Comparative synthesize of nanocrystalline Fe–Ni and Fe–Ni–Co alloys during hydrogen reduction of NixCo1−xFe2O4

Nickel cobalt ferrite (NixCo1−xFe2O4) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of nickel oxide, cobalt oxide and iron oxide. The produced powders of NixCo1−xFe2O4 were isothermally reduced in pure hydrogen at 800–1100 °C. Based on thermogravimetric analysis, the reduction behaviour of the synthesized ferrite and the kinetics reaction mechanism were studied. The initial ferrite powder and the various reduction products were characterized by XRD, SEM and reflected light microscope to reveal the effect of hydrogen reduction on composition, microstructure and magnetic properties of produced Fe–Nix–Co1−x alloy. Microstructure of partially and completely reduced samples was studied and the activation energy values were calculated from Arrhenius equation. The approved mathematical formulations for the gas solid reaction were applied to confirm the estimated rate controlling reaction mechanism. Complete reduction of NixCo1−xFe2O4 was achieved with synthesize of nanocrystalline Fe–Ni and Fe–Ni–Co alloys.