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Apparent soil electrical conductivity measurements in agriculture
Microsoft Academic Search
The field-scale application of apparent soil electrical conductivity (ECa) to agriculture has its origin in the measurement of soil salinity, which is an arid-zone problem associated with irrigated agricultural land and with areas having shallow water tables. Apparent soil electrical conductivity is influenced by a combination of physico-chemical properties including soluble salts, clay content and mineralogy, soil water content, bulk
D. L. Corwin; S. M. Lesch
Relationship of Apparent Soil Electrical Conductivity to Claypan Soil Properties
tantly, subsets of indicators could be related to a specific soilfunction(KarlenandStott,1994;Brejdaetal.,2000). Understanding relationships between sensor-based measurements Indicator measurements used to assess soil quality must and soil properties related to soil quality may help in developing site- beresponsivetomanagementpracticestoobservechanges specific management. The primary objective of this research was to that might either improve or impair the soil (Karlen examine whether sensor-based apparent
W. K. Jung; N. R. Kitchen; K. A. Sudduth; R. J. Kremer; P. P. Motavalli
Roles apparent resistivity amplitude and phase play in an aquifer's electrical-hydraulic conductivity correlation
NASA Astrophysics Data System (ADS)
This paper argues how the spectral characteristics of two borehole apparent resistivity traces further corroborate two statistically significant electrical-hydraulic (eh) conductivity correlations previously reported in Nevada's fractured welded tuffs. Even though the eh conductivity correlation is positive in one borehole and negative in the other, as explained by low pore water electrical conductivity and the absence or presence of alteration minerals, both apparent resistivity amplitude spectra are identically power-law structured. This is interpreted to mean that eh flow is occurring along rock fractures of a common regional fractal dimension. Furthermore, both apparent resistivity phase spectra are strikingly linear, as mandated by the condition of incompressible fluids. Linear phase implies a groundwater flow that is geostatistically nonstationary in the wide sense, a complication normally not considered by hydrogeologists.
Purvance, David T.
World's Oldest Cotton Experiment: Relationships between Soil Chemical and Physical Properties and Apparent Electrical Conductivity
Measuring and mapping apparent soil electrical conductivity (ECa) is a potentially useful tool for delineating soil variability. The �Old Rotation,� the world's oldest continuous cotton (Gossypium hirsutum L.) experiment (ca. 1896), provides a valuable resource for evaluating soil spatial variability. The objectives of this study were to determine the relationship between soil chemical and physical properties and ECa in the
D. W. Reeves; J. N. Shaw; C. C. Mitchell
Mapping within-field soil drainage using remote sensing, DEM and apparent soil electrical conductivity
In this study, we evaluated the capability of different datasets for soil drainage mapping within agricultural fields. The evaluated datasets include apparent soil electrical conductivity (ECa), remotely sensed high-resolution airborne hyperspectral reflectance (HR) and C-band synthetic aperture radar (SAR) backscattering coefficients, and a high precision digital elevation model (DEM) generated from GPS measurements. The study site was located in an
Jiangui Liu; Elizabeth Pattey; Michel C. Nolin; John R. Miller; Oumar Ka
Relating apparent electrical conductivity to soil properties across the north-central USA
Apparent electrical conductivity (ECa) of the soil profile can be used as an indirect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can efficiently and inexpensively develop the spatially dense datasets desirable for describing within-field spatial soil variability in precision agriculture. The objective of this research was to relate ECa data to measured soil
K. A. Sudduth; N. R. Kitchen; W. J. Wiebold; W. D. Batchelor; G. A. Bollero; D. G. Bullock; D. E. Clay; H. L. Palm; F. J. Pierce; R. T. Schuler; K. D. Thelen
Delineating productivity zones on claypan soil fields using apparent soil electrical conductivity
Efficient and cost-effective methods are needed for delineating sub-field productivity zones to improve soil and crop site-specific management. This investigation was conducted to answer the question of whether apparent soil electrical conductivity (ECa) and elevation could be used to delineate productivity zones (SPZ) for claypan soil fields that would agree with productivity zones delineated from yield map data (YPZ). Ten
N. R. Kitchen; K. A. Sudduth; D. B. Myers; S. T. Drummond; S. Y. Hong
Apparent soil electrical conductivity: applications for designing and evaluating field-scale experiments
On-farm field-scale research has become increasingly common with the advent of new technologies. While promoting a realistic systems perspective, field-scale experiments do not lend themselves to the traditional design concepts of replication and blocking. Previously, a farm-scale dryland experiment in northeastern Colorado was conducted to evaluate apparent electrical conductivity (ECa) classification (within-field blocking) as a basis for estimating plot-scale experimental
C. K. Johnson; K. M. Eskridge; D. L. Corwin
Using apparent soil electrical conductivity (EC a ) to characterize vineyard soils of high clay content
The adoption of precision viticulture requires a detailed knowledge of variation in soil chemical, physical and profile properties.\\u000a This study evaluates the usefulness of apparent electrical conductivity (ECa) data within a GIS framework to identify variations in soil chemical and physical properties and moisture content. The work\\u000a was conducted in a vineyard located in the Carneros Region (Napa Valley, California).
Jos� Ramon Rodr�guez-P�rez; Richard E. Plant; Jean-Jacques Lambert; David R. Smart
Investigation and modelling of the influence of soil moisture content and soil temperature on apparent electrical conductivity
Time-lapse shallow ground-based electromagnetic induction (EMI) measurements are often applied to monitor the dynamics of vadose zone soil water content. However, the relationship between the measured apparent electrical conductivity (ECa) and soil water content is not straightforward. First, apparent ECa reflects a depth-weighted value of the ground's electrical conductivity distribution. Linking it directly to a water content value down to a specific depth is therefore not possible. Secondly, the electrical conductivity of the bulk soil depends on the influence of several factors. The major contribution to a change in electrical conductivity is known to be caused by the amount of dissolved ions in the pore fluid, variations in soil water content and soil temperature. In addition, electrical conductivity depends on clay content. There exists no universal petrophysical relationship that relates the sum of all these parameters to electrical conductivity. The separation of the different influences remains challenging since EMI devices are applied in a non-destructive manner and profile information about soil textural properties, soil water content, soil temperature and the soil electrical conductivity is usually not accessible. We use a time series of TDR-measured soil water contents and soil electrical conductivities together with soil temperature data measured at various depths of a soil profile at the Grenzhof test site to investigate the influence of soil water content and temperature on the soil's electrical conductivity. Subsequently, we apply forward modelling of electrical conductivity to estimate the response of the EMI device on temperature-corrected and uncorrected electrical conductivity profiles. Preliminary results show, that the influence of a change in soil water content on apparent electrical conductivity conducts only few mS/m and is often influenced by simultaneous occurring changes in soil temperature.
Denk, Astrid; Dietrich, Peter; van der Kruk, Jan; Roth, Kurt; Wollschl�ger, Ute
Spatial and Temporal Patterns of Apparent Electrical Conductivity: DUALEM vs. Veris Sensors for Monitoring Soil Properties
PubMed Central
The main objective of this study was to compare two apparent soil electrical conductivity (ECa) sensors (Veris 2000 XA and DUALEM 1S) for mapping variability of soil properties in a Mediterranean shallow soil. This study also aims at studying the effect of soil cover vegetation on the ECa measurement by the two types of sensors. The study was based on two surveys carried out under two very different situations: in February of 2012, with low soil moisture content (SMC) and with high and differentiated vegetation development (non grazed pasture), and in February of 2013, with high SMC and with short and relatively homogeneous vegetation development (grazed pasture). The greater temporal stability of Veris sensor, despite the wide variation in the SMC and vegetation ground cover indicates the suitability of using this sensor for monitoring soil properties in permanent pastures. The survey carried out with the DUALEM sensor in 2012 might have been affected by the presence of a 0.20 m vegetation layer at the soil surface, masking the soil properties. These differences should be considered in the selection of ECa sensing systems for a particular application.
Serrano, Joao; Shahidian, Shakib; da Silva, Jose Marques
Spatial and temporal patterns of apparent electrical conductivity: DUALEM vs. Veris sensors for monitoring soil properties.
The main objective of this study was to compare two apparent soil electrical conductivity (ECa) sensors (Veris 2000 XA and DUALEM 1S) for mapping variability of soil properties in a Mediterranean shallow soil. This study also aims at studying the effect of soil cover vegetation on the ECa measurement by the two types of sensors. The study was based on two surveys carried out under two very different situations: in February of 2012, with low soil moisture content (SMC) and with high and differentiated vegetation development (non grazed pasture), and in February of 2013, with high SMC and with short and relatively homogeneous vegetation development (grazed pasture). The greater temporal stability of Veris sensor, despite the wide variation in the SMC and vegetation ground cover indicates the suitability of using this sensor for monitoring soil properties in permanent pastures. The survey carried out with the DUALEM sensor in 2012 might have been affected by the presence of a 0.20 m vegetation layer at the soil surface, masking the soil properties. These differences should be considered in the selection of ECa sensing systems for a particular application. PMID:24915182
Serrano, Jo�o; Shahidian, Shakib; Silva, Jos� Marques da
Soil Microbial Biomass Relationships with Organic Matter Fractions in a Nebraska Corn Field Mapped using Apparent Electrical Conductivity
Soils exhibit spatial variability in their properties. One approach for delineating field-scale variability involves mapping the variation in apparent soil electrical conductivity (ECa). The objectives of this study were to evaluate the physical and chemical soil characteristics that define ECa classification and the association of specific soil mi- crobiological communities with these soil properties. In May 2003, ECa was measured
Mar�a S. Grigera; Rhae A. Drijber; Kent M. Eskridge; Brian J. Wienhold
Soil Apparent Electrical Conductivity (EC a ) as a Means of Monitoring Changesin Soil Inorganic N on Heterogeneous Morainic Soils in SE Norway During Two Growing Seasons
An efficient method to monitor changes in soil inorganic N content during crop growth would be a useful means to guide N fertilization to ensure high yields and low N losses to the environment. In this study, soil apparent electrical conductivity (ECa) measured by the widely used conductivity meter EM38 was tested as an indirect measurement of available N in
Audun Korsaeth
Electrical Conductivity.
ERIC Educational Resources Information Center
Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)
Allen, Philip B.
Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)
Hershey, David R.; Sand, Susan
Apparent Thermal Conductivity Of Multilayer Insulation
NASA Technical Reports Server (NTRS)
Mathematical model of apparent or effective thermal conductivity between two successive layers of multilayer thermal insulation (MLI) offers potential for optimizing performance of insulation. One gains understanding of how each physical mechanism contributes to overall flow of heat through MLI blanket. Model helps analyze engineering tradeoffs among such parameters as number of layers, thicknesses of gaps between layers, types of spacers placed in gaps, weight, overall thickness, and effects of foregoing on apparent thermal conductivity through blanket.
Mcintosh, Glen E.
The Apparent Thermal Conductivity of Pozzolana Concrete
The recent development of some lightweight construction materials, such as light concrete, can play an important role as an insulator, while maintaining sufficient levels of mechanical performance. The quality of insulation to provide depends on the climate, the exposure of the walls and also the materials used in the construction. The choice of a material to be used as an insulator, obviously, depends on its availability and its cost. This is a study of natural pozzolanas as basic components in building materials. It is intended to highlight their thermal advantage. It is economically advantageous to use pozzolana in substitution for a portion of the clinker as hydraulically active additions, as well as in compositions of lightweight concretes in the form of pozzolanic aggregate mixtures, which provide mechanical strengths that comply with current standards. A theoretical study is conducted on the apparent thermal conductivity of building materials, namely concrete containing pozzolana. Thermal modeling, apparent to that commonly used for porous materials, has been applied to pozzolana concrete. Experimental results on measurements of the apparent thermal conductivity of pozzolana concrete are reported in this study, using an approach that considers that concrete is composed of two solid ingredients, a binding matrix (hydrated cement paste) and all aggregates. A second comparative theoretical approach is used for the case where concrete consists of a solid phase and a fluid phase (air).
Bessenouci, M. Z.; Triki, N. E. Bibi; Khelladi, S.; Draoui, B.; Abene, A.
Electrical Conductivity Protocol
NSDL National Science Digital Library
The purpose of this resource is to measure the conductivity of water at a freshwater hydrology site. Students calibrate and take electrical conductivity measurements using an electrical conductivity meter. Students estimate the total dissolved solids from the electrical conductivity measurements.
The GLOBE Program, UCAR (University Corporation for Atmospheric Research)
An Apparent Anomaly in Peanut Leaf Conductance
Conductance to gaseous transfer is normally considered to be greater from the abaxial than from the adaxial side of a leaf. Measurements of the conductance to water vapor of peanut leaves (Arachis hypogaea L.) under well watered and stress conditions in a controlled environment, however, indicated a 2-fold higher conductance from the adaxial side of the leaf than from the abaxial. Studies of conductance as light level was varied showed an increase in conductance from either surface with increasing light level, but conductance was always greater from the adaxial surface at any given light level. In contrast, measurements of soybean (Glycine max [L.] Merr.) and snapbean (Phaseolus vulgaris L.) leaf conductance showed an approximate 2-fold greater conductance from the abaxial surface than from the adaxial. Approximately the same number of stomata were present on both peanut leaf surfaces and stomatal size was similar. Electron microscopic examination of peanut leaves did not reveal any major structural differences between stomata on the two surfaces that would account for the differences in conductance. Light microscope studies of leaf sections revealed an extensive network of bundle sheaths with achloraplastic bundle sheath extensions; the lower epidermis was lined with a single layer of large achloraplastic parenchyma cells. Measurements of net photosynthesis made on upper and lower leaf surfaces collectively and individually indicated that two-thirds of the peanut leaf's total net photosynthesis can be attributed to diffusion of CO2 through the adaxial leaf surface. Possibly the high photosynthetic efficiency of peanut cultivars as compared with certain other C3 species is associated with the greater conductance of CO2 through their upper leaf surfaces. Images
Pallas, James E.
Electrically conductive diamond electrodes
An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.
Swain, Greg (East Lansing, MI) [East Lansing, MI; Fischer, Anne (Arlington, VA), [Arlington, VA; Bennett, Jason (Lansing, MI) [Lansing, MI; Lowe, Michael (Holt, MI) [Holt, MI
Polymers that Conduct Electricity.
Although polymers are regarded as electrical insulators, it was discovered that they can be made to conduct electricity. This discovery has opened vast new practical and theoretical areas for exploration by physicists and chemists. Research studies with these conducting polymers and charge-transfer salts as well as possible applications are�
Edelson, Edward
Relationship between apparent soil electrical conductivity (ECa) and soil attributes at an experimental parcel under pasture in a region of Galicia, Spain
Spatial characterization of the variability of soil properties is a central point in site-specific agricultural management and precision agriculture. Geospatial measures of geophysical attributes are useful not only to rapidly characterize the spatial variability of soil properties but also for soil sampling optimization. This work reports partial results obtained at an experimental parcel under pasture located at Castro de Ribeira do Lea (Lugo/ Galicia/ Spain). An ECa automated survey was conducted in September 2011 employing an EM-38 DD (Geonics Ltd.) installed in a nonmetallic car, according to parallel lines spaced 10m one from each other and oriented at the east-west direction. The ECa values were recorded every second with a field computer and the locations were geo-referenced using a GPS. The entire survey was carried out in 1hour and 45 minutes and corrections due to differences in temperature were made. A total of 9.581 ECa registers were retained, configuring a sampling intensity of approximately 1 register per 1.5 m2. Employing the software ESAP 2.35 and the computational tool ESAP-RSSD, eighty positions were selected at the field to extract disturbed and undisturbed soil samples at two depths: 0.0-0.2m, 0.2-0.4m. Ten physical attributes (clay, silt, total sand, coarse sand and fine sand contents, soil bulk density, particle density, total porosity, soil water content, percentage of gravels) and 17 chemical attributes (soil organic matter-SOM, pH, P, K, Ca, Mg, Al, H+Al, Sum of bases-S, Cation exchange capacity-CEC, Base saturation-V%, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined. The relationship between the geophysical variables and the soil attributes was performed using statistical and spatial analysis. There were significant correlations (p<0.01) between the geophysical variables and the textural attributes clay, silt, total sand and coarse sand contents. The biggest correlation (0.5623) was between ECa-V (vertical component) and clay content. Also, significant correlations (p<0.05) were found between the ECa-V and soil bulk density, total porosity, percentage of gravels and soil water content. Considering the chemical attributes, significant correlations (p< 0.01) were found between ECa-V and SOM and Cd, and between ECa-H (horizontal component) and SOM and Fe. Other significant correlations (p<0.05) were found between ECa-V and 6 soil chemical attributes: P, Ca, S, Fe, Ni and Pb. The biggest correlation was between ECa-V and SOM (-0.5942). In resume, clay content, SOM, Cd and Fe are the soil attributes better correlated with the observed variation of the ECa at the field. Additional analysis should be performed to compare the spatial patterns of these soil attributes and the ECa as a tool to proper define management zones in the area.
Marinho, M. D.; Paz-Gonzalez, A.; Dafonte, J. D.; Armesto, M. V.; Raposo, J. R.
Electrically conductive composite material
An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.
Clough, R.L.; Sylwester, A.P.
An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.
Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)
Electrical Conduction Activity
This resource provides an introductory activity on electrical conduction. As the module states, "electrical conduction, the movement of electrical charges, is a mechanism for passing energy and signals from one place to another." The activity covers concepts such as insulators, conductors, semiconductors, superconductors, and ballistic conduction at nanoscale. This module allows students to test their knowledge as they go.The other educational modules in this series can be found here. Instructors and students are encouraged to sign up with the Electron Technologies site here before starting to use these materials.
Electrically conductive material
An electrically conductive material is described for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO[sub 2] as a matrix and 6-19 wt. % monoclinic ZrO[sub 2] formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO[sub 2] as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns. 8 figures.
Singh, J.P.; Bosak, A.L.; McPheeters, C.C.; Dees, D.W.
An electrically conductive material for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO.sub.2 as a matrix and 6-19 wt. % monoclinic ZrO.sub.2 formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO.sub.2 as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns.
Singh, Jitendra P. (Bollingbrook, IL); Bosak, Andrea L. (Burnam, IL); McPheeters, Charles C. (Woodridge, IL); Dees, Dennis W. (Woodridge, IL)
Electrical Conductivity of Olivine
The electrical conductivity a of single crystals of olivine of 0, 7.7, 8.2, 9.4, and 26.4 mole % fayalite has been measured up to 1200�C and 7.5 kb. Samples from different localities with approximately the same fayalite content and impurity levels have electrical conductivities that differ by 2-3 orders of magnitude. It is proposed that the oxidation state of the
Al Duba
Electrical Conductivity in Textiles.
National Technical Information Service (NTIS)
Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NAS...
Electrical Conduction in Ice.
In an attempt to resolve the conflict existing in the literature as to dc electrical conductivity of ice, an extensive series of measurements has been made. Since surface conduction is a possible cause of some of the confusion, both bulk and surface condu...
P. R. Camp W. Kiszenick D. A. Arnold
Electrical Conductivity in Textiles
Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.
Electrical Conduction Assessment
This brief assessment on Electrical Conduction is intended to be used after students have completed the introductory activity on the topic, which may be located here. The assessment consists of 8 multiple choice and short answer questions. The other educational modules in this series can be found here. Instructors and students are encouraged to sign up with the Electron Technologies site here before starting to use these materials.
Numerical method for calculating the apparent eddy current conductivity loss on randomly rough surfaces
Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electrical conductivity. This technique is used to nondestructively characterize the subsurface residual stress and cold work distributions in shot-peened metal components. Unfortunately, the spurious surface roughness produced by the shot peening process causes an apparent loss of eddy current conductivity, thereby
Feng Yu; Peter B. Nagy
A scale of apparent intensity of electric shock
By the method of magnitude estimation, Ss having no previous experience in judging electric shock made numerical estimations of the apparent intensity of an electric current applied through salt-water electrodes to the fingers of one hand. To a first approximation, these magnitude estimations determine a power function in which subjective intensity S is related to current I by S =
S. S. Stevens; A. S. Carton; G. M. Shickman
Electrical conductivity of mantle minerals
Electrical conductivity of mantle minerals Deep electrical conductivity profiles can provide constraints on the thermal and chemical state of the mantle. Especially, electrical conductivity is very sensitive to small amount of hydrogen and iron contents in minerals. Accurate knowledge of electrical conductivity of mantle minerals is needed to constrain water and\\/or iron contents in the mantle as a function of
T. Yoshino; G. Manthilake; M. Nishi; T. Katsura
Electrical conduction in olivine
SciTech Connect
This paper reports detailed measurements of electrical conductivitysigma and thermoelectric effect /ital S/ in the mineral olivine and in syntheticforsterite as functions of temperature in the range from 1000/degree/ to1500 /degree/C and oxygen partial pressure in the range from 10/sup /minus/10/ to10/sup 4/ Pa. The two most striking observations are strong conductivityanisotropy in forsterite and a sign change in /ital S/ in olivine at 1390 /degree/C.These results are interpreted to show that both materials have mixed ionic andextrinsic electronic conduction under these conditions. On the basis ofthese interpretations, we infer that forsterite conductivity is dominatedby electronic conduction in the /ital a/ and /ital b/ directions and probably bymovement involving magnesium vacancies in the /ital c/ direction, wherefar higher /ital P//sub O/sub 2//-independent conductivity is observed. Olivineappears to show mixed conduction under all the circumstances observed; at low temperature, electron holes dominate but are superseded bymagnesium vacancies at high temperatures./copyright/ American Geophysical Union 1989
Schock, R. N.; Duba, A. G.; Shankland, T. J.
Ion mobility imaging and contrast mechanism of apparent conductivity in MREIT.
Magnetic resonance electrical impedance tomography (MREIT) aims to produce high-resolution cross-sectional images of conductivity distribution inside the human body. Injected current into an imaging object induces a distribution of internal magnetic flux density, which is measured by using an MRI scanner. We can reconstruct a conductivity image based on its relation with the measured magnetic flux density. In this paper, we explain the contrast mechanism in MREIT by performing and analyzing a series of numerical simulations and imaging experiments. We built a stable conductivity phantom including a hollow insulating cylinder with holes. Filling both inside and outside the hollow cylinder with the same saline, we controlled ion mobilities to create a conductivity contrast without being affected by the ion diffusion process. From numerical simulations and imaging experiments, we found that slopes of induced magnetic flux densities change with hole diameters and therefore conductivity contrasts. Associating the hole diameter with apparent conductivity of the region inside the hollow cylinder with holes, we could experimentally validate the contrast mechanism in MREIT. Interpreting reconstructed apparent conductivity images of the phantom as ion mobility images, we discuss the meaning of the apparent conductivity seen by a certain probing method. In designing MREIT imaging experiments, the ion mobility imaging method using the proposed stable conductivity phantom will enable us to estimate a distinguishable conductivity contrast for a given set of imaging parameters. PMID:21411866
Oh, Tong In; Kim, Young Tae; Minhas, Atul; Seo, Jin Keun; Kwon, Oh In; Woo, Eung Je
Electrically conductive alternating copolymers
Polymers which are soluble in common organic solvents and are electrically conductive, but which also may be synthesized in such a manner that they become nonconductive. Negative ions from the electrolyte used in the electrochemical synthesis of a polymer are incorporated into the polymer during the synthesis and serve as a dopant. A further electrochemical step may be utilized to cause the polymer to be conductive. The monomer repeat unit is comprised of two rings, a pyrrole molecule joined to a thienyl group, or a furyl group, or a phenyl group. The individual groups of the polymers are arranged in an alternating manner. For example, the backbone arrangement of poly(furylpyrrole) is -furan-pyrrole-furan-pyrrole- furan-pyrrole. An alkyl group or phenyl group may be substituted for either or both of the hydrogen atoms of the pyrrole ring.
Aldissi, M.; Jorgensen, B.S.
Model-based imaging of cardiac apparent conductivity and local conduction velocity for diagnosis and planning of therapy.
We present an adaptive algorithm which uses a fast electrophysiological (EP) model to estimate apparent electrical conductivity and local conduction velocity from noncontact mapping of the endocardial surface potential. Development of such functional imaging revealing hidden parameters of the heart can be instrumental for improved diagnosis and planning of therapy for cardiac arrhythmia and heart failure, for example during procedures such as radio-frequency ablation and cardiac resynchronisation therapy. The proposed model is validated on synthetic data and applied to clinical data derived using hybrid X-ray/magnetic resonance imaging. We demonstrate a qualitative match between the estimated conductivity parameter and pathology locations in the human left ventricle. We also present a proof of concept for an electrophysiological model which utilizes the estimated apparent conductivity parameter to simulate the effect of pacing different ventricular sites. This approach opens up possibilities to directly integrate modelling in the cardiac EP laboratory. PMID:18955178
Chinchapatnam, Phani; Rhode, Kawal S; Ginks, Matthew; Rinaldi, C Aldo; Lambiase, Pier; Razavi, Reza; Arridge, Simon; Sermesant, Maxime
Moldable Electrically Conductive Polymer Compositions.
Accordingly, it is an object of this invention to obtain high electrical conductivity in a polymeric composition. Another object is to provide a bulky, moldable polymeric composition that conducts electricity. Another object is to provide a polymeric comp...
O. K. Kim
Electrically Conductive Polymer Concrete Overlays.
The development of a built-up, electrically conductive polymer concrete overlay and a premixed, electrically conductive polymer concrete mortar for use on bridge decks and other concrete members, in conjunction with cathodic protection systems, is reporte...
R. P. Webster J. J. Fontana W. Reams
Electrically Conductive Polymer Concrete Coatings.
A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability....
J. J. Fontana D. Elling W. Reams
Electrically Conductive Polymer Compositions.
A conductive polymer composite system is made by dissolving an electron donating polymer and a simple or complex N-methylphenazinium TCNQ salt in a mutual solvent and casting a film of the resulting solution on a suitable substrate.
Electrically conductive anodized aluminum coatings
A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.
Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)
Electrically Conductive Anodized Aluminum Surfaces
Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In comparison with these competing finishes, the present nanocomposite finishes are expected to cost 50 to 20 percent less and to last longer.
Nguyen, Trung Hung
The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic prot...
J. J. Fontana R. P. Webster
The corrosion of reinforcing steel embedded in concrete causes cracks and delamination in the concrete. The application of impressed current cathodic protection utilizing electrically conductive polymer concrete to distribute the current across concrete b...
J. J. Fontana
Electrical conductivity of mantle minerals Deep electrical conductivity profiles can provide constraints on the thermal and chemical state of the mantle. Especially, electrical conductivity is very sensitive to small amount of hydrogen and iron contents in minerals. Accurate knowledge of electrical conductivity of mantle minerals is needed to constrain water and/or iron contents in the mantle as a function of depth. We have investigated the electrical properties of olivine, wadsleyite, ringwoodite and majorite, which are main constituent minerals of the upper mantle by in situ electrical conductivity measurement using multianvil apparatus. The starting materials were olivine (Fo91) for olivine, wadsleyite and ringwoodite, and glass powder with composition of pyrolite minus olivine for majorite, respectively. In most cases, molybdenum disk electrode connecting to the sample was used as an oxygen buffer media, whose oxygen fugacity is close to Fe-FeO buffer. The electrical conductivities of the samples were measured at various pressures from 3 and 20 GPa and temperatures up to 2000K at low frequencies ranging from 0.01 to 0.1 Hz. For all the dry samples, electrical conductivity displays Arrhenian behavior over the entire investigated temperature range. In the high temperature range above 1700K, activation energies (more than 1.5 eV) tend to be higher than those in the lower temperature range (less than 1.5 eV). The absolute values of electrical conductivity (S/m) for each mineral are very similar to each other. From these measurements we noted that the electrical conductivities of dry olivine, wadsleyite and ringwoodite (less than 100 wt. ppm of water) are much lower than those previously reported (e.g., Xu et al., 1998). While conductivities of samples with certain amounts of hydrogen are comparable to that of the dry one, conductivity increases with increasing hydrogen concentrations. Activation energies of hydrogen-bearing nominally anhydrous minerals we measured decreases with increasing hydrogen concentration from nearly 1 to 0.5 eV. Using our results, we can estimate the electrical conductivity profile of the upper mantle. Comparing the reference model of Utada et al. (2003), our modeling demonstrates that the electrical conductivity of the upper mantle up to 410km discontinuity (i.e. olivine stability field) is close to that of dry olivine, whereas the electrical conductivities of dry wadsleyite, ringwoodite and majorite are much lower than the reference model. Therefore, a presence of hydrogen in their minerals or the other conductors is required to explain the high conductivity in the transition zone. References Xu, Y., Poe, B. T., Shankland, T. J. & Rubie, D. C., Electrical conductivity of olivine, wadsleyite and ringwoodite under upper-mantle conditions. Science 280, 1415-1418 (1998). Utada, H., Koyama, T., Shimizu, H. & Chave, A. D., A semi-global reference model for electrical conductivity in the mid-mantle beneath the north Pacific region. Geophys. Res. Lett. 30, 1194, doi:10.1029/2002GL016902 (2003).
Yoshino, T.; Manthilake, G.; Nishi, M.; Katsura, T.
Electrical conduction in polymer dielectrics
The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.
Cotts, D. B.
Electrical conductivity of carbonaceous powders
The present paper deals with the electrical conductivity of a number of carbonaceous powders undergoing a low compaction. It is shown that the contributions to the conductivity of such samples are too numerous and too complex to be solved exactly. Hence, several criteria are proposed in order to quantify the behaviour of moderately compressed powders, and thus derive several useful
A. Celzard; J. F. Mar�ch�; F. Payot; G. Furdin
Electrical Conductivity of Cryolite Melts
This paper proposes an equation for the electrical conductivity of multicomponent cryolite-based mixtures. The equation is based on a physical model which assumes that the conductivity is proportional to the number density of the effective electric charges in the melt. The various authors in the available literature show a great discrepancy in conductivity data of cryolite-based melts. The equation based on the physical model enables determination of which set of data is preferable. Special consideration in this respect is given to the influence of magnesium flouride and lithium flouride additions to the melt.
Fellner, P.; Grjotheim, K.; Kvande, H.
Electrical conductivity of chondritic meteorites
The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C.
Duba, AL; Didwall, E. M.; Burke, G. J.; Sonett, C. P.
Electrically conductive polymer concrete coatings
A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt% calcined coke breeze, 40 wt% vinyl ester resin with 3.5 wt% modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag. 4 tabs.
Fontana, J.J.; Elling, D.; Reams, W.
A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.
Fontana, Jack J. (Shirley, NY); Elling, David (Centereach, NY); Reams, Walter (Shirley, NY)
Using Soil Electrical Conductivity to Improve Nutrient Management
ECa could be used to measure the available nutrient content of the soil, eliminating the need for time-consum- While site-specific nutrient management has the potential for im- ing and expensive soil sample acquisition and analysis. proving crop yields, the cost of intensive soil sampling is usually greater Apparent soil electrical conductivity consists of two than the benefits gained. Apparent soil
Ronnie W. Heiniger; Robert G. McBride; David E. Clay
Electrically conductive polymer concrete overlays
The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic protection for the highway industry. Laboratory studies indicate that electrically conductive polymer concrete overlays using conductive fillers, such as calcined coke breeze, in conjunction with polyester or vinyl ester resins have resistivities of 1 to 10 ohm-cm. Both multiple-layer and premixed mortar-type overlays were made. Shear bond strengths of the conductive overlays to concrete substrates vary from 600 to 1300 psi, with the premixed overlays having bond strengths 50 to 100% higher than the multiple-layer overlays.
Fontana, J. J.; Webster, R. P.
The electrical conductivity of lherzolite
Electrical conductivity as a function of oxygen fugacity (f{sub O2}) between 10{sup {minus}5} Pa and 1 Pa, temperature between 700{degrees}C and 1200{degrees}C, and time over a period of 1700 hours are reported for a lherzolite nodule from Mount Porndon, Australia. Analysis of complex impedance collected at 100 Hz, 1 kHz, and 10 kHz indicates that there is significant frequency dispersion in this rock at temperatures below 900{degrees}C-1000{degrees}C. By choosing the resistance of an equivalent parallel RC network at the frequency having minimum phase, the effect of dispersion is largely avoided. Conductivity as a function of time, collected following changes in f{sub O2} at 1010 and 1200{degrees}C, has been analyzed to determine the diffusivity of defects relating f{sub O2} to the electrical conduction mechanism in olivine. The diffusivities so obtained are in remarkably good agreement with those determined from strain measurements during creep tests, which implies that magnetism vacancies are the rate-limiting step for conductivity reequilibration after f{sub O2} changes. A longer-term process is observed in this rock in which the conductivity drifts upward or downward with a time constant of hundreds of hours after initial reequilibration to gas mix (f{sub O2}) changes. The authors speculate that this long-term drift could be related to equilibration of the iron distribution between coexisting olivine and pyroxene as a function of f{sub O2}. The lherzolite conductivity data are not significantly different from measurements made on olivine single crystals and polycrystals, even though the rock contains about 34 model % pyroxene. This consistency of laboratory measurements of electrical conductivity of olivines from many localities and geological settings supports the use of recent models relating mantle temperature with electrical conductivity in the interpretation of mantle geo/electromagnetic soundings. 33 refs., 11 figs., 3 tabs.
Duba, A. [Lawrence Livermore National Lab., CA (United States); Constable, S. [Scripps Institution of Oceanography, La Jolla, CA (United States)
Electrical Conductivity in Transition Metals
The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence�
Talbot, Christopher; Vickneson, Kishanda
Electrically conductive rigid polyurethane foam
A rigid, moldable polyurethane foam comprises about 2 to 10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.
Neet, T.E.; Spieker, D.A.
A rigid, polyurethane foam comprises about 2-10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.
Th. E. Neet; D. A. Spieker
T. E. Neet; D. A. Spieker
Electric conductivity of plasma in solar wind
One of the most important parameters in MHD description of the solar wind is the electric conductivity of plasma. There exist now two quite different approaches to the evaluation of this parameter. In the first one a value of conductivity taken from the most elaborated current theory of plasma should be used in calculations. The second one deals with the empirical, phenomenological value of conductivity. E.g.: configuration of interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of electrical conductivity of plasma in the solar wind. Knowing the main empirical features of the field configuration, one may estimate the apparent phenomenological value of resistance. The estimations show that the electrical conductivity should be approximately 10(exp 13) times smaller than that calculated by Spitzer. It must be noted that the empirical value should be treated with caution. Due to the method of its obtaining it may be used only for 'large-scale' description of slow processes like coronal expansion. It cannot be valid for 'quick' processes, changing the state of plasma, like collisions with obstacles, e.g., planets and vehicles. The second approach is well known in large-scale planetary hydrodynamics, stemming from the ideas of phenomenological thermodynamics. It could formulate real problems which should be solved by modern plasma physics, oriented to be adequate for complicated processes in space.
Chertkov, A. D.
Electrically conductive black optical paint
An electrically conductive flat black paint has been developed for use on the Galileo spacecraft which will orbit Jupiter in the late 1980s. The paint, designed for equipment operating in high-energy radiation fields, has multipurpose functions. Its electrical conductivity keeps differential charging of the spacecraft external surfaces and equipment to a minimum, preventing the buildup of electrostatic fields and arcing. Its flat black aspect minimizes the effects of stray light and unwanted reflectances, when used in optical instruments and on sunshades. Its blackness is suitable, also, for thermal control, when the paint is put on spacecraft surfaces. The paint has good adherence properties, as measured by tape tests, when applied properly to a surface. The electrically conductive paint which was developed has the following characteristics: an electrical resistivity of 5 x 10 to the 7th ohms per square; a visual light total reflectance of approximately 5 percent; an infrared reflectance of 0.13 measured over a spectrum from 10 to the (-5.5) power to 0.001 meter; a solar absorptivity, alpha-s, of 0.93, and a thermal emissivity, epsilon, of 0.87, resulting in an alpha-s/epsilon of 1.07. The formula for making the paint and the process for applying it are described.
