Chemical synthesis and characterization of Fe0.65Ni0.35-MgO nanocomposite powders

Fe0.65Ni0.35-MgO nanocomposite powders containing approximately 11 wt.% of metallic phase were prepared by selective reduction of oxide solid solutions elaborated by thermal decomposition of mixed oxalic precursor The reduction behavior of the oxide solid solution calcinated at 800 degrees C was investigated by XRD, Fe-57 Mossbauer spectroscopy and TEM. These studies have revealed that a reduction temperature of 1300 degrees C is needed to obtain a high reduction rate and to prepare alloy particles of the desired composition. The metallic alloy particles dispersed in the MgO matrix have a bimodal size distribution: the larger ones (average size from 50 to 90 nm) are approximately spherical and are located at the surface of the MgO grains; the smaller ones (average size from 5 to 13 nm) are spherical or cubic and generally grow epitaxially inside the oxide grains. (C) 1997 Acta Metallurgica Inc.