Oxidation behavior of FeV2O4 and FeCr2O4 particles in the air: Nonisothermal kinetic and reaction mechanism

High-temperature oxidation behavior of ferrovanadium (FeV 2 O 4 ) and ferrochrome (FeCr 2 O 4 ) spinels is crucial for the application of spinel as an energy material, as well as for the clean usage of high-chromium vanadium slag. Herein, the nonisothermal oxidation behavior of FeV 2 O 4 and FeCr 2 O 4 prepared by high-temperature solid-state reaction was examined by thermogravimetry and X-ray diffraction (XRD) at heating rates of 5, 10, and 15 K/min. The apparent activation energy was determined by the Kissinger–Akahira–Sunose (KAS) method, whereas the mechanism function was elucidated by the Malek method. Moreover, in-situ XRD was conducted to deduce the phase transformation of the oxidation mechanism for FeV 2 O 4 and FeCr 2 O 4 . The results reveal a gradual increase in the overall apparent activation energies for FeV 2 O 4 and FeCr 2 O 4 during oxidation. Four stages of the oxidation process are observed based on the oxidation conversion rate of each compound. The oxidation mechanisms of FeV 2 O 4 and FeCr 2 O 4 are complex and have distinct mechanisms. In particular, the chemical reaction controls the entire oxidation process for FeV 2 O 4 , whereas that for FeCr 2 O 4 transitions from a three-dimensional diffusion model to a chemical reaction model. According to the in-situ XRD results, numerous intermediate products are observed during the oxidation process of both compounds, eventually resulting in the final products FeVO 4 and V 2 O 5 for FeV 2 O 4 and Fe 2 O 3 and Cr 2 O 3 for FeCr 2 O 4 , respectively.