Birnbaum, M. M.; Metzler, E. C.; Cleland, E. L.
Electrical conductivity of ice VII
It was discovered that a peak appears near a pressure of Pc = 10?GPa in the electrical conductivity of ice VII as measured through impedance spectroscopy in a diamond anvil cell (DAC) during the process of compression from 2?GPa to 40?GPa at room temperature. The activation energy for the conductivity measured in the cooling/heating process between 278?K and 303?K reached a minimum near Pc. Theoretical modelling and molecular dynamics simulations suggest that the origin of this unique peak is the transition of the major charge carriers from the rotational defects to the ionic defects.
Okada, Taku; Iitaka, Toshiaki; Yagi, Takehiko; Aoki, Katsutoshi
Electrical conductivity of ice VII.
It was discovered that a peak appears near a pressure of Pc = 10?GPa in the electrical conductivity of ice VII as measured through impedance spectroscopy in a diamond anvil cell (DAC) during the process of compression from 2?GPa to 40?GPa at room temperature. The activation energy for the conductivity measured in the cooling/heating process between 278?K and 303?K reached a minimum near Pc. Theoretical modelling and molecular dynamics simulations suggest that the origin of this unique peak is the transition of the major charge carriers from the rotational defects to the ionic defects. PMID:25047728
Electrically conductive thermal control coatings
A coating characterized by low thermal absorption, high thermal emittance and high electrical conductivity comprises: (1) a fired oxide pigment comprising a minor amount of aluminum oxide and a major amount of zinc oxide; (2) sufficient water to provide a mixture suitable for application to a substrate, is presented. The fired oxide pigment may further include a minor amount of cobalt oxide. The resulting coating is particularly useful for coating the surfaces of spacecraft and similar objects.
Shai, M. C. (inventor)
Anisotropic wave propagation and apparent conductivity estimation in a fast electrophysiological model: application to XMR interventional imaging.
Cardiac arrhythmias are increasingly being treated using ablation procedures. Development of fast electrophysiological models and estimation of parameters related to conduction pathologies can aid in the investigation of better treatment strategies during Radio-frequency ablations. We present a fast electrophysiological model incorporating anisotropy of the cardiac tissue. A global-local estimation procedure is also outlined to estimate a hidden parameter (apparent electrical conductivity) present in the model. The proposed model is tested on synthetic and real data derived using XMR imaging. We demonstrate a qualitative match between the estimated conductivity parameter and possible pathology locations. This approach opens up possibilities to directly integrate modelling in the intervention room. PMID:18051105
Chinchapatnam, P P; Rhode, K S; King, A; Gao, G; Ma, Y; Schaeffter, T; Hawkes, D; Razavi, R S; Hill, D L G; Arridge, S; Sermesant, M
Anisotropic Wave Propagation and Apparent Conductivity Estimation in a Fast Electrophysiological Model: Application to XMR Interventional Imaging
Cardiac arrhythmias are increasingly being treated using ablation procedures. Development of fast electrophysiological models\\u000a and estimation of parameters related to conduction pathologies can aid in the investigation of better treatment strategies\\u000a during Radio-frequency ablations. We present a fast electrophysiological model incorporating anisotropy of the cardiac tissue.\\u000a A global-local estimation procedure is also outlined to estimate a hidden parameter (apparent electrical
Phani Chinchapatnam; Kawal S. Rhode; Andrew P. King; G. Gao; Y. Ma; T. Schaeffter; David J. Hawkes; Reza Razavi; Derek L. G. Hill; Simon R. Arridge; Maxime Sermesant
Electrical conductivity and corrosion protection properties of conductive paint coatings
Purpose � The purpose of this paper is to investigate the electrical conductivity and corrosion protection properties of a conductive coating composed of epoxy resin and carbon black in a sodium chloride (NaCl) solution. Design\\/methodology\\/approach � The conductive coating was prepared by combining epoxy resin, hardener, and carbon black. The electrical conductivity of the paint was studied with a DC
M. N. Masri; Z. M. Yunus; A. R. M. Warikh; A. A. Mohamad
Gas Phase Pressure Effects on the Apparent Thermal Conductivity of JSC-1A Lunar Regolith Simulant
Gas phase pressure effects on the apparent thermal conductivity of a JSC-1A/air mixture have been experimentally investigated under steady state thermal conditions from 10 kPa to 100 kPa. The result showed that apparent thermal conductivity of the JSC-1A/air mixture decreased when pressure was lowered to 80 kPa. At 10 kPa, the conductivity decreased to 0.145 W/m/degree C, which is significantly lower than 0.196 W/m/degree C at 100 kPa. This finding is consistent with the results of previous researchers. The reduction of the apparent thermal conductivity at low pressures is ascribed to the Knudsen effect. Since the characteristic length of the void space in bulk JSC-1A varies over a wide range, both the Knudsen regime and continuum regime can coexist in the pore space. The volume ratio of the two regimes varies with pressure. Thus, as gas pressure decreases, the gas volume controlled by Knudsen regime increases. Under Knudsen regime the resistance to the heat flow is higher than that in the continuum regime, resulting in the observed pressure dependency of the apparent thermal conductivity.
Yuan, Zeng-Guang; Kleinhenz, Julie E.
Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure
The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C
Study on Electrical Conductivity of Coal.
One of the engineering techniques in underground coal gasification is the electrical linking of holes drilled into the coal seam. The magnitude of electrical conductivity is one of the factors that will determine whether electrical linking is appropriate....
H. Ohuchi J. Soma T. Isobe
Characterization of electrically conducting oxides
This report discusses some of the highlights and publications of this years work. Listed below are the areas of interest and progress within the program: The studies of the Ba{sub 2}YCu{sub 3}O{sub 7-x} system have shown that the conduction processes (metallic or small polaron) have little temperature dependence and are almost entirely a function of oxygen stoichiometry. The substitution of 10 to 20 m% Ca and Co into LaCrO{sub 3} has enabled the system to be sintered to >95% TD at 1400{degree}C without deterioration of either the electrical conductivity or high temperature stability of the resulting dense ceramics. An elucidation of the structure of the high temperature (1400{degree}C) phases of La substitute SrTiO{sub 3} has demonstrated our abilities to determine small changes in structure as well as to determine cation defect concentrations using x-ray powder diffraction methods. In this study we were able to show that the oxidized state of Sr{sub 1-x}La{sub x}TiO{sub 3} contained cation vacancies. The studies in the Y{sub 1-x}Ca{sub x}CrO{sub 3} system also are yielding some important results. They are showing that this oxide system is more stable toward reduction than LaCrO{sub 3}. The construction of dual high temperature controlled atmosphere dilatometer has been completed. An effective-medium theory of hopping transport in binary systems is explaining the conductivity changes that occur when Mn is substituted into LaCrO{sub 3}.
Anderson, H.U.; Sparlin, D.M.
Electrical Conductivity of Ferritin Proteins by Conductive AFM
Electrical conductivity measurements were performed on single apoferritin and holoferritin molecules by conductive atomic force microscopy. Conductivity of self-assembled monolayer films of ferritin molecules on gold surfaces was also measured. Holoferritin was 5-25 times more conductive than apoferritin, indicating that for holoferritin most electron-transfer goes through the ferrihydrite core. With 1 V applied, the average electrical currents through single holoferritin and apoferritin molecules were 2.6 PA and 0.19 PA, respectively.
Xu, Degao; Watt, Gerald D.; Harb, John N.; Davis, Robert C.
Effective electrical conductivity of a nonuniform plasma
A simple nonuniformity model for calculating effective electrical conductivity and Hall parameter is proposed. The model shows that the effective conductivity can be significantly reduced by nonuniformities in the Hall parameter, even if the local conductivity is uniform.
Nichols, L. D.
EPA Science Inventory
We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light non-aqueous phase liquid (LNAPL). The bulk conductivity was measured using in situ vertical resistivity probes, while the most probable number met...
Electrically conductive fibers thermally isolate temperature sensor
Mounting assembly provides thermal isolation and an electrical path for an unbacked thermal sensor. The sensor is suspended in the center of a plastic mounting ring from four plastic fibers, two of which are coated with an electrically conductive material and connected to electrically conductive coatings on the ring.
De Waard, R.; Norton, B.
The electrical conduction in polyimide nanocomposites
The electrical properties of polyimide based nanocomposites were fully investigated by isothermal steady-state current, dielectric spectroscopy, and thermally stimulated current measurements. The effect of nano fillers on the dielectric properties was evaluated via the interfacial polarization as well as the electrical conduction mechanism study. The electrical conduction of polyimide nanocomposites is found to be thermally assisted ionic in nature. The
Yang Cao; Patricia C Irwin
Electrical Conductivity of Serpentinized Rocks to 6 Kilobars
Electrical conductivity of serpentinized rocks from the Indian Ocean ridge is 3-4 orders of magnitude higher than that of serpentine-free peridotitc, hornblende gabbro, and basalt from the same area and from the Tonga trench. The enhanced conduction is apparently characteristic of many but not all serpentine-rich rocks and may be due in part to high porosity and in part to
R. M. Stesky; W. F. Brace
Electrical conductivity imaging by magnetic resonance electrical impedance tomography (MREIT).
Magnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross-sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting subject when an electrical current is injected into the subject. In this work the results of an electrical conductivity imaging experiment are presented, along with some practical considerations regarding MREIT. The MREIT experiment was performed with a 0.3 Tesla MRI system on a phantom made of two compartments with different electrical conductivities. The current density inside the phantom was measured by the MR current density imaging (MRCDI) technique. The measured current density was then used for conductivity image reconstruction by the J-substitution algorithm. The conductivity phantom images obtained with an injection current of 28mA showed conductivity errors of about 25.5%. PMID:14523975
Oh, Suk H; Han, Jae Y; Lee, Soo Y; Cho, Min H; Lee, Byung I; Woo, Eung J
Electrically conductive glass fibre reinforced epoxy resin
The research on an industrially manufactured, electrically conductive glass fibre reinforced epoxy prepreg for aviation applications\\u000a is reported. In a co-operative effort between Technical University Hamburg-Harburg (TUHH) and Daimler-Benz Aerospace Airbus\\u000a (DASA) a new glass-epoxy composite with both electrical and good mechanical properties was successfully developed. The electrical\\u000a conductivity was achieved adding carbon black as a conductive filler into the
M. Kupke; Hans-Peter Wentzel; Karl Schulte
Electrical conduction in fluoropolymer films
Isothermal charging, discharging and transport currents in fluoropolymer films are measured in the temperature range of 50 to 200�C at electric fields to 40 MV\\/m. The currents are measured as a function of time elapsed after the application of steady state voltages in the range of 1 to 104 s. Charging currents increase with time to 103 s, depending upon
Z. Leo Wu; G. R. Govinda Raju
High Temperature Electrical Conductivity of Aluminum Nitride.
The electrical conductivity of high purity (99.8 pct) AlN has been determined using both a-c and d-c techniques. Measurements were made at temperatures between 700 and 1000 C and in a nitrogen pressure range of 1 to .001 atm. The electrical conductivity i...
R. W. Francis W. L. Worrell
Qualification of black electrically conductive paint
A paint having low electrical resistance has been developed. Using a low outgassing polyurethane resin, specific amounts of conductive carbon particles were added to produce paint compositions having a range of electrical resistance. Methods of testing for electrical resistance are discussed. The adhesion of these paints has been tested successfully over the temperature range from liquid nitrogen temperature up to 80 C (176 F).
Park, J. J.; Clatterbuck, C. H.
Electrical conduction models for isotropically conductive adhesive joints
An electrical conduction model for silver filled isotropically conductive adhesives (ICA) was developed. The model combines the microscopic resistance of the bulk silver particles and the contact between silver flakes with the macroscale resistor network calculation by percolation theory. The resistivities of the composites were calculated by resistor network simulations considering both contact effects and particle size effects. Three different
Li Li; James E. Morris
An apparatus to measure the apparent thermal conductivity of multilayer insulation (MLI)
The design of a concentric cylinder calorimeter for measuring the apparent thermal conductivity of MLI blankets is presented. Unlike similar devices where a liquid cryogen is used to control the cold boundary temperature and the cryogen boil-off rate is used to obtain the heat transfer through blanket, the design presented in this paper utilizes mechanical refrigerators to control the boundary temperatures and a heat rate meter to determine the heat load. This approach ensures two unique features of the apparatus. First, the use of cryocoolers enables the user to set the boundary temperatures anywhere within the operating range of the refrigerators and therefore permits a wide range of temperature and temperature differences with the measurement. The other unique feature is that the total heat transfer through the blanket is obtained by measuring the heat conducted along a cold cylinder support rod of known thermal conductivity. To determine the absolute thermal conductivity, a calibration is needed to eliminate the temperature related effects on the support rod.
Celik, Dogan; Klimas, Richard John; Van Sciver, Steven; Zia, Jalal
Electrically Conductive Polyimide Films Containing Gold Surface
Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.
Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.
Laboratory Electrical Conductivity Measurement of Mantle Minerals
Electrical conductivity structures of the Earth�s mantle estimated from the magnetotelluric and geomagnetic deep sounding\\u000a methods generally show increase of conductivity from 10?4�10?2 to 100�S\\/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower\\u000a mantle, the possible existence of a highly conductive layer has been proposed at the base of
Takashi Yoshino
Sprayable Electrically Conductive Polymer Concrete Coatings.
A sprayable electrically conductive polymer concrete coating for vertical and overhead applications has been developed. The technology, in conjunction with impressed current cathodic protection, can be used to prevent corrosion of the embedded reinforcing...
J. J. Fontana W. Reams D. Elling
Electrically Conductive Containment Vessel for Molten Aluminum.
The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreac...
C. E. Holcombe D. G. Scott
Biochemical status of renal epithelial Na+ channels determines apparent channel conductance, ion selectivity, and amiloride sensitivity.
Purified bovine renal papillary Na+ channels, when reconstituted into planar lipid bilayers, reside in three conductance states: a 40-pS main state, and two subconductive states (12-13 pS and 24-26 pS). The activity of these channels is regulated by phosphorylation and by G-proteins. Protein kinase A (PKA)-induced phosphorylation increased channel activity by increasing the open state time constants from 160 +/- 30 (main conductance), and 15 +/- 5 ms (both lower conductances), respectively, to 365 +/- 30 ms for all of them. PKA phosphorylation also altered the closed time of the channel from 250 +/- 30 ms to 200 +/- 35 ms, thus shifting the channel into a lower-conductance, long open time mode. PKA phosphorylation increased the PNa:PK of the channel from 7:1 to 20:1, and shifted the amiloride inhibition curve to the right (apparent K(i)amil from 0.7 to 20 microM). Pertussis toxin-induced ADP-ribosylation of either phosphorylated of either phosphorylated or nonphosphorylated channels decreased the PNa:PK to 2:1 and 4:1, respectively, and altered K(i)amil to 8 and 2 microM for phosphorylated and nonphosphorylated channels, respectively. GTP-gamma-S treatment of either phosphorylated or nonphosphorylated channels resulted in an increase of PNa:PK to 30:1 and 10:1, respectively, and produced a leftward shift in the amiloride dose-response curve, altering K(i)amil to 0.5 and 0.1 microM, respectively. These results suggest that amiloride-sensitive renal Na+ channel biophysical characteristics are not static, but depend upon the biochemical state of the channel protein and/or its associated G-protein. Images FIGURE 1
Ismailov, I I; Berdiev, B K; Benos, D J
Electrically Conductive White Thermal-Control Paint
Report describes development of white thermal-control paint intended for use on spacecraft. Paint required to exhibit combination of high emittance (equal to or greater than 0.90), low absorptance (equal to or less than 0.20), and electrical conductivity sufficient to prevent charging with static electricity to potentials beyond range of plus or minus 10 V.
Hsieh, Cheng-Hsien; Forsberg, Gustaf A.; O'Donnell, Timothy P.
Electrical conductivity of nickel nanostrand polymer composites
The electrical conductivity properties of nickel nanostrands in polymer composite systems are investigated and characterized. Recently developed nickel nanostrands feature a three-dimensionally interconnecting and branching nanostructure that is shown to be highly effective at imparting electrical conductivity in polymer composites. A systematic investigation of material behaviors is undertaken, with results that have been or will be published in a series of journal articles. The content of the studies that form these articles is given herein as the core content of this work. The first study investigates the basic electrical and mechanical properties of nanostrands in a single polymer system. Key results indicate a strong dependence of conductivity properties on processing conditions, volume fraction of conductor, and sample geometry. Mechanical properties are not significantly altered by the presence of nanostrands. The dispersed nanostrand structure is next investigated through the development of statistical topology tools that can quantify nanostrand dispersions and correlate them to the electrical resistivity of composite films. Quantification of the dispersed nanostructure is a significant improvement over common literature approaches. The next step tests full percolation characterization across multiple polymer systems, and indicates a strong dependence on electrical resistivity between polymer types. Polymer constituent properties are found to be poor predictors of nanostrand composites conductivities, though further testing of addition metrics is expected to bring improved correlation. The concluding investigation seeks electrical conductivity percolation models for nanostrand composites. Existing models show only moderate accuracy, and a newly developed combined percolation tunneling approached is suggested for improved fit to measured conductivity.
Hansen, Nathan D.
Electrical conductivities of deep mantle materials
The electrical conductivity is one of key physical properties of the Earth�s mantle. Joint analyses with the geomagnetic observations and laboratory-based electrical conductivity models provide us more constraints on the propagation of the geomagnetic signals to the Earth�s surface, the nature of the core-mantle coupling, the subtle chemistry and temperature of the deep Earth. In spite of its importance, the measurements on electrical conductivities of lower mantle materials have been mainly performed at relatively lower pressures below 40 GPa (e.g., Shankland et al., 1993). Although recently discovered iron spin transition and post-perovskite phase transition may have significant effect on the electrical conductivity of lower mantle, it has not been investigated. Relation between electrical property and crystal structure in FeO at high pressure and temperature conditions is also still unknown (e.g., Knittle and Jeanloz, 1986). We performed the electrical conductivity measurements on the deep mantle materials at in-situ high pressures and temperatures in a laser-heated diamond anvil cell. We examined the effect of iron spin transition both in perovskite and ferropericlase and post-perovskite phase transition on the electrical conductivity. High-pressure metallization in FeO was also investigated. In addition, electrical conductivities of natural pyrolitic mantle and MORB materials were measured at high pressure and temperature covering the entire lower mantle conditions. It was found in this study that iron spin transition in both ferropericlase and perovskite significantly diminished its electrical conductivity (Ohta et al., 2007, 2008, 2010a), while post-perovskite phase transition increased the electrical conductivity by several orders of magnitude (Ohta et al., 2008). Measured conductivity of normal NiAs-type FeO showed metallic behavior, which was contradictory to those of B1 and rB1 phases. In contrast to the previous laboratory-based models, our data demonstrate that the conductivity of pyrolite does not increase monotonically but varies dramatically with depth in the lower mantle (Ohta et al., 2010b). These new findings surely have important implications for the chemistry and dynamics of deep mantle and core.
Ohta, K.; Hirose, K.; Shimizu, K.; Ohishi, Y.
Electrical conductivity and Paleo-Proterozoic foredeeps
Sedimentary facies associated with Paleo-Proterozoic foredeeps are apparently highly conductive. The conductive lithology appears to be a euxinic carbonaceous shale deposited on preforedeep continental margin facies. The shale is overlaid by axial turbidites and often incorporated into the succeeding fold and thrust belt. Carbonaceous shales can be made highly conducting if graphitized by exposure to temperatures exceeding 400�C. Although foredeep facies develop diachronously, the most conductive unit is usually found in the core of the fold and thrust belt, suggesting that deformation may be essential for the complete graphitization of the carbon. The foredeep hypothesis offers an attractive explanation for several highly conductive features detected in the upper and middle crust in Laurentia, and possibly throughout the world. The euxinic facies represent highly specific, tectonic marker horizons that are readily delineated by using electromagnetic methods.
Boerner, D. E.; Kurtz, R. D.; Craven, J. A.
Combining Proximal and Penetrating Soil Electrical Conductivity Sensors for High-Resolution Digital Soil Mapping
\\u000a Proximal ground conductivity sensors produce high spatial resolution maps that integrate the bulk electrical conductivity\\u000a (ECa) of the soil profile. For meaningful interpretation, variability in conductivity maps must either be inverted to profile\\u000a conductivity or be directly calibrated to profile properties. Penetrating apparent electrical conductivity (ECa�P) sensors produce high depth resolution data at relatively fewer spatial locations. The objectives of
D. B. Myers; N. R. Kitchen; K. A. Sudduth; S. Grunwald; R. J. Miles; E. J. Sadler; R. P. Udawatta
Mechanisms of electrical conductivity in olivine
Data on the electrical conductivity and the thermoelectric effect in single crystals indicate that the charge conduction mechanism in pure magnesium forsterite is electrons. The concentration of electrons can be varied by controlling the number of oxygen vacancies through manipulation of the oxygen pressure. For iron bearing olivine, the conduction mechanism is by electron holes localized on an iron ion. Since iron strongly affects the creep process as well, oxidation of iron is probably accompanied by the production of magnesium vacancies. 15 references.
Schock, R.N.; Duba, A.G.; Shankland, T.J.
Balloon observations of stratospheric electricity above the South Pole - Vertical electric field, conductivity, and conduction current
Results are summarized of measurements of the electrical conductivity and vertical component of the vector electric field acquired from eight stratospheric balloon flights launched from the South Pole in the austral summer of 1985-1986. The data are a contribution to the set of global atmospheric electricity measurements and extend the work of Cobb (1977) to determine the electrical environment of
G. J. Byrne; J. R. Benbrook; E. A. Bering
Comparison of Electromagnetic Induction and Direct Sensing of Soil Electrical Conductivity
et al. (1989) modeled ECa as a function of soil water content (both the mobile and immobile fractions), the Apparent profile soil electrical conductivity (ECa) can be an indi- electrical conductivity (EC) of the soil water, soil bulk rect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can be used to efficiently and density,
K. A. Sudduth; N. R. Kitchen; G. A. Bollero; D. G. Bullock; W. J. Wiebold
Electrical conductivity of hot QCD matter.
We study the electric conductivity of hot QCD matter at various temperatures T within the off-shell parton-hadron-string dynamics transport approach for interacting partonic, hadronic or mixed systems in a finite box with periodic boundary conditions. The response of the strongly interacting system in equilibrium to an external electric field defines the electric conductivity ?(0). We find a sizable temperature dependence of the ratio ?(0)/T well in line with calculations in a relaxation time approach for T(c)electric conductor than Cu or Ag (at room temperature). PMID:23683192
Cassing, W; Linnyk, O; Steinert, T; Ozvenchuk, V
Airborne measurements of atmospheric electrical conductivities
Atmospheric electrical polar conductivities were measured using a Gerdien condenser mounted on an aircraft. These surveys, conducted over the western coast of South India, have detected enhanced conductivities associated with the placer deposits of the radioactive mineral monazite found in this region. The data reflect the variation in the level of surface radioactivity along the flight routes. In one flight that rose over the sea up to 1 km, the effect of radioactivity was seen to extend up to this point. Over land the influence of the surface radioactivity on electrical conductivity is mostly confined to the region of occurrence of the deposits. These studies also suggest the possibility of employing the Gerdien condenser in preliminary surveys to detect the presence of radioactivity.
Sampath, S.; Sasi Kumar, V.; Murali Das, S.
Changes During Storage of Electrically Conductive Blends Polyaniline�Poly(Ethylene?co?vinyl Acetate)
The electrical conductivity behavior of polyaniline�poly(ethylene?co?vinyl acetate) (PANI�EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (?c) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5�wt.%) increased by several
T. Tsanov; P. Mokreva; D. Tsocheva; L. Terlemezyan
The electrical conductivity of the moon
Some new aspects of lunar electrical conductivity are examined with reference to available data for the earth. A mathematical analysis is employed to determine zones at the lunar surface where high-order harmonics of magnetic fields have the lowest contributing effect. Attention is given to results from magnetovariation lunar sounding and from Apollo 12 and Explorer 35 magnetometers. Implications discussed have bearing on knowledge of regional anomalies in lunar conductivity.
Vanyan, L. L.
Electric conductivity and bootstrap current in tokamak.
A modified Ohm's law for the electric conductivity calculation is presented, where the modified ohmic current can be compensated by the bootstrap current. A comparison of TEXT tokamak experiment with the theories shows that the modified Ohm's law is a mor...
Mao Jianshan Wang Maoquan
Calculation of electric fields in conductive media
A method is presented, based upon finite-difference forms of Laplace's equation, for the iterative calculation of three-dimensional electric field distributions in electrically conductive media. The method, while generally applicable to any conductive media, will be presented with emphasis on its use for the prediction of power density in tissue when radio-frequency hyperthermia is utilized in the treatment of cancer. A computer code which performs these calculations has been written in BASIC so that it may be adapted to relatively inexpensive desktop computers for use in treatment planning. Example calculations of the distribution of electric potential, gradient, and power density with specific electrode configurations are presented. Applications and limitations of the technique are discussed.
Doss, J.D.
Thermal and electrical contact conductance studies
Prediction of electrical and thermal contact resistance for pressed, nominally flat contacts is complicated by the large number of variables which influence contact formation. This is reflected in experimental results as a wide variation in contact resistances, spanning up to six orders of magnitude. A series of experiments were performed to observe the effects of oxidation and surface roughness on contact resistance. Electrical contact resistance and thermal contact conductance from 4 to 290 K on OFHC Cu contacts are reported. Electrical contact resistance was measured with a 4-wire DC technique. Thermal contact conductance was determined by steady-state longitudinal heat flow. Corrections for the bulk contribution ot the overall measured resistance were made, with the remaining resistance due solely to the presence of the contact.
Vansciver, S. W.; Nilles, M.
Ionization and electrical conductivity of dense carbon
The electrical conductivity of a dense carbon plasma has been calculated by using a linear mixture rule considering various interactions among electrons, atoms, and ions in the density and temperature ranges of 10-5 - 10 g cm-3 and 104 - 105 K, respectively. The non-ideal Saha equation is used to obtain the plasma composition and the degree of ionization successfully. The present calculation spans from the weakly coupled, nondegenerate region to the strong coupled, degenerate domain. The calculated conductivity is in reasonable agreement with the explosive wire measurement and the quantum kinetic calculation. A nonmetal-metal transition is predicted to occur at 0.56 g cm-3 at temperatures lower than 3 � 104 K based on the calculation of the electrical conductivity.
Fu, Zhijian; Sun, Xiaowei; Quan, Weilong
DC electrical conductivity study of cerium doped conducting glass systems
The glass samples of composition 60V2O5-5P2O5-(35-x)B2O3-xCeO2, (1 <= x <= 5) were prepared by the conventional melt quench method. The samples were characterized by X-ray diffraction and thermo gravimetric-differential thermal analysis. The glass transition temperature and crystallization temperature determined from TG-DTA analysis. The DC electrical conductivity has been carried out in the temperature range 303-473 K. The maximum conductivity and minimum activation energy were found to be 0.039 Scm-1 and 0.15 eV at 473 K for x=1, respectively.
Barde, R. V.; Waghuley, S. A.
Electrical Conductance and Reversible Conductance Switching in Molecular Junctions
A technology is demonstrated to fabricate reliable molecular metal-molecule-metal junctions with unprecedented device diameters up to 100 ?m. The yield of these molecular junctions is close to unity. Stability investigations have shown a shelf life of years and no deterioration upon cycling. Key ingredients are the use of a conducting polymer layer (PEDOT:PSS) sandwiched between the self-assembled monolayer (SAM) and the top electrode to prevent electrical shorts, and processing in lithographically defined vertical interconnects (vias) to prevent both parasitic currents and interaction between the environment and the SAM [1--3]. Furthermore, a fully functional solid-state molecular electronic switch is manufactured by conventional processing techniques. The molecular switch is based on a monolayer of photochromic diarylethene molecules sandwiched between two electrodes. The monolayer reversibly switches the conductance by more than one order of magnitude between the two conductance states via optical addressing. This bidirectional conductance switch operates as an electronic ON/OFF switch and as a reprogrammable data storage unit that can be optically written and electronically read [4]. [4pt] [1] Nature, 441, 69--72 (2006). [0pt] [2] Proc. Natl Acad. Sci USA, 104, 11161-11167 (2007). [0pt] [3] Nature Nanotechn., 3, December issue (2008) [0pt] [4] Adv. Mater. 20, 1467--1473.
de Boer, Bert
Electrical conductivity of metal powders under pressure
A model for calculating the electrical conductivity of a compressed powder mass consisting of oxide-coated metal particles has been derived. A theoretical tool previously developed by the authors, the so-called `equivalent simple cubic system', was used in the model deduction. This tool is based on relating the actual powder system to an equivalent one consisting of deforming spheres packed in a simple cubic lattice, which is much easier to examine. The proposed model relates the effective electrical conductivity of the powder mass under compression to its level of porosity. Other physically measurable parameters in the model are the conductivities of the metal and oxide constituting the powder particles, their radii, the mean thickness of the oxide layer and the tap porosity of the powder. Two additional parameters controlling the effect of the descaling of the particle oxide layer were empirically introduced. The proposed model was experimentally verified by measurements of the electrical conductivity of aluminium, bronze, iron, nickel and titanium powders under pressure. The consistency between theoretical predictions and experimental results was reasonably good in all cases.
Montes, J. M.; Cuevas, F. G.; Cintas, J.; Urban, P.
Electrical conductivity of acidic sulfate solution
The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.
Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook
The electrical conductivity of sodium polysulfide melts
The electrical conductivities of sodium polysulfide melts, Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5}, were measured as a function of temperature between 300 and 360 C. Due to the viscous nature of the sodium polysulfide melts, the conductance cells are axisymmetric cylindrical cells with a microelectrode, instead of capillary cells. The values of the Arrhenius activation energy derived from the experimental conductivity data are about 33 kJ/mol. The macroscopic model of sodium polysulfide melts has described the melts as composed of sodium cations, monosulfide anions, and neutral sulfur solvent. For this model, the binary interaction coefficients quantifying the interaction between sodium cations and monosulfide anions were calculated from the experimental conductivity data and literature data for the transference number, diffusion coefficient, activity coefficient, and density.
Wang, M.H.; Newman, J. [Lawrence Berkeley Lab., CA (United States). Energy and Environment Division]|[Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering
Electric conductance of highly selective nanochannels
We consider electric conductance through a narrow nanochannel in the thick-double-layer limit, where the space-charge Debye layers adjacent to the channel walls overlap. At moderate surface-charge densities the electrolyte solution filling the channel comprises mainly of counterions. This allows to derive an analytic closed-form approximation for the channel conductance, independent of the salt concentration in the channel reservoirs. The derived expression consists of two terms. The first, representing electromigratory transport, is independent of the channel depth. The second, representing convective transport, depends upon it weakly.
Schnitzer, Ory; Yariv, Ehud
Electrically conductive palladium containing polyimide films
Lightweight, high temperature resistant, electrically conductive, palladium containing polyimide films and methods for their preparation are described. A palladium (II) ion-containing polyamic acid solution is prepared by reacting an aromatic dianhydride with an equimolar quantity of a palladium II ion-containing salt or complex and the reactant product is cast as a thin film onto a surface and cured at approximately 300 C to produce a flexible electrically conductive cyclic palladium containing polyimide. The source of palladium ions is selected from the group of palladium II compounds consisting of LiPdCl4, PdS(CH3)2Cl2Na2PdCl4, and PdCl2. The films have application to aerodynamic and space structures and in particular to the relieving of space charging effects.
Taylor, L. T.; St.clair, A. K.; Carver, V. C.; Furtsch, T. A. (inventors)
Electrically conducting polyimide film containing tin complexes
Disclosed is a thermally-stable SnO.sub.2 -surfaced polyimide film wherein the electrical conductivity of the SnO.sub.2 surface is within the range of about 3.0.times.10.sup.-3 to about 1.times.10.sup.-2 ohms.sup.-1,. Also disclosed is a method of preparing this film from a solution containing a polyamic acid and SnCl.sub.4 (DMSO).sub.2.
St. Clair, Anne K. (Inventor); Ezzell, Stephen A. (Inventor); Taylor, Larry T. (Inventor); Boston, Harold G. (Inventor)
Electrical conductivity of Co doped cuprous oxide
The solubility limit of metals in cuprous oxide is very low and it is therefore difficult to form solid solutions of metal\\u000a oxides with cuprous oxide. In an on going research looking for such solid solutions and their properties we have prepared\\u000a Co doped Cu2O. We report here on measurements of the electrical conductivity of Co doped Cu2O as a
Y. Tsur; I. Riess
Damage Detection in Electrically Conductive Structures
High-technology systems are in need of structures that perform with increased functionality and a reduction in weight, while simultaneously maintaining a high level of performance and reliability. To accomplish this, structural elements must be designed more efficiently and with increased functionality, thereby creating multifunctional structures (MFS). Through the addition of carbon fibers, nanotubes, or particles, composite structures can be made electrically conductive while simultaneously increasing their strength and stiffness to weight ratios. Using the electrical properties of these structures for the purpose of damage detection and location for health and usage monitoring is of particular interest for aerospace structures. One such method for doing this is Electrical Impedance Tomography (EIT). With EIT, an electric current is applied through a pair of electrodes and the electric potential is recorded at other monitoring electrodes around the area of study. An inverse solution of the governing Maxwell equations is then required to determine the conductivities of discrete areas within the region of interest. However, this method is nearly ill-posed and computationally intensive as it focuses on imaging small changes in conductivity within the region of interest. For locating damage in a medium with an otherwise homogeneous conductivity, an alternative approach is to search for parameters such as the damage location and size. Towards those ends, this study develops an Artificial Neural Network (ANN) to determine the state of an electrically conductive region based on applied reference current and electrical potentials at electrodes around the periphery of the region. A significant benefit of the ANN approach is that once trained, the solution of an inverse problem does not require costly computations of the inverse problem. This method also takes advantage of the pattern recognition abilities of neural networks and is a robust solution method in the presence of signal noise. The network is based on a two-tier approach where the coarse location of the damage is first located within given regions using a Learning Vector Quantization (LVQ) network. Once the approximate location is known, the second step is to apply a more refined feed-forward back-propagation (FFBP) ANN that utilizes the current and electric potential electrodes that focus on that region. In this manner, the resolution of the prediction scheme is increased. To train both the LVQ and FFBP networks, instead of time consuming and perhaps for large space structures, unfeasible experiments, a computational model is developed. The training function for the ANN is based on a finite element solution of the region and the applied boundary conditions. The inputs to the network are thus the location of the current electrodes and the corresponding electric potential values around the periphery and the network targets are the damage location and size. Future work will focus on the further development of the two-tier ANN, extension of the scheme for plural defects, and on the experimental validation of the computational training model for materials with isotropic and anisotropic conductivity.
Anderson, Todd A.
The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5} were measured as a function of temperature (range: 300 to 360{degree}C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.
Meihui Wang.
