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Microstructure and mechanical properties of Al-Fe-V-Si\\/SiCp composites
The characteristics of microstructures and mechanical properties of the multi-layer spray deposited SiCP\\/Al-6.5Fe-0.6V-1.3Si, SiCP\\/Al-8.5Fe-1.3V-1.7Si and SiCP\\/Al-10Fe-1.3V-2Si composite sheets obtained by rolling after extruding were investigated. The evolution of the grain and phases of these composites during processing were examined, and the influence of the microstructures on the mechanical properties was analyzed. The experimental results show that the ultimate tensile strengths
CHEN Zhen-hua; YAN Hong-ge; HAO Liang; CHEN Zhi-gang
Mössbauer spectroscopy study of the disordering process of Fe-rich FeAlSi alloys
NASA Astrophysics Data System (ADS)
In this work we study systematically the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe75Al25- x Si x , Fe70Al30- x Si x and Fe60Al40- x Si x alloys by means of Mössbauer spectroscopy and X-ray diffraction measurements. In order to obtain different stages of disorder the alloys were deformed by ball milling annealed (ordered) alloys during different number of hours. X-ray and Mössbauer data show that mechanical deformation induces the disordered A2 structure in these alloys. The results indicate that addition of Si to binary Fe-Al alloys makes the disordering more difficult. The study of the hyperfine fields indicates that depending on the Fe content the magnetic behaviour of these ternary alloys varies. For Fe75Al25- x Si x series, the alloys have different magnetic behaviours with deformation depending on the Si content. The magnetization of the alloys with high Si content decreases with deformation, as it happens to binary Fe75Si25 and the magnetization of the alloys with low Si content increases with deformation, as it happens to binary Fe75Al25. For Fe70Al30- x Si x series the mean hyperfine fields show that there are two different stages with the disordering, in a first stage the mean hyperfine fields decrease and in the second stage they increase. Finally, for Fe60Al40- x Si x alloys there is a magnetic transition, from a paramagnetic ordered state to a magneticdisordered state.
Legarra, E.; Apiñaniz, E.; Plazaola, F.
Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of ?-Al5FeSi in Hypoeutectic Al-Si Foundry Alloys
NASA Astrophysics Data System (ADS)
The present investigation was carried out on hypoeutectic Al-Si alloys containing two levels of Fe, 0.5 and 1.1 wt pct, and Sr in the range of 30 to 500 ppm. The addition of Sr in excess of 100 ppm significantly reduced the number of eutectic grains and also resulted in the formation of polygonal-shaped Al2Si2Sr intermetallics. Transmission electron microscopy studies revealed that the Al2Si2Sr phase surrounded the P-rich particles. This may suggest that the otherwise potent nuclei for the Al-Si eutectic, aluminum phosphide (AlP), become poisoned or deactivated by the formation of the Al2Si2Sr phase around the particles. At the high-Fe level (1.1 wt pct Fe), pre-eutectic formation of ?-Al5FeSi platelets further reduced the number of eutectic Al-Si nucleation events. It is proposed that both eutectic silicon and ?-Al5FeSi are preferentially nucleated on AlP particles. Nucleation of eutectic silicon, therefore, becomes more difficult when it is preceded by the formation of Al2Si2Sr or ?-Al5FeSi, because fewer nuclei are available to nucleate silicon. Addition of up to 60 ppm P to the alloys increased the formation temperature of the ?-Al5FeSi platelets but did not significantly alter the size, whereas the addition of Sr decreased the ?-Al5FeSi nucleation temperature by reducing the potency of the AlP particles.
Cho, Y. H.; Lee, H.-C.; Oh, K. H.; Dahle, A. K.
Precipitation of ?-Al5FeSi Phase Platelets in Al-Si Based Casting Alloys
NASA Astrophysics Data System (ADS)
The aim of the present work has been to investigate the factors affecting the precipitation of the ?-Al5FeSi iron intermetallic phase of directionally solidified A356- and 319-type alloys as a function of the iron content, a Sr addition of ~250 ppm, and superheating or cooling rates. The iron levels selected varied from 0.12 to 0.8 wt pct and cover the range of Fe levels in commercial casting alloys. The use of an end-chill mold provided different cooling rates along the height of the same casting, with dendritic arm spacing values that varied from ~15 to 85 ?m, corresponding to levels of 5, 10, 30, 50, and 100 mm above the chill end. The microstructure and phase identification were monitored using optical microscopy, scanning electron microscopy (SEM), thermal analysis, and electron probe microanalysis (EPMA) techniques. An image analyzer was used in conjunction with the optical microscope for quantification purposes. The results showed that, for the range of cooling rates covered in the present study, the highest cooling rate (at a 5-mm distance from the chill) is the more significant parameter in controlling the size and distribution of the ?-Al2FeSi intermetallic phase in the nonmodified 319 and 356 alloys. The addition of strontium leads to fragmentation of coeutectic or posteutectic ? platelets. This effect diminishes with an increase in the iron concentration, and further strontium addition leads to the precipitation of Al2Si2Sr phase particles, instead.
Liu, L.; Mohamed, A. M. A.; Samuel, A. M.; Samuel, F. H.; Doty, H. W.; Valtierra, S.
Microstructure and Mechanical Properties of Rapidly Solidified Hypereutectic Al–Si and Al–Si–Fe Alloys
The microstructure and mechanical properties of rapidly solidified Al–18 wt% Si and Al–18 wt% Si–5 wt% Fe alloys were investigated by a combination of optical microscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffraction, tensile testing, and wear testing. The centrifugally atomized binary alloy powder consisted of the a-Al (slightly supersaturated with Si) and Si phases and the ternary alloy
S. S. Cho; B. S. Chun; C. W. Won; H. K. Kim; B. S. Lee; K. H. Yim; S. H. Eom; H. Baek; B. J. Song; C. Suryanarayana
Production of exp 26 Al by Spallation of Fe, Si, Al Nuclei.
National Technical Information Service (NTIS)
Cross sections for exp 7 Be, exp 10 Be and exp 26 Al formation in Al, Si and Fe targets bombarded with 0.6 and 24GeV protons have been measured by using highly selective chemical separation and low-level background counters. Results for exp 26 Al at 0.6Ge...
P. Paillard
Impact of Al passivation and cosputter on the structural property of ?-FeSi2 for Al-doped ?-FeSi2/n-Si(100) based solar cells application.
The aluminum (Al) doped polycrystalline p-type ?-phase iron disilicide (p-?-FeSi2) is grown by thermal diffusion of Al from Al-passivated n-type Si(100) surface into FeSi2 during crystallization of amorphous FeSi2 to form a p-type ?-FeSi2/n-Si(100) heterostructure solar cell. The structural and photovoltaic properties of p-type ?-FeSi2/n-type c-Si structures is then investigated in detail by using X-ray diffraction, Raman spectroscopy, transmission electron microscopy analysis, and electrical characterization. The results are compared with Al-doped p-?-FeSi2 prepared by using cosputtering of Al and FeSi2 layers on Al-passivated n-Si(100) substrates. A significant improvement in the maximum open-circuit voltage (Voc) from 120 to 320 mV is achieved upon the introduction of Al doping through cosputtering of Al and amorphous FeSi2 layer. The improvement in Voc is attributed to better structural quality of Al-doped FeSi2 film through Al doping and to the formation of high quality crystalline interface between Al-doped ?-FeSi2 and n-type c-Si. The effects of Al-out diffusion on the performance of heterostructure solar cells have been investigated and discussed in detail. PMID:23734756
Dalapati, Goutam Kumar; Kumar, Avishek; Tan, Cheng Cheh; Liew, Siao Li; Sonar, Prashant; Seng, Hwee Leng; Hui, Hui Kim; Tripathy, Sudhiranjan; Chi, Dongzhi
Properties of Fe-Al-Si high-damping steel
NASA Astrophysics Data System (ADS)
Several high-damping materials have been developed in recent years to decrease vibration and noise levels of machines and structures. The most important damping steels have been Fe- 12Cr-based alloys. These steels exhibit high damping capacity combined with rather good mechanical and corrosion properties. A new vibration damping Fe-2.5Al-0.5Si steel has been developed by NKK-Corporation in Japan, and it is produced under a trade name of NKK- SERENA. This steel is a potential multi-purpose damping steel, because it is more economical than the previous steels. Damping capacity of NKK-SERENA is very high in wide temperature and frequency ranges, and its mechanical properties are similar to those of common structural steels. In this study, mechanical, welding and corrosion properties, and the results of the microstructural characterization are presented.
Aaltio, Ilkka; Ullakko, Kari; Hanninen, Hannu
27Al and 29Si NMR spectroscopy of MgSiO3 perovskite: mechanisms of Al and Fe incorporation
NASA Astrophysics Data System (ADS)
The boundary between the Earth's upper and lower mantle is generally attributed to the decomposition of (Mg,Fe)2SiO4 ringwoodite into ferropericlase and perovskite-structured (Mg,Fe)SiO3, hereafter perovskite. Concomitant with this phase change is the more gradual disappearance of a separate Al-bearing phase (majoritic garnet) and dissolution of Al into perovskite. The mechanism of Al incorporation is strongly affected by the presence of Fe due to the co-substitution of Al3+ and Fe3+ for Si4+ and Mg2+, respectively. However, questions about specific substitution mechanisms, site occupancy, and long- and short-range ordering of Fe and Al are still not fully understood. These are questions that NMR is particularly suited to address. We are applying Mossbauer, and 27Al and 29Si MAS-NMR spectroscopy to a series of Al- and Fe-bearing MgSiO3 perovskites of nominal composition Mg1-xFexSi1-xAlxO3 (x = 0.01, 0.025, 0.05). These were synthesized in a multi-anvil cell press at 26 GPa and 1900°C from either glassy starting material or Fe-bearing, aluminous pyroxene synthesized at 8-10 GPa and 1200°C. 29Si spectra show the presence of only a narrow perovskite peak at -191.7 ppm and a broad peak at -81 ppm from an amorphous phase likely formed when crushing the multi-anvil run products. 27Al spectra contain one narrow peak at 6.4 ppm and one broad peak at -14.6 ppm, matching those seen in previous NMR studies of aluminous perovskite and corresponding to Al3+ substituting for Si4+ and Mg2+ respectively. The ratio of observable Al3+ in Si4+ vs. that in Mg2+ sites ranges from 5.5 to 6.3 when the signal to noise of the -14.6 ppm peak is sufficient for quantitation. NMR spectra of materials containing paramagnetic species (i.e. Fe2+ or Fe3+) are often complicated and difficult to interpret due to line broadening, signal loss, "contact" shifts, etc. However, with an understanding of paramagnetic interactions in NMR spectroscopy, valuable information can be gained about some Fe-bearing geological materials. For the pyroxene starting materials used here, NMR signal loss increases linearly with increasing Fe content, an expected result given the likely uncoupled substitution of Fe2+ and Al3+ in these materials. However, 27Al signal loss for the perovskite samples is non-linear with a nearly constant value going from Fe/(Fe + Mg) = 0.01 to 0.025 indicating strong ordering of Fe3+ and Al3+ onto adjacent crystallographic sites. Complete signal loss at Fe/(Fe + Mg) = 0.05 suggests the upper limit of Fe2+ and Fe3+ concentration at which useful NMR data can be obtained for this system. The results of this study are a start to a better understanding of the mechanism of solution of Fe and Al in perovskite and continued work on this problem could provide valuable information on this important lower mantle phase. In addition, this study has potential to give us more general insights into paramagnetic interactions in NMR spectroscopy of geological materials.
Palke, A.; Stebbins, J. F.; Frost, D. J.; McCammon, C. A.
Microwave power absorption of magnetic composites filled with surface coated Fe-Al-Si flakes
NASA Astrophysics Data System (ADS)
The Al2O3 coated Fe-Al-Si flakes were employed as a magnetic filler in 150 ?m-thick dielectric matrix. The saturation magnetizations of the coated Fe-Al-Si flakes were decreased down to 98 emu/g with the increment of the coating thickness (170 nm, 250 nm, 350 nm) in comparison with that of uncoated Fe-Al-Si flakes (130 emu/g). The power absorptions for Al2O3 coated Fe-Al-Si flakes composites were decreased from 62.7% to 57.4% (at 5 GHz) with the increment of coating thickness in comparison with that of uncoated Fe-Al-Si flakes composite (80% at 5 GHz). The thermal conductivities of Al2O3 coated composites were increased up to 0.249 W/m K in comparison with that of uncoated composite of 0.096 W/m K.
Lee, Joonsik; Ho Cho, Sang; Yoon, Sanghoon; Hyeon Kim, Ki
Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of ? Al 5 FeSi in Hypoeutectic Al-Si Foundry Alloys
The present investigation was carried out on hypoeutectic Al-Si alloys containing two levels of Fe, 0.5 and 1.1 wt pct, and\\u000a Sr in the range of 30 to 500 ppm. The addition of Sr in excess of 100 ppm significantly reduced the number of eutectic grains\\u000a and also resulted in the formation of polygonal-shaped Al2Si2Sr intermetallics. Transmission electron microscopy studies revealed that the
Y. H. Cho; H.-C. Lee; K. H. Oh; A. K. Dahle
(Fe,Si,Al)-based nanocrystalline soft magnetic alloys for cryogenic applications
NASA Astrophysics Data System (ADS)
In this work Al and Si are substituted for Fe in a (Fe,Si,Al)-Nb-B-Cu alloy with the goal of improving its magnetic properties at 77 K. The x-ray diffraction patterns for a series of five alloys annealed at 823 K shows a Fe3(Si,Al) ordered phase with some residual amorphous phase. The lowest coercivity at room temperature was observed for the alloy with composition Fe68Si15.5Al3.5Nb3B9Cu1. At cryogenic temperatures, the saturation magnetization of 99.3 A m2/kg, coercivity of 0.45 A/m, and resistivity of 122 ?? cm for the Fe63Si17.5Al6Nb3B9Cu1 alloy, compare favorably to commercial alloys at 77 K.
Daniil, Maria; Osofsky, Michael S.; Gubser, Donald U.; Willard, Matthew A.
The Morphology and Chemistry Evolution of Inclusions in Fe-Si-Al-O Melts
NASA Astrophysics Data System (ADS)
This study aims to elucidate the process of inclusion precipitation in Fe-Si and Fe-Si-Al melts. Deoxidation experiments were carried out in a vacuum induction furnace (VIF) at 1873 K (1600 °C). In the Si-deoxidation experiments, spherical SiO2 of 1~2 ?m diameter was dominant. When 3 wt pct Si and 300 ppm Al were added, such that Al2O3 and mullite were thermodynamically stable, the resulting inclusions depended on the addition sequence. When aluminum was added before silicon, spherical aluminum oxides were dominant after the Al addition, but after the Si addition, the number and size of alumina decreased and Al-Si oxides and mullite appeared with increasing time. When silicon was added before aluminum, spherical SiO2 was dominant after the Si addition, but after the Al addition, spherical and polygonal alumina inclusions were dominant. When Al/Si was added simultaneously, polygonal alumina inclusions were dominant initially, but with time, Al-Si oxide and mullite inclusions increased in numbers. If the Al amount in the Al/Si addition was increased to 600 ppm, only alumina was found. This study shows how, under similar thermodynamic conditions, the transient evolution of inclusions in iron melts in the Si-Al-O system differ depending on the alloy addition sequence.
Kwon, Youjong; Choi, Juhan; Sridhar, Seetharaman
Microstructure and mechanical properties of Fe–Si–Ti–(Cu, Al) heterostructured ultrafine composites
The influence of partial substitution of Fe by Cu or Al in Fe75?xSi15Ti10(Cu, Al)x (x=0 and 4) ultrafine composites on the microstructure and mechanical properties has been investigated. The Fe71Si15Ti10Cu4 ultrafine composite exhibits a favorable microstructural evolution and improved mechanical properties, i.e., large plastic strain of ?5% and pronounced work hardening characteristics. The mechanical properties of the ultrafine eutectic composite
J. M. Park; D. H. Kim; N. Mattern; K. B. Kim; E. Fleury; J. Eckert
Effects of Mn on the crystal structure of ?-Al(Mn,Fe)Si particles in A356 alloys
NASA Astrophysics Data System (ADS)
In a commercial Al-7.0Si-0.38Mg cast alloy (A356) with 0.20 wt% Fe, added Mn modifies acicular ?-Al 5FeSi particles to less acicular ?-Al(Mn,Fe)Si in both crystallization and precipitation conditions. The crystal structure of ?-Al(Mn,Fe)Si changes from body-centered cubic (bcc)/ simple cubic (sc) to Pm3 structures in response to an increase in the bulk Mn content of the alloy. The ?-Al(Mn,Fe)Si particles (50-200 nm) precipitate during solution treatment and their precipitation temperature is about 485 °C in the as-cast condition.
Kim, Hyun You; Park, Tea Young; Han, Sang Won; Lee, Hyuck Mo
Rapidly solidified Al-Fe-Mo-Si alloys for high temperatures applications
Iron solubility in aluminium can be extended through the rapid solidification route, allowing the precipitation of a high volume fraction of intermetallic phases. In the ternary Al-Fe-Si system, the observed metastable hardening phase Al13Fe3Si is sensitive to ripening. Thermal stability can be improved by modification of the surface energy of the precipitate, i.e. by lattice parameter variation, through addition of
Solidification behaviour, microstructure and mechanical properties of high Fe-containing Al–Si–V alloys
The paper deals with effect of Fe on the solidification behaviour and mechanical properties of unmodified and modified Al–V–Si alloys. Effect of thermo-mechanical processing on the mechanical properties of these alloys was also reported. The solidification proceeds through several invariant reactions, the first one corresponds to formation of Al3(Fe,V,Si)-type phase. Modification with Ni–Mg master alloy changes the morphology, size and
K. L. Sahoo; B. N. Pathak
Evaluation of bulk ?-FeSi2 crystal as a solar cell semiconductor through the photo-response measurements of Al/n-?-FeSi2 Schottky diodes
NASA Astrophysics Data System (ADS)
?-FeSi2 has many attracting properties as a semiconductor not consisting of toxic chemical elements and is an ideal semiconductor as a thin film solar cell owing to its extremely high optical absorption coefficient. To evaluate ?-FeSi2 as a solar cell, photo-response measurement is critically important and useful. Since ?-FeSi2 thin films are normally deposited on Si substrates, intrinsic photo-response of ?-FeSi2 is usually difficult to be collected due to the strong contribution from Si substrates. We here present the photo-response from bulk ?-FeSi2 crystals, expecting that we can eliminate the contributions coming from the Si substrates and the crystallographic defects existing at the ?-FeSi2/Si interfaces when we use ?-FeSi2 thin films. We prepared bulk specimens by chemical vapor transport method (CVT) in which needle-like and plate-like ?-FeSi2 crystals were obtained. We chose the former specimens for the formation of Al/n-?-FeSi2 Schottky contacts to measure their photo-responses. These contacts were found to form Schottky diodes even though there are large series resistances and leakage currents. Under laser light illumination of 1.31 ?m through optical fiber, the positive voltage was observed between the Al contact and the In solder glued to the back-surface of ?-FeSi2 bulk specimen. Two-dimensional distribution of photo-responses were measured by scanning the above optical fiber with the spot size of 50 ?m. The highest photo-response was obtained in the vicinity of Al wire, and was 7.7 mA/W for the as-grown sample, and 31 mA/W for the annealing one, respectively. These observations state that ?-FeSi2 holds appropriate optical features to be used as a solar cell.
Fukuzawa, Yasuhiro; Ootsuka, Teruhisa; Nakayama, Yasuhiko; Makita, Yunosuke
Hot Tear Susceptibility of Al-Mg-Si-Fe Alloys with Varying Iron Contents
NASA Astrophysics Data System (ADS)
Hot tear susceptibility in cast Al-0.52Si-0.34Mg- xFe 6060 aluminum alloys was investigated using a hot tearing test apparatus to simulate hot tearing in DC casting. The test apparatus has two cast bars, one that is used to measure the load response and one which is fixed at both ends to restrain thermal contraction so that hot tearing can be observed and rated where it occurred. The iron (Fe) content, ranging from 0.02 to 0.5 wt pct, was seen to have a major influence on the load response during solidification and the tear rating of these alloys. The findings are discussed in terms of Rappaz-Drezet-Gremaud (RDG) model sensitivity analysis and related to the effect of Fe content on the morphology and prevalence of the ?-Al5FeSi and ?-AlFeSi intermetallic phases and their influence on the coherency and coalescence of the microstructure.
Sweet, Lisa; Easton, Mark A.; Taylor, John A.; Grandfield, John F.; Davidson, Cameron J.; Lu, Liming; Couper, Malcolm J.; StJohn, David H.
Topics in precipitation and ordering reactions and their related phenomena. [Al-Si; Al-Ge; Fe-Cu; Pt-C; Fe-N
The application of High Voltage Electron Microscopy to the study of phase transformations is illustrated with a number of examples of precipitation reactions (Al-Si; Al-Ge; Fe-Cu; Pt-C; Fe-N). The importance of lattice defects is emphasized and it is shown how strain accommodation is accomplished for various types of transformations.
Westmacott, K.H.; Dahmen, U.
Heterogeneous Nucleation of ?-Al Grain on Primary ?-AlFeMnSi Intermetallic Investigated Using 3D SEM Ultramicrotomy and HRTEM
NASA Astrophysics Data System (ADS)
Microstructural examination of the Al-5.3Mg-2.4Si-0.6Mn-1.0Fe alloy in the die-cast condition revealed that a significant number of the primary ?-AlFeMnSi intermetallic particles were found inside both the coarse ?-Al dendrite fragments formed in the shot sleeve and the fine ?-Al grains formed in the die cavity. The heterogeneous nucleation of ?-Al phase on primary ?-AlFeMnSi intermetallic particle was further investigated experimentally. 3-Dimension (3D) scanning electron microscopy ultramicrotomy revealed that the probability of finding at least one primary ?-AlFeMnSi intermetallic particle inside each ?-Al grain was almost 90 pct. The detailed microstructural analysis identified the primary ?-AlFeMnSi intermetallic particle as the ?-Al12(Fe,Mn)3Si composition with a body-centered cubic structure and a lattice parameter of a = 1.265 nm. It was found that the primary ?-Al12(Fe,Mn)3Si intermetallic particle had a faceted morphology with {110} planes exposed as its natural surfaces. High resolution transmission electron microscopy further confirmed that the crystallographic orientation relationship between ?-Al12(Fe,Mn)3Si intermetallic particle and ?-Al phase was: [111]?-AlFeMnSi//[110]Al and (1 overline{1} 0)?-AlFeMnSi 6 deg from (1 overline{1} 1)?-Al, and the corresponding interface between two phases could be confirmed as a semi-coherent interface with a lattice misfit of 2.67 pct at 933 K (660 °C), which was considerably smaller than the theoretical limit (5.7 pct) for epitaxial nucleation. Finally, based on these experimental evidences and the epitaxial nucleation model, we concluded that the primary ?-Al12(Fe,Mn)3Si intermetallic particles were both potent and effective nucleating substrates for the ?-Al phase.
Yang, Wenchao; Ji, Shouxun; Zhou, Xiaorong; Stone, Ian; Scamans, Geoff; Thompson, George E.; Fan, Zhongyun
Skin solidification during high pressure die casting of Al–11Si–2Cu–1Fe alloy
Surface regions of Al–11Si–2Cu–1Fe alloy castings produced by high pressure die casting (HPDC) were examined and three microstructural features were observed. In locations of direct melt impingement, there was not an ?-Al rich layer. In most surface locations, a porosity-free ?-Al rich layer was observed. However, in surface locations of low impact of melt, a porosity-free layer being a mixture
Z. W. Chen
Discussion of "Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of ? Al 5 FeSi in Hypoeutectic Al-Si Foundry Alloys"
The nucleation of Si during the solidification of Al-Si hypoeutectic alloys appears to result from a hierarchy of nucleating\\u000a substrates operating at progressively lower temperatures: (1) AlP, whose generally particulate morphology can initiate the\\u000a formation of compact Si particles as seen in hypereutectic alloys; (2) oxide bifilms alone, whose planar form creates platelike\\u000a Si morphologies; and (3) a currently unknown
John Campbell
FeAl and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying
FeAl and Mo-Si-B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe-24Al (wt.%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 m/s to 700 m/s. Mo-13.4Si-2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo-Si-B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity, again due to an increased peening effect. For Mo-Si-B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and {alpha}-Mo. The T1 phase was retained after spraying at 350 m/s.
Totemeier, T.C.; Wright, R.N.; Swank, W.D.
Spin pumping at the Co2FeAl0.5Si0.5/Pt interface
NASA Astrophysics Data System (ADS)
Spin pumping at the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces has been studied by ferromagnetic resonance technology (FMR). The spin mixing conductance of the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces was determined to be 3.7×1019 m-2 and 2.1×1019 m-2 by comparing the Gilbert damping in a Co2FeAl0.5Si0.5 single film, Co2FeAl0.5Si0.5/Pt bilayer film and a Pt/Co2FeAl0.5Si0.5/Pt trilayer film. Spin pumping is more efficient in the Co2FeAl0.5Si0.5/Pt bilayer film than in permalloy/Pt bilayer film.
Wu, Yong; Zhao, Yue-Lei; Xiong, Qiang; Xu, Xiao-Guang; Sun, Young; Zhang, Shi-Qing; Jiang, Yong
Compaction behavior of rapidly solidified Al-Si-Fe-Cr alloy powders
Recently, the powder forging process of rapidly solidified Al alloys was investigated in order to develop an inexpensive alternative process to produce high strength parts with complex shapes. It has been shown that the mechanical properties of powder-forged parts are as good as those produced by extrusion. In this study, the consolidation behaviors of rapidly solidified Al-Si-Fe-Cr alloy powders with
Hyoung Seop Kin; Sun Jae Kim; Hong Ro Lee; Chang Whan Won; seong Seock Cho; Byung Sun Chun
Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa
NASA Astrophysics Data System (ADS)
The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (?1) and imaginary part (?2) of the dielectric constant in the range of wavelengths ? = 0.3-13 ?m using the ellipsometric method. An anomalous behavior of the optical conductivity ?(?) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.
Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.
The structure-property relationships of powder processed Fe-Al-Si alloys
Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D{sub 84} < 32 {micro}m). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 {micro}m. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 {micro}m to 104 {micro}m. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase {alpha} + DO{sub 3} structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.
Prichard, P.D.
Effects of intensive forced melt convection on the mechanical properties of Fe containing Al–Si based alloys
The pickup of impurity Fe is an inherent engineering problem for the recycling of aluminium alloys, due to the detrimental effects of Fe containing intermetallic compounds on the mechanical properties. This work aims to understand the effects of intensive forced melt convection and alloying on the mechanical properties of Fe containing Al–Si based cast alloys. Varied Fe levels were introduced
X. Fang; G. Shao; Y. Q. Liu; Z. Fan
Photovoltaic characteristics of p-?-FeSi2(Al)/n-Si(100) heterojunction solar cells and the effects of interfacial engineering
NASA Astrophysics Data System (ADS)
Heterojunction solar cells with Al-alloyed polycrystalline p-type ?-phase iron disilicide [p-?-FeSi2(Al)] on n-Si(100) were investigated. The p-?-FeSi2(Al) was grown by sputter deposition and rapid-thermal annealing. Photocurrent of ~1.8 mA/cm2 and open-circuit voltage of ~63 mV were obtained for p-?-FeSi2(Al)/n-Si(100)/Ti/Al control cells with indium-tin-oxide (ITO) top electrode. Open-circuit voltage increased considerably once thin Al layer was deposited before amorphous-FeSi2(Al) deposition. Furthermore, device performances were found to improve significantly (~5.3 mA/cm2 and ~450 mV) by introducing germanium-nitride electron-blocking layer between ITO and p-?-FeSi2(Al). The improvement is attributed to the formation of epitaxial Al-containing p+-Si at p-?-FeSi2(Al)/n-Si(100) interface and suppressed back-diffusion of photogenerated electrons into ITO.
Dalapati, G. K.; Liew, S. L.; Wong, A. S. W.; Chai, Y.; Chiam, S. Y.; Chi, D. Z.
Alloy Composition and Dendrite Arm Spacing in Al-Si-Cu-Mg-Fe Alloys
NASA Astrophysics Data System (ADS)
Six Al-Si-Cu-Mg-(Fe/Mn) alloys with two levels of each of Cu, Si, and Fe/Mn were cast in the form of quasi-directionally solidified plates. The secondary dendrite arm spacing (SDAS) was measured as a function of the distance from the chill end for each composition and related to the local cooling rate as determined by thermocouples embedded in one of the cast plates. For a given cooling rate, Si has a strong, consistently refining effect on the SDAS per unit of solute content. Cu showed its strongest refining effect at low-Si and high-Fe contents. It is argued that the scale of the SDAS is determined by a combination of five main factors: constitutional undercooling; the fraction of Al-Si eutectic; and the amount, morphology, and distribution of the various intermetallic phases. The first two factors affect the early stages of the dendrite structure and SDAS formation, whereas the ones involving intermetallics affect the dendrite-coarsening mechanisms in the post-eutectic stage. The latter ones are more sensitive to cooling rate than the ones involving solute in solution. The scales of both, SDAS and intermetallics, can be predetermined to a measurable extent through the solute content to best suit particular casting conditions.
Sivarupan, Tharmalingam; Caceres, Carlos H.; Taylor, John A.
Kinetics of Reduction of SiO2 in SiO2-Al2O3-CaO Slags by Al in Fe-Al(-Si) Melts
NASA Astrophysics Data System (ADS)
Kinetic models considering mass transport in, (i) metal phase only and (ii) both metal and slag phases (mixed control or two-phase mass transfer) were developed for the reduction of SiO2 in a SiO2-Al2O3-CaO slag by Al in an Al-Fe melt. The models were validated with experiments of the reaction with Fe-Al melt and SiO2-Al2O3-CaO-MgOsat slags at 1873 K (1600 °C). The models predict that the rate of reaction is slower in the mixed control model because of the added resistance of slag phase mass transport. The mixed control becomes applicable when the slag contains low amounts of SiO2. In this case, when the initial Al content in the metal increases, the normalized rate of reaction decreases. The increased Al content in the metal retards the reaction due to the limited SiO2 provided to the reaction interface in the mixed control model. Sensitivity analyses were done using the models for the ratios of mass transfer coefficients of Si to Al, and Al2O3 to Si, along with slag density, which did not impose a significant effect.
Park, Jiwon; Sridhar, Seetharaman; Fruehan, Richard J.
The structure-property relationships of powder processed Fe-Al-Si alloys
Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape PN processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive
Paul Dehnhardt Prichard
The Structure-property Relationships Of Powder Processed Fe-al-si Alloys
Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P\\/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive
P D Prichard
Effect of casting and homogenizing treatment conditions on the formation of Al–Fe–Si intermetallic compounds in 6063 Al–Mg–Si alloys
The effect of casting and homogenizing treatment conditions on the formation of several Al–Fe–Si intermetallic compounds in 6063 aluminum alloy was investigated using X-ray diffraction and transmission electron microscopy (TEM). The four kinds of alloys containing 0.1 to 0.5 mass% Fe were melted and then cooled at three different cooling rates ranging from 0.06 to 50 K\\/s, following the homogenization
H. Tanihata; T. Sugawara; K. Matsuda; S. Ikeno
X-rays structural analysis and thermal stability studies of the ternary compound {alpha}-AlFeSi
From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound {alpha}-AlFeSi (also designated as {alpha}{sub H} or {tau}{sub 5}) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound {alpha}-AlFeSi were meticulously studied. The crystal structure of {alpha}-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6{sub 3}/mmc with unit cell parameters (293 K) a=12.345(2) A and c=26.210(3) A (V=3459 A{sup 3}). The average chemical formula obtained from refinement is Al{sub 7.1}Fe{sub 2}Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into {theta}-Fe{sub 4}Al{sub 13}(Si), {gamma}-Al{sub 3}FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772{+-}12 {sup o}C. -- Graphical abstract: Partial representation of the crystal structure of the {alpha}-Al{sub 7.1}Fe{sub 2}Si compound. Display Omitted Highlights: The main findings of our work are: {yields} a detailed X-rays crystal structure determination of the ternary compound {alpha}-AlFeSi. {yields} The precision of the silicon atoms positions in the crystal structure. {yields} A precised determination of the decomposition temperature of this compound.
Roger, J., E-mail: email@example.com [Laboratoire des Multimateriaux et Interfaces, UMR CNRS no. 5615, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex (France); Bosselet, F.; Viala, J.C. [Laboratoire des Multimateriaux et Interfaces, UMR CNRS no. 5615, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex (France)
X-rays structural analysis and thermal stability studies of the ternary compound ?-AlFeSi
NASA Astrophysics Data System (ADS)
From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound ?-AlFeSi (also designated as ?H or ?5) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound ?-AlFeSi were meticulously studied. The crystal structure of ?-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6 3/mmc with unit cell parameters (293 K) a=12.345(2) Å and c=26.210(3) Å ( V=3459 Å 3). The average chemical formula obtained from refinement is Al 7.1Fe 2Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into ?-Fe 4Al 13(Si), ?-Al 3FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772±12 °C.
Roger, J.; Bosselet, F.; Viala, J. C.
Glass formation by first-order transition in Al-Fe-Si system
NASA Astrophysics Data System (ADS)
There are two quite different views of metallic glasses. One, that a glass forms when an undercooled melt becomes kinetically frozen. This mechanism is quite universal and in principle occurs for all melts if they can be cooled rapidly enough. Usually such glasses tolerate wide compositional variations and occur at deep eutectics. The other view looks for efficient high-density low-energy packing of atoms in an aperiodic isotropic structure. These glasses, which we dubbed q-glasses, are expected to be less tolerant of composition variations and do not require deep eutectic. In our earlier publications we presented evidence of the existence of a q-glass in Al-Fe-Si. The glass was found to form from the melt as a primary phase by a nucleation and growth reaction before there is any crystallization was found to occur in. Here we present detailed study of formation of the Al-Fe-Si q-glass in a wide range of compositions. It was found that the glass behaves as a stoichiometric compound, with a concentration near 15 a/o Fe, 20 a/o Si. For other compositions formation of complex intermetallic compounds and an icosahedral phase were observed
Bendersky, Leonid A.
The Viscous Behavior of FeO t Al 2 O 3 SiO 2 Copper Smelting Slags
Understanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining\\u000a the discrete separation between the matte and the slag. The viscosity of the FeOt-SiO2-Al2O3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al2O3 concentration decreased with increasing Fe\\/SiO2 ratio because of the
Hyun-Shik Park; Su Sang Park; Il Sohn
Effects of Melt Thermal-Rate Treatment on Fe-Containing Phases in Hypereutectic Al-Si Alloy
NASA Astrophysics Data System (ADS)
In this paper, effects of melt thermal-rate treatment (MTRT) on Fe-containing phases in hypereutectic Al-Si alloy were investigated. Results show that MTRT can refine microstructures and improve castability, mechanical properties, wear characteristics, and corrosion resistance of Fe-containing Al-Si alloy. When Al-15Si-2.7Fe alloy is treated with MTRT by 1203 K (930 °C) melt: coarse primary Si and plate-like Fe-containing phase both can be refined to small blocky morphology, and the long needle-like Fe-containing phase disappears almost entirely; ultimate tensile strength and elongation are 195 MPa and 1.8 pct, and increase by 12.7 and 50 pct, respectively; and the wear loss and coefficient of friction decrease 7 to 17 and 24 to 30 pct, respectively, compared with that obtained with conventional casting technique. Corrosion resistance of the alloy treated with MTRT by 1203 K (930 °C) melt is the best, that is it has the lowest i corr value and the highest E corr value. Besides, effects of MTRT on Al-15Si-xFe (x = 0.2, 0.7, 1.7, 3.7, 4.7) alloys were also studied, MTRT can only refine microstructure and improve mechanical properties of Al-15Si alloy with 0.7 to 3.7 pct Fe content greatly in the present work.
Wang, Qinglei; Geng, Haoran; Zhang, Shuo; Jiang, Huawei; Zuo, Min
Power performance of LiAlSi/(FeNi)S cells
NASA Astrophysics Data System (ADS)
Half-cell and model-cell experiments have been conducted to investigate the electrochemical performance of (Fe-Ni)S2 electrodes and Li-Al-Si/(Fe-Ni)S2 cells. The electrodes, fabricated with 0.5- to 2-Ah theoretical capacity, have been investigated in both LiCl-LiBr-KBr and LiF-LiCL-LiBr electrolyte in the temperature ranges of 320 to 500 C and 450 to 500 C, respectively. Nickel-sulfide additive was found to improve the kinetics of the FeS2 electrode. Power performance and charge acceptance of the cell improves to a great extent when Li2S is used in excess of the stoichiometric amount required by the metal sulfide formation. The presence of lithium sulfide at the end of charge provides a unique overcharge protection mechanism.
Redey, L.
Surface modification of 5083 Al alloy by electrical discharge alloying processing with a 75 mass% Si-Fe alloy electrode
NASA Astrophysics Data System (ADS)
This study experimentally investigates the surface modification of 5083 Al alloy by the electrical discharge alloying (EDA) process with a Si-Fe alloy as an electrode. Samples were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-hardness and corrosion resistance tests. The micro-hardness of EDA alloyed layer was evidently higher than that of the base metal (5083 Al alloy). The TEM results show that the matrix of the alloyed layer has an amorphous-like structure; the matrix contains fine needle-like Si particles, block-like Si particles and nano-size Al4.5FeSi and Al13Fe4 particles. The TEM results support experimental results for the high hardness of the alloyed layer. Moreover, the EDA alloyed layer with composite microstructures has good corrosion resistance in NaCl aqueous solution.
Stambekova, Kuralay; Lin, Hung-Mao; Uan, Jun-Yen
Synthesis and equation of state of perovskites in the Mg3Al2Si3O12- Fe3Al2Si3O12 system
NASA Astrophysics Data System (ADS)
Fe and Al are two of the most abundant minor elements in the lower mantle and may have significant effects on the stability and elastic properties of the region's dominant phase, MgSiO3 perovskite. In order to predict the chemical and physical behavior of lower mantle chemical heterogeneities enriched in Fe and Al, we investigated perovskites synthesized from pyrope-almandine garnet compositions at high pressures. Previous studies of this system above 30 GPa are limited, and no in situ studies were reported before in this pressure range (Ahmed-Zaid and Madon, 1995; Kesson et al., 1995;; Miyajima et al., 1999; Tateno et al., 2005). Five compositions along the Mg3Al2Si3O12 (pyrope)- Fe3Al2Si3O12 (almandine) join were examined: three natural garnets (Alm38, Alm54, and Alm73) and two synthetic garnet glasses (Alm90 and Alm100). X-ray diffraction experiments were performed using the laser-heated diamond anvil cell at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Garnet powders were mixed with 10-15 wt % Au (with Alm54, Alm73, Alm90, and Alm100) or Pt (with Alm38) as pressure calibrant and loaded between foils of NaCl as thermal insulator, pressure medium, and secondary pressure standard. All compositions were initially cold compressed to 74-77 GPa and then laser heated to 1820-2480K. Samples were decompressed gradually to 41-50 GPa with laser annealing at 5-10 GPa intervals. For Alm90 and Alm100, synthesis experiments were also carried out near 41 GPa and then the samples were compressed up to 76 GPa with laser annealing at 10 GPa intervals. Over the pressure range studied, all compositions formed orthorhombic GdFeO3- type perovskites, with trace CaCl2-type SiO2. The unit cell volume of the perovskite structure increases with iron content, with that of the almandine end-member composition 3% larger than that of pyrope-composition perovskite and 4% larger than the corresponding MgSiO3 perovskite. As with MgSiO3 perovskite, the a lattice parameter is the most compressible. The degree of distortion from the cubic structure increases with pressure; however, the addition of a large amount of Fe to the structure appears to retard this effect.
Dorfman, S. M.; Mao, Z.; Shieh, S. R.; Meng, Y.; Prakapenka, V. B.; Duffy, T. S.
Spin transitions in (Mg,Fe)(Si,Al)O3 perovskite and the electrical conductivity of the lower mantle
NASA Astrophysics Data System (ADS)
Iron has the ability to adopt different spin states in the dominant lower mantle phase, (Mg,Fe)(Si,Al)O3 perovskite, where the spin states of iron atoms can significantly influence mantle properties and dynamics. Most studies have observed a transition involving Fe2+ that starts above approximately 30 GPa, although there is disagreement as to whether it involves a high-spin (HS) to intermediate-spin (IS) transition or simply a structural modification of the local atomic environment. Previous studies have also suggested that Fe3+ (which constitutes at least half of the iron in lower mantle silicate perovskite) undergoes a HS to low-spin (LS) transition when Fe3+ occupies the octahedral site in the structure. Previous electrical conductivity measurements of (Mg,Fe)(Si,Al)O3 perovskite have shown that conductivity drops significantly above 50 GPa, which has been attributed to the HS-LS transition of Fe3+. In view of many existing controversies concerning the spin state of iron in the lower mantle and suggestions that spin transitions may cause seismic velocity anomalies, we made a new investigation of carefully characterised samples of (Mg,Fe)(Si,Al)O3 perovskite with a range of Fe3+/?Fe values. We applied a new synchrotron-based method of Mössbauer spectroscopy (which enables individual spin and valence states to be identified) combined with electrical conductivity measurements on one of the samples, in order to construct a clear picture of iron spin transitions in (Mg,Fe)(Si,Al)O3 perovskite at lower mantle pressures and temperatures. We studied four different samples using a laser heated diamond anvil cell (DAC) with a Synchrotron Mössbauer Source (SMS) at the Nuclear Resonance beamline ID18 at the European Synchrotron Radiation Facility. Our data demonstrate unambiguously that Fe3+ remains in the HS state at conditions throughout the lower mantle, and show evidence for a HS-IS transition in Fe2+. High-pressure high-temperature electrical conductivity measurements of (Mg,Fe)(Si,Al)O3 perovskite with high Fe3+/?Fe show a continuous increase in conductivity with pressure, strongly advocating that the conductivity drop in previous experiments with low Fe3+/?Fe is due to a HS-IS transition of Fe2+. Our results provide improved constraints for forward modelling of electromagnetic data as well as for joint inversion of electromagnetic and seismic data, providing a new probe of heterogeneity in the lower mantle.
McCammon, C. A.; Potapkin, V.; Glazyrin, K.; Kantor, A.; Kupenko, I.; Prescher, C.; Sinmyo, R.; Pesce, G.; Smirnov, G. V.; Chumakov, A. I.; Rüffer, R.; Dubrovinsky, L. S.
The Viscous Behavior of FeOt-Al2O3-SiO2 Copper Smelting Slags
NASA Astrophysics Data System (ADS)
Understanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining the discrete separation between the matte and the slag. The viscosity of the FeOt-SiO2-Al2O3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al2O3 concentration decreased with increasing Fe/SiO2 ratio because of the depolymerization of the molten slag by the network-modifying free oxygen ions (O2-) supplied by FeO. The Fourier transform infrared (FTIR) analyses of the slag samples with increasing Fe/SiO2 ratio revealed that the amount of large silicate sheets decreased, whereas the amount of simpler silicate structures increased. Al2O3 additions to the ternary FeOt-SiO2-Al2O3 slag system at a fixed Fe/SiO2 ratio showed a characteristic V-shaped pattern, where initial additions decreased the viscosity, reached a minimum, and increased subsequently with higher Al2O3 content. The effect of Al2O3 was considered to be related to the amphoteric behavior of Al2O3, where Al2O3 initially behaves as a basic oxide and changes to an acidic oxide with variation in slag composition. Furthermore, Al2O3 additions also resulted in the high temperature phase change between fayalite/hercynite and the modification of the liquidus temperature with Al2O3 additions affecting the viscosity of the copper smelting slag.
Park, Hyun-Shik; Park, Su Sang; Sohn, Il
Morphological features of the crystalline or quasicrystalline silicides observed in the quaternary Al-Fe-Mo-Si alloys
Rapidly solidified Al-Fe-Mo-Si powders were produced by centrifugal atomization and then consolidated by hot extrusion. Five compositions were chosen in order to obtain a theoretical constant volume fraction of (silicide + Al12Mo) of 20%, with different relative fractions of [silicide]\\/[a-matrix] and different ratios of [Fe]\\/[Mo] within the silicide. This paper presents the microstructures observed in both as-atomized and consolidated states.
M. C. S. De Macêdo; G. Michot
Ab initio study of Fe2MnZ (Al, Si, Ge) Heusler alloy using GGA approximation
NASA Astrophysics Data System (ADS)
Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe2MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater-Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 ?B. Spin polarization calculations evidence 100% spin polarization for Fe2MnSi. Fe2MnAl and Fe2MnGe show metallic behavior with 93%, 98% spin polarization.
Jain, Vivek Kumar; Jain, Vishal; Lakshmi, N.; Venugopalan, K.
As-spray-deposited structure of an Al20Si5Fe Osprey preform and its development during subsequent processing
The application of the Osprey process to the fabrication of newly developed Al-20Si-X alloys is at present a subject of considerable interest. This paper reports the results of a study on the as-spray deposited structural characteristics of an Al-20Si-5Fe alloy preform and their development during subsequent hot extrusion and high-temperature exposure, by means of X-ray diffraction, differential scanning calorimetry and
J. Zhou; J. Duszczyk; B. M. Korevaar
Microstructural development during consolidation of rapidly solidified Al-Fe-V-Si powder by VHP, extrusion and rolling
The rapid solidification of powder results in a high cooling rate which leads to microstructural refinement and extended solid solubility of alloying elements and thereby precipitation of fine dispersive phases during powder solidification and consolidation. During the last decade considerable research work has been done in the development of high temperature powder metallurgy aluminum alloys capable of competing with titanium alloys on a specific strength basis with the use of rapid solidification processes. The Al-Fe-V-Si family of alloys are one of the most promising on a basis of elevated temperature strength, stiffness and thermal stability. In previous studies, the Al-Fe-V-Si alloys were usually produced by melt spinning (both jet casting and planar flow casting) followed by consolidation of the resulting ribbons. The aim of the present study was to investigate the microstructural development of atomized Al-Fe-V-Si alloy powder during consolidation by vacuum hot pressing (VHP), extrusion and rolling.
Wang, Y.; Lorimer, G.W.; Sale, F.R. (Univ. of Manchester (United Kingdom). Manchester Materials Science Centre)
Crystallographic Orientation of the ? ? ?' Martensitic (Athermal) Transformation in a FeMnAlSi Steel
NASA Astrophysics Data System (ADS)
The presence of athermal ?- and ?-martensite ( ?') in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two athermal martensitic transformations described by ? ? ?' and ? ? ? ? ?'. The Shoji-Nishiyama orientation relationship was observed between ?-austenite and ?-martensite, while ?-martensite nucleated from ?-austenite exhibited a Kurdjumov-Sachs orientation relationship. Six crystallographic variants of ?-martensite consisting of three twin-related variant pairs were observed in ?-bands. A planar parallelism of {0001} ? || {110} ?' and a directional relation of lying within 1 deg of existed for these variants.
Pisarik, S. T.; Van Aken, D. C.
