Oxidation behavior of ferrovanadium spinel particles in air: Isothermal kinetic and reaction mechanism

The oxidation behavior of ferrovanadium spinel (FeV2O4), synthesized via high-temperature solid-state reaction, was investigated using thermogravimetry, X-ray diffractometry, and X-ray photoelectron spectroscopy over the temperature range of 450-700 degrees C. The results revealed that the oxidation process of FeV2O4 can be divided into three stages with the second stage being responsible for maximum weight gain due to oxidation. Three classical methods were employed to analyze the reaction mechanisms and model functions for distinct oxidation stages. The random nucleation and subsequent growth (A(3)) kinetic model was found to be applicable to both initial and secondary stage. The third stage of oxidation was consistent with the three-dimensional diffusion, spherical symmetry (D-3) kinetic mode. Both the model-function method and the model-free method were utilized to investigate the apparent activation energy of the oxidation reaction at each stage. It was found that the intermediates including Fe3O4, VO2, V2O3, and Fe2.5V7.11O16, played significant roles in the oxidation process prior to the final formation of FeVO4 and V2O5 through oxidation of FeV2O4.