Electrical Noise in Individual Conducting Polymer Nanowires
Electrical property characterizations of conducting polymer nanostructures have been limited primarily to resistance measurements. Electrical noise is one aspect that is usually overlooked, yet critical to their device performance. Moreover, electrical noise is more sensitive to the polymer doping and microstructure than resistance, which makes it particularly interesting for sensor applications. In this talk, we will present the results on the electrical noise measurements of individual multisegmented electrodeposited nanowires based on Poly(3,4-ethylenedioxythiophene (PEDOT) [1]. The polymer was electrochemically doped with either poly(4-styrenesulfonic acid) (PSS) or perchlorate (ClO4). The nanowires had gold contacts on both ends and were measured in four-point and two-point configurations. We found that the electrical noise behavior is typical of 1/f noise, with a spectral density that depends on the polymer structure and is affected by the ambient conditions. Our data show that the contact noise represents a significant contribution to the total noise level. We will discuss the interpretation of these results assuming that the polymer is a disordered conductor. [1] Cao et al., Nano Letters Article ASAP
Kovalev, Alexey; Cao, Yanyan; Mayer, Theresa; Mallouk, Thomas
Inductive Measurement of Plasma Jet Electrical Conductivity
An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.
Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.
Finite Element Model of Cardiac Electrical Conduction.
In this thesis, we develop mathematical models to study electrical conduction of the heart. One important pattern of wave propagation of electrical excitation in the heart is reentry which is believed to be the underlying mechanism of some dangerous cardiac arhythmias such as ventricular tachycardia and ventricular fibrillation. We present in this thesis a new ionic channel model of the ventricular cardiac cell membrane to study the microscopic electrical properties of myocardium. We base our model on recent single channel experiment data and a simple physical diffusion model of the calcium channel. Our ionic channel model of myocardium has simpler differential equations and fewer parameters than previous models. Further more, our ionic channel model achieves better results in simulating the strength-interval curve when we connect the membrane patch model to form a one dimensional cardiac muscle strand. We go on to study a finite element model which uses multiple states and non-nearest neighbor interactions to include curvature and dispersion effects. We create a generalized lattice randomization to overcome the artifacts generated by the interaction between the local dynamics and the regularities of the square lattice. We show that the homogeneous model does not display spontaneous wavefront breakup in a reentrant wave propagation once the lattice artifacts have been smoothed out by lattice randomization with a randomization scale larger than the characteristic length of the interaction. We further develop a finite 3-D 3-state heart model which employs a probability interaction rule. This model is applied to the simulation of Body Surface Laplacian Mapping (BSLM) using a cylindrical volume conductor as the torso model. We show that BSLM has a higher spatial resolution than conventional mapping methods in revealing the underlying electrical activities of the heart. The results of these studies demonstrate that mathematical modeling and computer simulation are very useful tools to study the electrical conduction of the heart. Our new ionic channel model can be used in future higher dimensional model study of cardiac electrical conduction. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).
Yin, John Zhihao
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Apparently Negative Electric Polarization in Shaped Graded Dielectric Materials
By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently negative electric polarization (ANEP), which is due to a symmetric oscillation of the paired electric permittivities, satisfying a sum rule. The ANEP does not occur for a
Chun-Zhen Fan; Yin-Hao Gao; Yong Gao; Ji-Ping Huang
[The electrical conductivity of triggered lightning channel].
Spectra of return strokes for artificial triggered lightning were obtained by optical multi-channel analyzer (OMA) in Shandong region. Compared with previous spectra of natural lightning, additional lines of ArI 602.5 nm and ArII 666.5 nm were observed. Under the model of local thermodynamic equilibrium, electronic temperatures of the lightning channel plasma were obtained according to the relative line intensities. Meanwhile, with semi-empirical method the electron density was obtained by Halpha line Stark broadening. In combination with plasma theory, electrical conductivity of the lightning channel has been calculated for the first time, and the characteristic of conductivity for lightning channel was also discussed. The relation between the electrical conductivity of channel and the return stroke current was analyzed, providing reference data for further work on computing return stroke current. Results show that the lightning channel is a good conductor, and electrons are the main carrier of channel current. The brightness of artificial triggered lightning channel is usually higher than that of natural lightning, and its current is smaller than that of the natural lightning. PMID:18306764
Zhang, Hua-ming; Yuan, Ping; Su, Mao-gen; L�, Shi-hua
Numerical recovery of certain discontinuous electrical conductivities
The inverse problem of recovering an electrical conductivity of the form Gamma(x) = 1 + (k-1)(sub Chi(D)) (Chi(D) is the characteristic function of D) on a region omega is a subset of 2-dimensional Euclid space from boundary data is considered, where D is a subset of omega and k is some positive constant. A linearization of the forward problem is formed and used in a least squares output method for approximately solving the inverse problem. Convergence results are proved and some numerical results presented.
Bryan, Kurt
Electrically-conducting thermal-control coating
Coating comprised mainly of zinc and aluminum oxides is characterized by high thermal emittance, low thermal absorption, and high electrical conductivity. Originally developed to protect spacecraft, coating can be used to prevent charge buildup on components in other applications. Mixture is stable under ultraviolet and X-ray radiation and under bombardment by ionizing particles. It can be applied to aluminum, stainless steel, epoxy/fiberglass, and other substrates. When exposed to equivalent of 1,000 Sun-hours illumination, coating remained stable and retained its optical properties.
Shai, M. C.
Electrically conductive polyurethanes for biomedical applications
Electrical interfacing with neural tissue poses significant problems due to host response to the material. This response generally leads to fibrous encapsulation and increased impedance across the electrode. In neural electrodes such as cochlear implants, an elastomeric material like silicone is used as an insulator for the metal electrode. This project ultimately aims to produce a polymer electrode with elastomeric mechanical properties, metal like conductivity and capability. The approach taken was to produce a nanocomposite elastomeric material based on polyurethane (PU) and carbon nanotubes. Carbon nanotubes are ideal due to their high aspect ratio as well as being a ballistic conductor. The choice of PU is based on its elastomeric properties, processability and biocompatibility. Multi-walled nanotubes (MWNTs) were dispersed ultrasonically in various dispersive solutions before being added at up to 20wt% to a 5wt% PU (Pellethane80A) in Dimethylacetamide (DMAc). Films were then solvent cast in a vacuum oven overnight. The resulting films were tested for conductivity using a two-probe technique and mechanically tested using an Instron tensiometer. The percolation threshold (p) of the PU/MWNT films occurred at loadings of between 7 and 10 wt% in this polymer system. Conductivity of the films (above p) was comparable to those for similar systems reported in the literature at up to approximately 7x10-2 Scm-1. Although PU stiffness increased with increased %loading of nanotubes, all composites were highly flexible and maintained elastomeric properties. From these preliminary results we have demonstrated electrical conductivity. So far it is evident that a superior percolation threshold is dependent on the degree of dispersion of the nanotubes. This has prompted work into investigating other preparations of the films, including melt-processing and electrospinning.
Williams, Charles M.; Nash, M. A.; Poole-Warren, Laura A.
Local Electrical Conductivity of Multiferroic Domain Walls
There is an intense interest in magnetoelectric coupling between electric and magnetic due to its potential to the revolutionary of device architectures. Single-phase multiferroics - materials that show spontaneous magnetization and polarization simultaneously at ambient conditions remain elusive as most systems (such as the manganites) exhibit multiferroicity only at low temperatures. Alternatively, multiferroics can be synthesized as a composite system, e.g. as a product property of a composite phase consisting of a magnetostrictive and a piezoelectric material. One multiferroic material, however, has played a key role in rejuvenating the field after a report of large ferroelectric polarization combined with interesting magnetic properties - BiFeO3. Here we provide evidence of a unique property of single domain walls in multiferroic BiFeO3. Unlike other multiferroic materials, e.g. PbTiO3, on which the electronic properties of the domain walls are not significantly different from the domain area, we observe a finite electric conductivity at room temperature along such a wall using conductive atomic force microscopy. This intrinsic property of the domain wall is attributed to a changed crystallographic structure as revealed by high resolution transmission electron microscopy. Additionally, optical absorption measurements confirm a change in bandstructure at domain walls in BiFeO3.
He, Qing; Seidel, Jan; Martin, Lane; Chu, Ying-Hao; Zhan, Qian; Wang, Feng; Ramesh, Ramamoorthy
Measurement of apparent thermal conductivity of multilayer insulations at low compressive loads.
A description is presented of the test calorimeter, the experimental technique, and the results obtained in an evaluation of four multilayer insulations selected for application on future multilaunch space vehicles utilizing liquid hydrogen and oxygen for orbital operations. Particular attention is paid to techniques for minimizing error in obtaining thermal conductivity data. The effective conductivity for four high-performance insulations was determined at a minimum of four compressive loads in the range from 0.0001 to 0.1 psi. Results show that the thermal conductivity of multilayer insulations is insensitive to small changes in mechanical loading at 1 torr interstitial gas pressure, but becomes increasingly more sensitive to mechanical loading as the interstitial gas pressure is reduced.
Holmes, V. L.; Mccrary, L. E.; Krause, D. R.
Induction heating of electrically conductive porous asphalt concrete
In this research, an electrically conductive porous asphalt concrete, used for induction heating, was prepared by adding electrically conductive filler (steel fibers and steel wool) to the mixture. The main purpose of this paper is to examine the electrical conductivity and the indirect tensile strength of this conductive porous asphalt concrete and prove that it can be heated via induction
Quantao Liu; Erik Schlangen; �lvaro Garc�a; Martin van de Ven
Application of electrical and electromagnetic depth sounding in highly conductive sediments: The concept of vertical electrical anisotropy
``N�rdlinger Ries'' is a meteorite crater in the Bavarian `Alb' of Germany that was formed 15 million years ago, and subsequently filled with salty water. Evaporation resulted in an approximately 300 meter thick layer of young, highly conductive sediments. Audio-frequency Magnetotelluric (AMT) and geoelectric depth sounding (VES) techniques were used to analyze the electrical properties of these sediments. The apparent
A. K�hler; K. Bahr
System for Measuring the Local Electrical Conductivity of Plasma.
The system for measuring the local electrical conductivity of the plasma of products of combustion (SILYeP) is intended for investigation of the distribution of electrical conductivity of the ionized gas flows (plasma) and the determination of the electri...
N. A. Balashov I. M. Gaponov G. P. Malyuzhonok Y. S. Mikhailov F. M. Oberman
Electrical Conductance of Liquid Propellants: Theory and Results.
An overview of the development of the theory of electrical conductance of electrolytes is presented. Conditions where ion-pairing can occur is emphasized. Electrical conductance versus both concentration and temperature is reported for aqueous hydroxylamm...
J. A. Vanderhoff P. M. Donmoyer S. W. Bunte
Electrical conductivity of thermally hydrogenated nanodiamond powders
Electrical properties of detonation diamond nanoparticles (NDs) with individual diameters of ~5 nm are important for many applications. Although diamond is an insulator, it is known that hydrogen-terminated bulk diamond becomes conductive when exposed to water. We show that heating ND in hydrogen gas at 600-900 �C resulted in a remarkable decrease in resistivity from 107 to 105 ? cm, while the resistivity was essentially unchanged after treatment at 400 �C and lower temperatures. Fourier Transform Infrared Spectroscopy and X-ray photoelectron spectroscopy (XPS) studies revealed that hydrogenation of ND occurs at 600-900 �C, suggesting that the decrease in resistivity is based on transfer doping at the hydrogenated ND surface. Oxidation of the hydrogenated sample at 300 �C recovers resistivity to its original value. The resistivity of treated ND as a function of the O/C atomic ratio showed a transition from resistive (O/C ratio > 0.033) to conductive (O/C ratio < 0.033) state. This is consistent with the idea that the change in the resistivity is caused by the shift of the valence band maximum to above the Fermi level due to the dipole of the C-H bonds leading to transfer doping.
Kondo, Takeshi; Neitzel, Ioannis; Mochalin, Vadym N.; Urai, Junichi; Yuasa, Makoto; Gogotsi, Yury
Photovoltaic device having light transmitting electrically conductive stacked films
A light transmitting electrically conductive stacked film, useful as a light transmitting electrode, including a first light transmitting electrically conductive layer, having a first optical thickness, a second light transmitting layer, having a second optical thickness different from the optical thickness of the first layer, and an electrically conductive metallic layer interposed between and in initimate contact with the first and second layers.
Weber, Michael F. (St. Paul, MN); Tran, Nang T. (St. Paul, MN); Jeffrey, Frank R. (St. Paul, MN); Gilbert, James R. (St. Paul, MN); Aspen, Frank E. (St. Paul, MN)
Chapter A6. Section 6.3. Specific Electrical Conductance
USGS Publications Warehouse
Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.
Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.
Accuracy issues in electromagnetic induction sensing of soil electrical conductivity for precision agriculture
Soil apparent electrical conductivity (ECa) has been used as a surrogate measure for such soil properties as salinity, moisture content, topsoil depth (TD), and clay content. Measurements of ECa can be accomplished with commercially available sensors and can be used to efficiently and inexpensively develop the dense datasets desirable for describing within-field spatial variability in precision agriculture. The objective of
K. A. Sudduth; S. T. Drummond; N. R. Kitchen
Soil electrical conductivity as a function of soil water content and implications for soil mapping
Apparent soil electrical conductivity (ECa) has shown promise as a soil survey tool in the Midwestern United States, with a share of this interest coming from the precision agriculture community. To fully utilize the potential of ECa to map soils, a better understanding of temporal changes in ECa is needed. Therefore, this study was undertaken to compare temporal changes in
Eric C. Brevik; Thomas E. Fenton; Andreas Lazari
Accurate and inexpensive methods for measuring soil properties are required to enhance interpretation of yield maps and improve planning for precision farming strategies. The conventional soil sampling is time consuming and requires intensive laboratory analysis. Hence mapping of apparent profile of soil electrical conductivity (ECa) was developed to identify areas of contrasting soil properties. Such ECa values are surrogate measures
M. S. M. Amin; W. Aimrun; S. M. Eltaib; C. S. Chan
Electrically conductive, immobilized bioanodes for microbial fuel cells
The power densities of microbial fuel cells with yeast cells as the anode catalyst were significantly increased by immobilizing the yeast in electrically conductive alginate electrodes. The peak power densities measured as a function of the electrical conductivity of the immobilized electrodes show that although power increases with rising electrical conductivity, it tends to saturate beyond a certain point. Changing the pH of the anode compartment at that point seems to further increase the power density, suggesting that proton transport limitations and not electrical conductivity will limit the power density from electrically conductive immobilized anodes.
Ganguli, R.; Dunn, B.
Magnetic flowmeter for electrically conductive liquid
A magnetic flowmeter includes first and second tube sections each having ls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. The magnets are provided in matched pairs spaced 180.degree. apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.
Skladzien, Stanley B. (Elmhurst, IL); Raue, Donald J. (Naperville, IL)
A magnetic flowmeter includes first and second tube sections each having walls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. Two magnets are provided in matched pairs spaced 180/sup 0/ apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.
Skladzien, S.B.; Raue, D.J.
Electric Field in Materials, Containing Conductive Nanofibers
Concentrated electric field and its energy in materials, containing nanofibers, are discussed. It is shown that the electric field in the vicinity of the end of a fiber is proportional to the external applied field and to the fiber length, whilst it is inversely proportional to the fiber diameter. Specific electrostatic energy of a fiber in a sample under the
Yuri Kornyushin
Spin state dependence of electrical conductivity of spin crossover materials.
We studied the spin state dependence of the electrical conductivity of the spin crossover compound [Fe(Htrz)(2)(trz)](BF(4)) (Htrz = 1H-1,2,4-triazole) by means of dc electrical measurements. The low spin state is characterized by higher conductance and lower thermal activation energy of the conductivity, when compared to the high spin state. PMID:22466531
Rotaru, Aurelian; Gural'skiy, Il'ya A; Moln�r, G�bor; Salmon, Lionel; Demont, Philippe; Bousseksou, Azzedine
Radiation Fluence dependent variation in Electrical conductivity of Cu nanowires
Electrical conductivity of Cu nanowires varies with diameter of nanowires. However, keeping the diameter of nanowires constant, a variation in their electrical conductivity is observed after they irradiated with gamma rays and neutrons. On the basis of I-V characteristics drawn at room temperature, decrease in the conductivity of Cu nanowires is observed, as compared to that of pristine nanowires.
Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G. [Department of physics, National institute of Technology, Kurukshetra-136119 (India); IUAC, New Delhi (India)
Role of Dislocation Movement in the Electrical Conductance of Nanocontacts
Dislocation is a lattice imperfection of crystalline materials. Dislocation movement is induced during plastic deformation and influences the mechanical properties. Although the role of dislocation in mechanical properties has been well understood, the role of dislocation in electrical properties is completely lacking. Only Matthiessen's rule addresses the electrical influence of dislocations at the macroscale. Here, we show that the electrical conductance change due to dislocations and show their movements through in situ observation of a gold nanocontact. The density of the dislocations in the gold nanocontact did not affect the electrical conductance. The repeated and discrete dislocation movements resulted in an electrical conductance oscillation. Our results demonstrate how dislocations and their movements affect electric conductance at the nanoscale. This instability issue will cause a big problem for future electric devices such as ultra low power electric devices and nanowire photovoltaic devices.
Ishida, Tadashi; Kakushima, Kuniyuki; Mizoguchi, Teruyasu; Fujita, Hiroyuki
Electrical conductivity of nitride carbon films with different nitrogen content
The electrical conductivity of nitride carbon (DLC: N) films has been studied. It is found that the electrical conductivity of the deposited films increases slowly with increasing nitrogen content, however, it decreases after the nitrogen content in the film reaches a certain value of 12.8 at%. Thermal treatment results show that the electrical conductivity of the lowly nitrogen doped DLC film increases rapidly, while that of the heavily doped film decreases after annealing at 300 �C for 30 min. Raman and XPS spectra results show that when the nitrogen content in the films reaches a certain value, there appears nonconductive phases. Therefore the electrical conductivity of the heavily doped films decreases. FTIR spectra analysis results show that the nitrogen atom as an impurity center undergoes an 'activation' process during the thermal treatment, which leads to the increase of the electrical conductivity. Therefore, the nitrogen in these two kinds of films has different effects on the electrical conductivity.
Zhang, Weili; Xia, Yiben; Ju, Jianhua; Wang, Linjun; Fang, Zhijun; Zhang, Minglong
Method of forming an electrically conductive cellulose composite
An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.
Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN); Woodward, Jonathan (Ashtead, GB)
Non-Contact Electrical Conductivity Measurement Technique for Molten Metals
A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.
Rhim, W. K.; Ishikawa, T.
Electrical Conductivity of Metal Powders under Shock Compression
The electrical conductivity of a series of metal powders under shock compression is measured by an electrocontact technique. Initially, the metal particles are covered by an oxide film, and the powder is non-conducting. Under shock compression, the powder acquires macroscopic conductivity. The electrical conductivity of the shock-compressed powder depends substantially on the metal, porosity, particle size, and shock-wave pressure. The
S. D. Gilev
There is an intense interest in magnetoelectric coupling between electric and magnetic due to its potential to the revolutionary of device architectures. Single-phase multiferroics - materials that show spontaneous magnetization and polarization simultaneously at ambient conditions remain elusive as most systems (such as the manganites) exhibit multiferroicity only at low temperatures. Alternatively, multiferroics can be synthesized as a composite system,
Qing He; Jan Seidel; Ying-Hao Chu; Qian Zhan; Feng Wang; Ramamoorthy Ramesh
Electrical conductivity measurements from the STRATCOM 8 experiment
A blunt probe experiment for measuring electrical conductivity was flown with the STRATCOM 8 instrument package. Data were obtained by the instrument throughout the entire measurement period. A preliminary analysis of the data indicates an enhancement in conductivity associated with the krypton discharge ionization lamp, particularly in negative conductivity. The conductivity values and their altitude dependence are consistent with previous balloon and rocket results.
Mitchell, J. D.; Ho, K. J.; Half, L. C.; Croskey, C. L.; Olsen, R. O.
Synthesis of novel electrically conducting polymers: Potential conducting Langmuir-Blodgett films and conducting polymers on defined surfaces
Based on previous results involving thiophene derived electrically conducting polymers in which it was shown that thiophene, 3-substituted thiophenes, furans, and certain oligomers of these compounds showed electrical conductivity after polymerization. The conductivity was in the order of up to 500 S/cm. In addition, these polymers showed conductivity without being doped and most of all they were practically inert toward ambient conditions. They even could be used in aqueous media. With these findings as a guide, a number of 3-long-chain-substituted thiophenes and 1-substituted-3-long-chain substituted pyrrols were synthesized as monomers for potential polymeric electrically conducting Langmuir-Blodgett films.
Zimmer, Hans
High pressure electrical conductivity studies of acid doped polybenzimidazole
Electrical conductivity studies of acid doped poplybenzimidazole (PBI) and 85% phosphoric acid have been carried out. The PBI contained about 600mol% of 85% phosphoric acid and the electrical conductivity was deduced from complex impedance studies which were made at frequencies from 10 to 107Hz. Measurements were made at pressures up to 0.25 GPa and temperatures of about 25, 50 and
J. J Fontanella; M. C Wintersgill; J. S Wainright; R. F Savinell; M Litt
Evaluation of contact resistance for isotropic electrically conductive adhesives
Electrically conductive adhesives are discussed and studied with ever-increasing interest as an alternative to solder interconnection in microelectronics circuit packaging. A similar level of scrutiny that is used to evaluate contact resistance performance for interconnections made with solder and separable connectors is necessary for electrically conductive adhesives. Experience with solder interconnection and separable connectors shows low initial contact resistance of
Michael A. Gaynes; Russell H. Lewis; R. F. Saraf; Judith M. Roldan
Electrical conductivity measurements of nanofluids and development of new correlations.
In this study the electrical conductivity of aluminum oxide (Al2O3), silicon dioxide (SiO2) and zinc oxide (ZnO) nanoparticles dispersed in propylene glycol and water mixture were measured in the temperature range of 0 degrees C to 90 degrees C. The volumetric concentration of nanoparticles in these fluids ranged from 0 to 10% for different nanofluids. The particle sizes considered were from 20 nm to 70 nm. The electrical conductivity measuring apparatus and the measurement procedure were validated by measuring the electrical conductivity of a calibration fluid, whose properties are known accurately. The measured electrical conductivity values agreed within +/- 1% with the published data reported by the manufacturer. Following the validation, the electrical conductivities of different nanofluids were measured. The measurements showed that electrical conductivity of nanofluids increased with an increase in temperature and also with an increase in particle volumetric concentration. For the same nanofluid at a fixed volumetric concentration, the electrical conductivity was found to be higher for smaller particle sizes. From the experimental data, empirical models were developed for three nanofluids to express the electrical conductivity as functions of temperature, volumetric concentration and the size of the nanoparticles. PMID:22103081
Konakanchi, Hanumantharao; Vajjha, Ravikanth; Misra, Debasmita; Das, Debendra
Structural and Electrical Study of Conducting Polymers
Pure and oxalic acid doped conducting polymers (polyaniline and polypyrrole) were chemically synthesized using ammonium persulfate (APS) as an oxidant. These samples were characterized through Scanning Electron Microscopy (SEM), which provides information about the surface topography of polymers. I-V characteristics have been recorded at room temperature as well as in the temperature range from 313 K to 463 K. So obtained characteristic curves were found to be linear. Temperature dependence of conductivity suggests a semiconducting nature in polyaniline samples with increase in temperature, whereas oxalic acid doped polypyrrole sample suggests a transition from semiconducting to metallic nature with the increase of temperature.
Shaktawat, Vinodini; Dixit, Manasvi; Saxena, N. S.; Sharma, Kananbala
Electrical conductivity anisotropy in alkali feldspar at high pressure
Magnetotelluric studies have shown that electrical conductivity in the crust is highly anisotropic. Knowledge of the anisotropy of crustal minerals, such as feldspar and quartz, is essential to interpreting this phenomenon. Feldspars are the most abundant minerals in the earth's crust, and thus, the electrical conductivity of feldspars may help in understanding of the bulk conductivity of the crust. The electrical conductivities of single-crystal and polycrystalline feldspars have been previously studied, but few studies have considered the electrical conductivity of single alkali feldspars. In this study, we investigated the electrical conductivity of alkali feldspars at different orientations under high temperatures and pressures through several heating and cooling cycles. The starting materials were natural alkali feldspar minerals collected from Beijing, China. The samples contain 65 % potassium-rich host (microcline) and 30 % sodium-rich exsolution lamellae (albite), as well as ~5% minor phases. The impedance spectrum measurements were carried out in a high-pressure cubic-anvil apparatus.All complex impedance measurements were performed at 1 GPa using a Solartron 1260 impedance phase analyzer. Impedance arcs representing crystal conductivity occur in the frequency range of ~10^3-10^6 Hz. The electrical conductivity of alkali feldspars increased with increasing temperature. The highest electrical conductivities in alkali feldspars were measured along the a-axis, with somewhat lower conductivities along the b-axis and the lowest conductivities along the c-axis, suggesting minor anisotropy. The activation enthalpies ranged from 100 to 110 kJ/mol. The electrical conductivity of alkali feldspar is mildly anisotropic, with an anisotropy factor of approximately 2. The minor anisotropy in conductivity for alkali feldspar may not account for the anisotropy of the crust. This work is supported by the Important Field Knowledge Innovation Program (KZCX2-YW-QN608), National Natural Science Foundation of China (No. 40774036)
Wang, D.; Yu, Y.
Aircraft observations of electrical conductivity in warm clouds
Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, India. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and corona discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other investigators. Classical static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivity measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mechanism of vertical mixing in clouds lends support to convective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.
Raj, P. Ernest; Devara, P. C. S.; Selvam, A. M.; Murty, A. S. R.
Variable anisotropic brain electrical conductivities in epileptogenic foci.
Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n = 15) were measured using the 4-electrode technique and compared with clinical variables. Mean (+/-SD) electrical conductivities were 0.10 +/- 0.01 S/m, and varied by 243% from patient to patient. Perpendicular and parallel conductivities differed by 45%, and the larger values were perpendicular to the pial surface in 47% and parallel in 40% of patients. A perpendicular principal axis was associated with normal, while isotropy and parallel principal axes were linked with epileptogenic lesions by MRI. Electrical conductivities were decreased in patients with cortical dysplasia compared with non-dysplasia etiologies. The electrical conductivity values of freshly excised human brain tissues were approximately 30% of assumed values, varied by over 200% from patient to patient, and had erratic anisotropic and isotropic shapes if the MRI showed a lesion. Understanding brain electrical conductivity and ways to non-invasively measure them are probably necessary to enhance the ability to localize EEG sources from epilepsy surgery patients. PMID:20440549
Akhtari, M; Mandelkern, M; Bui, D; Salamon, N; Vinters, H V; Mathern, G W
Synthesis of cross-linked electrically conductive polymers
We report attempts to improve the intrinsic conductivity of electrically conductive polymers by crosslinking them with conjugated linkages, thus providing physical pathways for charge transport. Conductive polymers were crosslinked by palladium catalyzed cross-coupling reactions of the type developed by Suzuki and Stille. Crosslinked polymers included derivatives of poly(thiophene), and poly(?-thiophenediyl)benzylidene. Changes in the physical and electrical properties are reported.
K. Davidson; A. M. Ponsonby
Calibration-Free Electrical Conductivity Measurements for Highly Conductive Slags;Metallurgical Transactions B.
This research involves the measurement of the electrical conductivity (k) for the ESR (electroslag remelting) slag (60 wt.% CaF2 - 20 wt.% CaO - 20 wt.% Al2O3) used in the decontamination of radioactive stainless steel. The electrical conductivity is meas...
Macdonald Gao Pal Van Den Avyle Melgaard
Atrioventricular conduction in mammalian species: Hemodynamic and electrical scaling
OBJECTIVES The purpose of this study was to investigate scaling of the duration of late diastolic left ventricular (LV) filling in relation to AV conduction time (delay) (PR interval on the ECG) in mammals.\\u000aBACKGROUND From mouse to whale, AV delay increases 10-fold, whereas body mass increases one million-fold. The apparent \\
Frits L. Meijler; Jacques Billette; Jos� Jalife; Marja J. L. Kik; Johan H. C. Reiber; Arnold A. Stokhof; Jos J. M. Westenberg; Claes Wassenaar; Jan Strackee
Electrical impedance spectroscopy for electro-mechanical characterization of conductive fabrics.
When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493
Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun
Band Structure and Electrical Conductivity in Semiconductors
In this experiment, we will, 1. understand how conductivity in semiconductors depends on carrier concentration and mobility, and how these depend on temperature, 2. distinguish between intrinsic and extrinsic temperature regimes and identify the applicable temperature range from an examination of measured data, 3. appreciate and utilize the advantages of the four-probe resistance measurement technique, 4. calculate the energy band gap for doped Si and pure Ge, 5. calculate the temperature dependent coefficient of the majority carriers, 6. through experimental realizations, appreciate a physical understanding of the band gap structure of semiconductors.
Khalid, Asma; Anwar, Muhammad S.; Zia, Wasif
Ultraviolet-laser-induced permanent electrical conductivity in polyimide
When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 O cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The
T. Feurer; R. Sauerbrey; M. C. Smayling; B. J. Story
When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 Omega cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The
Electrical Conductivity in a Mixed-Species Biofilm
Geobacter sulfurreducens can form electrically conductive biofilms, but the potential for conductivity through mixed-species biofilms has not been examined. A current-producing biofilm grown from a wastewater sludge inoculum was highly conductive with low charge transfer resistance even though microorganisms other than Geobacteraceae accounted for nearly half the microbial community.
Lau, Joanne; Nevin, Kelly P.; Franks, Ashley E.; Tuominen, Mark T.; Lovley, Derek R.
Thermal and Electrical Conductivity Probe (TECP) for Phoenix
The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity, and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring
Aaron P. Zent; Michael H. Hecht; Doug R. Cobos; Gaylon S. Campbell; Colin S. Campbell; Greg Cardell; Marc C. Foote; Stephen E. Wood; Manish Mehta
Electric Pulp Tester Conductance Through Various Interface Media
A conducting media is necessary when using an electric pulp tester (EPT). The objective of this study was to observe differences in conductance through various media. We hypothesized that variations in current conductance through different media exist. The pulp chamber of a freshly extracted premolar was exposed, and the cathode of a voltmeter was inserted into the pulpal tissue. The
Andr� K. Mickel; Kimberly A. D. Lindquist; Sami Chogle; Jefferson J. Jones; Francis Curd
Spatial variability of bulk soil electrical conductivity in a Malaysian paddy field: key to soil management
On-the-go EC sensor is a useful tool in mapping the apparent soil electrical conductivity (ECa) to identify areas of contrasting soil properties. In non-saline soils, ECa is a substitute measurement for soil texture. It is directly related to both water holding capacity and cation exchange capacity\\u000a (CEC), which are key ingredients of productivity. This sensor measures the ECa across a
W. Aimrun; M. S. M. Amin; Desa Ahmad; M. M. Hanafi; C. S. Chan
Electrical Conductance, Density, and Viscosity in Mixtures of Alkali-Metal Halides and Glycerol
This paper presents the results of density, viscosity, and electrical conductivity measurements for glycerol solutions of some alkali-metal halides at 25�C. The apparent and partial molar volumes (VF and V1) in mixtures of KCl, NaCl, KBr, KI, and glycerol were calculated from the density data. The Debye�H�ckel limiting law was assumed to be valid at low concentrations, and values of
A. Hammadi
Surface electrical conductivity of single crystal spinel in cesium vapor. Final report
The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.
Agnew, P.; Ing, J.L.
Assembly for electrical conductivity measurements in the piston cylinder device
An assembly apparatus for measurement of electrical conductivity or other properties of a sample in a piston cylinder device wherein pressure and heat are applied to the sample by the piston cylinder device. The assembly apparatus includes a body, a first electrode in the body, the first electrode operatively connected to the sample, a first electrical conductor connected to the first electrode, a washer constructed of a hard conducting material, the washer surrounding the first electrical conductor in the body, a second electrode in the body, the second electrode operatively connected to the sample, and a second electrical conductor connected to the second electrode.
Watson, Heather Christine (Dublin, CA); Roberts, Jeffrey James (Livermore, CA)
Thermal and electrical conductivities of silver-indium-tin alloys
The variations of thermal conductivity with temperature for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) were measured using a radial heat flow apparatus. From the graphs of thermal conductivity versus temperature, the thermal conductivities of solid phases at their melting temperature for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) were found to be 46.9�3.3, 53.8�3.8, 61.2�4.3, 65.1�4.6 and 68.1�4.8 W/Km, respectively. The variations of electrical conductivity of solid phases versus temperature for the same alloys were determined from the Wiedemann-Franz equation using the measured values of thermal conductivity. From the graphs of electrical conductivity versus temperature, the electrical conductivities of the solid phases at their melting temperatures for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) alloys were obtained to be 0.036, 0.043, 0.045, 0.046 and 0.053 (�108/?m), respectively. Dependencies of the thermal and electrical conductivities on the composition of Sn in the Ag-Sn-In alloys were also investigated. According to present experimental results, the thermal and electrical conductivities for the Ag-[x] wt% Sn-20 wt% In alloys linearly decrease with increasing the temperature and increase with increasing the composition of Sn.
Aks�z, Sezen; Mara?l?, Necmettin
Using electrical impedance tomography to map subsurface hydraulic conductivity
The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.
Berryman, James G. (Danville, CA); Daily, William D. (Livermore, CA); Ramirez, Abelardo L. (Pleasanton, CA); Roberts, Jeffery J. (Livermore, CA)
Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.
Integrated Teaching And Learning Program
Microstructure, electrical conductivity, and piezoelectric properties of bismuth titanate
A study was conducted on the effects of microstructure, atmosphere, and several dopants on the electrical conductivity of bismuth titanate (Bi�Ti�O��, BIT). Increased grain size increased the conductivity in undoped BIT as did acceptor dopants that substituted for either Bi (Ca and Sr) or Ti(Fe). A donor dopant (Nb) decreased the conductivity in BIT by as much as 3 orders
Holly S. Shulman; Martin Testorf; Dragan Damjanovic; Nava Setter
Electrical conduction and breakdown properties of silicon nitride films
The electrical conduction properties of ion-plated silicon nitride films in the form of aluminium-silicon nitride-aluminium structures have been studied in the temperature range 300 K to 470 K. The results obtained in the d.c. Conduction studies have been explained on the basis of the Poole-Frenkel conduction mechanism. The a.c. conduction studies in the frequency range 500 Hz to 30 kHz
D. Mangalaraj; M. Radhakrishnan; C. Balasubramanian
Estimating Plant-Available Water Capacity for Claypan Landscapes Using Apparent Electrical Conductivity
direct relationship between ECa?1 and profi le PAW (PAW1.2) was signifi cant, with regression r2 values of 0.67 and 0.87 and RMSEs of 30 and 20 mm for Fields 1 and 2, respectively. The RMSEs for two-layer-estimated PAW1.2 were 14 and 16 mm for Fields 1 and 2, respectively, or 7.6 and 8.6% of the respective mean measured PAW1.2. With
Pingping Jiang; Stephen H. Anderson; Newell R. Kitchen; Kenneth A. Sudduth; E. John Sadler
Soybean Root Distribution Related to Claypan Soil Properties and Apparent Soil Electrical Conductivity
Soybean (Glycine max (L.) Merr.) yield in claypan soils varies systematically with soil properties and landscape position. This is likely caused by soil interactions with soybean roots. Field obser- vations of soybean root distribution are needed to reveal its effect on yield variability. This study examined profi le distributions of soybean root length density (RLD) and average root diameter (ARD)
D. Brenton Myers; Newell R. Kitchen; Kenneth A. Sudduth; Robert E. Sharp; Randall J. Miles
�SIGMELTS�: A web portal for electrical conductivity calculations in geosciences
Electrical conductivity measurements in the laboratory are critical for interpreting geoelectric and magnetotelluric profiles of the Earth's crust and mantle. In order to facilitate access to the current database on electrical conductivity of geomaterials, we have developed a freely available web application (SIGMELTS) dedicated to the calculation of electrical properties. Based on a compilation of previous studies, SIGMELTS computes the electrical conductivity of silicate melts, carbonatites, minerals, fluids, and mantle materials as a function of different parameters, such as composition, temperature, pressure, water content, and oxygen fugacity. Calculations on two-phase mixtures are also implemented using existing mixing models for different geometries. An illustration of the use of SIGMELTS is provided, in which calculations are applied to the subduction zone-related volcanic zone in the Central Andes. Along with petrological considerations, field and laboratory electrical data allow discrimination between the different hypotheses regarding the formation and rise from depth of melts and fluids and quantification of their storage conditions.
