Microstructure, kinetics and mechanisms of nano-crystalline CuFe2O4 reduction in flowing hydrogen at 300–600°C for the production of metallic nano-wires

Copper ferrite was obtained by the thermal decomposition of acetate precursors. The powder mixture is then fired at 600 °C for 2 h. The fired powder is then pressed in form of pellets and sintered at 1000 °C for 6 h. The prepared nano-crystalline (220 nm) CuFe2O4 compacts were characterized by X-ray diffraction analysis, and reflected light microscope. Nano-crystalline CuFe2O4 were isothermally reduced in H2 flow at 300–600 °C, the reduction products were metallic nano-wires of iron (106 nm) and copper (56 nm) both of average length 10 μm. The isothermal reduction profiles obtained in this study show that a topochemical mode of reduction is done by which the reduction process proceeds. Microstructure of partially and completely reduced samples was studied and the activation energy values were calculated from Arrhenius equation. The activation energy of the initial stage was found to be 39.35 kJ/mol, the intermediate stage has an activation energy of 56.2 kJ/mol while that of the final stage is found to be 55.3 kJ/mol. The approved mathematical formulations for the gas solid reaction were applied and it was found that at the initial stages the reaction is controlled by the combined gaseous diffusion and interfacial chemical reaction mechanisms. On the other hand at the intermediate and final stages the mechanism by which the reduction process proceeds was found to be the interfacial chemical reaction.