Oxidation mechanism and kinetics of TiB2 submicron powders in air

High-activity TiB2 submicron powders were synthesized via microwave-assisted carbothermal reduction, and their oxidation behavior at 550 degrees C-1000 degrees C for 0.5-1.5 h in air atmosphere was carried out by the isothermal oxidation test. The phase composition and microstructure evolution of the oxidation products were performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It was established that TiB2 submicron powders had been significantly oxidized at 550 degrees C, and the oxidation products were TiO2 and B2O3. Hexagonal plate-like TiB2 grains had been completely disappeared, and fragmented into uniform nano-scale spherical TiO2 particles after being oxidized at 1000 degrees C for 1 h, accompanied by the violent evaporation of B2O3 products at temperatures above 1000 degrees C. In addition, the corresponding oxidation kinetics was investigated by using a non-isothermal thermogravimetric (TG)-differential scanning calorimetry (DSC) technique. The results showed that the Mample power law (n = 1) was the most probable mechanism function, and the oxidation activation energy E of TiB2 submicron powders was 640.58 kJ/mol.