Pommier, A.; Le-Trong, E.
Improving electrical conductivity in polycarbonate nanocomposites using highly conductive PEDOT/PSS coated MWCNTs.
We describe a strategy to design highly electrically conductive polycarbonate nanocomposites by using multiwalled carbon nanotubes (MWCNTs) coated with a thin layer of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate), a conductive polymer. We found that this coating method improves the electrical properties of the nanocomposites in two ways. First, the coating becomes the main electrical conductive path. Second, the coating promotes the formation of a percolation network at a low filler concentration (0.3 wt %). To tailor the electrical properties of the conductive polymer coating, we used a polar solvent ethylene glycol, and we can tune the final properties of the nanocomposite by controlling the concentrations of the elementary constituents or the intrinsic properties of the conductive polymer coating. This very flexible technique allows for tailoring the properties of the final product. PMID:23758203
Zhou, Jian; Lubineau, Gilles
Apparent cooperativity of amino acid transport in Halobacterium halobium - Effect of electrical potential
Active serine accumulation in cell envelope vesicles from Halobacterium halobium proceeds by co-transport with Na(+) and can be induced by either transmembrane electrical potential or transmembrane Na(+) concentration difference. It was shown earlier that in the former case the initial transport rate is a fourth-power function of the magnitude of the electrochemical potential difference of sodium ions, and in the latter, a second-power function. A possible interpretation of this finding is cooperativity of sodium-transporting sites in the transport carrier. When both kinds of driving force are imposed simultaneously on the vesicles, fourth-power dependence on the total potential difference of sodium ions is obtained, suggesting that the transport carrier is regulated by the electrical potential. Heat treatment of the vesicles at 48 C partially inactivates transport and abolishes this effect of the electrical potential.
Lanyi, J. K.
Electrical conductivity of rocks at high pressures and temperatures
The results of studies of the electrical conductivity in the most widely distributed types of igneous rocks, at temperatures of up to 1200 C, at atmospheric pressure, and also at temperatures of up to 700 C and at pressures of up to 20,000 kg/sq cm are described. The figures of electrical conductivity, of activaation energy and of the preexponential coefficient are presented and the dependence of these parameters on the petrochemical parameters of the rocks are reviewed. The possible electrical conductivities for the depository, granite and basalt layers of the Earth's crust and of the upper mantle are presented, as well as the electrical conductivity distribution to the depth of 200 to 240 km for different geological structures.
Parkhomenko, E. I.; Bondarenko, A. T.
Proton Abstraction as a Route to Electrically Conductive Polymers.
Proton abstraction with strong base from relatively acidic coubly allylic and/or benzylic methylene moieties spaced along an otherwise all-conjugated polymer chain has been demonstrated as an alternate route to electrically conductive polymers. Poly(p-phe...
B. Gordon L. F. Hancock
Electrical conductivity of rocks in the heating and cooling cycle
Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.
Marcela Lastovickov�; F. Jan�k
Corrosion-Protective Coatings from Electrically Conducting Polymers.
In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high ac...
K. G. Thompson C. J. Bryan B. C. Benicewicz D. A. Wrobleski
Corrosion-protective coatings from electrically conducting polymers.
In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch...
Measurement of Electrical Conductivity for a Biomass Fire
A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K.
Mphale, Kgakgamatso; Heron, Mal
Temperature-dependent electrical conductivity of soda-lime glass
The objective of this educational exercise was to demonstrate the difference between the electrical conductivity of metals and ceramics. A list of the equipment and supplies and the procedure for the experiment are presented.
Bunnell, L. Roy; Vertrees, T. H.
Metallization and electrical conductivity of hydrogen in Jupiter
Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter`s magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. 30 refs., 3 figs.
Nellis, W.J.; Weir, S.T.; Mitchell, A.C. [Lawrence Livermore National Laboratory, CA (United States)
Metallization and electrical conductivity of hydrogen in Jupiter.
Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072
Nellis, W J; Weir, S T; Mitchell, A C
Electrically Conductive Resinous Bond and Method of Manufacture.
A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages ...
T. M. Snowden B. J. Wells
Electrical Circuit Analogues of Thermal Conduction and Diffusion
After briefly reviewing equations of conduction and diffusion, and voltage and charge in electrical circuits, a simple experiment is given that allows students practical experience in a theoretical realm of physics. (MDR)
Tomlin, D. H.; Fullarton, G. K.
Electrical Conductivities of Liquid Egg Products and Fruit Juices Exposed to High Pulsed Electric Fields
Electrical conductivity can be used to monitor important changes in a food product during pulsed electric field (PEF) processing. Electrical conductivities of selected fruit juices (namely apple, orange, and pineapple juices) and liquid egg products (namely whole egg, yolk, and egg white) were determined online during a PEF treatment. The property was measured at broad processing temperatures ranging from 5
Malek Amiali; Michael O. Ngadi; Vijaya G. S. Raghavan; D. H. Nguyen
Effect of volatile components on electrical conductivity of mantle materials
Recent laboratory electrical conductivity measurements of the main mantle constituent minerals have refined our understanding of the effect of water, carbon and iron contents on electrical conductivity. Especially effect of water on electrical conductivity of nominally anhydrous minerals has been substantially investigated. These studies suggested that proton conduction in nominally anhydrous minerals can elevate the electrical conductivity compared to the dry condition. However, if the water exists along grain boundaries, the proton conduction is completely masked by contribution of grain boundary water to the bulk conductivity. This phenomena was confirmed by the conductivity measurement at high temperatures (> 1000 K), leading to higher conductivity due to the grain boundary water generated by dehydration of sample. For nominally anhydrous minerals containing water in its crystal structure, water must partition between crystal and fluid. Thus when certain amount of grain boundary water exists, we cannot directly estimate water content in minerals based on a comparison between laboratory and geophysical data. Volatile components such as water and carbon dioxide in mantle materials can largely reduce the melting temperature. For example, solidus temperature of carbonate-bearing peridotite is below the normal mantle geotherm up to the 330 km depth. Solidus of water-saturated peridotite is low enough to generate partial melting through the upper mantle and the transition zone. Electrical conductivity of partial molten carbonate peridotite showed that the conductivity of the carbonate melt is nearly one order of magnitude higher than those of silicate melt in peridotite. In addition, electrical conductivity of hydrous basalt also show enhancement of the conductivity. Considering the effect of water and carbon on the bulk conductivity, the conductivity of volatile-bearing peridotites could be significantly higher than that of the volatile-free peridotites. Because melts contaning volatile components have smaller temperature dependence (low activation energy), the high conductivity can be accomplished even if temperature is largely lower than the normal mantle geotherm. Therefore, the electrical conductivity of the Earth's mantle would be controlled by the trace amount of volatile components.
Yoshino, T.; Katsura, T.; Shimojuku, A.
Estimating Soil Salinity from Saturated Soil-Paste Electrical Conductivity
A method is presented for estimating the electrical conductivity of the saturated soil-paste extract (EC,) from measurement of the electrical conductivity of the saturated soil-paste (EC,) and esti- mated saturated soil-paste water content (SP), for purposes of soil salinity appraisal. The method is suitable for both field and labo- ratory applications. Empirical relations are provided to estimate val- ues of
J. D. Rhoades; Nahid A. Manteghi; P. J. Shouse; W. J. Alves
Manipulating connectivity and electrical conductivity in metallic nanowire networks.
Connectivity in metallic nanowire networks with resistive junctions is manipulated by applying an electric field to create materials with tunable electrical conductivity. In situ electron microscope and electrical measurements visualize the activation and evolution of connectivity within these networks. Modeling nanowire networks, having a distribution of junction breakdown voltages, reveals universal scaling behavior applicable to all network materials. We demonstrate how local connectivity within these networks can be programmed and discuss material and device applications. PMID:23062152
Nirmalraj, Peter N; Bellew, Allen T; Bell, Alan P; Fairfield, Jessamyn A; McCarthy, Eoin K; O'Kelly, Curtis; Pereira, Luiz F C; Sorel, Sophie; Morosan, Diana; Coleman, Jonathan N; Ferreira, Mauro S; Boland, John J
Electrical Conductivity of Hydrous Single Crystal San Carlos Olivine
The electrical conductivity of anhydrous San Carlos olivine is too low to explain the observed electrical conductivity of Earth's upper mantle. Although the solubility of hydrogen in olivine is relatively low at mantle P and T conditions, it has been estimated that even at concentrations of less than 1000 ppm, electrical conductivity is enhanced by as much as a factor of one hundred, based on a conduction mechanism involving hydrogen diffusion (Karato, Nature 347, 272-273, 1990). In this study we have measured the electrical conductivity of hydrated San Carlos olivine single crystals, oriented along (100), (010) and (001). SCO single crystals were first oriented, machined into 2 mm diameter cylinders, and then sandwiched between layers of a talc+brucite mix in sealed Pt capsules for hydration runs at pressures up to 8 GPa and 1200�C in a multianvil apparatus. Recovered samples were then cut into wafers ranging from 0.2 to 0.6 mm in thickness for subsequent complex impedance measurements to determine electrical conductivity, also carried out at high pressure. For the electrical measurements, temperatures were limited to about 700�C in order to minimize loss of water from the sample. FTIR spectroscopy was used to determine water content of samples both before and after the electrical measurements. Preliminary results indicate that at concentrations of a few hundred ppm water, conductivities are several orders of magnitude higher than for dry olivine. Activation energies decrease with increasing water content, indicating that extrapolation of conductivities to higher temperatures leads to a smaller overall effect. However, based on these results, at upper mantle conditions, the presence of minor amounts of hydrogen in olivine is sufficient to bridge the gap between the conductivity of dry olivine and that of the mantle.
Poe, B.; Romano, C.; Nestola, F.; Rubie, D.
When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 ? cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The conduction mechanism is phonon-assisted variable range hopping, evident from the observed temperature and electric field dependence of the resistivity at low conductivities. The laser-induced conductivity depends on the ambient atmosphere during irradiation. Transmission spectroscopy in the visible region and infrared Fourier transform spectroscopy have been used to characterize the material. A thermal mechanism is proposed for the formation of conducting polyimide, by excimer-laser irradiation.
Feurer, T.; Sauerbrey, R.; Smayling, M. C.; Story, B. J.
Electrical conductivity of silver bismuth borate tellurite glasses
The AC electrical conductivity of (Ag 2O) x (Bi 2O 3) 30 (B 2O 3) 60-x (TeO 2) 10 glass ( x=0, 2, 4, 5, 10, 15 and 20) were measured at different temperatures and frequencies. The results obtained indicated that glasses containing silver<5 mol% have values nearly approximately equal to AC electrical conductivity. A slight decrease was observed with increasing Ag 2O concentration up to 4 mol%. However, the AC electrical conductivity values increase with increasing silver content, i.e. ?5 mol%. The AC electrical conductivity values, increased with increasing frequency and follow the power law, ?AC= A?s. The frequency exponent s was found to be dependent on frequency and temperature. The s values tended to increase to unity as the temperature decreased. Such results suggest that the correlated barrier-hopping (CBH) model is appropriate for explaining the AC electrical conductivity in these glasses. A pronounced increase in the dielectric loss values was observed with increasing silver content. These reflect the effect of Ag + ions charge carriers on the electrical conductivity of such glasses.
Ali, A. A.; Shaaban, M. H.
Electrically conductive nanocomposites made from cellulose nanofibrils and polyaniline.
Electrically conductive nanocomposites from cellulose nanofibrils (CNF) were successfully produced by in situ polymerization of aniline onto CNF, and studied by open circuit potential (Voc), four probe direct current (dc) electrical conductivity, ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). The oxidative polymerization of aniline using ammonium peroxydisulfate in hydrochloric acid aqueous solutions was realized by the addition of nanofibrils leading to an aqueous suspension of CNF coated with polyaniline (PANI). This procedure lead to stable, green suspensions of CNF coated with PANI in the emeraldine oxidation state as demonstrated by Voc and UV-Vis analyses. Electrically conductive films of this cellulose nanocomposite could be cast from aqueous solutions with conductivity close to the conducting polymer, yet with the potential for more useful flexible films. PMID:19452949
Mattoso, L H C; Medeiros, E S; Baker, D A; Avloni, J; Wood, D F; Orts, W J
Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze
Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, there is significant variation among different phosphor bronze formulations. The James Webb Space Telescope (JWST) will use several phosphor bronze wire harnesses containing a specific formulation (CDA 510, annealed temper). The heat conducted into the JWST instrument stage is dominated by these harnesses, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to just keep the instruments at their operating temperature with limited cooling margin, it is important to know the thermal conductivity of the actual alloy being used. We describe an experiment which measured the electrical and thermal conductivity of this material between 4 and 295 Kelvin.
Tuttle, James E.; Canavan, Edgar; DiPirro, Michael
Electrical-Impedance Tomography for Opaque Multiphase Flows in Metallic (Electrically-Conducting) Vessels.
A novel electrical-impedance tomography (EIT) diagnostic system, including hardware and software, has been developed and used to quantitatively measure material distributions in multiphase flows within electrically-conducting (i.e., industrially relevant ...
S. G. Liter J. R. Torczynski K. A. Shollenberger S. L. Ceccio
Extended thermodynamics of a relativistic plasma with finite electric conductivity
A system of equations for relativistic m.h.d, with finite electric conductivity and no heat flux is proposed, starting from the properties of the systems of conservation laws compatible with a supplementary balance law (entropy balance) with convex density ( symmetric-hyperbolic systems). The electric current density is treated as a new field variable which contributes to non equilibrium entropy density ( extended thermodynamics). The result is a theory in which only one new constitutive function, representing entropy increment respect to equilibrium, is necessary to characterize the properties of the medium related to electric conductivity.
Strumia, A.
Scaling of the electrical conductivity of granular media
We derive the scaling properties of the dependence of the macroscopic electrical conductivity of granular media (e.g., sands) with a surface mechanism of electrical conduction on the grain size, when the medium is subjected to a given mechanical stress. In order to eliminate the influence of the inter-grain junction capacity, the direct electrical current is considered. We determine the applicability restrictions on the theory which disregards the ultimate crushing compression strength, adhesion, and the effect of charge carrier tunneling at grain junctions beyond the contact surface area. Solutions for several regular packings of grains are obtained as well.
Goldobin, D. S.; Krauzin, P. V.
Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...
Distinguishability of Conductivities by Electric Current Computed Tomography
We give criteria for the distinguishability of two different conductivity distributions inside a body by electric current computed tomography (ECCT) systems with a specified precision. It is shown in a special case how these criteria can be used to determine the measurement precision needed to distinguish between two different conductivity distributions. It is also shown how to select the patterns
David Isaacson
Conductance imaging AFM and electrical properties of carbon nanotubes
This thesis reports the development of a new method for measuring electrical of nanoscale objects, called conductance imaging atomic force microscopy (CIAFM), and reports the results of measurements performed on carbon nanotube networks and nanotube junctions. We introduce CIAFM, a method that combines atomic force microscopy and local conductance measurements. The method is implemented by using a tuning fork as
Michael Stadermann
Liquid Additives to Improve Conductivity in Electric Contacts
Electric contacts generally have high contact resistances because of the relatively small number of conducting contact spots and correspondingly small area through which to transfer current. Liquid metals have been used in the past to provide complete coverage in the contact region but generally require protective atmospheres to prevent corrosion of the liquid metal. Adding an atmospherically stable, non-consumable, conductive
W. A. Lynch; N. A. Sondergaard
Electrical conduction of XLPE with vacuum degassed semiconductive electrodes
It has been found that the electrical conduction characteristics of polyethylene are influenced strongly by the vacuum treatment of cross-linked polyethylene (XLPE) and\\/or semiconductive electrodes. The major changes due to the vacuum treatment of these materials are the suppression in the rate of change of current density at some field range and the change of conduction mechanisms from the SCLC
K. S. Suh; C. R. Lee; Min-Koo Han
Electrical conductivity of amphibole-bearing rocks: influence of dehydration
We investigated the electrical conductivity of amphibole-bearing rocks under the conditions of the middle to lower crust. Alternating current measurements were performed in the frequency range of 10-106 Hz in a cubic-anvil high-pressure apparatus at 0.5-1.0 GPa and 373-873 K. The electrical conductivity of these rocks is weakly temperature dependent below ~800 K with modest anisotropy and relatively low conductivity (~5 � 10-3 S/m at ~750 K with the activation enthalpy of 64-67 kJ/mol). However, the electrical conductivity starts to increase with temperature more rapidly above ~800 K (activation enthalpy of 320-380 kJ/mol). The infrared spectroscopy observations indicate that dehydration occurs in this high temperature regime. The observed high activation enthalpy and the reproducibility suggest that the enhanced conductivity is not due to the direct effect caused by the generation of conductive fluids. Dehydration of amphibole is associated with the oxidation of iron (from ferrous to ferric), and we suggest that the increased conductivity associated with dehydration is caused by oxidation. This effect may explain high electrical conductivity observed in some regions of the continental crust.
Wang, Duojun; Guo, Yingxing; Yu, Yingjie; Karato, Shun-ichiro
Electrically conductive resinous bond and method of manufacture
A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40.degree. to 365.degree. C. to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.
Snowden, Jr., Thomas M. (P.O. Box 4231, Clearwater, FL 33518); Wells, Barbara J. (865 N. Village Dr., Apt. 101B, St. Petersburg, FL 33702)
Electric field enhanced conductivity in strongly coupled dense metal plasma
Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field ({approx}6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.
Stephens, J.; Neuber, A. [Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)
A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40 to 365/sup 0/C to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.
Snowden, T.M. Jr.; Wells, B.J.
Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field (~6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.
Stephens, J.; Neuber, A.
A Simulation Study of Electrical Fiber Composite Conductivity
Percolation concept has been used in this study to estimate the amount of conductive fibers embedded in polymeric matrix, necessary to establish conduction in this kind of composites. The resistance of composite materials is calculated by simulating composite samples with different size, containing conductive fibers with various lengths Calculation is based on detecting conductive pathways through the insulating matrix, these pathways are assumed to be resistances in parallel. Electrical resistance curves showed a percolative behavior of the samples versus volume fraction of filler. Lower conduction thresholds are obtained for fiber aspect ratio of 20 and sample size of 100. The electrical resistivity and the conduction thresholds of the carbon fiber reinforced polycarbonate composites have been characterized. Simulation results are in good agreement with an experimental result found in the literature.
Mezdour, D.; Sahli, S.
Effects of contact resistance on electrical conductivity measurements of SiC-based materials
A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ?973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ?1000 ? cm2 at RT, decreasing continuously to ?1�10 ? cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ?0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.
Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.
Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials
A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700�C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 ?-cm2 at RT, decreasing continuously to ~1-10 ?-cm2 at 700�C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.
An Expansion Theorem for the Elecric Conductivity of Metals. I Electric Conductivity for Longitudinal Electric Field
A systematic diagram representation in a composite 4-dimensional space is developed for Kubo's response function which describes the electric response currents of metals for longitudinal electric fields. Proper diagrams are defined as the Feynman type linked diagrams which cannot be decomposed into simpler diagrams connected only by one Coulomb line. The greatest care is exercised with reference to the fact
Takeo Izuyama
Numerical study on electrical conductivity of spin-fermion models
The DC electrical conductivity is studied numerically in finite-size spin-fermion models with antiferromagnetic couplings between localized spins by a direct numerical estimation of the Kubo formula. In contrast with an ordinary magnetoresistance, in a system where the localized spins form an antiferromagnetically coupled two-leg ladder, conductivity shows an anomalous non-monotonic field dependence. It is attributed to a spin configuration where two spins on the ladder rung dimerize into a spin singlet. In addition, we study conductivity of a square lattice and observe the direction dependence of conductivity. We obtained remarkable and qualitative differences in behavior of conductivity depending on the direction of current.
Ogasahara, Akira; Kusakabe, Koichi
The electrical conductivity of the oceanic upper mantle
SUMMARY Previous inversions of sea-floor magnetotelluric (MT) sounding data have predicted upper mantle electrical conductivities which are more than an order of magnitude higher than laboratory measurements of the conductivity of olivine would suggest, and controlled source-field electromagnetic (CSEM) soundings require a lithos- pheric mantle conductivity of 3 x lop5 Sm-', which is so low that the electromag- netic (EM)
Graham Heinson; Steven Constable
Detection of temperature distribution via recovering electrical conductivity in MREIT
In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 �C.
In Oh, Tong; Kim, Hyung Joong; Jeong, Woo Chul; Chauhan, Munish; In Kwon, Oh; Woo, Eung Je
Detection of temperature distribution via recovering electrical conductivity in MREIT.
In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 �C. PMID:23552880
Oh, Tong In; Kim, Hyung Joong; Jeong, Woo Chul; Chauhan, Munish; Kwon, Oh In; Woo, Eung Je
GLOBE Videos: Hydrology Protocols - Electrical Conductivity (9:20 min)
The video is a procedural guide to sampling electrical conductivity measurements in water bodies using standardized GLOBE protocols. It provides a step-by-step explanation of the field procedure and features students conducting the investigation and asking questions about measuring electrical conductivity and what these measurements mean with respect to water impurities and dissolved solids. The resource includes a video, transcript, and is supported by the Electrical Conductivity Protocol in the GLOBE Teacher's Guide. This is one of seven videos on hydrology in the 24-part instructional video series describing scientific protocols used by GLOBE (Global Learning and Observation to Benefit the Environment) a worldwide, hands-on, K-12 school-based science education program.
Investigation of thermal and electrical conductivity of graphene based nanofluids
We report for the first time, the synthesis of highly stable exfoliated graphene based nanofluids with water and ethylene glycol as base fluids with out any surfactant and the subsequent studies on their thermal and electrical conductivities. Graphene was synthesized by thermal exfoliation of graphene oxide at 1050 �C in Ar atmosphere. The as-synthesized graphene has been suitably functionalized and further dispersed it in the base fluids without any surfactant. Thermal and electrical conductivities of these nanofluids were measured for varying volume fractions and at different temperatures. An enhancement in thermal conductivity by about 14% has been achieved at 25 �C with deionized water (DI) as base fluid at a very low volume fraction of 0.056% which increases to about 64% at 50 �C. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement at 25 �C for a volume fraction of 0.03%in DI water.
Baby, Tessy Theres; Ramaprabhu, S.
Temperature distribution for electrically conductive and non-conductive materials during Field Assisted Sintering (FAST)
During Field Assisted Sintering Technology (FAST) the temperature differences at two different positions were investigated using two pyrometers, an internal and an external one. Two substances, an electrically conductive (tungsten carbide) and a non-conductive material (96wt.% silicon nitride with 2wt.% alumina and yttria) were used to monitor the temperature differences between both pyrometers during heating, sintering shrinkage and dwell time
Jan R�thel; Mathias Herrmann; Wieland Beckert
Electrical Conductivity of HgTe at High Temperatures
The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.
Li, C.; Lehoczky, S. L.; Su, C.-H.; Scripa, R. N.
Electrical conductivity of fluid-bearing quartzite under lower crustal conditions
The electrical conductivity of fluid-bearing quartzite was determined as function of temperature and fluid fraction at 1 GPa in order to assess the origin of the high conductivity anomalies observed in the middle to lower crustal levels. Dihedral angles of quartz-fluid-quartz determined from recovered samples were below 60�, suggesting that fluid forms an interconnected network through the quartz aggregate. The electrical conductivity of quartzite increases with increasing temperature, which can be approximately expressed by Arrhenius equation. The apparent activation enthalpy decreases from 0.70 to 0.25 eV with increasing fluid fraction in volume from 0.00043 to 0.32. The electrical conductivity (?) of the fluid-bearing quartzite increased with fluid fraction (?) proportionally to a power law (? ? ?0.56-0.71) within the temperature range of 900-1000 K. The electrical conductivity of the aqueous fluid-bearing quartzite with the maximum fluid fraction (0.32) was found to be about three orders of magnitude higher than that of dry quartzite at 1000 K. However, its electrical conductivity was definitely lower than the geophysically observed values of high-conductivity anomalies, even if the quartzite contained large fluid fractions (0.32). The present results suggest that fluid-bearing quartzite is unable to account for the high-conductivity anomalies in terms of fluid fraction. A significant amount of other ionic species, such as Na, Cl, and Al in aqueous fluid, in addition to silica phases dissolved in fluid, is required to increase conductivity.
Shimojuku, Akira; Yoshino, Takashi; Yamazaki, Daisuke; Okudaira, Takamoto
Seasonal changes in apparent hydraulic conductance and their implications for water use of European beech ( Fagus sylvatica L.) and sessile oak [ Quercus petraea (Matt.) Liebl] in South Europe
The water status of Fagus sylvatica L. and Quercus petraea (Matt) Liebl. was analysed during a cycle of progressive natural drought in southern Europe. Predawn (?pd) and midday water potential were measured in transpiring (?leaf) and non-transpiring leaves (?xyl). Furthermore, photosynthesis (A), stomatal conductance to water vapour (gs) and sap flow (Fd) were recorded on the same dates. Apparent leaf
I. Aranda; L. Gil; J. A. Pardos
Round-Robin Measurements of the Apparent Thermal Conductivity of Two Refractory Insulation Materials, Using High-Temperature Guarded-Hot-Plate Apparatus,
The report presents the test results and analysis of round-robin measurements of apparent thermal conductivity for two kinds of refractory insulation board using high-temperature guarded-hot-plate apparatus. The round robin was carried out under the spons...
J. G. Hust D. R. Smith
Electrical conductivity of stishovite as a function of water content
The electrical conductivity of stishovite with various Al2O3 and H2O contents was measured at 12 GPa of pressure (P) and temperatures (T) up to 1900 K in a Kawai-type multi-anvil apparatus. Starting materials were pre-synthesized at 12 GPa and 1673 K from various mixtures of SiO2, Al2O3 and Al(OH)3. The synthesized stishovite aggregates contained various H2O concentrations up to 0.25 wt.%. The conductivity of relatively dry stishovite was almost constant independently of Al content, whereas the conductivity significantly increased with increasing H2O content in stishovite. All electrical conductivity data fit the formula for electrical conductivity ?=?0Cexp{-[?H0-?CW1/3]/kT}, where ?0 is the pre-exponential term, CW is the H2O concentration, ?H0 is the activation enthalpy at very low H2O concentration, and k is the Boltzmann constant. The activation enthalpy decreased from 1.22 to 0.90 eV with increasing H2O content from 0.01 to 0.22 wt.%. A nearly linear correlation of the conductivity values on the H2O content suggests that the dominant mechanism of charge transport in stishovite is proton conduction. Although electrical conductivity of hydrous stishovite is higher than that of garnet in the subducted oceanic crust, small amount of hydrous stishovite is insufficient to raise conductivity. On the other hand, hydrous stishovite can contribute to the high conductivity occasionally observed at the mantle transition zone, if the subducted Archean continental crusts with tonalite-trondhjemite-granodiorite (TTG) composition were accumulated above the 660 km seismic discontinuity.
Yoshino, Takashi; Shimojuku, Akira; Li, Danyang
Electrical conductivity of polypropylene fibers with dispersed carbon fillers
Polypropylene fibers with fillers in the form of carbon nanoparticles of four types (technical carbon, graphitized carbon nanofibers, multi-walled carbon nanotubes, and single-walled carbon nanotubes) have been synthesized. For all types of fillers, the electrical conductivity of the fibers has been measured as a function of the concentration of nanoparticles and the percolation thresholds have been determined. A correlation between the nanoparticle concentration and the electrical conductivity of the percolation cluster at the percolation threshold with the cross section, the axial ratio, and the shape of the nanoparticles dispersed in the polymer matrix has been discussed. The dependence of the electrical conductivity of the composite material with carbon nanofibers on the temperature has been measured.
Moskalyuk, O. A.; Aleshin, A. N.; Tsobkallo, E. S.; Krestinin, A. V.; Yudin, V. E.
Electrical and thermal conductivity of hybrid nanocomposites with giant strain
The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, conformable sensors, and lightweight solar cells. The optimization of electronic, thermal, and mechanical properties of conductive and extensible materials is necessary for the application of energy device. Here we demonstrate the theoretical prediction for the electrical conductivity of the nanocomposites compared with experimental results. Also, we present the giant dependence of electrical conductivity on strain and the large positive thermal expansion that can be expected for the elastomer matrix. The percolation threshold (26 vol% of Ag, average interparticle distance model) and Poisson's ratio (Vt=0.33, Vw=0.2) of nanocomposites are significant factors that can determine the electrical and thermal conductivity with giant strain. The thermal conductivity for the electronically conducting elastomeric film is relatively high at the zero-strain state, and shows a non-metallic temperature dependence consistent with phonon transport. The observed combinational property of a very small dependence of conductivity on temperature with an exponential dependence can be suitable for for the mechanical strain sensing.
Chun, Kyoung-Yong; Kim, Shi Hyeong; Shin, Min Kyoon; Spinks, Geoffrey M.; Aliev, Ali E.; Baughman, Ray H.; Kim, Seon Jeong
Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons
Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.
Iversen, I. B.; Madsen, M. M.; Dangelo, N.
Contamination from electrically conductive silicone tubing during aerosol chemical analysis
Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography-mass spectrometry (GC-MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.
Yu, Yong; Alexander, M. L.; Perraud, Veronique; Bruns, Emily; Johnson, Stan; Ezell, Michael J.; Finlayson-Pitts, Barbara J.
Yu, Yong; Liz Alexander, M.; Perraud, Veronique; Bruns, Emily A.; Johnson, Stanley N.; Ezell, Michael J.; Finlayson-Pitts, Barbara J.
Corrosion-protective coatings from electrically conducting polymers
In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.
Thompson, K.G.; Bryan, C.J. (National Aeronautics and Space Administration, Cocoa Beach, FL (United States). John F. Kennedy Space Center); Benicewicz, B.C.; Wrobleski, D.A. (Los Alamos National Lab., NM (United States))
Thompson, K.G.; Bryan, C.J. [National Aeronautics and Space Administration, Cocoa Beach, FL (United States). John F. Kennedy Space Center; Benicewicz, B.C.; Wrobleski, D.A. [Los Alamos National Lab., NM (United States)
Electrical conductivity measurements on silicate melts using the loop technique
A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.
Waff, H. S.
Electrically conductive doped block copolymer of polyacetylene and polyisoprene
An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.
Aldissi, Mahmoud (Los Alamos, NM)
In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high acid and/or elevated temperature conditions. Electrically conductive polymer coatings were developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.
Thompson, Karen Gebert; Bryan, Coleman J.; Benicewicz, Brian C.; Wrobleski, Debra A.
Rubber-like electrically conductive polymeric materials with shape memory
This paper presents a heating-responsive shape memory polymeric material, which is not only rubber-like at room temperature and above its shape recovery temperature, but also electrically conductive. This polymeric material is made of silicone, melting glue (MG), and carbon black (CB). The influence of volume fractions of MG and CB on the elasticity, electrical resistivity, and shape memory effect of the polymeric material is systematically investigated. The feasibility of Joule heating for shape recovery is experimentally demonstrated with an electric power of 31 V.
Cui, H. P.; Song, C. L.; Huang, W. M.; Wang, C. C.; Zhao, Y.
Electric conductivity of hafnium-containing fluoride-chloride melts
This paper presents the results of an investigation of the specific electric conductivity of melts of the potassium, hafnium-containing fluoride-chloride ternary reciprocal system which is of practical interest because fluoride-chloride melts containing hafnium can be used as electrolytes in the preparation of metallic hafnium. Experimental results depend largely on the purity of the salts that are used, so much attention was paid to problems of preparation and storage of the pure anhydrous salts. To obtain potassium fluorides, the authors used cp KF.2H/sub 2/O which was dried and then melted with continuous vacuum treatment. The specific electric conductivity was measured by a relative capillary method at a frequency of 50 kHz with an R-568 alternatingcurrent bridge. The lines of equal specific electric conductivity of the melts investigated at 1000/sup 0/C show that the conductivity of the melts was determined mainly by the hafnium tetrafluoride content, namely, the increase of its concentration in the melt caused a decrease of the electric-conductivity values.
Darienko, S.E.; Chervinskii, Yu.F.; Katyshev, S.F.; Nichkov, I.F.
Electrically Joining Mixed Conducting Oxides for High Temperature Applications
Mixed conducting oxides such as lanthanum strontium cobalt ferrite are currently being investigated for potential use as electrochemically active electrodes and catalytic membranes in a number of high temperature devices, including oxygen generators and solid oxide fuel cells (SOFC). However to take full advantage of the unique properties of these materials, reliable joining techniques need to be developed. What complicates joining in these applications is the requirement that the ceramic-to-metal junction be electrically conductive, so that current can either be drawn from the mixed conducting oxide, in the case of SOFC applications, or be carried to the oxide to initate ionic conduction, as required for oxygen separation and electrocatalysis. This paper outlines a new technique that is being developed to electrically join an oxide conductor to a metal current collector for high temperature electrochemical application.
Weil, K. Scott; Hardy, John S.
Electrical conductivity of albite melts at high pressures
High electrical conductivity observed from magnetotelluric/geomagnetic depth sounding is probably associated with the presence of silicate melts. We investigated electrical conductivity of albite melts, both anhydrous and hydrous with 2.0-5.4 wt% H2O, at 300-1500�C and 0.9-1.8 GPa in a piston-cylinder apparatus. Anhydrous glass was synthesized by fusing oxides and carbonates in 1-bar furnace, and hydrous glasses were prepared by fusing the mixture of glass powder and water in a TZM vessel. A glass cylinder was enclosed between a platinum rod as inner electrode and a Pt-Rh capsule as outer electrode. Platinum wires were used to connect both electrodes to a Solartron 1260 impedance analyzer for conductivity measurements at 3M to 3 HZ. A type-S thermocouple, which was separated from the conductivity circuit, was used to monitor temperature. Furthermore, a Mo foil was employed to reduce the interference from heating circuit. Experimental results demonstrate that the electrical conductivity of albite melt follows an Arrhenius relationship in both glass (<700�C) and liquid (>1100�C) region. In both cases, electrical conductivity increases with water content but decreases with pressure. In the glass region, electrical conductivity can be modelled as log? = 3.5734 + 0.25534C - (4264+160.43P)/T, where ? is conductivity in S/m, C is water content in wt%, P is pressure in GPa, and T is temperature in K. The above expression implies an activation energy of 82 kJ/mol and an activation volume of 3.1 cc/mol. In the liquid region, electrical conductivity can be modelled as log? = 2.6906 + 0.065915C - (2339+371.97P)/T, which implies an activation energy of 45 kJ/mol and an activation volume of 7.1 cc/mol. The dominating conduction mechanism in albite melts is suggested to be the motion of sodium cation.
Ni, H.; Keppler, H.
Porosity effect on the electrical conductivity of sintered powder compacts
A new equation for calculating the electrical conductivity of sintered powder compacts is proposed. In this equation, the\\u000a effective resistivity of porous compacts is a function of the fully dense material conductivity, the porosity of the compact\\u000a and the tap porosity of the starting powder. The new equation is applicable to powder sintered compacts from zero porosity\\u000a to tap porosity.