Effects of metallurgical parameters on the decomposition of pi-AlFeMgSi phase in Al-Si-Mg alloys and its influence on the mechanical properties
NASA Astrophysics Data System (ADS)
The formation of the pi-AlFeMgSi iron intermetallic phase in Al-Si-Mg alloys is known for its detrimental effect on ductility and strength, in that it is controlled by the Fe and Mg content of the alloy, as well as by the cooling rate. The current study was carried out with a view to investigating all the metallurgical parameters affecting the formation of the pi-phase iron intermetallic and, in turn, the role of the pi-phase as it relates to the tensile and impact properties of Al-Si-Mg alloys. Microstructural assessment was carried out by means of quantitative metallography using electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). The results indicate that increasing the Mg and Fe content increases the amount of the pi-AlMgFeSi phase formed. All the alloys containing low levels of iron regardless of the amount of Mg-content show low amounts of pi-phase iron intermetallic. The addition of trace amounts of Be has an observable effect in reducing the amount of the pi-phase formed in all the alloys studied. The pi-phase iron intermetallic particles appear to be segregated away from the modified Si in the Sr-modified alloys, particularly those solidified at a low cooling rate. The effects of different solution treatment times on the decomposition of the pi-phase were investigated in order to examine how this type of decomposition affected the chemistry of the matrix itself. After 8 hours of solution heat treatment and at Mg content of 0.4wt%, the pi-phase showed complete decomposition into fine beta-phase needles. The a-phase, however, showed only partial decomposition into beta-AlFeSi phase needles at Mg levels of over 0.4%wt. This type of decomposition was examined for the purposes of this study over extended periods of solution heat treatment time in Al-7Si-0.55Mg-0.1Fe alloy samples obtained at different cooling rates in order to evaluate the mechanism of pi to beta-phase decomposition. The results obtained show that the volume fraction of pi-AlFeMgSi phase decreases significantly at prolonged solution treatment times. The highest amount of the newly-formed beta-phase was observed in the solution treatment time range of 60 to 80 hours. An analysis of the chemical composition of the matrix using wavelength-dispersive spectroscopy (WDS) at different stages of solution heat treatment revealed that the pi to beta-phase decomposition during solution heat treatment results in a distinct increase in the Mg content of the matrix. Furthermore, no changes were observed in the calculated stoichiometries of the pi-phase or the beta-phase intermetallics during solution treatment in all the alloy samples studied. The study also investigated the decomposition of pi-AlFeMgSi into beta-phase needles during extended periods of solution heat treatment and its effects on the mechanical properties of Al-7Si-0.55Mg-0.1Fe alloys. The results obtained from the calculated quality index values show that the optimum solution treatment time for Sr-modified alloys is of the order of 12 hours. Using prolonged solution treatment time leads to the decomposition of a large amount of pi-phase into beta-phase needles, approximately 85%, thereby providing a slight improvement in the tensile properties at 80 hrs compared to standard heat treatment times; this improvement may be attributed to the increased amount of Mg in the matrix resulting from the decomposition of the pi-phase, and which is then available for precipitation as Mg2Si upon subsequent aging. An analysis of the results obtained from the Charpy impact test using unnotched samples shows that the greatest improvement in the initiation and propagation energies is obtained for the as-cast and heat-treated alloys when these alloys are solidified at a low cooling rate and modified with strontium. An increase in the solution treatment time improves the impact properties of the alloys compared to the as-cast condition. In accordance with this finding, the recommended solution treatment time at which the maximum initiation and propagation energy values can be obtained is 20 hou
Elsharkawi, Ehab A.
Structural and magnetic properties and tunnel magnetoresistance for Co2(Cr,Fe)Al and Co2FeSi full-Heusler alloys
We have investigated the structure and magnetization of Co2(Cr1-xFex)Al (0 <= x <= 1) and Co2FeSi full-Heusler alloy films deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultra-high vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). Magnetic tunnel junctions with a full-Huesler alloy electrode were fabricated with
K. Inomata; S. Okamura; A. Miyazaki; M. Kikuchi; N. Tezuka; M. Wojcik; E. Jedryka
Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al-20Si-5Fe alloys
The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 x 10{sup 5} K/s and 5 x 10{sup 7} K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 deg. C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated. Results showed a profound effect of the cooling rate, consolidation stage, and transition metals on the microstructure and mechanical strength of Al-20Si-5Fe alloys. While microstructural refining was obtained at both cooling rates, the microstructure of the atomized powder exhibited the formation of fine primary silicon ({approx} 1 {mu}m), eutectic Al-Si phase with eutectic spacing of {approx} 300 nm, and {delta}-iron intermetallic. Supersaturated Al matrix containing 5-7 at.% silicon and nanometric Si precipitates (20-40 nm) were determined in the microstructure of the melt-spun ribbons. The hot consolidation resulted in coarsening of Si particles in the atomized particles, and precipitation of Si and Fe-containing intermetallics from the supersaturated Al matrix in the ribbons. The consolidated ribbons exhibited higher mechanical strength compared to the atomized powders, particularly at elevated temperatures. The positive influence of the transition metals on the thermal stability of the Al-20Si-5Fe alloy was noticed, particularly in the Ni-containing alloy.
Rajabi, M.; Vahidi, M. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Simchi, A., E-mail: firstname.lastname@example.com [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology (INST), Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Davami, P. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of)
Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe
NASA Astrophysics Data System (ADS)
Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like ?-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of ?-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like ?-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, ?-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.
Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin
Neutrons Scattering and Gamma-Ray Production Cross Sections for N, O, Al, Si, Ca and Fe.
National Technical Information Service (NTIS)
Measurements of neutron elastic and inelastic scattering and gamma-ray production have been made on several elements with 9.0 and 11.0 MeV incident neutrons. Differential cross sections for N, O, Al, Si, Ca, and Fe are presented and integral cross section...
D. O. Nellis P. S. Buchanan T. C. Martin W. E. Tucker G. H. Williams
A study of damage under tensile loading in a new Al-Si-Fe alloy processed by the Osprey route
The mode of damage in tension of a new Al-Si-Fe alloy made by spray deposition was studied. This alloy has a composite type structure composed of silicon and intermetallic particles in an aluminium matrix. In situ tensile tests in the SEM, with gold microgrids deposited on the surface of the specimen as an indicator of local plastic strains, provide us
A. Mocellin; R. Fougeres; P. F. Gobin
Electronic spin state of Fe,Al-containing MgSiO3 perovskite at lower mantle conditions
NASA Astrophysics Data System (ADS)
We have investigated silicate perovskite with composition Mg0.83Fe0.21Al0.06Si0.91O3 relevant for the lower mantle at pressures up to 81 GPa and temperatures up to 2000 K using conventional Mössbauer spectroscopy and synchrotron Nuclear Forward Scattering (NFS) combined with double-sided laser heating in a diamond anvil cell. Room temperature Mössbauer and NFS spectra at low pressure are dominated by high-spin Fe2 +, with minor amounts of Fe3 + and a component assigned to a metastable position of high-spin Fe2 + in the A-site predicted by computational studies. NFS data show a sharp transition (< 20 GPa) from high-spin Fe2 + to a new component with extremely high quadrupole splitting, similar to previous studies. Mössbauer data show the same transition, but over a broader pressure range likely due to the higher pressure gradient. The new Fe2 + component is assigned to intermediate-spin Fe2 +, consistent with previous X-ray emission studies. NFS data at high temperatures and high pressures comparable to those in the lower mantle are consistent with the presence of Fe2 + only in the intermediate-spin state and Fe3 + only in the high-spin state. Our results are therefore consistent with the occurrence of spin crossover only in Fe2 + in Fe-, Al-containing perovskite within the lower mantle.
Kupenko, I.; McCammon, C.; Sinmyo, R.; Prescher, C.; Chumakov, A. I.; Kantor, A.; Rüffer, R.; Dubrovinsky, L.
Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys
NASA Astrophysics Data System (ADS)
A set of modified embedded-atom method (MEAM) potentials for the interactions between Al, Si, Mg, Cu, and Fe was developed from a combination of each element's MEAM potential in order to study metal alloying. Previously published MEAM parameters of single elements have been improved for better agreement to the generalized stacking fault energy (GSFE) curves when compared with ab initio generated GSFE curves. The MEAM parameters for element pairs were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure garnered from ab initio calculations, with adjustment to reproduce the ab initio heat of formation of the most stable binary compounds. The new MEAM potentials were validated by comparing the formation energies of defects, equilibrium volumes, elastic moduli, and heat of formation for several binary compounds with ab initio simulations and experiments. Single elements in their ground-state crystal structure were subjected to heating to test the potentials at elevated temperatures. An Al potential was modified to avoid formation of an unphysical solid structure at high temperatures. The thermal expansion coefficient of a compound with the composition of AA 6061 alloy was evaluated and compared with experimental values. MEAM potential tests performed in this work, utilizing the universal atomistic simulation environment (ASE), are distributed to facilitate reproducibility of the results.
Jelinek, B.; Groh, S.; Horstemeyer, M. F.; Houze, J.; Kim, S. G.; Wagner, G. J.; Moitra, A.; Baskes, M. I.
MgSiO3-FeSiO3-Al2O3 in the Earth's lower mantle: Perovskite and garnet at 1200 km depth
NASA Technical Reports Server (NTRS)
Natural pyroxene and garnet starting material are used to study the effects of joint Fe and Al substitution into MgSiO3 perovskite at approxmiately 50 GPa. Garnet is found to coexist with perovskite in samples containing both Fe and Al to pressures occurring deep into the lower mantel (approximately 1200 km depth). The volume of the perovskite unit cell is V(sub o(Angstrom(exp 3)) = 162.59 + 5.95x(sub FeSiO3) + 10.80x(sub Al2O3) with aluminum causing a significant increase in the distortion from the ideal cubic cell. On the basis of a proposed extension of the MgSiO3-Al2O3 high-pressure phase diagram toward FeSiO3, Fe is shown to partition preferentially into the garnet phase. The stability of garnet deep into the lower mantel may hinder the penetration of subducted slabs below the transition zone.
O'Neill, Bridget; Jeanloz, Raymond
Anomalous resonances in 29Si and 27Al NMR spectra of pyrope ([Mg,Fe]3Al2Si3O12) garnets: effects of paramagnetic cations.
In oxide and silicate materials, particularly naturally-occurring minerals with contents of iron oxides greater than a few percent, paramagnetic impurities are well-known to broaden MAS NMR peaks, decrease relaxation times, and even cause overall loss of signal intensity. However, detection of resolved, discrete peaks that are shifted in frequency by nearby unpaired electron spins is rare in such systems. We report here high-resolution (27)Al and (29)Si spectra for synthetic and natural samples of pyrope garnet ([Mg,Fe](3)Al(2)Si(3)O(12)), the latter containing up to 3.5 wt% FeO. For both nuclides, spectra contain anomalous NMR peaks at frequencies that are 25 to 200 ppm from normal ranges, possibly through pseudocontact shifts induced by paramagnetic cations. Quantitation of peak areas suggests that signals from nuclides with such cations in their first shell may be broadened enough to be unobservable, while those with paramagnetics in their second cation shells may be substantially shifted. Overall spin-lattice relaxation rates are greatly enhanced by such impurities, and shifted resonances relax much faster than the unshifted main peaks. A high symmetry crystal structure (in this case cubic), which limits the number of different cation-cation distances in each shell, combined with a relatively low (non-cubic) symmetry for the sites hosting the magnetic cations, may be needed to readily detect such features. PMID:19652824
Stebbins, Jonathan F; Kelsey, Kimberly E
Characterization of centrifugally atomized Al12Si5Fe3Cu1Mg(wt%) alloy powder and extruded rod
The Al-12Si-5Fe-3Cu-1Mg(wt%) alloy was rapidly solidified by centrifugal atomization. The microstructural characteristics of rapidly solidified powder and the microstructure changes with heat treatment were investigated in terms and related to powder size. The microstructures of the powder consisted of dendritic a-Al, eutectic phase, Cu-rich phase, and needle-like intermetallic compounds. These phases were much finer than that of ingot cast structure
S. S. Cho; B. S. Chun; C. H. Won; B. S. Lee; H. K. Kim; B. J. Song; M. Ryu
Electromagnetic properties of Fe-Si-Al/BaTiO3/Nd2Fe14B particulate composites at microwave frequencies
NASA Astrophysics Data System (ADS)
Ferroelectric/ferromagnetic (soft and hard) three-phase microwave absorption composites, consisting of Fe-Si-Al/BaTiO3/Nd2Fe14B, are presented, which were fabricated by mechanical ball milling. The microstructure, magnetic, and microwave properties were measured, demonstrating significant improvement in magnetization and coercivity, compared to those single phase materials. In particular, either ferroelectric or hard magnetic phase presents a strong tunability of permeability and permittivity with frequency, which can tailor a frequency band of microwave absorption. The experiments indicate that an optimal reflection loss of the Fe-Si-Al/BaTiO3/Nd2Fe14B was tuned from 2 to 9.52 GHz, whereas the peak value was remarkably enhanced by 62.8%. Therefore, the three-phase microwave absorption composites may remain thin but have great potential to be used at high frequency range.
Wang, Xian; Xu, Xiaojun; Gong, Wei; Feng, Zekun; Gong, Rongzhou
Optimization of exchange bias in Co2FeAl0.5Si0.5 Heusler alloy layers
NASA Astrophysics Data System (ADS)
We have fabricated and investigated IrMn3/Co2FeAl0.5Si0.5 stacks to meet the criteria for future spintronic device applications which requires low-temperature crystallisation (<250 °C) and a large exchange bias Hex (>500 Oe). Such a system would form the pinned layer in spin-valve or tunnel junction applications. We have demonstrated that annealing at 300 °C which can achieve crystalline ordering in the Co2FeAl0.5Si0.5 layer giving ˜80% of the predicted saturation magnetisation. We have also induced an exchange bias of ˜240 Oe at the interface. These values are close to the above criteria and confirm the potential of using antiferromagnet/Heusler-alloy stacks in current Si-based processes.
Hirohata, Atsufumi; Izumida, Keisuke; Ishizawa, Satoshi; Sagar, James; Nakayama, Tadachika
High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process
The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.
Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.
The role of tree uprooting dynamics on the dynamics of Fe (Mn, Al and Si) forms in different forest soils
NASA Astrophysics Data System (ADS)
Tree uprooting dynamics plays an important role in the development of forest ecosystems. This process causes bioturbation of soils and creates new microenvironments which consist of pits and mounds. These microtopographical forms could persist for some thousands of years. Pits and mounds undergo different pedogenesis in comparison to adjacent undisturbed soils. The stage of pedogenesis can be assessed according to the results of fractionation of Fe and also partially Mn, Al and Si. The main aim of this contribution is to assess the fractionation of Fe, Mn, Al and Si for three different soil regions. Soil samples were collected at three localities occurred along hypothetical gradient of soil weathering and leaching processes: The first was a (spruce)-fir-beech natural forest in the Razula region. The second location is the same type of natural forest in Zofin; however it has contrasting lithology. Both these natural forests are located in the Czech Republic (CZ). The third forest was a northern hardwood forest in Upper Peninsula, Michigan, USA. The prevailing soil types - Haplic Cambisols have formed on flysch parent materials in the Razula reserve; Entic Podzols have developed on granite residuum at the Zofin reserve, and Albic Podzols occurred in outwash parent materials at the Michigan sites (Šamonil et al., in press). In total 790 soil samples were analysed. These samples were collected from 5 depths (0-10, 15, 30, 50 and 100 cm) within the pit, mound and control, currently undisturbed position. For each sample, content of Fe (and Mn, Al, Si) forms: exchangeable, crystalline, and amorphous together with organically complexed Fe were determined. We generally observed an increased content of Fe soil forms in the pits of studied treethrows. The content of Fe forms increased along depth gradient at the disturbed sites. However, exchangeable Fe was most abundant in the 0-10cm layer which corresponds to the A horizon. Naturally, if present, the E horizon exhibited the lowest content of exchangeable Fe forms. The content of crystalline Fe forms also increased with the age of the windthrow. Differences in the amounts of Fe, Mn, Al and Si forms were observed between all studied localities. Research was supported by the Czech Science Foundation (project No. P504/11/2135). Šamonil P., Schaetzl R. J., Valtera M., Goliáš V., Baldrian P., Vaší?ková I., Adam D., Janík D., Hort L. (in press). Crossdating of disturbances by tree uprooting: Can treethrow microtopography persist for 6,000 years? Forest Ecology and Management.
Tejnecký, V.; Samonil, P.; Boruvka, L.; Nikodem, A.; Drabek, O.; Valtera, M.
Pyroxene-garnet solid-solution equilibria in the systems Mg4Si4O12Mg3Al2Si3O12 and Fe4Si4O12Fe3Al2Si3O12 at high pressures and temperatures
Pyroxene-garnet solid-solution equilibria have been studied in the pressure range 41-200 kbar and over the temperature range 850-1,450°C for the system Mg4Si4O12-Mg3Al2Si3O12, and in the pressure range 30-105 kbar and over the temperature range 1,000-1,300°C for the system Fe4Si4O12-Fe3Al2Si3O12. At 1,000°C, the solid solubility of enstatite (MgSiO3) in pyrope (Mg3Al2Si3O12) increases gradually to 140 kbar and then increases suddenly in
M. Akaogi; S. Akimoto
Magnetic Moments and Hyperfine Parameters of Fe3-xCrxAl0.5Si0.5
NASA Astrophysics Data System (ADS)
Results of X-ray, neutron, magnetization and Mössbauer measurements on polycrystalline samples of Fe3-xCrx Al0.5Si0.5 (x=0, 0.125, 0.250, 0.375, and 0.5) alloys, crystallizing in DO3 type of structure, are presented. X-ray and neutron diffraction confirmed the phase homogeneity of all the samples. The unit cell volume has been proved to be independent of the chromium content. Neutron and Mössbauer measurements disclosed that Cr atoms occupy preferentially B-sites, while D-sites are almost entirely occupied by Al and Si. The total magnetisation as well as the individual magnetic moments ?Fe(A,C), ?Fe(B) and ?Cr(B,D) have been found to vary linearly with chromium concentration. Influence of local environments on the formation of magnetic moments in Fe3Al0.5Si0.5 when chromium is substituted for iron was examined using self-consistent spin-polarized tight-binding linear muffin-tin orbital method (TB-LMTO).
Re?ko, Katarzyna; Go, Anna; Satu?a, Dariusz; Biernacka, Maria; Dobrzy?ski, Ludwik; Waliszewski, Janusz; Milczarek, Jacek J.; Szyma?ski, Krzysztof
Post-irradiation examination of AlFeNi cladded U 3Si 2 fuel plates irradiated under severe conditions
NASA Astrophysics Data System (ADS)
Three full size AlFeNi cladded U 3Si 2 fuel plates were irradiated in the BR2 reactor of the Belgian Nuclear Research Centre (SCK·CEN) under relatively severe, but well defined conditions. The irradiation was part of the qualification campaign for the fuel to be used in the future Jules Horowitz reactor in Cadarache, France. After the irradiation, the fuel plates were submitted to an extensive post-irradiation campaign in the hot cell laboratory of SCK·CEN. The PIE shows that the fuel plates withstood the irradiation successfully, as no detrimental defects have been found. At the cladding surface, a multilayered corrosion oxide film has formed. The U-Al-Si layer resulting from the interaction between the U 3Si 2 fuel and the Al matrix, has been quantified as U(Al,Si) 4.6. It is found that the composition of the fuel particles is not homogenous; zones of USi and U 3Si 2 are observed and measured. The fission gas-related bubbles generated in both phases show a different morphology. In the USi fuel, the bubbles are small and numerous while in U 3Si 2 the bubbles are larger but there are fewer.
Leenaers, A.; Koonen, E.; Parthoens, Y.; Lemoine, P.; Van den Berghe, S.
Magnetic properties of Fe75Si15Al10 crystalline powders and domain structural observations using Lorentz transmission electron microscopy
NASA Astrophysics Data System (ADS)
Fe75Si15Al10 flakes with soft magnetism were manufactured by microforging granules and annealing them at temperatures up to 800 °C in Ar atmosphere. Spherical granules 50 ?m in diameter were transferred after milling to a thin plate of 1 ?m thickness with elongated subgrains. After annealing, the deformed subgrains were recrystallized with equiaxed grains 200 nm in size. Lorentz transmission electron microscopy and Foucault imaging revealed the milled and annealed flakes to consist of in-plane spins within a longitudinal double-layered domain structure. The magnetic properties of the Fe75Si15Al10 flakes depend strongly on platelike shape anisotropy and orientation anisotropy due to the {200} texture, which can easily induce magnetization through in-plane spin directions.
Ahn, Jae-Pyoung; Yoon, Sang-Won; Kim, Sang-Woo
Magnetic properties of spray-formed Fe–6.5%Si and Fe–6.5%Si–1.0%Al after rolling and heat treatment
The maximum silicon content in commercial Fe–Si steels is limited to about 3.5wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold\\/hot rolling. However, the best magnetic properties are attained at about 6.5wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our research group has
Claudemiro Bolfarini; Mário Cézar Alves Silva; Alberto Moreira Jorge; Claudio Shyinti Kiminami; Walter José Botta
Magnetic properties of spray-formed Fe 6.5%Si and Fe 6.5%Si 1.0%Al after rolling and heat treatment
The maximum silicon content in commercial Fe Si steels is limited to about 3.5 wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold\\/hot rolling. However, the best magnetic properties are attained at about 6.5 wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our
Claudemiro Bolfarini; Mário Cézar Alves Silva; Alberto Moreira Jorge; Claudio Shyinti Kiminami; Walter José Botta
Post-irradiation examination of AlFeNi cladded U 3Si 2 fuel plates irradiated under severe conditions
Three full size AlFeNi cladded U3Si2 fuel plates were irradiated in the BR2 reactor of the Belgian Nuclear Research Centre (SCK·CEN) under relatively severe, but well defined conditions. The irradiation was part of the qualification campaign for the fuel to be used in the future Jules Horowitz reactor in Cadarache, France. After the irradiation, the fuel plates were submitted to
A. Leenaers; E. Koonen; Y. Parthoens; P. Lemoine; S. Van den Berghe
Dynamic mechanical properties of the Fe–30Mn–3Si–4Al TWIP steel after different heat treatments
The dynamic mechanical properties of Fe–30Mn–3Si–4Al TWIP steel were studied using a split-Hopkinson pressure bar at room temperature with strain rates between 700 and 5000s?1. It was found that the effect of heat treatments on the dynamic mechanical properties is limited. With increasing the strain rate from 700 to 2500s?1, the strain hardening dominates the process. When the strain rate
Zhi-ping Xiong; Xue-ping Ren; Wei-ping Bao; Shu-xia Li; Hai-tao Qu
Microstructural features and heat flow analysis of atomized and spray-formed Al-Fe-V-Si alloy
Microstructural features of rapidly solidified powders and preforms of Al80Fe10V4Si6 alloy produced by spray forming process have been studied. The atomization and spray deposition were carried out using a\\u000a confined gas atomization process and the microstructural features were characterized using scanning electron microscopy and\\u000a transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The microstructure of a wide size range
A. K. Srivastava; S. N. Ojha; S. Ranganathan
TiC particulate-reinforced Al–20Si–5Fe composite fabricated by melt in situ reaction spray forming
A novel technique in which TiC particulates are fabricated by an in situ reaction in molten aluminum is introduced for producing TiC\\/Al–20Si–5Fe composite. In order to reveal the characteristics of the technique, in this paper the formation mechanism of TiC particulates obtained by this method is studied. Both theoretical and experimental results have shown that the TiC particulates are formed
B Yang; F Wang; H Cui; X. J Duan; S. C Hu; J. S Zhang
Magnetic Fe, Si, Al-Rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica
NASA Technical Reports Server (NTRS)
The geological boundary between Triassic and Permian strata coincides with the greatest life extinction in the Earth's history. Although the cause of the extinction is still the subject of intense debates, recent discoveries in the P-T boundary layer of shocked quartz grains, fullerenes with the extraterrestrial noble gases, Fe metal nuggets, and chondritic meteorite fragments all point to a powerful collision of Earth with a celestial body in the late Permian. Here we report the discovery of magnetic Fe, Si, Al-rich impact spherules which accompany the chondritic meteorite fragments in some samples from the P-T boundary layer at Graphite Peak, Antarctica.
Petaev, M. I.; Jacobsen, S. B.; Basu, A. R.; Becker, L.
Epitaxial films of Heusler compound Co2FeAl0.5Si0.5 with high crystalline quality grown by off-axis sputtering
NASA Astrophysics Data System (ADS)
Co2FeAl0.5Si0.5 films with a surface roughness of 0.12 nm have been grown epitaxially on lattice-matched MgAl2O4 (001) substrates by off-axis sputtering. X-ray diffraction shows pronounced Laue oscillations, rocking curves as narrow as 0.0043°, and clear Co2FeAl0.5Si0.5 (111) peaks indicating L21 ordering. Magnetic characterizations show a clear magnetocrystalline anisotropy comprising cubic and epitaxy-induced uniaxial terms. Nuclear magnetic resonance measurements reveal L21 order of 81% in the Co2FeAl0.5Si0.5 films. Magnetotransport measurements show a distinct separation of anisotropic magnetoresistance and ordinary magnetoresistance. These results demonstrate the state-of-the-art crystalline quality and magnetic uniformity of the Co2FeAl0.5Si0.5 films.
Peters, B.; Alfonsov, A.; Blum, C. G. F.; Hageman, Stephen J.; Woodward, P. M.; Wurmehl, S.; Büchner, B.; Yang, F. Y.
Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12
The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.
Anovitz, L. M.; Essene, E. J.; Metz, G. W.; Bohlen, S. R.; Westrum, Jr. , E. F.; Hemingway, B. S.
Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics
NASA Astrophysics Data System (ADS)
T he oxidation behaviors of composites SiAlON/MgAlON phases (?-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 °C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.
Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri
Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline Al-Fe-V-Si alloys.
A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al-based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two-phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe-V-Si-rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion-resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro-chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7549001
Thomas, S C; Birss, V I; Steele, D; Tessier, D
Thermodynamic modelling of phase equilibria in melts of Fe-Ca-Al-Si-Mn-V-Nb-Ni-Mo-P-C-O system
NASA Astrophysics Data System (ADS)
A thermodynamic analysis of the phase equilibria in the Fe-Ca-Al-Si-Mn-V-Nb-Ni-Mo-P-C-O system at fixed concentrations of silicon, manganese, vanadium, niobium, nickel, molybdenum, phosphorus and carbon was performed. The formation of nonmetallic phases at 1873 K in liquid metal solutions of various compositions was studied. It has been established that, depending on the concentrations of calcium and aluminum, the metal melt can be in equilibrium with (FeO, CaO, Al2O3, SiO2, MnO) liquid solutions, |FeO, CaO, MnO| and |Al2O3, V2O3| solid solutions, individual compounds 3Al2O3·SiO2, CaO·2Al2O3, CaO·6Al2O3 and {Ca} gas.
Tanklevskaya, N. M.; Chernova, L. A.; Mikhailov, G. G.
Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase
NASA Astrophysics Data System (ADS)
Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined ?-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized ?-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the ?-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined ?-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized ?-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.
Hou, L. G.; Yu, H.; Cui, H.; Cai, Y. H.; Zhuang, L. Z.; Zhang, J. S.
Influence of Co addition on the magnetocaloric effect of FeCoSiAlGaPCB amorphous alloys
The FeCoSiAlGaPCB alloys can be prepared as bulk amorphous materials, with outstanding mechanical properties and increased electrical resistivity. These features can be beneficial for their application as a magnetic refrigerant. The influence of Co addition on the magnetic entropy change of the alloy has been studied. This compositional modification displaces the temperature of the peak entropy change closer to room temperature, but reduces the refrigerant capacity of the material. For the Co-free alloy, the peak entropy change is increased with respect to a Finemet alloy containing Mo, but its refrigerant capacity is not enhanced.
Franco, V.; Borrego, J.M.; Conde, A.; Roth, S. [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Leibniz Institut fuer Metallische Werkstoffe, IFW Dresden, Postfach 270016, D 01171 Dresden (Germany)
Fracture of an Osprey{trademark} AlSiFe alloy: A microstructure based model for fracture of microheterogeneous materials
This paper is concerned with the failure in tension of an AlSiFe alloy with a particular composite type microstructure. The experimental observations allow to distinguish three main steps in the damage process: nucleation by the cracking of some big silicon particles, increasing of the number of cracked particles with macroscopic plastic strain and final failure by joining of the microcracks thus created. This schematization is the basis of the modelization which requires Eshelby type calculations and energetic balances. This model is in good agreement with experiment for the studied alloy and makes the microstructural parameters of the material clearly appear.
Mocellin, A.; Fougeres, R. [INSA Lyon, Villeurbanne (France)] [INSA Lyon, Villeurbanne (France); Brechet, Y. [ENSEEG, Saint Martin d`Heres (France)] [ENSEEG, Saint Martin d`Heres (France)
Theoretical phase relations involving cordierite and garnet in the system MgO-FeO-Al 2 O 3 SiO 2
Theoretical stability relations have been derived between the phases cordierite (Cd), garnet (Ga), hypersthene (Hy), olivine (Ol), sapphirine (Sa), spinel (Sp), sillimanite (Si) and quartz (Qz) in the system MgO-FeO-Al2O3-SiO2. Natural rock data and experimental evidence suggest that the Mg\\/Mg+Fe2+ ratio (X) of coexisting ferromagnesian phases decreases as follows: XCd>XSa>XHy>XOl>XSp>XGa. By use of this information four stable invariant points are
B. J. Hensen
Giant magnetoelectric coefficients in (Fe90Co10)78Si12B10-AlN thin film composites
NASA Astrophysics Data System (ADS)
Thin film magnetoelectric (ME) two-two composites consisting of AlN and amorphous (Fe90Co10)78Si12B10 layers were fabricated by magnetron sputtering on Si (100) substrates. Upon magnetic field annealing they show an extremely high ME coefficient of 737 V/cm Oe at mechanical resonance at 753 Hz and 3.1 V/cm Oe out of resonance at 100 Hz. These are the highest reported ME coefficients in thin film composites ever. Furthermore, the induced magnetic anisotropy by field annealing serves the possibility to obtain a sensor element with a pronounced sensitivity in only one dimension, which allows the realization of a three-dimensional vector field sensor.
Greve, Henry; Woltermann, Eric; Quenzer, Hans-Joachim; Wagner, Bernhard; Quandt, Eckhard
Electronic Structure of Iron in (Mg,Fe)(Si,Al)O3 Glass up to 93 GPa
NASA Astrophysics Data System (ADS)
Recent studies have found changes in the electronic spin state of iron in crystalline mantle silicate and oxide phases. However, little is known for the spin state of iron in melts in the mantle. We have measured the Mössbauer spectra of (Mg0.8Fe0.2)(Si0.9Al0.1)O3 glass up to 93 GPa at 300 K in the diamond-anvil cell at Sector 3 of the APS. At ambient conditions, 64% of iron in the glass has a high quadrupole splitting value (QS = 2.2 mm/s) consistent with high-spin Fe2+ and 36% has a low QS value (= 0.7 mm/s) consistent with high-spin Fe3+. The ratio of high QS to low QS populations is unchanged by 6 GPa. The population of the low QS site increases rapidly from 34% to 57% between 6 and 32 GPa, followed by a more gradual increase to 68% between 32 and 93 GPa, indicating that 50% of Fe2+ changes from high QS to low QS in the pressure range. According to recent first-principles calculations, low- or intermediate-spin Fe2+ has QS = 0.5 ˜1.5~mm/s which overlaps with the QS of high-spin Fe3+. Therefore, the increase in the low QS site population can be related to a decrease in the spin moment of 50% of Fe2+ between 6 and 93 GPa. If our findings are applicable for silicate melts, the spin transition in silicate melts may occur over a much wider depth range (200--2500 km) starting at a much shallow depth (200 km) than those in perovskite and ferropericlase in the mantle.
Gu, C.; Catalli, K.; Grocholski, B.; Shim, S.; Gao, L.; Alp, E. E.; Evans, W.
Microstructural features and heat flow analysis of atomized and spray-formed Al-Fe-V-Si alloy
Microstructural features of rapidly solidified powders and preforms of Al{sub 80}Fe{sub 10}V{sub 4}Si{sub 6} alloy produced by spray forming process have been studied. The atomization and spray deposition were carried out using a confined gas atomization process and the microstructural features were characterized using scanning electron microscopy and transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The microstructure of a wide size range of atomized powders invariably revealed cellular and dendritic morphology. The extent of dendritic region and the dendritic arm spacing were observed to increase with power particle size. The TEM investigations indicated the presence of ultrafine second-phase particles in the intercellular or interdendritic regions. In contrast, the spray deposits of the alloy showed considerable variation in microstructure and size and dispersion of the second-phase particles at specific distances from the deposit-substrate interface and the exterior regions of the deposit. Nevertheless, considerable homogeneity was observed in the microstructure toward the center of the spray deposit. The formation and distribution of a cubic phase {alpha}-Al(Fe, V)Si has been characterized in both atomized powders and spray deposits. A one-dimensional heat flow model has been used to analyze the evolution of microstructure during atomization and also during spray deposition processing of this alloy. The results indicate that thermal history of droplets in the spray on deposition surface and their solidification behavior considerably influence the microstructural features of the spray deposits.
Srivastava, A.K.; Ranganathan, S. [Indian Inst. of Science, Bangalore (India); Ojha, S.N. [Banaras Hindu Univ., Varanasi (India)
Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution
NASA Astrophysics Data System (ADS)
The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 °C to 1500 °C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.
Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri
Micro- and nanocomposite Ti-Al-N/Ni-Cr-B-Si-Fe-based protective coatings: Structure and properties
NASA Astrophysics Data System (ADS)
A new type of nanocomposite Ti-Al-N/Ni-Cr-B-Si-Fe-based coatings 70-90 ?m thick produced by combined magnetron sputtering and a plasma detonation technology is created and studied. Phases Ti3AlN + Ti3Al2N2 and the phases caused by the interaction of plasma with a thick Al3Ti + Ni3Ti coating are detected in the coatings. The TiAlN phase has a grain size of 18-24 nm, and other phases has a grain size of 35-90 nm. The elastic modulus of the Ti-Al-N coating is E = 342 ± 1 GPa and its average hardness is H = 20.8 ± 1.8 GPa. The corrosion rate of this coating is very low, 4.8 ?g/year, which is about three orders of magnitude lower than that of stainless steel (substrate). Wear tests performed according to the cylinder-surface scheme demonstrate high wear resistance and high adhesion between the thick and thin coatings.
Pogrebnyak, A. D.; Drobyshevskaya, A. A.; Beresnev, V. M.; Kylyshkanov, M. K.; Kirik, T. V.; Dub, S. N.; Komarov, F. F.; Shipilenko, A. P.; Tuleushev, Yu. Zh.
Search for half-metallic magnets with large half-metallic gaps in the quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb)
NASA Astrophysics Data System (ADS)
We investigate the electronic structure and magnetic properties of the twelve quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb) by using the first-principles calculations. It is shown that only CoFeTiSi, CoFeTiAs and CoFeVSb are half-metallic ferromagnets with considerable half-metallic gaps of 0.31, 0.18 and 0.17 eV, respectively. CoFeTiAl and CoFeTiGa are conventional semiconductors, and other alloys exhibit nearly half-metallicity or their half-metallic gaps are almost zero eV. We also find that the half-metallicities of CoFeTiSi, CoFeTiAs and CoFeVSb can be preserved under appropriate uniform and in-plane strains. The considerable half-metallic gaps and the robust half-metallicities under uniform and in-plane strains make CoFeTiSi, CoFeTiAs and CoFeVSb promising candidates for spintronic applications.
Xiong, Lun; Yi, Lin; Gao, G. Y.
Giant Tunnel Magnetoresistance at Room Temperature for Junctions using Full-Heusler Co2FeAl0.5Si0.5 Electrodes
The authors have investigated the tunnel magnetoresistance (TMR) effect of magnetic tunnel junctions (MTJs) with Co2FeAl0.5Si0.5 full-Heusler electrodes and a MgO barrier in the thickness range of 1.5-2.5 nm. A cross-sectional transmission electron micrograph showed the epitaxial growth of both the upper and lower Co2FeAl0.5Si0.5 layers and a MgO barrier and some distortion in the MgO barrier after annealing above
Nobuki Tezuka; Naomichi Ikeda; Satoshi Sugimoto; Koichiro Inomata
Effect of the addition of Mn on the tensile properties of a spray-formed and extruded Al-9Si-4Cu-1Fe alloy
NASA Astrophysics Data System (ADS)
The microstructure and the tensile properties of a spray-formed and extruded Al- 9Si-4Cu-1Fe alloy were investigated. Manganese (0.3, 1, 2 in wt%) was added to the alloy to avoid the formation of the needle-like ?-AlFeSi intermetallic phases that are highly detrimental to the alloy's ductility. The deposits were extruded at 623K with a n area reduction of 5 to 1. Small faceted dispersoids surrounding the equiaxial ?-Al matrix, mainly in the form of silicon particles, were identified by SEM-EDS, as well as the Mn-containing ?-Al15(Fe,Mn)3Si2 phase. The presence of the needle-like ?-Al(Fe,Mn)Si was scanty, even with the lowest Mn content. The room temperature tensile tests of all the extruded alloys showed a significant increase in elongation to fracture when compared with the values observed fo r the as-spray formed deposits.This result can be ascribed to the elimination of porosity promoted by the extrusion process and to the smaller grain size of the extruded samples. PUBLISHER'S NOTE This article by Benetti et al was published in error, it was a duplicate of article 012114 which appears later in this volume, the duplicate PDF and references have been deleted. The missing article by S Jayalakshmi, E Fleury and D J Sordelet, which forms part of the section HYDROGEN IN METASTABLE ALLOYS, now appears at the end of the volume (012120).
Benetti, G. D.; Jorge, A. M., Jr.; Kiminami, C. S.; Botta, W. J.; Bolfarini, C.
Phase relations associated with the aluminum blast furnace: Aluminum oxycarbide melts and Al-C-X (X=Fe, Si) liquid alloys
The thermodynamic properties and the phase relations were evaluated and estimated for the Al-O-C, Al-Si-C, and Al-Fe-C systems\\u000a which are important to understand the chemical behavior in an aluminum blast furnace. The mixing properties of binary liquid\\u000a alloys, including metal-carbon systems, were represented by the Redlich-Kister equation. The properties of liquid Al?C and\\u000a Si?C alloys were estimated so as to
Harumi Yokokawa; Masao Fujishige; Seiichi Ujiie; Masayuki Dokiya
Thermodynamic properties of Fe- and Al-bearing MgSiO3 perovskite: an internally consistent LSDA+U study
NASA Astrophysics Data System (ADS)
To better understand the Earth's lower mantle (LM), thermodynamic properties (TDPs) of LM minerals with Fe and Al dopant should be illustrated more clearly. We have so far reported the TDPs of Fe-bearing MgO, MgSiO3 perovskite (Pv) and post perovskite. [1-4] We furthermore study the TDPs of Fe- and Al-bearing Pv, where the internally consistent LSDA+U method and the lattice dynamics method are applied. Two spin states, high (HS) and low spin state, two substitution sites, Mg and Si site, and several possible distribution configurations are considered. In the LM pressure range, HS Fe3+ substituted at the Mg site with Al3+ at the adjacent Si site (Fe-Al pair) is the most stable configuration and tends to distribute homogeneously in LM. Furthermore, negative frequency cannot be observed in the Fe-Al pair-bearing Pv, and Al contributes to middle frequency while Fe mainly to low part due to its heavy mass. This indicates that the Fe-Al pair is vibrationally stable. Incorporation of the pair for geophysically relevant concentrations can increase volume of Pv a little and has marginal effects on the TDPs of Pv except for thermal expansivity and Grüneisen parameter. Simulated bulk sound velocities and densities show that a composition close to pyrolite is accountable for the reference Earth model. References: [1] A. Metsue, and T. Tsuchiya, J. Geophys. Res. 116, B08207 (2011). [2] A. Metsue, and T. Tsuchiya, Geophys. J. Int. 190, 310 (2012). [3] H. Fukui, T. Tsuchiya, and A. Q. R. Baron, J. Geophys. Res. 117, B12202 (2012). [4] T. Tsuchiya, and X. Wang, J. Geophys. 118, 83 (2013).
Wang, X.; Tsuchiya, T.
Mössbauer studies on the shape effect of Fe84.94Si9.68Al5.38 particles on their microwave permeability
NASA Astrophysics Data System (ADS)
Ball milling for long time (such as 10, 20, and 30 h) can transform Fe84.94Si9.68Al5.38 alloy powders with irregular shapes into flakes. X-ray diffraction (XRD) and Mössbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D03-type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder ?-Fe(Si, Al) structure. There are more than 6 absorption peaks in the transmission Mössbauer spectra (TMSs) for the particles with D03-type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder ?-Fe(Si, Al) structure, which can be fitted with the distributions of Mössbauer parameters (Bhf, isomer shift). The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron Mössbauer spectra (CEMSs) also show the significantly different Fe-sites environments between the alloy surface and the inside.
Han, Man-Gui; Deng, Long-Jiang
Electronic structure and magnetism of Fe3-xVxX (X=Si, Ga, and Al) alloys by the KKR-CPA method
NASA Astrophysics Data System (ADS)
We present first-principles charge- and spin-self-consistent electronic structure computations on the Heusler-type disordered alloys Fe3-xVxX for three different metalloids X=(Si, Ga, and Al). In these calculations we use the methodology based on the Korringa-Kohn-Rostoker formalism and the coherent-potential approximation generalized to treat disorder in multicomponent complex alloys. Exchange correlation effects are incorporated within the local spin density approximation. Total energy calculations for Fe3-xVxSi show that V substitutes preferentially on the Fe(B) site, not on the Fe(A,C) site, in agreement with experiment. Furthermore, calculations have been carried out for Fe3-xVxX alloys (with x=0.25, 0.50, and 0.75), together with the end compounds Fe3X and Fe2VX, and the limiting cases of a single V impurity in Fe3X and a single Fe(B) impurity in Fe2VX. We delineate clearly how the electronic states and magnetic moments at various sites in Fe3-xVxX evolve as a function of the V content and the metalloid valence. Notably, the spectrum of Fe3-xVxX (X=Al and Ga) develops a pseudogap for the majority as well as minority spin states around the Fermi energy in the V-rich regime, which, together with local moments of Fe(B) impurities, may play a role in the anomalous behavior of the transport properties. The total magnetic moment in Fe3-xVxSi is found to decrease nonlinearly, and the Fe(B) moment to increase with increasing x; this is in contrast to expectations of the ``local environment'' model, which holds that the total moment should vary linearly while the Fe(B) moment should remain constant. The common-band model, which describes the formation of bonding and antibonding states with different weights on the different atoms, however, provides insight into the electronic structure of this class of compounds.
Bansil, A.; Kaprzyk, S.; Mijnarends, P. E.; Tobo?a, J.
Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF
The heat capacity of cryolite (Na3AlF6) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S0298 = 238.5 J/mol KS0T-S0298 = 145.114 ln T+ 193.009*10-3T- 10.366* 105 T2- 872.89 J/mol K (273-836.5 K)??STrans = 9.9J/mol KS0T-S0298 =198.414 ln T+73.203* 10-3T-63.814* 105 T2-1113.11 J/mol K (836.5-1153 K) with the transition temperature between ??- and ??-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system NaFeAlSiOF. The resultant phase diagrams allow constraints to be placed on the fO2, fF2, aSiO2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log fO2 is approximately -19.2, log fF2 is -31.9 to -33.2, and aSiO2 is -1.06 at assumed P T conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland. ?? 1987.
Anovitz, L. M.; Hemingway, B. S.; Westrum, Jr. , E. F.; Metz, G. W.; Essene, E. J.
Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems
NASA Technical Reports Server (NTRS)
The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.
Lemkey, F. D.; Gupta, H.; Nowotny, H.; Wayne, S. F.
Structure and magnetic properties of FeSiAl-based soft magnetic composite with AlN and Al2O3 insulating layer prepared by selective nitridation and oxidation
NASA Astrophysics Data System (ADS)
FeSiAl is widely used in switching power supply, filter inductors and pulse transformers. But when used under higher frequencies in some particular condition, it is required to reduce its high-frequency loss. Preparing a homogeneous insulating coating with good heat resistance and high resistivity, such as AlN and Al2O3, is supposed to be an effective way to reduce eddy current loss, which is less focused on. In this project, mixed AlN and Al2O3 insulating layers were prepared on the surface of FeSiAl powders after 30 min exposure at 1100 °C in high purity nitrogen atmosphere, by means of surface nitridation and oxidation. The results revealed that the insulating layers increase the electrical resistivity, and hence decrease the loss factor, improve the frequency stability and increase the quality factor, especially in the high-frequency range. The morphologies, microstructure and compositions of the oxidized and nitrided products on the surface were characterized by Scanning Electron Microscopy/Energy Disperse Spectroscopy, X-Ray Diffraction, Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Photoelectron Spectroscopy.
Zhong, Xiaoxi; Liu, Ying; Li, Jun; Wang, Yiwei
Tensile deformation of 2618 and Al-Fe-Si-V aluminum alloys at elevated temperatures
NASA Technical Reports Server (NTRS)
The present study experimentally characterizes the effects of elevated temperature on the uniaxial tensile behavior of ingot metallurgy 2618 Al alloy and the rapidly solidified FVS 0812 P/M alloy by means of two constitutive formulations: the Ramberg/Osgood equation and the Bodner-Partom (1975) incremental formulation for uniaxial tensile loading. The elastoplastic strain-hardening behavior of the ingot metallurgy alloy is equally well represented by either formulation. Both alloys deform similarly under decreasing load after only 1-5 percent uniform tensile strain, a response which is not described by either constitutive relation.
Leng, Y.; Porr, W. C., Jr.; Gangloff, R. P.
The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)
NASA Technical Reports Server (NTRS)
The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.
Schuon, S. R.
Al, Fe, and Si compounds in Tamm and Mehra-Jackson extracts from mucky-peaty-podzolic gley soil: Contents, reserves, and profile and particle-size distributions
NASA Astrophysics Data System (ADS)
Equal or comparable contents of Fe and Al extractable by Tamm and Mehra-Jackson solutions have been revealed in all the horizons of a loamy mucky-peaty-podzolic gley soil on binary deposits. The content of Si extractable by the Mehra-Jackson solution has exceeded that of oxalate-soluble Si by an order of magnitude. The distributions of Al in the Tamm solutions from the entire soil and its fractions of 1-5 and >5 ?m are of accumulative type with a maximum in the mucky H horizon and a gradual decrease of the content with depth in relation with the analogous distribution of Al-organic complexes. The maximum content of oxalate-soluble Al in the clay fraction has been found in the eluvial ELg horizon, which can be due to the partial dissolution of Al hydroxide interlayers in soil chlorites. The distribution of Fe in the entire soil has two maximums, in the H horizon due to the accumulation of Fe-organic complexes and in the concretion-rich ELnn,g horizon due to the accumulation of Fe hydroxides. Depletion of oxalate-soluble Fe in the eluvial ELg horizon has been observed in all the fractions, which can be related to its mobilization and removal under strongly acidic conditions and the development of reductive processes, as well as the enrichment of the concretion-rich horizon with these compounds because of an increase in pH and the development of conditions favorable for water stagnation and Fe segregation.
Sokolova, T. A.; Tolpeshta, I. I.; Maksimova, Yu. G.
Combinatorial investigation of the effects of the incorporation of Ti, Si, and Al on the performance of ?-Fe2O3 photoanodes.
The effect of adding small amounts of Ti, Si, and Al on the photoelectrochemical activity of ?-Fe(2)O(3) is investigated using a high-throughput combinatorial method. Quantitative ink jet printing is used to pattern iron oxide and dopant precursors onto conductive glass substrates. Subsequent pyrolysis yields a library of doped iron oxide electrodes that are screened for photoelectrolysis activity by immersing in an electrolyte and scanning a laser over the electrodes to map the photocurrent response. When Si and Al are individually added to iron oxide at the levels we studied, the photoelectrolysis activity decreased whereas low levels of Ti addition enhanced the photocurrents. Synergistic effects were observed resulting in enhanced photocurrents when multiple impurities were added to ?-Fe(2)O(3). PMID:21627308
He, Jianghua; Parkinson, B A
Modeling of viscosities of the partly crystallized slags in the Al2O3-CaO-``FeO''-SiO2 system
NASA Astrophysics Data System (ADS)
A viscosity model of the partly crystallized slag in the Al2O3-CaO-'FeO'-SiO2 system has been developed in conjunction with the thermodynamic computer package F*A*C*T. Proportions of solids crystallized out of the liquid phase and compositions of the remaining liquid phase predicted by F*A*C*T are used in the viscosity model. Various heterogeneous viscosity models have been tested using large experimental dataset in the Al2O3-CaO-'FeO'-SiO2 system in reducing conditions close to the equilibrium with metallic iron. The Roscoe equation with new empirical parameters was found to provide reasonable agreement with experimental data. Examples of model application to industrial nonferrous smelting slag systems are presented. This model can also be applied to coal ash slags.
Kondratiev, Alex; Jak, Evgueni
Impact of a long term fire retardant (Fire Trol 931) on the leaching of Na, Al, Fe, Mn, Cu and Si from a Mediterranean forest soil: a short-term, lab-scale study.
