Effect of type and parameters of synthesis on the properties of magnetite nanoparticles

In the present work magnetite nanopowders were synthesized by chemical precipitation using FeCl3 center dot 6H(2)O and FeCl2 center dot 4H(2)O (80 degrees C, maintaining 5 min-1 h) and decomposition of FeC2O4 (470 degrees C, in hydrocarbon and nitrogen media maintaining 2 h) and investigated by X-ray diffraction analysis, IR spectroscopy and Scanning electron microscopy. Specific surface area and magnetic properties (specific saturation magnetization and coercive force) were also evaluated. It was shown that the time of synthesis did not influence on the phase composition and nanopowder with specific surface area equal to 141 m(2)/g could be prepared using chemical precipitation method for 5 min. Thermal decomposition method was found to allow obtaining of nanopowders with the higher degree crystallinity. It was established that increasing time of chemical precipitation causes decreasing the specific saturation magnetization from to 62 down to 53.5 emu/g and coercive force from 18.1 down to 3.0 Oe. Thermal decomposition method significantly improve magnetic properties and allow to obtain magnetite nanopowder with the specific saturation magnetization 135 emu/g.