J. M. Montes; F. G. Cuevas; J. Cintas
Ionic Conduction at High Electric Field Strengths in Tantalum Pentoxide
Polarization of the cell Ta|Ta2O5|Solution|Pt sets up a very high electric field strength in the oxide and ionic conduction (resulting in growth of the oxide film) occurs with negligible electronic conduction. With this cell measurements of field strength and current density have been made in the temperature range -63 to + 90�C. These results are incompatible with single barrier control
A. R. Bray; P. W. M. Jacobs; L. Young
Electrical conductivity in shaly sands with geophysical applications
We develop a new electrical conductivity equation based on Bussian's model and accounting for the different behavior of ions in the pore space. The tortuosity of the transport of anions is independent of the salinity and corresponds to the bulk tortuosity of the pore space which is given by the product of the electrical formation factor F and the porosity ?. For the cations, the situation is different. At high salinities, the dominant paths for the electromigration of the cations are located in the interconnected pore space, and the tortuosity for the transport of cations is therefore the bulk tortuosity. As the salinity decreases, the dominant paths for transport of the cations shift from the pore space to the mineral water interface and consequently are subject to different tortuosities. This shift occurs at salinities corresponding to ?/t(+)f � 1, where ? is the ratio between the surface conductivity of the grains and the electrolyte conductivity, and t(+)f is the Hittorf transport number for cations in the electrolyte. The electrical conductivity of granular porous media is determined as a function of pore fluid salinity, temperature, water and gas saturations, shale content, and porosity. The model provides a very good explanation for the variation of electrical conductivity with these parameters. Surface conduction at the mineral water interface is described with the Stern theory of the electrical double layer and is shown to be independent of the salinity in shaly sands above 10-3 mol L-1. The model is applied to in situ salinity determination in the Gulf Coast, and it provides realistic salinity profiles in agreement with sampled pore water. The results clearly demonstrate the applicability of the equations to well log interpretation of shaly sands.
Revil, A.; Cathles, L. M., III; Losh, S.; Nunn, J. A.
Electrical conductivity of dense hydrous magnesium silicates with implication for conductivity in the stagnant slab
Electrical conductivities of dense hydrous magnesium silicates (DHMS), phase A, super-hydrous phase B (SuB) and phase D, were measured by means of impedance spectroscopy in the frequency range of 10-1-106 Hz at temperatures up to 775, 700 and 700 K and pressures of 10, 18 and 22 GPa, respectively. For all phases, the increase in electrical conductivity (?) with temperature follows the Arrhenian formula: ?=?0exp(-(?H/kT)). The pre-exponential factors (?0) and activation enthalpies (?H) of phase A, SuB and phase D yield values of 7.28�0.82 S/m and 0.77�0.01 eV, 292�48 S/m and 0.83�0.01 eV and 1342�154 and 0.75�0.01 eV, respectively. Higher pressure DHMS phases show higher conductivity values. The electrical conductivities of phase D and super hydrous phase B are about two and one orders of magnitude higher than that of phase A in the same temperature range, respectively. Although the proton conduction is considered to be a dominant mechanism, there is no clear relationship between water content and conductivity. Rather the conductivity of DHMS phase is closely related to the O⋯O distance. The conductivity-depth profiles for a cold subduction zone were constructed based on the phase proportion predicted in the descending slab. The results show distinctly lower conductivity values than those geophysically observed beneath the northeastern China and the Philippine Sea, where the cold slab stagnates in the mantle transition zone. Consequently, the DHMS phases themselves cannot be a main contributor to enhance the conductivity in the stagnant slab. Dehydration of the stagnant slab would strongly enhance the conductivities in the transition zone beneath northeastern China and Philippine Sea.
Guo, Xinzhuan; Yoshino, Takashi
Relating Relative Hydraulic Conductivity and Electrical Conductivity in the Unsaturated Zone
Monitoring flow in the unsaturated zone is an important task, especially for overseeing managed aquifer recharge, tracking contaminant transport, and optimizing agricultural operations. Geophysical data can provide in-situ unsaturated subsurface information with much higher temporal and spatial resolution over a larger areal extent than traditional hydrologic methods. The measurement of electrical conductivity is a geophysical technique of particular interest in the vadose zone because the geophysical parameter that is obtained is highly correlated with saturation. Changes in saturation can then be used to make qualitative inferences on the rate of fluid motion within the unsaturated zone. However, quantitative information on infiltration rates and unsaturated flow rates via saturation is typically hard to find and usually requires a cumbersome hydrologic inversion that cannot be done in real-time. In this work, we used numerical simulations to find a relationship that relates electrical conductivity not to saturation, but to relative hydraulic conductivity, which has been shown to be a useful proxy for direct estimation of infiltration and unsaturated flow rates even under transient conditions. We obtained this relationship through numerical modeling by generating pore-scale soil structures, partially saturating them through morphological operations according to both wetting and draining schemes and calculating their hydraulic and electrical conductivities at a range of saturations. We found that a power law relationship exists between relative hydraulic conductivity (hydraulic conductivity divided by saturated conductivity) and relative electrical conductivity for each of the sixteen tested media. The power law exponent in the relationship changes depending on whether the medium is being wetted or drained as would be expected as hysteresis is evident in both unsaturated hydraulic and electrical conductivity. Parameters that are typically seen to be related to both saturated conductivities, such as tortuosity, porosity and surface area to volume ratio were calculated for each sphere pack and plotted against the exponent. No correlation was seen between the exponent and these parameters for either the wetting or draining curves. However, the exponent was well constrained for the wetting curve to between 2.45 and 3 and the draining curve to between 1.6 and 2.2. The error introduced by using values within these bounds to estimate the hydraulic conductivity of any of the numerical soil packs using electrical conductivity was negligible, meaning that mean values of 2.75 and 1.8 could be used to estimate the hydraulic conductivity for any pack. These results are applicable to media with minimal surface conduction. We went on to analyze the effects of surface conduction via mineralogy and clay on the power law relationship between electrical and hydraulic conductivity via a number of approaches. We found that the power law relationship between hydraulic and electrical conductivity breaks down when clay content exceeds 5%. However, for media with less clay, use of the relationship with the mean values for exponents found for the clean medium results in less than ten percent error.
Mawer, C. M.; Knight, R. J.; Kitanidis, P. K.
Electrical Conductivity of milk: ability to predict mastitis status
Electrical conductivity (EC) of milk has been intro- duced as an indicator trait for mastitis over the last decade, and it may be considered as a potential trait in a breeding program where selection for improved udder health is included. In this study, various EC traitswereinvestigatedfortheirassociationwithudder health. In total, 322 cows with 549 lactations were in- cluded in the study.
E. Norberg; H. Hogeveen; I. R. Korsgaard; N. C. Friggens; K. H. M. N. Sloth; P. Lovendahl
Electrical conduction in polyethylene terephthalate and polyethylene films
Electrical conduction is studied in polyethylene terephthalate and to a limited extent in polyethylene over a range of fields up to 1�2�106 V cm?1. In common with previous investigations, it is found that the current decays with time according to an inverse power law, but this can be obviated by a conditioning procedure which then allows steady values of current
D M Taylor; T J Lewis
Resistance welding of metals with high electrical and thermal conductivity
A simple device for welding metals with high electrical and thermal conductivity is described. The use of the device, which was adapted from a commercially available carbon deposition unit, for welding 0.0127 and 0.0507-cm-diam Ag, Au, and Pt wires is discussed.
R. Ekern; A. W. Czanderna
Structure and electrical conduction properties of phthalocyanine thin films
The structure and the dc and ac electrical conduction properties of evaporated phthalocyanine thin films are critically reviewed.Results of various structural studies on phthalocyanine single crystals and thin films performed using X-ray diffraction methods are described, and reported unit cell dimensions are given for several phthalocyanines in both the metastable ? and the stable ? forms: reported unit cell dimensions
R. D. Gould
Electrical Conduction and Dielectric Properties of Biodegradable Plastics
We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60�C and the melting point (Tm) was about 166�C. For the temperature dependence of current density (J), J of PLA
Katsuyoshi Shinyama; Shigetaka Fujita
Prediction of electrical contact resistance for anisotropic conductive adhesive assemblies
Anisotropic conductive adhesive (ACA) assembly is emerging as one of the most flexible and cost effective packaging interconnect methods in the microelectronics industry. One of the major impediments to the full realization of the fine pitch (<200 ?m) capabilities of this assembly method is accurate prediction and control of electrical contact resistance. This paper presents a detailed review and direct
Melida Chin; Kaushik A. Iyer; S. Jack Hu
Ion induced electrical conductivity versus chemical doping in polyaniline (PANI)
The effect of ion implantation on the electrical conducting behavior of neutral polyaniline (EB) has been studied and this is compared with the result of chemical doping (ES). The damage caused by ion implantation was analyzed with 4He+ Rutherfold backscattering spectroscopy. The experimental results indicate that the value of the resistivity in the carbon-rich layer of EB resulted from the
Zhi Shen Tong; Mei Zhen Wu; Jiu Long Ding; Qun Hua Hu; Min Zhu; Lei Chen; Xing Long Xu; Mei Xiang Wan; Huai Xia Zhou
Electrical conductivity of silicon carbide composites and fibers
The electrical conductivity, ?, of silicon carbide (SiC) composites and fibers was measured for temperatures between 20 and 1000 �C in order to estimate the magnitude of magnetohydrodynamic effects for liquid metal blankets and a SiC composite structure. Two types of composites were tested: the first type had a matrix made by chemical vapor infiltration (CVI), the second type had
R. Scholz; F. dos Santos Marques; B. Riccardi
Radiation Effect on Thermal and Electric Conductivity of Reactor Graphite.
Results are presented on the measurement of the heat and electric conduction properties of the standard reactor graphite in the initial and irradiated states in the temperature interval from 20 to 600 exp 0 C, pointing to a significant reduction of the he...
P. A. Platonov E. I. Trofimchuk V. I. Karpukhin
High Resolution Global Electrical Conductivity Variations in the Earth's Mantle
Electrical conductivity of the Earth's mantle is a valuable constraint on the water content and melting processes. In Kelbert et al. (2009), we obtained the first global inverse model of electrical conductivity in the mantle capable of providing constraints on the lateral variations in mantle water content. However, in doing so we had to compromise on the problem complexity by using the historically very primitive ionospheric and magnetospheric source assumptions. In particular, possible model contamination by the auroral current systems had greatly restricted our use of available data. We have now addressed this problem by inverting for the external sources along with the electrical conductivity variations. In this study, we still focus primarily on long period data that are dominated by quasi-zonal source fields. The improved understanding of the ionospheric sources allows us to invert the magnetic fields directly, without a correction for the source and/or the use of transfer functions. It allows us to extend the period range of available data to 1.2 days - 102 days, achieving better sensitivity to the upper mantle and transition zone structures. Finally, once the source effects in the data are accounted for, a much larger subset of observatories may be used in the electrical conductivity inversion. Here, we use full magnetic fields at 207 geomagnetic observatories, which include mid-latitude, equatorial and high latitude data. Observatory hourly means from the years 1958-2010 are employed. The improved quality and spatial distribution of the data set, as well as the high resolution modeling and inversion using degree and order 40 spherical harmonics mapped to a 2x2 degree lateral grid, all contribute to the much improved resolution of our models, representing a conceptual step forward in global electromagnetic sounding. We present a fully three-dimensional, global electrical conductivity model of the Earth's mantle as inferred from ground geomagnetic observatory data, and use additional constraints to interpret these results in terms of mantle processes and compositional variations.
Kelbert, A.; Sun, J.; Egbert, G. D.
Microbial interspecies electron transfer via electric currents through conductive minerals
In anaerobic biota, reducing equivalents (electrons) are transferred between different species of microbes [interspecies electron transfer (IET)], establishing the basis of cooperative behaviors and community functions. IET mechanisms described so far are based on diffusion of redox chemical species and/or direct contact in cell aggregates. Here, we show another possibility that IET also occurs via electric currents through natural conductive minerals. Our investigation revealed that electrically conductive magnetite nanoparticles facilitated IET from Geobacter sulfurreducens to Thiobacillus denitrificans, accomplishing acetate oxidation coupled to nitrate reduction. This two-species cooperative catabolism also occurred, albeit one order of magnitude slower, in the presence of Fe ions that worked as diffusive redox species. Semiconductive and insulating iron-oxide nanoparticles did not accelerate the cooperative catabolism. Our results suggest that microbes use conductive mineral particles as conduits of electrons, resulting in efficient IET and cooperative catabolism. Furthermore, such natural mineral conduits are considered to provide ecological advantages for users, because their investments in IET can be reduced. Given that conductive minerals are ubiquitously and abundantly present in nature, electric interactions between microbes and conductive minerals may contribute greatly to the coupling of biogeochemical reactions.
Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya
Electrical conduction and polarization of calcite single crystals
The electrical conductivity and polarization properties of calcite single crystals with three orientations, namely, a (00.1) plane perpendicular to the crystallographic c axis (10.0) plane parallel to the crystallographic c axis, and a (10.4) cleavage plane, were studied by both complex impedance and thermally stimulated depolarization current (TSDC) measurements. Conductivities for (00.1)-, (10.0)-, and (10.4)-oriented single calcite crystals at 400-600 �C were 1.16 � 10-7 - 1.05 � 10-5, 7.40 � 10-8 - 4.27 � 10-6, and 4.27 � 10-7 - 2.86 � 10-5 ?-1 m-1, respectively, and the activation energies for conduction were 112, 103, and 101 kJ mol-1, respectively. The TSDC spectra verified the electrical polarizability of calcite crystals. The activation energy for depolarization, estimated from TSDC spectra, of the (00.1)-, (10.0)-, and (10.4)-oriented calcite substrates were 112, 119, and 114 kJ mol-1, respectively. Considering the correlation between the processes of conduction and electric polarization, we proposed the mechanisms of conduction and polarization in calcite on the assumption of oxide ion transport.
Wada, Norio; Horiuchi, Naohiro; Wang, Wei; Hiyama, Tetsuo; Nakamura, Miho; Nagai, Akiko; Yamashita, Kimihiro
Electrical conductivity anomalies associated with circular lunar maria
A strong anisotropy is observed in magnetic field fluctuations measured by the Lunokhod 2 magnetometer located on the eastern edge of Mare Serenitatis. This anisotropy can be explained by a regional anomaly in the subsurface electrical conductivity distribution associated with the mare similar to the proposed conductivity anomaly associated with Mare Imbrium. The Serenitatis magnetic field anisotropy is compared to the field fluctuation measured by the Apollo 16 magnetometer 1100 km to the south, and this comparison indicates that the subsurface conductivity distribution can be modeled by a nonconducting layer in the lunar lithosphere which is 150 km thick beneath the highlands and 300 km thick beneath Serenitatis. The decrease in electrical conductivity of the upper mantle beneath the mare may result from lower temperatures due to transport of thermal energy and radioactive heat sources to the surface during mare flooding. This proposed anomaly, along with that proposed for Mare Imbrium, strengthens the possibility of regional anomalies in electrical conductivity associated with all circular lunar maria.
Dyal, P.; Daily, W. D.
Electrical insulation and conduction coating for fusion experimental devices
The development of electrical insulation and conduction coating methods that can be applied to large components of fusion experimental devices has been investigated. A thermal spraying method is used to coat the insulation or conduction materials on the structural components because of its applicability for large surfaces. The insulation material chosen was Al{sub 2}O{sub 3}, while Cr{sub 3}C{sub 2}-NiCr and WC-NiCr were chosen as conduction materials. These materials were coated on stainless steel substrates to examine the basic characteristics of the coated layers, such as their adhesive strength to the substrate, thermal shock resistance, electrical resistance, dielectric breakdown voltage, and thermal conductivity. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed adequate frictional properties. The spraying method was tested on a 100- x 1000-mm surface and found to be applicable for large surfaces of experimental fusion devices. 9 refs., 6 figs., 15 tabs.
Onozuka, Masanori; Tsujimura, Seiji; Toyoda, Masahiko; Inoue, Masahiko [Mitsubishi Heavy Industries, Ltd., Yokohama (Japan); Abe, Tetsuya; Murakami, Yoshio [Japan Atomic Energy Research Inst., Naka (Japan)
The mechanical and the electrical properties of conducting polypyrrole fibers
The mechanical and the electrical properties of polypyrrole (PPy) fibers and electrochemically deposited PPy films were studied. It was found that the PPy fibers showed a significantly higher strength than the PPy films due to better orientation of the molecular structure. The electrochemically prepared PPy films had a higher electrical conductivity than that of the fibers at high temperature. At low temperature, the PPy fibers showed the higher conductivity. The conductivity results were analyzed in the frame of the three-dimensional variable range hopping model. The results showed that at room temperature the average hopping distance for the fibers was about 4 A? while for the films it increases to about 5.7 A?. This corresponds to about 1 and 2 monomer units in length for the fiber and film samples, respectively.
Foroughi, J.; Ghorbani, S. R.; Peleckis, G.; Spinks, G. M.; Wallace, G. G.; Wang, X. L.; Dou, S. X.
Unconventional approaches to combine optical transparency with electrical conductivity
The combination of electrical conductivity and optical transparency in the same material - known to be a prerogative of only a few oxides of post-transition metals, such as In, Sn, Zn and Cd - manifests itself in a distinctive band structure of the transparent conductor host. While the oxides of other elements with s2 electronic configuration, for example, Mg, Ca, Sc and Al, also exhibit the desired optical and electronic features, they have not been considered as candidates for achieving good electrical conductivity because of the challenges of efficient carrier generation in these wide-bandgap materials. Here we demonstrate that alternative approaches to the problem not only allow for attaining the transport and optical properties which compete with those in currently utilized transparent conducting oxides (TCO), but also significantly broaden the range of materials with a potential of being developed into novel functional transparent conductors.
Medvedeva, J. E.
The combination of electrical conductivity and optical transparency in the same material known to be a prerogative of only a few oxides of post-transition metals, such as In, Sn, Zn and Cd manifests itself in a distinctive band structure of the transparent conductor host. While the oxides of other elements with s2 electronic configuration, for example, Mg, Ca, Sc and Al, also exhibit the desired optical and electronic features, they have not been considered as candidates for achieving good electrical conductivity because of the challenges of efficient carrier generation in these wide-bandgap materials. Here we demonstrate that alternative approaches to the problem not only allow for attaining the transport and optical properties which compete with those in currently utilized transparent conducting oxides (TCO), but also significantly broaden the range of materials with a potential of being developed into novel functional transparent conductors.
Dross, F.; Robbelein, J.; Vandevelde, B.; van Kerschaver, E.; Gordon, I.; Beaucarne, G.; Poortmans, J.
Consequences of electrical conductivity in an orb spider's capture web
The glue-coated and wet capture spiral of the orb web of the garden cross spider Araneus diadematus is suspended between the dry silk radial and web frame threads. Here, we experimentally demonstrate that the capture spiral is electrically conductive because of necks of liquid connecting the droplets even if the thread is stretched. We examine how this conductivity of the capture spiral may lead to entrapment of charged airborne particles such as pollen, spray droplets and even insects. We further describe and model how the conducting spiral will also locally distort the Earth's ambient electric field. Finally, we examine the hypothesis that such distortion could be used by potential prey to detect the presence of a web but conclude that any effect would probably be too small to allow an insect to take evasive action.
Vollrath, Fritz; Edmonds, Donald
Electrical conductivity beneath the volcanoes of the NW Argentinian Puna
The detection of a high conductivity anomaly below the northern (Bolivian) part of the Altiplano-Puna plateau motivated a new analysis of magnetotelluric (MT) data which were formerly collected further south in NW Argentina. After appropriate dimensionality analysis from a profile located in the magmatic arc and backarc of the south-central Andean subduction zone, two-dimensional (2-D) electrical conductivity modelling of the crust and upper mantle in the eastern sector could be performed, i.e., in the eastern Puna and backarc zone. The 2-D conductivity models show a conductive zone beneath the eastern Puna shoshonitic volcanoes and nearby Tuzgle volcano, which reaches from the upper crust to the upper mantle. We suggest that this conductor is related to the Puna volcanism of enriched mantle composition. Whether the western Puna is also characterized by anomalous conductivities at crust-mantle depths, is still an open question.
Lezaeta, Pamela; Brasse, Heinrich
Effect of iron content on the electrical conductivity of perovskite and magnesiowuestite assemblages at lower mantle conditions
The electrical conductivity of (Mg/0.76/Fe/0.24/)SiO3 perovskite and of an assemblage of (Mg/0.89/Fe/0.11/)SiO3 perovskite + (Mg/0.70/Fe/0.30/)O magnesiowiestite was measured at pressures of 45-80 GPa and temperatures from 295 to 3600 K. The apparent activation energy for electrical conduction is 0.24 (+ or - 0.10) eV for the perovskite and 0.20 (+ or - 0.08) eV for the perovskite + magnesiowuestite assemblage. Comparing present results with those derived previously for Fe-poor samples, it is found that the electrical conductivities of both the silicate perovskite and the perovskite + magnesiowuestite assemblage depend strongly on iron content. Thus, the electrical conductivity distribution inside the earth could provide an important constraint in modeling the composition of the lower mantle.
Li, Xiaoyuan; Jeanloz, Raymond
Optimization and Testing of Electrically Conductive Spacecraft Coatings
This is the final report discussing work done for the Space Environmental Effects (SEE) program in the Materials and Processes Laboratory, on electrically conductive thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude lower electrical resistivity than most available thermal control coatings. Extensive research has taken place over the last few years to develop a variety of spacecraft coatings with the unique property of being able to conduct surface charge to a substrate or grounding system. The ability to conduct surface charge to a safe point, while maintaining optical properties and performance, is highly advantageous in maintaining operational space based systems. Without this mechanism the surface of a spacecraft can accumulate charge to the point that a catastrophic electrical breakdown can occur, resulting in damage to or failure of the spacecraft. Ultimately, use of this type of coating will help mitigate many of the concerns that NASA and the space industry still have for their space based systems. The unique coatings studied here fall into two specific categories: 1) broadband absorber and 2) selective absorber. These coatings have controllable solar absorptance and electrical surface resistivity values over the designated ranges. These coatings were developed under an SBIR program which focused on the development of such constituents and coatings. This project focused on simulated space environmental effects testing with the intent of using this data to help optimize the stability and initial properties of these coatings.
Mell, Richard J.
Inflow and outflow signatures in flowing wellbore electrical conductivity logs
Flowing wellbore electrical-conductivity logging provides a means to determine hydrologic properties of fractures, fracture zones, or other permeable layers intersecting a borehole in saturated rock. The method involves analyzing the time-evolution of fluid electrical-conductivity logs obtained while the well is being pumped and yields information on the location, hydraulic transmissivity, and salinity of permeable layers, as well as their initial (or ambient) pressure head. Earlier analysis methods were restricted to the case in which flows from the permeable layers or fractures were directed into the borehole. More recently, a numerical model for simulating flowing-conductivity logging was adapted to permit treatment of both inflow and outflow, including analysis of natural regional flow in the permeable layer. However, determining the fracture properties with the numerical model by optimizing the match to the conductivity logs is a laborious trial-and-error procedure. In this paper, we identify the signatures of various inflow and outflow features in the conductivity logs to expedite this procedure and to provide physical insight for the analysis of these logs. Generally, inflow points are found to produce a distinctive signature on the conductivity logs themselves, enabling the determination of location, inflow rate, and ion concentration in a straightforward manner. Identifying outflow locations and flow rates, on the other hand, can be done with a more complicated integral method. Running a set of several conductivity logs with different pumping rates (e.g., half and double the original pumping rate) provides further information on the nature of the feed points. In addition to enabling the estimation of flow parameters from conductivity logs, an understanding of the conductivity log signatures can aid in the design of follow-up logging activities.
Doughty, Christine; Tsang, Chin-Fu
High performance electrically conductive adhesives (ECAs) for leadfree interconnects
Electrically conductive adhesives (ECAs) are one of the lead-free interconnect materials with the advantages of environmental friendliness, mild processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability. However, some challenging issues still exist for the currently available ECAs, including lower electrical conductivity, conductivity fatigue in reliability tests, limited current-carrying capability, poor impact strength, etc. The interfacial properties is one of the major considerations when resolving these challenges and developing high performance conductive adhesives. Surface functionalization and interface modification are the major approaches used in this thesis. Fundamental understanding and analysis of the interaction between various types of interface modifiers and ECA materials and substrates are the key for the development of high performance ECA for lead-free interconnects. The results of this thesis provide the guideline for the enhancement of interfacial properties of metal-metal and metal-polymer interactions. Systematic investigation of various types of ECAs contributes to a better understanding of materials requirements for different applications, such as surface mount technology (SMT), flip chip applications, flat panel display modules with high resolution, etc. Improvement of the electrical, thermal and reliability of different ECAs make them a potentially ideal candidate for high power and fine pitch microelectronics packaging option.
Li, Yi
Thermal and Electrical Conductivity Probe for Phoenix Mars Lander
Electrical conductivity of aqueous solutions of aluminum salts
We present experimental measurements of the specific electrical conductivity (?) in aqueous solutions of aluminum salts at different temperatures, covering all salt concentrations from saturation to infinite dilution. The salts employed were AlCl3 , AlBr3 , AlI3 , and Al(NO3)3 , which present a 1:3 relationship between the electrical charges of anion and cation. In addition, we have measured the density in all ranges of concentrations of the four aqueous electrolyte solutions at 298.15K . The measured densities show an almost linear behavior with concentration, and we have fitted it to a second order polynomial with very high degree of approximation. The measurement of the specific conductivity at constant temperature reveals the existence of maxima in the conductivity vs concentration curves at molar concentrations around 1.5M for the three halide solutions studied, and at approximately 2M for the nitrate. We present a theoretical foundation for the existence of these maxima, based on the classical Debye-H�ckel-Onsager hydrodynamic mean-field framework for electrical transport and its high concentration extensions, and also a brief consideration of ionic frictional coefficients using mode-coupling theory. We also found that the calculated values of the equivalent conductance vary in an approximately linear way with the square root of the concentration at concentrations as high as those where the maximum of ? appears. Finally, and for completeness, we have measured the temperature dependence of the electrical conductivity at selected concentrations from 283to353K , and performed a fit to an exponential equation of the Vogel-Fulcher-Tamman type. The values of the calculated temperatures of null mobility of the four salts are reported.
Vila, J.; Rilo, E.; Segade, L.; Cabeza, O.; Varela, L. M.
Optimum depth of investigation and conductivity response rejection of the different electromagnetic devices measuring apparent magnetic susceptibility
Electromagnetic susceptibility surveys are valuable for archaeological prospection owing to their ability to cover large areas of land. Their use, however, is often compromised by the conductivity in fluence of the soil and the limited investigation depth of the susceptibility response. To examine these constraints further, we compared the characteristics of two types of apparatus: coincident loop (e.g. Bartington MS2
Christophe Benech; Eric Marmet
Electrical Conductivity of Cadmium Oxide in High-Frequency Electrical Fields.
Results are given of an investigation into the electrical conductivity of polycrystalline samples of cadmium oxide using the non-electrode method in the frequency range (7 to 8.9) x 10 to the 9th power cps. (Author)
R. A. Baltrushaitis P. P. Brazdzhyunas
Electrical conductivity in lipid bilayer membranes induced by pentachlorophenol.
Electrical conductivity induced in thin lipid bilayer membranes by pentachlorophenol has been studied. The membranes were formed from phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl glycerol and various amounts of cholesterol. The position and the magnitude of the maximum of the conductivity vs. pH curve depend on the type of lipids and cholesterol content. At low pentachlorophenol concentrations and low pH the concentration dependence of conductivity is quadratic and becomes linear at higher pH. Above 10(-5) M of pentachlorophenol the concentration dependence of the membrane conductivity tends to saturate. Presence of pentachlorophenol enhances membrane transport of nonactin-K+ complex. Increase of cholesterol content increases pentachlorophenol induced conductivity in all membranes and shifts the conductivity toward lower pH. For phosphatidyl choline the largest rate of change of membrane conductivity with cholesterol occurs at 1:1 phospholipid to cholesterol molar ratio. Pentachlorophenol is found to be a class II uncoupler and the experimental results are consistent with the hypothesis that the membrane permeable species are dimers formed by combination of neutral and dissociated pentachlorophenol molecules. Several schemes of membrane conduction, including dimer formation in the aqueous phase as well as at the membrane-water interface have been considered. Arguments are given in favor of the formation of dimers within the membrane surface.
Smejtek, P; Hsu, K; Perman, W H
Effect of orientation anisotropy on calculating effective electrical conductivities
This paper develops an analytical effective medium theory (EMT) equation for calculating the effective conductivity of a mixture based on Maxwell's and Maxwell-Garnett's theories, extended to higher volume fractions using Bruggeman's unsymmetrical treatment (BUT), with a long term goal of extending the treatment to mixtures more representative of real materials in order to calculate their effective electrical conductivity. The development accounts for spheroid shaped inclusions of varying degrees of anisotropic orientation. The orientation is described by the introduction of a distribution function. Two methodologies valid for the inclusion dilute limit were used to evaluate the effective conductivity: one based on Maxwell's far field approach, and the other based on the Maxwell-Garnett in the matrix approach. It was found that while the dilute limit equations for the effective conductivity were different, the final EMT equations derived by applying BUT collapsed to the same formula which was generalized for anisotropic orientation based on the distribution function presented.
Myles, Timothy D.; Peracchio, Aldo A.; Chiu, Wilson K. S.
Evolving concepts on the electrical conductivity of the continental crust
Several decades of geophysical research have established that the middle and lower crust are typically much more electrically conductive than the upper crust and orders of magnitude more so than either dry crystalline rocks or rock-forming silicate minerals at similar conditions. The high conductivities at depth were originally ascribed to the presence of saline fluids. Two problems with this view have emerged: hot water is far too reactive with surrounding rocks to remain for long in the deep crust, and the permeability of hot, ductile crust is too low to account for the observed conductivities. Another possibility is that graphitic carbon exerts the primary control on deep crustal conductivity. Graphitic carbon can exist in different habits and abundances and influence conductivity on different scales. Buried organic-rich shales form megascopic layers in which carbon is likely to be interconnected over kilometers, but such layers are not common. Graphitic veins formed during metamorphism are probably more common but much less extensive. Carbon also forms films on microfracture surfaces. These have been observed in many crystalline rocks and appear to be ubiquitous; they are also probably extensive and thus may generally account for the crustal conductivity structure. The microcrack network need not be completely interconnected to impart high electrical conductivity. It can exist in series with conductive minor phases such as oxides or sulfides, and it also reduces the size of regions of high resistivity. Regardless of mode of occurrence, that carbonaceous rocks are more abundant in the Phanerozoic than Precambrian records explains why the deep Phanerozoic crust is more conductive than old shield regions. The control of rock conductivity by carbon in the microfracture network implies that conductivity is in part controlled by microstructure and microfabric and by the chemical state of carbon. Observations of rocks from the KTB borehole indicate that microcrack carbon at the bottom of the hole (9.1 km depth) is relatively pure but at shallower levels contains a higher proportion of hydrocarbon. With uplift of the host rocks, carbon may react with fluids to form less conductive hydrocarbons. This retrograde metamorphism of microcrack carbon may be one reason that shallow crust can be less conductive than deep crust.
Mathez, E. A.
Correlations of electrical conductivity to slag composition and temperature
The electrical conductivity of slags is an important factor in the design of electric smelting furnaces. Although there are many experimental studies on this subject, as yet there are no quantitative correlations of conductivity to slag composition and temperature. The objective of this work was to develop such correlations, on the basis of the experimental data by various other authors. The results show that in the concentration range of industrial-type SiO2-CaO-MgO-MnO slags the slag conductivity can be expressed as a linear function of the molar concentrations of the basic oxides; in the concentration range of industrial nonferrous slags, where the iron oxide content is usually over 20 pct, the slag conductivity can be expressed as an exponential function of the molar concentrations of the iron and basic oxides. The effect of temperature on slag conductivity, in the industrial range of interest, can be accounted for by means of an Arrhenius-type of equation.
Jiao, Q.; Themelis, N. J.
The Thermal Electrical Conductivity Probe (TECP) for Phoenix
The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring the electrical conductivity of the regolith, as well as the dielectric permittivity. In the vapor phase, TECP is capable of measuring the atmospheric H2O vapor abundance, as well as augment the wind velocity measurements from the meteorology instrumentation. TECP is mounted near the end of the 2.3 m Robotic Arm, and can be placed either in the regolith material or held aloft in the atmosphere. This paper describes the development and calibration of the TECP. In addition, substantial characterization of the instrument has been conducted to identify behavioral characteristics that might affect landed surface operations. The greatest potential issue identified in characterization tests is the extraordinary sensitivity of the TECP to placement. Small gaps alter the contact between the TECP and regolith, complicating data interpretation. Testing with the Phoenix Robotic Arm identified mitigation techniques that will be implemented during flight. A flight model of the instrument was also field tested in the Antarctic Dry Valleys during the 2007-2008 International Polar year. 2
Zent, Aaron P.; Hecht, Michael H.; Cobos, Doug R.; Campbell, Gaylon S.; Campbell, Colin S.; Cardell, Greg; Foote, Marc C.; Wood, Stephen E.; Mehta, Manish
Electrical conductivity of the roof of electric arc steel melting furnaces
The authors test for the relationship between temperature and electrical conductivity in the refractory liners of arc furnaces used by the steel industry in the Soviet Union in order to minimize the degradation of these refractories by electrical and thermal processes, to maximize their service life, and to optimize their insulating properties and the consequent efficiency of the furnaces in which they are utilized.
Osipenko, V.D.; Garbuz, S.S.; Khromov, A.P.
Orbital dynamics of two electrically charged conducting spheres
The similar forms of Coulomb's law of electrostatics and Newton's law of gravitation suggest that two oppositely charged spheres can orbit each other by means of the electrostatic force. We demonstrate electrostatic binary orbits using two oppositely charged graphite coated Styrofoam� spheres. The experiment was conducted on the NASA aircraft Weightless Wonder which simulates weightless conditions. Videos of 23 orbital attempts were analyzed to investigate the dynamics and orbital stability of the two sphere system. The results support predictions of a recently developed theory that establishes criteria for stable orbits between two conducting, electrically charged spheres.
Hoffmeister, Brent K.; Meyer, Deseree A.; Atkins, Brad M.; Franks, Gavin A.; Fuchs, Joshua T.; Li, Lulu; Sliger, Chase W.; Thompson, Jennifer E.
Single-photon heat conduction in electrical circuits
We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominant part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting quantum bits coupled to cavities.
Jones, P. J.; Huhtam�ki, J. A. M.; Tan, K. Y.; M�tt�nen, M.
Electrical conductivity of tissue at frequencies below 1 MHz
A two-pronged approach, review and measurement, has been adopted to characterize the conductivity of tissues at frequencies below 1 MHz. The review covers data published in the last decade and earlier data not included in recent reviews. The measurements were carried out on pig tissue, in vivo, and pig body fluids in vitro. Conductivity data have been obtained for skeletal and myocardial muscle, liver, skull, fat, lung and body fluids (blood, bile, CSF and urine). A critical analysis of the data highlights their usefulness and limitations and enables suggestions to be made for measuring the electrical properties of tissues.
Gabriel, C.; Peyman, A.; Grant, E. H.
The deep lunar electrical conductivity profile - Structural and thermal inferences
Simultaneous lunar surface and orbital magnetometer records are reexamined, to ascertain intervals which may be suitable for measuring lunar inductive response in the solar wind and terrestrial magnetosheath. Power spectral estimates of the response tangent to the lunar surface, defined in terms of transfer and gain functions, are obtained for the 0.0001-0.01 Hz frequency range. The maximum consistency of estimates from different time intervals is found when the initial analysis is limited to the tangential direction of maximum incident power, or that direction in which the ratio of signal to background noise is greatest. Spherically symmetric plasma confinement theory is used in the interpretation of transfer function data, by way of forward model calculations, under the assumption of continuous electrical conductivity increase with depth. Results are presented for internal electrical conductivity profile, metallic core radius, and selenotherm limits.