Long term fire retardant (LTR) application for forest fire prevention purposes as well as wildland fires can result in chemical leaching from forest soils. Large quantities of sodium (Na), aluminium (Al), iron (Fe), manganese (Mn), copper (Cu) and silicon (Si) in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The leaching of Na, Al, Fe, Mn, Cu and Si due to nitrogen based LTR application (Fire Trol 931) was studied at laboratory scale. The concentrations of Na(+), Al(3+), Fe(3+)/Fe(2+), Mn(2+), Cu(2+) and Si(4+) were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire. The leaching of Na, Fe and Si from treated pots was significantly greater than that from control pots. The leaching of Al, Mn and Cu was extremely low. PMID:24687225
Koufopoulou, Sofia; Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Pappa, Athina
Neutron yields from thick C, Al, Cu, and Pb targets bombarded by 400 MeV\\/nucleon Ar, Fe, Xe and 800 MeV\\/nucleon Si ions
The angular and energy distributions of neutrons produced by 400 MeV\\/nucleon Ar, Fe, and Xe, and 800 MeV\\/nucleon Si ions stopping in thick C, Al, Cu, and Pb targets were measured using the Heavy-Ion Medical Accelerator in Chiba of the National Institute of Radiological Science (NIRS), Japan. The neutron spectra in the forward direction have broad peaks which are located
T. Kurosawa; N. Nakao; T. Nakamura; H. Iwase; H. Sato; Y. Uwamino; A. Fukumura
Analysis of size distributions of primary oxide inclusions in Fe10 mass Pct Ni M ( M =Si, Ti, Al, Zr, and Ce) alloy
The planar and spatial size distributions of primary oxide inclusions were measured in an Fe-10 mass pct Ni alloy on deoxidation\\u000a with 0.2 mass pct M (M=Si, Ti, Al, Zr, and Ce). It was found that the size distribution of inclusions obtained at a certain magnification in microanalysis\\u000a was accurate only in a limited range of particle size, due to
Andrey Karasev; Hideaki Suito
Effect of annealing on the microstructure and mechanical properties of cold rolled Fe–24Mn–3Al–2Si–1Ni–0.06C TWIP steel
Fe–24Mn–3Al–2Si–1Ni–0.06C TWinning Induced Plasticity (TWIP) steel was 42% cold-rolled and isochronally annealed at temperatures between 600 and 850°C. Optical, secondary and transmission electron microscopy found that a majority of as cold-rolled grains contain a large fraction of primary twin densities and a smaller fraction of secondary twins. Partially recrystallised microstructures comprise a mix of recrystallised grains and annealing twins as
Dagoberto B. Santos; Ahmed A. Saleh; Azdiar A. Gazder; Andrew Carman; Dayanna M. Duarte; Érica A. S. Ribeiro; Berenice M. Gonzalez; Elena V. Pereloma
Effect of Ge addition to Si 50–55Al 25–20Fe 10Ni 5Cr 5Zr 5 alloys obtained by melt spinning
Microstructure of Si50-55Al25-20Fe10Ni5Cr5Zr5 alloys obtained by rapid solidification changes from homogeneously amorphous to heterogeneous — amorphous+c-Ge (c-Ge: crystalline Ge solid solution) by the addition of Ge. The size, volume fraction and composition of c-Ge particles depend on Ge concentration in the alloy. Fine particles, with a size less than 10 nm, were obtained at 7–10 at.% Ge. Small size and
D. V. Louzguine; A. Inoue
Microstructural evolution during annealing of the melt-spun ternary hypoeutectic Al–7.6Si–3.3Fe (in wt.%) alloy
A ternary hypoeutectic Al–7.6 wt.%Si–3.3 wt.%Fe alloy was rapidly quenched at cooling rates between 106 and 107 K\\/s using the melt-spinning technique. Differential scanning calorimetry (DSC) scan of the as-quenched ribbon revealed a small exothermic peak at 348°C, attributed to the silicon particle coarsening and two endothermic peaks: one at 585°C and the other at 600°C corresponding to ternary eutectic
N Ünlü; A Genç; M. L Öveço?lu; E. J Lavernia; F. H Froes
Thermostability and magnetic properties of Sm 2(Fe,M) 17(C,N) y (M=Ga, Al and Si)
NASA Astrophysics Data System (ADS)
The effect of heat treatments on the interstitial nitrides and carbides prepared from Sm 2(Fe,M) 17 and Sm 2Fe 15Ga 2C 2 by gas-solid reaction (GSR) was investigated in order to understand more about the influence of the substitutions M=Ga, Al and Si on the thermostability of these compounds. X-ray diffraction measurements of the heat-treated samples have shown that all of these substitutions improve the thermostability of the Th 2Zn 17-type interstitial structure, with Al having the smallest influence and Si and Ga having a stronger influence on the thermostability. Contrary to the nitrides, the carbides prepared by GSR can be significantly stabilized with an increasing amount of the stabilizing elements. Already for a small amount of the substitution element, e.g. Sm 2Fe 16.5Ga 0.5, the 2 : 17-type interstitial phase was stabilized up to 750°C. Carburization at temperatures above 500°C was possible for the stabilized 2 : 17 compounds making possible much shorter carburization times for high C contents. Investigations on Sm 2Fe 15Ga 2C y have revealed a dependence of the thermostability on the amount of absorbed C and on the processing route for the interstitial modification by GSR. A coercivity ?0JHc up to about 2.8 T was obtained for Sm 2Fe 15Ga 2C 2N showing the magnetic potential of these modified compounds.
Handstein, A.; Kubis, M.; Cao, L.; Gebel, B.; Müller, K.-H.
Demonstration of half-metallicity in fermi-level-tuned Heusler alloy Co2FeAl0.5Si0.5 at room temperature.
Fermi level tuning has been successfully demonstrated in Co-based full-Heusler alloy Co(2)FeAl(0.5)Si(0.5) (CFAS). The half-metallic band gap of CFAS was proved by the behavior of differential conductance of CFAS/(MgAl(2))O(x)/CoFe magnetic tunneling junctions with an unexplored crystalline (MgAl(2))O(x) barrier. CFAS exhibits the highest effective spin polarization (P_{eff}) at 300 K and the weakest temperature dependence of P_{eff} among all known half metals. Further study shows that P_{eff} of CFAS decays with increasing temperature (T) following T;{3/2} law perfectly, which indicates that the depolarization of CFAS is determined by spin wave excitation only. PMID:19659034
Shan, R; Sukegawa, H; Wang, W H; Kodzuka, M; Furubayashi, T; Ohkubo, T; Mitani, S; Inomata, K; Hono, K
On the Formation of non-metallic inclusions in fe-50 pct Ni type alloys by deoxidation with Mn, Si, and Al
NASA Astrophysics Data System (ADS)
This investigation deals with deoxidation experiments in 30 g lab melts of Fe-50 pct Ni alloys. After deoxidation with different amounts of Mn, Si and Al and their combinations the samples were quenched into water at different times. Metallographic studies comprising light microscopy, scanning electron microscopy, electron microprobe and image analysis were performed. Classical nucleation theory was used for computation of the different supersaturation with oxygen or the deoxidant necessary for homogeneous nucleation. The different deoxidation reactions and the transformation of inclusions due to diffusion of oxygen, or the deoxidant, from or into the inclusions was treated for the different cases of deoxidation. Most deoxidation reactions take place within some seconds. The experimental results were to be used to estimate the pertinent interfacial tensions between the oxides and the melt and the values obtained for the different oxides seemed to be reasonable. The diffusional computations were successfully used for predicting the different transformations taking place. For example, in deoxidation with 0.03 pct Si the oxygen solubility is controlled by the equilibrium with liquid FeO ? SiO2. The time taken to reach equilibrium is determined by the number of inclusions and the particle size. In deoxidation with 0.1 pct Si or more, the equilibrium is controlled by SiO2 inclusions and the time taken to reach equilibrium, less than 1 s, is much shorter compared to the samples with 0.03 pct Si. The deoxidation reactions with aluminum were treated in the same way, and it was shown that the number of particles determined the time elapsing before equilibrium with respect to the formation of FeOAl2O3 or A12O3. It was further shown that transformation of primary liquid FeOAl2O3 with high contents of FeO into solid FeOAl2O3 was expected to occur within one second. However, the experiments showed that it took somewhat longer, due to formation of solid FeOAl2O3 around the liquid FeOAl2O3 inclusions, thereby preventing the diffusion of aluminum into the particles.
Fredriksson, Hasse; Hammar, Örjan
Magnetoelectric response of AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films
NASA Astrophysics Data System (ADS)
The magnetoelectric (ME) composite films composed of piezoelectric layer AlN film and new magnetostrictive layer [(Fe90Co10)78Si12B10 + Terfenol-D] films were successfully prepared by RF magnetron sputtering. The influence of bias magnetic field Hdc on ME response, as well as, the ac magnetic field sensitivity were investigated in detail. The results demonstrated that the respective magnetic properties of (Fe90Co10)78Si12B10 and Terfenol-D films are coupled in this new magnetostrictive layer, resulting in the fact that ME voltage coefficient ?ME reaches the maximum of 78.1 V/cm Oe and 77.5 V/cm Oe at the bias field of 11 Oe and 96 Oe, respectively. Meanwhile, the composite films display ac magnetic field sensitivity of 0.45 nT/?Hz and 0.47 nT/?Hz at Hdc of 11 Oe and 96 Oe, respectively. The results above indicate that the AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films exhibit a promising potential application in diverse range of magnetic field detection.
Tong, Bei; Yang, Xiaofei; Ouyang, Jun; Lin, Gengqi; Zhang, Yue; Chen, Shi
Multiscale modeling of the influence of Fe content in a Al-Si-Cu alloy on the size distribution of intermetallic phases and micropores
NASA Astrophysics Data System (ADS)
A multiscale model was developed to simulate the formation of Fe-rich intermetallics and pores in quaternary Al-Si-Cu-Fe alloys. At the microscale, the multicomponent diffusion equations were solved for multiphase (liquid-solid-gas) materials via a finite difference framework to predict microstructure formation. A fast and robust decentered plate algorithm was developed to simulate the strong anisotropy of the solid/liquid interfacial energy for the Fe-rich intermetallic phase. The growth of porosity was controlled by local pressure drop due to solidification and interactions with surrounding solid phases, in addition to hydrogen diffusion. The microscale model was implemented as a subroutine in a commercial finite element package, producing a coupled multiscale model. This allows the influence of varying casting conditions on the Fe-rich intermetallics, the pores, and their interactions to be predicted. Synchrotron x-ray tomography experiments were performed to validate the model by comparing the three-dimensional morphology and size distribution of Fe-rich intermetallics as a function of Fe content. Large platelike Fe-rich ? intermetallics were successfully simulated by the multiscale model and their influence on pore size distribution in shape castings was predicted as a function of casting conditions.
Wang, Junsheng; Li, Mei; Allison, John; Lee, Peter D.
Multiscale modeling of the influence of Fe content in a Al-Si-Cu alloy on the size distribution of intermetallic phases and micropores
A multiscale model was developed to simulate the formation of Fe-rich intermetallics and pores in quaternary Al-Si-Cu-Fe alloys. At the microscale, the multicomponent diffusion equations were solved for multiphase (liquid-solid-gas) materials via a finite difference framework to predict microstructure formation. A fast and robust decentered plate algorithm was developed to simulate the strong anisotropy of the solid/liquid interfacial energy for the Fe-rich intermetallic phase. The growth of porosity was controlled by local pressure drop due to solidification and interactions with surrounding solid phases, in addition to hydrogen diffusion. The microscale model was implemented as a subroutine in a commercial finite element package, producing a coupled multiscale model. This allows the influence of varying casting conditions on the Fe-rich intermetallics, the pores, and their interactions to be predicted. Synchrotron x-ray tomography experiments were performed to validate the model by comparing the three-dimensional morphology and size distribution of Fe-rich intermetallics as a function of Fe content. Large platelike Fe-rich {beta} intermetallics were successfully simulated by the multiscale model and their influence on pore size distribution in shape castings was predicted as a function of casting conditions.
Wang Junsheng; Lee, Peter D. [Department of Materials, Imperial College London, South Kensington Campus, Prince Consort Road, London SW7 2AZ (United Kingdom); Li Mei; Allison, John [Materials Research and Advanced Engineering Department, Ford Research Laboratory, Dearborn, Michigan 48121-2053 (United States)
Predicting of mechanical properties of Fe–Mn–(Al, Si) TRIP\\/TWIP steels using neural network modeling
In this work, an artificial neural network (ANN) model was established in order to predict the mechanical properties of transformation induced plasticity\\/twinning induced plasticity (TRIP\\/TWIP) steels. The model developed in this study was consider the contents of Mn (15–30wt%), Si (2–4wt%) and Al (2–4wt%) as inputs, while, the total elongation, yield strength and tensile strength are presented as outputs. The
G. Dini; A. Najafizadeh; S. M. Monir-Vaghefi; A. Ebnonnasir
First-principles study of the Hume-Rothery electron concentration rule in Al-Cu-(Fe,Ru)-Si 1/1-cubic approximants
NASA Astrophysics Data System (ADS)
To elucidate the Hume-Rothery electron concentration rule, we determined the self-consistent electronic structures of the Al108Ru24Cu6Si6 and Al108Fe24Cu6Si6 1/1-1/1-1/1 approximants containing 144 atoms in each Pm-3 cubic unit cell using the full-potential linearized augmented plane wave (FLAPW) method [1], now running on massively parallel computer platforms. A significant pseudogap was found around the Fermi level for both alloys in the calculated densities of states, which should contribute to stabilization of the system. The FLAPW wave functions provide a direct observation of the Brillouin zone resonance in the Fermi surface [2]: a Fourier analysis of the wave functions confirms the Hume-Rothery matching rule 2kF=K where the reciprocal lattice vectors K consist of 543, 550, and 710 planes highly degenerate at the N point. Consequently, an effective electron concentration per atom (e/a) was evaluated to be 0.8 for both Ru and Fe in these structures making a sharp contrast with the previously assumed empirical value of -2.7 proposed by Raynor [3]. [1] Wimmer et al., Phys. Rev. B 24, 864 (1981). [2] Asahi et al., Phys. Rev. B 72, 125102 (2005). [3] Raynor, Prog. Metal Phys. 1, 1 (1949).
Asahi, Ryoji; Kontsevoi, O. Y.; Mizutani, U.; Takeuchi, T.; Freeman, A. J.
Melts in the Deep Earth: Calculating the Densities of CaO-FeO-MgO-Al2O3-SiO2 Liquids
NASA Astrophysics Data System (ADS)
We present new equation of state (EOS) measurements for hedenbergite (Hd, CaFeSi2O6) and forsterite (Fo, Mg2SiO4) liquids. These liquid EOS add to the basis set in the CaO-FeO-MgO-Al2O3-SiO2 (CMASF) oxide space at elevated temperatures and pressures; other liquids include: enstatite (En, MgSiO3), anorthite (An, CaAl2Si2O8), diopside (Di, CaMgSi2O6), and fayalite (Fa, Fe2SiO4). The Hd EOS measurement was a multi-technique collaboration using 1-atm double-bob Archimedean, ultrasonic, sink/float, and shock wave techniques. Un-weighted linear fitting of the shock data in shock velocity (US)-particle velocity (up) space defines a pre-heated (1400 °C) Hugoniot US = 2.628(0.024) + 1.54(0.01)up km/s. The slope corresponds to a K' of 5.16(0.04), consistent with piston-cylinder and multi-anvil sink/float experiments. The intercept is fixed at the ultrasonic sound speed (Co) since the unconstrained intercept is within the stated error. This behavior demonstrates consistency across methods and that the liquid is relaxed during shock compression. Shock compression of pre-heated (2000°C) single crystal Fo gives an un-weighted linear Hugoniot of US = 2.674(0.188) + 1.64(0.06)up km/s. The unconstrained Co falls below estimates based on extrapolation in both temperature and composition from two published partial molar sound speed models, 3.195m/s [1] and 3.126 m/s [2]. The shock-derived Co indicates that dC/dT is negative for Fo liquid, contrary to the positive [1] and zero [2] temperature dependences derived over relatively narrow temperature intervals. CMASF liquid isentropes were calculated using five end-members (En, Fo, Fa, An, Di). For modeling crystallization of a fictive magma ocean, we examined two liquids: peridotite [3] (P=.33En+.56Fo+.07Fa+.03An+.007Di) and simplified chondrite [4] (Ch=.62En+.24Fo+.08Fa+.04An+.02Di). Each end-member is defined by a 3rd or 4th order Birch-Murnaghan isentrope, Mie-Grüneisen thermal pressure and a constant heat capacity. The volumes are assumed to ideally mix allowing for interpolation between end-member compositions. Results show the chondrite critical isentrope intersecting its liquidus at the core-mantle boundary with a potential temperature (TP) of 2400 K, whereas the peridotite critical isentrope has a TP of 2800 K and first crystallizes at 85 GPa. An identical calculation fails to recover the Hd isentrope (Hd = Di+0.5Fa-0.5Fo). This failure is likely due to the very different partial molar volumes of FeO in Hd and Fa, which have average Fe2+ coordination states of ~4.5 and ~6, respectively [5]. Consequently the simple ideal model is likely to only support mixing among like-coordinated Fe2+ liquids. We hope to further investigate this hypothesis for linear-mixing by constraining the EOS of An-Hd (50:50), and An-Di-Hd (33:33:33) melts using pre-heated shock wave techniques. [1] Ghiorso & Kress (2004) AJS 304, 679-751.[2] Ai & Lange(2008) JGR 113,B04203.[3] Fiquet et al. (2010) Science 329, 1516-1518.[4]Andrault et al. (2011) EPSL 304, 251-259.[5]Lange et al. (2012) Goldschmidt meeting, abstract.
Thomas, C.; Guo, X.; Agee, C. B.; Asimow, P. D.; Lange, R. A.
Experimental Determination of Phase Relations in SiO2-Al2O3-Fe2O3-MgO at Lower Mantle Conditions: Synthesis Results
NASA Astrophysics Data System (ADS)
We made synthesis experiments in the system SiO2-Al2O3-Fe2O3-MgO (SAFM) using the laser-heated diamond anvil cell at conditions approximating the upper portion of Earth`s lower mantle. Eleven starting compositions spanning five compositional joins were investigated. Starting mixtures are composed of glass, glass+oxide(s), or glass+crystalline materials. Fine Pt black was added to iron-free mixtures for a laser absorber. Seventeen experiments on finely powdered samples were made at pressures of 25-60 GPa and at temperatures of 2000-3000 K. Samples were heated in a double-sided geometry with a diode-pumped YLF laser operating in TEM01 mode. The laser spot was ~ 30 ?m in diameter, and sample areas ~ 70 ?m in diameter were heated by slow and repeated scanning for 15 to 20 minutes. Pressure and temperature quenched samples were analyzed for phase identification using wavelength-dispersive X-ray diffraction at station 12.2.2 of the Advanced Light Source. Multiple spectra spanning the heated regions of the samples were collected using a monochromatic (?=0.62) X-ray beam focused to a spot ~ 30 ?m in diameter. The salient findings are as follows: 1. SAM system: Al2O3 is highly soluble in Mg-perovskite (MPv=MgSiO3), possibly exceeding 50 wt% Al2O3. This shows that coupled substitution of Al3+ on both the six- and eight-coordinated sites is energetically favorable, as predicted in ab initio calculations. 2. Results along MPv-MgAlO2.5 indicate a considerable solution of Al3+ into MgPv via a vacancy forming reaction. 3. SFM system: Fe2O3 has low solubility in MPv, indicating that coupled substitution of 2Fe3+ onto six- and eight-fold sites is generally not energetically favorable. Experiments indicate that Fe3+ enters the six-fold site via an oxygen-vacancy forming reaction. 4. Results within SAFM along the join MPv-FeAlO3 show an extensive region within which MPv, a ferrite-structered Mg(Fex,Al1-x)2O4, and stishovite coexist. Phase relations indicate that as Al3+ is added to the system SFM, coupled substitution of Fe3+ (8-fold) and Al3+ (6-fold) increases over vacancy-forming substitution of Fe3+. Based on a self-consistent set of quaternary phase relations in SAFM, we predict that at conditions of the upper part of the lower mantle (e.g. 25-50 GPa), model mantle peridotite compositions should yield an oxide phase (Mg,Fe)O coexisting with Mg-perovskite dominated by defect substitution mechanisms. This is because in the quaternary system, peridotite composition is confined between the MgO apex and a plane of defect perovskite.
Walter, M.; Tronnes, R.; Caldwell, S.
Iron spin transitions and elastic properties of (Mg,Fe)(Si,Al)O3 perovskite using a newly developed synchrotron Mössbauer source and nuclear inelastic scattering
NASA Astrophysics Data System (ADS)
Comparison of laboratory measurements of elastic wave velocities of mantle minerals with seismic data constitutes one of the foundations upon which knowledge of the Earth's interior is based. In situ measurements are important, because some transitions (for example, spin transitions) are not quenchable, and may influence the elastic properties of iron-containing minerals. Nuclear inelastic scattering (NIS) offers the possibility to determine elastic wave velocities of iron-containing minerals in the laser-heated diamond anvil cell through direct measurement of the partial density of states. Existing NIS data for (Mg,Fe)O are generally consistent with results from other methods, and show the effects of the high spin to low spin transition on elastic properties. In contrast, NIS data collected for (Mg,Fe)(Si,Al)O3 perovskite show anomalously low velocities, and the effect of spin transitions on elastic properties remains controversial. Mössbauer spectroscopy measured in the energy domain remains one of the best methods to identify the nature of spin transitions in (Mg,Fe)(Si,Al)O3 perovskite, but conventional radioactive sources have limited intensity and essentially no possibilities for focusing in a laboratory setting. In order to measure energy domain Mössbauer spectra to at least 100 GPa in the laser-heated diamond anvil cell, we have developed a synchrotron source of Mössbauer radiation with an intensity of around 50,000 photons per second that is focused to a spot of roughly 10 x 10 ?m2. High quality energy domain Mössbauer spectra of samples at 100 GPa can be collected in approximately 10 minutes. Quasi-single crystals of (Mg,Fe)(Si,Al)O3 perovskite characterised using X-ray diffraction provide structural constraints that enable robust fitting of Mössbauer spectra to provide clear evidence of which spin transitions of Fe2+ and Fe3+ occur in the different sites of the perovskite structure. The corresponding NIS data of the highly homogeneous samples enable elastic wave velocity data to be interpreted with respect to the effect of small amounts of impurity phases, as well as provide insight into elastic wave anisotropy. We will report our most recent results, and discuss the implications of our data for modelling of lower mantle compositions and temperatures, as well as the consequences for dynamic mantle processes.
McCammon, C. A.; Potapkin, V.; Chumakov, A. I.; Celse, J. P.; Rüffer, R.; Smirnov, G.; Popov, S. L.; Glazyrin, K.; Kantor, A.; Kantor, I.; Sergueev, I.; Boffa Ballaran, T.; Dubrovinsky, L. S.
Electronic, structural, and magnetic properties of the half-metallic ferromagnetic quaternary Heusler compounds CoFeMnZ (Z=Al, Ga, Si, Ge)
NASA Astrophysics Data System (ADS)
The quaternary intermetallic Heusler compounds CoFeMnZ (Z=Al, Ga, Si, or Ge) with 1:1:1:1 stoichiometry were predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations. The compounds were synthesized using an arc-melting technique and the crystal structures were analyzed using x-ray powder diffraction. The electronic properties were investigated using hard x-ray photoelectron spectroscopy. The low-temperature magnetic moments, as determined from magnetization measurements, follow the Slater-Pauling rule, confirming the proposed high spin polarizations. All compounds have high Curie temperatures, allowing for applications at room temperature and above.
Alijani, Vajiheh; Ouardi, Siham; Fecher, Gerhard H.; Winterlik, Jürgen; Naghavi, S. Shahab; Kozina, Xeniya; Stryganyuk, Gregory; Felser, Claudia; Ikenaga, Eiji; Yamashita, Yoshiyuki; Ueda, Shigenori; Kobayashi, Keisuke
Partitioning behavior of Al in a nanocrystalline Fe{sub 71.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1}Al{sub 2} alloy
The nanocrystalline Fe-Si-B-Nb-Cu alloy, known as FINEMET, is now a well established commercial soft magnetic material exhibiting excellent permeability while maintaining a high saturation magnetization. It is produced by melt-spinning to form a ribbon with an amorphous structure. The purpose of this investigation was to use 3-dimensional atom probe microanalysis to experimentally quantify the local phase chemistries of this nanocomposite microstructure, with particular reference to the partitioning behavior of the Al.
Warren, P.J.; Todd, I.; Davies, H.A.; Cerezo, A.; Gibbs, M.R.J.; Kendall, D.; Major, R.V.
Heterogeneous reactions of volatile organic compounds on oxide particles of the most abundant crustal elements: Surface reactions of acetaldehyde, acetone, and propionaldehyde on SiO2, Al2O3, Fe2O3, TiO2, and CaO [SiO2 Al2O3 Fe2O3 TiO2
The heterogeneous reactivity of volatile organic compounds (VOCs) on oxide particles has been investigated. Oxide particles composed of the most abundant elements present in the Earth's crust were used to identify potentially important reactions of VOCs on mineral dust. In particular, heterogeneous reactions of acetaldehyde, acetone, and propionaldehyde on alpha-Al2O3, alpha-Fe2O3, TiO2, CaO, and SiO2 particle surfaces have been investigated.
P. Li; K. A. Perreau; E. Covington; C. H. Song; G. R. Carmichael; V. H. Grassian
Activities of Fe t O in CaO-Al 2 O 3 SiO 2 Fe t O (<5 pct) slags saturated with liquid iron
The activity coefficients of FetO in CaO-Al2O3 and CaO-Al2O3-SiO2 slags with 0.01 to 5 mass pct FetO were determined at 1873 K from the data obtained in the present and previous slag-metal experiments, using an alumina or\\u000a lime crucible. It was found that the activity coefficients of FetO obeyed a dilute solution law and increased with increasing the content of
Kwang Ro Lee; Hideaki Suito
Measurement of recoil nuclei losses for proton-induced reactions in Al, Si, Mg and Fe at 200 and 500 MeV
NASA Astrophysics Data System (ADS)
The recoil losses of product nuclei in proton-induced reactions at 200 and 500 MeV in Al, Si, Mg and Fe targets were measured using carbon catcher foils or stacks of Mylar foils. In all cases, the recoil losses were less than 1% for the target thicknesses used and so in the ongoing systematic study to measure cross sections for proton- and neutron-induced reactions, these losses are not important. For Fe targets irradiated at 200 MeV, the recoil losses in the forward direction for several product nuclei measured in both a carbon catcher foil and a Mylar stack were in good agreement. From the recoil losses, the mean forward recoil ranges for several product nuclei were calculated.
Sisterson, J. M.
Full potential results on the magneto-optical properties of the Heusler compounds Co(2)FeX (X = Al, Ga, Si and Ge).
We have calculated the magneto-optical (MO) properties of Co(2)FeX (X = Al, Ga, Si and Ge) Heusler compounds using the full potential linearized augmented plane wave (FPLAPW) method as implemented in the WIEN2K code using the local spin density approximation (LSDA) and also by using the generalized gradient approximation (GGA) for the electronic exchange and correlation. In all the compounds, Kerr rotation ?(K) has a strong minimum near 2 eV, the value of |?(K)| corresponding to this minimum being almost as large as in pure Co-Fe compounds. The calculated MO spectra help to identify the features of the experimental spectra. A comparison of the results shows that the Kerr spectrum is quite similar from both LSDA and GGA but the latter gives better agreement with experiment. Moreover, we find that inclusion of correlation effects using GGA+U removes the discrepancy in magnetic moment of Co(2)FeX (X = Si, Ge) though it has an insignificant effect on the Kerr spectra. PMID:21825501
Kumar, Manish; Nautiyal, Tashi; Auluck, Sushil
Planar Flow Casting of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 Ribbons
NASA Astrophysics Data System (ADS)
In this study, the planar flow casting (PFC) technique for producing wide amorphous ribbons of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 alloy is investigated. Various ribbons of the mentioned alloy were produced through applying different values of wheel speed and ejection pressure. In addition, effects of wheel speed (13, 23, and 33 m/s) on the structure, degree of amorphicity, and surface quality of the ribbons were examined. The results showed that the trends of thickness variation with increasing wheel speed and ejection pressure for Fe71Si13.5B9Nb3Cu1Al1.5Ge1 ribbons are in good agreement with what the Bernoulli equation in fluid dynamics predicts for the PFC process. Further, based on x-ray diffraction and differential scanning calorimeter results, it was shown that the degree of amorphicity increases by increasing the wheel speed. Besides, surface roughness measurements and scanning electron microscope micrographs of the ribbons revealed that the surface quality of the prepared ribbons improved by increasing the wheel speed.
Sohrabi, S.; Arabi, H.; Beitollahi, A.; Gholamipour, R.
Interactions between iron, manganese, and the Al-Si eutectic in hypoeutectic Al-Si alloys
NASA Astrophysics Data System (ADS)
Sand-cast plates were used to determine the effect of iron and manganese concentrations on porosity levels in Al-9 pct Si-0.5 pct Mg alloys. Iron increased porosity levels. Manganese additions increased porosity levels in alloys with 0.1 pct Fe, but reduced porosity in alloys with 0.6 and 1 pct Fe. Thermal analysis and quenching were undertaken to determine the effect of iron and managanese on the solidification of the Al-Si eutectic. At high iron levels, the presence of large ?-Al5FeSi was found to reduce the number of eutectic nucleation events and increase the eutectic grain size. The preferential formation of ?-Al15Mn3Si2 upon addition of manganese reversed these effects. It is proposed that this interaction is due to ?-Al5FeSi and the Al-Si eutectic having common nuclei. Porosity levels are proposed to be controlled by the eutectic grain size and the size of the iron-bearing intermetallic particles rather than the specific intermetallic phase that forms.
Dinnis, C. M.; Taylor, J. A.; Dahle, A. K.
The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge
NASA Astrophysics Data System (ADS)
Phase transition from perovskite (Pv) to Post-Pv (PPv) phase in MgSiO3 has been studied by many groups since its discovery in 2004 (1,2) and the different studies find similar transition pressures. The effect of Al and Fe on the phase transition remains more controversial. The most recent studies suggest an increase of the transition pressure with increasing Fe-content (3,4), but other experimental work (5) as well as ab-initio calculations (6) show the opposite effect. The effect of Al was reported to increase slightly the pressure transition to the CaIrO3 form (4,7), but its influence on the Fe3+ content in the PPv phase has not been documented yet. By means of in situ study of the Fe K-edge fine structures (XANES), we investigated the phase relations between Pv and PPv phases for three different Al-(Mg,Fe)SiO3 compositions. For this, we synthesized various Pv and PPv mixtures using laser-heated diamond anvil cell (DAC) for pressures between 60 and 170 GPa. The sample's mineralogy, i.e. the Pv and PPv phase fractions, was determined using in-situ X-ray diffraction at the ID27 beamline of the ESRF (8,9). Then, we probed the Fe speciation, i.e. the Fe concentration in each phases, in-situ in the DAC using the µ-XANES mapping technique available at the ID24 beamline (10,11). Both pieces of information were combined to retrieve the Fe partitioning coefficient between the two high-pressure phases. Our results show that Fe partitions strongly into the PPv phase, which implies a very large binary loop of coexistence of the two phases. Thus, at the core-mantle boundary pressure (135 GPa), the Pv and PPv phase always coexist for all geophysically relevant Al-(Mg,Fe)SiO3 compositions, and the Fe-content in the PPv-phase is only a few percent. References: 1. M. Murakami, K. Hirose, K. Kawamura, N. Sata, Y. Ohishi, Science 304, 855 (2004). 2. A. R. Oganov, S. Ono, Nature 430, 445 (2004). 3. S. Tateno, K. Hirose, N. Sata, Y. Ohishi, Phys. Earth Planet. Inter. 160, 319 (2007). 4. D. Nishio-Hamane, T. Nagai, K. Fujino, Y. Seto, N. Takafuji, Geophys. Res. Lett. 32, L16306 (2005). 5. W. L. Mao et al., PNAS 101, 15867 (2004). 6. J. P. Brodholt, A. R. Oganov, personal communication. 7. S. Ono, A. R. Oganov, T. Koyama, H. Shimizu, Earth Planet. Sci. 246, 326 (2006). 8. N. Guignot, D. Andrault, G. Morard, M. Mezouar, Earth Planet. Sci. 256, 162 (2007). 9. E. Schultz et al., High Press. Res. 25, 71 (2005). 10. S. Pascarelli, O. Mathon, M. Muñoz, T. Mairs, J. Susini, J. Synch. Rad. 13, 351 (2006). 11. M. Muñoz et al., Geochemistry Geophysics Geosystems 7, Q11020 (2006).
Andrault, D.; Munoz, M.; Bolfan-Casanova, N.; Guignot, N.; Perrillat, J.; Aquilanti, G.; Pascarelli, S.
Spin state of iron and elastic properties of (MgFe)(SiAl)O3 under conditions of the lower mantle
NASA Astrophysics Data System (ADS)
Iron is incorporated into crystal structures of the dominant lower mantle phases, namely, magnesium silicate perovskite (Pv) and ferropericlase (Fp). There is no doubt that iron is the most abundant transition element of the lower mantle. Depending on conditions imposed by the latter, charge distribution between different electronic orbitals of iron may change, giving rise to spin state transitions (SST) which, in turn, may modify bulk elastic and transport properties of the material. Critical conditions promoting SST vary depending on iron cation charge and crystallographic environment. In the case of Pv, it was shown that Fe2+ will occupy exclusively the distorted dodecahedral (A) site, while Fe3+ can substitute in both the A and the B (octahedral) sites. However, the problem becomes more complicated if we consider Fe/Al coupled substitution in Pv and realistic compositions of the lower mantle. Although SST in Pv is a current and highly debated topic, there is clearly a lack of experimental data, and the literature shows strong controversies between theoretical calculations and experiment. The problem of iron SST in Pv is one of the most challenging and important for our understanding of mantle processes and dynamics. We conducted a single crystal diffraction experiment on Mg0.6Fe0.4Si0.63Al0.37O3 Pv at the ID09 beamline, ESRF, Grenoble. Comprehensive characterization of this sample synthesized in a multianvil apparatus revealed that almost all iron in this material is ferric and occupies exclusively the A site (Fe3+A). We studied the combined effect of compression and temperature on the crystal structure and elastic properties of the material, and we observed that (a) below 77 GPa, 1800K there is no SST for Fe3+A and (b) high pressure-high temperature treatment has no effect on Fe/Al cation distribution between different crystallographic sites. These observations are in good agreement with recent theoretical work. Based on a thermal equation of state derived from our experiments and data from the literature, we present a unified model capable of predicting elastic properties for a wide range of realistic lower mantle Pv compositions. Additionally we discuss the effect of iron spin state and iron oxidation state on one of the most important variables - bulk sound velocity of Pv at conditions of the lower mantle.
Glazyrin, K.; Boffa Ballaran, T.; Frost, D. J.; McCammon, C. A.; Kantor, A.; Merlini, M.; Hanfland, M.; Dubrovinsky, L. S.
AlN/Fe/AlN nanostructures for magnetooptic magnetometry
NASA Astrophysics Data System (ADS)
AlN/Fe/AlN/Cu nanostructures with ultrathin Fe grown by sputtering on Si substrates are evaluated as probes for magnetooptical (MO) mapping of weak currents. They are considered for a laser wavelength of ? = 410 nm (3.02 eV) and operate at oblique light incidence angles, ?(0), to enable detection of both in-plane and out-of-plane magnetization. Their performance is evaluated in terms of MO reflected wave electric field amplitudes. The maximal MO amplitudes in AlN/Fe/AlN/Cu are achieved by a proper choice of layer thicknesses. The nanostructures were characterized by MO polar Kerr effect at ?(0) ? 5° and longitudinal Kerr effect spectra (?(0) = 45°) at photon energies between 1 and 5 eV. The nominal profiles were refined using a model-based analysis of the spectra. Closed form analytical expressions are provided, which are useful in the search for maximal MO amplitudes.
Lišková-Jakubisová, E.; VišÅovský, Š.; Široký, P.; Hrabovský, D.; Pištora, J.; Harward, I.; Celinski, Z.
On the Production of He, Ne, and AR Isotopes from Mg, Al, Si, Ca, Fe, and NI in an Artificially Irradiated Meteoroid
NASA Astrophysics Data System (ADS)
The production of He, Ne, and Ar isotopes from their main target elements was investigated in an experiment (1) by irradiating a 50-cm-diameter gabbro sphere isotropically with 1.6 GeV protons. The model meteoroid contained, among a large number of other targets, pure element foils of Mg, Al, Si, Fe, and Ni at 10 different depths and wollastonite targets at 3 different depths in central bores. After the irradiation, radionuclide production in these targets was measured by gamma spectrometry. Stable He, Ne, and Ar isotopes were measured in statically operated mass spectrometers. Here, we report the results for stable He, Ne, and Ar isotopes and for ^22Na. The production depth profiles vary widely, ranging from profiles with near-surface production 15% higher than in the center (^22Na from Fe) to such profiles with production in the center 45% higher than near the surface (^20Ne from Mg). The isotope ratios ^3He/^4He and ^3He/^21Ne in Mg, Al, Si and ^22Ne/^21Ne in Mg all decrease significantly with increasing shielding. The production rates of He, Ne, and ^22Na from Mg, Al, and Si in the 1600-MeV simulation experiment are 1.5 to 3 times higher than in the model meteoroid of similar size but irradiated earlier with 600 MeV protons (2). This increase is attributed to the increase of the production of secondary neutrons with primary energies rising from 600 to 1600 MeV. This effect also causes the depth dependences of isotope ratios observed in the 1600-MeV simulation that was not seen in the 600-MeV experiment. Model calculations of the production of He, Ne, and Ar isotopes and of ^22Na were performed for the artificial meteorites of the 600- and 1600 MeV-exposures as well as for real meteoroids. Production rates were calculated from depth-dependent p- and n- spectra, which were derived by Monte Carlo techniques using the HERMES code system (3), and from cross sections for the relevant nuclear reactions as described earlier (4). The cross section database for p-induced reactions was extended by new data. Particularly, new thin target cross sections for the production of He and Ne isotopes from Mg, Al, Si, Fe, and Ni at energies of 800, 1200, 1600, and 2600 MeV measured by our group were included. For the production of He isotopes by n- and p-induced reactions identical cross sections were assumed. The new calculations for real meteorites confirm the recently published production rates of ^21Ne in stony meteoroids (4) and newly also describe the depth profiles of ^22Ne/^21Ne ratios. Comparison of production in the model meteoroid and real meteoroids shows that the 1600-MeV irradiation simulates the cosmic exposure to galactic protons within about 20%. The systematic deviations are attributed to differences between the monoenergetic irradiation and the exposure to the GCR spectrum and to the resulting differences between the secondary particle fields. Acknowledgement: This work was supported by the Deutsche Forschungsgemeinschaft and by the Swiss National Science Foundation. References: (1) Michel R. et al. (1991) Meteoritics (abstract) 26, 372a. (3) Cloth P. et al. (1988) Juel-2203. (2) Michel R. et al. (1989) Nucl. Instr. Meth. Phys. Res. B42, 76-100. (4) Michel R. et al. (1991) Meteoritics 26, 221-242.
Wieler, R.; Signet, P.; Rosel, R.; Herpers, U.; Lupke, M.; Lange, H.-J.; Michel, R.
Effect of Fe 2O 3 concentration on the structure of the SiO 2-Na 2O-Al 2O 3-B 2O 3 glass system
NASA Astrophysics Data System (ADS)
The structural properties of the glass matrix 40SiO 2·30Na 2O·1Al 2O 3·(29 - x)B 2O 3· xFe 2O 3 (mol%), 0.0 ? x ? 29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe 3O 4 crystal formation for Fe 2O 3 concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe 2O 3 concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe 2O 3 concentration.
Dantas, Noelio O.; Ayta, Walter E. F.; Silva, Anielle C. A.; Cano, Nilo F.; Silva, Sebastião W.; Morais, Paulo C.
Effect of Mg and Sr additions on the formation of intermetallics in Al-6 wt pct Si-3.5 wt pct Cu-(0.45) to (0.8) wt pct Fe 319-type alloys
Al-Si alloys are materials that have been developed over the years to meet the increasing demands of the automotive industry for smaller, lighter-weight, high-performance components. An important alloy in this respect is the 319 alloy, wherein silicon and copper are the main alloying elements, and magnesium is often added in automotive versions of the alloy for strengthening purposes. the mechanical properties are also ameliorated by modifying the eutectic silicon structure (strontium being commonly employed) and by reducing the harmful effect of the {beta}-Al{sub 5}FeSi iron intermetallic present in the cast structure. Magnesium is also found to refine the silicon structure. The present study was undertaken to investigate the individual and combined roles of Mg and Sr on the morphologies of Si, Mg{sub 2}Si, and the iron and copper intermetallics likely to form during the solidification of 319-type alloys at very slow (close to equilibrium) cooling rates. The results show that magnesium leads to the precipitation of Al{sub 8}Mg{sub 3}FeSi{sub 6}, Mg{sub 2}Si, and Al{sub 5}Mg{sub 8}Cu{sub 2}Si{sub 6} intermetallics. With a strontium addition, dissolution of a large proportion of the needle-like {beta}-Al{sub 5}FeSi intermetallic in the aluminum matrix takes place; no transformation of this phase into any other intermetallics (including the Al{sub 15}(Fe,Mn){sub 3}Si{sub 2} phase) is observed. When both Mg and Sr are added, the diminution of the {beta}-Al{sub 5}FeSi phase is enhanced, through both its dissolution in the aluminum matrix as well as its transformation into Al{sub 8}Mg{sub 3}FeSi{sub 6}. The reactions and phases obtained have been analyzed using thermal analysis, optical microscopy, image analysis, and electron microprobe analysis (EMPA) coupled with energy-dispersive X-ray (EDX) analysis.
Samuel, F.H.; Ouellet, P.; Samuel, A.M. [Univ. of Quebec, Chicoutimi, Quebec (Canada); Doty, H.W. [General Motors Corp., Milford, NH (United States)
Effect of high temperature and high strain rate on the dynamic mechanical properties of Fe-30Mn-3Si-4Al TWIP steel
NASA Astrophysics Data System (ADS)
The dynamic mechanical properties of Fe-30Mn-3Si-4Al twinning induced plasticity (TWIP) steel were studied by the split-Hopkinson pressure bar (SHPB) at temperatures of 298-1073 K and strain rates of 700, 2500, and 5000 s-1. The TWIP steel indicates strain rate hardening effect between 700 and 2500 s-1, but it shows strain rate softening effect between 2500 and 5000 s-1. In addition, the strain rate softening effect enhances with an increase in deformation temperature. After deformation, the microstructures were studied by optical microscopy (OM). It is shown that the deformation bands become more convergence, a part of which become interwoven with an increase in strain rate, and the dynamic recovery and recrystallization are enhanced with an increase in both temperature and strain rate.
Xiong, Zhi-ping; Ren, Xue-ping; Bao, Wei-ping; Shu, Jian; Li, Shu-xia; Qu, Hai-tao
Modelling equilibrium and fractional crystallization in the system MgO-FeO-CaO-Al2O3-SiO2
NASA Technical Reports Server (NTRS)
A mathematical modelling technique for use in petrogenesis calculations in the system MgO-FeO-CaO-Al2O3-SiO2 is reported. Semiempirical phase boundary and elemental distribution information was combined with mass balance to compute approximate equilibrium crystallization paths for arbitrary system compositions. The calculation is applicable to a range of system compositions and fractionation calculations are possible. The goal of the calculation is the computation of the composition and quantity of each phase present as a function of the degree of solidification. The degree of solidification is parameterized by the heat released by the solidifying phases. The mathematical requirement for the solution of this problem is: (1) An equation constraining the composition of the magma for each solid phase in equilibrium with the liquidus phase, and (2) an equation for each solid phase and each component giving the distribution of that element between that phase and the magma.
Herbert, F.
Phase Equilibria Studies of Cu-O-Si Systems in Equilibrium with Air and Metallic Copper and Cu-Me-O-Si Systems (Me = Ca, Mg, Al, and Fe) in Equilibrium with Metallic Copper
NASA Astrophysics Data System (ADS)
The pseudo-binary phase diagrams in the Cu-O-Si system in equilibrium with air and metallic copper have been constructed. Equilibration at high temperature in an appropriate containment material, followed by rapid quenching and measurement of phase compositions using an electron probe x-ray microanalysis (EPMA) technique, was carried out to obtain the phase equilibria data. The investigation has been extended to characterize the effects of CaO, MgO, Al2O3, and "Fe2O3" on the liquidus isotherms of tridymite in equilibrium with metallic copper at temperatures of 1473 K and 1573 K (1200 °C and 1300 °C).
Hidayat, Taufiq; Henao, Hector M.; Hayes, Peter C.; Jak, Evgueni
Epitaxial films of Heusler compound Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} with high crystalline quality grown by off-axis sputtering
Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} films with a surface roughness of 0.12 nm have been grown epitaxially on lattice-matched MgAl{sub 2}O{sub 4} (001) substrates by off-axis sputtering. X-ray diffraction shows pronounced Laue oscillations, rocking curves as narrow as 0.0043°, and clear Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (111) peaks indicating L2{sub 1} ordering. Magnetic characterizations show a clear magnetocrystalline anisotropy comprising cubic and epitaxy-induced uniaxial terms. Nuclear magnetic resonance measurements reveal L2{sub 1} order of 81% in the Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} films. Magnetotransport measurements show a distinct separation of anisotropic magnetoresistance and ordinary magnetoresistance. These results demonstrate the state-of-the-art crystalline quality and magnetic uniformity of the Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} films.
Peters, B.; Hageman, Stephen J.; Yang, F. Y. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Alfonsov, A.; Blum, C. G. F. [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany)] [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany); Woodward, P. M. [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210 (United States); Wurmehl, S.; Büchner, B. [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany) [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany); Institute for Solid State Physics, Technische Universität Dresden, D-01062 Dresden (Germany)
Precipitation hardening processes in an Al–0.4%Mg–1.3%Si–0.25%Fe aluminum alloy
Aluminum alloys containing Mg and Si as the major solutes are strengthened by precipitation of the metastable precursors of the equilibrium ? (Mg2Si) phase in one or more sequences. There are several metastable particles that can form during ageing, but the strengthening potential of these particles relative to one another is not extensively studied. In this paper, the precipitation and
A. K. Gupta; D. J. Lloyd; S. A. Court
Habit Modification of SiO2 Doped Y3Al5O12, Y3Fe5O12, and Y3Ga5O12 Garnets.
National Technical Information Service (NTIS)
The habits of single crystals of the synthetic garnets, when grown from a SiO2 contaminated PbO-PbF2 flux, are dependent on the concentration of SiO2 in the melt. Y3Ga5O12 and Y3Fe5O12 crystals have a pure (211) habit when grown from an undoped melt. The ...
A. B. Chase J. A. Osmer
Interactions between iron, manganese, and the Al-Si eutectic in hypoeutectic Al-Si alloys
Sand-cast plates were used to determine the effect of iron and manganese concentrations on porosity levels in Al-9 pct Si-0.5\\u000a pct Mg alloys. Iron increased porosity levels. Manganese additions increased porosity levels in alloys with 0.1 pct Fe, but\\u000a reduced porosity in alloys with 0.6 and 1 pct Fe. Thermal analysis and quenching were undertaken to determine the effect of
C. M. Dinnis; J. A. Taylor; A. K. Dahle
Heterogeneous nucleation of solidification of Si in Al-Si and Al-Si-P alloys
Heterogeneous nucleation of solidification in melt spun Al-Si and Al-Si-P has been studied using differential scanning calorimetry, and transmission, scanning transmission and high resolution electron microscopies. The microstructures of the heat treated melt spun alloys all consist of an Al matrix, Al-Si eutectic distributed along the Al grain boundaries, and Si embedded in the Al matrix. The Si microstructure depends on the level of P: coarse faceted Si particles are nucleated by AlP particles in Al-Si containing 2 ppm P and Al-Si-P containing 35 ppm P whereas eutectic droplets of fine Si particles are nucleated by the surrounding Al matrix at a high undercooling in Al-Si containing 0.25 ppm P. The Si nucleation onset temperature remains approximately constant while the peak and end temperatures both decrease with increasing cooling rate, in agreement with classical nucleation theory. Kinetic analysis, using the spherical cap model gives contact angles of 10{degree}, 43{degree} and 10{degree} for Si nucleation in low and high purity Al-Si and Al-Si-P respectively.
