Synthesis and Magnetic Properties of Nanocrystalline Fe-Ni Alloys During Hydrogen Reduction of NiFe2O4

Nickel ferrite (NiFe2O4) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of nickel oxide (NiO) and iron oxide (Fe2O3). The pressed pellets of NiFe2O4 were isothermally reduced in pure hydrogen at 800, 900, 1000 and 1100 degrees C. Based on thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and various reduction products were characterized by XRD, SEM, reflected light microscope and VSM to reveal the effect of hydrogen reduction on the composition, microstructure, magnetic properties and reaction kinetics of the produced Fe-Ni alloy. Complete reduction of the NiFe2O4 was achieved with synthesis of homogeneous nanocrystalline Fe-Ni alloys. Arrhenius equation with the approved mathematical formulations for a gas-solid reaction was applied for calculating the activation energy (E-a) values and detecting the controlling reaction mechanism.