Hood, L. L.; Herbert, F.; Sonett, C. P.
Electrical conductivity of two-phase composite material
It is a long standing problem to predict the effective electrical conductivity of binary mixtures or two-phase composites. The early history of this problem is often connected with the names of Clausius, Mossotti, Lorenz, and Lorentz. Currently, the general effective media (GEM) equation, proposed by McLachlan, seems to explain different results of experimental studies over an entire composition range. The GEM equation consists of electrical conductivity of constituent phases, their volume fractions and two free parameters. As has been pointed out by Boccaccini the free parameters of the GEM equation do not have yet a clear correlation with the real features of the microstructure. In this paper the author discusses such correlation using connections among the GEM equation, percolation theory and effective medium theory.
Kovacik, J. [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics] [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics
Equation of state and electrical conductivity of expanded Al
Ab-initio molecular dynamics (AIMD) simulations have been performed for generating equation of state (EOS) data as well as atomic configurations of expanded states of Al. The generated atomic configurations have been used for the calculation of electrical conductivity. AIMD simulations have been performed using the ABINIT code and electrical conductivity has been calculated using the Kubo-Greenwood formula as implemented in ABINIT. The generated equation of state data have been fitted to a three-term EOS model using adjustable parameters of ionic and electronic Gruneisen parameters. This three-term EOS model has been used to estimate critical density, temperature and pressure in the liquid-vapour region. The calculated values of critical density, temperature and pressure show good agreement with results available in the literature.
Mishra, V.; Mehra, V.; Chaturvedi, S.
Electrical conductivity and total dissolved solids in urine
The objective of this paper is to study the relevance of electrical conductivity (EC) and total dissolved solids (TDS) in\\u000a early morning and random samples of urine of urinary stone patients; 2,000 urine samples were studied. The two parameters\\u000a were correlated with the extent of various urinary concrements. The early morning urine (EMU) and random samples of the patients\\u000a who
Y. M. Fazil Marickar
The Electrical Conductivity of Packed Beds Containing Macroporous Cation Exchanger
The electrical conductivity of packed beds containing macroporous Duolite C-25 polystyrene sulfonate cation exchanger equilibrated with aqueous solutions of a single electrolyte (NaCl or HCl) has been measured over a range of electrolyte concentrations. The results are interpreted in terms of a two-phase model for the resin particle involving (1) the resin matrix, with the conventional properties of polystyrene sulfonate
Darryl G. Howery; Sugihiko Tada
Nonlinear dc and ac conductivity in electrically insulating composites
The non-linear electrical behavior of zinc oxide, used to practical advantage in surge arresters on distribution power systems, has been replicated in epoxy resin, which has been filled with an appropriate volume fraction of this intrinsically semi-conducting material. Comparison has been made with epoxy resin containing a similar volume fraction of aluminum oxide in order to establish that the non-linearity
K. P. Donnelly; B. R. Varlow
This paper presents the results of an investigation of the specific electric conductivity of melts of the potassium, hafnium-containing fluoride-chloride ternary reciprocal system which is of practical interest because fluoride-chloride melts containing hafnium can be used as electrolytes in the preparation of metallic hafnium. Experimental results depend largely on the purity of the salts that are used, so much attention
S. E. Darienko; Yu. F. Chervinskii; S. F. Katyshev; I. F. Nichkov
Practical tools are needed to identify and advance sustainable management practices to optimize economic return, conserve soil, and minimize negative off-site environmental effects. The objective of this article is to review current research in non-saline soils of the central U.S. to consider bulk soil electrical conductivity (EC a) as an assessment tool for: (1) tracking N dynamics, (2) identifying management
C. K. Johnson; R. A. Eigenberg; J. W. Doran; B. J. Wienhold; B. Eghball; B. L. Woodbury
Influence of oxygen fugacity on the electrical conductivity of hydrous olivine: Implications for the mechanism of conduction
Various mechanisms of hydrogen-assisted electrical conductivity predict different dependence of conductivity on oxygen fugacity. If a majority of hydrogen-related defects (i.e., two protons at M-site) carries the electrical current, then the conductivity will be independent of oxygen fugacity, whereas if a minority defect such as free proton carries the electrical conductivity, then the electrical conductivity will decrease with oxygen fugacity. We have determined the dependence of hydrogen-assisted electrical conductivity on oxygen fugacity in hydrous olivine. We found that the hydrogen-assisted electrical conductivity in olivine decreases with oxygen fugacity. This result supports a model where hydrogen-related defect with minor concentration (e.g., free proton or one hydrogen at M-site) carries most of the electric charge.
Dai, Lidong; Karato, Shun-ichiro
On the electrical conductivity of Ti-implanted alumina
Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.
Salvadori, M. C.; Teixeira, F. S.; Cattani, M. [Institute of Physics, University of Sao Paulo, C.P. 66318, CEP 05315-970, Sao Paulo S.P. (Brazil); Nikolaev, A.; Savkin, K. P.; Oks, E. M. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Park, H.-K.; Phillips, L. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Yu, K. M.; Brown, I. G. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 � 1016 cm-2 and the maximum dose for which the system remains an insulator-conductor composite is about 10 � 1016 cm-2. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.
Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.
Electrical conductivity of disordered semi-infinite systems
Employing the Kubo-Greenwood formula the electrical conductivity of disordered semi-infinite systems is formulated in terms of the (Screened) KKR method and the Coherent Potential Approximation. It is shown that by neglecting vertex corrections in the same manner as in the bulk case, the elements of the electrical conductivity tensor can be described in terms of ''layer-diagonal''- and ''layer-off-diagonal'' contributions. In order to discuss effects of the underlying electronic structure on the electrical conductivity, but also to point out particular contributions to it, Bloch spectral functions are formulated. A spin-polarized (relativistic) application of the present theory to non-collinear disordered magnetic multilayers allows to discuss giant magnetoresistance (GMR) on an ab-inito level in quite a general context. --This paper was financially supported by the CMS, Vienna, the Hungarian National Scientific Research Foundation (OTKA F014378), from the Office of Naval Research (N00014-91-J-1695), and a grant from NATO, CGR. 890599.
Weinberger, P.; Szunyogh, L.; Ujfalussy, B.; Levy, P. M.; Banhart, J.
Electrical studies on silver based fast ion conducting glassy materials
Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI-Ag2O-[(1-x)B2O3-xTeO2] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz-3MHz by Impedance Analyzer in the temperature range 303-423K. The DC conductivity measurements were also carried out in the temperature range 300-523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10-2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.
Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.
Determination of Electric Conductivity and Local SAR Via B1 Mapping
The electric conductivity can potentially be used as an additional diagnostic parameter, e.g., in tumor diagnosis. Moreover, the electric conductivity, in connection with the electric field, can be used to estimate the local SAR distribution during MR measurements. In this study, a new approach, called electric properties tomography (EPT) is presented. It derives the patient's electric conductivity, along with the
Ulrich Katscher; Tobias Voigt; Christian Findeklee; Peter Vernickel; Kay Nehrke; Olaf D�ssel
Electrical Conductivity Measurement and Anisotropy of Mylonite and Cataclasite
Resent studies of electromagnetic survey reveal the electrical conductivity structure at the deeper part of faults. There seems to be high conductivity region around the focal areas. The high conductivity may be related to the existence of water in rocks, which affect the strength and activity of faults, i.e., earthquake. Investigations on the electrical conductivity structure suggest important clues on the mechanism and conditions of earthquake occurrence. Rocks at the focal zone of a fault are expected to suffer from hard deformation and/or fracturing with alteration. Rocks have characteristic fabrics. They are called fault-related rocks, such as mylonite and cataclasite. We collected mylonite and cataclasite samples from the Hatagawa fracture zone in northeast Japan. The Hatagawa fracture zone is regarded as a major exhumed fault. We can observe the mylonite and cataclasite at a surface now that were produced from granitic rocks at the focal depth region in the past. We conducted measurements of electrical conductivities of the fault-related rocks at ambient condition, as a first step. We connected a frequency response analyzer and a potentiostat to measure AC impedance spectra. The combination of the two instruments performs sine wave correlation between signals passing trough a sample and a reference resistance. In addition, the potentiostat can measure a micro current. As a result, the measurement system is basically resistant to an electrical noise around the sample under severe condition and is able to measure up to 109 ? . We observed clearly foliations and lineations in mylonite samples. We cut each mylonite sample into three cylindrical chips parallel to three directions: parallel to both the foliation and the lineation (x-axis), parallel to the foliation and perpendicular to the lineation (y-axis), perpendicular to the foliation (z-axis). We did not observe any planar or linear fabric on the cataclasite samples. Porosities of the samples were less than 1 %. The conductivities at 1 Hz of samples under dry condition (samples are heated at 120 degree C for 6 hours) are about 10-8 1/? m and have little difference among samples. Under wet condition at the same frequency (samples were forcibly saturated by distilled water in a vacuum chamber), conductivities of all samples increased by more than one order of magnitude, but conductivities along three direction of mylonite are significantly different. The conductivity along x-axis and y -axis was higher by about one order and several times, respectively, than that along z-axis. This result suggests the distribution and connectivity of cracks in mylonite are anisotropic and more conductive water than rock matrix connected along x-axis. At focal deep region along a fault, cracks must be compacted, but, if thin sheets of water are distributed anisotropically in mylonite zone, some anisotropic conductivity structure may be detected.
Omura, K.
High temperature electrically conducting ceramic heating element and control system
Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements, a furnace was fabricated and demonstrated to have excellent thermal response and cycling capability. The furnace was used to melt platinum-20% rhodium alloy (melting point 1904 C) with an isothermal ceramic heating element having a nominal working cavity size of 2.5 cm diameter by 10.0 cm long. The furnace was operated to 1940 C with the isothermal ceramic heating element. The same furnace structure was fitted with a pair of main heater elements to provide axial gradient temperature control over a working cavity length of 17.8 cm.
Halbach, C. R.; Page, R. J.
Method for electrically isolating an electrically conductive member from another such member
The invention relates to methods for electrically isolating a first electrically conductive member from another such member by means of an electrically insulating medium. In accordance with the invention, the insulating medium is provided in the form of MgO which contains a dopant selected from lithium, copper, cobalt, sodium, silver, gold and hydrogen. The dopant is present in the MgO in an amount effective to suppress dielectric breakdown of the MgO, even at elevated temperatures and in the presence of electrical fields.
Tsang, K.L.; Chen, Y.
An Overview of Earth's Global Electric Circuit and Atmospheric Conductivity
The Earth�s global atmospheric electric circuit depends on the upper and lower atmospheric boundaries formed by the ionosphere and the planetary surface. Thunderstorms and electrified rain clouds drive a DC current (�1 kA) around the circuit, with the current carried by molecular cluster ions; lightning phenomena drive the AC global circuit. The Earth�s near-surface conductivity ranges from 10-7 S m-1 (for poorly conducting rocks) to 10-2 S m-1 (for clay or wet limestone), with a mean value of 3.2 S m-1 for the ocean. Air conductivity inside a thundercloud, and in fair weather regions, depends on location (especially geomagnetic latitude), aerosol pollution and height, and varies from �10-14 S m-1 just above the surface to 10-7 S m-1 in the ionosphere at �80 km altitude. Ionospheric conductivity is a tensor quantity due to the geomagnetic field, and is determined by parameters such as electron density and electron-neutral particle collision frequency. In the current source regions, point discharge (coronal) currents play an important role below electrified clouds; the solar wind-magnetosphere dynamo and the unipolar dynamo due to the terrestrial rotating dipole moment also apply atmospheric potential differences. Detailed measurements made near the Earth�s surface show that Ohm�s law relates the vertical electric field and current density to air conductivity. Stratospheric balloon measurements launched from Antarctica confirm that the downward current density is �1 pA m-2 under fair weather conditions. Fortuitously, a Solar Energetic Particle (SEP) event arrived at Earth during one such balloon flight, changing the observed atmospheric conductivity and electric fields markedly. Recent modelling considers lightning discharge effects on the ionosphere�s electric potential (�+250 kV with respect to the Earth�s surface) and hence on the fair weather potential gradient (typically �130 V m-1 close to the Earth�s surface. We conclude that cloud-to-ground (CG) lightning discharges make only a small contribution to the ionospheric potential, and that sprites (namely, upward lightning above energetic thunderstorms) only affect the global circuit in a miniscule way. We also investigate the effects of mesoscale convective systems on the global circuit.
Rycroft, Michael J.; Harrison, R. Giles; Nicoll, Keri A.; Mareev, Evgeny A.
Using High Resolution Complex Electrical Conductivity Measurements of Heterogeneous Rocks
The complex electrical resistivity of a slab of Berea sandstone was measured using a four electrode probe in the frequency range of 1 Hz to 1 kHz. The measurements where made in the context of the development of a new high resolution methodology for the laboratory characterization of hydro-geophysical properties on core and field samples. Electrical conductivity maps with millimeter-scale resolution and measured at different pore fluid salinities are used to constrain dual conduction models (e.g. Waxman-Smits, 1968) that allow us to separate the contribution of electrical conduction through the pore fluid from surface conduction along mineral grain surfaces. Measured resistivity variations are observed to be structured in distinct layers at the scale of millimeters to centimeters and are well correlated with fine scale layering observed in thin section. The data is analyzed in conjunction with petrophysical maps of permeability and velocity variations. The maps of permeability, resistivity, and velocity all indicate that Berea sandstone contains measurable structural anisotropy at a variety of scales. The heterogeneities in petrophysical properties are in general rather weak, with permeability varying by a factor of 3 and velocity and resistivity varying by 7% and 19% respectively. Analyzed collectively, the data provides insights into the physical causes of the observed resistivity anomalies and allows us to interpret them as due to localized pore-scale variations in grain size, pore structure, and mineralogy. Correlations among these petrographic variables lead to the discovery that surface conductivity of the rock is negatively correlated with the conductivity due to the free electrolyte. Using this integrated petrophysical data-set, we build a predictive model of the meter-scale petrophysical properties that honors the intrinsic heterogeneity of the sample. The data and models are used as the foundation for a physically-based upscaling approach for understanding how petrophysical properties relate to flow and transport processes at scales difficult to measure in the laboratory. Through application of effective media and numerical models we show that the observed small-scale heterogeneity leads to anisotropy in electrical properties that correlates with anisotropy in relative permeability. The anisotropy is found to be a complex function of scale, salinity, and saturation.
Boitnott, G. N.; Bussod, G. Y.
Electrical conductivity of gold-implanted alumina nanocomposite
We have carried out ion implantation of gold into alumina ceramic substrates and measured the surface resistivity as a function of implantation dose. The Au ion energy was 40 keV and the dose spanned the range 2.7-8.9 � 1016 cm-2. Imaging of the implanted material by transmission electron microscopy revealed that the implanted gold self-assembles into nanoparticles, thus forming a gold-alumina nano-composite. The surface resistivity measurements were compared with the predictions of a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the Au nanoparticles. The electrical conductivity of a composite, near the critical conductor-insulator transition, is given by ? ? ?0(x-xc)t, where ?0 is the saturation conductivity for which the material still remains a composite, x is the normalized metal atom concentration of the conducting phase, xc is the critical concentration, or percolation threshold and t is the critical exponent. Excellent agreement was found between the experimental results and the predictions of the theory, and the results are consistent with prior related (but more limited) work. The percolation dose was 4.4 � 1016 cm-2, and the critical exponent obtained was t = 1.4 � 0.1. We conclude that the conductivity process is due to percolation and that the contribution from tunneling conduction is negligible.
Salvadori, M. C.; Teixeira, F. S.; Sgubin, L. G.; Cattani, M.; Brown, I. G.
Testing and Optimization of Electrically Conductive Spacecraft Coatings
This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.
Mell, R. J.; Wertz, G. E.; Edwards, D. L. (Technical Monitor)
Gas-Tolerant Device Senses Electrical Conductivity of Liquid
The figure depicts a device for measuring the electrical conductivity of a flowing liquid. Unlike prior such devices, this one does not trap gas bubbles entrained in the liquid. Usually, the electrical conductivity of a liquid is measured by use of two electrodes immersed in the liquid. A typical prior device based on this concept contains large cavities that can trap gas. Any gas present between or near the electrodes causes a significant offset in the conductivity reading and, if the gas becomes trapped, then the offset persists. Extensive tests on two-phase (liquid/ gas) flow have shown that in the case of liquid flowing along a section of tubing, gas entrained in the liquid is not trapped in the section as long as the inner wall of the section is smooth and continuous, and the section is the narrowest tubing section along the flow path. The design of the device is based on the foregoing observation: The electrodes and the insulators separating the electrodes constitute adjacent parts of the walls of a tube. The bore of the tube is machined to make the wall smooth and to provide a straight flow path from the inlet to the outlet. The diameter of the electrode/insulator tube assembly is less than the diameter of the inlet or outlet tubing. An outer shell contains the electrodes and insulators and constitutes a leak and pressure barrier. Any gas bubble flowing through this device causes only a momentary conductivity offset that is filtered out by software used to process the conductivity readings.
O'Connor, Edward W.
Miniatuization of the flowing fluid electric conductivity loggingtec hnique
An understanding of both the hydraulic properties of the aquifer and the depth distribution of salts is critical for evaluating the potential of groundwater for conjunctive water use and for maintaining suitable groundwater quality in agricultural regions where groundwater is used extensively for irrigation and drinking water. The electrical conductivity profiles recorded in a well using the flowing fluid electric conductivity logging (FEC logging) method can be analyzed to estimate interval specific hydraulic conductivity and estimates of the salinity concentration with depth. However, irrigation wells that are common in agricultural regions have limited access into them because these wells are still in operation, and the traditional equipment used for FEC logging cannot fit through the small access pipe intersecting the well. A modified, miniaturized FEC logging technique was developed such that this logging method could be used in wells with limited access. In addition, a new method for injecting water over the entire screened interval of the well was developed to reduce the time required to perform FEC logging. Results of FEC logging using the new methodology and miniaturized system in two irrigation wells are also summarized.
Su, Grace W.; Quinn, Nigel W.T.; Cook, Paul J.; Shipp, William
Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration.
Normal and electrically stimulated PC12 cell cultures and the implantation of nerve guidance channels were performed to evaluate newly developed electrically conductive biodegradable polymer composites. Polypyrrole (PPy) doped by butane sulfonic acid showed a significantly higher number of viable cells compared with PPy doped by polystyrenesulfonate after a 6-day culture. The PC12 cells were left to proliferate for 6 days, and the PPy-coated membranes, showing less initial cell adherence, recorded the same proliferation rate as did the noncoated membranes. Direct current electricity at various intensities was applied to the PC12 cell-cultured conductive membranes. After 7 days, the greatest number of neurites appeared on the membranes with a current intensity approximating 1.7-8.4 microA/cm. Nerve guidance channels made of conductive biodegradable composite were implanted into rats to replace 8 mm of sciatic nerve. The implants were harvested after 2 months and analyzed with immunohistochemistry and transmission electron microscopy. The regenerated nerve tissue displayed myelinated axons and Schwann cells that were similar to those in the native nerve. Electrical stimulation applied through the electrically conductive biodegradable polymers therefore enhanced neurite outgrowth in a current-dependent fashion. The conductive polymers also supported sciatic nerve regeneration in rats. PMID:17209956
Zhang, Ze; Rouabhia, Mahmoud; Wang, Zhaoxu; Roberge, Christophe; Shi, Guixin; Roche, Phillippe; Li, Jiangming; Dao, L� H
Ionospheric electrical conductances produced by auroral proton precipitation
From incoherent scatter radar observations and space-borne particle detector data, it appears that energetic proton precipitation can sometimes, for some locations, be a major source of ionization in the auroral ionosphere and contribute significantly to the electrical conductances. Here we propose a simple parameterization for the Pedersen and Hall conductances produced by proton precipitation. The derivation is based on a proton transport code for computing the electron production rate and on an effective recombination coefficient for deducing the electron density. The atmospheric neutral densities and temperatures and the geomagnetic-field strength are obtained from standard models. The incident protons are assumed to have a Maxwellian distribution in energy with a mean energy in the 2-40 keV range and an energy flux Q0. The parameterized Pedersen and Hall conductances are functions of and Q0, as well as of the geomagnetic-field strength. The dependence on these quantities is compared with those obtained for electron precipitation and for solar EUV radiation. To add the contribution of proton precipitation to the total conductances for electrodynamic studies in auroral regions, the conductances produced by electron and proton precipitations can be combined by applying a root-sum-square approximation.
Galand, Marina; Richmond, Arthur D.
Transparent electrical conducting films by activated reactive evaporation
Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment.
Bunshah, Rointan (Los Angeles, CA); Nath, Prem (Troy, MI)
Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation is disclosed. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment. 1 fig.
Bunshah, R.; Nath, P.
Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes
Carbon nanotubes (CNT) based polymer composites have emerged as the future multifunctional materials in view of its exceptional mechanical, thermal and electrical properties. One of the major interests is to develop conductive polymer composites preferably at low concentration of CNT utilizing their high aspect ratio (L/D) for numerous applications, which include antistatic devices, capacitors and materials for EMI shielding. In this context, polymer blends have emerged as a potential candidate in lowering the percolation thresholds further by the utilization of 'double-percolation' which arises from the synergistic improvements in blend properties associated with the co-continuous morphology. Due to strong inter-tube van der Waals' forces, they often tend to aggregate and uniform dispersion remains a challenge. To overcome this challenge, we exploited sodium salt of 6-aminohexanoic acid (Na-AHA) which was able to assist in debundlling the multiwall carbon nanotubes (MWNT) through 'cation-{pi}' interactions during melt-mixing leading to percolative 'network-like' structure of MWNT within polyamide6 (PA6) phase in co-continuous PA6/acrylonitrile butadiene styrene (ABS) blends. The composite exhibited low electrical percolation thresholds of 0.25 wt% of MWNT, the lowest reported value in this system so far. Retention of 'network-like structure' in the solid state with significant refinement was observed even at lower MWNT concentration in presence Na-AHA, which was assessed through AC electrical conductivity measurements. Reactive coupling was found to be a dominant factor besides 'cation-{pi}' interactions in achieving low electrical percolation in PA6/ABS+MWNT composites.
Kulkarni, Ajit R.; Bose, Suryasarathi; Bhattacharyya, Arup R. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai-400076 (India)
Electrical Conductivity Imaging Using Controlled Source Electromagnetics for Subsurface Characterization
Controlled Source Audio-Frequency Magnetotellurics (CSAMT) is a frequency domain electromagnetic (EM) sounding technique. CSAMT typically uses a grounded horizontal electric dipole approximately one to two kilometers in length as a source. Measurements of electric and magnetic field components are made at stations located ideally at least four skin depths away from the transmitter to approximate plane wave characteristics of the source. Data are acquired in a broad band frequency range that is sampled logarithmically from 0.1 Hz to 10 kHz. The usefulness of CSAMT soundings is to detect and map resistivity contrasts in the top two to three km of the Earth's surface. Some practical applications that CSAMT soundings have been used for include mapping ground water resources; mineral/precious metals exploration; geothermal reservoir mapping and monitoring; petroleum exploration; and geotechnical investigations. Higher frequency data can be used to image shallow features and lower frequency data are sensitive to deeper structures. We have a 3D CSAMT data set consisting of phase and amplitude measurements of the Ex and Hy components of the electric and magnetic fields respectively. The survey area is approximately 3 X 5 km. Receiver stations are situated 50 meters apart along a total of 13 lines with 8 lines bearing approximately N60E and the remainder of the lines oriented orthogonal to these 8 lines. We use an unconstrained Gauss-Newton method with positivity to invert the data. Inversion results will consist of conductivity versus depth profiles beneath each receiver station. These 1D profiles will be combined into a 3D subsurface conductivity image. We will include our interpretation of the subsurface conductivity structure and quantify the uncertainties associated with this interpretation.
Miller, C. R.; Routh, P. S.; Donaldson, P. R.
Electrical Conductivity of Interacting Fermions. I. General Formulation
Electrical conductivity ?(?,T)of a lattice electron system due only to mutual Coulomb interaction is studied on the basis of the Fermi liquid theory, ? and T being the external frequency and the temperature, respectively. Based on the Kubo formula to respect the consistency between the selfenergyand the vertex corrections, a formulation of ?(?,T)is given in terms of memory function which is extended to the matrix form.In this formulation, it is explicitly demonstrated that,in the absence of Umklapp processes, T2-term in the resistivity vanishesas it should in spite of the fact that the total current is not conserved.
Maebashi, Hideaki; Fukuyama, Hidetoshi
Sinterability and electrical conductivity of calcium-doped lanthanum chromites
Calcium-doped lanthanum chromites, (La1-xCax) (Cr1-y Cay O3, have been synthesized to investigate effects of calcium doping on sinterability and electrical conductivity. X-ray diffractometric results have revealed that in addition to normal perovskites (La1-xCaxCrO3), chromium-deficient perovskites can exist as a single phase in the composition region 0.1 x < 0.3, although the deficit of chromium is small. These chromium-deficient perovskites show
N. Sakai; T. Kawada; H. Yokokawa; M. Dokiya; T. Iwata
Measurements of middle-atmosphere electric fields and associated electrical conductivities
A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.
Hale, L. C.; Croskey, C. L.; Mitchell, J. D.
Electrical conductivity anisotropy of partially molten peridotite under shear deformation
Recent ocean bottom magnetotelluric investigations have revealed a high-conductivity layer (HCL) with high anisotropy characterized by higher conductivity values in the direction parallel to the plate motion beneath the southern East Pacific Rise (Evans et al., 2005) and beneath the edge of the Cocos plate at the Middle America trench offshore of Nicaragua (Naif et al., 2013). These geophysical observations have been attributed to either hydration (water) of mantle minerals or the presence of partial melt. Currently, aligned partial melt has been regarded as the most preferable candidate for explaining the conductivity anisotropy because of the implausibility of proton conduction (Yoshino et al., 2006). In this study, we report development of the conductivity anisotropy between parallel and normal to shear direction on the shear plane in partial molten peridotite as a function of time and shear strain. Starting samples were pre-synthesized partial molten peridotite, showing homogeneous melt distribution. The partially molten peridotite samples were deformed in simple shear geometry at 1 GPa and 1723 K in a DIA-type apparatus with uniaxial deformation facility. Conductivity difference between parallel and normal to shear direction reached one order, which is equivalent to that observed beneath asthenosphere. In contrast, such anisotropic behavior was not found in the melt-free samples, suggesting that development of the conductivity anisotropy was generated under shear stress. Microstructure of the deformed partial molten peridotite shows partial melt tends to preferentially locate grain boundaries parallel to shear direction, and forms continuously thin melt layer sub-parallel to the shear direction, whereas apparently isolated distribution was observed on the section perpendicular to the shear direction. The resultant melt morphology can be approximated by tube like geometry parallel to the shear direction. This observation suggests that the development of conductivity anisotropy is caused by the realignment of partial melt (forming tube-like melt) parallel to shear direction in the silicate matrix. Finally, the high anisotropy of conductivity in the direction of plate motion can be well explained by anisotropic interconnection of melt in partially molten rocks at the top of asthenosphere, but not hydration of nominally anhydrous minerals. Therefore, our results provide the direct experimental evidence for supporting these geophysically observed high-conductivity anisotropy at the LAB and verify the validity of partial melting hypothesis (Yoshino et al., 2006; Naif et al., 2013). References Evans, R. L. et al. Geophysical evidence from the MELT area for compositional controls on oceanic plates. Nature 437, 249-252 (2005). Naif, S., Key, K., Constable, S. & Evans, R. L. Melt-rich channel observed at the lithosphere-asthenosphere boundary. Nature 495, 356-359 (2013). Yoshino, T., Matsuzaki, T., Yamashita, S. & Katsura, T. Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere. Nature 443, 973-976 (2006).
Zhang, B.; Yoshino, T.; Yamazaki, D.; Manthilake, G. M.; Katsura, T.
Electrical Modulation of the Local Conduction at Oxide Tubular Interfaces
Hetero-interfaces between complex oxides have sparked considerable interest due to their fascinating physical properties and offer new possibilities for next-generation electronic devices. The key to realize practical applications is the control through external stimulus. In this study, we take the self-assembled BiFeO3-CoFe2O4 hetero-interface as a model system to demonstrate the non-volatile electric control of the local conduction at the complex oxide tubular interface. The fundamental mechanism behind this modulation was explored based on static and dynamic conducting atomic force microscopy. We found the movement of oxygen vacancies in the BiFeO3-CoFe2O4 heterostructure is the key to drive this intriguing behavior. This study delivers a possibility of designing new device for next-generation electronic devices.
Hsieh, Ying-Hui [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Strelcov, Evgheni [ORNL] [ORNL; Jia-Ming, Liou [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Chia-Ying, Shen [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Yi-Chun, Chen [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Kalinin, Sergei V [ORNL] [ORNL; Ying-Hao, Chu [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan
Electrical modulation of the local conduction at oxide tubular interfaces.
Heterointerfaces between complex oxides have sparked considerable interest due to their fascinating physical properties and their offering of new possibilities for next-generation electronic devices. The key to realize practical applications is the control through external stimuli. In this study, we take the self-assembled BiFeO3-CoFe2O4 tubular interface as a model system to demonstrate the nonvolatile electric control of the local conduction at the complex oxide tubular interface. The fundamental mechanism behind this modulation was explored based on static and dynamic conductive atomic force microscopies. We found the movement of oxygen vacancies in the BiFeO3-CoFe2O4 heterostructure is the key to drive this intriguing behavior. This study delivers a possibility in developing next-generation electronic devices. PMID:24016142
Hsieh, Ying-Hui; Strelcov, Evgheni; Liou, Jia-Ming; Shen, Chia-Ying; Chen, Yi-Chun; Kalinin, Sergei V; Chu, Ying-Hao
Electrically conductive PEDOT coating with self-healing superhydrophobicity.
A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 � 10(-4) ?�m, but also displayed a water contact angle larger than 156� and a sliding angle smaller than 10�. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h. PMID:24702588
Zhu, Dandan; Lu, Xuemin; Lu, Qinghua
Stimulation of neurite outgrowth using an electrically conducting polymer
Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer�oxidized polypyrrole (PP)�has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(l-lactic acid) (PLA), and poly(lactic acid-co-glycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 ?m (n = 5643) compared with 9.5 ?m (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-co-glycolic acid).
Schmidt, Christine E.; Shastri, Venkatram R.; Vacanti, Joseph P.; Langer, Robert
Stimulation of neurite outgrowth using an electrically conducting polymer.
Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer--oxidized polypyrrole (PP)--has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(L-lactic acid) (PLA), and poly(lactic acid-co-glycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 micron (n = 5643) compared with 9.5 micron (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-co-glycolic acid). PMID:9256415
Schmidt, C E; Shastri, V R; Vacanti, J P; Langer, R
Stimulation of Neurite Outgrowth Using an Electrically Conducting Polymer
Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer--oxidized polypyrrole (PP)--has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(L-lactic acid) (PLA), and poly(lactic acid-coglycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 ? m (n = 5643) compared with 9.5 ? m (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-coglycolic acid).
This thesis reports the development of a new method for measuring electrical of nanoscale objects, called conductance imaging atomic force microscopy (CIAFM), and reports the results of measurements performed on carbon nanotube networks and nanotube junctions. We introduce CIAFM, a method that combines atomic force microscopy and local conductance measurements. The method is implemented by using a tuning fork as cantilever and a solid metal tip. It excels at taking large amounts of measurements at high data density, making it equally suitable to analyze transitions on the nanometer scale or large systems such as networks. The method is thoroughly characterized. CIAFM is applied to measure the local conductances of a carbon nanotube network on the nanometer scale to characterize current paths through the network. The extent of metallic connections is investigated and found to be the principal contributor to current flow on the macroscopic scale. Finally, we analyze the length scale of conductance decay around carbon nanotube junctions. We find indication for ballistic current and exponential decay of ballistic current over a distance of several microns.
Stadermann, Michael
DNA-templated nanowires: morphology and electrical conductivity.
DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates. PMID:24614835
Watson, Scott M D; Pike, Andrew R; Pate, Jonathan; Houlton, Andrew; Horrocks, Benjamin R
Thermophysical Properties of Liquid Te: Density, Electrical Conductivity, and Viscosity
The thermophysical properties of liquid Te, namely, density, electrical conductivity, and viscosity, were determined using the pycnometric and transient torque methods from the melting point of Te (723 K) to approximately 1150 K. A maximum was observed in the density of liquid Te as the temperature was increased. The electrical conductivity of liquid Te increased to a constant value of 2.89 x 10(exp 5 OMEGA-1m-1) as the temperature was raised above 1000 K. The viscosity decreased rapidly upon heating the liquid to elevated temperatures. The anomalous behaviors of the measured properties are explained as caused by the structural transitions in the liquid and discussed in terms of Eyring's and Bachiskii's predicted behaviors for homogeneous liquids. The Properties were also measured as a function of time after the liquid was coded from approximately 1173 or 1123 to 823 K. No relaxation phenomena were observed in the properties after the temperature of liquid Te was decreased to 823 K, in contrast to the relaxation behavior observed for some of the Te compounds.
Li, C.; Su, C.; Lehoczky, S. L.; Scripa, R. N.; Ban, H.; Lin, B.
Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon
These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.
Baker, D.F.
�N�rdlinger Ries� is a meteorite crater in the Bavarian �Alb� of Germany that was formed 15 million years ago, and subsequently filled with salty water. Evaporation resulted in an approximately 300 meter thick layer of young, highly conductive sediments. Audio-frequency Magnetotelluric (AMT) and geoelectric depth sounding (VES) techniques were used to analyze the electrical properties of these sediments. The apparent resistivities measured by the two methods are different, which can be explained by vertical electrical anisotropy (horizontal layering). Applying a joint forward modelling technique with resistivity variations found by a Monte Carlo method results in a best fit model containing a large number of layers, while separate inversions of the two data sets yield 3-layer models. Comparisons of the coefficient of anisotropy with drilling core samples demonstrate the reliability of the results. One difficulty of the AMT method is the low signal-to-noise ratio, because of the source�s deadband. Some suggestions for an �intelligent� processing are presented. Kerch (this session) is employing the result of the integrated conductivity as an input for 3D modelling of collected MT data.
K�hler, A.; Bahr, K.
Electric conductivity-tunable transparent flexible nanowire-filled polymer composites: orientation control of nanowires in a magnetic field.
Cobalt compound nanowires were dispersed in a transparent nonconductive polymer film by merely stirring, and the film's transparency and electrical conductivity were examined. This composite film is a unique system in which the average length of the nanowires exceeds the film's thickness. Even in such a system, a percolation threshold existed for the electric conductivity in the direction of the film thickness, and the value was 0.18 vol%. The electric conductivity value changed from ?1 � 10(-12) S/cm to ?1 � 10(-3) S/cm when the volume fraction exceeded the threshold. The electric conductivity apparently followed the percolation model until the volume fraction of the nanowires was about 0.45 vol %. The visible light transmission and electric conductivity of the composite film of about 1 vol % nanowires were 92% and 5 � 10(-3) S/cm, respectively. Moreover, the electric conductivity in the direction parallel to the film surface did not depend on the amount of the dispersed nanowires, and its value was about 1 � 10(-14) S/cm. Even in a weak magnetic field of about 100 mT, the nanowires were aligned in a vertical and parallel direction to the film surface, and the electric conductivity of each aligned composite film was 2.0 � 10(-2) S/cm and 2.1 � 10(-12) S/cm. The relation between the average wire length and the electric conductivity was examined, and the effect of the magnetic alignment on that relation was also examined. PMID:21623632
Nagai, Takayuki; Aoki, Nobuyuki; Ochiai, Yuichi; Hoshino, Katsuyoshi
Acidosis slows electrical conduction through the atrio-ventricular node
Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 � 7.9 to 166.1 � 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37�C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 � 5.2 to 174.9 � 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis.
