In , the hydrothermal synthesis of magnetite nanoparticles, to be used in lithium-ion batteries, is exposed. "All the chemicals were of analytical grade and purchased from Shanghai Chemical Reagents. In a typical procedure, 5 mmol (NH4)2Fe(SO4)2•6H2O, 2.5 mmol hexamethylenetetramine, and 1 g sodium sulfate were dissolved in 30 ml distilled water. After stirring for 20 min, the homogeneous green solution was transferred into a 50 ml Teflon lined autoclave, … The autoclave was sealed and placed in an oven, heated at 90 °C for 24 h. After the reaction, the autoclave was cooled in air. The suspension was washed … and the resulting black precipitates finally were dried in an oven at 60 °C for 24 h" . A Micro-Raman spectrometer (Jobin Yvon LabRAM HR800 UV, YGA 532 nm) was used.