Effect of temperature on reduction of nanocrystalline Fe2O3 into metallic iron

The synthesis of ultrafine magnetic material with large saturation magnetisation and high coercivity has received much attention, owing to its wide applications. The reduction of nanocrystalline Fe2O3 into metallic iron was studied. The iron oxide precursor was synthesised by thermal evaporation of iron acetate and then pressed into cylindrical shape compacts before being fired at 500 degrees C for 1 h in a muffle furnace. The prepared nanocrystalline Fe2O3 was characterised using X-ray diffraction analysis technique, reflected light microscope and scanning electron microscope. The reduction behaviour of nanocrystalline Fe2O3 in hydrogen atmosphere at 450-600 degrees C has been studied using thermogravimetric techniques. The reduction rate is controlled initially by the interfacial chemical reaction mechanism, while the solid state diffusion is the rate controlling mechanism at final stages. The reduction temperature has a great effect on physicochemical properties of produced metallic iron during reduction of nanocrystalline Fe2O3. Metallic iron was formed in nanosized grains of 100-200 nm, while grain growth and highly coalescence were observed at reduction temperatures higher than at firing temperatures. Diluted magnetic nanoiron metal was formed with Hc ranged from 25 to 94 Oe, Br from 0(.)5 to 1(.)8 emu g(-1) and Bs from 24(.)5 to 41(.)4 emu g(-1).