Nisbet, Ashley M.; Burton, Francis L.; Walker, Nicola L.; Craig, Margaret A.; Cheng, Hongwei; Hancox, Jules C.; Orchard, Clive H.; Smith, Godfrey L.
Imaging in electrically conductive porous media without frequency encoding
Understanding multi-phase fluid flow and transport processes under various pressure, temperature, and salinity conditions is a key feature in many remote monitoring applications, such as long-term storage of carbon dioxide (CO2) or nuclear waste in geological formations. We propose a low-field NMR tomographic method to non-invasively image the water-content distribution in electrically conductive formations in relatively large-scale experiments (�1 m3 sample volumes). Operating in the weak magnetic field of Earth entails low Larmor frequencies at which electromagnetic fields can penetrate electrically conductive material. The low signal strengths associated with NMR in Earth's field are enhanced by pre-polarization before signal recording. To localize the origin of the NMR signal in the sample region we do not employ magnetic field gradients, as is done in conventional NMR imaging, because they can be difficult to control in the large sample volumes that we are concerned with, and may be biased by magnetic materials in the sample. Instead, we utilize the spatially dependent inhomogeneity of fields generated by surface coils that are installed around the sample volume. This relatively simple setup makes the instrument inexpensive and mobile (it can be potentially installed in remote locations outside of a laboratory), while allowing spatial resolution of the order of 10 cm. We demonstrate the general feasibility of our approach in a simulated CO2 injection experiment, where we locate and quantify the drop in water content following gas injection into a water-saturated cylindrical sample of 0.45 m radius and 0.9 m height. Our setup comprises four surface coils and an array consisting of three volume coils surrounding the sample. The proposed tomographic NMR methodology provides a more direct estimate of fluid content and properties than can be achieved with acoustic or electromagnetic methods alone. Therefore, we expect that our proposed method is relevant for geophysical applications, such as for monitoring CO2 injections in saline aquifers or detecting water leakage into nuclear waste deposit sites installed in electrically conductive formations.
Lehmann-Horn, J. A.; Walbrecker, J. O.
Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites
The use of multiphase polymer blends provides unique morphologies and properties to reduce the percolation concentration and increase conductivity of carbon-based polymer composites. These systems offer improved conductivity, temperature stability and selective distribution of the conductive filler through unique morphologies at significantly lower conductive filler concentration. In this work, the kinetic and thermodynamic effects on a series of multiphase conductive polymer composites were investigated. The polymer blend phase morphology, filler distribution, electrical conductivity, and rheological properties of CB-filled PP/PMMA/EAA conductive polymer composites were determined. Thermodynamic and kinetic parameters were found to influence the morphology development and final composite properties. The morphology and CB distribution were found to be kinetically driven when annealed for a short period of time following the shear-intensive mixing process, whereas the three-phase polymer blend morphology is driven by thermodynamics when given sufficient time under high temperature annealing conditions in the melt state. At short annealing times, the CB distribution was influenced by the compounding sequence where the CB was added after being premixed with one of the polymer phases or directly added to the three phase polymer melt, but again was thermodynamically driven at longer annealing times with the CB migrating to the EAA phase. The resistivity was found to decrease by a statistically significant amount to similar levels for all of the composite systems with increasing annealing time, providing evidence of gradual phase coalescence to a tri-continuous morphology and CB migration. The addition of CB via the PP and EAA masterbatch results in significantly faster percolation and lower resistivity compared to when added direct to the system during compounding after 30 minutes annealing by a statistically significant amount. Dynamic oscillatory shear rheology using small-amplitude oscillations was used to probe for differences in the tri-continuous morphology and attempt to characterize the CB distribution with annealing time. Minor differences were observed in the PP/PMMA/(EAA-CB) as a function of annealing time, while the rheological behavior was not observed to be significantly different for the other multiphase composites as a function of annealing, nor for the compounding sequence after the same annealing time.
Brigandi, Paul James
Spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction
The cultivation of sugar cane in Brazil occupies a prominent place in national production chain, because the country is the main world producer of sugar and ethanol. Accordingly, studies are needed that allow an integrated production and technified, and especially that estimates of crops are consistent with the actual production of each region. The objective of this study was to determine the spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction. The field experiment was conducted at an agricultural research site located in Goiana municipality, Pernambuco State, north-east of Brazil (Latitude 07 � 34 '25 "S, Longitude 34 � 55' 39" W). The surface of the studied field is 6.5 ha, and its mean height 8.5 m a.s.l. This site has been under sugarcane (Saccharum officinarum sp.) monoculture during the last 24 years and it was managed burning the straw each year after harvesting, renewal of plantation was performed every 7 years. Studied the field is located 10 km east from Atlantic Ocean and it is representative of the regional landscape lowlands, whose soils are affected by salinity seawater, sugarcane plantations with the main economical activity. Soil was classified an orthic the Podsol. The productivity of cane sugar and electrical conductivity were measured in 90 sampling points. The productivity of cane sugar was determined in each of the sampling points in plots of 9 m2. The Apparent soil electrical conductivity (ECa, mS m-1) was measured with an electromagnetic induction device EM38-DD (Geonics Limited). The equipment consists of two units of measurement, one in a horizontal dipole (ECa-H) to provide effective measurement distance of 1.5 m approximately and other one in vertical dipole (ECa-V) with an effective measurement depth of approximately 0.75 m. Data were analyzed using descriptive statistics and geostatistical tools. The results showed that productivity in the study area reached values above 200 t ha-1, with higher values of productivity are concentrated in the region northern terrain. The maps of soil electrical conductivity (ECa-V and ECa-H) showed behavior similar to the productivity of cane sugar. The linear correlation showed values of 0.74 (yield x ECa-H) and 0.85 (yield x ECa-V). The adjusted semivariograms showed no similarity in the spatial pattern of pairs of semivariance. The electrical conductivity measured by electromagnetic induction has been shown as an important tool for predicting the productivity of sugar cane, however more studies are needed to determine the magnitude of the differences between such attributes.
Siqueira, Glecio; Silva, Jucicl�ia; Bezerra, Joel; Silva, Enio; Montenegro, Abelardo
Thermal and electrical conductivity of iron at Earth's core conditions
The power supplied to the geodynamo, measured by the heat-flux at the core-mantle boundary (CMB), places constraints on the evolution of Earth's core. Estimates of CMB heat-flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. Recently, we computed these conductivities at core conditions for liquid iron mixtures that fit the seismologically-determined core density and inner-core boundary density jump. Both conductivities were found to be 2-3 times higher than estimates in current use. Here we describe a reassessment of the power requirements for the geodynamo based on the revised conductivity values and new estimates of the mass diffusion coefficients for individual components of the mixtures. The adiabatic heat-flux at the CMB is found to be 15-16 TW at the CMB, higher than present estimates of CMB heat-flux based on mantle convection. A thermally stratified layer beneath the CMB appears unavoidable unless a very high present-day CMB heat-flux can be maintained, which requires a rapid CMB cooling rate and an inner core that is only a few hundred years old. We estimate stable layer thicknesses by computing the radial variation of thermal and compositional gradients for a range of plausible CMB heat-flux values and assuming that the base of the layer is defined by the condition for neutral buoyancy. Thermally stable layers spanning hundreds of kilometres are found for all cases except those where the inner core is very young. These calculations also suggest that compositional buoyancy may not be sufficient to overcome the large stabilising thermal gradient; any convection in the upper core must be driven by dynamical instabilities arising from convection deeper inside the core, or by lateral variations in CMB heat flow.
Davies, C. J.; Pozzo, M.; Gubbins, D.; Alfe, D.
Electrically conductive, optically transparent polymer/carbon nanotube composites
The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.
Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)
Spectroscopic and Electrical Conductivity Studies of Some Semicarbazide Hydrochloride Complexes
The infrared and electronic absorption spectra of semicarbazide hydrochloride and its complexes with anthracene, tetracyanoquinodimethane TCNQ, Na-fluorescein and cupferron were recorded in the regions 200-4000cm-1 and 200-400nm. The new bands that appeared in the complex spectra were assigned. The effect of the complex formation on the frequency and intensity of the active vibrational bands was also studied. The internal energy changes of the complexes were calculated in a new line of calculation to give a clear insight about the stability of the investigated complexes. The electrical conductivity of the complexes was measured in the temperature range 25-130�C. The activation energy E was calculated and discussed on the basis of the spectroscopic information.
Fadly, M.; El-Manakhly, H.
System and method for determining velocity of electrically conductive fluid
A flowing electrically-conductive fluid is controlled between an upstream and downstream location thereof to insure that a convection timescale of the flowing fluid is less than a thermal diffusion timescale of the flowing fluid. First and second nodes of a current-carrying circuit are coupled to the fluid at the upstream location. A current pulse is applied to the current-carrying circuit so that the current pulse travels through the flowing fluid to thereby generate a thermal feature therein at the upstream location. The thermal feature is convected to the downstream location where it is monitored to detect a peak associated with the thermal feature so-convected. The velocity of the fluid flow is determined using a time-of-flight analysis.
Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor); Markusic, Thomas E. (Inventor); Stanojev, Boris Johann (Inventor)
Formulation of electrically conductive thermal-control coatings
The development and formulation of electrically conductive thermal control coating was undertaken for use on the International Sun Earth Explorer spacecraft. The primary effort was to develop a coating with a bulk resistivity of less than 100,000 ohm/sqm, an optical absorptance of approximately 0.55, and a normal emittance of 0.90. The required stability in space called for a bulk resistivity of less than 100,000 ohm/sq m, an absorptance of less than 0.67, and a normal emittance of 0.90 after exposure to approximately 4 x 10 to the 16th proton/sq cm of solar-wind particles and 5300 equivalent sun-hours. These exposures represent 2 years of ISEE flight conditions. Both the unsuccessful formulation efforts and the successful use of oxide pigments fired at 1448 K are described. Problems relative to the reactivity of specific coating vehicles exposed to high humidity are discussed.
Polymeric salt bridges for conducting electric current in microfluidic devices
A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.
Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)
Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature
In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.
Parkin, C. W.
Thermal effects of electrically conductive deposits in melter
The radioactive waste processed by the Defense Waste Processing Facility melter at the Savannah river Site contains noble metal fission-products. Operation of waste-glass melters treating commercial power reactor wastes indicates that accumulation of noble metals on melter floors can lead to distortion of electric heating patterns, loss of power, and possible electrode damage. Changes in melter geometry have been developed in Japan and Germany to minimize these effects. The two existing melters for the US Department of Energy`s Defense Waste Processing Facility were designed in 1982, before this effect was known or had been characterized. Modeling and pilot scale tests are being conducted in the Integrated DWPF melter system to determine if the effect is significant for melters processing defense wastes, and if the effect can be diagnosed and corrected without significant damage or changes to the melter design. This document provides a discussion of these tests.
Choi, I.G.; Bickford, D.F.; Carter, J.T.
The radioactive waste processed by the Defense Waste Processing Facility melter at the Savannah river Site contains noble metal fission-products. Operation of waste-glass melters treating commercial power reactor wastes indicates that accumulation of noble metals on melter floors can lead to distortion of electric heating patterns, loss of power, and possible electrode damage. Changes in melter geometry have been developed in Japan and Germany to minimize these effects. The two existing melters for the US Department of Energy's Defense Waste Processing Facility were designed in 1982, before this effect was known or had been characterized. Modeling and pilot scale tests are being conducted in the Integrated DWPF melter system to determine if the effect is significant for melters processing defense wastes, and if the effect can be diagnosed and corrected without significant damage or changes to the melter design. This document provides a discussion of these tests.
Facile synthesis of boron nitride nanotubes and improved electrical conductivity.
A layer of catalyst film on substrate is usually required during the vapor-liquid-solid (VLS) growth of one-dimensional (1D) nanomaterials. In this work, however, a novel approach for synthesizing high-purity bamboo-like boron nitride (BN) nanotubes directly on commercial stainless steel foils was demonstrated. Synthesis was realized by heating boron and zinc oxide (ZnO) powders at 1200 degrees C under a mixture gas flow of nitrogen and hydrogen. The stainless steel foils played an additional role of catalyst besides the substrate during the VLS growth of the nanotubes. In addition, the electrical conductivity of the BN nanotubes was efficiently improved in a simple way by coating with Au and Pd nanoparticles. The decorated BN nanotubes may find potential applications in catalysts, sensors and nanoelectronics. PMID:20352730
Chen, Yongjun; Luo, Lijie; Zhou, Longchang; Mo, Libin; Tong, Zhangfa
Electrical conduction and dielectric studies of ZnO pellets
A series of Zinc Oxide pellets sintered at different temperatures was studied by means of dielectric spectroscopy in the wide frequency range of 1-106 Hz and temperature interval from -100 �C to 30 �C. Electrical conductivity was analysed using Jonsher's universal power law, and the values of s were found to decrease with the increase in temperature, which agrees well with the correlation barrier hopping (CBH) model. As the temperature increased, energy activation Edc became less than 0.39 eV and dc conductivity (?dc) values in the range of 1.9�10-14-9.7�10-10 ? m-1 were observed. The dielectric modulus showed ionic polarisation at the intermediate and high frequencies related to oxygen interstitial Oi, oxygen vacancy VO and Zinc interstitial Zni. At low frequency, it revealed a Maxwell-Wagner-Sillars relaxation with barrier heights of grain boundaries between 0.74 and 0.88 eV for all the studied pellets.
Chaari, Mariem; Matoussi, Adel
The Deep Electrical Conductivity Structure of the Dead Sea Basin
The left-lateral Dead Sea transform (DST) is a major transform fault separating the Arabian plate in the east from the African and Sinai plates in the west. It extends from the Red Sea rift to the Taurus collision zone in eastern Turkey, with a total length of more than 1000 km. During its evolution, the DST formed several deep sedimentary (pull-apart) basins, such as the Gulf of Aqaba / Eilat, the Lake Tiberias and the Dead Sea basin (DSB). The DSB is the largest basin along the transform valley and probably the largest of these structures on earth. The basin is 135km long, 20km wide and according to an interpretation of gravity data the basin's sedimentary fill is assessed to 10km thickness. Within the framework of the multi-disciplinary DESIRE (Dead Sea Integrated Research) project, several geophysical methods were applied to investigate the southern part of the DSB, including magnetotellurics (MT), active reflection and refraction seismic, aero-gravity, and passive seismology. The MT data were acquired at 150 stations in 2006 along a 120 km long, approximately east-west oriented profile. Resistivity models obtained from two-dimensional inversion of the MT data reveal several robust features: Beneath the Dead Sea, extending to a depth of approximately 3 km, we observe extremely low electrical resistivity (0.1- 0.5 ? m). Embedded within this structure and located beneath the Al-Lisan Peninsula we observe a localized high resistivity body (> 100 ? m), which is interpreted as the Al Lisan salt diapir. The lateral boundaries of the DSB are clearly expressed in the resistivity model as abrupt changes from moderately low (~20 ? m) to high resistivity (> 1000 ? m) at depths of 3 and 4 km under the eastern and western segment of the profile, respectively. The locations of the boundaries coincide with the surface traces of the eastern and western border faults. Furthermore, the 2D model images two conductive layers beneath both, the eastern and western segments of the profile at varying depth ranges. Based on hydro-geological information the location and depth extent of these conductive layers appear to coincide with a shallow and a deeper aquifer. With our electrical conductivity model it is possible to delineate the saline/fresh water interface, particularly at the eastern shoreline of the Dead Sea. The border faults appear to prevent cross-fault fluid flow of the Dead Sea brines.
Meqbel, N. M.; Ritter, O.; Weckmann, U.; Becken, M.; Munoz, G.
Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies
Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.
Duba, AL
Thermal and electrical conductivity of iron at Earth's core conditions.
The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core. PMID:22495307
Pozzo, Monica; Davies, Chris; Gubbins, David; Alf�, Dario
Investigation of thermal conductivity, viscosity, and electrical conductivity of graphene based nanofluids
Stable and well dispersed functionalized graphene-ethylene glycol (EG) + distilled water nanofluids having graphene nano-sheets (GnS) volume concentration between 0.041 and 0.395 vol. % are prepared without any surfactant. Graphene nano-sheets are prepared from high purity graphite powder by Hummers method followed by exfoliation and reduction by hydrogen gas. Thus, obtained hydrogen exfoliated graphene (HEG) is then functionalized using acid. The graphene nano-sheets are characterized using XRD, TEM, Raman spectroscopy, and FTIR spectroscopy. Thermal conductivity and viscosity measurements are performed both as a function of graphene loading and temperature between 10 and 70 �C. Thermal conductivity enhancement of ~15% for a loading of 0.395 vol. % f-HEG is observed at room temperature. The measured nanofluid's thermal conductivity is explained well in terms of the expression derived by Nan et al. (J. Appl. Phys. 81, 6692 (1997)), which considers matrix-additive interface contact resistance of mis-oriented ellipsoidal particles. The viscosity of the prepared f-HEG nanofluids and the base fluid (EG + distilled water) displays non-Newtonian behaviour with the appearance of shear thinning and nearly 100% enhancement compared to the base fluid (EG + DI water) with f-HEG loading of 0.395 vol. %. Known theoretical models for nanofluid's viscosity fail to explain the observed f-HEG volume concentration dependence of the nanofluid's viscosity. Temperature dependence of the studied nanofluid between 10 and 70 �C is explained well by the correlations proposed earlier for nanofluids with spherical nanoparticles. Electrical conductivity of the f-HEG nanofluids shows significant enhancement of ~8620% for 0.395 vol. % loading of f-HEG in a base fluid of 70:30 mixture of EG and distilled water.
Kole, Madhusree; Dey, T. K.
Soil electrical conductivity: Effects of soil properties and application to soil salinity appraisal
A model is discussed which relates bulk soil electrical conductivity (ECa) to volumetric water content (?W), electrical conductivity of the soil water (ECW), volumetric content of the solid phase (?S) and average electrical conductivity of the soil particles (ECS). Within the model a distinction is made between the water and dissolved salt present in the �immobile�; (fine pores) and �mobile�;
J. D. Rhoades; D. L. Corwin
Electrical conduction and glass relaxation in alkali- silicate glasses
Electrical response measurements from 1 Hz to 1 MHz between 50o and 540oC were made on potassium, sodium and lithium-silicate glasses with low alkali oxide contents. Conductivity and electrical relaxation responses for both annealed and air quenched glasses of the same composition were compared. Quenching was found to lower the dc conductivity, ?dc, and activation energy as well as increase the pre-exponential term when compared to the corresponding annealed glass of the same composition. All of the glasses exhibited Arrhenius behavior in the log ?dc against 1/T plots. A sharp decrease in ?dc was observed for glasses containing alkali concentrations of 7 mol% or less. The ?dc activation energy exhibited similar behavior when plotted as a function of alkali composition and was explained in terms of a mixture of the weak and strong electrolyte models. The depression angle for fits to the complex impedance data were also measured as a function of thermal history, alkali concentration and alkali species. These results were interpreted in terms of changes in the distribution of relaxation times. Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450o to 800oC, held isothermally for 20 min, and then quenched in either air or silicon oil. The complex impedance of both an annealed and the quenched samples were then measured as a function of temperature from 120o to 250oC. The ?dc was found to be remain unaffected by heat treatments below 450oC, to increase rapidly over an approximate 200oC range of temperatures that was dependent on cooling rate and to be constant for heat treatments above this range. This behavior is interpreted in terms of the mean structural relaxation time as a function of temperature and cooling rate near the glass transition temperature and glass transformation ranges. A more detailed definition for the transition and transformation temperatures and ranges was also provided.
Angel, Paul William
Electrical modification of a conductive polymer using a scanning probe microscope
We have demonstrated the electrical modification of a conductive polymer for data storage using a scanning probe microscope (SPM). A blend of polyaniline and polymethyl-methacrylate as the conductive polymer was spun on a silicon substrate to make a test specimen. The tip of a conductive SPM probe was placed in contact with the conductive polymer and electrical modification was carried
Takahito Ono; Shinya Yoshida; Masayoshi Esashi
Hopping conduction in high electric fields: three issues
Three issues concerning phonon-assisted hopping in molecularly doped polymers are considered. The first issue is whether Arrhenius jump rates in the vicinity of room temperature arise from single- phonon or small-polaronic hopping. It is concluded that Arrhenius hopping only occurs above low temperatures through small-polaronic hopping. Second, hopping in molecularly doped polymers is compared with small- polaronic hopping of other systems. Small-polaronic hopping typically occurs between similar chemical structures whose energies are relatively insensitive to their surroundings. Thus, disorder energies experienced by carriers are often modest, values of several hundredths of an eV are common. Nonetheless, the effects of large electric fields on carrier mobilities differ significantly among disordered systems. Data reported for molecularly doped polymers is unlike that for either transition- metal-oxide or chalcogenide glasses. In no case is high-field transport well understood. Finally, I stress that steady-state flow is driven by differences in sites` quasielectrochemical potentials (QECPs). With disorder, differences of QECPs are not simply related to the driving emf. Solution of the (nonlinear) stochastic equations for the QECPs shows that bottlenecks produced by disorder result in nonohmic conduction. Solving the linearized stochastic (disordered resistor network) equations underestimates bottleneck effects. Linearization is inappropriate when interest differences in the QECPs exceed [kappa]T.
Emin, D.
Effect of Electric Field on Conductivity and Vickers Hardness of an Al-Li Alloy
Static electric fields were applied on an aluminium-lithium alloy during solution treatment. The conductivity and Vickers hardness of the quenched Al-Li alloy is changed with the effect of electric field. The Vickers hardness increases with the applied electric field for a certain solutionizing time but decreases with the time under an electric field. In the absence of the electric field, the Vickers hardness and the conductivity increase synchronously, while reversed after electric field treatment. Positive and negative electric fields had the similar effect. The change of the local electron density in alloy caused by electric field is presented to explain the effect.
Liu, Bing; Chen, Da-Rong; Chen, Zheng; Wang, Yong-Xin; Li, Xiao-Ling
Fracture criterion for conductive cracks in soda-lime glass under combined mechanical and electrical loading
Fracture tests of electrically conductive cracks on pre-notched four-point bending soda-lime glass samples were conducted\\u000a under combined mechanical and electrical loading. The experimental results show that the critical stress intensity factor\\u000a at fracture is reduced if an electric field is applied, thereby indicating that the electric field makes contributions to\\u000a the fracture of conductive cracks. Base on the charge-free zone
Dong-Jun Yan; Hai-You Huang; Chi-Wai Cheung; Tong-Yi Zhang
The Wilkes subglacial basin eastern margin electrical conductivity anomaly
We have analyzed the deep conductivity structure at the transition between the Transantarctic Mountains (TAM) and the eastern margin of the WSB in NVL, by means of the GDS (Geomagnetic Deep Sounding) technique, in order to constrain the geodynamical interpretation of this antarctic sector. The TAM form the uplifted flank of the Mesozoic and Cenozoic West Antarctic Rift System. Structure of the TAM rift flank has been partially investigated with different geophysical approaches.The Wilkes Subglacial Basin is a broad depression over 400 km wide at the George V Coast and 1200 km long. Geology, lithospheric structure and tectonics of the Basin are only partially known because the Basin is buried beneath the East Antarctic Ice Sheet and is located in a remote region which makes geophysical exploration logistically challenging. Different authors have proposed contrasting hypothesis regarding the origin of the WSB: it could represent a region of rifted continental crust, or it may have a flexural origin or might represent an "extended terrane". Recently aerogeophysical investigations have demonstrated a strong structural control on the margin. Magnetovariational studies carried out at high geomagnetic latitudes are often hampered by source effects, mainly due to the closeness to the Polar Electrojet currents systems (PEJ). Its presence, in fact, makes the uniform magnetic field assumption, on which the magnetovariational methods are based on, often invalid, which outcome is a bias in the GDS transfer functions and to compromise the reliability of the inverted models. Data from the aforementioned campaigns have been then processed under the ISEE project (Ice Sheet Electromagnetic Experiment), aimed at evaluate and mitigate the bias effect of the PEJ on geomagnetic an magnetotelluric transfer functions at high geomagnetic latitudes, by means of suitable processing algorithms, developed upon a statistical analysis study on PEJ effects (Rizzello et al. 2013). Recent results allowed for a new processing of a wide dataset acquired during three different international Antarctic campaigns supported by the Italian Antarctic Project: the BACKTAM, WIBEM and WISE expeditions. The qualitative analysis of the induction arrows, in the period range 20-170 s, reveals an approximately 2D regional electrical conductivity pattern with a clear differentiation between the three Terrains crossed by the GDS transect we have re-analized: the Robertson Bay, the Bowers and the Wilson Terrain. Bi-dimensional conductivity models, jointly with magnetic and gravimetric profiles, suggest a differentiation of the investigated area in three crustal sectors separated by the Daniels Range and the Bowers Mts., in close relation with main known structural lineaments; to the West, a deep conductivity anomaly is associated with the transition to the Wilkes Subglagial Basin. We deem that such anomaly, together with the magnetic and gravimetric signatures, is compatible with an extensional regime in the eastern margin of the WSB. References Rizzello, D., Armadillo, E., Manzella, A."Statistical analysis of the polar electrojet influence on geomagnetic transfer functions estimates, over wide time and space scales". EGU 2013 General Assembly, Wien - poster presentation.
Rizzello, Daniele; Armadillo, Egidio; Ferraccioli, Fausto; Caneva, Giorgio
Measurement of Electrical Conductivity into Tomato Cultivation Beds using Small Insertion Type Electrical Conductivity Sensor Designed for Agriculture
Our group has studied on-site monitoring sensor for agricultural field. An electrical conductivity (EC) sensor had been fabricated using Si integrated circuit technology. EC information of solutions shows ion concentrations dissolving in water, and can be used as the index of nutrient concentration for plants. So, it is important to measure EC in real time and on site. Because our EC sensor (5mm�5mm in size) is smaller than other commercial ones (several centimeters), it is easy to insert and achieve measurement in rock wool. In this study, our sensor measured long term EC values in tomato cultivation soil and rock wool medium. At first, we calibrated a relationship between output voltages and EC values on the sensor. The sensor was confirmed about enough EC measurement range from 8 to 969mS/m. In long period measurement, the sensor was confirmed about continuous operation for over five months, and intermittent measurement for over a year. In measurement in the cultivation soil, the sensor indicated that water was kept and diffused in the soil. In contrast, it was found that water diffused without keeping in it in rock wool medium. We confirmed our small EC sensor is useful for on-site monitoring and analysis of solution concentration distribution in several kinds of cultivation bed in real time.
Kawashima, Kazuko; Futagawa, Masato; Ban, Yoshihiro; Asano, Yoshiyuki; Sawada, Kazuaki
Hygrothermal Stability of Electrical Contacts Made from Silver and Graphite Electrically Conductive Pastes
The hygrothermal stability of electrical contacts made from silver and graphite electrically conductive pastes is comparatively evaluated by measurement of the increase in contact electrical resistance during immersion in water at 15�C and 40�C. The pastes are silver paint, silver paint with a nonconductive epoxy overcoat, silver epoxy, and graphite colloid. Each electrical contact is made between a seven-strand tin-coated copper wire and the surface of a carbon fiber epoxy-matrix composite. Silver paint and graphite colloid penetrate the spaces among the 130-?m-diameter strands, but silver epoxy does not. Partly due to its low penetrability and the silver flake (15 ?m) preferred orientation, silver epoxy gives contacts of significantly higher resistance than silver paint. Graphite colloid is comparable to silver epoxy in the resistance. Among the four pastes, silver paint with an epoxy overcoat is most durable, though it gives slightly higher resistance than silver paint without epoxy. Silver epoxy is less durable than silver paint without an epoxy overcoat, particularly at 40�C, due to the low hygrothermal stability of epoxy. Graphite colloid is even less durable than silver epoxy, due to its being water based.
Wang, Shoukai; Pang, Dick S.; Chung, D. D. L.
Nonlocal dc electrical conductivity of a Lorentz plasma in a stochastic magnetic field
The stochastic wandering of magnetic field lines allows momentum of even perfectly magnetized electrons to be transported across the mean B. We include this effect, along with the usual acceleration and scattering terms, in a spatially one-dimensional Boltzmann equation for the electron distribution function. For an electric field E/sub parallel/ (along local B) which varies versus position normal to B, the momentum transport leads to a nonlocal electrical conductivity. We apply the formalism to sheared, force-free magnetoplasmas, in which the E/sub parallel/ gradient is caused by variable twisting of B with respect to an externally applied uniform E. We examine in particular the experimentally documented phenomenon of field-aligned current density j/sub parallel/>0 in regions of the sheared magnetic field where E/sub parallel/roughly-equal0 or even E/sub parallel/<0. This phenomenon is in apparent violation of Ohm's law. Under suitable conditions of stochasticity and collisionality, we find that the spatial structure and temporal persistence of these force-free configurations can be directly caused by electron-momentum transport. This result is derived solely on the basis of electron dynamics. In contrast to fluid-turbulent models, our kinetic derivation requires no hypothetical ''plasma dynamo'' and no conjecture on the decay rates of magnetic helicity versus magnetic energy.
Jacobson, A.R.; Moses, R.W.
The electrically detected magnetic resonance microscope: Combining conductive atomic force microscopy with electrically detected magnetic resonance
We present the design and implementation of a scanning probe microscope, which combines electrically detected magnetic resonance (EDMR) and (photo-)conductive atomic force microscopy ((p)cAFM). The integration of a 3-loop 2-gap X-band microwave resonator into an AFM allows the use of conductive AFM tips as a movable contact for EDMR experiments. The optical readout of the AFM cantilever is based on an infrared laser to avoid disturbances of current measurements by absorption of straylight of the detection laser. Using amorphous silicon thin film samples with varying defect densities, the capability to detect a spatial EDMR contrast is demonstrated. Resonant current changes as low as 20 fA can be detected, allowing the method to realize a spin sensitivity of 8 � 10^6spins/?Hz at room temperature.
Klein, Konrad; Hauer, Benedikt; Stoib, Benedikt; Trautwein, Markus; Matich, Sonja; Huebl, Hans; Astakhov, Oleksandr; Finger, Friedhelm; Bittl, Robert; Stutzmann, Martin; Brandt, Martin S.
Preparation and characterization of highly electrically and thermally conductive polymeric nanocomposites
The conducting polymers and polymeric composites have attracted considerable attention in recent years because of their potential applications in advanced technologies, for example, in antistatic coatings, electromagnetic shielding. The introduction of electrically conductive fillers such as graphite, carbon black, metal and metal oxide powders into the polymeric matrix is a promising approach to fabricate electrically conductive polymeric materials. The recent
Volkan �e�en; I. �zdemir; Alparslan Turgut; Igor Krupa; Maria Omastova; Igor Novak
Electrical conductivity as an indicator of iron reduction rates in abiotic and biotic systems
Although changes in bulk electrical conductivity (?b) in aquifers have been attributed to microbial activity, ?b has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction experiments of increasing biological complexity. To quantify reaction rates, we propose composite reactions that incorporate the stoichiometry of
Aaron Regberg; Kamini Singha; Ming Tien; Flynn Picardal; Quanxing Zheng; Jurgen Schieber; Eric Roden; Susan L. Brantley
Mechanism of electrical conductivity in an irradiated polyimide
A polyimide was exposed to 1.0 MeV electron radiation. The radiation-induced radical density and dc conductivity were measured at various post-irradiation times. The radiation-induced radical density was found to be correlated to the increased dc conductivity through a hopping model of conductivity. The post-irradiation radical species were identified.
Ries, H. R.; Harries, W. L.; Long, S. A. T.; Long, E. R., Jr.
Determinantal quantum theory of d.c. electrical conductivity
the quantum calculation of the d.c. electrical conductivity for an electron system is reconsidered by using an improved form of the long-time solution of the density matrix. The starting time-evolution equation which is written as a linear system in the Liouville space of discrete quantum states, is first solved in terms of Cramer's determinants and next suitably adapted to tranport problems. The calculation of the statistical average of the many-body current density, in the presence of scattering potential, is carried out in the thermodynamic limit, using a characteristic property of collision matrices introduced earlier by van Hove as the so-called ?-singularity. In contrast to previous methods based on kinetic equations solved by perturbations, Kubo's theory, or Mori type memory functions, the resolution of an integral equation, initially included in Cramer's formulae, is no longer required. Among its major advantages, the method succeeds in overcoming the well known zero frequency divergent behaviour of the conductivity. It also yields an explicit expression of an effective relaxation time which is just constructed out of those diagonal transition sequences responsible for self-energy effects in van Hove's theory. This expression which only assumes the randomization of phases of initial states can be used to get tractable expansions in powers of the collision potential. Its range of validity is limited by the effect of collisions on equilibrium statistics, which is shown to be negligible within the Peierls criterion, hbar / tau ll ?, tau being the relaxation time and ? the Fermi energy. Finally, the comparison of the present approach with the elementary transport theory reveals that the relaxation time is close to the standard expression, even though the latter would be exactly recovered, in lowest order of collisions, only on disregarding divergent terms arising beyond second order. Le calcul quantique de la conductivit� en courant continu d'un syst�me d'�lectrons est reconsid�r� � l'aide d'une solution am�lior�e pour la matrice densit�. L'�quation d'�volution utilis�e est d'abord �crite comme un syst�me lin�aire dans l'espace de Liouville des �tats quantiques discrets, r�solue � l'aide de d�terminants de Cramer et convenablement adapt�e ensuite aux probl�mes de transport. Le calcul de la moyenne statistique de la densit� de courant, en pr�sence d'un potentiel de diffusion, est effectu� � la limite thermodynamique, en utilisant une propri�t� caract�ristique des matrices de collision, initialement introduite par van Hove sous le nom de singularit� ?. Contrairement aux m�thodes pr�c�dentes, bas�es sur les �quations cin�tiques r�solues par perturbations, la th�orie de Kubo, ou l'utilisation de fonctions m�moire de type Mori, la r�solution d'une �quation int�grale, d�j� incluse dans les formules de Cramer, n'est plus n�cessaire. Parmi ses autres avantages majeurs, la m�thode est capable de r�soudre la divergence bien connue de la conductivit� lorsque la fr�quence tend vers z�ro. Elle fournit aussi une expression explicite d'un temps de relaxation effectif, construite pr�cis�ment � partir des s�quences de transitions diagonales responsables des effets de self-�nergie dans la th�orie de van Hove. Cette expression qui ne suppose que la distribution de phase al�atoire des �tats d'�quilibre initiaux, peut �tre utilis�e pour obtenir des d�veloppements maniables en puissances du potentiel de collision. Son domaine de validit� n'est limit� que par l'effet des collisions sur la statistique d'�quilibre, qui se r�v�le n�gligeable dans les limites du crit�re de Peierls hbar / tau ll ?, o� tau est le temps de relaxation et ? l'�nergie de Fermi. Finalement, la comparaison avec la th�orie �l�mentaire montre que le temps de relaxation est proche de l'expression classique, mais ne pourrait s'y identifier compl�tement, � l'ordre le plus bas des collisions, qu'en ignorant les divergences apparaissant au-del� du second ordre.
Fortini, A.
Investigation of a High Temperature Electrical Conductivity Device for Use with Thermal Image Heating.
The 'double-clamshell' imaging system has been successfully used to measure electrical conductivity of single crystal and polycrystalline aluminum oxide and pyrolytic boron nitride in the absence of impressed electric and magnetic fields. A furnace with a...
