Reduction of FeVO4 to synthesise nanocrystalline ferrovanadium alloy

Abstract

Iron(III) vanadate was prepared by calcination of a stoichiometric mixture of vanadium metal and iron oxide. Compacts of the FeVO4 produced were isothermally reduced in pure hydrogen at 400–800°C and the reduction behaviour and kinetics were studied based on the thermogravimetric analysis. The initial product and the reduction products were characterised by X-ray diffraction analysis, scanning electron microscope and vibrating sample magnetometry. The reduction reaction was found to be controlled by a gaseous diffusion mechanism. Nanocrystalline (73·2 nm) ferrovanadium with metallic iron was obtained after the reduction of FeVO4 at 600–800°C. The magnetic properties of Fe and FeV alloy were enhanced with increasing reduction temperature: coercivity decreased from 254 to 158·2 Oe with increasing reduction temperature from 400 to 800°C, whereas saturation magnetisation increased from 9·35 to 29·1 emu g−1.