Reduction Kinetics of FeO-CoO Solid Solution by Hydrogen Gas

The reduction kinetics of the FeO-CoO solid solutions (Fe_0.8Co_0.2O, Fe_0.7Co_0.3O, and Fe_0.6Co_0.4O) by hydrogen gas has been investigated using the thermogravimetric technique. Isothermal experiments were carried out in the temperature range 573 to 973 K. The activation energies for the reduction were calculated from the results of the isothermal experiments, and a typical value for Fe_0.8Co_0.2O solid solution was 65.9 kJ/mol. The activation energy values were found to be higher than the corresponding values for FeO and CoO obtained earlier under identical reduction conditions. Fine Fe-Co alloy particles were obtained by carrying out the reduction experiments using a fluidized bed reactor with the parameters defined by the thermogravimetric results. The transmission electron microscope and laser particle sizer studies confirmed that the particle size of the synthesized alloys is in the range of 20 to 300 nm. By using vibrating sample magnetomer measurements, the saturation magnetization values (Ms) were evaluated to be 196 emu/g and the coercive field was 33 Oe for Fe_0.8Co_0.2