P. S. Schaffer H. A. Hobbs R. C. Folweiler
Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires.
Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on ...
R. A. Perkins
Electrical-stress-induced conductivity increase in SrTiO3 films
The charge transport of polycrystalline SrTiO3 films doped with Cr is investigated by means of temperature- and electric-field-dependent current measurements. In particular, the effect of electrical stress on the conduction mechanism is analyzed to understand the forming process of samples exhibiting resistance-switching phenomena. The temperature dependence of the conductivity can be described with the variable-range hopping model. The electrical-stress-induced conductivity
S. Karg; G. I. Meijer; D. Widmer; J. G. Bednorz
Intercomponent momentum transport and electrical conductivity of collisionless plasma
Based on the Lenard-Balescu equation, the interaction integral for the intercomponent momentum transfer in a two-component, collisionless plasma is evaluated in closed form. The distribution functions of the electrons and ions are represented in the form of nonisothermal, displaced Maxwellians corresponding to the 5-moment approximation. As an application, the transport of electrical current in an electric field is discussed for infrasonic up to sonic electron-ion drift velocities.
Wilhelm, H. E.
Phase Diagrams of Electric-Fduced Aggregation in Conducting Colloids
Under the application of a sufficiently strong electric field, a suspension may undergo reversible phase transitions from a homogeneous random arrangement of particles into a variety of ordered aggregation patterns. The surprising fact about electric-field driven phase transitions is that the aggregation patterns, that are observed in very diverse systems of colloids, display a number of common structural features and modes of evolution thereby implying that a universal mechanism may exist to account for these phenomena. It is now generally believed that this mechanism emanates from the presence of the long-range anisotropic interactions between colloidal particles due to their polarization in an applied field. But, in spite of numerous applications of the electric-field-driven phenomena in biotechnology, separation, materials engineering, chemical analysis, etc. our understanding of these phenomena is far from complete. Thus, it is the purpose of the proposed research to develop a theory and then test experimentally, under normal- and low-gravity conditions, the accuracy of the theoretical predictions regarding the effect of the synergism of the interparticle electric and hydrodynamic interactions on the phase diagram of a suspension. The main results from our theoretical studies performed to-date enable one to trace how the variations of the electrical properties of the constituent materials influence the topology of the suspension phase diagram and then, by using an appropriate phase diagram, to evaluate how the electric-field-induced transformations will depend on the frequency and the strength of the applied field.
Khusid, B.; Acrivos, A.
Electrical conductivity of diopside: evidence for oxygen vacancies
Impedance spectra for two natural single crystals of diopside were obtained at 800 to 1300??C and 1-bar pressure over the frequency range 0.001 Hz to 100 kHz in a system closed to all components but oxygen. At both higher and lower fO2 values, no fO2 dependence of conductivity was observed, indicating the presence of different conduction mechanisms. At temperatures less than 1000??C, the activation energy is 1.3 eV, also suggesting a different conduction mechanism. Thus, at least four regimes are necessary to describe the conductivity of this diopside in T-fO2 space. The approximately -1/(7 ?? 1) value of d(log ??)/d(log fO2) in a high-temperature geologic region suggests a reaction by which oxygen vacancies control the conductivity. This relatively pure diopside is much less conducting than olivine or orthopyroxene. A second diopside with greater Fe content but otherwise similar in composition to the near-end-member diopside, is more conducting, has a smaller activation energy (1.0 eV) over the range 1050 to 1225??C, and shows only a weak negative fO2 dependence; suggesting that oxygen vacancies are present but are not the dominant defect in controlling the conductivity. -from Authors
Huebner, J. S.; Voigt, D. E.
Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films
A simple and effective approach to prepare conductive polystyrene/carbon nanofiber (PS/CNF) nanocomposite films via a solution dispersion method is presented. Inexpensive CNF, which has a structure similar to multi-walled carbon nanotubes, is chosen as a nanofiller in this experiment to achieve conductivity in PS films. A good dispersion is�
Sun, Luyi; O'Reilly, Jonathan Y.; Tien, Chi-Wei; Sue, Hung-Jue
Size Effect Variation of the Electrical Conductivity of Metals
This paper records experiments and theoretical work concerned with the variation of conductivity with size in metals. Experimental results for the conductivity in thin wires of pure sodium of varying diameter in the absence of a magnetic field and also in the presence of longitudinal and transverse magnetic fields are given. Using the general statistical theory of metals the variation
D. K. C. MacDonald; K. Sarginson
Breakdown Characteristics of an Isolated Conducting Object in a Uniform Electric Field.
A laboratory experiment was conducted to determine the physical processes involved in the electrical breakdown of a particular spark gap arrangement. The gap consists of an isolated conducting ellipsoid located midway between two large flat electrodes. Gr...
M. G. Grothaus T. F. Trost
Influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles: application to the modeling of their aggregation kinetics.
Titanium dioxide nanoparticles (TiO2 NPs) are extensively used in consumer products. The release of these NPs into aquatic environments raises the question of their possible risks to the environment and human health. The magnitude of the threat may depend on whether TiO2 NPs are aggregated or dispersed. Currently, limited information is available on this subject. A new approach based on DLVO theory is proposed to describe aggregation kinetics of TiO2 NPs in aqueous dispersions. It has the advantage of using zeta potentials directly calculated by an electrostatic surface complexation model whose parameters are calibrated by ab initio calculations, crystallographic studies, potentiometric titration and electrophoretic mobility experiments. Indeed, the conversion of electrophoretic mobility measurements into zeta potentials is very complex for metal oxide nanoparticles. This is due to their very high surface electrical conductivity associated with the electromigration of counter and co-ions in their electrical double layer. Our model has only three adjustable parameters (the minimum separation distance between NPs, the Hamaker constant, and the effective interaction radius of the particle), and predicts very well the stability ratios of TiO2 NPs measured at different pH values and over a broad range of ionic strengths (KCl aqueous solution). We found an effective interaction radius that is significantly smaller than the radius of the aggregate and corresponds to the radius of surface crystallites or small clusters of surface crystallites formed during synthesis of primary particles. Our results confirm that DLVO theory is relevant to predict aggregation kinetics of TiO2 NPs if the double layer interaction energy is estimated accurately. PMID:23806415
Bouhaik, Izzeddine Sameut; Leroy, Philippe; Ollivier, Patrick; Azaroual, Mohamed; Mercury, Lionel
Investigation of DC electrical conductivity of chalcogenide glasses
The various Se-S-Zn chalcogenide glasses have been prepared by the standard melt-quenching technique. Their amorphous state was verified by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The temperature dependence of DC conductivity was measured in the temperature range 323-358K, in order to identify the conduction mechanism and to observe the doping effect of Zn on Se-S. In this temperature range, DC conductivity increases from 10-8 to 10-7 S/m with an increase in Zn concentration.
Sanjay; Kishore, N.; Kundu, R. S.; Agarwal, A.; Dhankhar, S.
Electrochemical intercalation and electrical conductivity of graphite fibers
Lamellar compounds of graphite fibers were prepared by electrochemical intercalation. The dependence of the electrical resistance on the intercalate concentration was determined by a quasi simultaneous method. A factor 30 decrease of the relative fiber resistance was obtained with fluorosulfuric acid.
Besenhard, J. O.; Fritz, H. P.; Moehwald, H.; Nickl, J. J.
Surface Electrical Conductivity of Single Crystal Spinel in Cesium Vapour.
The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Pr...
P. Agnew J. L. Ing
High frequency electrical conduction block of the pudendal nerve
A reversible electrical block of the pudendal nerves may provide a valuable method for restoration of urinary voiding in individuals with bladder-sphincter dyssynergia. This study quantified the stimulus parameters and effectiveness of high frequency (HFAC) sinusoidal waveforms on the pudendal nerves to produce block of the external urethral sphincter (EUS). A proximal electrode on the pudendal nerve after its exit
Narendra Bhadra; Niloy Bhadra; Kevin Kilgore; Kenneth J. Gustafson
Electrical Conductance of Bolted Copper Joints for Cryogenic Applications
We present the results of electric contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate and systematic data display a rather small dispersion, and may be a useful tool for cryogenic applications like pulse-tubes, dilution refrigerators and nuclear refrigerators.
Blondelle, F.; Sultan, A.; Collin, E.; Godfrin, H.
Electrical and Optical Properties of Conducting Polymer - Fullerene and Conducting Polymer - Carbon Nanotube Composites
Various novel photo-physical properties such as a drastic photoluminescence quenching and photoconductivity enhancement and a photo-induced enhancement of low-field microwave absorption due to a highly effective photo-induced electron transfer have been observed in various conducting polymers doped with fullerenes and also acceptor-type molecules and conducting polymers. New types of junction devices utilizing effective charge separation at the interface of conducting
Katsumi Yoshino; Hirotake Kajii; Hisashi Araki; Tooru Sonoda; Hiroyoshi Take; Sergey Lee
Thermal characterisation of electrically conductive adhesive flip-chip joints
In this paper, we present simulation results of the thermal characteristics of epoxy-based anisotropically conductive adhesive (ACA) flip-chip joints. The results are compared with the thermal characteristics of isotropically conductive adhesive (ICA) flip-chip joints, soldered flip-chip modules and wire bonded modules. The simulated thermal parameters are the overall thermal resistance from the active chip surface down to the substrate as
Anders Sihlbom; Johan Liu
Enhancement of Electrical Conductivity in Plasticized Chitosan Based Membranes
Plasticized natural macromolecules-based polymer electrolyte samples were prepared and characterized. The plasticization of chitosonium acetate with glycerol increased the ionic conductivity value from 3.0 � 10 S\\/cm to 1.1 � 10 S\\/cm. The conductivity temperature relationship of the samples exhibits either VTF or Arrhenius type depending on the glycerol concentration in the sample. The dielectric studies evidencing the relaxation process
R. I. Mattos; E. Raphael; S. R. Majid; A. K. Arof; A. Pawlicka
Dielectric properties and electrical conduction in yttrium iron garnet (YIG)
The dielectric properties (dielectric constant and loss) of a single crystal of yttrium iron garnet (Y3Fe5O12) were measured in the temperature range 77�725 K and in the frequency range 100 Hz-1 MHz. AC conductivity was derived from\\u000a dielectric constant and loss. DC conductivity was measured in the temperature range 30�725 K. Thermoelectric power (TEP) was\\u000a measured from 77�800 K. On
Lalitha Sirdeshmukh; K Krishna Kumar; S Bal Laxman; A Rama Krishna; G Sathaiah
Electrical Conductance Cell Assembly for Precise Measurements with Carbonates, Oxides, and Fluorides up to 1000�C
A conductance cell assembly is reported of the capillary design with a cell constant sufficiently high to permit precise electrical conductance measurements with the standard type precision conductance bridge circuits. Important features are the use of single crystal grade MgO for construction of the capillaries that determine the resistance for the electrolyte in the conductance cell, and the use of
George J. Janz; Max R. Lorenz
Physical property and electrical conductivity of electroless Ag-plated carbon fiber-reinforced paper
The addition of a large amount of conductive filler to paper in order to increase electrical conductivity adversely affects some physical properties of the paper. Hence, it is desirable that conductive paper can be manufactured by adding only a small amount of conductive filler. Reinforced paper was manufactured by adding (1) electroless Ag-plated carbon fiber or (2) activated carbon fiber
Joon Jang; Seung Kon Ryu
Measurements of the Electrical Conductivities of Air over Hot Water.
Measurements of the conduction current between two electrodes in air over recently boiled water have been interpreted by Carlon as indicating that the humidified air became highly conductive and that large numbers of ions were produced in the air after it was saturated with water vapor. These interpretations have been questioned because it is possible that the insulators used in the high-humidity experiments allowed leakage currents to flow and these were treated as though they were conduction currents through the air.We repeated these measurements with the use of a conventional, Gerdien cylinder conductivity-measuring apparatus that had insulators heated to temperatures above the dew point of the water vapor in the air being measured so that the insulators maintained high resistances. The results from the heated Gerdien cylinder experiments contradict the suggestions of high conductivities in humid air, for the measured conductivities of air were repeatedly observed to decrease by about 50% when recently boiled, hot water was brought in contact with the air.
Moore, C. B.; Vonnegut, B.
Simultaneous measurements of thermal conductivity and electrical conductivity of micro-machined Silicon films
The in-plane effective thermal conductivity of free-standing Si thin films with periodic micropores was measured at -100 to 0 �C. The Si thin films with micropores were prepared from silicon-on-insulator (SOI) wafers by standard microfabrication processes. The dimensions of the free-standing Si thin films were 200?m�150?m�2 ?m, with staggered 4 ?m pores having an average pitch of 4 mm. The Si thin film serves both as a heater and thermometer. The average temperature rise of the thin film is a function of its in-plane thermal conductivity. The effective thermal conductivity was calculated using a simple one-dimensional heat conduction model. The measured thermal conductivity was much lower than that expected based on classical model evaluations. A significant phonon size effect was observed even in the microsized structures, and the mean free path for phonons is very long even at the room temperature.
Hagino, H.; Kawahara, Y.; Goto, A.; Miyazaki, K.
Electrical Characterization and Morphological Studies of Conducting Polymer Nanofibers
Doped polyaniline blended with poly(ethylene oxide) has been electrospun in air to give fibers with diameters in the range 3 nm 200 nm. These fibers were captured on wafers of degenerately doped Si/SiO2 by placing the wafer in the path of the fiber jet formed during the electrospinning process. Individual fibers were contacted using shadow mask evaporation and were also captured on prepatterned wafers. Fibers having diameters greater than 100 nm show a slight increase in the conductivity as compared to the bulk film, while fibers with diameters less than 30 nm had lower conductivity than the bulk. Data on Scanning Conductance Microscopy along the length of individual fibers will be presented. For fibers where the diameter was not uniform, we found that below a certain diameter ( approx.15 nm) the fiber was less conducting as compared to thicker diameter fibers. Dependence of the fiber conductivity on a gate bias is underway and these results will also be presented.
Pinto, N. J.; Zhou, Y. X.; Freitag, M.; Johnson, A. T.; MacDiarmid, A. G.; Mueller, C. H.; Theofylaktos, N.; Robinson, D. C.; Miranda, F. A.
Advantages of Fused Deposition Modeling for Making Electrically Conductive Plastic Patterns
There are many applications where electrically conductive plastic patterns are needed. The most usual way to make electrically conductive patterns is coating a plastic part by a thin layer of metal. It's well known the different procedures for metalizing plastic parts but most of them aim to obtain either aesthetic or functional metallic coating with high level of adherence, finishing
M. D. Monzon; N. Diaz; A. N. Benitez; M. D. Marrero; P. M. Hernandez
A review of laboratory measurements of the electrical conductivity of rocks and minerals
The use of laboratory measurements of electrical conductivity for rocks and minerals at high temperatures and pressures helps us to interpret magnetotelluric measurements and allows us to obtain further information about various physical and mineralogical properties of the Earth's interior. A survey of recent laboratory measurements of electrical conductivity of rocks and minerals at high temperatures and pressures is outlined.
Marcela Latovikov�
Polyaniline\\/zeolite LTA composites and electrical conductivity response towards CO
Electrical conductivity response of polyaniline\\/zeolite composites towards CO is investigated in terms of dopant type, dopant concentration, zeolite LTA content and zeolite pore size. Both MA and HCl doped polyanilines respond with comparable magnitudes towards CO; the latter responses are slightly smaller for the same doping level. Addition of zeolite 4A reduces the electrical conductivity response but improves the sensitivity
C. Chuapradit; L. Ruangchuay Wannatong; D. Chotpattananont; Piyanoot Hiamtup; A. Sirivat; J. Schwank
Electrical conductivity and dielectric properties of PMMA\\/expanded graphite composites
PMMA\\/expanded graphite (EG) composites were prepared by direct solution blending of PMMA with the expanded graphite filler. Electrical conductivity and dielectric properties of the composites were measured by a four-point probe resistivity determiner and a dielectric analyzer (DEA). Interestingly, only 1 wt.% filler content was required to reach the percolation threshold (?) of transition in electrical conductivity from an insulator
Wenge Zheng; Shing-Chung Wong
Electrical Conductivity Of Diamond Up To 1,200 Degrees C
Report discusses measurements of electrical conductivities of two synthetic diamond films, three synthetic diamondlike films, and two natural type IIa diamonds at temperatures from ambient to 1,200 degrees C. Measurements performed to compare electrical conductivities of state-of-the-art diamond films with those of natural insulating diamond, particularly at temperatures above 700 degrees C.
Vandersande, Jan W.; Zoltan, Leslie D.
Measurement of soil water content and electrical conductivity by time domain reflectometry: a review
Non-destructive measurement of soil water content and electrical conductivity has been desired for many years. Recent development of time domain reflectometry (TDR) enables us to simultaneously obtain soil water content and electrical conductivity using a single probe with a minimal disturbance of soil. Research on water and solute transport in porous media using TDR has flourished in the last few
K. Noborio
Electrical Conductivity of Solid Oxides. Xi. La2O3-CaO System.
In view of the previously investigated electrical conductivity of a solid solution with the fluorite-type lattice, the subject of this study was to determine the effect of the change of the crystal structure of the electrolyte on electrical conductivity. ...
S. F. Palguev Z. S. Volchenkova
Electrical Conductivity during XPS of Heated PMMA: Detection of Core Line and Valence Band Tacticity Effects.
Electrical conductivity during the XPS of approximately 100 nm thick films of PMMA on silicon was induced by heating to above 100 degrees C. Rapid x-ray induced depolymerization set in at about the same temperature. The electrical conductivity allowed acq...
G. Beamson D. T. Clark D. S. L. Law
Thermal conductivity of KH2PO4 in an applied electric field
The thermal conductivity of single-crystal KH2PO4 has been measured from 10 K to room temperature in an applied electric field. The applied field causes a small increase in the thermal conductivity at temperatures close to the ferroelectric-to-paraelectric transition. The results are compared with the dielectric polarization KH2PO4 in an applied electric field.
Fengqi Lin; Da-Ming Zhu
Lin, Fengqi; Zhu, Da-Ming
Electrical conductivity measurements of a high-pressure seeded air plasma
The magnetohydrodynamic (MHD) accelerator has been considered as a device for augmenting the performance of hypersonic test facilities. A requirement for operating an MHD accelerator is that the gas must have sufficient electrical conductivity to allow current flow at reasonable applied electrode voltage. Therefore, knowledge of flow properties such as the electrical conductivity, electron density and current discharge characteristics in
Hsuan-Cheng Liu
Electrical behaviour of conducting silicon rubber under short high current stress
The conducting silicon rubber was highly stressed by means of voltage impulses in order to investigate the electric behaviour of this material. A specific value of electric load-carrying capacity was observed. Below this value material exhibits resistive character and constant electrical properties, however, above this value the material is damaged and can not be used in practical application. The explanation
A. Napierala
Local electrical conduction in polycrystalline La-doped BiFeO? thin films.
Local electrical conduction behaviors of polycrystalline La-doped BiFeO3 thin films have been investigated by combining conductive atomic force microscopy and piezoelectric force microscopy. Nanoscale current measurements were performed as a function of bias voltage for different crystal grains. Completely distinct conducting processes and resistive switching effects were observed in the grain boundary and grain interior. We have revealed that local electric conduction in a grain is dominated by both the grain boundary and ferroelectric domain, and is closely related to the applied electric field and the as-grown state of the grain. At lower voltages the electrical conduction is dominated by the grain boundary and is associated with the redistribution of oxygen vacancies in the grain boundary under external electric fields. At higher voltages both the grain boundary and ferroelectric domain are responsible for the electrical conduction of grains, and the electrical conduction gradually extends from the grain boundary into the grain interior due to the extension of the ferroelectric domain towards the grain interior. We have also demonstrated that the conduction dominated by the grain boundary exhibits a much small switching voltage, while the conduction of the ferroelectric domain causes a much high switching voltage in the grain interior. PMID:23637078
Zhou, Ming-Xiu; Chen, Bo; Sun, Hai-Bin; Wan, Jian-Guo; Li, Zi-Wei; Liu, Jun-Ming; Song, Feng-Qi; Wang, Guang-Hou
Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion
Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al were slightly modified for intermediate temperatures in order to obtain fitting between experimental and simulated exploding wire radial expansion. Also, it was shown that the electrical conductivity results and the EOS evaluation differ significantly from the results obtained in nanosecond timescale experiments. Finally, it was found that underwater electrical W wire explosion is characterized by the appearance of non-uniformities along the z-axis of the wire. This phenomena adds uncertainty to the possibility of applying this type of experiments for evaluation of the electrical conductivity and EOS of W.
Sheftman, D.; Krasik, Ya. E.
Sheftman, D.; Krasik, Ya. E. [Physics Department, Technion, Haifa 32000 (Israel)
Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.
Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 �C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445
Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang
Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions
Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 �C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.
Relationship between microstructure, hardness and electrical conductivity of 2219 aluminium
A TEM study of unstretched, heat-treated aluminium alloy 2219 was performed with the aim of correlating the microstructure with hardness (H) and eddy current conductivity (C) data. Recently Chihoski has developed a new method of evaluating heat treatments of aluminium alloys by constructing in an H-C field a �sail� formed by a network of curved coordinate lines of quenching and
M. Natan; R. A. Chihoski
Electric Conduction in n-Type Germanium and Cadmium Sulfide.
The impurity conduction of n-type Ge and CdS is calculated via a previously developed theory for impurity bands in doped semiconductors. Rough agreement with experimental data over a wide range of impurity concentration is found. The comparison with AMO-M...
D. A. Ferreira I. C. Dacunhalima M. Fabbri
Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges
Conductive polymer composites require a threedimensional 3D network to impart electrical conductivity. A general method that is applicable to most polymers for achieving a desirable graphene 3D network is still a challenge. We have developed a facile technique to fabricate highly electrical conductive composite using vacuumassisted infusion of epoxy into graphene sponge GS scaffold. Macroscopic GSs were synthesized from graphene oxide solution by a hydrothermal method combined with freeze drying. The GSepoxy composites prepared display consistent isotropic electrical conductivity around 1Sm, and it is found to be close to that of the pristine GS. Compared with neat epoxy, GSepoxy has a 12ordersofmagnitude increase in electrical conductivity, attributed to the compactly interconnected graphene network constructed in the polymer matrix. This method can be extended to other materials to fabricate highly conductive composites for practical applications such as electronic devices, sensors, actuators, and electromagnetic shielding.
Li, Yuanqing; Samad, Yarjan Abdul; Polychronopoulou, Kyriaki; Alhassan, Saeed M.; Liao, Kin
Doping dependence of electrical and thermal conductivity of nanoscale polyaniline thin films
We performed simultaneous characterization of electrical and thermal conductivity of 55 nm thick polyaniline (PANI) thin films doped with different levels of camphor sulfonic acids (CSAs). The effect of the doping level is more pronounced on electrical conductivity than on thermal conductivity of PANIs, thereby greatly affecting their ratio that determines the thermoelectric efficiency. At the 60% (the molar ratio of CSA to phenyl-N repeat unit of PANI) doping level, PANI exhibited the maximum electrical and thermal conductivity due to the formation of mostly delocalized structures. Whereas polarons are the charge carriers responsible for the electrical conduction, phonons are believed to play a dominant role in the heat conduction in nanoscale doped PANI thin films.
Jin, Jiezhu; Wang, Qing; Haque, M. A.
Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids.
Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids. PMID:21711869
White, Steven Bryan; Shih, Albert Jau-Min; Pipe, Kevin Patrick
Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids
Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids.
Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2
High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.
Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook
Improving the electrical and mechanical behavior of electrically conductive paint by partial replacement of silver by carbon black
Partial replacement of silver particles by carbon black (low cost) in electrically conductive paint was found to decrease\\u000a the electrical resistivity and increase the scratch resistance of the resulting thick film, which is for use in electrical\\u000a interconnections. An effective carbon black content is 0.055 of the total filler volume. By using a total solid volume fraction\\u000a of 0.1969 and
Chia-Ken Leong; D. D. L. Chung
Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al
D. Sheftman; Ya. E. Krasik
Electrical Conductivity Images of South African Continental Collision Zones
Within the framework of the German-South African geo-scientific research initiative Inkaba yeAfrica several magnetotelluric (MT) field experiments were conducted along the Agulhas-Karoo transect in South Africa. This 600km long transect is designed to cross the Cape Fold Belt, the Namaqua-Natal Mobile Belt (NNMB), the Karoo Basin and the transition into the Kaapvaal Craton. At the same time, the transect crosses
U. Weckmann; O. Ritter; M. Becken; J. Pek; M. de Wit
Modeling the Time-dependent Changes in Electrical Conductivity of Basaltic Melts With Redox State
The electrical conductivity sigma is an efficient probe of mass transfer processes within silicate melts and magmas. Little attention has been given to the influence of redox state (fO2) on the melts conductivity. We present an experimental setup allowing electrical conductivity measurements for basaltic melts under variable fO2. We demonstrate a significant dependence of sigma with fO2, allowing to characterize
A. Pommier; F. Gaillard; M. Pichavant
Space charge and electrical conduction in maleic anhydride-grafted polyethylene
The space charge behavior such as charge distribution and electrical conduction of maleic anhydride grafted LDPE (LDPE-g-MAH) was investigated. Heterocharge was found in LDPE and it decreased with increasing MAH graft ratio in LDPE-g-MAH. Conduction currents also decreased with increasing MAH graft ratio. The relationship between the space charge behavior and the electrical conduction characteristics in LDPE-g-MAH is discussed
Seung Hyung Lee; Jung-Ki Park; Jae Hong Han; Kwang S. Suh
Measurement of Complex Electrical Conductivity of Metallic Powders in a Sealed Tube
We studied the method of complex-electrical-conductivity measurement for powders placed in a sealed tube at microwave and millimeter-wave frequencies, using a cavity perturbation technique. We applied this technique to a molecular superconductor K3C60, whose electrical conduction is well known in single crystals, and reproduced the metallic conductivity with the magnitude of 0.5-1.2 mOmegacm at 20 K which is in good
Atsutaka Maeda; Ryoji Matsuo; Ryotaro Inoue; Haruhisa Kitano; Taishi Takenobu; Yoshihiro Iwasa; Tadaoki Mitani
Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites
The electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites were measured as a function of oxygen partial pressure (Po2) and temperature, and the results were discussed in light of defect chemistry. The electrical conductivity was independent of Po2 and in proportion to the Sr-content at high Po2, while at low Po2, the conductivity decreased exponentially with decrease of
I. Yasuda; M. Hishinuma
Re-evaluation of electrical conductivity of anhydrous and hydrous wadsleyite
Recent laboratory electrical conductivity measurements of the main mantle constituent minerals have represented considerable efforts to determine the effects of water content on electrical conductivity. However, there are large discrepancies between the results of Yoshino et al. (2008a) and those of Dai and Karato (2009a) on hopping conduction and the effects of water on the electrical conductivity of wadsleyite. To investigate the cause of these discrepancies, the electrical conductivity of anhydrous and hydrous wadsleyite were newly measured under low and high temperature conditions by impedance spectroscopy. The conductivity values of dry wadsleyite aggregates with less than 2 ppm H2O by weight were similar to those for hopping conduction reported by Yoshino et al. (2008a) and distinctly higher than those of Dai and Karato (2009a). For hydrous wadsleyite, at temperatures below 1000 K, the electrical conductivity in an Arrhenius plot was repeatable along the heating-cooling paths and was similar to the results of Yoshino et al. (2008a). The impedance spectrum in the complex impedance plane of hydrous wadsleyite showed a semicircular shape, and the infrared spectrum did not show any shape change after the conductivity measurements. In contrast, when the temperature exceeds 1000 K, the electrical conductivity in an Arrhenius plot showed higher activation enthalpy. The impedance spectra were greatly distorted and the impedance arc contained at least two relaxation processes. This shape is similar to those reported by Dai and Karato (2009a) who measured the conductivity above 1000 K. The infrared spectra showed a large contribution from molecular water after conductivity measurements, suggesting significant dehydration during the conductivity measurements. In summary, the results obtained from conductivity measurements at higher temperatures (>1000 K) do not represent the proton conduction in the grain interior.
Yoshino, Takashi; Katsura, Tomoo
DC electrical conductivity of silicon carbide ceramics and composites for flow channel insert applications
High purity chemically vapor-deposited silicon carbide (SiC) and 2D continuous SiC fiber, chemically vapor-infiltrated SiC matrix composites with pyrocarbon interphases were examined. Specifically, temperature dependent (RT to 800 �C) electrical conductivity and the influence of neutron irradiation were measured. The influence of neutron irradiation on electrical properties appeared very strong for the SiC of this study, typically resulting in orders lower ambient conductivity and steeper temperature dependency of this conductivity. For the 2D composites, through-thickness (normal to the fiber axis') electrical conductivity was dominated by bypass conduction via interphase network at relatively low temperatures, whereas conduction through SiC constituents dominated at higher temperatures. Through-thickness electrical conductivity of neutron-irradiated 2D SiC composites with thin PyC interphase, currently envisioned for flow channel insert application, will likely in the order of 10 S/m at the appropriate operating temperature. Mechanisms of electrical conduction in the composites and irradiation-induced modification of electrical conductivity of the composites and their constituents are discussed.
Katoh, Y.; Kondo, S.; Snead, L. L.
Carbon nanotube grease with enhanced thermal and electrical conductivities
A stable and homogeneous grease based on carbon nanotubes (CNTs, single-wall and multi-wall) in polyalphaolefin oil has been\\u000a produced without using a chemical surfactant. For example, for a 11�wt% (7�vol%) single-wall CNT (diameter 1�2�nm, length\\u000a 0.5�40�?m) loading, the thermal conductivity (TC) of the grease shows a 60�70% increase compared to that for no nanotube loading.\\u000a In addition, the grease is
Haiping Hong; Dustin Thomas; Andy Waynick; Wenhua Yu; Pauline Smith; Walter Roy
Tunable single-photon heat conduction in electrical circuits
We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor-insulator-normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.
Jones, P. J.; Huhtam�ki, J. A. M.; Partanen, M.; Tan, K. Y.; M�tt�nen, M.
Electrically conductive and mechanically elastic titanium nitride ceramic microsprings.
The structural and functional characterizations of titanium nitride (TiN) advanced ceramic microsprings (CMSs), with a coil diameter of several micrometers and synthesized by chemical vapor deposition (CVD) were investigated by microscopy techniques. The CMSs were sufficiently mechanically elastic for extension to more than 1.3 times their original size, and they spontaneously contracted to their original state on releasing the tension. To explore their application to a microdevice, a method of manufacturing TiN-CMS microcircuit elements was developed. The I-V plots of the elements indicated that the CMSs were as conductive as metals. PMID:24738385
Yang, Shaoming; Chen, Xiuqin; Yamamoto, Kazuo; Iitake, Masanori; Nishio-Hamane, D; Sakai, Hideki; Abe, Masahiko
Simple Method for Estimating the Electrical Conductivity of Oxide Melts with Optical Basicity
The electrical conductivity of oxide melts is an important physicochemical property for designing the electric smelting furnaces. Although the data of many slag systems have been measured, the quantitative relationships of electrical conductivity to slag composition and temperature are still limited. In this article, a model is proposed based on the optical basicity corrected for the cations required for the charge balance of {{AlO}}_{ 4}^{ 5- } , in which Arrhenius Law is used to describe the relationship between electrical conductivity and temperature. In this model, the activation energy is expressed as a linear function of the corrected optical basicity. Successful applications to CaO-MgO-Al2O3-SiO2 and CaO-Al2O3-SiO2 systems indicate that this model can work well in the electrical conductivity estimation.
Zhang, Guo-Hua; Chou, Kuo-Chih
Electrostatic interaction of two unequal conducting spheres in uniform electric field
An image dipole method is employed to calculate the induced dipole moments of a pair of unequal-size conducting spheres subjected to a uniform electric field. Expressions for the dipole moments are given, involving the size ratio and separation of the spheres. Two typical cases are analyzed; two similar conducting spheres and two unequal conducting spheres with remarkable difference in size.
Zehui Jiang
Nature of surface electrical conductivity in natural sands, sandstones, and clays
The electrical conductivity of rocks results from conduction through the bulk solution occupying the pores and from surface conduction occurring at the fluid/grain interface. The nature of the surface electrical conductivity of shaly and clean sands and sandstones is examined. Surface conduction is characterized by the specific surface conductance which is the sum of three contributions: (i) Conduction within the electrical diffuse layer, which makes a negligible contribution to the total specific surface conductance, (ii) Conduction in the Stern layer, which is shown to vary significantly with the salinity of the pore fluid at low salinities (10-6 to 10-3 mol 1-1), but becomes independent of salinity at higher salinities, (iii) A mechanism operating directly on the mineral surface, independent of salinity, and perhaps associated with proton transfer. At salinities higher than 10-3 mol 1-1 and at 25�C, the specific surface conductance of quartz and clays is equal to 8.9�10-9 S and 2.5�10-9 S respectively. Equations describing the influence of surface conductivity and microstructure upon the macroscopic electrical conductivity of sands, sandstones, and shales are also developed.
Revil, A.; Glover, P. W. J.
Electrical conductivities of the freshly excised cerebral cortex in epilepsy surgery patients; correlation with pathology, seizure duration, and diffusion tensor imaging.
The electrical conductivities (sigma) of freshly excised neocortex and subcortical white matter were studied in the frequency range of physiological relevance for EEG (5-1005 Hz) in 21 patients (ages 0.67 to 55 years) undergoing epilepsy neurosurgery. Surgical patients were classified as having cortical dysplasia (CD) or non-CD pathologies. Diffusion tensor imaging (DTI) for apparent diffusion coefficient (ADC) and fractional anisotropy (FA) was obtained in 9 patients. Results found that electrical conductivities in freshly excised neocortex vary significantly from patient to patient (sigma = 0.0660-0.156 S/m). Cerebral cortex from CD patients had increased conductivities compared with non-CD cases. In addition, longer seizure durations positively correlated with conductivities for CD tissue, while they negatively correlated for non-CD tissue. DTI ADC eigenvalues inversely correlated with electrical conductivity in CD and non-CD tissue. These results in a small initial cohort indicate that electrical conductivity of freshly excised neocortex from epilepsy surgery patients varies as a consequence of clinical variables, such as underlying pathology and seizure duration, and inversely correlates with DTI ADC values. Understanding how disease affects cortical electrical conductivity and ways to non-invasively measure it, perhaps through DTI, could enhance the ability to localize EEG dipoles and other relevant information in the treatment of epilepsy surgery patients. PMID:16858632
Akhtari, M; Salamon, N; Duncan, R; Fried, I; Mathern, G W
A reversible electrical block of the pudendal nerves may provide a valuable method for restoration of urinary voiding in individuals with bladder-sphincter dyssynergia. This study quantified the stimulus parameters and effectiveness of high frequency (HFAC) sinusoidal waveforms on the pudendal nerves to produce block of the external urethral sphincter (EUS). A proximal electrode on the pudendal nerve after its exit from the sciatic notch was used to apply low frequency stimuli to evoke EUS contractions. HFAC at frequencies from 1 to 30 kHz with amplitudes from 1 to 10 V were applied through a conforming tripolar nerve cuff electrode implanted distally. Sphincter responses were recorded with a catheter mounted micro-transducer. A fast onset and reversible motor block was obtained over this range of frequencies. The HFAC block showed three phases: a high onset response, often a period of repetitive firing and usually a steady state of complete or partial block. A complete EUS block was obtained in all animals. The block thresholds showed a linear relationship with frequency. HFAC pudendal nerve stimulation effectively produced a quickly reversible block of evoked urethral sphincter contractions. The HFAC pudendal block could be a valuable tool in the rehabilitation of bladder-sphincter dyssynergia.