Ho, C.R.; Cantor, B. [Oxford Univ. (United Kingdom)] [Oxford Univ. (United Kingdom)
Study by Means of the Mass Spectrometry of Volatile Species in the Oxidation of Cr, Cr 2 O 3 , Al, Al 2 O 3 , Si, SiO 2 , Fe and Ferritic\\/Martensitic Steel Samples at 923 K in Ar+(10 to 80%)H 2 O Vapor Atmosphere for New-Materials Design
Mass spectrometry was used to study in-situ the role of volatile species in the oxidation of reference materials Cr, Cr2O3, Al, Al2O3, Si, SiO2, Fe and ferritic\\/martensitic steels (P91 and P92) at high temperatures. All samples were heated to 650°C at 1 atm in a mixture of Ar with 10–80% range H2O vapor. Oxidation times varied between 100 and 200 h. Cr(g),
F. J. Pérez-Trujillo; S. I. Castañeda
Solubility of iron among plagioclase, clinopyroxene and silicate liquid in the system CaO-MgO-Al/sub 2/O/sub 3/ - SiO/sub 2/-Fe-O
The 1-atm liquidus of the system diopside-anorthite + 10wt% ferric iron is lower (approx. 30/sup 0/C) for end-member compositions but the temperature and projected (Fe-free) composition of the minimum melt are unchanged. The effect of fO/sub 2/ on the liquidus curve is minimal. The major element compositions, the structural state of iron and the ferrous/ferric ratio of existing crystal-liquid pairs have been determined using electron microprobe analyses and /sup 57/Fe Mossbauer spectroscopy. For anorthite-liquid pairs, the partition coefficient, D(Fe) (equal to (Fe in xtal)/(Fe in liquid)) decreases with increasing temperature and with increasing anorthite/diopside ratio, at fixed fO/sub 2/. The effect of bulk composition on D(Fe) predominates over the relatively weak temperature dependence (Longhi et al. 1976). Significantly, at fixed temperature and anorthite/diopside ratio, D(Fe) decreases linearly with fO/sub 2/ from 0.25 (log fO/sub 2/=-0.68) to 0.05 (log fO/sub 2/=-6.0). The increase in D(Fe) with increasing fO/sub 2/ is accompanied by an increase in the ferric iron content of the feldspar lattice. The mechanisms for incorporation of iron in synthetic anorthite are Fe(3+)-Al under oxidizing conditions and Fe(2+), Si-2Al under reducing conditions. The use of D(Fe) as an oxygen barometer is considered. D(Fe) for the system diopside-Fe/sub 2/O/sub 3/ is not strongly fO/sub 2/-dependent at constant temperature. The incorporation of iron in liquidus pyroxene is via the Fe(2+)-Ca substitution. Ferric iron acts as an inert diluent in these melts. Tschermak's substitution is discussed for igneous, ferric-bearing clinopyroxenes.
Virgo, D.; Mysen, B.O.
Perrierite-(La), (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8, a new mineral species from the Eifel volcanic district, Germany
NASA Astrophysics Data System (ADS)
Non-metamict perrierite-(La) discovered in the Dellen pumice quarry, near Mendig, in the Eifel volcanic district, Rheinland-Pfalz, Germany has been approved as a new mineral species (IMA no. 2010-089). The mineral was found in the late assemblage of sanidine, phlogopite, pyrophanite, zirconolite, members of the jacobsite-magnetite series, fluorcalciopyrochlore, and zircon. Perrierite-(La) occurs as isolated prismatic crystals up to 0.5 × 1 mm in size within cavities in sanidinite. The new mineral is black with brown streak; it is brittle, with the Mohs hardness of 6 and distinct cleavage parallel to (001). The calculated density is 4.791 g/cm3. The IR spectrum does not contain absorption bands that correspond to H2O and OH groups. Perrierite-(La) is biaxial (-), ? = 1.94(1), ? = 2.020(15), ? = 2.040(15), 2 V meas = 50(10)°, 2 V calc = 51°. The chemical composition (electron microprobe, average of seven point analyses, the Fe2+/Fe3+ ratio determined from the X-ray structural data, wt %) is as follows: 3.26 CaO, 22.92 La2O3, 19.64 Ce2O3, 0.83 Pr2O2, 2.09 Nd2O3, 0.25 MgO, 2.25 MnO, 3.16 FeO, 5.28 Fe2O3, 2.59 Al2O3, 16.13 TiO2, 0.75 Nb2O5, and 20.06 SiO2, total is 99.21. The empirical formula is (La1.70Ce1.45Nd0.15Pr0.06Ca0.70)?4.06(Fe{0.53/2+}Mn0.38Mg0.08)?0.99(Ti2.44Fe{0.80/3+}Al0.62Nb0.07)?3.93Si4.04O22. The simplified formula is (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8. The crystal structure was determined by a single crystal. Perrierite-(La) is monoclinic, space group P21/ a, and the unit-cell dimensions are as follows: a =13.668(1), b = 5.6601(6), c = 11.743(1) Å, ? = 113.64(1)°; V = 832.2(2) Å3, Z = 2. The strong reflections in the X-ray powder diffraction pattern are [ d, Å ( I, %) ( hkl)]: 5.19 (40) (110), 3.53 (40) (overline 3 11), 2.96 (100) (overline 3 13, 311), 2.80 (50) (020), 2.14 (50) (overline 4 22, overline 3 15, 313), 1.947 (50) (024, 223), 1.657 (40) (overline 4 07, overline 4 33, 331). The holotype specimen of perrierite-(La) is deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, with the registration number 4059/1.
Chukanov, N. V.; Blass, G.; Pekov, I. V.; Belakovskiy, D. I.; Van, K. V.; Rastsvetaeva, R. K.; Aksenov, S. M.
Boronizing of iron aluminide Fe 72Al 28
Boronizing of Fe72Al28 was carried out in a slurry salt bath composed of borax and SiC at temperatures between 900 and 1050°C for different durations starting from 3h up to 15h. The microstructures and microhardness of boride layers and intermetallic matrix were analysed. Samples boronized had Fe2B phase or Fe2B plus FeB phases depending on the process temperatures and times.
?. Çelikyurek; B. Baksan; O. Torun; R. Gürler
Structure and transport properties of current-perpendicular-to-plane spin valves using Co2FeAl0.5Si0.5 and Co2MnSi Heusler alloy electrodes
NASA Astrophysics Data System (ADS)
We report the structure and transport properties of current-perpendicular-to-plane spin valves (CPP SVs) with Co2FeAl0.5Si0.5 (CFAS) or Co2MnSi (CMS) Heusler alloy magnetic layers and an Ag or Cu spacer layer. A multilayer stack of sub/Cr/Ag/Heusler/(Ag or Cu)/ Heusler/Co75Fe25/Ir22Mn78/Ru was deposited on a MgO(001) single crystalline substrate by magnetron sputtering. Transmission electron microscopy observations showed epitaxial growth from the substrate to the top Heusler layer. The CPP SV with a CFAS/Ag/CFAS trilayer showed relatively large magnetoresistance (MR) ratios of 12% at room temperature and 31% at 12 K, with monotonous temperature dependence. However, the MR values of the SV with the CMS/Ag/CMS trilayer showed a different temperature dependence with a maximum value of 22% at 100 K. This might be related to the 90° couplings between the two CMS layers.
Furubayashi, T.; Kodama, K.; Nakatani, T. M.; Sukegawa, H.; Takahashi, Y. K.; Inomata, K.; Hono, K.
Simulation of a directional solidification of a binary Al7wt%Si and a ternary alloy Al7wt%Si1wt%Fe under the action of a rotating magnetic field
We propose an approach for the solidification of metallic alloys taking into account the turbulence in the liquid phase. For modeling of the turbulent flow a k-? model is used. This model is applied for solidification of AlSi-based alloys under the action of rotating electromagnetic field of intensity up to 65mT. Two cases have been considered, namely solidification of a
O Budenkova; F Baltaretu; J Kovács; A Roósz; A Rónaföldi; A-M Bianchi; Y Fautrelle
Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 glass matrix
NASA Astrophysics Data System (ADS)
Samples of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 (mol%), with 0.0 ? x ? 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe3+ ion complexes (g = 4.27 and g = 6.4) and Fe3+-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe3+-based clusters built in from two sources of isolated ions, namely Fe2+ and Fe3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed 5Eg-5T2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe2+ and Fe3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO4 complex resulting from replacing silicon in non-bridging oxygen (SiO3O-) sites whereas ferric ions are incorporated as FeO4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO4).
Dantas, Noelio O.; Ayta, Walter E. F.; Silva, Anielle C. A.; Cano, Nilo F.; Rodriguez, Anselmo F. R.; Oliveira, Aderbal C.; Garg, Vijayendra K.; Morais, Paulo C.
Compatibility of Fe-40Al with various fibers
NASA Technical Reports Server (NTRS)
Chemical reaction can occur at the fiber/matrix interface of intermetallic matrix composites, leading to a degradation of mechanical properties. Fe-40Al matrix composites were fabricated using SiC, B, W, Mo-base, and Al2O3 fibers. Composite samples were heat treated up to 1500 K to study the reaction kinetics, and reaction rates were determined from reaction zone thickness measurements. The Al2O3 and W fibers were found to be compatible with the Fe-40Al matrix, while the Mo-based fibers reacted moderately and the B and SiC fibers reacted severely. Experimental results are compared to theoretical thermodynamic predictions.
Draper, S. L.; Gaydosh, D. J.; Nathal, M. V.; Misra, A. K.
Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si
NASA Technical Reports Server (NTRS)
The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.
Kennedy, J. R.; Gilman, P. S.; Zedalis, M. S.; Skinner, D. J.; Peltier, J. M.
Growth and characterization of high crystalline quality Co2FeAlxSi1-x Heusler alloy films on MgAl2O4(001) substrates
NASA Astrophysics Data System (ADS)
A number of Heusler alloys have been predicted to be half-metallic and are thus ideal candidates for use in spintronics. Co2FeAlxSi1-x has been predicted and shown to have some of the highest Tc, saturation magnetization and lowest magnetic damping constant among Heusler half-metals. Here we outline the growth and characterization of the highest crystalline quality epitaxial Heusler films using a novel off-axis UHV sputtering technique. We grow these films onto a closely lattice matched MgAl2O4(001) substrate, without the need for a Cr-buffer layer or post annealing, as has been done previously. This eliminates the diffusion of Cr across the interface, thus improving the purity and crystallinity of the films at the interface. X-ray diffraction results demonstrate epitaxial films with distinct Laue oscillations and rocking curves of FWHM as low as 0.0035^o, which demonstrates the highest crystalline quality for Heusler films reported to date. Magnetic measurements show highly square hysteresis loops with a remanence of 95-98%, near ideal saturation magnetization, very small coercivities - between 3-8 Oe, pronounced magnetocrystalline anisotropy.
Peters, Brian; Blum, Christian; Woodward, Patrick; Wurmehl, Sabine; Yang, Fengyuan
Formation of ?-FeSi 2 by excimer laser irradiation of 57Fe/Si bilayers
NASA Astrophysics Data System (ADS)
Pulsed laser annealing has been applied on 57Fe/Si(1 0 0) layers in order to study the formation of iron silicides after irradiation with a XeCl excimer laser. The 57Fe layers were produced by pulsed laser deposition. The number of pulses and the fluence were varied. FeSi, ?-FeSi 2 and metastable ?-FeSi 2 phases have been observed after irradiation. Subsequent thermal annealing leads to the presence of a pure ?-FeSi 2 surface layer. Rutherford backscattering spectrometry and conversion electron Mössbauer spectroscopy characterized the irradiated layers.
Wagner, Steffen; Carpene, Ettore; Schaaf, Peter; Weisheit, Martin
Discovery of Ahrensite ?-Fe2SiO4 and Tissintite (Ca,Na,[])AlSi2O6, Two New Shock-induced Minerals from the Tissint Martian Meteorite: a Nanomineralogy Investigation
NASA Astrophysics Data System (ADS)
The recent Martian meteorite fall, Tissint, is a fresh olivine-phyric shergottite, with strong shock features. During our nano-mineralogy investigation of the Tissint meteorite with a combined analytical scanning electron microscope and synchrotron diffraction approach, two new shock-induced minerals have been discovered; these provide new insights into understanding shock conditions and impact processes on Mars. Ahrensite (IMA 2013-028), the Fe-analogue (?-Fe2SiO4) of ringwoodite, is a new high-pressure mineral identified in Tissint. Both ahrensite and ringwoodite occur in Tissint as fine-grained polycrystalline aggregates in the rims of olivines around some shock-melt pockets. The morphology and texture of these silicate-spinels suggest formation by a solid-state transformation from Fe-rich olivine. Associated with the ahrensite and ringwoodite, inside melt pockets, often resides a thin layer of vitrified silicate-perovskite and magnesio-wüstite or wüstite. Such transitions represent a unique pressure and temperature gradient. Tissintite (IMA 2013-027), (Ca,Na,[])AlSi2O6 with the C2/c clinopyroxene structure, is a new jadeite-like mineral in Tissint. It appears as fine-grained aggregates within plagioclase glass, inside many shock-melt pockets. Both ahrensite and tissintite are high-pressure minerals formed by shock during the impact event(s) on Mars that excavated and ejected the rock off Mars. We will discuss the path of structure analysis for both new-mineral cases. Such novel methodology be utilized for many cases of mineralogical phase identification or structure analysis; this demonstrates how nano-mineralogy can be addressed and how it may play a unique role in meteorite and Mars rock research, in general.
Ma, C.; Tschauner, O. D.; Liu, Y.; Sinogeikin, S. V.; Zhuravlev, K. K.; Prakapenka, V.; Dera, P. K.; Taylor, L. A.
Effect of Sulfur on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-S System in Equilibrium with Metallic Iron
NASA Astrophysics Data System (ADS)
The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-S system have been determined experimentally in equilibrium with metallic iron. A pseudoternary section of the form ZnO-"FeO"-(Al2O3+CaO+SiO2) for CaO/SiO2 = 0.71 (weight), (CaO+SiO2)/Al2O3 = 5.0 (weight), and fixed 2.0 wt pct S concentration has been constructed. It was found that the addition of 2.0 wt pct S to the liquid extends the spinel primary phase field significantly and decreases the size of the wustite primary phase field. The liquidus temperature in the wustite primary phase field is decreased by approximately 80 K and the liquidus temperature in the spinel primary phase field is decreased by approximately 10 K with addition of 2.0 wt pct S in the composition range investigated. It was also found that iron-zinc sulfides are present in some samples in the spinel primary phase field, which are matte appearing at low zinc concentrations and sphalerite (Zn,Fe)S at higher zinc concentrations. The presence of sulfur in the slag has a minor effect on the partitioning of ZnO between the wustite and liquid phases but no effect on the partitioning of ZnO between the spinel and liquid phases.
Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni
Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and associated metamorphic and igneous rocks, Osgood Mountains, Nevada
Garnet-pyroxene skarns were formed 90 m.y. B.P. in the Osgood Mountains at or near contacts of grandiorite with calcareous rocks of the Cambrian Preble Formation. The metasomatic replacement followed contact metamorphic recrystallization of the Preble. The sources, temperature, and variation in H2O/CO2 ratios of the metasomatic fluid are interpreted from 269 analyses of oxygen, carbon, hydrogen, and sulfur isotopes in whole rocks, minerals and inclusion fluids. Skarns formed in three mineralogical stages. Oxygen isotope data indicate that temperatures during the crystallization of garnet, pyroxene and wollastonite (Stage I) were least 550 ?? C, and that the metasomatic fluid had an {Mathematical expression} ??? 0.035 in the massive skarns, and ??? 0.12 in vein skarns up to 3 cm thick. Pore fluids in isotopic equilibrium with garnet in calc-silicate metamorphic rocks, on the other hand, had {Mathematical expression} ??? 0.15. The metasomatic fluids of Stage I were derived primarily from the crystallizing magma. The isotopic composition of magmatic water was ??18O =+9.0, ??D= -30 to -45. Oxygen isotope temperatures of greater than 620 ?? C were determined for the granodiorite. Isotopic and chemical equilibria between mineral surfaces and the metasomatic fluid were approached simultaneously in parts of the skarn several meters or more apart, while isotopic and chemical disequilibria (i.e. zoning) have been preserved between 20 to 40 ??m-thick zones in grandite garnet. More Fe-, or andradite-rich garnet crystallized in more H2O-rich C-O-H fluids ( {Mathematical expression} ??? 0.01) than present with grossularite-rich garnet ( {Mathematical expression}??? 0.035). Stage II was marked by the replacement of garnet and pyroxene by quartz, amphibole, plagioclase, epidote, magnetite, and calcite. Many of the replacement reactions took place over a relatively narrow range in temperature (480-550 ?? C), as indicated by 18O fractionations between quartz and amphibole. Meteoric water comprised 20 to 50% of the metasomatic fluid during Stage II. Calcite was formed along with pyrite, minor pyrrhotite, and chalcopyrite during Stage III, although the crystallization of pyrite and calcite had begun earlier, during Stages I and II, respectively. Carbon and sulfur isotope compositions of calcite and pyrite indicate a magmatic source for most of the C and S in the metasomatic fluids of Stage III. By the end of Stage III, meteoric water constituted as much as 100% of the metasomatic fluid. Minerals from grandiorite and skarn do not show large depletions in 18O because the oxygen isotope composition of the metasomatic fluid was buffered by the calcareous wall rocks and the grandiorite. Meteoric water in the vicinity of the Osgood Mountains during the Late Crectaceous (??18Ocale. ??? -14.0, ??D = - 107) was slightly enriched in 18O and D relative to present-day meteoric water (??18O = 15.9, ??D = - 117) ?? 1977 Springer-Verlag.
Taylor, B. E.; O'Neil, J. R.
Micromagnetic simulation of spin-transfer switching in a full-Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} alloy spin-valve nanopillar
We investigated the spin-transfer switching in a full-Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} alloy spin-valve nanopillar through micromagnetic simulation. A two-step switching hysteresis loop due to the fourfold in-plane magnetocrystalline anisotropy of Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} layers was obtained. The simulation explains the experimental result of the resistance versus current hysteresis loop and yields good agreement with the measured critical current. Furthermore, the magnetization trajectory and magnetization distribution were shown and analyzed to elucidate the different characters of two-step switching.
Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Xiao, Z. H.; Wu, P. P. [Department of Physics, University of Science and Technology Beijing, Beijing, 100083 (China); Shi, S. Q. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Chen, L. Q. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
Thermodynamic modeling of non-ideal mineral–fluid equilibria in the system Si–Al–Fe–Mg–Ca–Na–K–H–O–Cl at elevated temperatures and pressures: Implications for hydrothermal mass transfer in granitic rocks
We present the results of thermodynamic modeling of fluid–rock interaction in the system Si–Al–Fe–Mg–Ca–Na–H–O–Cl using the GEM-Selektor Gibbs free energy minimization code. Combination of non-ideal mixing properties in solids with multicomponent aqueous fluids represents a substantial improvement and it provides increased accuracy over existing modeling strategies. Application to the 10-component system allows us to link fluid composition and speciation with
David Dolejs; Thomas Wagner
Experimental determination of some periclase and spinel compositions in the system CaO-MgO-Al 2 O 3 Cr 2 O 3 -Fe-O 2 SiO 2
The solubilities of Cr2O3, Fe2O3 and Al2O3 (as well as CaO and SiO2) in periclase were determined from samples equilibrated in the temperature range 1550 to 1725° C, at two oxygen pressures (air and fO2 about 10-9atm). Most samples contained periclase, spinel, and liquid which is the mineralogy of most chrome-bearing refractories at manufacturing and service temperatures. In air a
G. M. Biggar
Phase separation in Fe2CrSi thin films
NASA Astrophysics Data System (ADS)
Thin films of a nominal Fe2CrSi alloy have been deposited by magnetron co-sputtering with various heat treatments on MgO and MgAl2O4 substrates. After heat treatment, the films were found to decompose into a nearly epitaxial Fe3Si film with the D03 structure and Cr3Si precipitates with the A15 structure. We explain the experimental results on the basis of ab initio calculations, which reveal that this decomposition is energetically highly favorable.
Meinert, Markus; Hübner, Torsten; Schmalhorst, Jan; Reiss, Günter; Arenholz, Elke
Microstructures and mechanical properties of Fe 3Al-based Fe–Al–C alloys
In this paper results on the microstructures and mechanical properties of Fe3Al-based Fe–Al–C alloys with strengthening precipitates of the perovskite-type ?-phase Fe3AlCx are presented. The alloys are prepared by vacuum induction melting and cast into Cu-moulds. The composition of the Fe3Al matrix of the investigated Fe–Al–C alloys varies between 23 and 29at.% Al. The ternary C-additions range from 1 to
A. Schneider; L. Falat; G. Sauthoff; G. Frommeyer
Realization of small intrinsic hysteresis with large magnetic entropy change in La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 by controlling itinerant-electron characteristics
NASA Astrophysics Data System (ADS)
Tuning of phase-transition characteristics in La(FexSi1-x)13 was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss QH accompanied by a large magnetic entropy change ?SM in La(FexSi1-x)13, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ?SM through magnetovolume effect. The selective enhancement of ?SM apart from QH by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ?SM of La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 is -18 J/kg K under a magnetic field change of 0-1.2 T, while the maximum value of QH becomes 1/6 of that for La(Fe0.88Si0.12)13.
Fujita, A.; Matsunami, D.; Yako, H.
U-Mo/Al-Si interaction: Influence of Si concentration
NASA Astrophysics Data System (ADS)
Within the framework of the development of low enriched nuclear fuels for research reactors, U-Mo/Al is the most promising option that has however to be optimised. Indeed at the U-Mo/Al interfaces between U-Mo particles and the Al matrix, an interaction layer grows under irradiation inducing an unacceptable fuel swelling. Adding silicon in limited content into the Al matrix has clearly improved the in-pile fuel behaviour. This breakthrough is attributed to an U-Mo/Al-Si protective layer around U-Mo particles appeared during fuel manufacturing. In this work, the evolution of the microstructure and composition of this protective layer with increasing Si concentrations in the Al matrix has been investigated. Conclusions are based on the characterization at the micrometer scale (X-ray diffraction and energy dispersive spectroscopy) of U-Mo7/Al-Si diffusion couples obtained by thermal annealing at 450 °C. Two types of interaction layers have been evidenced depending on the Si content in the Al-Si alloy: the threshold value is found at about 5 wt.% but obviously evolves with temperature. It has been shown that for Si concentrations ranging from 2 to 10 wt.%, the U-Mo7/Al-Si interaction is bi-layered and the Si-rich part is located close to the Al-Si for low Si concentrations (below 5 wt.%) and close to the U-Mo for higher Si concentrations. For Si weight fraction in the Al alloy lower than 5 wt.%, the Si-rich sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2Al 20, when the other sub-layer (close to U-Mo) is silicon free and made of UAl 3 and U 6Mo 4Al 43. For Si weight concentrations above 5 wt.%, the Si-rich part becomes U 3(Si, Al) 5 + U(Al, Si) 3 (close to U-Mo) and the other sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2Al 20. On the basis of these results and of a literature survey, a scheme is proposed to explain the formation of different types of ILs between U-Mo and Al-Si alloys (i.e. different protective layers).
Allenou, J.; Palancher, H.; Iltis, X.; Cornen, M.; Tougait, O.; Tucoulou, R.; Welcomme, E.; Martin, Ph.; Valot, C.; Charollais, F.; Anselmet, M. C.; Lemoine, P.
The sulfide capacities of CaO-SiO2 melts containing MgO, FeO, TiO2, and Al2O3
NASA Astrophysics Data System (ADS)
The sulfide capacities of CaO-SiO2 melts containing MgO, FeO, TiO2, and A12O3 have been measured by simultaneous equilibration within quartz capsules at 1776 K (1503 °C). The compositions of the melt samples and static gas phase within each capsule adjusted to establish a mutual equilibrium. The sulfide capacities, Cs, of all equilibrated samples must satisfy the following equation: 11663_2007_Article_BF02654142_TeX2GIFE1.gif C_{{text{S(}}j{text{)}}} = {{text{pctS}}_j }/{pctS_i } bullet C_{S(i)} The inclusion of several reference slags for which values of Cs are known from previous measurements enabled the calculation of the sulfide capacities of unknown samples. The influences of basic oxide substitutions (FeO and MgO) for CaO and acidic oxide substitutions (TiO2 and A12O3) for SiO2 on the sulfide capacities of CaO-SiO2 melts have been measured. When a basic oxide/acidic oxide ratio of 1.21 is maintained, MgO additions decrease sulfide capacity, while FeO, TiO2 and A12O3 additions increase sulfide capacity. The results are compared with earlier measurements on the influences of CaF2 and B2O3, and the relative effects are discussed in terms of the activity of free oxide ions.
Bronson, Arturo; Pierre, George R. St.
Sliding wear behavior of Fe–Al and Fe–Al\\/WC coatings prepared by high velocity arc spraying
A comparative study was carried out to investigate the microstructure and tribological behavior of Fe–Al and Fe–Al\\/WC iron aluminide based coatings against Si3N4 under dry sliding at room temperature using a pin-on-disc tribotester. The coatings were prepared by high velocity arc spraying (HVAS) and cored wires. The effect of normal load on friction coefficient and wear rate of the coatings
Binshi Xu; Zixin Zhu; Shining Ma; Wei Zhang; Weimin Liu
Microstructural characteristics and aging response of Zn-containing Al-Mg-Si-Cu alloy
NASA Astrophysics Data System (ADS)
Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast Al-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like ?/?-AlFeSi white intermetallics, and Chinese script-like ?-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like ?-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like ?-phase does not show any morphological and size changes. Phase transitions from ?-AlFeSi to ?-AlFeSi and from ?-AlFeSi to ?-AlFeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.
Cai, Yuan-hua; Wang, Cong; Zhang, Ji-shan
A first-principles study on surface and interface magnetism of Fe\\/ B2-FeSi(0 0 1)
We investigated the surface and interface magnetism of Fe\\/B2-FeSi(001) by using the full-potential linearized augmented plane wave method within the generalized gradient approximation to density functional theory. We considered two Fe monolayers covering FeSi(001) with the Fe interfaced [2Fe\\/FeSi(001) = 3Fe\\/SiFe(001)] and Si interfaced [2Fe\\/SiFe(001)] systems as well as the Fe terminated [FeSi(001) = 1Fe\\/SiFe(001)] and Si terminated [SiFe(001)] systems.
J. I Lee; I. G Kim
A first-principles study on surface and interface magnetism of Fe\\/B2-FeSi(001)
We investigated the surface and interface magnetism of Fe\\/B2-FeSi(001) by using the full-potential linearized augmented plane wave method within the generalized gradient approximation to density functional theory. We considered two Fe monolayers covering FeSi(001) with the Fe interfaced [2Fe\\/FeSi(001) = 3Fe\\/SiFe(001)] and Si interfaced [2Fe\\/SiFe(001)] systems as well as the Fe terminated [FeSi(001) = 1Fe\\/SiFe(001)] and Si terminated [SiFe(001)] systems.
J. I. Lee; I. G. Kim
Permeability spectra study of Fe 73.5Si 13.5B 9Cu 1Nb 3? x Al x ( x = 0, 0.1, 0.2, 0.4, 0.8 and 1.6)
The series of Nb-poor Finemet-type alloys Fe73.5Si13.5B9Cu1Nb3?xAlx (x=0, 0.1, 0.2, 0.4, 0.8 and 1.6) were prepared by partial substitution of Nb by Al and then were annealed at different temperatures under hydrogen protection. The effect of Al content as well as the annealing conditions on permeability spectra is discussed. It is found that (1) the initial permeabilities of the samples
Haishun Liu; Chunhao Yin; Xiexing Miao; Zhida Han; Dunhui Wang; Youwei Du
Al, Al/C and Al/Si implantations in 6H-SiC
NASA Astrophysics Data System (ADS)
Multiple-energy Al implantations were performed with and without C or Si coimplantations into 6H-SiC epitaxial layers and bulk substrates at 850°C. The C and Si co-implantations were used as an attempt to improve Al acceptor activation in SiC. The implanted material was annealed at 1500, 1600, and 1650°C for 45 min. The Al implants are thermally stable at all annealing temperatures and Rutherford backscattering via channeling spectra indicated good lattice quality in the annealed Al-implanted material. A net hole concentration of 8 × 1018 cm-3 was measured at room temperature in the layers implanted with Al and annealed at 1600°C. The C or Si co-implantations did not yield improvement in Al acceptor activation. The co-implants resulted in a relatively poor crystal quality due to more lattice damage compared to Al implantation alone. The out-diffusion of Al at the surface is more for 5Si co-implantation compared to Al implant alone, where 5Si means a Si/Al dose ratio of 5.
Rao, Mulpuri V.; Griffiths, Peter; Gardner, Jason; Holland, O. W.; Ghezzo, M.; Kretchmer, J.; Kelner, G.; Freitas, J. A.
High-temperature mass spectrometric study of the vaporization processes in the system CaO-MgO-Al2O3-Cr2O3-FeO-SiO2.
Knudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of twenty samples of chromium-containing slags in the CaO-MgO-Al2O3-Cr2O3-FeO-SiO2 system in the temperature range 1850-2750 K. Tungsten cells were used and Cr2O3 solid was used as a reference material. The system was calibrated using liquid gold. As FeO was the first emanating vapor species, monitoring of the chromium-containing species could be carried out only after the complete vaporization of FeO. This, however, was found to have very little impact on the concentration of the slags investigated. During the measurements, the ion current intensities of CrO+ and CrO2+ species in the mass spectra of the vapor over the CaO-MgO-Al2O3-Cr2O3-FeO-SiO2 samples were monitored and compared with those corresponding to solid Cr2O3. Data on the partial pressures of vapor species as well as the activities of Cr2O3 as a function of temperature were obtained. The results are expected to be valuable in the optimization of slag composition in high alloy steelmaking processes. PMID:19530146
Wang, L J; Stolyarova, V L; Lopatin, S I; Seetharaman, S
Spin Injection, Transport, and Detection at Room Temperature in a Lateral Spin Transport Device with Co2FeAl0.5Si0.5/n-GaAs Schottky Tunnel Junctions
NASA Astrophysics Data System (ADS)
We observed spin-valve signals and Hanle signals in four-terminal nonlocal measurements on a lateral spin transport device with Co2FeAl0.5Si0.5(CFAS)/n-GaAs Schottky tunnel junctions. The estimated spin injection/detection efficiency was 0.06 at 4.2 K, which is larger than those of the devices with Fe and CoFe electrodes [Nature Physics 3 (2007) 197 and Appl. Phys. Lett. 99 (2011) 082108]. The spin diffusion length estimated from Hanle signals was consistent with the gap length dependency of the spin-valve signals. Furthermore, the spin-valve signals were observed at up to 290 K. This is the first demonstration of detecting spin accumulation in semiconductor with full-Heusler alloys electrodes at room temperature.
Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi
Three-Dimensional Microstructure Visualization of Porosity and Fe-Rich Inclusions in SiC Particle-Reinforced Al Alloy Matrix Composites by X-Ray Synchrotron Tomography
NASA Astrophysics Data System (ADS)
Microstructural aspects of composites such as reinforcement particle size, shape, and distribution play important roles in deformation behavior. In addition, Fe-rich inclusions and porosity also influence the behavior of these composites, particularly under fatigue loading. Three-dimensional (3-D) visualization of porosity and Fe-rich inclusions in three dimensions is critical to a thorough understanding of fatigue resistance of metal matrix composites (MMCs), because cracks often initiate at these defects. In this article, we have used X-ray synchrotron tomography to visualize and quantify the morphology and size distribution of pores and Fe-rich inclusions in a SiC particle-reinforced 2080 Al alloy composite. The 3-D data sets were also used to predict and understand the influence of defects on the deformation behavior by 3-D finite element modeling.
de Andrade Silva, Flávio; Williams, Jason J.; Müller, Bernd R.; Hentschel, Manfred P.; Portella, Pedro D.; Chawla, Nikhilesh
Chimie d'interface du couple fer/alliage Al-Si (13,5 % Si) : aspects théoriques et appliqués
NASA Astrophysics Data System (ADS)
The interface chemistry of the Fe/Al-13,5 wt% Si couple has been investigated at temperatures ranging from 600 to 800 °C. New data have been acquired on the phase equilibria in the Al-Fe-Si ternary system and on the kinetics of the interface reactions. A push out test has been developed to examine the relationships between the extent, thickness or composition of the insert/alloy reaction zone and the mechanical properties of the Fe/Al-Si joint.
Pontevichi, S.; Bosselet, F.; Dezellus, O.; Peronnet, M.; Rouby, D.; Viala, J. C.
Electrochemical properties of cobalt-free La 0.80Mg 0.20Ni 2.85Al 0.11M 0.53 (M=Ni, Si, Cr, Cu, Fe) alloys
In order to investigate the effect of different B-site additions on phase structure and electrochemical properties of cobalt-free La-Mg-Ni based alloys, La0.80Mg0.20Ni2.85Al0.11M0.53 (M=Ni, Si, Cr, Cu, Fe) hydrogen storage alloys were prepared and studied systematically. X-ray powder diffraction showed that the alloys consisted mainly of LaNi3 phase and LaNi5 phase except that Cr addition caused a minor Cr phase. Electrochemical
Guochang XU; Shumin HAN; Jiansheng HAO; Zhonghou FENG; Yuan LI; Danyang XIE
High-coercivity iron-rich rare-earth permanent magnet material based on (Fe, Co)3B-Nd-M (M=Al, Si, Cu, Ga, Ag, Au)
High-coercivity, high-remanence permanent magnet materials have been obtained via a crystallization treatment of amorphous (Nd,Dy)xFe80.5?x?yCoyB18.5M1 alloys for 3?x?5 and 0?y?5, where M represent the additives Al, Si, Cu, Ga, Ag, and Au. It has been found that addition of Co and M results in a significant reduction of the crystal grain size and leads to significant improvements both in the
Satoshi Hirosawa; Hirokazu Kanekiyo; Minoru Uehara
EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel
5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.
Cheng, Wei-Jen, E-mail: firstname.lastname@example.com; Wang, Chaur-Jeng
An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2: implications for garnet-clinopyroxene geothermometry
NASA Astrophysics Data System (ADS)
Samples with eclogitic composition in the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2 were produced from various kinds of starting materials held in graphite-lined Pt capsules at a pressure of 2.5-3.0 GPa and temperatures of 800-1,300 °C using a piston-cylinder or Belt apparatus. Garnets and clinopyroxenes were characterized by analytical transmission electron microscopy and electron probe micro-analysis (EPMA). Fe3+/?Fe ratios determined by electron energy-loss spectroscopy (EELS) decrease in clinopyroxene from 22.2 ± 3.4 % at 800 °C to 13.3 ± 5.4 % at 1,300 °C, while in garnet, they vary between 10.8 ± 1.5 and 15.4 ± 4.7 %, respectively. Temperature estimates according to Krogh (Contrib Mineral Petrol 99:44-48, 1988) reproduce the experimental temperature to ±60 °C without systematic deviations if total iron is used in the calculation. If only the Fe2+ content is used, which was obtained by combining EPMA and EELS results, the experimental temperature is underestimated by 33 °C on average at 800-1,200 °C and overestimated by 77 °C on average at 1,300 °C. These systematic deviations can be explained by the temperature-dependent ratio of Fe2+/?Fe in garnet divided by that in clinopyroxene. Since the difference between the calculated and experimental temperature is relatively small, a Fe2+-based recalibration of the thermometer appears not to be necessary for the investigated system in the range of pressure, temperature and composition covered by the experiments of this study.
Purwin, Horst; Lauterbach, Stefan; Brey, Gerhard P.; Woodland, Alan B.; Kleebe, Hans-Joachim
Partitioning of Si and platinum group elements between liquid and solid Fe–Si alloys
NASA Astrophysics Data System (ADS)
Crystallization of the Earth's inner core fractionates major and minor elements between the solid and liquid metal, leaving physical and geochemical imprints on the Earth's core. For example, the density jump observed at the Inner Core Boundary (ICB) is related to the preferential partitioning of lighter elements in the liquid outer core. The fractionation of Os, Re and Pt between liquid and solid during inner core crystallization has been invoked as a process that explains the observed Os isotopic signature of mantle plume-derived lavas (Brandon et al., 1998; Brandon and Walker, 2005) in terms of core–mantle interaction. In this article we measured partitioning of Si, Os, Re and Pt between liquid and solid metal. Isobaric (2 GPa) experiments were conducted in a piston-cylinder press at temperatures between 1250 °C and 1600 °C in which an imposed thermal gradient through the sample provided solid–liquid coexistence in the Fe–Si system. We determined the narrow melting loop in the Fe–Si system using Si partitioning values and showed that order–disorder transition in the Fe–Si solid phases can have a large effect on Si partitioning. We also found constant partition coefficients (DOs, DPt, DRe) between liquid and solid metal, for Si concentrations ranging from 2 to 12 wt%. The compact structure of Fe–Si liquid alloys is compatible with incorporation of Si and platinum group elements (PGEs) elements precluding solid–liquid fractionation. Such phase diagram properties are relevant for other light elements such as S and C at high pressure and is not consistent with inter-elemental fractionation of PGEs during metal crystallization at Earth's inner core conditions. We therefore propose that the peculiar Os isotopic signature observed in plume-derived lavas is more likely explained by mantle source heterogeneity (Meibom et al., 2002; Baker and Krogh Jensen, 2004; Luguet et al., 2008).
Morard, G.; Siebert, J.; Badro, J.
Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe 2 O 3 SiO 2 -CaO-MgO-Al 2 O 3 System at PO 2 10 ?8 atm
Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all\\u000a are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational\\u000a temperature. Optimal control of the slag chemistry in the copper
Hector M. Henao; Colin Nexhip; David P. George-Kennedy; P. C. Hayes; E. Jak
Magnetic Properties of Disordered Fe3Al
NASA Astrophysics Data System (ADS)
The magnetic properties of Fe3Al powders prepared by filing the ingot in both as-filed and annealed form are studied. Results of Mössbauer, X-ray diffraction and DC magnetization studies show that the magnetic properties are modified due to formation of non-magnetic Fe3AlC0.5 phase due to C intercalated on filing. The hyperfine fields obtained are explained in terms of nearest and next nearest neighbor configurations of 57Fe.
Nehra, J.; Kabra, K.; Jani, S.; Ranjith, P. M.; Lakshmi, N.; Venugopalan, K.
Energetic ion bombarded Fe/Al multilayers
The utility of ion-assisted deposition is investigated to explore the possibility of counteracting the deficiency of back-reflected current of Ar neutrals in the case of lighter elements such as Al. A range of energetically ion bombarded Fe/Al multilayers sputtered with applied surface bias of 0, -200, or -400 V were deposited onto Si(111) substrates in an argon atmosphere of 4 mTorr using a computer controlled dc magnetron sputtering system. Grazing incidence reflectivity and rocking curve scans by synchrotron x rays of wavelength of 1.38 A were used to investigate the structures of the interfaces produced. Substantial evidence has been gathered to suggest the gradual suppression of interfacial mixing and reduction in interfacial roughness with increases of applied bias. The densification of the Al microstructure was noticeable and may be a consequence of resputtering attributable to the induced ion bombardment. The average interfacial roughnesses were calculated for the 0, -200, and -400 V samples to be 7{+-}0.5, 6{+-}0.5, and 5{+-}0.5 A respectfully demonstrating a 30% improvement in interface quality. Data from rocking curve scans point to improved long-range correlated roughness in energetically deposited samples. The computational code based on the recursive algorithm developed by Parratt [Phys. Rev. 95, 359 (1954)] was successful in the simulation of the specular reflectivity curves.
Al-Busaidy, M.S.; Crapper, M.D. [College Science, Physics Department, Sultan Qaboos University, P.O. Box 36, Al-Khod 123 (Oman); Department of Physics, Loughborough University, Loughborough (United Kingdom)
Structure of multicomponent SiO 2-Al 2O 3-Fe 2O 3-CaO-MgO glasses for the preparation of fibrous insulating materials
NASA Astrophysics Data System (ADS)
Glasses used for the fabrication of fibrous insulating materials are made from natural raw materials, mainly basalts. Basalt alloys, however, show relatively high crystallization capability, which is disadvantageous for throwing and durability of the fibres prepared. In the work new raw materials, such as melaphyres and diabase from the Silesia region of Poland were applied for the preparation of aluminosilicate alloys. In order to study their crystallization ability the glasses were heated in an electric furnace at various temperatures for various time periods. Depending on the raw material used as well as the temperature of heat-treatment amorphous or crystalline materials were obtained. Crystalline phases were identified based on X-ray diffraction studies. It was found that magnetite/titanomagnetite crystallized in the first step. Then pyroxenes phases of diopsides or augite type appeared in the systems. Spectroscopic investigations in the mid IR region were carried out for all the glasses. This made it possible to determine the influence of thermal treatment on the structural changes of glasses (changes in the spectra shapes). Locations of the bands due to Al-O-Si and Si-O-Si bridges vibrations suggested that in most cases the augite-type phases were present in the systems (aluminium coordination number equal to 4 and 6). Appearance of aluminium in coordination 4 and 6 was confirmed by NMR investigations (two clear bands in the spectra).
Lubas, M.; Sitarz, M.; Fojud, Z.; Jurga, S.
Electronic structure of Fe3Si on Si(100) substrates
NASA Astrophysics Data System (ADS)
The improved performance of large-scale integrated circuits (LSIs) by the shrinking of devices is becoming difficult due to physical limitations. Here we report, the growth and formation of Fe3Si on Si(100) and characterized by x-ray photoemission, UV photoemission and low energy electron diffraction to study the electronic structure. The results revealed that the DO3 phase formation is exist and photoemission results also support the electron diffraction outcome.
Lal, Chhagan; Di Santo, G.; Caputo, M.; Panighel, M.; Taleatu, B. A.; Goldoni, A.; Jain, I. P.
Experimental kerma coefficients and dose distributions of C, N, O, Mg, Al, Si, Fe, Zr, A-150 plastic, Al2O3, AlN, SiO2 and ZrO2 for neutron energies up to 66 MeV
NASA Astrophysics Data System (ADS)
Low-pressure proportional counters (LPPCs) with walls made from the elements C, Mg, Al, Si, Fe and Zr and from the chemical compounds A-150 plastic, AlN, Al2 O3 , SiO2 and ZrO2 were used to measure neutron fluence-to-kerma conversion coefficients at energies up to 66 MeV. The LPPCs served to measure the absorbed dose deposited in the gas of a cavity surrounded by the counter walls that could be converted to the absorbed dose to the wall on the basis of the Bragg-Gray cavity theory. Numerically the absorbed doses to the walls were almost equal to the corresponding kerma values of the wall materials. The neutron fluence was determined by various experimental methods based on the reference cross sections of the 1 H(n,p) scattering and/or the 238 U(n,f) reactions. The measurements were performed in monoenergetic neutron fields of energies of 5 MeV, 8 MeV, 15 MeV and 17 MeV and in polyenergetic neutron beams with prominent peaks of energies of 34 MeV, 44 MeV and 66 MeV. For the measurements in the polyenergetic neutron beams, significant corrections for the contributions of the non-peak energy neutrons were applied. The fluence-to-kerma conversion coefficients of N and O were determined using the difference technique applied with matched pairs of LPPCs made from a chemical compound and a pure element. This paper reports experimental fluence-to-kerma conversion coefficient values of eight elements and four compounds measured for seven neutron energies, and presents a comparison with data from previous measurements and theoretical predictions. The distributions of the absorbed dose as a function of the lineal energy were measured for monoenergetic neutrons or, for polyenergetic neutron fields, deduced by applying iterative unfolding procedures in order to subtract the contributions from non-peak energy neutrons. The dose distributions provide insight into the neutron interaction processes.
Schrewe, U. J.; Newhauser, W. D.; Brede, H. J.; DeLuca, P. M., Jr.
Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 System at PO2 10-8 atm
NASA Astrophysics Data System (ADS)
Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10-8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl2O3.
Henao, Hector M.; Nexhip, Colin; George-Kennedy, David P.; Hayes, P. C.; Jak, E.
Modification of hypoeutectic Al-Si alloys
Modification of the Al-Si eutectic microstructure has been studied by using the entrained droplet technique in a range of hypoeutectic Al-Si alloys doped with different levels of phosphorus and sodium. Differential scanning calorimetry has been used to investigate the kinetics of silicon nucleation during eutectic solidification, and transmission and scanning transmission electron microscopy has been used to investigate the eutectic
C. R. Ho; B. Cantor
The self diffusion of iron in Fe2SiO4 and CaFeSiO4 melts
The self diffusion of iron in Fe2SiO4 and CaFeSiO4 melts has been measured in the temperature range 1250° to 1540°C using Fe59 as the radio tracer and the capillary-liquid reservoir method of diffusion measurement. The results obtained are represented by log D_{Fe} = - {3800 ± 500}\\/T - 2.74 ± 0.29 for Fe2SiO4, and log D_{Fe} = - {5450 ±
D. P. Agarwal; D. R. Gaskell
High-performance batteries for off-peak energy storage and electric-vehicle propulsion. Progress report, January--March 1976. [Li--Al\\/LiCl--KCl\\/FeS or FeS; some work on CaAl, CaSi, and Mg anodes and FeS, FeO and FeS cathodes; ANL
The research and management efforts of Argonne National Laboratory's program on lithium\\/metal sulfide batteries during the period January--March 1976 are described. These batteries are being developed for energy storage on utility networks and for electric-vehicle propulsion. The present cells are vertically oriented, prismatic cells with a central positive electrode of FeS or FeS and two facing negative electrodes of lithium--aluminum
P. A. Nelson; R. O. Ivins; N. P. Yao; J. E. Battles; A. A. Chilenskas; E. C. Gay; R. K. Steunenberg; W. J. Walsh
Structure alterations in microporous (Mg,Fe){sub 2}Al{sub 4}Si{sub 5}O{sub 18} crystals induced by energetic heavy-ion irradiation
The microporous framework structure of (Mg{sub 1-x}Fe{sub x}){sub 2}Al{sub 4}Si{sub 5}O{sub 18} (=cordierite) has been subject to a comparative study on the effect of structural alterations originating from exposure to high-energy heavy ions. Oriented samples (with x=0.061, 0.122, and 0.170) were irradiated with swift {sup 124}Xe, {sup 197}Au and {sup 96}Ru ions with 11.1 MeV per nucleon energy and fluences of 1x10{sup 12} and 1x10{sup 13} ions/cm{sup 2}. Irradiated and non-irradiated samples were investigated by means of X-ray diffraction, Moessbauer spectroscopy and optical absorption spectroscopy. Structural investigations reveal an essentially unchanged Al,Si ordering, which appears to be unaffected by irradiation. The most remarkable macroscopic change is the ion-beam induced colouration, which could be assigned to electronic charge transfer transitions involving the Fe cations. Moessbauer spectra indicate an increased amount of {sup [4]}Fe{sup 3+} for the irradiated sample. The most noticeable structural alteration concerns irradiation-induced dehydration of extra-framework H{sub 2}O, which is accompanied by a reduction in the molar volume by {approx}0.2 vol%. - Graphical abstract: Cordierite single-crystal specimen showing the color change from pale blue (unirradiated) to a yellowish brown layer (irradiated) after exposure to relativistic {sup 124}Xe ions at a fluence of 1x10{sup 12} ions per cm{sup 2}.
Miletich, Ronald, E-mail: firstname.lastname@example.com [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Diego Gatta, G. [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Redhammer, Guenther J. [Fachbereich Materialforschung und Physik, Abteilung Mineralogie, Universitaet Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg (Austria); Burchard, Michael; Meyer, Hans-Peter [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Weikusat, Christian [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany); Rotiroti, Nicola [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Glasmacher, Ulrich A. [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Trautmann, Christina; Neumann, Reinhard [GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany)
Formation and ferromagnetic properties of FeSi thin films
In this work, the growth and ferromagnetic properties of {epsilon}-FeSi thin film on Si(100) substrate prepared by molecular beam epitaxy are reported. The inter-diffusion of Fe layer on Si(100) substrate at 600 Degree-Sign C results in polycrystalline {epsilon}-FeSi layer. The determined activation energy was 0.044 eV. The modified magnetism from paramagnetic in bulk to ferromagnetic states in {epsilon}-FeSi thin films was observed. The saturated magnetization and coercive field of {epsilon}-FeSi film are 4.6 emu/cm{sup 3} and 29 Oe at 300 K, respectively.
Shin, Yooleemi; Anh Tuan, Duong; Hwang, Younghun; Viet Cuong, Tran; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of)
Influence of Si/Fe ratio in multilayer structures on crystalline growth of {beta}-FeSi{sub 2} thin film on Si substrate
The deposited Si/Fe ratio has been found to have a significant influence on crystalline growth of {beta}-FeSi{sub 2} film on Si substrate. Stoichiometry is always satisfied by interdiffusion of Si, under both Si-lean and Si-rich conditions. However, Si diffusion from the substrate into the deposited layer, which compensates for deficient Si, induces an undulated interface, as well as Fe and Si vacancies. On the other hand, excess Si is driven to the {beta}-FeSi{sub 2}/Si interface, which results in a lamellar structure with a large number of small grains. Fe and Si vacancies are significantly reduced by excess Si. These results suggest that precise control of the Si/Fe ratio is essential for good crystallinity and fewer vacancies.
Liu Zhengxin [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 2, Umezono 1-1-1, Tsukuba 305-8568 (Japan); Technology Development Department, System Engineers', Company, Limited, AIST Tsukuba West, Onogawa 16-1, Tsukuba 305-8569 (Japan); Tanaka, Miyoko [High Voltage Electron Microscopy Station, National Institute for Materials Science, Sakura 3-13, Tsukuba 305-0003 (Japan); Kuroda, Ryo; Makita, Yunosuke [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 2, Umezono 1-1-1, Tsukuba 305-8568 (Japan); Osamura, Masato [Technology Development Department, System Engineers', Company, Limited, AIST Tsukuba West, Onogawa 16-1, Tsukuba 305-8569 (Japan)
Tunneling magnetoresistance in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junctions
NASA Astrophysics Data System (ADS)
We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junction (MTJ). It is found that the spin-polarized conductance and bias-dependent TMR ratios are rather sensitive to the structure of Fe3Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized ?1 symmetry bands crossing the Fermi level for the cubic Fe3Si. In contrast, the tetragonal Fe3Si driven by in-plane strain reveals half-metal nature in terms of ?1 state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe3Si electrodes under zero bias. However, the giant TMR ratio resulting from interface resonant transmission for the former decreases rapidly with the bias. For the latter, the giant TMR ratio can maintain up to larger bias due to coherent transmission through the majority-spin ?1 channel.
Tao, L. L.; Liang, S. H.; Liu, D. P.; Wei, H. X.; Wang, Jian; Han, X. F.
Development of SiAlON materials
NASA Technical Reports Server (NTRS)
Cold pressing and sintering techniques were used to produce ceramic test specimens in which the major phase was either Si3N4 or a solid solution having the beta Si3N4 structure. Additional components were incorporated to promote liquid phase sintering. Glass and/or crystalline phase were consequently retained in boundaries between Si3N4 grains which largely determined the physical properties of the bodies. Systems investigated most extensively included R-Si-Al-O-N (R = rare earth element) Zr-Si-Al-O-N, Y-Si-Be-O-N, and R1-R2-Si-O-N. Room temperature and 1370 C modulus of ruptured, 1370 C creep, and oxidation behavior are discussed in terms of phase relationships in a parent quinery, and relavent oxide systems.
Layden, G. K.
Crystal structure of the NaCa(Fe2+, Al, Mn)5[Si8O19(OH)](OH)7 · 5H2O mineral: A new representative of the palygorskite group
NASA Astrophysics Data System (ADS)
A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Å, b = 17.901(1) Å, c = 13.727(1) Å, ? = 90.018(3)°, ? = 97.278(4)°, and ? = 89.952(3)°. The structure is solved by the direct methods in space group P bar 1 and refined to R = 5.5% for 4168 | F| > 7?( F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula ( Z = 1) is (Na1.6K0.2Ca0.2)[Ca2(Fe{3.6/2+}Al1.6Mn0.8)(OH)9(H2O)2][(Fe{3.9/2+}Ti0.1)(OH)5(H2O)2][Si16O38(OH)2] · 6H2O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.
Rastsvetaeva, R. K.; Aksenov, S. M.; Verin, I. A.
Interfacial Reaction Between CaO-SiO2-MgO-Al2O3 Flux and Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) Steel at 1873 K (1600 °C)
NASA Astrophysics Data System (ADS)
This study investigated the interfacial reaction kinetics and related phenomena between CaO-SiO2-MgO-Al2O3 flux and Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) steel, which simulates transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels at 1873 K (1600 °C). It also examines the effect of changes in the composition of the steel and slag phases on the interfacial reaction rate and the reaction mechanisms. The content of Al and Si in the 1 mass pct Al-containing steel was found to change rapidly within the first 15 minutes of the reaction, but then it remained relatively constant. The content of Al and Si in the 3 to 6 mass pct Al-containing steels, in contrast, changed continuously throughout the entire reaction time. In addition, the content of Mn in the 1 mass pct Al-containing steels initially decreased with increasing time, but the content did not change in the 3 to 6 mass pct Al-containing steels. Furthermore, the mass transfer coefficient of Al, k Al, in the 1 mass pct Al-containing systems was significantly higher than that in other systems; i.e., the k Al can be arranged such that 1 mass pct Al systems >> 3 mass pct Al systems ? 6 mass pct Al systems. The compositions of the final slags were close to the saturation lines of the [Mg,Mn]Al2O4 and MgAl2O4 spinels when the slags reacted with 1 mass pct Al and 3 to 6 mass pct Al-containing steels, respectively. These results, which show the effect of Al content on the reaction phenomena, can be explained by the significant increase in the apparent viscosity of the slags that reacted with the 3 to 6 mass pct Al-containing steels. This reaction was likely caused by the precipitation of solid compounds such as MgAl2O4 spinel and CaAl4O7 grossite at locally alumina-enriched areas in the slag phase. This analysis is in good accordance with the combination of Higbie's surface renewal model and the Eyring equation.
Kim, Dong Jin; Park, Joo Hyun
Four-terminal nonlocal signals in lateral spin transport devices with variously ordered Co2FeAl0.5Si0.5 full-Heusler alloy electrodes
NASA Astrophysics Data System (ADS)
The structural ordering of the Co2FeAl0.5Si0.5 (CFAS) full-Heusler alloy, the electrical transport properties, and the four-terminal (4T) nonlocal signals were investigated in lateral spin transport devices with CFAS/n-GaAs Schottky tunnel junctions as a function of the deposition temperature of CFAS (TCFAS). The 4T nonlocal signals increased with increasing TCFAS, in contrast to the trend in three-terminal Hanle measurements [Jpn. J. Appl. Phys., Part 1 52, 063001 (2013)]. No relationship between interface resistance and 4T nonlocal signal was confirmed, indicating that conductance mismatch problems did not affect the tendency of signal values.
Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi
Magneto-optical characterization of single crystalline Co2FeAl0.4Si0.6 thin films on MgO(1?0?0) substrates with Cr and MgO seed layers
NASA Astrophysics Data System (ADS)
We report on the experimental investigation of the influence of a seed layer on the magnetic properties of the full-Heusler alloy Co2FeAl0.4Si0.6 (CFAS). The studied magnetic films are grown epitaxially on MgO (1?0?0) substrates with Cr and/or MgO seed layers. By employing magneto-optical Kerr effect magnetometry we show that magnetic anisotropy can be tuned by choosing the proper seed layer. The results on CFAS show an overall uniaxial anisotropy plus a biaxial contribution which depends on the seed layer. In addition, if grown on MgO, a sharp increase in the coercive field HC at a series of angles symmetric with respect to the easy axis is present. Scanning Kerr-microscope imaging is performed during the magnetization reversal process in order to reveal the type of magnetic domain formation taking place at these angles.
Ruiz-Calaforra, A.; Conca, A.; Graf, T.; Casper, F.; Leven, B.; Felser, C.; Hillebrands, B.
Preparation and characterization of highly L2{sub 1}-ordered full-Heusler alloy Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} thin films for spintronics device applications
We report the investigation of structure and magnetic properties of full-Heusler alloy Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) thin films grown on MgO-buffered MgO (001) substrates through magnetron sputtering. It was found that single-crystal CFAS thin films with high degree of L2{sub 1} ordering and sufficiently flat surface could be obtained after postdeposition annealing. All the films show a distinct uniaxial magnetic anisotropy with the easy axis of magnetization along the in-plane [110] direction. These results indicate that the use of the MgO buffer for CFAS is a promising approach for achieving a higher tunnel magnetoresistance ratio, and thus for spintronics device applications.
Wang Wenhong; Sukegawa, Hiroaki; Shan Rong; Furubayashi, Takao; Inomata, Koichiro [Magnetic Materials Center, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
Micromagnetic simulation of critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin valve nanopillar
NASA Astrophysics Data System (ADS)
We investigated the critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulations. The simulations explain the experimental results on the resistance versus external magnetic field and yield good agreement with the measured switching behavior. It is shown that different magnitudes of current densities and directions of external magnetic fields give rise to a shift of resistance hysteretic loop and a variable range of switching. We demonstrated that three critical current densities have different slopes with Gilbert damping constant ? and spin polarization constant ?, indicating that ? and ? have different contributions to the critical current densities. Furthermore, we found that the area of resistance-current hysteretic loop decreases as the nanopillar size decreases. The domain structures indicated that the magnetization reversals have different switching processes between small and large sizes of pillars.
Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Shi, S. Q.; Chen, L. Q.
Measurements of the sound velocities in a single crystal of FeSi were performed in the temperature range 4-300 K. Elastic constants C{sub 11} and C{sub 44} deviate from a quasiharmonic behavior at high temperature; on the other hand, elastic constants C{sub 12} increases anomalously in the entire temperature range, indicating a change in the electron structure of this material.
Petrova, A. E.; Krasnorussky, V. N.; Stishov, S. M., E-mail: email@example.com [Russian Academy of Sciences, Institute for High Pressure Physics (Russian Federation)
Effects of temperature and pressure on phonons in FeSi1-xAlx
NASA Astrophysics Data System (ADS)
The effects of temperature and pressure on phonons in B20 compounds FeSi1-xAlx were measured using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering. The effect of hole doping through Al substitution is compared to results of alloying with Co (electron doping) in Fe1-xCoxSi. While the temperature dependence of phonons in FeSi is highly anomalous, doping with either type of carriers leads to a recovery of the normal quasiharmonic behavior. Density functional theory (DFT) computations of the electronic band structure and phonons were performed. The anomaly in the temperature dependence of the phonons in undoped FeSi was related to the narrow band gap, and its sensitivity to the effect of thermal disordering by phonons. On the other hand, the pressure dependence of phonons at room temperature in undoped FeSi follows the quasiharmonic behavior and is well reproduced by the DFT calculations.
Delaire, O.; Al-Qasir, I. I.; Ma, J.; dos Santos, A. M.; Sales, B. C.; Mauger, L.; Stone, M. B.; Abernathy, D. L.; Xiao, Y.; Somayazulu, M.
Magnetic shape anisotropy calculations of Fe nanostructures at the Si/Fe(1 1 1) interface
NASA Astrophysics Data System (ADS)
The influence of Si capping layers on the magnetic properties of thin Fe films grown on Si(1 1 1) has been studied by means of shape anisotropy calculations. Fe surface morphology simulations are realized using experimental STM data. Surface modifications induced by the interaction between the Si overlayer and the Fe surface are performed in agreement with the model proposed in a previous work by Stephan et al. [J. Magn. Mater. 293 (2005) 746]. Calculations of the uniaxial anisotropy energy constant Ku are then performed on the modified Fe surface morphology for different Si deposition geometries as proposed in the model. The relevant data deduced by this method such as anisotropy constants and their related easy axis direction, are directly compared to the experimental ones obtained by ex situ magneto-optical Kerr effect (MOKE) measurements at room temperature using the transverse bias initial inverse susceptibility and torque (TBIIST) method. We show that a very good agreement between those results leads to a confirmation of the proposed model.
Stephan, R.; Zabrocki, S.; Berling, D.; Mehdaoui, A.; Wetzel, P.
Truncated tetrahedron seed crystals initiating stereoaligned growth of FeSi nanowires.
We have synthesized epitaxially grown freestanding FeSi nanowires (NWs) on an m-Al(2)O(3) substrate by using a catalyst-free chemical vapor transport method. FeSi NW growth is initiated from FeSi nanocrystals, formed on a substrate in a characteristic shape with a specific orientation. Cross-section TEM analysis of seed crystals reveals the crystallographic structure and hidden geometry of the seeds. Close correlation of geometrical shapes and orientations of the observed nanocrystals with those of as-grown NWs indicates that directional growth of NWs is initiated from the epitaxially formed seed crystals. The diameter of NWs can be controlled by adjusting the composition of Si in a Si/C mixture. The epitaxial growth method for FeSi NWs via seed crystals could be employed to heteroepitaxial growth of other compound NWs. PMID:22966939
Kim, Si-in; Yoon, Hana; Seo, Kwanyong; Yoo, Youngdong; Lee, Sungyul; Kim, Bongsoo
Hillesheimite, (K,Ca,?)2(Mg,Fe,Ca,?)2[(Si,Al)13O23(OH)6](OH) · 8H2O, a new phyllosilicate mineral of the Günterblassite group
NASA Astrophysics Data System (ADS)
A new mineral, hillesheimite, has been found in the Graulai basaltic quarry, near the town of Hillesheim, the Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. It occurs in the late assemblage comprising nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite-group minerals, and åkermanite. Colorless flattened crystals of hillesheimite reaching 0.2 × 1 × 1.5 mm in size and aggregates of the crystals occur in miarolitic cavities in alkali basalt. The mineral is brittle, with Mohs' hard-ness 4. Cleavage is perfect parallel to (010) and distinct on (100) and (001). D calc = 2.174 g/cm3, D meas = 2.16(1) g/cm3. IR spectrum is given. Hillesheimite is biaxial (-), ? = 1.496(2), ? = 1.498(2), ? = 1.499(2), 2 V meas = 80°. The chemical composition (electron microprobe, mean of 4 point analyses, H2O determined from structural data, wt %) is as follows: 0.24 Na2O, 4.15 K2O, 2.14 MgO, 2.90 CaO, 2.20 BaO, 2.41 FeO, 15.54 Al2O3, 52.94 SiO2, 19.14 H2O, total is 101.65. The empirical formula is: K0.96Na0.08Ba0.16Ca0.56Mg0.58Fe{0.37/2+}[Si9.62Al3.32O23(OH)6][(OH)0.82(H2O)0.18] · 8H2O. The crystal structure has been determined from X-ray single-crystal diffraction data, R = 0.1735. Hillesheimite is orthorhombic, space group Pmmn, the unit-cell dimensions are: a = 6.979(11), b = 37.1815(18), c = 6.5296(15) Å; V=1694(3) Å3, Z = 2. The crystal structure is based on the block [(Si,Al)13O25(OH)4] consisting of three single tetrahedral layers linked via common vertices and is topologically identical to the triple layers in günterblassite and umbrianite. The strong reflections [ d Å ( I %)] in the X-ray powder diffraction pattern are: 6.857(58), 6.545(100), 6.284(53), 4.787(96), 4.499(59), 3.065(86), 2.958(62), 2.767(62). The mineral was named after its type locality. Type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.
Chukanov, N. V.; Zubkova, N. V.; Pekov, I. V.; Belakovskiy, D. I.; Schüller, W.; Ternes, B.; Blass, G.; Pushcharovsky, D. Yu.
A thermodynamic model for di-trioctahedral chlorite from experimental and natural data in the system MgO-FeO-Al2O3-SiO2-H2O: applications to P- T sections and geothermometry
NASA Astrophysics Data System (ADS)
We present a new thermodynamic activity-composition model for di-trioctahedral chlorite in the system FeO-MgO-Al2O3-SiO2-H2O that is based on the Holland-Powell internally consistent thermodynamic data set. The model is formulated in terms of four linearly independent end-members, which are amesite, clinochlore, daphnite and sudoite. These account for the most important crystal-chemical substitutions in chlorite, the Fe-Mg, Tschermak and di-trioctahedral substitution. The ideal part of end-member activities is modeled with a mixing-on-site formalism, and non-ideality is described by a macroscopic symmetric (regular) formalism. The symmetric interaction parameters were calibrated using a set of 271 published chlorite analyses for which robust independent temperature estimates are available. In addition, adjustment of the standard state thermodynamic properties of sudoite was required to accurately reproduce experimental brackets involving sudoite. This new model was tested by calculating representative P- T sections for metasediments at low temperatures (<400 °C), in particular sudoite and chlorite bearing metapelites from Crete. Comparison between the calculated mineral assemblages and field data shows that the new model is able to predict the coexistence of chlorite and sudoite at low metamorphic temperatures. The predicted lower limit of the chloritoid stability field is also in better agreement with petrological observations. For practical applications to metamorphic and hydrothermal environments, two new semi-empirical chlorite geothermometers named Chl(1) and Chl(2) were calibrated based on the chlorite + quartz + water equilibrium (2 clinochlore + 3 sudoite = 4 amesite + 4 H2O + 7 quartz). The Chl(1) thermometer requires knowledge of the (Fe3+/?Fe) ratio in chlorite and predicts correct temperatures for a range of redox conditions. The Chl(2) geothermometer which assumes that all iron in chlorite is ferrous has been applied to partially recrystallized detrital chlorite from the Zone houillère in the French Western Alps.
Lanari, Pierre; Wagner, Thomas; Vidal, Olivier
The structure and mechanical properties of Fe 3Al–30 vol.% Al 2O 3 nanocomposite
Fe3Al–30vol.% Al2O3 nanocomposite powder was fabricated via two routes. The first route involved the ball milling of Fe2O3–Al–Fe powder mixtures to produce in situ Al2O3 nanoparticles in Fe3Al matrix via mechanochemical reaction of Fe2O3 and Al. In the second route, Fe3Al–Al2O3 nanocomposite was prepared by ex situ addition of Al2O3 nanopowder to Fe–Al powder mixture followed by ball milling. The
M. Khodaei; M. H. Enayati; F. Karimzadeh
The mechanical properties of FeAl
Only in the last few years has progress been made in obtaining reproducible mechanical properties data for FeAl. Two sets of observations are the foundation of this progress. The first is that the large vacancy concentrations that exist in FeAl at high temperature are easily retained at low temperature and that these strongly affect the low-temperature mechanical properties. The second is that RT ductility is adversely affected by water vapor. Purpose of this paper is not to present a comprehensive overview of the mechanical properties of FeAl but rather to highlight our understanding of key phenomena and to show how an understanding of the factors which control the yield strength and fracture behavior has followed the discovery of the above two effects. 87 refs, 9 figs.
Baker, I. [Dartmouth Coll., Hanover, NH (United States); George, E.P. [Oak Ridge National Lab., TN (United States)
Ferromagnetic FePt nanoparticles formed in Al2O3 by ion implantation
Oriented, ferromagnetic FePt nanoparticles have been produced in Al2O3 single crystals by ion implantation and annealing. FePt orientation and particle size depends strongly on the implantation conditions. Magnetic coercivities of these nanocomposites are extremely high, reaching values in excess of 20 kOe for Pt concentrations of \\/~45% in the FePt alloy. The formation of ferromagnetic FePt nanoparticles in fused SiO2
C. W. White; S. P. Withrow; J. D. Budai; L. A. Boatner; K. D. Sorge; J. R. Thompson; K. S. Beaty; A. Meldrum
Formation and properties of high Fe-content Fe-(B-Si)-Zr bulk amorphous alloys
NASA Astrophysics Data System (ADS)
The present work is devoted to the development of Fe-(B-Si)-Zr amorphous alloys with high glass-forming ability and good magnetic properties. Using the cluster-plus-glue-atom model proposed for ideal amorphous structures, [FeFe11B3Si](Fe1- x Zr x ) was determined as the cluster formula of Fe-(B-Si)-Zr alloys. The glass formation and thermal stability of the serial alloys, namely, [FeFe11B3Si](Fe1- x Zr x ) ( x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.75, and 1.0), were studied by the combination of copper mold casting, X-ray diffraction, and differential thermal analysis techniques. The maxima of glass-forming ability and thermal stability were found to occur at the compositions of [FeFe11B3Si](Fe0.6Zr0.4) and [FeFe11B3Si](Fe0.5Zr0.5). The alloys can be cast into amorphous rods with 1.5 mm diameter, and upon reheating, the amorphous alloys exhibit a large undercooled liquid span of 37 K. The saturation magnetization of the [FeFe11B3Si](Fe0.5Zr0.5) amorphous alloy was measured to be 1.4 T.
Geng, Yao-xiang; Wang, Ying-min; Qiang, Jian-bing; Wang, Qing; Kong, Fan-yang; Zhang, Gui-feng; Dong, Chuang
A Sulfide Capacity Prediction Model of CaO-SiO2-MgO-FeO-MnO-Al2O3 Slags during the LF Refining Process Based on the Ion and Molecule Coexistence Theory
NASA Astrophysics Data System (ADS)
A sulfide capacity prediction model of CaO-SiO2-MgO-FeO-MnO-Al2O3 ladle furnace (LF) refining slags has been developed based on the ion and molecule coexistence theory (IMCT). The predicted sulfide capacity of the LF refining slags has better accuracy than the measured sulfide capacity of the slags at the middle and final stages during the LF refining process. Increasing slag binary basicity, optical basicity, and the Mannesmann index can lead to an increase of the predicted sulfide capacity for the LF refining slags as well as to an increase of the sulfur distribution ratio between the slags and molten steel at the middle and final stages during the LF refining process. The calculated equilibrium mole numbers, mass action concentrations of structural units or ion couples, rather than mass percentages of components, are recommended to represent the slag composition for correlating with the sulfide capacity of the slags. The developed sulfide capacity IMCT model can calculate not only the total sulfide capacity of the slags but also the respective sulfide capacity of free CaO, MgO, FeO, and MnO in the slags. The comprehensive contribution of the combined ion couples (Ca2+ + O2-) and (Mn2+ + O2-) on the desulfurization reactions accounts for 96.23 pct; meanwhile, the average contribution of the ion couple (Fe2+ + O2-) and (Mg2+ + O2-) only has a negligible contribution as 3.13 pct and 0.25 pct during the LF refining process, respectively. The oxygen activity of bulk molten steel in LF is controlled by the [Al]-[O] equilibrium, and the oxygen activity of molten steel at the slag-metal interface is controlled by the (FeO)-[O] equilibrium. The ratio of the oxygen activity of molten steel at the slag-metal interface to the oxygen activity of bulk molten steel will decrease from 37 to 5 at the initial stage, and further decrease from 28 to 4 at the middle stage, but will maintain at a reliable constant as 5 to 14 at the final stage during the LF refining process. The proposed high-oxygen potential layer of molten steel beneath the slag-metal interface can be quantitatively verified.
Yang, Xue-Min; Zhang, Meng; Shi, Cheng-Bin; Chai, Guo-Ming; Zhang, Jian
An evaluation of weldments joined by Fe-Mn-Al and Fe-Cr-Ni consumables
Stainless steel plates were joined using Fe-Mn-Al and Fe-Cr-Ni consumables to evaluate the strength and corrosion resistance of the weldments. The Fe-Mn-Al consumables successfully joined austenitic stainless steel plates. However, the corrosion performance of the Fe-Mn-Al weld metals was poor. As a result, at room temperature, Fe-Mn-Al consumables cannot replace Fe-Cr-Ni consumables in an acidic chloride-bearing environment.
Aidun, D.K.; Makhamreh, K.M.; Morrison, D.J. (Clarkson Univ., Potsdam, NY (United States)); Olszewski, J. (Aluminum Co. of America, Massena, NY (United States))
Magnetic properties of Al/57Fe/Cr multilayers
NASA Astrophysics Data System (ADS)
Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.
Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.
Characterization of Si-added aluminum oxide (AlSiO) films for power devices
Synthesis of Si-added aluminum oxide (AlSiO) films is attempted as an insulating film with both a wide bandgap and a high dielectric constant. Electrical characteristics of AlSiO films are investigated. Leakage current of the AlO film is suppressed by Si addition and is minimized with Si composition ratio of 12%. Capacitance versus voltage (C–V) measurements are carried out for Au\\/AlSiO\\/Si
Naoyoshi Komatsu; Keiko Masumoto; Hidemitsu Aoki; Chiharu Kimura; Takashi Sugino
The molar volume of cubic garnets in the system SiO2-Al2O3-TiO2-Fe2O3-Cr2O3-FeO-MnO-MgO-CaO-Na2O
NASA Astrophysics Data System (ADS)
Garnet is a critical phase that controls major and trace element partitioning at pressures above ~3 GPa during partial melting of the Earth's upper mantle. A molar volume model is calibrated for cubic garnets (space group Ia3d) in the oxide system listed in the title. This model and a recent calibration of spinel molar volume (Hamecher et al., in press, CMP) will be used in calibration of thermodynamic activity-composition models of garnet and pyroxene solid solutions. The activity and molar volume models will be incorporated into the next generation MELTS (Ghiorso & Sack, 1995, CMP) model, xMELTS. A new garnet volume model calibrated with recent in situ high-P, T diffraction data is crucial for accurately modeling key mineralogical transitions in the mantle, e.g., the spinel-garnet transition and the mantle transition zone. Above 5 GPa a majorite component is an essential part of any thermodynamic model of mantle garnets, which to be useful must accurately predict garnet stability with respect to spinel, pyroxene, perovskites, and melt. Our model system contains nine independent end members: Ca3Al2Si3O12, Mg3Al2Si3O12, Fe2+3Al2Si3O12, Mg3Cr2Si3O12, Mg3Fe3+2Si3O12, Mn3Al2Si3O12, Na2(MgSi2)Si3O12, Mg3(TiMg)Si3O12, and cubic majorite component Mg3(MgSi)Si3O12. An inclusive set of end-member components is formed by linear combinations of these explicit end members. Approximately 950 published X-ray diffraction experiments performed on garnets at ambient and in situ high-P, T conditions are used to calibrate end-member equations of state and an excess volume model for this system. Optimal values of the bulk modulus and its pressure derivative are obtained by analyzing published compression and/or ultrasonic data for the end members for which such studies exist; for other end members, density functional theory results are used. For any cubic garnet in this chemical system, the model molar volume is obtained by adding excess volume terms to a linear combination of the nine independent end-member volumes. In the first step of our least squares fitting procedure we calculate volumes of the explicit end members as a function of P and T using the high-T Vinet equation of state. We allow standard state volumes and coefficients of thermal expansion to vary for those independent end members where pure compositional data exist, either for the phase itself or for an appropriate dependent end member. For each dependent end member for which there are data, we calculate the volume of reaction for formation of the phase from the independent end members, ?V. We then fit the binary and mixed composition data, using the singular value analysis method of Lawson & Hanson (1974) to ensure that the calibrated combinations of excess parameters obey the nine ?V constraints from the first step. A key plausibility check on the model results from comparing the predicted T-dependence of the bulk modulus to high-T ultrasonic results that were not used in the calibration. The calculated pressure of the spinel-garnet transition using the new volume models is compared to that obtained with the previous models. The implications our model has for the density of the lithospheric mantle are explored.
Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.
The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.
Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C. [Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering; Carleton, R.L.; George, E.P. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
Optical properties of Fe-doped silica films on Si
NASA Astrophysics Data System (ADS)
Optical properties of Fe-doped silica films on Si were investigated by ellipsometric technique in the region 1-5 eV. Samples were produced by sol-gel method. Precursors were prepared by mixing tetraethoxysilane (TEOS) solution in ethanol and water with aqueous solution of Fe-chloride or Fe-acetate. The coating solution was deposited on Si substrates by spin on technique. The size of Fe-containing nanometric-sized particles depended on technology and varied from 20 to 100 nm. Optical response of complex hybrid samples SiO 2:Fe/Si was interpreted in a multi-layer model. In the inverse problem, the Maxwell equations were solved by transfer matrix technique. Dielectric function of Fe-doped silica layers was calculated in the model of effective media. Analysis of optical data has shown that various Fe-oxides formed. Experimental data for films obtained from precursors with Fe-acetate and annealed in hydrogen were well described by the model calculations taking into account a small contribution 1-5% of metal Fe imbedded in silica. The Fe/Fe-O contribution to optical response increased for samples grown from FeCl 3-precursor. Ellipsometric data for Fe-doped silica films on Si were interpreted taking into account the structural AFM studies as well as the results of magnetic measurements.
Babonas, G. J.; Reza, A.; Simkiene, I.; Sabataityte, J.; Baran, M.; Szymczak, R.; Karlsson, U. O.; Suchodolskis, A.
Magnetic properties and high frequency characteristics of sputtered FeAl and FeAlB
The magnetic properties and high frequency characteristics of sputtered Fe81Al19 and Fe81Al10B9 thin films have been investigated. The above two thin films were sputtered at different oblique deposition angles in order to induce magnetic anisotropy in the film. The saturation magnetization of the films is easily above 12 kG, while the coercivity and the magnetic anisotropy field of the films
C. C. Hsieh; M. Y. Jian; H. W. Chang; X. G. Zhao; W. C. Chang
National Technical Information Service (NTIS)
The glass-forming region at 1650 deg C was investigated for Mg-Si-Al-O-N compositions containing up to 20 equivalent % N (16 atomic %), and glass batches of up to 30 g were prepared and characterized. Glasses containing up to 8 atomic % N were grey colore...
D. R. Messier R. P. Gleisner
Synthesis and performance of Ca-?/?-SiAlON composites from tailings
NASA Astrophysics Data System (ADS)
Ca-?/?-SiAlON composites were prepared using Ca-?/?-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520°C for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-?-SiAlON): I(?-SiAlON): I(Fe3Si) = 23:74:3, where I i stands for the diffraction peak intensity of phase i.
Hao, Hong-shun; Yang, Yang; Lian, Fang; Gao, Wen-yuan; Liu, Gui-shan; Hu, Zhi-qiang
Thermodynamic modeling of non-ideal mineral fluid equilibria in the system Si Al Fe Mg Ca Na K H O Cl at elevated temperatures and pressures: Implications for hydrothermal mass transfer in granitic rocks
NASA Astrophysics Data System (ADS)
We present the results of thermodynamic modeling of fluid-rock interaction in the system Si-Al-Fe-Mg-Ca-Na-H-O-Cl using the GEM-Selektor Gibbs free energy minimization code. Combination of non-ideal mixing properties in solids with multicomponent aqueous fluids represents a substantial improvement and it provides increased accuracy over existing modeling strategies. Application to the 10-component system allows us to link fluid composition and speciation with whole-rock mineralogy, mass and volume changes. We have simulated granite-fluid interaction over a wide range of conditions (200-600 °C, 100 MPa, 0-5 m Cl and fluid/rock ratios of 10 -2-10 4) in order to explore composition of magmatic fluids of variable salinity, temperature effects on fluid composition and speciation and to simulate several paths of alteration zoning. At low fluid/rock ratios ( f/ r) the fluid composition is buffered by the silicate-oxide assemblage and remains close to invariant. This behavior extends to a f/ r of 0.1 which exceeds the amount of exsolved magmatic fluids controlled by water solubility in silicate melts. With increasing peraluminosity of the parental granite, the Na-, K- and Fe-bearing fluids become more acidic and the oxidation state increases as a consequence of hydrogen and ferrous iron transfer to the fluid. With decreasing temperature, saline fluids become more Ca- and Na-rich, change from weakly acidic to alkaline, and become significantly more oxidizing. Large variations in Ca/Fe and Ca/Mg ratios in the fluid are a potential geothermometer. The mineral assemblage changes from cordierite-biotite granites through two-mica granites to chlorite-, epidote- and zeolite-bearing rocks. We have carried out three rock-titration simulations: (1) reaction with the 2 m NaCl fluid leads to albitization, chloritization and desilication, reproducing essential features observed in episyenites, (2) infiltration of a high-temperature fluid into the granite at 400 °C leads to hydrolytic alteration commencing with alkali-feldspar breakdown and leading to potassic, phyllic and argillic assemblages; this is associated with reduction and iron metasomatism as observed in nature and (3) interaction with a multicomponent fluid at 600 °C produces sodic-calcic metasomatism. Na, Ca and Fe are the most mobile elements whereas immobility of Al is limited by f/ r ˜ 400. All simulations predict a volume decrease by 3.4-5.4%, i.e., porosity formation at f/ r < 30. At higher fluid/rock ratios simulation (2) produces a substantial volume increase (59%) due to mineral precipitation, whereas simulation (3) predicts a volume decrease by 49% at the advanced albitization-desilication stage. Volume changes closely correlate with mass changes of SiO 2 and are related to silica solubility in fluids. The combined effects of oxygen fugacity, fluid acidity and pH for breakdown of aqueous metal complexes and precipitation of ore minerals were evaluated by means of reduced activity products. Sharp increases in saturation indexes for oxidative breakdown occur at each alteration zone whereas reductive breakdown or involvement of other chloride complexes favor precipitation at high fluid/rock ratios only. Calculations of multicomponent aqueous-solid equilibria at high temperatures and pressures are able to accurately predict rock mineralogy and fluid chemistry and are applicable to diverse reactive flow processes in the Earth's crust.
Dolejš, David; Wagner, Thomas
Interaction of Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC\\/Al discontinuously reinforced metal matrix composites
Interactions between Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC whisker-reinforced aluminium metal matrix composites were studied as a function of temperature above the eutectic melting temperature. Penetration extended several millimetres into the composite for the Al-Si and Al-Ge alloys but was restricted to a thin surface layer (50 µm) for the Zn-Al alloy. The extent of the penetration zone
W. C. Moshier; J. S. Ahearn; D. C. Cooke
Epitaxial Growth of Ferromagnetic Fe3Si Films on CaF2/Si(111) by Molecular Beam Epitaxy
NASA Astrophysics Data System (ADS)
Ferromagnetic Fe3Si/CaF2 hybrid structures were epitaxially grown on Si(111) by molecular beam epitaxy. When Si and Fe were directly deposited on the Si substrate, it was difficult to prevent inclusion of FeSi in the grown films. This problem was overcome by forming a CaF2 epitaxial film on Si(111) first, followed by codeposition of Si and Fe to form Fe3Si. Fe3Si films were epitaxially grown on the CaF2 at 400°C. A distinct square-like hysteresis loop was observed at room temperature in the magnetic field dependence of Kerr rotation.
Sunohara, Tsuyoshi; Kobayashi, Ken'ichi; Umada, Masakazu; Yanagihara, Hideto; Kita, Eiji; Akinaga, Hiroyuki; Suemasu, Takashi
The rate of reaction of solid iron with oxidized ``FeO''-CaO-SiO2-Al2O3 slags at 1360 °C—the chemical diffusivity of iron oxide
NASA Astrophysics Data System (ADS)
Measurements have been made of the rate of reduction of oxidized iron oxide-containing 41CaO-38SiO2-21Al2O3 (wt pct) slags at 1360 °C by a rotating disc of solid iron. For initial total iron concentrations of between 1.8 and 13.4 wt pct and rotation speeds up to 1000 rpm, the rate is shown to be determined by mass transfer in the liquid phase. The chemical diffusivity of iron oxide (in cm2 s-1) is found to be given by the empirical expression log D = -6.11 + 0.08 (wt pct Fe). It is concluded that the values of the diffusivity are for melts at close to iron saturation. It is shown that the available measurements of the diffusivity of iron oxide in liquid slags are consistent with increasing diffusivity with increasing state of oxidation, with about a tenfold increase between melts in equilibrium with iron and those in equilibrium with oxygen at 1 atm.
Xie, D.; Belton, G. R.
Thermodynamic and physical properties of FeAl and Fe3Al: an atomistic study by EAM simulation
NASA Astrophysics Data System (ADS)
With this work we present a newly developed potential for the Fe-Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D03-Fe3Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D03-Fe3Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe-Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe-Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe-Al system.
Ouyang, Yifang; Tong, Xiaofeng; Li, Chang; Chen, Hongmei; Tao, Xiaoma; Hickel, Tilmann; Du, Yong
Strip casting of Al-25%Si strip was tried using an unequal diameter twin roll caster. The diameter of the lower roll (large roll) was 1000 mm and the diameter of the upper roll (small roll) was 250 mm. Roll material was mild steel. The sound strip could be cast at the speeds ranging from 8 m/min to 12 m/min. The strip did not stick to the roll without the parting material. The primary Si, which existed at centre area of the thickness direction, was larger than that which existed at other area. The size of the primary Si was smaller than 0.2 mm. Eutectic Si was smaller 5 {mu}m. The as-cast strip was ranging from 2 mm to 3 mm thick and its width was 100 mm. The as-cast strip could be hot rolled down to 1 mm. The hot rolled strip was cold rolled. The primary Si became smaller and the pore occurred around the primary Si after the rolling.
Haga, Toshio [Osaka Institute of Technology, Omiya Asahiku Osaka city 535-8585 (Japan); Harada, Hideto [Graduate School of Osaka Institute of Technology, Omiya Asahiku Osaka city 535-8585 (Japan); Watari, Hisaki [Gunma University, Kiryu city, 376-8515 (Japan)
The erosion–corrosion behavior of some Fe 3Al-based alloys at high temperatures
The erosion–corrosion tests of some Fe3Al-based alloys were carried out in an elevated temperature erosion tester. In this facility, solid particle (SiO2) and corrosive gas (SO2) were fed into oil-fired gas by the feed subsystems, respectively. The test specimens were impacted in the temperature range of 600–800°C. Erosion–corrosion behavior of Fe3Al-based alloys was compared with that of Ni and Co
X. Q Yu; M Fan; Y. S Sun
Sliding wear behavior of some Al-Si alloys: Role of shape and size of Si particles and test conditions
In this investigation, effects of the shape and size of silicon particles have been studied on the sliding wear response of\\u000a two Al-Si alloys, namely, LM13 and LM29. The LM13 alloy comprised 11.70 pct Si, 1.02 pct Cu, 1.50 pct Ni, 1.08 pct Mg, 0.70\\u000a pct Fe, 0.80 pct Mn, and remainder Al. The LM29 alloy contained 23.25 pct Si,
B. K. Prasad; K. Venkateswarlu; O. P. Modi; A. K. Jha; S. Das; R. Dasgupta; A. H. Yegneswaran
Phase relations and physical properties of Fe2SiO4-Fe3O4 solid solution under pressures up to 12 GPa
NASA Astrophysics Data System (ADS)
Phase study of the Fe2SiO4-Fe3O4 solid solution system has been carried out under high pressures up to 12 GPa at 1200°C by multianvil apparatus. A complete spinel solid solution between Fe304 and ?-Fe2Si04 has been found at pressures over 10 GPa. ?-Fe2Si04 with a normal spinel structure is stable at pressures above 7 GPa. A spinelloid structure similar to aluminosilicate V (Pmma) in the NiAl2O4-Ni2SiO4 system is found in a wide intermediate compositional range x=0.37 to 0.73 in Fe3-xSixO4 at pressures between 3 and 9 GPa. X ray single-crystal structure analyses of several samples of Fe3-xSixO4 spinel indicate the site occupancy of (Fe3+1-x+ySi4+x-y) [Fe2+1+xFe3+1-x-ySi4+y]O4. This cation distribution affects the electrical conductivity mainly because of the electron hopping between Fe3+ and Fe2+ in the octahedral site. Measurement of the electrical conductivity of the spinel solid solution has been made at low temperatures in the range 80 to 300 K. The transition temperature of the Verwey order between Fe3+ and Fe2+ decreases with the Si content in Fe3-xSix04 and the energy gap becomes smaller with Si.
Yamanaka, T.; Tobe, H.; Shimazu, T.; Nakatsuka, A.; Dobuchi, Y.; Ohtaka, O.; Nagai, T.; Ito, E.
Elastic anisotropy of FeSiO3 end-members of the perovskite and post-perovskite phases
The athermal elastic constants of the perovskite and post-perovskite polymorphs of pure end-member FeSiO3 were calculated from ab initio calculations. We predict that incorporating ten mole percent FeSiO3 together with four mole percent Al2O3 into MgSiO3 reduces the perovskite to post-perovskite phase transition pressure by 5 GPa. Small changes in the seismic properties of the post-perovskite phase due to the
Stephen Stackhouse; John P. Brodholt; G. David Price
Microstructure and properties of Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites formed by in situ reaction of Al with aluminosilicate ceramics
Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites have been formed by in situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce {alpha}-Al{sub 2}O{sub 3} and elemental Si. With excess Al (i.e., x > 0), a composite of {alpha}-Al{sub 2}O{sub 3}, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young`s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites produced by in situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content.
Ewsuk, K.G.; Glass, S.J.; Loehman, R.E. [Sandia National Labs., Albuquerque, NM (United States); Tomsia, A.P. [Lawrence Berkeley Lab., CA (United States); Fahrenholtz, W.G. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemical and Nuclear Engineering
Measurement and Modeling of the Production of He, Ne, and AR from Mg, Al, Si, Fe, and NI in an Artificial Iron Meteoroid Irradiated Isotropically with 1.6 GeV Protons
NASA Astrophysics Data System (ADS)
The production by GCR protons of He, Ne and Ar isotopes from their main target elements was investigated in a simulation experiment [1] by irradiating a 20-cm diameter iron sphere isotropically with 1.6 GeV protons. The model-meteoroid contained, among other targets, pure Mg, Al, Si, Fe, and Ni foils at various depths in central bores. Radionuclide production in these targets was measured by gamma-spectrometry. Stable He, Ne, and Ar isotopes were measured by mass spectrometry. These latter results and the ^22Na data are reported here. As in our earlier simulation with a 50-cm diameter gabbro sphere irradiated with 1.6 GeV protons [2], the present experiment simulates the exposure of meteoroids to galactic protons in space within about 20%, if normalized to the same number of particles. Some systematic deviations are attributed to differences between the monoenergetic irradiation and the exposure to the GCR spectrum and to resulting differences between the secondary particle fields. A comparison of the new production rates with those obtained in the gabbro sphere [2] clearly exhibits the influence of bulk chemical composition on production rates which was discovered earlier by Begemann and Schultz [3] in stony irons. Model calculations of the production of He, Ne, Ar, and ^22Na were performed for all artificial iron and stony meteoroids irradiated by our collaboration [2, 4, 5, this work]. Production rates were calculated from depth-dependent p- and n-spectra derived by Monte Carlo techniques using the HERMES code system [6] and from cross sections for the relevant nuclear reactions. For p-induced reactions all available experimental thin-target cross sections were used [2]. Cross sections for n-induced reactions were calculated by the new AREL code [7] which is a relativistic version of the hybrid model of preequilibrium reactions [8]. In addition to these a priori calculations a posteriori model calculations were performed. Theoretical cross sections for n-induced reactions were improved by a least square fitting procedure adjusting the calculated production rates to all experimental ones from the simulation experiments. The simultanous interpretation of rare gas production rates measured in artificial meteoroids of different radii and bulk chemical composition irradiated by 600 MeV and 1.6 GeV protons results in an improved set of neutron cross sections. The new experimental production rates provide a basis for validation of model calculations of rare gas production in all types of extraterrestrial matter. In particular, they allow to validate model calculations of the matrix effect [9, 10] on the basis of laboratory data obtained under controlled conditions. Production rates in stony and iron meteoroids are consistently described by a physical model without free parameters. Acknowledgments: This work was supported by the Swiss National Science Foundation. References: [1] Michel R. et al. (1993) Meteoritics, 28, 399-400. [2] Wieler R. et al. (1992) Meteoritics, 27, 315-316. [3] Begemann F. and Schultz L. (1988) LPS XIX, 51-52. [4] Michel R. et al. (1986) Nucl. Instr. Meth. Phys. Res., B16, 61-82. [5] Michel R. et al. (1989) Nucl. Instr. Meth. Phys. Res., B42, 76-100. [6] Cloth P. et al. (1988) Juel 2203. [7] Blann M. (1994) personal communication. [8] Blann M. (1972) Phys. Rev. Lett., 28, 757-759. [9] Michel et al. (1990) Meteoritics, 25, 386-387. [10] Masarik J. et al. (1994) GCA, 58, 5307-5317.
Busemann, H.; Wieler, R.; Leya, I.; Lange, H.-J.; Michel, R.; Meltzow, B.; Herpers, U.
Soft magnetic powder-core composites of Fe{sub 90}Zr{sub 7}B{sub 3} and Fe{sub 49}Co{sub 21}Al{sub 5}Ga{sub 2}P{sub 9.65}C{sub 5.75}B{sub 4.6}Si{sub 3} alloys
Amorphous and nanocrystalline alloys in ribbon form exhibit excellent soft magnetic properties, but their forms are limited to tape wound cores. Complex shapes require the implementation of a powder metallurgical approach resulting in reduced permeabilities. The present study investigates Fe-based Fe{sub 90}Zr{sub 7}B{sub 3} (C1) and Fe{sub 49}Co{sub 21}Al{sub 5}Ga{sub 2}P{sub 9.65}C{sub 5.75}B{sub 4.6}Si{sub 3} (C2) melt-spun ribbons as precursors for compacted powder cores. Single-roller melt spinning of C1 produced partially crystallized structures while C2 resulted in amorphous ribbons. Annealing studies were carried out based on the crystallization temperatures of various phases extracted from M(T) measurements. In ribbon form and under optimum annealing conditions, C1 revealed a 1.88 T saturation flux density (B{sub s}) and 44 A/m coercivity (H{sub c}), while C2 exhibited a B{sub s} of 0.78 T and H{sub c} of 2.4 A/m.
Turgut, Zafer; Attenweiler, Thomas; Huang, Meiqing; Horwath, John C.; Fingers, Richard T. [UES Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432 (United States); AFRL, Wright-Patterson AFB, Ohio 45433-7251 (United States); UES Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432 (United States); AFRL, Wright-Patterson AFB, Ohio 45433-7251 (United States)
Nanocrystallization mechanism of amorphous Fe78B13Si9
NASA Astrophysics Data System (ADS)
The nanocrystallization mechanism of an amorphous alloy is discussed based on the kinetics of open nanospaces in Fe78B13Si9. There already exists a high concentration of Fe-enriched fluctuated sites with open nanospaces in the amorphous matrix. The structural and compositional fluctuation helps transient short-range Fe diffusion in the metastable amorphous matrix with an increase of temperature, triggering highly concentrated ?-Fe nucleation. Along with the growth of ?-Fe nucleus, Fe atoms are transferred from the intergranular amorphous phase to Fe-based nanocrystallites. The nanocrystallization of ?-Fe is achieved through nucleation by short-range Fe diffusion and its growth by nanovoid-mediated long-range Fe diffusion.
Sato, K.; Murakami, H.; Sprengel, W.; Schaefer, H.-E.; Kobayashi, Y.
Localized Corrosion Behavior of Al-Si-Mg Alloys Used for Fabrication of Aluminum Matrix Composites
NASA Astrophysics Data System (ADS)
The relationship between microstructure and localized corrosion behavior in neutral aerated chloride solutions was investigated with SEM/EDAX, conventional electrochemical techniques, and with scanning Kelvin probe force microscopy (SKPFM) for two custom-made alloys with Si/Mg molar ratios of 0.12 and 0.49. In this order, Al3Fe, Al3Mg2, and Mg2Si intermetallics were identified in the first alloy and Al(FeMn)Si and Mg2Si particles in the second one. Anodic polarization curves and corrosion morphology showed that the alloy with higher Si/Mg molar ratio exhibited a better corrosion performance and evidence was shown that it had a more corrosion-resistant passive film. The corrosion process for both alloys in aerated 0.1 M NaCl solutions was localized around the Fe-rich intermetallics. They acted as local cathodes and produced dissolution of the aluminum matrix surrounding such particles. Mg2Si and Al3Mg2 exhibited anodic behavior. SKPFM was successfully used to map the Volta potential distribution of main intermetallics. The localized corrosion behavior was correlated with a large Volta potential difference between the Fe-rich intermetallics and the matrix. After immersion in the chloride solution, such Volta potential difference decreased.
Pech-Canul, M. A.; Giridharagopal, R.; Pech-Canul, M. I.; Coral-Escobar, E. E.
Separation and purification of Si from solidification of hypereutectic Al-Si melt under rotating magnetic field
NASA Astrophysics Data System (ADS)
A low-cost and high-efficiency method to purify Si directly from cheap MG-Si at low temperature was proposed and demonstrated in this paper, which used power frequency rotating magnetic field (RMF) to separate the primary Si from a hypereutectic Al-Si alloy and was followed by the acid peeling. The separation mechanism was based on the flow characteristic of melt under RMF and the cooling condition of the liquid metal. A Si-rich layer with Si content of 65-59 wt% was formed in the periphery of alloy, while the inner microstructure of the alloy was mainly the Al-Si eutectic structure. The refined silicon was collected after aqua regia leaching, and had much fewer typical impurities (Fe, Ti, Ca, B, P) than those in MG-Si, and the metallic impurities besides Al had removal fraction higher than 98%, which is mainly ascribed to the segregation effect of Al-30Si alloy during solidification under RMF.
Jie, J. C.; Zou, Q. C.; Wang, H. W.; Sun, J. L.; Lu, Y. P.; Wang, T. M.; Li, T. J.
Itinerant Electron Ferromagnetism in Fe1-xCoxSi Studied by Polarized Neutron Diffraction
NASA Astrophysics Data System (ADS)
Polarized neutron diffraction and magnetic measurement have been carried out on single crystal samples of solid solutions Fe1-xCoxSi. The result of magnetic measurement shows that this alloy has a lot of features of itinerant electron ferromagnet i.e. low TC, small magnetization, large value of ?C/?s. The spin density map of Fe0.6Co0.4Si is composed of the two kinds of magnetic moments, those are, a 3d-like moment localized on the (Fe, Co) site (?3d) and a weak negative magnetic moment diffused over the crystal (?dif). The magnetic moments are estimated to be ?3d{=}0.263± 0.014?B/(Fe, Co) atom and ?dif{=}-0.046± 0.014?B/F.U. These results are discussed with those of typical itinerant electron ferromagnets ZrZn2, Ni3Al and MnSi.
Ishimoto, Kenichi; Ohashi, Masayoshi; Yamauchi, Hiroshi; Yamaguchi, Yasuo
The {beta}-Ti(Al,Si) + Ti{sub 5}(Si,Al){sub 3} eutectic reaction in the Ti-Al-Si ternary system
Dual phase alloys Ti + Ti{sub 5}Si{sub 3} or Ti{sub 3}Al + Ti{sub 5}(Si,Al){sub 3} are recently of special interest, due to their probable high performance at elevated temperatures. In 1988, a eutectic line of Ti{sub 3}(Al,Si) + Ti{sub 5}(Si,Al){sub 3} was first established in a Ti-rich portion of the Ti-Al-Si system, and was further reported in the following years. However, the reported line only covered a limited range in the Ti-Al-Si ternary system; thus, extensive study over a wider range in the ternary phase diagram is necessary. In the present paper, the details of the {beta}-Ti(Al,Si) + Ti{sub 5}(Si,Al){sub 3} eutectic line, ranging from 0 at% Al to 40 at% Al will be reported, together with the melting temperatures and the microstructures of the eutectic alloys. It is suggested that the eutectic line in this paper means the liquidus valley between {beta}-Ti-rich liquidus surface and Ti{sub 5}Si{sub 3}-rich liquidus surface, while the eutectic microstructure, here, means the coupled-growth microstructure solidified along this liquidus valley.
Wu, J.; Qiu, G.; Zhang, L. [Shanghai Jiao Tong Univ. (China). Dept. of Materials Science] [Shanghai Jiao Tong Univ. (China). Dept. of Materials Science
A Thermodynamic Model of Phosphorus Distribution Ratio between CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 Slags and Molten Steel during a Top-Bottom Combined Blown Converter Steelmaking Process Based on the Ion and Molecule Coexistence Theory
NASA Astrophysics Data System (ADS)
A thermodynamic model for calculating the phosphorus distribution ratio between top-bottom combined blown converter steelmaking slags and molten steel has been developed by coupling with a developed thermodynamic model for calculating mass action concentrations of structural units in the slags, i.e., CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 slags, based on the ion and molecule coexistence theory (IMCT). Not only the total phosphorus distribution ratio but also the respective phosphorus distribution ratio among four basic oxides as components, i.e., CaO, MgO, FeO, and MnO, in the slags and molten steel can be predicted theoretically by the developed IMCT phosphorus distribution ratio prediction model after knowing the oxygen activity of molten steel at the slag-metal interface or the Fe t O activity in the slags and the related mass action concentrations of structural units or ion couples in the slags. The calculated mass action concentrations of structural units or ion couples in the slags equilibrated or reacted with molten steel show that the calculated equilibrium mole numbers or mass action concentrations of structural units or ion couples, rather than the mass percentage of components, can present the reaction ability of the components in the slags. The predicted total phosphorus distribution ratio by the developed IMCT model shows a reliable agreement with the measured phosphorus distribution ratio by using the calculated mass action concentrations of iron oxides as presentation of slag oxidation ability. Meanwhile, the developed thermodynamic model for calculating the phosphorus distribution ratio can determine quantitatively the respective dephosphorization contribution ratio of Fe t O, CaO + Fe t O, MgO + Fe t O, and MnO + Fe t O in the slags. A significant difference of dephosphorization ability among Fe t O, CaO + Fe t O, MgO + Fe t O, and MnO + Fe t O has been found as approximately 0.0 pct, 99.996 pct, 0.0 pct, and 0.0 pct during a combined blown converter steelmaking process, respectively. There is a great gradient of oxygen activity of molten steel at the slag-metal interface and in a metal bath when carbon content in a metal bath is larger than 0.036 pct. The phosphorus in molten steel beneath the slag-metal interface can be extracted effectively by the comprehensive effect of CaO and Fe t O in slags to form 3CaO·P2O5 and 4CaO·P2O5 until the carbon content is less than 0.036 pct during a top-bottom combined blown steelmaking process.
Yang, Xue-Min; Duan, Jian-Ping; Shi, Cheng-Bin; Zhang, Meng; Zhang, Yong-Liang; Wang, Jian-Chang
The self diffusion of iron in Fe 2 SiO 4 and CaFeSiO 4 melts
The self diffusion of iron in Fe2SiO4 and CaFeSiO4 melts has been measured in the temperature range 1250° to 1540°C using Fe59 as the radio tracer and the capillary-liquid reservoir method of diffusion measurement. The results obtained are represented\\u000a by\\u000a \\u000a \\u000a \\u000a \\u000a $$log D_{Fe} = - \\\\frac{{3800 \\\\pm 500}}{T} - 2.74 \\\\pm 0.29$$\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a for Fe2SiO4, and\\u000a \\u000a \\u000a \\u000a \\u000a $$log D_{Fe} = - \\\\frac{{5450 \\\\pm
D. P. Agarwal; D. R. Gaskell
Tensile Behavior of Al2O3/FeAl + B and Al2O3/FeCrAlY Composites
NASA Technical Reports Server (NTRS)
The feasibility of Al2O3/FeAl + B and Al2O3/FeCrAlY composites for high-temperature applications was assessed. The major emphasis was on tensile behavior of both the monolithics and composites from 298 to 1100 K. However, the study also included determining the chemical compatibility of the composites, measuring the interfacial shear strengths, and investigating the effect of processing on the strength of the single-crystal Al2O3 fibers. The interfacial shear strengths were low for Al203/FeAl + B and moderate to high for Al203/FeCrAlY. The difference in interfacial bond strengths between the two systems affected the tensile behavior of the composites. The strength of the Al203 fiber was significantly degraded after composite processing for both composite systems and resulted in poor composite tensile properties. The ultimate tensile strength (UTS) values of the composites could generally be predicted with either rule of mixtures (ROM) calculations or existing models when using the strength of the etched-out fiber. The Al2O3/FeAl + B composite system was determined to be unfeasible due to poor interfacial shear strengths and a large mismatch in coefficient of thermal expansion (CTE). Development of the Al2O3/FeCrAlY system would require an effective diffusion barrier to minimize the fiber strength degradation during processing and elevated temperature service.
Draper, S. L.; Eldridge, J. I.; Aiken, B. J. M.
Disorder-induced reversal of spin polarization in the Heusler alloy Co{sub 2}FeSi
We study the spin polarization in the conduction band of Co{sub 2}FeSi layers with a different degree of structural order. The injected spin polarization in Co{sub 2}FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co{sub 2}FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered L2{sub 1} phase and the Fe-Si disordered B2 phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co{sub 2}FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.
Bruski, P.; Ramsteiner, M.; Brandt, O.; Friedland, K.-J.; Farshchi, R.; Herfort, J.; Riechert, H. [Paul-Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Erwin, S. C. [Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375 (United States)
Development of SiAlON materials
NASA Technical Reports Server (NTRS)
Cold pressing and sintering techniques were used to produce ceramic bodies in which the major phase was beta prime Si3-Al-O-N4 solid solution. A variety of foreign oxides were used to promote liquid phase sintering, and this resulted in the incorporation of additional solid phases in the ceramic bodies which controlled elevated temperature properties. None of the bodies studied to date exhibited both adequate high temperature mechanical properties and oxidation resistance. Criteria are suggested to guide the formulation of bodies with improved high temperature properties.
Layden, G. K.
High Pressure Melting, Phase Diagrams, and Equations of State in the Fe-FeSi System with Application to Earth's Core
NASA Astrophysics Data System (ADS)
The Earth's core is comprised mostly of iron, with some nickel and several weight percent of one or more light elements. The light element(s) dictate phase relations, structure, and dynamic behaviour, so it is crucial to evaluate various candidates at conditions of planetary interiors. We present results on high P-T phase diagrams and equations of state in the Fe-FeSi system with application to the structure and composition of Earth's core. X-ray diffraction measurements were performed on stoichiometric FeSi and on Fe-Si alloys containing 9 and 16 wt% silicon in a laser-heated diamond anvil cell at the APS, NSLS, and ALS. Pressures were determined from the lattice parameter of KBr. We have investigated the phase diagram of Fe-9Si to 100 GPa and over 3000 K. Our melting curve agrees with previous results on similar alloys [1,2], as demonstrated using multiple methods of detecting melting. Our subsolidus results are similar to those of Lin et al. [3], though we find the B2 structure instead of bcc, and a shallower slope for the hcp+B2 to fcc+B2 boundary. We studied phase relations of Fe-16Si to over 135 GPa, finding agreement with previous melting curves [2,4]. Below 45 GPa, this alloy has the D0_3 structure. At high pressures, Fe-16Si breaks down into a mixture of B2 and hcp phases, with this mixture stable to pressures of the Earth's outer core. This is the first study on the B2 phase of FeSi with in situ X-ray diffraction at high pressures and temperatures. We report a wide B2+B20 two-phase field in FeSi, with complete conversion to the B2 structure by ~42 GPa. A melting experiment on FeSi agrees with the results of Lord et al. [5]. We have synthesized our results with previous studies to construct T-X and P-X phase diagrams, and we have determined thermal equations of state of each alloy. Our measured densities can be used to constrain the maximum amount of silicon in the Earth's outer core by comparison to the equation of state of hcp-Fe [6] and the seismologically-determined density. Assuming a core-mantle boundary (CMB) temperature of 4000 +/- 500 K and a 1-2% density decrease upon melting, the amount of silicon in the outer core required to match PREM at the CMB is 11.3 +/- 1.5 weight percent, under the simplifying assumption of a purely Fe-Ni-Si outer core. The minimum temperature of an Fe-Si outer core is 4380 K, based on the eutectic melting point of Fe-FeSi alloys, and silicon is shown not to significantly depress the melting point of iron at core conditions. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe-FeSi system. We predict that alloys containing more than ~4-8 wt% Si will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron-silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases. [1] Kuwayama and Hirose (2004) Am Mineral 89, 273-276 [2] Morard et al. (2011) PCM 38, 767-776 [3] Lin et al (2002) Science 295, 313-315 [4] Asanuma et al. (2010) PCM 37, 353-359 [5] Lord et al. (2010) JGR 115, B06208 [6] Dewaele et al. (2006) PRL 97, 215504
Fischer, R. A.; Campbell, A. J.; Reaman, D. M.; Heinz, D. L.; Dera, P. K.; Prakapenka, V.
Electron-conduction properties of Fe-Al alloy nanowires.
Helical and nonhelical shell structures of Fe-Al alloy nanowires are obtained using molecular dynamics (MD) and density functional theory (DFT) calculations. The electrical transport properties of alloy nanowires are investigated and compared with those of pure metallic aluminum and iron nanowires. The calculations indicate that the conductance of the Fe-Al alloy nanowire is less than that of the pure Al or Fe nanowires. The results show that the conductance of a carbon-coated Fe-Al alloy nanowire (28,7) is significantly larger than that of Fe-Al alloy nanowire. The difference in the electrical behavior of the Fe-Al alloy nanowire and the carbon-coated structure can be attributed to the two interfering pathways between the CNT and the alloy nanowire. The nonlinear feature of the current-voltage (I-V) for all alloy nanowires suggests that it does not follow the Ohmic pattern. PMID:19367947
Li, H; Liew, K M; Zhang, X Q; Zhang, J X; Liu, X F; Bian, X F
Effect of Fe content on the mechanical alloying and mechanical properties of Al-Fe alloys
Al-Fe alloys with Fe contents ranging from 5 to 12 wt% are produced by a double mechanical alloying process (DMA) which consists of a first step of mechanical alloying (MA1) applied to elemental Al and Fe powders, with subsequent heat treatment of MA1 powders to promote the formation of Al-Fe intermetallic phases, and a second mechanical alloying step (MA2) to
X. P. Niu; L. Froyen; L. Delaey; C. Peytour
Solid State Synthesis of Fe-B-Si Alloys.
National Technical Information Service (NTIS)
Fe-B and Fe-B-Si elemental and intermetallic powders were synthesized by the mechanical alloying method. Vibratory and planetary type of ball mills were used. The alloying time and the alloying type in the results were investigated. The microstructure and...
P. Ruuskanen O. Heczko
Solid State Synthesis of Fe-B-Si Alloys.
National Technical Information Service (NTIS)
Fe-B and Fe-B-Si elemental and intermetallic powders were synthesized by mechanical alloying method. Vibratory and planetary type of ball mills were used in the tests. The alloying time and the alloying type in the results were investigated. The microstru...
P. Ruuskanen O. Heczko
Noncentrosymmetric cubic helical ferromagnets Mn1 - y Fe y Si and Fe1 - x Co x Si
NASA Astrophysics Data System (ADS)
Two systems of noncentrosymmetric cubic helical magnets Mn1 - y Fe y Si ( y = 0.06, 0.08, 0.10) and Fe1 - x Co x Si ( x = 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.50) have been compared. The concentration dependences of the critical temperature and magnetic field have been obtained using small-angle polarized-neutron scattering and analyzed in the framework of the Bak-Jensen model. It has been established that, among the two interactions that play the main role in these systems, i.e., the isotropic symmetric ferromagnetic exchange and the Dzyaloshinskii-Moriya isotropic antisymmetric interaction, the former interaction determines the critical temperature in the Mn1 - y Fe y Si system and the latter interaction determines this temperature in the Fe1 - x Co x Si system.
Grigoriev, S. V.; Dyadkin, V. A.; Maleyev, S. V.; Menzel, D.; Schoenes, J.; Lamago, D.; Moskvin, E. V.; Eckerlebe, H.
Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family
A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.
Rastsvetaeva, R. K., E-mail: email@example.com; Aksenov, S. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
Natural Occurrence of Fe2SiO4 - in Shocked Umbarger l6 Chondrite
NASA Astrophysics Data System (ADS)
Fe2SiO4 with the spinel structure was synthesized by Ringwood [1] and inferred to be important in Earth's upper mantle [1,2], but it has not previously been found in nature. Umbarger is an L6 chondrite, which contains a series of high-pressure phases: ring-woodite, akimotoite, augite and hollandite-structured plagioclase [3-6]. Transmission electron microscopy also revealed a Fe2SiO4-spinel and stishovite assem-blage in a Fe-rich zone of a melt pocket. Phyllosili-cates and glass are also associated with the Fe2SiO4-spinel, indicating post-shock aqueous glass alteration. The Fe2SiO4-spinel grains are equant to irregular, with sizes from 100 to 400 nm. Diffraction patterns can only be indexed as a spinel structure, but the unit cell is a little large (a= 8.46 Å) relative to synthetic Fe2SiO4-spinel (a=8.234 Å [1]). EDS analyses show that the spinel has a fayalite compositon with Fe/(Fe+Mg) ratio ranging from 62% to 97%. Stishovite occurs as elongated prismatic crystals up to 1 mm long and up to 100 mm wide. The alteration products in Umbarger are phyllosilicates rich in Fe and Si, with a basal layer spacing of about 9.7 Å. Crystallization of melt veins began with akimotoite and ringwoodite at pressures up to 25 GPa and ended with augite at pressure less than 18 GPa [3, 4]. Mg2SiO4-spinel and stishovite are stable in the pres-sure range from 15 GPa to 25 GPa in the enstatite-forsterite system [7], while Fe2SiO4-spinel and stishovite is stable at lower pressure. Fe2SiO4-spinel and stishovite assemblage, like that of Akimotoite plus ringwoodite, is a sub-solidus assemblage, indicating crystallization of a supercooled liquid during rapid cooling and decompression associated with shock pres-sure release. Reference: [1] Ringwood A.E. (1958) GCA,15, 18-29. [2] Irifune T. (1993) The Island Arc, 2, 55-71. [3] Xie Z. and Sharp T. G. (2000a) LPS XXXI, 2065.pdf. [4] Xie Z. and Sharp T. G. (2000b) MAPS, 35 A172. [5] Xie Z. et al.(2001) LPS XXXII, 1805.pdf. [6] Sharp T.G. (2001) LPS XXXII, 2159.pdf. [7] Gasparik T. (1992) JGR, 97, 15181-15188.
Xie, Z.; Sharp, T. G.
Kinematic viscosity of rail steel melts modified by Fe-Si-Ca and Fe-Si-Ca-Ba alloys
1 Rails produced from steel modified by Fe?Si?Ca? Ba alloys is more plastic than steel modified by Fe?Si? Ca alloys, as shown in [1, 2]. Given that physicochemical properties from the initial melt are inherited in the final parts [3], this suggests that barium in the liquid steel is a stronger modifying agent than is calcium. Until recently, the efficiency
A. A. Deryabin; V. S. Tsepelev; V. V. Konashkov; E. Yu. Berestov; V. V. Mogil'nyi
Removal of phosphate from water using six Al-, Fe-, and Al-Fe-modified bentonite adsorbents.
This study was part of a larger effort that involves evaluating alternatives to upgrading secondary treatment systems in the United Arab Emirates for the removal of nutrients. In this study, six modified bentonite (BNT) phosphate adsorbents were prepared using solutions that contained hydroxy-polycations of aluminum (Al-BNT), iron (Fe-BNT), and mixtures of aluminum and iron (Al-Fe-BNT). The adsorption kinetics and capacities of the six adsorbents were evaluated, and the adsorbents were used to remove phosphorus from synthetic phosphate solutions and from treated wastewater. The experimental adsorption kinetics results were well represented by the pseudo-second-order kinetic model, with R(2) values ranging from 0.99 to 1.00. Similarly, the experimental equilibrium adsorption results were well represented by the Freundlich and Langmuir isotherms, with R(2) values ranging from 0.98 to 1.00. The adsorption capacities of the adsorbents were dependent on the BNT preparation conditions; the types, quantities and combination of metals used; BNT particle size; and adsorption pH. The Langmuir maximum adsorption capacities of the six adsorbents ranged from 8.9-14.5 mg P/g-BNT. The results suggested that the BNT preparations containing Fe alone or in combination with Al achieved higher adsorption capacities than the preparations containing only Al. However, the Al-BNT preparations exhibited higher adsorption rates than the Fe-BNT preparation. Three of the six adsorbents were used to remove phosphate from secondarily treated wastewater samples, and the removal results were comparable to those obtained using synthetic phosphate solutions. The BNT adsorbents also exhibited adequate settling characteristics and significant regeneration potential. PMID:23043345
Shanableh, Abdallah M; Elsergany, Moetaz M
Structural and transport properties of ferromagnetically coupled Fe/Si/Fe trilayers
We report structural, transport, and magnetic studies on ion beam deposited Fe(30,50 A)/Si(15,20,25,30,40 A)/Fe(30,50 A) trilayers. Grazing incidence x-ray reflectivity, grazing incidence x-ray diffraction, and x-ray photoelectron spectroscopy techniques are used to characterize the trilayers. From these studies we infer the formation of silicide interlayers at both Fe/Si and Si/Fe interfaces. Above 25 A nominal thickness of the Si layer, a uniform density layer of pure Si is formed. But below 25 A nominal thickness of Si layer, a nonuniform density layer of Si and silicide is found. The electrical resistance of trilayers depends on both Fe and Si layer thicknesses. Resistance decreases with the increase in temperature between 30 and 300 K. Attempts are made to analyze the temperature dependence of resistance with the help of semiconducting and electron hopping mechanisms. Magneto-optical Kerr effect results suggest that ferromagnetic correlations are established between the Fe layers of the trilayers.
Naik, S. R.; Rai, S.; Lodha, G. S. [Synchrotron Utilization and Material Research Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Chattopadhyay, M. K.; Sharma, V. K. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Majumdar, S. [Department of Physics, Indian Association for Cultivation of Science, Kolkata 700 032 (India)
Si diffusion in GaInAs-AlInAs high-electron-mobility transistor structures
NASA Astrophysics Data System (ADS)
Secondary-ion-mass spectrometry, Hall-effect measurements, and dc I-V characteristics of 1-micron Ga(0.47)In(0.53)As-Al(0.48)In(0.52)As high-electron mobility transistor structures indicate that significant diffusion of Si can occur in these layers. The source of the Si is both the intentional Si used for modulation doping of the devices, and Si which is an unintentional impurity in the Fe-doped InP substrates on which the layer is grown. Preannealing and polishing the substrates can lessen the effect.
Brown, A. S.; Itoh, T.; Wicks, G.; Eastman, L. F.
Investigation of intermetallics in hypoeutectic Al–Fe alloys by dissolution of the Al matrix
During the non-equilibrium solidification typical of DC (direct chill) castings a range of cooling rates occur from the surface to the casting center, and can cause the formation of metastable intermetallic phases (AlmFe, Al6Fe, etc.) in addition to the stable Al3Fe phase. The extensive presence of the plate-like Al3Fe phase in the as-cast structure adversely influences the mechanical properties of
Pedro R. Goulart; Valentim B. Lazarine; Claudenete V. Leal; José E. Spinelli; Noé Cheung; Amauri Garcia
Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices
NASA Technical Reports Server (NTRS)
Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.
Misra, Ajay K.
Thermodynamics of Al-substitution in Fe-oxyhydroxides
NASA Astrophysics Data System (ADS)
Ab initio simulation results are presented for dilute Al-substitution in the common Fe-(oxyhydr)oxide materials hematite, goethite, lepidocrocite and ferrihydrite. Experimental evidence from the literature suggests that Al-substitution in these materials may influence particle stability and phase transformation behavior, typically stabilizing the oxyhydroxide phases relative to the oxide, hematite. We find that all the alloyed phases studied are unstable with respect to phase separation into their unalloyed Fe/Al-(oxyhydr)oxide end members. Among the phases studied, ferrihydrite is predicted to allow Al-substitution with the lowest energy cost, while hematite appears to have the strongest tendency for phase separation. Considering the effect on thermodynamic stability relative to the stable Fe-oxide hematite, the three Fe-oxyhydroxide materials (goethite, lepidocrocite, ferrihydrite) are shown to be stabilized relative to doped Al-hematite as Al content is increased. Interactions between Al dopant atoms on neighboring Fe sites are simulated and are shown to have minimal influence on Fe–Al alloying thermodynamics in each of the materials simulated within the range of Al-dopant concentrations calculated. Simulations of Al-substitutions at the goethite (1 0 1) surface indicate that surface segregation of Al dopants is energetically favored for low Al concentrations, however this tendency diminishes when Al dopants form a full monolayer at the mineral surface.
Pinney, Nathan; Morgan, Dane
Mössbauer analysis of silicate Li2FeSiO4 and delithiated Li2-xFeSiO4 (x = 0.66) compounds
NASA Astrophysics Data System (ADS)
Lithium iron silicate compounds of Li2FeSiO4 and partially delithiated Li2-xFeSiO4 (x = 0.66) were synthesized by vacuum-sealed solid-state and chemical delithiation reactions, and their magnetic properties were characterized based on Mössbauer analysis. Crystal structures of both Li2FeSiO4 and Li2-xFeSiO4 (x = 0.66) compounds are found to be ?s-type (P21/n) monoclinic structures with difference in the lattice parameters due to lithium delithiation. Mössbauer spectrum of Li2FeSiO4 below TN1 = 20 K exhibits eight Lorentzians of Fe2+ with antiferromagnetic ordering. However, the spectrum of intermediate Li2-xFeSiO4 (x = 0.66) compound shows the appearance of magnetically ordered Fe3+ sextet below TN2 = 28 K. The temperature-dependent isomer shift of Li2-xFeSiO4 indicates the coexistence of nonequivalent Fe2+/Fe3+ valence states with the partial oxidation of FeO4, enhanced by the lithium ion deficiency. Also, we have observed a considerable change in electric quadrupole interaction between Fe2+/Fe3+ ions in Li2-xFeSiO4, when compared to that of Li2FeSiO4, due to the different lattice and valence electron contributions, being originated from crystalline and valence transitions caused by the lithiation/delithiation process.
Lee, In Kyu; Kim, Sam Jin; Kouh, Taejoon; Kim, Chul Sung
Copper solubility in FeO?Fe 2 O 3 ?SiO 2 ?Al 2 O 3 slag and distribution equilibria of Pb, Bi, Sb and As between slag and metallic copper
The solubility of copper in silica-unsaturated fayalite slags containing an average of about 8 pct Al2O3 was measured by equilibrating the slag with metallic copper at 1200 and 1300°C under CO?CO2 atmospheres with oxygen potentials in the rangep\\u000a O\\u000a 2=10?6 to 10?11 at. The copper solubility, which was found to be dependent upon the oxygen potential, was expressed in terms
M. Nagamori; P. J. Mackey; P. Tarassoff
Large tunnel magnetoresistance at room temperature with a Co{sub 2}FeAl full-Heusler alloy electrode
Magnetic tunnel junctions (MTJs) with a Co{sub 2}FeAl Heusler alloy electrode are fabricated by the deposition of the film using an ultrahigh vacuum sputtering system followed by photolithography and Ar ion etching. A tunnel magnetoresistance (TMR) of 47% at room temperature (RT) are obtained in a stack of Co{sub 2}FeAl/Al-O{sub x}/Co{sub 75}Fe{sub 25} magnetic tunnel junction (MTJ) fabricated on a thermally oxidized Si substrate despite the A2 type atomic site disorder for Co{sub 2}FeAl. There is no increase of TMR in MTJs with the B2 type Co{sub 2}FeAl, which is prepared by the deposition on a heated substrate. X-ray photoelectron spectroscopy (XPS) depth profiles in Co{sub 2}FeAl single layer films reveal that Al atoms in Co{sub 2}FeAl are oxidized preferentially at the surfaces. On the other hand, at the interfaces in Co{sub 2}FeAl/Al-O{sub x}/Co{sub 75}Fe{sub 25} MTJs, the ferromagnetic layers are hardly oxidized during plasma oxidation for a formation of Al oxide barriers.
Okamura, S.; Miyazaki, A.; Sugimoto, S.; Tezuka, N.; Inomata, K. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 (Japan); Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 (Japan); CREST, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan)
Spray cast Al-Si base alloys for stiffness and fatigue strength requirements
SUMMARY Hypereutectic AlSiFe spray-cast alloys exhibit properties similar to those of metal-matrix composite (MMC's) : high Young's modulus and a low coefficient of thermal expansion. These physical properties can be adjusted by changing the Si content of the alloy. The refinement of the microstructure is produced by formation of a large amount of nuclei in the spray. Consolidation done by
Al 2O 3–FeCrAl composites and functionally graded materials fabricated by reactive hot pressing
Al2O3–FeCrAl composites were fabricated by mixing Fe2O3, Al and Cr powders and then reactive hot pressing. The high temperature alloy FeCrAl was formed by the reaction of extra Al, Cr and the Fe reduced from Fe2O3. The Al2O3–FeCrAl composites with various Al2O3 fractions were successfully fabricated by the proper addition of extra Fe, Cr, Al or Al2O3 powders. A five-layer
J. Q. Li; W. A. Sun; W. Q. Ao; K. M. Gu; P. Xiao
Equation of state of (Mg,Fe)SiO3 perovskite and the chemical composition of lower mantle
NASA Astrophysics Data System (ADS)
Laboratory P--V--T measurements for mantle silicates at lower mantle conditions provide constraints on the bulk chemical composition of the lower mantle. Yet the existing interpretations of measurements of the thermal equation of state of (Mg,Fe)SiO3 perovskite, which is dominant in the lower mantle, are discrepant. While earlier studies (Knittle et al., 1986; Mao et al., 1991) preferred higher thermal expansivity of (Mg,Fe)SiO3 perovskite at ambient pressure, more recent measurements (Wang et al., 1994; Funamori et al., 1996) indicated lower thermal expansivity. However, only a few existing pressure-volume-temperature measurements for (Mg,Fe)SiO3 perovskite were conducted at lower mantle conditions (Funamori et al., 1996; Saxena et al., 1999; Fiquet et al, 1996, 2000). Among these, the measurement by Funamori et al. (1996) yields the strongest constraint on the Grüneisen parameter of (Mg,Fe)SiO3 perovskite at lower mantle conditions. Recent work (Shim et al., 2001) found a 2.5-GPa underestimate of pressure at 650--700 km depth conditions for Anderson et al. (1989)'s gold pressure-calibration scale, which has been widely used in multi-anvil studies: e.g., measurements by Funamori et al. (1996), compared with other pressure calibrants. Using the gold scale by Jamieson et al. (1982), we corrected the pressure of the multi-anvil data of MgSiO3 perovskite by Funamori et al. (1996). Inversions with the Birch-Murnaghan-Debye equation show that this pressure correction for the data yields a thermal expansivity between the high and low values. If resistance-heated diamond cell data (Saxena et al., 1999) or laser-heated diamond cell data (Fiquet et al., 1998,2000) are included, the corrected pressure scale reconciles the discrepancy in the thermal equation of state of (Mg,Fe)SiO3 perovskite; the high thermal expansivity is reproduced. The calculation using these inversions show that the density of (Mg,Fe)SiO3 perovskite are more consistent with seismic models (PREM and ak135) than pyrolite, at least at shallow lower mantle levels, and the density of pyrolite is 1 % smaller then seismic models throughout lower mantle. Thus the lower mantle may be chemically distinct from (possibly Fe or Si enriched relative to) the upper mantle.
Shim, S.; Jeanloz, R.
Crystal and quasicrystal structures in Al-Mn-Si alloys
It is shown that the alpha-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the 'projection' method of generating icosahedral structures from six-dimensional lattices, a simple description of the alpha-(AlMnSi) structure is found. This structure, and (it is conjectured) the icosahedral one, can also be described as a packing of
Veit Elser; C. L. Henley
Grain refinement mechanisms of hypoeutectic Al?Si alloys
The general concept of the grain refinement mechanism in hypoeutectic Al?Si alloys has been adopted from that in wrought alloys without consideration of the influence of the silicon content. In the present investigation the commercial grain refinement practice in Al?Si foundry alloys has been experimentally simulated by introducing synthetic TiB2 crystals directly into Al?Si melts. To explore the possible use
P. S. Mohanty; J. E. Gruzleski
Sound velocities of Fe and Fe-Si alloy in the Earth's core
Compressional wave velocity-density (VP - ?) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earth's core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planet's remotest region. Specifically, comparison between seismic VP - ? profiles of the core and candidate Fe alloys provides first-order information on the amount and type of potential light elements—including H, C, O, Si, and/or S—needed to compensate the density deficit of the core. To address this issue, here we have surveyed and analyzed the literature results in conjunction with newly measured VP - ? results of hexagonal closest-packed (hcp) Fe and hcp-Fe0.85Si0.15 alloy using in situ high-energy resolution inelastic X-ray scattering and X-ray diffraction. The nature of the Fe-Si alloy where Si is readily soluble in Fe represents an ideal solid-solution case to better understand the light-element alloying effects. Our results show that high temperature significantly decreases the VP of hcp-Fe at high pressures, and the Fe-Si alloy exhibits similar high-pressure VP - ? behavior to hcp-Fe via a constant density offset. These VP - ? data at a given temperature can be better described by an empirical power-law function with a concave behavior at higher densities than with a linear approximation. Our new datasets, together with literature results, allow us to build new VP - ? models of Fe alloys in order to determine the chemical composition of the core. Our models show that the VP - ? profile of Fe with 8 wt?% Si at 6,000 K matches well with the Preliminary Reference Earth Model of the inner core.
Mao, Zhu; Lin, Jung-Fu; Liu, Jin; Alatas, Ahmet; Gao, Lili; Zhao, Jiyong; Mao, Ho-Kwang
Structural and magnetic stability of Fe2NiSi
NASA Astrophysics Data System (ADS)
Full-potential ab-initio calculations in the stable F-43m phase have been performed to investigate the structural and magnetic properties of Fe2NiSi inverse Heusler alloys. The spin magnetic moment distributions show that present material is ferromagnetic in stable F-43m phase. Further, spin resolved electronic structure calculations show that the discrepancy in magnetic moments of Fe-I and Fe-II depend upon the hybridization of Fe with the main group element. It is found that the main group electron concentration is predominantly responsible in establishing the magnetic properties, formation of magnetic moments and the magnetic order for present alloy.
Gupta, Dinesh C.; Bhat, Idris Hamid; Chauhan, Mamta
Analysis of depth redistribution of implanted Fe near SiO2/Si interface
NASA Astrophysics Data System (ADS)
We have studied diffusion and clustering processes of room-temperature (RT)-implanted Fe ions in a SiO2/Si structure during annealing at 600 and 800 °C temperatures. The depth profile of implanted Fe was analyzed by Rutherford backscattering spectroscopy (RBS). In the previous study, we found that the hot-implanted Fe ions near the SiO2/Si interface at high substrate temperatures of 600 and 800 °C were distributed significantly different from the result predicted in the TRIM simulation. We think that the diffusion phenomena during the ion implantation at such elevated temperatures are recognized to be strongly enhanced by ion-beam-irradiation effect. In this study, to simplify the diffusion phenomenon, we particularly treat thermal diffusion process of RT-Fe implantation around the SiO2/Si interface in the post annealing at high temperatures. It is clearly seen that Fe atoms post-annealed at 800 °C are preferably gathered at a definitive depth in the SiO2 layer around 15 nm distances from the interface. We finally compare the Fe depth distribution for hot-implanted samples to that for the post-annealed ones by RBS analysis quantitatively.
Hoshino, Y.; Yokoyama, A.; Yachida, G.; Nakata, J.
Solidification and Microstructural Evolution of Hypereutectic Al-15Si-4Cu-Mg Alloys with High Magnesium Contents
NASA Astrophysics Data System (ADS)
The low coefficient of thermal expansion and good wear resistance of hypereutectic Al-Si-Mg alloys with high Mg contents, together with the increasing demand for lightweight materials in engine applications have generated an increasing interest in these materials in the automotive industry. In the interests of pursuing the development of new wear-resistant alloys, the current study was undertaken to investigate the effects of Mg additions ranging from 6 to 15 pct on the solidification behavior of hypereutectic Al-15Si-4Cu-Mg alloy using thermodynamic calculations, thermal analysis, and extensive microstructural examination. The Mg level strongly influenced the microstructural evolution of the primary Mg2Si phase as well as the solidification behavior. Thermodynamic predictions using ThermoCalc software reported the occurrence of six reactions, comprising the formation of primary Mg2Si; two pre-eutectic binary reactions, forming either Mg2Si + Si or Mg2Si + ?-Al phases; the main ternary eutectic reaction forming Mg2Si + Si + ?-Al; and two post-eutectic reactions resulting in the precipitation of the Q-Al5Mg8Cu2Si6 and ?-Al2Cu phases, respectively. Microstructures of the four alloys studied confirmed the presence of these phases, in addition to that of the ?-Al8Mg3FeSi6 (?-Fe) phase. The presence of the ?-Fe phase was also confirmed by thermal analysis. The morphology of the primary Mg2Si phase changed from an octahedral to a dendrite form at 12.52 pct Mg. Any further Mg addition only coarsened the dendrites. Image analysis measurements revealed a close correlation between the measured and calculated phase fractions of the primary Mg2Si and Si phases. ThermoCalc and Scheil calculations show good agreement with the experimental results obtained from microstructural and thermal analyses.
Tebib, M.; Ajersch, F.; Samuel, A. M.; Chen, X.-G.
In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy.
The solidification sequence of an AlMg4.7Si8 alloy is imaged in situ by synchrotron microtomography. Tomograms with (1.4 ?m)(3)/voxel have been recorded every minute while cooling the melt from 600 °C at a cooling rate of 5 K min(-1) to 540 °C in the solid state. The solidification process starts with the three-dimensional evolution of the ?-Al dendritic structure at 590 °C. The growth of the ?-Al dendrites is described by curvature parameters that represent the coarsening quantitatively, and ends in droplet-like shapes of the secondary dendrite arms at 577 °C. There, the eutectic valley of ?-Al/Mg2Si is reached, forming initially octahedral Mg2Si particles preferentially at the bases of the secondary dendrite arms. The eutectic grows with seaweed-like Mg2Si structures, with increasing connectivity. During this solidification stage Fe-aluminides form and expand as thin objects within the interdendritic liquid. Finally, the remaining liquid freezes as ternary ?-Al/Mg2Si/Si eutectic at 558 °C, increasing further the connectivity of the intermetallic phases. The frozen alloy consists of four phases exhibiting morphologies characteristic of their mode of solidification: ?-Al dendrites, eutectic ?-Al/Mg2Si "Chinese script" with Fe-aluminides, and interpenetrating ?-Al/Mg2Si/Si ternary eutectic. PMID:23470958
Tolnai, D; Townsend, P; Requena, G; Salvo, L; Lendvai, J; Degischer, H P
In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy
The solidification sequence of an AlMg4.7Si8 alloy is imaged in situ by synchrotron microtomography. Tomograms with (1.4 ?m)3/voxel have been recorded every minute while cooling the melt from 600 °C at a cooling rate of 5 K min?1 to 540 °C in the solid state. The solidification process starts with the three-dimensional evolution of the ?-Al dendritic structure at 590 °C. The growth of the ?-Al dendrites is described by curvature parameters that represent the coarsening quantitatively, and ends in droplet-like shapes of the secondary dendrite arms at 577 °C. There, the eutectic valley of ?-Al/Mg2Si is reached, forming initially octahedral Mg2Si particles preferentially at the bases of the secondary dendrite arms. The eutectic grows with seaweed-like Mg2Si structures, with increasing connectivity. During this solidification stage Fe-aluminides form and expand as thin objects within the interdendritic liquid. Finally, the remaining liquid freezes as ternary ?-Al/Mg2Si/Si eutectic at 558 °C, increasing further the connectivity of the intermetallic phases. The frozen alloy consists of four phases exhibiting morphologies characteristic of their mode of solidification: ?-Al dendrites, eutectic ?-Al/Mg2Si "Chinese script" with Fe-aluminides, and interpenetrating ?-Al/Mg2Si/Si ternary eutectic.
Tolnai, D.; Townsend, P.; Requena, G.; Salvo, L.; Lendvai, J.; Degischer, H.P.
Preparation and Mechanical Properties of Fe 3 Al Nanostructured Intermetallics
Nanostructured Fe3Al intermetallic compounds were produced by using hydrogen arc plasma method. The transmission electron microscopy experiments showed that the average particle size of the as-synthesized was about 40-nm. The change in hardness of Fe3Al nanostructured intermetallic compounds with annealing temperatures was observed and evaluated.
Hao Chuncheng; Cui Zuolin; Yin Yansheng; Zhang Zhikun
The role of iron in the formation of porosity in Al-Si-Cu-based casting alloys. Part 2: A phase-diagram approach
The mechanism by which iron causes casting defects in the AA309 (Al-5 pct Si-1.2 pct Cu-0.5 pct Mg) may be related to the solidification sequence of the alloy. Superimposing calculated segregation lines on the liquidus projection of the ternary Al-Si-Fe phase diagram suggests that porosity is minimized at a critical iron content when solidification proceeds directly from the primary field to the ternary Al-Si-{beta}Al{sub 5}FeSi eutectic point. Solidification via the binary Al-{beta}Al{sub 5}FeSi eutectic is detrimental to casting integrity. This hypothesis was tested by comparing the critical iron content observed in the standard AA309 alloy to that of a high-silicon (10 pct Si) variant of this alloy.
Taylor, J.A.; Schaffer, G.B.; StJohn, D.H. [Univ. of Queensland, Brisbane (Australia)
Oxidation of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) intermetallic compounds at low-oxygen pressures
The oxidation behavior of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) (Ni{sub 75}Al{sub 20}Si{sub 5}) intermetallic compounds was studied at 1073 K and oxygen partial pressures of 5 {approximately} 9 x 10{sup {minus}6} atm, 1.2 x 10{sup {minus}14} atm, and 1.2 x 10{sup {minus}19} atm by means of a manometric apparatus, and Rhines packs of NiO/Ni and FeO/Fe, respectively. Oxidation kinetics were determined either by recording weight gains or by measuring the internal-oxidation-zone depths. The structures and morphologies of oxides were also studied. Relatively low oxidation rates occurred for both compounds when oxidized in the manometric apparatus, while fast internal oxidation was observed for both compounds in the NiO/Ni pack. The fastest oxidation occurred in the {gamma}{prime}-Ni{sub 3}Al compound in the FeO/Fe pack. A healing Al{sub 2}O{sub 3} layer was formed on the surface of {gamma}{prime}-Ni{sub 3}Al(Si) compound in the FeO/Fe pack, indicating a synergistic effect between the solute elements in the compound at the oxygen pressures corresponding to the dissociation of FeO. The oxidation rate was found to depend on the volume expansion associated with solute-atom oxidation.
Yi, H.C. [Guigne International, Newfoundland (Canada); Smeltzer, W.W.; Petric, A. [McMaster Univ., Hamilton, Ontario (Canada)
High Temperature Sulfidation Properties of FeAl Alloys
The sulfidation properties of the Fe-Al alloys containing 6, 9, 18 and 28 atomic percent Al were investigated in alloy\\/FeS diffusion couples, in sulfur vapour at the dissociation pressure of the FeS and in H?S+H atmosphereat 1173K. The reaction kinetics were determined thermogravitmetrically and by layer thickness. measurements. The reaction specimens were analyzed using light microscopy, X-ray diffraction and electron
Prakash Chandra Patnaik
Sr-Al-Si co-segregated regions in eutectic Si phase of Sr-modified Al-10Si alloy.
The addition of 200 ppm strontium to an Al-10 wt% Si casting alloy changes the morphology of the eutectic silicon phase from coarse plate-like to fine fibrous networks. In order to clarify this modification mechanism the location of Sr within the eutectic Si phase has been investigated by a combination of high-resolution methods. Whereas three-dimensional atom probe tomography allows us to visualise the distribution of Sr on the atomic scale and to analyse its local enrichment, transmission electron microscopy yields information about the crystallographic nature of segregated regions. Segregations with two kinds of morphologies were found at the intersections of Si twin lamellae: Sr-Al-Si co-segregations of rod-like morphology and Al-rich regions of spherical morphology. Both are responsible for the formation of a high density of multiple twins and promote the anisotropic growth of the eutectic Si phase in specific crystallographic directions during solidification. The experimental findings are related to the previously postulated mechanism of "impurity induced twinning". PMID:23298536
Timpel, M; Wanderka, N; Schlesiger, R; Yamamoto, T; Isheim, D; Schmitz, G; Matsumura, S; Banhart, J
Structural evolution in mechanically alloyed Al-Fe powders
The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al{sub 3}Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al{sub 5}Fe{sub 2} was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.
Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H. [Univ. of Idaho, Moscow, ID (United States)
Systematic study of surface magnetism in Si(111)-Fe system grown by solid phase epitaxy: In situ schematic magnetic phase diagram of Si(111)-Fe
NASA Astrophysics Data System (ADS)
We have studied in situ structures and magnetic properties for several iron silicides grown on Si(111)7×7 clean surfaces by the solid phase epitaxy (SPE) method: deposition of Fe at 40 K and subsequently annealing, and summarized almost all silicide phases depending on the deposition thickness and the annealing temperature as a "schematic magnetic phase diagram". In the SPE growth, bcc-Fe(111)1×1, c-FeSi(111)1×1, 2×2, and c(4×8), ?-FeSi2(112)2×2, ?-FeSi(111)?3 ×? 3-R30°, ?-FeSi2(101)/(110) and polycrystalline phases are formed on Si(111)7×7 surfaces depending on Fe coverage (0.15-10.0 nm) and annealing temperature (470-1070 K). The structures and magnetic properties of all the above Fe silicide phases have been characterized by using in situ reflection high-energy electron diffraction, scanning tunneling microscopy, and surface magneto-optical Kerr effect. Bulk-unstable c-FeSi phases showed ferromagnetic property at 40 K and this ferromagnetism remained even after air exposure. For the c-FeSi(111)/Si(111) system, the large spin polarization was proposed at the Fe interface atoms in the B5-type interface structure between the c-FeSi(111) ultra-thin film and the Si(111) substrate by first-principle calculations.
Hattori, Azusa N.; Hattori, Ken; Kataoka, Keita; Takematsu, Emi; Ishii, Akira; Komori, Fumio; Daimon, Hiroshi
Al, Si ordering in chabazites: A Monte Carlo study
NASA Astrophysics Data System (ADS)
The Al, Si distribution in the framework of chabazites has been studied as a function of the Al loading by Monte Carlo simulations. The atom ordering has been characterized by several thermodynamic variables and order parameters obtained from the simulations at room temperature. One finds three different Al,Si ordering patterns, whose stability limits are defined from characteristic changes in the thermodynamic variables. Long-range order is found in the atom distribution for Al loading higher than 0.44. We have found similarities with the Al,Si distribution in other zeolitic frameworks which include six-membered rings.
Gordillo, M. C.; Herrero, C. P.
Microstructure and mechanical properties of spray deposited hypoeutectic Al–Si alloy
The microstructure and the tensile properties of an Al–8.9wt.% Si–3.2wt.% Cu–0.9wt.% Fe–0.8% Zn alloy processed by spray forming was investigated. The alloy was gas atomized with argon and deposited onto a copper substrate. The microstructure was evaluated by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Small faceted dispersoids observed surrounding equiaxial ?-Al matrix were
C. F. Ferrarini; C. Bolfarini; C. S. Kiminami; W. J. Botta F
Quantitative Analysis in the Al-Mg-Si System with Small Amounts of Mg and Si.
National Technical Information Service (NTIS)
In the commercial Al-Mg-Si system, detailed knowledge of the precipitation rate of the Mg2Si needles and the dissolution rate of the original Mg2Si particles are of practical importance. However, due to low Mg and Si contents, experimental studies of the ...
Y. Tang H. K. Nylund R. Hoeier N. Ryum
Compositional range, thermal stability, hardness and electrical resistivity of amorphous alloys in Al-Si (or Ge)-transition metal systems
An amorphous single phase was found to be formed in wide compositional ranges in rapidly solidified Al-Si-transition metal (M) and Al-Ge-M alloys. The compositional ranges are in the range from 12 to 53 at. % Si or Ge and 8 to 23% M and Al-Si-Co and Al-Ge-Fe alloys have the widest glass-formation ranges. Because the interaction between aluminium and silicon
A. Inoue; Y. Bizen; H. M. Kimura; T. Masumoto; M. Sakamoto
Temperature compensating Elinvar character in Fe-Mn-Si alloys
NASA Astrophysics Data System (ADS)
Young's modulus-temperature and thermal expansion curves were measured in ?-Fe-31Mn-(0.25-8.67) Si-0.77C (at%) alloys by dynamic audio resonance method and in a light dilatometer. The results show that the anomalies in Young's modulus and thermal expansion appear near the Néel temperature. The temperature coefficient of Young's modulus, (1/ Ep)( dEp/ dT), is controlled by Si content below the Néel temperature. When Si content increases to 5.31 at%, ( 1/ Ep)( dEp/ dT) is close to zero in temperature range from 260 to 335 K, i.e. the Fe-31Mn-5.31Si-0.67C (at%) alloy shows Elinvar character. The temperature range in which the Elinvar character appears is wider than that of ?-Fe-Mn Elinvar alloys. The change in exchange energy and the ? E effect result from the effect of Si on the antiferromagnetic behavior in ?-Fe-Mn alloys since it induces or enhances localized magnetic moment. When the increase in normal Young's modulus due to lowering temperature is compensated by the ? E effect caused by the antiferromagnetic ordering, Elinvar character appears.
Zhang, Yansheng; Tian, Xing; Qin, Zuoxiang; Jiang, Haichang
Thermochemistry of (Fe 2+, Mg)SiO 3 orthopyroxene
NASA Astrophysics Data System (ADS)
Enthalpies of solution in eutectic (Li, Na) 2B 2O 4 melts at 1023 K were measured for five synthetic orthopyroxenes on the join MgSiO 3-FeSiO 3. The pyroxenes were synthesized at 1120°C and 20 kbar and thus were presumed to be highly disordered. The measurements indicate a small positive enthalpy of mixing, with WH = 950 cal/ MSiO3. Enthalpy of solution measurements were made on a natural, well-ordered orthopyroxene near the composition En 52.5Fs 47.5 and on this material after heat-treatment at 1150°C and 20 kbar. Irreversible expansion of the unit-cell constants of the natural pyroxene after heat-treatment at various temperatures was used to characterize the degree of M-site disorder. The observed enthalpy of solution decrement of 0.85 kcal/MSiO 3 between the natural En 52.5 and the same material heated at 1150° corresponds to about half of the maximum possible disordering, or ?XFeM1 ? 0.25, which leads to a ?H of 7.5 kcal/M 2Si 2O 6, for the exchange reaction: Fe( M2) + Mg( Ml) = Fe( Ml) + Mg( M2) if M-site interaction energy terms are ignored. This ? H is larger than inferred from any of the analyses of site-occupancy data except that of Besancon (1981), who gave a very similar value. The measured ? H of disorder and the WH of mixing together indicate a large ? H as great as 3.2 kcal for the reciprocal reaction: Fe2Si2O6 + Mg2Si2O6 = Fe( M2) Mg( M1) Si2O6 + Fe( M1) Mg( M2) Si2O6 as anticipated by Sack (1980). As a consequence of the inferred magnitudes of ?Hof the exchange and reciprocal reactions, departures from ideality of Gibbs energy of mixing of orthopyroxene are very small at 700°-1000°C. Activities of MgSiO 3 and FeSiO 3 may be replaced by their mol fractions at all temperatures in most petrologic calculations.
Chatillon-Colinet, C.; Newton, R. C.; Perkins, D., III; Kleppa, O. J.
Testing of SiC Particle Reinforced Al Alloy.
National Technical Information Service (NTIS)
Researchers mixed SiC particles and Al6061 atomized powder to produce round bar and plate-shaped Al alloys reinforced with Si particles by means of hot extrusion. Sectional shapes such as round, tube, H, Z, T, etc., could be optionally selected by changin...
T. Furuta S. Ushigome T. Soeda
Eutectic nucleation in hypoeutectic Al-Si alloys
The nucleation mechanism of eutectic grains in hypoeutectic Al-Si foundry alloys has been investigated by examining deep etched specimens in high-resolution field emission gun scanning electron microscope (FEG-SEM) and by using in-situ Focused Ion Beam (FIB) milling and microscopy. Both unmodified and Sr-modified alloys were studied to characterize the nucleation mechanism of eutectic silicon flakes and fibers. It is proposed that following nucleation of eutectic Al on the primary {alpha}-Al dendrites, fine Si particles form at the solidification front upon which the eutectic Si flakes and fibers could develop. The formation of small Si particles is attributed to Si enrichment of the remaining melt due to the formation of eutectic Al (aluminum spikes) at the eutectic temperature. A hypothesis is then proposed to explain the mechanism of eutectic grains formation with main emphasis on the eutectic Si phase.
Nafisi, S. [Facility for Electron Microscopy Research, McGill University, 3640 University St., Montreal, QC, H3A 2B2 (Canada)], E-mail: email@example.com; Ghomashchi, R. [Advanced Materials and Processing Research Institute, Suite 122, A7-1390 Major MacKenzie, ON, L4S 0A1 (Canada); Vali, H. [Facility for Electron Microscopy Research, McGill University, 3640 University St., Montreal, QC, H3A 2B2 (Canada)
Strength anomaly in B2 FeAl single crystals
Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.
Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School
The study of primary Si phase in spray forming hypereutectic Al–Si alloy
This paper is concerned mainly with the influence of the G\\/M ratio in the spray forming process on the size of the primary Si phase in hypereutectic Al–Si alloy. Before the hot extrusion process the growth of primary Si phase in as-deposited Al–Si alloy was observed with the increasing of the preheating temperature. The microstructure of the different samples which
Xiong Baiqing; Zhang Yongan; Wei Qiang; Shi Likai; Xie Changan; Shang Chengjia; He Xinlai
Effects of Si content on defect band formation in hypoeutectic Al–Si die castings
Al–3–11% Si alloys have been high-pressure die-cast and characterized microstructurally. Alstruc was used to calculate the solidification characteristics and fraction of eutectic. Defect bands were observed at all Si contents, although their constitution, position and distinctiveness were a function of Si content. The defect bands contain a higher fraction Al–Si eutectic than the surroundings in all alloys, and porosity was
Hans I. Laukli; Christopher M. Gourlay; Arne K. Dahle; Otto Lohne
Fe2.7Si, Fe50Ni and Fe50Co Soft Ferromagnetic Materials by Powder Injection Moulding
Powder injection moulding is an enabling technology for the production of soft ferromagnetic components, which bring solutions and open the way for new applications. In this work, square toroid parts have been injection moulded for three typical soft magnetic alloy compositions. Fe2.7Si, Fe50Ni and Fe50Co feedstocks were produced by mixing elemental powders and a multicomponent binder. The green parts were
Al-Cu-Fe-Pd-Mn and Al-Cr-Pd-Mn quasicrystalline alloys
While searching for new multicomponent quasicrystalline alloys, the authors have suggested a principle of composition activity in the quasicrystal constitution. This means that some new quasicrystals can be constituted by adding several quasicrystalline alloy compositions, and these alloys can be obtained by means of rapid solidification or ingot processing. Guided by this principle, Al-Mn-Cr, Al-Cu-Fe-Mn, Al-Cu-Fe-Cr, Al-Cu-Fe-Cr-Mn, Al-Mn-Ni-Ti, Al-Mn-Fe-Ti, Al-Cu-Fe-Ni-Ti and other multicomponent quasicrystalline alloys have been found. A recent study used Al[sub 70]Pd[sub 20]Mn[sub 10], Al[sub 65]Cu[sub 20]Fe[sub 15] and Al[sub 85]Cr[sub 15] quasicrystalline alloys to formulate new alloys. Both Al-Cu-Fe-Pd-Mn and Al-Cr-Pd-Mn alloys are quasicrystalline. In this paper, they discuss these two quasicrystals, their formation, electronic diffraction and composition scope and thermal stability in detail.
Chen Zhenhua (Univ. of Technology, Hunan (China). Powder Metallurgy Research Inst.); Inoue, Akihisa; Masumoto, Tsuyoshi (Tohoku Univ. (Japan). Metal Research Inst.)
Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys
The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4 h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of ?-Al matrix and a rigid long-range 3-D network of Al7Cu4Ni, Al4Cu2Mg8Si7, Al2Cu, Al15Si2(FeMn)3 and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300 °C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20 vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ?15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4 h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si.
Asghar, Z.; Requena, G.; Boller, E.
Cast AlSi9Cu4 alloy with hybride strenghtened by FexAly-Al2O3 composite powder
NASA Astrophysics Data System (ADS)
The main objective of the study was to develop a technology of dispersion strenghtened hypoeutectic Al-Si alloy. The article presented the materials and technology conception for producing aluminium matrix composite AlSi9Cu4Fe alloy with hybride reinforcement of AlxFey intermetallic and aluminium oxide powders. Composite powder obtained in mechanical agllomerisation mixture of elemental powders. Changes in the structure were confirmed by TA and ATD thermal analyses plotting the solidification curves, which showed a decrease in temperature Tliq compared to the unmodified alloy and an exothermic effect originating from the crystallisation of eutectics with alloying elements. The examinations carried out by SEM and BSE as well as the determination of local chemical composition by EDX technique have characterised the structure of the alloy as containing some binary Al-Si-Al-Cu and Al-Fe eutectics and multicomponent eutectics.
Pi?tkowski, J.; Formanek, B.
Oxidation behavior of FeAl+Hf,Zr,B
NASA Technical Reports Server (NTRS)
The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.
Smialek, James L.; Doychak, Joseph
Solid phase crystallization of amorphous Fe-Si layers synthesized by ion implantation
NASA Astrophysics Data System (ADS)
Microstructural changes of ion-beam-synthesized amorphous Fe-Si layers on thermal annealing were investigated using transmission electron microscopy. Single crystal Si(111) substrates were irradiated with 120 keV Fe+ ions at cryogenic temperature to a fluence of 4.0×1017 cm-2, followed by thermal annealing at 200-700 °C. The amorphous Fe-Si layer in the as-implanted sample crystallized to polycrystalline ?-FeSi and ?-FeSi2 layers after annealing at 500 °C for 2 h.V-FeSi transformed into ?-FeSi2 and the ?-FeSi2 region extended with increasing annealing temperature. Excess Fe atoms from V-to-? phase transformation migrate toward the Si substrate via ?-FeSi2 grain boundaries. We discuss the recrystallization process of amorphous Fe-Si thin layers and the growth mechanism of ?-FeSi2 thin layers formed in high-dose Fe ion-implanted Si.
Naito, Muneyuki; Ishimaru, Manabu; Hirotsu, Yoshihiko; Valdez, James A.; Sickafus, Kurt E.
Mechanisms of linear anelasticity in Fe- M and Fe-Al- M ( M = Ga, Ge) alloys
NASA Astrophysics Data System (ADS)
Linear anelastic effects in binary and ternary alloys of iron with 13 and 17 at % Ga, 12 at % Ge, and 4-8 at % Al (Fe-13Ga, Fe-17Ga, Fe-12Ge, Fe-8Al-3Ga, Fe-8Al-4Ge, and Fe-4Al-8Ge) have been investigated. In all of these alloys, thermally activated effects of linear anelasticity have been found and identified that are caused by point defects in interstitial (Snoek-type relaxation) and substitutional (Zener relaxation) solid solutions, as well as by dislocations (Hasiguti effect), and by grain boundaries. The effects of the alloy composition on the activation parameters of the above-mentioned relaxation mechanisms have been determined. In addition, frequency-independent effects related to processes of structural rearrangement, such as ordering and disordering of the alloys have been revealed due to the specific features in the curves of the temperature dependences of internal friction for almost all compositions.
Golovin, I. S.
Studies of the Si(111) surface with various Al overlayers
The electronic structure of the Si(111) surface with Al overlayers has been investigated by the self-consistent pseudopotential method for three different Al chemisorption sites. The geometries are a onefold coordinated covalent site, and two other geometries which correspond to threefold coordinated ionic sites with different Al-Si bond lengths. The electronic energy bands, local densities of states, and charge distributions for
H. I. Zhang; M. Schlüter
Room Temperature Mechanical Properties of Fe3Al Intermetallic Alloys with Li and Ni Additions
NASA Astrophysics Data System (ADS)
This work analyzes the effect of very small additions of Li and Ni on the mechanical properties of the Fe72Al28 intermetallic alloy, close to the Fe3Al ratio. Hardness and tensile strength at room temperature were analyzed for the cast Fe3Al intermetallic alloys as a function of Li and Ni additions. For this purpose, high-purity raw materials were melted in an open induction furnace into a SiC crucible and the liquid alloys were poured into sand moulds to directly get tensile test-shaped specimens to minimize machining. Mechanical tests were carried out in the as-cast condition as well as after a homogenization heat treatment at 400 °C for 120 h. The obtained microstructure was characterized by XRD and SEM. Results show an increase in ductility, particularly when Li was added.
Rosas, G.; Esparza, R.; Bedolla-Jacuinde, A.; Pérez, R.
Structural properties of the solidified-Al\\/regrown-Si structures of printed Al contacts on crystalline Si solar cells
Structural properties of the solidified-Al\\/regrown-Si structures of screen-printed aluminum contacts on a crystalline silicon solar cell have been studied by transmission electron microscopy (TEM). TEM results revealed that the solidified-Al\\/regrown-Si boundary is sharply defined except for the local silicon protrusion. A possible mechanism for forming the Si protrusion has been discussed. The results presented in this study suggested that the
Ching-Hsi Lin; Song-Yeu Tsai; Shih-Peng Hsu; Ming-Hsun Hsieh
Electrolyte effects in Li(Si)\\/FeS2 thermal batteries
The most common electrochemical couple for thermally activated ('thermal') batteries is the Li-alloy\\/FeS2 system. The most common Li-alloys used for anodes are 20% Li-80% Al and 44% Li-56% Si (by weight); liquid Li immobilized with iron powder has also been used. The standard electrolyte that has been used in thermal batteries over the years is the LiCl-KCl eutectic that melts
Ronald A. Guidotti; Frederick W. Reinhardt
Microstructure Evolution of Atomized Al-0.61 wt pct Fe and Al-1.90 wt pct Fe Alloys
NASA Astrophysics Data System (ADS)
The microstructure evolution of impulse atomized powders of Al-0.61 wt pct and Al-1.90 wt pct Fe compositions have been investigated with a scanning electron microscope, transmission electron microscope, neutron diffraction, and backscattering electron diffraction (EBSD). Both hypoeutectic and hypereutectic compositions demonstrated similar macrostructure ( i.e., primary ?-Al dendrites/cells with eutectic Al-Fe intermetallics decorated at the dendritic/cellular walls). Selected area electron diffraction (SAED) analysis and SAED pattern simulation identified the eutectic Al-Fe intermetallic as AlmFe ( m = 4.0-4.4). This is verified by neutron diffraction analysis. Cubic texture was observed by EBSD on the droplets with dendritic growth direction close to <111>. The possible reasons are discussed.
Chen, Jian; Dahlborg, Ulf; Bao, Cui Min; Calvo-Dahlborg, Monique; Henein, Hani
Dielectric properties of spark plasma sintered AlN/SiC composite ceramics
NASA Astrophysics Data System (ADS)
In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were prepared by spark plasma sintering (SPS) under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%-40wt% SiC at 1600°C for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and ?-SiC, the samples also contained 2H-SiC and Fe5Si3, as detected by X-ray difraction (XRD). The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ceramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.
Gao, Peng; Jia, Cheng-chang; Cao, Wen-bin; Wang, Cong-cong; Liang, Dong; Xu, Guo-liang
Fabrication of novel double-hetero-epitaxial SOI structure Si/?-Al 2O 3/Si
NASA Astrophysics Data System (ADS)
In this paper, we report the fabrication of Si-based double-hetero-epitaxial silicon on insulator (SOI) structure Si/?-Al 2O 3/Si. Firstly, single crystalline ?-Al 2O 3(1 0 0) insulator films were grown epitaxially on Si(1 0 0) using the sources of TMA (Al(CH 3) 3) and O 2 by very low-pressure chemical vapor deposition. Afterwards, Si(1 0 0) epitaxial films were grown on ?-Al 2O 3 (1 0 0)/Si(1 0 0) epi-substrates using a chemical vapor deposition method similar to the silicon on sapphire epitaxial growth. The Si/?-Al 2O 3/Si SOI materials are characterized in detail by reflect high-energy electron diffraction, X-ray diffraction and Auger energy spectrum (AES) techniques. The insulator layer of ?-Al 2O 3 has an excellent dielectric property. The leakage current is less than 1×10 -10 A/cm 2 when the electric field is below 1.3 MV/cm. The Si film grown on ?-Al 2O 3/Si epi-substrates was single crystalline. Meanwhile, the AES depth profile of the SOI structure shows that the composition of ?-Al 2O 3 film is uniform, and the carbon contamination is not observed. Additionally, the ?-Al 2O 3/Si epi-substrates are suitable candidates as a platform for a variety of active layers such as GaN, SiC and GeSi. It shows a bright future for microelectronic and optical electronics applications.
Tan, Liwen; Wang, Qiyuan; Wang, Jun; Yu, Yuanhuan; Liu, Zhongli; Lin, Lanying
Spin transition and substitution of Fe3+ in Al-bearing post-Mg-perovskite
NASA Astrophysics Data System (ADS)
The spin transition and substitution of Fe3+ in Mg0.85Fe3+0.15Al0.15Si0.85O3 post-Mg-perovskite (PPv) synthesized at 165-170 GPa, 2100 K were examined by X-ray emission spectroscopy (XES) and X-ray diffraction (XRD) during decompression to 37 GPa without annealing. XRD showed that samples were single phase PPv down to 49 GPa, although the samples may have partly become amorphous. The result of XES measurement indicates that Fe3+ is fully low spin (LS) for 165-100 GPa and Fe3+ largely changes from LS to high spin (HS) between 80 and ˜40 GPa. These results combined with previous reports indicate that Al and LS Fe3+ may occupy the A-(dodecahedral) and B-(octahedral) sites, respectively, as the favorable cation sites for 165-100 GPa in Al-bearing PPv. Based on the present results on Fe3+ and recent theoretical reports on Fe2+, the spin states of iron in lower mantle PPv are discussed.
Fujino, Kiyoshi; Nishio-Hamane, Daisuke; Kuwayama, Yasuhiro; Sata, Nagayoshi; Murakami, Sayaka; Whitaker, Matthew; Shinozaki, Ayako; Ohfuji, Hiroaki; Kojima, Yohei; Irifune, Tetsuo; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding
Influence of Some Trace Elements on Solidification Path and Microstructure of Al-Si Foundry Alloys
NASA Astrophysics Data System (ADS)
In the present study, Ca, Ni, V, and Zn were added to a high purity binary Al-7wt pct Si and commercial purity A356 foundry alloy in the nominal range of 50 to 600 ppm in order to study their effect on the solidification path and the resultant microstructure. Thermal analysis was used to assess nucleation and growth of the various phases. It was found that Ca and Ni additions suppress characteristic temperatures associated with nucleation and growth of the eutectic by up to 4 and 1.5 K, respectively. Additionally, Ca was observed to modify the eutectic Si and a concentration as low as 39 ppm Ca was sufficient to precipitate the geometrically unfavored polyhedral Al2Si2Ca phase. Furthermore, Ni addition resulted in the formation of two intermetallic phases when the Ni concentration exceeded 300 ppm. These phases have been quantified as Al3Ni and Al9FeNi by SEM-EDS. V and Zn had no apparent effect on the cooling curve and the microstructure. Even though it could be shown that V accumulates preferably in ?-Al5FeSi particles, V concentrations of 600 ppm were too low to have any influence on the phase's morphology.
Ludwig, Thomas Hartmut; Schaffer, Paul Louis; Arnberg, Lars
Thermal stability of TiAlN and nanocomposite TiAlSiN thin films.
TiAlN and TiAlSiN coatings were synthesized by a cathodic arc deposition process. Titanium, Ti50Al50 alloy and AlSi (88 at.% of Al and 12 at.% of Si) alloy targets were adopted as the cathode materials. X-ray diffraction analyses revealed that Ti0.5Al0.5N and Ti49Al0.44Si0.07N possess a B1-NaCl crystal structure. The lattice constants of the Ti0.5Al0.5N and Ti0.49Al0.44Si0.07N calculated from XRD pattern were 0.418 nm and 0.422 nm, respectively. For the high temperature oxidation test, the coated samples were annealed at 900 degrees C in air atmosphere for 2 hours. In this study, the deposited Ti0.5Al0.5N had completely transformed to TiO2 and Al2O3, and Ti0.49Al0.44Si0.07N remained the as-deposited structure after oxidation treatment. It indicated that Ti0.49Al0.44Si0.07N possesses superior oxidation resistance than Ti0.5Al0.5N, due to the amorphous SiNx phase existed in the nanocomposite structure. The different oxidation mechanisms of Ti50Al50N and Ti0.49Al0.44Si0.07N at high temperature of 900 degrees C are developed in this study. PMID:19441466
Yang, Sheng-Min; Chang, Yin-Yu; Lin, Dong-Yih; Wang, Da-Yung; Wu, Weite
Effect of Introducing ?-FeSi2 Template Layers on Defect Density and Minority Carrier Diffusion Length in Si Region near p-?-FeSi2/n-Si Heterointerface
NASA Astrophysics Data System (ADS)
The electrical properties of defects in a p-?-FeSi2/n-Si heterostructures were investigated by deep level transient spectroscopy (DLTS) and the electron-beam-induced current (EBIC) technique. DLTS revealed the presence of trap levels for holes, caused by defects in the n-Si layer near the interface during the ?-FeSi2 film fabrication. The defect density became small when a 20-nm-thick ?-FeSi2 template layer was grown on the n-Si prior to molecular beam epitaxy (MBE) of a 700-nm-thick ?-FeSi2 layer. The diffusion length of minority carriers in the n-Si was found to be approximately 15 ?m by EBIC. This is much larger than the value of approximately 3 ?m for the n-Si obtained when the template layer was not inserted.
Kawakami, Hideki; Suzuno, Mitsushi; Akutsu, Keiichi; Chen, Jun; Jiptner, Karolin; Sekiguchi, Takashi; Suemasu, Takashi
Observations of Al, Fe and Ca(+) in Mercury's Exosphere
NASA Technical Reports Server (NTRS)
We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.
Bida, Thomas A.; Killen, Rosemary M.
Potentiodynamic Polarization Aspects of the As-cast and Sprayed Al-Si, Al-Sn and Al-Sn-Si Alloys in a Sodium Chloride Solution
NASA Astrophysics Data System (ADS)
The present study compares the corrosion behavior of Al-Sn, Al-Si and Al-Sn-Si alloys processed by spray forming with that of the conventional chill cast ones in aqueous 0.1 N NaCl solution. Spray forming resulted in finer microstructural features with uniform distribution of second-phase particles. The spray formed Al-Si samples showed improved corrosion resistance as compared to the chill cast ones. The Sn containing alloys showed inferior corrosion resistance in the neutral electrolyte. The addition of 12.5 wt.% Si to Al-Sn alloys improves the corrosion resistance.
Anil, M.; Balaji, S.; Upadhyaya, A.; Ghosh, M. K.; Ojha, S. N.
State-of-the-art SiAlON materials
NASA Technical Reports Server (NTRS)
The state of the art of SiAlONs is examined. The review includes work on phase relations, crystal structure, synthesis, fabrication, and properties of various SiAlONs. The essential features of compositions, fabrication methods, and microstructure are reviewed. High temperature flexure strength, creep, fracture toughness, oxidation, and thermal shock resistance are discussed. These data are compared to those for some currently produced silicon nitride ceramics to assess the potential of SiAlON materials for use in advanced gas turbine engines.
Dutta, S.
Structure Sensitive Properties of Liquid Al-Si Alloys
NASA Astrophysics Data System (ADS)
Development and application of new expedient aluminum-based light alloys are a key issue in current material science. In this study measurements are presented for the thermophysical properties of liquid Al-7Si, AlSi7Mg, and AlSi8Cu3 (mass%) alloys, which are the most utilized casting alloys in the aluminum industry. Experimental data with respect to the density, viscosity, and the electrical and thermal conductivities have been determined in a wide temperature range, and corresponding fit relations have been derived. Comparisons with already published data and scaling relations available in the literature are given.
Sklyarchuk, V.; Plevachuk, Yu.; Yakymovych, A.; Eckert, S.; Gerbeth, G.; Eigenfeld, K.
Surface Microstructure of Fe3Al After Severe Plastic Deformation
NASA Astrophysics Data System (ADS)
Nanocrystals were produced on the surface of Fe3Al intermetallic compound by a severe plastic deformation technology—surface mechanical attrition. The phase and grain evolutions were characterized through x-ray diffraction technology, transmission electron microscopy, and Mossbauer spectroscopy. The results show that surface grains are refined to 15 nm in average size after 60 min of attrition. The surface grains present inhomogeneity due to the nonuniform plastic deformation when the attrition time is less than 15 min. Large quantities of dislocations and tangles of dislocations are observed in those larger grains. Al8Cr5 phase forms on the surface of Fe3Al samples which have undergone attrition for less than 15 min. When the attrition time increases, the Al8Cr5 phase becomes disordered and dissolves into the matrix. In addition, disordering of Fe3Al occurs only in a very thin area during severe plastic deformation.
Ren, Jiangwei; Li, Dong; Xu, Peiquan
Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides
NASA Technical Reports Server (NTRS)
A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.
Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)
Structure, magnetostatic properties, and microwave characteristics of mechanoactivated nanocrystalline Fe and Fe-Si powders
The effect of the chemical composition and structural and morphological features of Fe and Fe87Si13 powders milled in an inert atmosphere of Ar and a 3% solution of oleic acid in heptane (H + OA) on the magnetostatic and\\u000a microwave properties has been studied in this work. Irrespective of the milling medium, all the samples were nanocrystalline.\\u000a The powder particles
E. P. Elsukov; K. N. Rozanov; S. F. Lomaeva; A. V. Osipov; D. A. Petrov; D. V. Surnin; A. A. Chulkina; A. S. Shuravin
Effects of energetic heavy ion irradiation on hardness of Al-Mg-Si alloys
NASA Astrophysics Data System (ADS)
Al-Mg-Si alloys were irradiated with 5.4 MeV Al ions, 7.3 MeV Fe ions, 10 MeV I ions, and 16 MeV Au ions at room temperature and the Vickers microhardness was measured. The hardness of Al-Mg-Si alloys increases with increasing the ion fluence. In a viewpoint of ion fluence, hardness change of the Al alloys is different by the kind of irradiating ions. But, in a viewpoint of the density of elastically deposited energy, the effect of the four kinds of them on hardness is almost the same. This result means that the effect of irradiation on hardness of Al-Mg-Si alloys is dominated by the elastically deposited energy. The microstructure of the ion-irradiated specimens were investigated by means of three-dimensional atom probe (3DAP). The experimental result was compared with the microstructure and the hardness for thermally aged specimens. We also discuss the difference in ion-irradiation induced change in hardness between Al-Mg-Si alloys and Al-Cu-Mg alloys (duralumin).
Ueyama, D.; Saitoh, Y.; Hori, F.; Kaneno, Y.; Nishida, K.; Dohi, K.; Soneda, N.; Semboshi, S.; Iwase, A.
Surface acoustic wave devices on AlN/3C-SiC/Si multilayer structures
NASA Astrophysics Data System (ADS)
Surface acoustic wave (SAW) propagation characteristics in a multilayer structure including a piezoelectric aluminum nitride (AlN) thin film and an epitaxial cubic silicon carbide (3C-SiC) layer on a silicon (Si) substrate are investigated by theoretical calculation in this work. Alternating current (ac) reactive magnetron sputtering was used to deposit highly c-axis-oriented AlN thin films, showing the full width at half maximum (FWHM) of the rocking curve of 1.36° on epitaxial 3C-SiC layers on Si substrates. In addition, conventional two-port SAW devices were fabricated on the AlN/3C-SiC/Si multilayer structure and SAW propagation properties in the multilayer structure were experimentally investigated. The surface wave in the AlN/3C-SiC/Si multilayer structure exhibits a phase velocity of 5528 m s-1 and an electromechanical coupling coefficient of 0.42%. The results demonstrate the potential of AlN thin films grown on epitaxial 3C-SiC layers to create layered SAW devices with higher phase velocities and larger electromechanical coupling coefficients than SAW devices on an AlN/Si multilayer structure. Moreover, the FWHM values of rocking curves of the AlN thin film and 3C-SiC layer remained constant after annealing for 500 h at 540 °C in air atmosphere. Accordingly, the layered SAW devices based on AlN thin films and 3C-SiC layers are applicable to timing and sensing applications in harsh environments.
Lin, Chih-Ming; Chen, Yung-Yu; Felmetsger, Valery V.; Lien, Wei-Cheng; Riekkinen, Tommi; Senesky, Debbie G.; Pisano, Albert P.
Magnetic Evolution with Composition on Fe-rich Fe-Al Alloys by Moessbauer spectroscopy
Fe-Al alloys have ferromagnetic properties up to 33 at %Al at room temperature and then become paramagnetic at higher Al concentrations. While up to about 20 at % Al the magnetization decreases following a simple dilution law, at higher Al concentrations it falls rapidly until it disappears. Moessbauer spectroscopy and magnetic measurements indicate that the ferromagnetic network present at the stoichiometric composition of D03 structure (25at.%Al) breaks down forming magnetic clusters that become smaller increasing Al content. The development of the clustering process takes place in a small concentration range (between 27.5% and 30.5 at % Al)
Rodriguez, D. Martin; Plazaola, F. [Elektrika eta Elektronika Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 P. K., 48080 Bilbao (Spain); Garitaonandia, J.S. [Fisika Aplikatua II Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 P. K., 48080 Bilbao (Spain)
Iron redox equilibria in CaO-Al 2 O 3 SiO 2 and MgO-CaO-Al 2 O 3 SiO 2 slags
Measurements have been made of the ratio of ferric to ferrous iron in CaO-Al2O3-SiO2 and MgO-CaO-Al2O3-SiO2 slags at oxygen activities ranging from equilibrium with pCO2\\/pCO?0.01 to as high as air at temperatures of 1573 to 1773 K. At 1773 K, values are given by \\u000a \\u000a \\u000a \\u000a \\u000a $$\\\\begin{gathered} \\\\log {\\\\text{ }}\\\\left( {\\\\frac{{Fe^{3 + } }}{{Fe^{2 + } }}} \\\\right) = 0.3( \\\\pm {\\\\text{
Lixiang Yang; G. R. Belton
Constraints on Al, Fe and Li Abundances in Mercury's Exosphere
NASA Astrophysics Data System (ADS)
Before the arrival of Messenger and Bepi Colombo at Mercury, the only source of information available on Mercury's environment is observations done from ground based observatories. We performed high spectral resolution observations of the Mercury's exosphere on the 30th and 31st October 2005 using the ESO-NTT telescope, La Silla, Chile. The large spectral range, 385-855 nm of the spectrograph EMMI provides a unique opportunity to search for non-identified species in the Hermian's environment. In this paper, we report a tentative detection of atomic aluminium in the exosphere of Mercury. This detection should be confirmed by further observations and can be used as an upper limit for this element in Mercury's exosphere. We also estimate upper limit for the column densities of Fe and Si exospheric atoms. Detection of Al, a refractory element, if confirmed, as well as its high exospheric abundance (between 2 to 18) with respect to Ca would suggest either an unexpected surface composition or a relation between exosphere and surface composition that is not well understood.
Doressoundiram, Alain; Leblanc, F.
Epitaxial BiFeO3 thin films on Si
BiFeO3 was studied as an alternative environmentally clean ferro\\/piezoelectric material. 200-nm-thick BiFeO3 films were grown on Si substrates with SrTiO3 as a template layer and SrRuO3 as bottom electrode. X-ray and transmission electron microscopy studies confirmed the epitaxial growth of the films. The spontaneous polarization of the films was ~45 muC\\/cm2. Retention measurement up to several days showed no decay
J. Wang; H. Zheng; Z. Ma; S. Prasertchoung; M. Wuttig; R. Droopad; J. Yu; K. Eisenbeiser; R. Ramesh
Magnetism in icosahedral Al 44Mn 26Si 30
NASA Astrophysics Data System (ADS)
AC susceptibility studies on quasicrystalline Al 44Mn 26Si 30 are presented in the temperature range 4.2-260 K. The susceptibility curve shows a broad peak ( Tp) that shifts to higher temperatures as the ac susceptibility frequency is increased, which is an indication of presence of spin glass behaviour in these high Si containing quasicrystalline alloys.
Srinivas, V.; Ramakrishnan, S.; Chandra, Girish; Dunlap, R. A.
Microstructures and mechanical properties of Fe–Al–Ta alloys with strengthening Laves phase
The addition of Ta to Fe–Al alloys results in the formation of a stable Ta(Fe,Al)2 Laves phase with hexagonal C14 structure in the Fe–Al phase at temperatures of 800, 1000 and 1150 °C. It was found that the solubility of Ta in Fe–Al is generally low and the solubility of Ta varies with Al content. Respective isothermal sections of the Fe–Al–Ta
D. D. Risanti; G. Sauthoff
Microstructure and Wear Behavior of Solidification Sonoprocessed B390 Hypereutectic Al-Si Alloy
NASA Astrophysics Data System (ADS)
The hypereutectic Al-Si alloys constitute an important family of alloys because of their excellent wear resistance and low thermal expansion. However, the optimal microstructure and hence the optimal service performance of these alloys cannot be achieved by the conventional melt treatments used in industry today, because of the chemical incompatibility between the primary-Si refiners and the eutectic-Si modifiers used in microstructure control. The current study aimed at using ultrasonic vibrations to improve the microstructure and the properties of these alloys. The results of the current study showed that for the B390 Al-Si alloy (i) the ultrasonic treatment has potential refining effect on the primary Si and Fe intermetallic phases, (ii) the primary Si particles become finer as the pouring temperature decreases from 1033 K (760 °C) to 938 K (665 °C), (iii) pouring and ultrasonic treatment at temperatures below the start of primary Si precipitation result in the coexistence of large and fine Si particles in microstructure, (iv) phosphorous additions of 50 ppm did not show any substantial effect in the ultrasonically treated ingots, (v) ultrasonic-treated samples have uniform hardness over the surface while the untreated samples show large scattering (high standard deviation) in hardness levels and (vi) ultrasonic-treated samples showed better wear resistance in the absence of phosphorous.
Khalifa, Waleed; El-Hadad, Shimaa; Tsunekawa, Yoshiki
Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3SiO2-CaO-MgO-Al2O3 System at PO2 10-8 atm
Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper
Hector M. Henao; Colin Nexhip; David P. George-Kennedy; P. C. Hayes; E. Jak
SiAlON ceramic compositions and methods of fabrication
A method of fabricating a SiAlON ceramic body includes: (a) combining quantities of Si[sub 3]N[sub 4], Al[sub 2]O[sub 3] and CeO[sub 2] to produce a mixture; (b) forming the mixture into a desired body shape; (c) heating the body to a densification temperature of from about 1,550 C to about 1,850 C; (d) maintaining the body at the densification temperature for a period of time effective to densify the body; (e) cooling the densified body to a devitrification temperature of from about 1,200 C to about 1,400 C; and (f) maintaining the densified body at the devitrification temperature for a period of time effective to produce a [beta][prime]-SiAlON crystalline phase in the body having elemental or compound form Ce incorporated in the [beta][prime]-SiAlON crystalline phase. Further, a SiAlON ceramic body comprises: (a) an amorphous phase; and (b) a crystalline phase, the crystalline phase comprising [beta][prime]-SiAlON having lattice substituted elemental or compound form Ce.
O'Brien, M.H.; Park, B.H.
Combinatorial investigation of magnetostriction in Fe-Ga and Fe-Ga-Al
NASA Astrophysics Data System (ADS)
A high-throughput high-sensitivity optical technique for measuring magnetostriction of thin-film composition-spread samples has been developed. It determines the magnetostriction by measuring the induced deflection of micromachined cantilever unimorph samples. Magnetostriction measurements have been performed on as-deposited Fe-Ga and Fe-Ga-Al thin-film composition spreads. The thin-film Fe-Ga spreads display a similar compositional variation of magnetostriction as bulk. A previously undiscovered peak in magnetostriction at low Ga content was also observed and attributed to a maximum in the magnetocrystalline anisotropy. Magnetostrictive mapping of the Fe-Ga-Al ternary system reveals the possibility of substituting up to 8 at. % Al in Fe70Ga30 without significant degradation of magnetostriction.
Hattrick-Simpers, Jason R.; Hunter, Dwight; Craciunescu, Corneliu M.; Jang, Kyu Sung; Murakami, Makoto; Cullen, James; Wuttig, Manfred; Takeuchi, Ichiro; Lofland, Samuel E.; Benderksy, Leonid; Woo, Noble; van Dover, Robert Bruce; Takahashi, Toshiya; Furuya, Yasubumi
Structural behaviour of Al–Si die-castings: Experiments and numerical simulations
Axial crushing and three-point bending tests have been performed in order to establish an experimental database of the behaviour of generic high-pressure die-cast (HPDC) Al–Si alloys. The experimental data are used to obtain a validated methodology for finite element modelling of thin-walled cast components subjected to quasi-static loading. The HPDC structural components are modelled in the non-linear explicit FE-code LS-DYNA
C. Dorum; H. I. Laukli; O. S. Hopperstad; M. Langseth
Structure and properties of hypoeutectic Al-Si-Mg alloys modified with pure strontium
Pure metallic strontium has been used as a modifier for A356.0 alloys, and the relationship between microstructure and mechanical\\u000a properties has been established. It is shown that mechanical properties depend on both the cooling rate and the amount of\\u000a strontium in the melt. The effect of other elements (Fe, Mg) on the microstructure of strontium modified Al-Si-Mg hypoeutectic\\u000a alloys has
B. Closset; J. E. Gruzleski
Sliding wear behavior of some Al-Si alloys: Role of shape and size of Si particles and test conditions
In this investigation, effects of the shape and size of silicon particles have been studied on the sliding wear response of two Al-Si alloys, namely, LM13 and LM29. The LM13 alloy comprised 11.70% Si, 1.02% Cu, 1.50% Ni, 1.08% Mg, 0.70% Fe, 0.80% Mn, and remainder Al. The LM29 alloy contained 23.25% Si, 0.80% Cu, 1.10% Ni, 1.21% Mg, 0.71% Fe, 0.61% Mn, and remainder Al. Wear tests were conducted under the conditions of varying sliding speed and applied pressure. The alloys were also characterized for their microstructural features and mechanical properties. The presence of primary silicon particles in the alloy led to a higher hardness but lower tensile properties. Further, refinement in the size of the primary particles improved the mechanical properties of the alloy system. The wear behavior of the alloys was influenced by the presence of primary Si particles and was a function of their size. Samples with refined but identical microconstituents (e.g., pressure cast vs gravity cast LM29 in terms of the size of primary Si particles and dendritic arm spacing) exhibited better wear characteristics. Their overall effect was further controlled by the test conditions. The study suggests that shape, size, microcracking tendency, and thermal stability of different microconstituents greatly control the mechanical and tribological properties of these alloys. The extent of effective load transfer between the phases plays an important role in this regard. Further, The overall effect of these factors is significantly governed by the test conditions.
Prasad, B.K.; Modi, O.P.; Jha, A.K.; Das, S.; Dasgupta, R.; Yegneswaran, A.H. [Regional Research Lab., Bhopal (India); Venkateswarlu, K. [National Metallurgical Lab., Jamshedpur (India)
Effect of iron on the crystal structure of (Mg,Fe)SiO sub 3 perovskite
The perovskite form of Mg{sub 0.981},Fe{sub 0.028}Cr{sub 0.011}Si{sub 0.979}O{sub 3}, quenched from 26 GPa and 2,173 K in a uniaxial split-sphere-type high-pressure apparatus, was studied at the SUNY X3A beamline at the National Synchrotron Light Source. With a Si (111) double-crystal monochromator and a single crystal of perovskite measuring 29{times}29{times}43 {mu}m, intensities of 127 independent reflections were collected with sin {theta}/{lambda} < 0.60 {angstrom}{sup {minus}1} and I{sub o} > 3.5{sigma}{sub I}. This is the first-reported single-crystal diffraction study of a Mg-silicate perovskite containing a significant amount of Fe or other cations. The unit cell parameters obtained through the refinement of 30 reflections are: a = 4.7823(3), b = 4.9331(3), c = 6.9026(8) {angstrom}, V = 162.84(2) {angstrom}{sup 3}. The result of structural refinement in space group Pbnm indicates that Fe and a small amount of Cr substitute for Mg rather than for Si, contrary to the result of Jackson et al. (1987) who reported Fe in the octahedral site of a perovskite synthesized at 50 GPa and 2,000 K in a diamond-anvil cell with laser heating.
Kudoh, Y.; Prewitt, C.T.; Finger, L.W. (Carnegie Institute of Washington, DC (USA)); Darovskikh, A. (Brookhaven National Laboratory, Upton, NY (USA)); Ito, E. (Okayama Univ., Misasa (Japan))
Skyrmion Lattice Domains in Fe1-xCoxSi
NASA Astrophysics Data System (ADS)
The strongly doped semiconductor Fe1-xCoxSi displays a dome of helimagnetic order for 0.05 <= x <= 0.7. We report small angle neutron scattering of the magnetic structure in the skyrmion lattice phase of Fe1-xCoxSi for x = 0.2 and magnetic field parallel to a crystallographic (100) direction. We observe twelve equally spaced maxima of scattering intensity on a ring, with an underlying six-fold symmetry of two sets of six spots. The intensity distribution suggests the formation of two degenerate skyrmion lattice domain populations with respect to the four-fold symmetry of the (100) directions in the scattering plane.
Adams, T.; Mühlbauer, S.; Neubauer, A.; Münzer, W.; Jonietz, F.; Georgii, R.; Pedersen, B.; Böni, P.; Rosch, A.; Pfleiderer, C.
The Sintering, Sintered Microstructure and Mechanical Properties of Ti-Fe-Si Alloys
NASA Astrophysics Data System (ADS)
A systematic study has been conducted of the sintering, sintered microstructure and tensile properties of a range of lower cost Ti-Fe-Si alloys, including Ti-3Fe-(0-4)Si, Ti-(3-6)Fe-0.5Si, and Ti-(3-6)Fe-1Si (in wt pct throughout). Small additions of Si (?1 pct) noticeably improve the as-sintered tensile properties of Ti-3Fe alloy, including the ductility, with fine titanium silicides (Ti5Si3) being dispersed in both the ? and ? phases. Conversely, additions of >1 pct Si produce coarse and/or networked Ti5Si3 silicides along the grain boundaries leading to predominantly intergranular fracture and, hence, poor ductility, although the tensile strength continues to increase because of the reinforcement by Ti5Si3. Increasing the Fe content in the Ti- xFe-0.5/1.0Si alloys above 3 pct markedly increases the average grain size and changes the morphology of the ?-phase phase to much thinner and more acicular laths. Consequently, the ductility drops to <1 pct. Si reacts exothermically with Fe to form Fe-Si compounds prior to the complete diffusion of the Fe into the Ti matrix during heating. The heat thus released in conjunction with the continuous external heat input melts the silicides leading to transient liquid formation, which improves the densification during heating. No Ti-TiFe eutectoid was observed in the as-sintered Ti-Fe-Si alloys. The optimum PM Ti-Fe-Si compositions are determined to be Ti-3Fe-(0.5-1.0)Si.
Yang, Y. F.; Luo, S. D.; Schaffer, G. B.; Qian, M.
Grain refinement mechanisms of hypoeutectic Al-Si alloys
The general concept of the grain refinement mechanism in hypoeutectic Al-Si alloys has been adopted from that in wrought alloys without consideration of the influence of the silicon content. In the present investigation the commercial grain refinement practice in Al-Si foundry alloys has been experimentally simulated by introducing synthetic TiB{sub 2} crystals directly into Al-Si melts. To explore the possible use of a new generation of Al-Ti-C master alloys in these alloys, the behavior of synthetic TiC has also been studied. Experimental findings indicate that in the presence of Si, TiC crystals are highly unstable in aluminium melts. TiB{sub 2} crystals alone do not nucleate the {alpha}-phase, whereas in the presence of dissolved Ti a ternary Al-Ti-Si interfacial layer is formed on the TiB{sub 2} which subsequently nucleates the {alpha}-Al, via a peritectic reaction. However, due to a drastic decrease in the peritectic temperature, the efficiency of grain refinement is greatly reduced. A theoretical analysis indicates that when boron is added in excess of TiB{sub 2} stoichiometry, or simply as AlB{sub 2}, grain refinement occurs by a eutectic reaction.
Mohanty, P.S.; Gruzleski, J.E. [McGill Univ., Montreal, Quebec (Canada). Dept. of Mining and Metallurgical Engineering] [McGill Univ., Montreal, Quebec (Canada). Dept. of Mining and Metallurgical Engineering
Interdiffusion in Diffusion Couples: U-Mo v. Al and Al-Si
Interdiffusion and microstructural development in the U-Mo-Al system was examined using solid-tosolid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, annealed at 600°C for 24 hours. The influence of Si alloying addition (up to 5 wt.%) in Al on the interdiffusion microstructural development was also examined using solid-to-solid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, Al-2wt.%Si, and Al-5wt.%Si annealed at 550°C up to 20 hours. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase intermetallic layer. In ternary U-Mo-Al diffusion couples annealed at 600°C for 24 hours, interdiffusion microstructure varied of finely dispersed UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases while the average composition throughout the interdiffusion zone remained constant at approximately 80 at.% Al. Interdiffusion microstructure observed by SEM/TEM analyses and diffusion paths drawn from concentration profiles determined by EPMA appear to deviate from the assumption of "local thermodynamic equilibrium," and suggest that interdiffusion occurs via supersaturated UAl4 followed by equilibrium transformation into UAl3, U6Mo4Al43, UAl4 and UMo2Al20 phases. Similar observation was made for U-Mo vs. Al diffusion couples annealed at 550°C. The addition of Si (up to 5 wt.%) in Al significantly reduced the thickness of the intermetallic layer by changing the constituent phases of the interdiffusion zone developed in U-Mo vs. Al-Si diffusion couples. Specifically, the formation of (U,Mo)(Al,Si)3 with relatively large solubility for Mo and Si, along with UMo2Al20 phases was observed along with disappearance of U6Mo4Al43 and UAl4 phases. Simplified understanding based on U-Al, U-Si, and Mo-Si binary phase diagrams is discussed in the light of the beneficial effect of Si alloying addition.
D. D. Keiser, Jr.; E. Perez; B. Yao; Y. H. Sohn
Oxidation kinetics of fayalite (Fe 2 SiO 4 )
Single crystals of fayalite (Fe2SiO4) have been oxidized either in the hematite or the magnetite stability field to investigate the kinetics and mechanisms of oxidation. For samples heated in air at 770° C, a two-phase region composed of fine-grained iron oxide and silica phases formed as the reaction front moved into the sample, and an iron oxide layer formed external
Stephen J. Mackwell
Electromagnetic and microwave absorbing properties of raw and milled FeSiCr particles
NASA Astrophysics Data System (ADS)
FeSiCr alloy (Fe: 90%, Si: 7.9%, and Cr: 2.1%) with pre-milled flaky shape was re-milled in a planetary ball-mill for 30 h. The complex permittivity (?'-j??) and permeability (?'-j??) are measured by using the transmission/reflection method for two different aspect ratios of flake-shaped FeSiCr/epoxy composites for 30%, 40%, and 50% weight ratios. Dielectric loss tangent and magnetic loss tangent of re-milled FeSiCr powder show larger electromagnetic wave energy dissipation than those of the raw flaky FeSiCr powder. For 30 wt. % of FeSiCr/epoxy absorbers with 2 mm thickness, the calculated reflection loss reaches -25 dB at 13.0 GHz for raw flaky powder, -40 dB at 11.4 GHz for the re-milled FeSiCr powder with higher aspect ratios.
Yang, R. B.; Liang, W. F.; Chen, C. C.; Choi, S. T.
Enhanced microwave absorption properties of Fe3Al\\/Al2O3 fine particle composites
Fe3Al\\/Al2O3 composites were prepared by mechanochemical synthesis using a mixture of Fe2O3, Al and Fe as the starting material. Microwave characteristics were measured in the range 0.1-18 GHz. A reflection loss (RL) exceeding -20 dB in the frequency range 7.2-17.4 GHz was achieved for an absorber of 1.5-2.5 mm. An optimal RL of -45 dB was obtained at 8.9 GHz
Jianqiang Wei; Jianbo Wang; Qingfang Liu; Liang Qiao; Tao Wang; Fashen Li
Friction and wear behavior of Ti following laser surface alloying with Si, Al and Si+Al
This study concerns the friction and wear behavior of Ti following laser surface alloying (LSA) with Si, Al or Si+Al. The said tribological characteristics of the laser-alloyed samples, subjected to the earlier determined optimum conditions of LSA, were investigated in terms of the variation of wear depth as a function of load and time using a computer-controlled reciprocating ball-on-disc wear
J. Dutta Majumdar; B. L Mordike; I Manna
Absorption and desorption of hydrogen in Fe-40Al intermetallic
The present research was performed in an attempt to study the kinetics of hydrogen diffusion based on the results on hydrogen content measurements in B2 FeAl after heat treatment. A temperature-programmed hydrogen release test was also undertaken to investigate the existing states of hydrogen in FeAl. The single crystals and polycrystals of Fe-40Al were used for this experiment. Through a heat treatment in vacuum the hydrogen concentration in a Fe-40Al single crystal can be decreased significantly, while the hydrogen content increases significantly when the crystal is exposed in air at room temperature. The change of hydrogen content can be described as C{sub H} = C{sub s} {minus} C{sub 0}/2{pi}L {radical}Dt + C{sub 0}. The estimated hydrogen diffusivity for the Fe-40Al single crystal at room temperature is about 10{sup {minus}9} cm{sup 2}/s. It is revealed that hydrogen can be trapped in a vacancy or bonded inside the lattice of the single crystal. Because of the difference in stability, two different release temperatures are observed for hydrogen in a vacancy and hydrogen bonded in the lattice. The lattice hydrogen shows the highest stability. Grain boundaries also act as hydrogen condensation sites and hydrogen in grain boundaries possesses higher stability than in the vacancy.
Yang, Y.; Hanada, S. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research] [Tohoku Univ., Sendai (Japan). Inst. for Materials Research
Magnetic properties of Fe and Fe-Si alloys with {100}<0vw> texture
NASA Astrophysics Data System (ADS)
When iron and its alloy sheets with clean metal surfaces undergo the ? to ? phase transformation, they develop strong {100}<0vw> texture with grain size being larger than the sheet thickness. For example, when Fe or Fe-1%Si sheets were subjected to the ? to ? phase transformation in a reducing gas atmosphere (hydrogen gas having the dew point below -50 °C), strong {100}<0vw> texture developed. Magnetic properties of Fe and Fe-Si alloys show that, by developing the {100}<0vw> texture, the core loss can be reduced by more than 25% and the permeability can be increased by 2-5 times. With 0.35 mm-thick Fe-1%Si with the {100}<0vw> texture, the magnetic properties are W15/50 (core loss at 1.5 T, 50 Hz) = 2.7 W/kg and B50 (magnetic flux density at 5000 A/m) = 1.80 T. The improvement of permeability together with reducing iron loss by texture control will make a significant contribution to improving power density as well as reducing copper losses in induction motors.
Kyung Sung, Jin; Mo Koo, Yang
Structural characterization by electronic transport properties on Fe3Si films
NASA Astrophysics Data System (ADS)
We have investigated the electronic transport properties of resistivity, magnetoresistance and the Hall effect on epitaxial and polycrystalline Fe3Si thin films. The electrical transport measurements reveal the microstructure which has not been clarified from x-ray diffraction and/or scanning electron microscopy. We show that (1 0 0)-oriented epitaxial film 36 nm thick on MgO(1 1 1) exhibits ferromagnetic-tunnelling conduction, (1 1 0)-oriented epitaxial film 36 nm thick on yttria stabilized zirconia [YSZ(1 1 1)] is in a percolated region, and polycrystalline film 36 nm thick on Al2O3(1 1 0) and (1 0 0)-oriented epitaxial film 150 nm thick on MgAl2O4(1 0 0) have metallic conduction. These results imply that the electrical transport measurements are a powerful tool for evaluating the microstructure of the samples. The coefficients of the skew and the side-jump scatterings in the extraordinary Hall effect, and the quadratic temperature coefficient of resistivity observed on (1 0 0)-oriented epitaxial film 150 nm thick on MgAl2O4 show that Fe3Si is a ferromagnetic metal where the effective electron mass is slightly enhanced compared with Fe, Co and Ni due to the electron-electron correlation.
Kobayashi, Y.; Kaneko, T.; Kamogawa, M.; Asai, K.; Akiyama, K.; Funakubo, H.
A polarized neutron study of the magnetization distribution in Co?FeSi.
The magnetization distribution in Co2FeSi which has the largest moment per formula unit ?6 ?B of all Heusler alloys, has been determined using polarized neutron diffraction. The experimentally determined magnetization has been integrated over spheres centred on the three sites of the L12 structure giving ? Fe = 3.10(3) ?B and ? Co = 1.43(2) ?B, results which are slightly lower than the moments in atomic spheres of similar radii obtained in recent LDA + U band structure calculations (Li et al 2010 Chin. Phys. B 19 097102). Approximately 50% of the magnetic carriers at the Fe sites were found to be in orbitals with eg symmetry. This was higher, ?65%, at the Co sites. Both Fe and Co were found to have orbital moments that are larger than those predicted. Comparison with similar results obtained for related alloys suggests that there must be a finite density of states in both spin bands at the Fermi energy indicating that Co2FeSi is not a perfect half-metallic ferromagnet. PMID:23612471
Brown, P J; Kainuma, R; Kanomata, T; Neumann, K-U; Okubo, A; Umetsu, R Y; Ziebeck, K R A
Temperature dependence of the exchange coupling in CO/SI(or Ge)/Fe trilayers
NASA Astrophysics Data System (ADS)
The temperature dependences of interfacial exchange coupling in Co/semiconductor (SM)/Fe trilayers (SM?Si or Ge) with different spacer thicknesses are investigated. Only one step is found in the third (not in the first) quadrant of the hysteresis loop of the trilayers with different SM thicknesses, which is ascribed to a larger interfacial coupling strength of Co/CoGe (or Co/CoSi) than of Fe/FeGe (or Fe/FeSi). Furthermore, in comparison with Co/Ge/Fe, a smaller exchange bias field HE and no clear step are observed in Co/Si/Fe, which may originate from the weaker interfacial coupling in this trilayer. The variation of coercivity HC with spacer thickness at low temperatures in Co/Ge/Fe is different from that in Co/Si/Fe, indicating again the important effect of the SM layer in the trilayers.
Liu, X. H.; Liu, W.; Guo, S.; Lv, X. K.; Gong, W. J.; Zhang, Z. D.
Mechanochemical Behavior of NiO-Al-Fe Powder Mixtures to Produce (Ni, Fe)3Al-Al2O3 Nanocomposite Powder
NASA Astrophysics Data System (ADS)
(Ni, Fe)3Al-30 vol pct Al2O3 nanocomposite powder was synthesized by mechanochemical reaction of Fe-NiO-Al powder mixtures. Structural evolution during mechanical alloying was studied by employing X-ray diffractometry (XRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM). After 78 minutes of milling, the (Ni, Fe)3Al-30 vol pct Al2O3 nanocomposite can be synthesized by reaction 3Fe + 7Al + 6NiO with a combustion mode. DTA results revealed that milling for 60 minutes decreases the temperature of reaction from 1040 K to 898 K (767 °C to 625 °C). TEM images corroborate a homogenous dispersion of reinforcements in the matrix of the nanocomposite proving that the reduction in the crystallite size of both reinforcements and matrix is within the nanometer range.
Adabavazeh, Z.; Karimzadeh, F.; Enayati, M. H.
Formation and magnetic properties of Fe-B-Si amorphous alloys
The magnetic properties and crystallization temperatures of alloys in the ternary Fe-B-Si system are reported. The Curie temperature increases slightly on replacement of boron by silicon. This results in a sharp ridge of relatively constant room-temperature saturation magnetization extending from Fe80B20to Fe82B12Si6. The coercivity exhibits a broad minimum, both before and after stress relief annealing, in the region around Fe81B15Si4and
F. Luborsky; J. Becker; J. Walter; H. Liebermann
Interferometric Measurement of Resonance Transition Wavelengths in C IV, Si IV, Al III, Al II, and Si II
NASA Astrophysics Data System (ADS)
We have made the first interferomeric measurements of the wavelengths of the important ultraviolet diagnostic lines in the spectra C IV near 155 nm and Si IV near 139 nm with a vacuum ultraviolet Fourier transform spectrometer and high-current discharge sources. The wavelength uncertainties were reduced by 1 order of magnitude for the C IV lines and by 2 orders of magnitude for the Si IV lines. Our measurements also provide accurate wavelengths for resonance transitions in Al III, Al II, and Si II.
Griesmann, Ulf; Kling, Rainer
The corrosion behavior of Fe-Mn-Al weld metals
NASA Astrophysics Data System (ADS)
The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.
Aidun, Daryush K.
Structure, Bonding, and Adhesion of Materials Interfaces With Density Functional Theory: Cr/Fe, SiC/Fe, MoSi2/Ni.
National Technical Information Service (NTIS)
SiC/Fe and MoSi2/Ni interfaces are investigated using first principles calculations in order to determine the structure of the interfaces and calculate ideal adhesion energies. As a baseline for comparison, calculations were also performed on the Cr/Fe in...
D. F. Johnson E. A. Carter
NaAlSi: An Unusual Self-Doped Semimetal With Free Electrons and Covalent Holes
NASA Astrophysics Data System (ADS)
The ternary compound NaAlSi is a layered sp conductor that superconducts at a relatively high Tc of 7 K. Using first principles electronic structure calculations (the FPLO code), we find that NaAlSi is a self-doped semimetal with several unusual characteristics (in addition to the interesting fact that its structure is the same as those of the Fe-pnictide 111 coupounds). Na gives up its electron, allowing the Si-Al sublayer to form a distinct set of covalent valence bands, which are nearly filled. A strongly directional, Al-derived free electron band overlaps the valence bands, providing the electron carriers. The kz dispersion is small, but it occurs at the Fermi level, leading to unusual Fermi surfaces. Wannier functions will be provided to assist in the understanding of the bonding, and comparison with the CaAlSi compound, with one additional electron and a different structure (the MgB2 structure) will be presented.
Rhee, Hahnbidt; Banerjee, Swapnonil; Ylvisaker, Erik; Pickett, Warren
Experimental studies on the ignition of single Ni\\/Al, Fe\\/Al, and Ti particles
The work presented here focuses on the ignition of single Ni- and Fe-coated Al particles in pure CO2 and Ar atmospheres and Ti particles in O2\\/N2 and O2\\/Ar environments. The importance of studying Ni- and Fe-coated Al particles is related to their potential use in propulsion and materials synthesis applications. Meanwhile, Ti combustion may be utilized to eliminate hazardous chemical
Timothy Al Andrzejak
27Al-NQR\\/NMR Study of Kondo Semiconductor CeFe2Al10
27Al-NQR\\/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1\\/T1 above about 20
Yukihiro Kawamura; Shingo Edamoto; Tomoaki Takesaka; Takashi Nishioka; Harukazu Kato; Masahiro Matsumura; Yo Tokunaga; Shinsaku Kambe; Hiroshi Yasuoka
Atomically controlled molecular beam epitaxy of ferromagnetic silicide Fe{sub 3}Si on Ge
Low-temperature (60 deg. C) molecular beam epitaxy (MBE) of Fe{sub 3}Si layers on Ge substrates was investigated. From x-ray diffraction and transmission electron microscopy measurements, it was shown that Fe{sub 3}Si layers including the DO3 type were epitaxially grown on Ge(110) and Ge(111), while polycrystal Fe{sub 3}Si was formed on Ge(100). Although the Fe{sub 3}Si/Ge(110) interface was slightly rough ({approx}1 nm), the Fe{sub 3}Si/Ge(111) interface was atomically flat. Such atomically controlled MBE of Fe{sub 3}Si on the Ge(111) substrate can be employed to realize Ge channel spin transistors, which can be integrated with Si large-scale integrated circuits.
Sadoh, T.; Kumano, M.; Kizuka, R.; Ueda, K.; Kenjo, A.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan)
First-principles study of the Co2FeSi(001) surface and Co2FeSi/GaAs(001) interface
NASA Astrophysics Data System (ADS)
Ab initio study of the electronic and magnetic properties of bulk Co2FeSi , free Co2FeSi(001) surfaces, and its interfaces with GaAs(001) substrate are reported. The bulk computations indicate that the LSDA+U scheme is necessary to reproduce the measured total magnetic moments and to observe a half-metallic behavior. The thermodynamic stability of various Co2FeSi(001) surface and Co2FeSi/GaAs(001) interface terminations are studied in the framework of ab initio thermodynamics. The calculated surface phase diagram indicates that by tuning the atomic chemical potentials, three different terminations are probable. The obtained interface diagrams argue the possibility of the formation of mixed interfaces. The spin-polarized density of states shows that the half metallicity confirmed in the bulk Co2FeSi is lost at its surfaces and interfaces with GaAs(001).
Khosravizadeh, Sh.; Hashemifar, S. Javad; Akbarzadeh, Hadi
Effect of Antimony on the Interfaces of Cast AlSi-SiC Composites.
National Technical Information Service (NTIS)
When the matrix alloy of an AlSi7Mg - SiC composite has been modified with antimony, the wetting properties deteriorate. By transmission electron microscopy and microanalysis it is found that this is probably related to the formation of a film-like amorph...
A. Bardal
Magnetic force microscopy of ferromagnetic nanoparticles formed in Al2O3 and SiO2 by ion implantation
Magnetic force microscopy (MFM) has been used to investigate the properties of ferromagnetic FePt nanoparticles produced by the implantation of Fe and Pt ions into single-crystal Al2O3 or fused SiO2 followed by thermal processing. The MFM results are compared to cross-section and plan view transmission electron microscopy images of the same samples. We demonstrate that MFM can detect magnetism in
C. E. Vallet; C. W. White; S. P. Withrow; J. D. Budai; L. A. Boatner; K. D. Sorge; J. R. Thompson; K. S. Beaty; A. Meldrum
(Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units
An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.
Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)
(Si)5-2y(AlP)y alloys assembled on Si(100) from Al-P-Si3 building units
NASA Astrophysics Data System (ADS)
An original class of IV/III-V hybrid (Si)5-2y(AlP)y/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH3)3 and atomic Al yielding tetrahedral ``Al-P-Si3'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.
Watkins, T.; Jiang, L.; Xu, C.; Chizmeshya, A. V. G.; Smith, D. J.; Menéndez, J.; Kouvetakis, J.
FeAl-TiC and FeAl-WC composites - melt infiltration processing, microstructure and mechanical properties
TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (> 97 % theoretical density). Phase equilibria calculations in the quaternary Fe-Al-Ti-C and Fe-Al-W-C systems at 145{degrees}C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc{trademark} and the results show that molten Fe-40 at.% Al in equilibrium with Ti{sub 0.512}C{sub 0.488} and graphite, dissolves 4.9 at% carbon and 64 atomic ppm titanium. In the Fe-Al-W-C system, liquid Fe-40 at.% Al in equilibrium with graphite dissolves about 5 at.% carbon and 1 at.% tungsten. Due to the low values for the solubility of the carbide phases in liquid iron aluminide, liquid phase sintering of mixed powders does not yield a dense, homogeneous microstructure for carbide volume fractions greater than 0.70. Melt infiltration of molten FeAl into TiC and WC preforms serves as a successful approach to process cermets with carbide contents ranging from 70 to 90 vol. %, to greater than 97% of theoretical density. Also, the microstructures of cermets prepared by melt infiltration were very homogeneous. Typical properties such as hardness, bend strength and fracture toughness are reported. SEM observations of fracture surfaces suggest the improved fracture toughness to result from the ductility of the intermetallic phase. Preliminary experiments for the evaluation of the oxidation resistance of iron aluminide bonded cermets indicate that they are more resistant than WC-Co cermets.
Subramanian, R.; Schneibel, J.H.
Neutron diffraction study on site occupation of substitutional elements at sub lattices in Fe 3 Al intermetallics
The site occupation of substitutional elements Cr, Mo, Ti, Mn, Ni and Si at sublattices in DO3-type stoichiometric Fe3Al intermetallics, effect of the elements on magnetic moment of the unit cell, and tensile properties at room temperature have been determined my means of neutron diffractometry and mechanical measurement in vacuum. The experimental results indicate that Cr, Mo, and Ti atoms
Sun Zuqing; Yang Wangyue; Shen Lizhen; Huang Yuanding; Zhang Baisheng; Yang Jilian
Solid phases of FeSi to 45 GPa and 2500 K
NASA Astrophysics Data System (ADS)
FeSi remains solid up to 2300+-200 K between 22 and 45 GPa in a laser-heated diamond anvil cell, showing that addition of silicon does not cause a large amount of melting point depression (the melting temperature of Fe ranges from 2300 +- 200 K to 2700 +- 200 K between 22 and 45 GPa). While the phase that is stable at core conditions remains an open question, our data constrain the epsilon-B2 transition to 29 +- 1 GPa at all temperatures from 1200 K to 2300 K. Room temperature diffraction data are fit to a Birch-Murnaghan equation of state with V0 = 21.28(4) Å^3, K0 = 235(13) GPa and K0' = 3.2(6) (1-sigma uncertainties), tied to the equations of state of Ar and Ne used as pressure standards and media [Errandonea, et al., PRB, 73, 092106 (2006); Lin, et al., JGR, 108, 2045 (2010)]. The relatively low value of K0' matches that of epsilon-FeSi from Knittle and Williams, GRL, 15, 445 (1995), and suggests that an iron-silicon alloy may not be compatible with the density profile of the Earth's outer core.
Geballe, Z. M.; Jeanloz, R.
XAFS studies on a modified Al-Si hypoeutectic alloy
To understand the role of Sr in doped aluminium-silicon alloys, we have conducted for the first time, Sr- K edge XAFS measurements on Al-3%Si-0.04%Sr. Aluminium-Silicon alloys are widely used in automobile and aerospace applications. Modification of these alloys with addition of trace levels of Sr (200-400 ppm) results in changing the morphology of Si eutectic from \\
V. S. Prakash Srirangam; S. Chattopadhyay; T. Shibata; J. A. Kaduk; J. T. Miller; C. U. Segre; S. Shankar
The precipitation sequence in Al–Mg–Si alloys
Fine-scale precipitation that occurs during age hardening of Al alloy 6061 has been studied using differential scanning calorimetry (DSC), atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). It was found that the precipitation sequence is: independent clusters of Mg and Si atoms?co-clusters that contain Mg and Si atoms?small precipitates of unknown structure??? needle-shaped precipitates?B? lath-shaped precipitates and
G. A. Edwards; K. Stiller; G. L. Dunlop; M. J. Couper
Modification of hypoeutectic Al–Si alloys with scandium
The present study was undertaken to investigate the effects of Sc on the modification of Al6Si0.25Mg alloy. The two levels of scandium used were 0.2wt.% or 0.4wt.%. For each treated condition, the mean shape factor of eutectic Si was determined to quantify the level of the modification effect. It was found that a Sc addition of only 0.2wt.% modified eutectic
Wattanachai Prukkanon; Nakorn Srisukhumbowornchai; Chaowalit Limmaneevichitr
Irradiation mixing of Al into U{sub 3}Si
Thermal and irradiation induced intermixing of uranium silicide reactor fuels with the aluminum cladding is an important consideration in understanding their fission gas and fuel swelling behavior. The authors have used Rutherford backscattering to follow the behavior of an Al thin film on U{sub 3}Si and U{sub 3}Si{sub 2} during 1.5 MeV Kr ion irradiation at temperatures of 30 and 350 C. After an initial dose during which no intermixing occurs, the Al mixes quickly into U{sub 3}Si. The threshold dose is believed to be associated with an oxide layer between the Al and the uranium silicide. At 300 C and doses greater than threshold, rates of mixing and aluminide phase growth are extracted.
Birtcher, R.C.; Ding, F.R.; Kestel, B.J.; Baldo, P.M.; Zaluzec, N.J. [Argonne National Lab., IL (United States). Materials Science Div.
The effect of Fe-coverage on the structure, morphology and magnetic properties of ?-FeSi2 nanoislands.
Self-assembled ?-FeSi(2) nanoislands were formed using solid-phase epitaxy of low (~1.2 ML) and high (~21 ML) Fe coverages onto vicinal Si(111) surfaces followed by thermal annealing. At a resulting low Fe-covered Si(111) surface, we observed in situ, by real-time scanning tunneling microscopy and surface electron diffraction, the entire sequence of Fe-silicide formation and transformation from the initially two-dimensional (2 × 2)-reconstructed layer at 300?°C into (2 × 2)-reconstructed nanoislands decorating the vicinal step-bunch edges in a self-ordered fashion at higher temperatures. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface. Ex situ x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy indicated the formation of an ?-FeSi(2) island phase, in an ?-FeSi(2){112} // Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ~1.9 ?(B)/Fe atom at 4 K for the low Fe-coverage, indicating stronger ferromagnetic coupling of individual magnetic moments, as compared to high Fe-coverage, where the calculated moments were only ~0.8 ?(B)/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk ?-FeSi(2) phase, and may open new pathways to high-density magnetic memory storage devices. PMID:23154191
Tripathi, J K; Garbrecht, M; Kaplan, W D; Markovich, G; Goldfarb, I
The effect of Fe-coverage on the structure, morphology and magnetic properties of ?-FeSi2 nanoislands
NASA Astrophysics Data System (ADS)
Self-assembled ?-FeSi2 nanoislands were formed using solid-phase epitaxy of low (˜1.2 ML) and high (˜21 ML) Fe coverages onto vicinal Si(111) surfaces followed by thermal annealing. At a resulting low Fe-covered Si(111) surface, we observed in situ, by real-time scanning tunneling microscopy and surface electron diffraction, the entire sequence of Fe-silicide formation and transformation from the initially two-dimensional (2 × 2)-reconstructed layer at 300?°C into (2 × 2)-reconstructed nanoislands decorating the vicinal step-bunch edges in a self-ordered fashion at higher temperatures. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface. Ex situ x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy indicated the formation of an ?-FeSi2 island phase, in an ?-FeSi2{112} ? Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ˜1.9 ?B/Fe atom at 4 K for the low Fe-coverage, indicating stronger ferromagnetic coupling of individual magnetic moments, as compared to high Fe-coverage, where the calculated moments were only ˜0.8 ?B/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk ?-FeSi2 phase, and may open new pathways to high-density magnetic memory storage devices.
Tripathi, J. K.; Garbrecht, M.; Kaplan, W. D.; Markovich, G.; Goldfarb, I.
Natural dissociation of olivine to (Mg,Fe)SiO3 perovskite and magnesiowustite in a shocked Martian meteorite.
We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine (Fa(34-41)) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO(3) perovskite (Pv)+magnesiowüstite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular (Mg,Fe)SiO(3) Pv and Mw have 50-100 nm in diameter, and lamellar (Mg,Fe)SiO(3) Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, K(Pv/Mw) = [FeO/MgO]/[FeO/MgO](Mw), between (Mg,Fe)SiO(3) Pv and Mw in equigranular and lamellar textures are approximately 0.15 and approximately 0.78, respectively. The dissociation of olivine implies that the pressure and temperature conditions recorded in the shock melt vein and melt pockets during the dynamic event were approximately 25 GPa but 700?°C at least. PMID:21444781
Miyahara, Masaaki; Ohtani, Eiji; Ozawa, Shin; Kimura, Makoto; El Goresy, Ahmed; Sakai, Takeshi; Nagase, Toshiro; Hiraga, Kenji; Hirao, Naohisa; Ohishi, Yasuo
Processing and properties of FeAl-bonded composites
Iron aluminides are thermodynamically compatible with a wide range of ceramics such as carbides, borides, oxides, and nitrides, which makes them suitable as the matrix in composites or cermets containing fine ceramic particulates. For ceramic contents varying from 30 to 60 vol.%, composites of Fe-40 at. % Al with WC, TiC, TiB{sub 2}, and ZrB{sub 2} were fabricated by conventional liquid phase sintering of powder mixtures. For ceramic contents from 70 to 85 vol.%, pressureless melt infiltration was found to be a more suitable processing technique. In FeAl-60 vol.% WC, flexure strengths of up to 1.8 GPa were obtained, even though processing defects consisting of small oxide clusters were present. Room temperature fracture toughnesses were determined by flexure testing of chevron-notched specimens. FeAl/WC and FeAl/TiC composites containing 60 vol.% carbide particles exhibited K{sub Q} values around 20 MPa m{sup 1/2}. Slow crack growth measurements carried out in water and in dry oxygen suggest a relatively small influence of water-vapor embrittlement. It appears therefore that the mechanical properties of iron aluminides in the form of fine ligaments are quite different from their bulk properties. Measurements of the oxidation resistance, dry wear resistance, and thermal expansion of iron aluminide composites suggest many potential applications for these new materials.
Schneibel, J.H.; Subramanian, R.; Alexander, K.B.; Becher, P.F. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
Influence of Cr on the Oxidation of Fe3Al and Ni3Al at 500°C
The influence of chromium on the mechanical properties of the aluminides Fe3Al and Ni3Al has been studied extensively. In order to evaluate the role of Cr during the early stages of oxidation, Fe3Al and Ni3Al containing 2 and 4 at.% Cr were oxidized in dry air at 500°C for 6, 50, and 100 hr. The oxide scale on Fe3Al consists
A. Velon; D.-Q. Yi
Investigation of primary Li-Si/FeS2 cells
NASA Astrophysics Data System (ADS)
The factors that limit the performance of thermally activated Li-Si/FeS2 batteries were defined through the use of electrochemical characterization tests and post-test examinations. For the characterization tests, 82 individual cells were instrumented with multiple voltage sensors and discharged under isothermal and isobaric conditions. The voltage data for the sensors were recorded to determine the ohmic and electrochemical impedances of each cell component at different levels of discharge. The data analysis completed to date has demonstrated that this approach can successfully differentiate the influence of various operating parameters (e.g., temperature, current density), electrode structures (e.g., FeS2 particle size), and additives on cell capacity, specific energy, and power capability. Thirty cells selected from these tests and additional tests at SNL were examined using optical and scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. These analyses documented microstructural and compositional changes in the active materials and electrolyte. In general, the electrochemical impedance of the FeS electrode limited cell performance. Several methods (including use of fine FeS2 particle size, graphite additions, and higher operating temperatures) produced measurable reductions in this impedance and yielded significant improvements in specific energy and power.
Redey, L.; Smaga, J. A.; Battles, J. E.; Guidotti, R.
Electrochemical corrosion behaviour of Mg–Al alloys with thermal spray Al\\/SiCp composite coatings
The corrosion protection of Mg–Al alloys by flame thermal spraying of Al\\/SiC particles (SiCp) composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiCp varied between 5 and 30%. The as-sprayed Al\\/SiCp composite coatings revealed a high number of microchannels, largely in the vicinity of the SiCp, that facilitated the penetration of
A. Pardo; S. Feliu Jr; M. C. Merino; M. Mohedano; P. Casajús; R. Arrabal
Electrochemical corrosion behaviour of Mg–Al alloys with thermal spray Al\\/SiCp composite coatings
The corrosion protection of Mg–Al alloys by flame thermal spraying of Al\\/SiC particles (SiCp) composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiCp varied between 5 and 30%. The as-sprayed Al\\/SiCp composite coatings revealed a high number of microchannels, largely in the vicinity of the SiCp, that facilitated the penetration of
A. Pardo; S. Feliu Jr; M. C. Merino; M. Mohedano; P. Casajús; R. Arrabal
Lower mantle electrical conductivity based on measurements of Al,?Fe-bearing perovskite under lower mantle conditions
NASA Astrophysics Data System (ADS)
Laboratory measurements of the electrical conductivities of minerals provide important constraints on the chemistry and structure of the Earth's interior. We have measured the electrical conductivity of Al, Fe-bearing perovskite (Pv), the most abundant lower mantle phase, using a laser-heated diamond-anvil cell (LHDAC). The sample with composition Mg0.83Fe0.21Al0.06Si0.91O3 (Fe3+/?Fe ratio ? 0.4) was synthesized at 26 GPa and 2073 K using a multianvil press. Sample resistance was measured in situ at high pressure and high temperature up to 82 GPa and 2000 K, respectively. Results show a continuous increase in electrical conductivity with increasing pressure, in contrast to some previous studies of (Mg, Fe)SiO3 perovskite and a pyrolite assemblage where a decrease in conductivity was observed at higher pressure. Our results suggest that (1) incorporation of aluminum in Pv has a strong effect on its electrical conductivity and evolution with pressure; (2) spin crossover of Fe3+ does not occur or its effect on the conductivity is small in Al, Fe-bearing Pv, and (3) the contribution of ferropericlase to the electrical conductivity of pyrolite may be significant. The electrical conductivity profile of the Earth's lower mantle derived from geomagnetic data can be better explained by a pyrolitic bulk chemical composition rather than a non-pyrolitic model such as one based solely on perovskite.
Sinmyo, R.; Pesce, G.; Greenberg, E.; McCammon, C.; Dubrovinsky, L.
Microstructure evolution in TiAl alloyed with Si
Titanium aluminides are among those promising candidates for high-temperature structural use. Development of these alloys requires improved toughness and creep resistance while maintaining their inherently attractive properties. Eutectic alloy consisting of two intermetallic phases is a competitive design to the costly intermetallic-matrix composites in the present research. It has been shown that silicon additions to Ti and Ti{sub 3}Al lead to dual phase alloys containing Ti{sub 5}Si{sub 3} as the second phase. Based on previous work, it might be inferred that silicon additions to TiAl may introduce Ti{sub 5}Si{sub 3} in the matrix. Moreover, by referring to the Ti-Al diagram in the vicinity of the {gamma} field, changes to the liquidus valley in this region of the Ti-Al-Si system are implied. In this paper, investigation was undertaken to extend the understanding of the titanium aluminides which were alloyed with silicon and the Ti-Al-Si system.
Zhang, L.; Wu, J. [Shanghai Jiao Tong Univ. (China). Dept. of Materials Science] [Shanghai Jiao Tong Univ. (China). Dept. of Materials Science
Mechanical properties of Ni{sub 3}Al and FeAl: Recent developments
Recent developments in the understanding of the ductility and fracture behavior of Ni{sub 3}Al and FeAl are reviewed. Both intrinsic factors (e.g., alloy stoichiometry), and extrinsic factors (e.g., environment) have been shown to affect their mechanical properties. Of all the recent developments, perhaps the most significant is the realization that Ni{sub 3}Al and FeAl are intrinsically ductile (at least on the Al-deficient side of stoichiometry); their brittleness when tested in ambient air is due mainly to environmental embrittlement. Another intriguing discovery is that boron embrittles Ni{sub 3}Al in gaseous hydrogen (until recently, B was though to have only beneficial, or at most neutral, effects). The authors review these and other recent discoveries and discuss, wherever possible, the underlying physical mechanisms giving rise to the observed mechanical behavior.
George, E.P.; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
Graphite–FeSi alloy composites as anode materials for rechargeable lithium batteries
Iron–silicon are prepared by annealing elemental mixtures at 1000°C followed by mechanical milling. Graphite–Fe20Si80 alloy composites have been prepared by ball-milling a mixture of Fe20Si80 alloy and graphite powder. The microstructure and electrochemical performance of the composites are characterized by X-ray diffraction and an electrochemical method. The FeSi2 matrix is stable for extended cycles and acts as a buffer for
Heon-Young Lee; Sung-Man Lee
Microindentation of Al-Cu-Fe icosahedral quasicrystal
Many different microindentation experiments have been performed at ambient temperature on icosahedral quasicrystals (QCs). They have shown that icosahedral QCs, such as Al-Cu-Fe, Al-Pd-Mn, Al-Li-Cu, Al-Ru-Cu and Mg-Zn-Y are rather hard and exhibit a low fracture toughness. In other respects, compression experiments have shown that these materials exhibit a brittle-to-ductile transition temperature (BDTT) at about 0.7 T{sub m} where T{sub m} is the melting temperature. Few results have been reported concerning microindentation experiments performed at high temperatures, either in the brittle or in the ductile regime. The hardness behavior of icosahedral QCs as a function of temperature has been presented in two cases, however: Al-Li-Cu and Al-Pd-Mn. This paper is aimed at providing information about microindentation measurements performed on an icosahedral Al-Cu-Fe alloy over an extended temperature range. The results are analyzed within the frame used for previous results obtained in the same alloy by means of compression experiments.
Giacometti, E.; Baluc, N.; Bonneville, J.; Rabier, J.
Mechanical properties of {beta}-SiAlON ceramics joined using composite {beta}-SiAlON-glass adhesives
The mechanical properties of {beta}-SiAlON ceramics joined using {beta}-SiAlON-glass-forming adhesives consisting of mixed Si{sub 3}N{sub 4}, Y{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, and SiO{sub 2} powders are described. Use of adhesives with a {beta}-SiAlON:glass ratio of 60:40 gave an optimum joint strength of 650 MPa in four-point bending mode, i.e., 85% of that of unbonded material, when joining was carried out at 1,600-C for 10 min, under an applied uniaxial pressure of 2 MPa. Bonding pressures in excess of 2 MPa caused excessive compressive creep distortion during the joining operation. The strengths of postjoined HIPed material and HIPed, unbonded material, differed by only 4%, i.e., 975 and 1,010 MPa, respectively, which indicates that HIPing reduces the size of critical defects in the joint. Fracture toughness of the joint also improved upon HIPing.
Walls, P.A.; Ueki, Masanori [Nippon Steel Corp., Kawasaki (Japan). Advanced Technology Research Labs.
Corrosion performance of Fe-Cr-Al and Fe aluminide alloys in complex gas environments
Alumina-forming structural alloys can offer superior resistance to corrosion in the presence of sulfur-containing environments, which are prevalent in coal-fired fossil energy systems. Further, Fe aluminides are being developed for use as structural materials and/or cladding alloys in these systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. In addition, surface coatings of Fe aluminide are being developed to impart corrosion resistance to structural alloys. This paper describes results from an ongoing program that is evaluating the corrosion performance of alumina-forming structural alloys, Fe-Al and Fe aluminide bulk alloys, and Fe aluminide coatings in environments typical of coal-gasification and combustion atmospheres. Experiments were conducted at 650-1000{degrees}C in simulated oxygen/sulfur gas mixtures. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HCl-containing gases. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales and to determine the modes of corrosion degradation that occur in the materials when they are exposed to S/Cl-containing gaseous environments.
Natesan, K. [Argonne National Lab., IL (United States); Johnson, R.N. [Pacific Northwest Lab., Richland, WA (United States)
Comparison of the microstructure and magnetic properties of strontium hexaferrite films deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates by pulsed laser technique
NASA Astrophysics Data System (ADS)
Strontium hexaferrite SrFe12O19 (SrM) films have been deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates. The (001) oriented SrFe12O19 films deposited on the Al2O3(0001) and Si(100)/Pt(111) substrates have been confirmed by X-ray diffraction patterns. Higher coercivity in perpendicular direction rather than in-plane direction of the SrM/Al2O3(0001) and SrM/Pt(111) films showed that the films had perpendicular magnetic anisotropy. The (001) orientation and similar microstructure and magnetic properties of the SrM/Al2O3(0001) and SrM/Pt(111) films show the Al2O3(0001) substrate can be replaced by the Si(100)/Pt(111) substrate.
Masoudpanah, S. M.; Seyyed Ebrahimi, S. A.; Ong, C. K.
Decomposition of SiN interlayer during thermal annealing of HfAlOx/SiN/Si(001) structure
NASA Astrophysics Data System (ADS)
We investigated the effects of postdeposition annealing (PDA) on a 3.1-nm-HfAlOx/0.45-nm-SiN/Si(001) structure under ultrahigh vacuum conditions. PDA caused the SiN interlayer (IL) to decompose, which was followed by N incorporation into the HfAlOx film. A detailed assessment of temperature and time dependencies during the PDA of the structure indicated that the SiN IL decomposed with an activation energy of 0.7 eV, which was much lower than that of bulk ?-phase Si3N4. We suggest that the presence of oxygen-deficient metal oxide sites at the internal dielectric interface of the structure was responsible for catalyzing IL decomposition during PDA.
Kundu, Manisha; Miyata, Noriyuki; Morita, Yukinori; Horikawa, Tsuyoshi; Nabatame, Toshihide; Ichikawa, Masakazu; Toriumi, Akira
Electronic structure and unusual superconducting properties of of CaAlSi and SrAlSi
NASA Astrophysics Data System (ADS)
We report full-potential LAPW calculations for CaAlSi and SrAlSi in ordered structures and in the virtual crystal approximation, at normal and elevated pressures. We also estimate the electron-phonon coupling using either frozen-phon calculations at the zone center, or the rigid muffin tin approximation. We conclude that there is no simple way to explain the recently reported qualitative disparity in the superconducting properties of the two compounds. An assumption of an ultrasoft phonon mode, on the other hand, allows to reconcile in a reasonable way the experimental findings with the theory.
Mazin, Igor I.; Papaconstantopoulos, Dimitris
Mechanical properties of Fe–Ni–Cr–Si–B bulk glassy alloy
The mechanical properties and crystallization behavior of new Fe–Ni–Cr–Si–B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe–Ni–Cr–Si–B, Fe–Ni–Zr–Cr–Si–B, Fe–Ni–Zr–Cr–W–Si–B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin
Kee Ahn Lee; Yong Chan Kim; Jung Han Kim; Chong Soo Lee; Jung Namkung; Moon Chul Kim
Growth and surface morphology of hot-dip Al–Si on 9Cr1Mo steel
The high-temperature oxidation behavior of a commercial cold-rolled 9Cr-1Mo steel sheet that was hot-dipped in Al–7 wt.% Si was studied. The oxidation kinetics showed a two-stage behavior. The oxidation rate was significantly faster during the first hour, followed by a decreased steady-state growth rate at longer times. The hot-dipped steel had a higher oxidation rate than has been reported for FeAl
Yo-Yu Chang; Wei-Jen Cheng; Chaur-Jeng Wang
Scratch behavior of SiAlON ceramics
The mechanical response of four different types of hot pressed yttrium stabilized ?\\/? composite SiAlON ceramics was investigated by scratch testing in order to interpret their severe wear behavior. A progressive loading scratch tester with both rough and smooth spherical diamond styluses was used to analyze the variation in mechanical response with roughness of stylus. The extent of subsurface damage
Ramasamy Sivakumar; Mark I. Jones; Kiyoshi Hirao; Wataru Kanematsu
Laser welding of Al-Si coated hot stamping steel
Advanced high strength steel (AHSS) is being increasingly used in automotive industries for weight reduction purposes. Hot stamping steel, which is a boron alloyed steel, has a strength greater than 1500MPa after hot forming and successive quenching. Because the heating temperature is normally greater than 900°C, a thin Al-Si based coating layer is applied to the steel surface to prevent
C. Kim; M. J. Kang; Y. D. Park
Mullite/SiAlON/alumina composites by infiltration processing
The formation of mullite/SiAlON/alumina composites was studied by infiltrating a SiAlON/alumina-base composite with two different solutions, followed by thermal treatment. The base composite was prepared from a mixture of tabular Al{sub 2}O{sub 3} grains, fume SiO{sub 2}, and aluminum powders. The mixture was pressed into test bars and nitrided in a nitrogen-gas (N{sub 2}) atmosphere at 1,480 C. The infiltrants were prehydrolyzed ethyl polysilicate solution and ethyl polysilicate-aluminum nitrate solution. The composites were infiltrated under vacuum, cured at 100 C, and precalcined in air at 700 C. This infiltration process was repeated several times to produce bars that had been subjected to multiple infiltrations, then the bars were calcined in a N{sub 2} atmosphere at 1,480 C to obtain mullite/SiAlON/alumina composites. The infiltration process increased the percentage of nitrogenous crystalline and mullite phases in the matrix; therefore, a decrease of the composite microporosity was observed. The infiltration increased the mechanical strength of the composites. Of the two composites, the one produced using prehydrolyzed ethyl polysilicate as the infiltrant had a higher mechanical strength, before and after being subjected to a severe thermal shock.
Albano, M.P.; Scian, A.N. [Centro de Tecnologia de Recursos Minerales y Ceramica, Buenos Aires (Argentina)
Influence of acid-base equilibrium in the Na/sub 2/O-CaO-FeO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system on the structure and characteristics of man-made rock
The influence of acid-base equilibrium on the Na/sub 2/O-CaO-FeO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system was investigated in this work. Granulated slag from smelted nickel, copper, and lead was used as the silicate component; and aqueous solutions of Na/sub 2/CO/sub 3/ and Na/sub 2/O x SiO/sub 2/ were used in the alkaline component. The use of this raw material in alkaline slag binders is made possible by the high activity of the alkali metal compounds which interact with nonferrous metal slags to form low based calcium hydrosilicates of the tobermorite group, sodium-calcium zeolites of gmelinite composition, calcite, and hydrated iron-containing neogenics in the solidification products that serve as auxiliary structure forming elements. These conclusions are based on a nuclear gamma resonance (Moessbauer effect) study of the iron ions during the hydration of alkaline slag binders. The study showed that there is an acid-base equilibrium which accelerates the transformation of iron II into iron III oxide, making amphoteric properties possible in this system.
Krivenko, P.V.; Skurchinskaya, Zh. V.; Sulmanov, A.A.; Pol'shin, E.V.
Coprecipitated iron-containing catalysts (FeAl 2O 3, Fe-Co-Al 2O 3, Fe-Ni-Al 2O 3) for methane decomposition at moderate temperatures
Genesis of the composition and structure of the active component of coprecipitated iron containing catalysts (Fe-Al2O3, Fe-Co-Al2O3, Fe-Ni-Al2O3) with high metal loadings (>50wt.%) for methane decomposition at moderate temperatures (600–650°C) has been investigated by XRD, EXAFS, radial electron density distribution (REDD), TEM, FTIR and Mössbauer spectroscopy. The main stages of the catalyst genesis during drying, thermal decomposition and reduction have
T. V. Reshetenko; L. B. Avdeeva; A. A. Khassin; G. N. Kustova; V. A. Ushakov; E. M. Moroz; A. N. Shmakov; V. V. Kriventsov; D. I. Kochubey; Yu. T. Pavlyukhin; A. L. Chuvilin; Z. R. Ismagilov
Novel image analysis to determine the si modification for hypoeutectic and hypereutectic Al-Si alloys
NASA Astrophysics Data System (ADS)
The aim of this research is to develop a novel analytical approach to determine the level of modification of silicon in Al-Si hypoeutectic and hypereutectic alloys. Two standards to determine the level of modification of silicon particles were investigated: the AFS Si Modification Standard and the Primary Si Grade.1,2 The first method can only be used for Al-Si hypoeutectic alloys and the second one for Al-Si hypereutectic alloys. In both methods, the determination of the level of modification of silicon is carried out by comparing micrographs of the test sample with the respective standards by simple observation. This results in a method with a bias error and does not take advantage of the analytical accuracy made possible by modern image analysis techniques. This paper presents a method known as image-analysis-based silicon modification level, which provides highly reliable results to determine the level of silicon modification for Al-Si hypoeutectic and hypereutectic alloys.
Robles Hernández, F. C.; Sokolowski, J. H.
Crystal structure of the NaCa(Fe{sup 2+}, Al, Mn){sub 5}[Si{sub 8}O{sub 19}(OH)](OH){sub 7} {center_dot} 5H{sub 2}O mineral: A new representative of the palygorskite group
A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Angstrom-Sign , b = 17.901(1) Angstrom-Sign , c = 13.727(1) Angstrom-Sign , {alpha} = 90.018(3) Degree-Sign , {beta} = 97.278(4) Degree-Sign , and {gamma} = 89.952(3) Degree-Sign . The structure is solved by the direct methods in space group P1-bar and refined to R = 5.5% for 4168 |F| > 7{sigma}(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na{sub 1.6}K{sub 0.2}Ca{sub 0.2})[Ca{sub 2}(Fe{sub 3.6}{sup 2+}Al{sub 1.6}Mn{sub 0.8})(OH){sub 9}(H{sub 2}O){sub 2}][(Fe{sub 3.9}{sup 2+}Ti{sub 0.1})(OH){sub 5} (H{sub 2}O){sub 2}][Si{sub 16}O{sub 38}(OH){sub 2}] {center_dot} 6H{sub 2}O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.
Rastsvetaeva, R. K., E-mail: firstname.lastname@example.com; Aksenov, S. M.; Verin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
Semiconducting Ge{endash}Si{endash}Fe alloy grown on Si(100) substrate by reactive deposition epitaxy
In this letter, we report a semiconducting Ge{endash}Si{endash}Fe alloy thin film grown on Si(100) by reactive deposition epitaxy using high vacuum evaporation technique. This work is based on the idea that the band structure of {beta}-FeSi{sub 2} will be changed with part of the Si atoms in the lattice replaced by Ge atoms. An iron film was first deposited on a SiGe/Si(100) structure, then the alloy was formed during an annealing process. Auger electron spectroscopy and x-ray diffraction results indicate that the new alloy film can be regarded as a distorted {beta}-FeSi{sub 2} thin film with the participation of Ge. The direct band gap of the Ge{endash}Si{endash}Fe alloy is determined to be 0.83 eV by optical transmission measurements, which indicate a redshift of the band gap with regard to that of {beta}-FeSi{sub 2} ({ital E}{sub {ital g}}=0.87 eV) thin films. {copyright} {ital 1996 American Institute of Physics.}
Chen, H.; Han, P.; Huang, X.D.; Hu, L.Q.; Shi, Y.; Zheng, Y.D. [Department of Physics, Nanjing University, Nanjing 210093, People`s Republic of (China)] [Department of Physics, Nanjing University, Nanjing 210093, People`s Republic of (China)
Refinement of primary Si in hypereutectic Al-Si alloys by intensive melt shearing
NASA Astrophysics Data System (ADS)
Hypereutectic Al-Si based alloys are gaining popularity for applications where a combination of light weight and high wear resistance is required. The high wear resistance arising from the hard primary Si particles comes at the price of extremely poor machine tool life. To minimize machining problems while exploiting outstanding wear resistance, the primary Si particles must be controlled to a uniform small size and uniform spatial distribution. The current industrial means of refining primary Si chemically by the addition of phosphorous suffers from a number of problems. In the present paper an alternative, physical means of refining primary Si by intensive shearing of the melt prior to casting is investigated. Al-15wt%Si alloy has been solidified under varying casting conditions (cooling rate) and the resulting microstructures have been studied using microscopy and quantitative image analysis. Primary Si particles were finer, more compact in shape and more numerous with increasing cooling rate. Intensive melt shearing led to greater refinement and more enhanced nucleation of primary Si than was achieved by adding phosphorous. The mechanism of enhanced nucleation is discussed.
Zhang, Z.; Li, H.-T.; Stone, I. C.; Fan, Z.
Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties
NASA Astrophysics Data System (ADS)
An Al-11Mg2Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg2Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.
Georgatis, E.; Lekatou, A.; Karantzalis, A. E.; Petropoulos, H.; Katsamakis, S.; Poulia, A.
First-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions
NASA Astrophysics Data System (ADS)
We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001) magnetic tunneling junctions (MTJs) on the basis of first-principles calculations of the electronic structures and the ballistic conductance. The calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ (1600%) for the same barrier thickness. However, there was an evanescent state with ?1 symmetry in the energy gap around the Fermi level of normal spinel MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs. The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive channels in the minority spin states resulting from a band-folding effect in the two-dimensional Brillouin zone of the in-plane wave vector (k?) of the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the primitive in-plane cell size of bcc Fe, the bands in the boundary edges are folded, and minority-spin states coupled with the ?1 evanescent state in the MgAl2O4 barrier appear at k?=0, which reduces the TMR ratio of the MTJs significantly.
Miura, Yoshio; Muramoto, Shingo; Abe, Kazutaka; Shirai, Masafumi
Molecular beam epitaxy of ?- FeSi films on Si(111) substrates and its influence on minority-carrier diffusion length of Si measured by EBIC
NASA Astrophysics Data System (ADS)
We have studied the influence of molecular beam epitaxy (MBE) of ?- FeSi films on minority-carrier diffusion length of an n-type Si(111) substrate. It was found from electron beam induced current technique that the diffusion length was less influenced in sample formed with a ?- FeSi template prior to the MBE growth than that in sample grown without the template. The size of ?- FeSi grains measured by electron back-scatter diffraction was also discussed.
Kawakami, H.; Suzuno, M.; Akutsu, K.; Chen, J.; Fuxing, Y.; Sekiguchi, T.; Suemasu, T.
Mössbauer study of Fe in 3C-SiC following 57Mn implantation
NASA Astrophysics Data System (ADS)
Our investigations on substitutional and interstitial Fe in the group IV semiconductors, from 57Fe Mössbauer measurements following 57Mn implantation, have been continued with investigations in 3C-SiC. Mössbauer spectra were collected after implantation and measurement at temperatures from 300 to 905 K. Following comparison with Mössbauer parameters for Fe in Si, diamond and Ge, four Fe species are identified: two due to Fe in tetrahedral interstitial sites surrounded, respectively, by four C atoms (Fei.C) or four Si atoms (Fei,Si) and two to Fe in (or close to) defect free or implantation damaged substitutional sites. An annealing stage at 300 500 K is evident. Above 600 K the Fei,Si fraction decreases markedly, reaching close to zero intensity at 905 K. This is accompanied by a corresponding increase in the Fei,C fraction.
Bharuth-Ram, K.; Gunnlaugsson, H. P.; Mantovan, R.; Naicker, V. V.; Naidoo, D.; Sielemann, R.; Weyer, G.; Aigne, Th.
Effect of AlN layer thickness on structure and magnetic properties of FePt\\/AlN multilayers
FePt (50nm) and [FePt(xnm)\\/AlN(1, 2, 3nm)]10 (x=2, 3nm) films were prepared by RF magnetron sputtering technique, then were annealed at 550°C for