Study on oxidation mechanism and kinetics of MoO2 to MoO3 in air atmosphere

• The oxidation mechanism and kinetics of MoO2 to MoO3 in air atmosphere are investigated.
• The intermediate product Mo4O11 is formed when the oxidation temperature is above 810 K.
• When the temperature is lower than 779 K, MoO2 is oxidized directly to be MoO3.
• MoO3 has a tendency to form platelet-shaped when the oxidation temperature is high.

The oxidation mechanism and kinetics of MoO2 to MoO3 in air atmosphere from 750 K to 902 K have been investigated in the present work. These results show that temperature has significant effects on the oxidation process. It is found that the produced MoO3 has a tendency to form a big platelet-shaped particle and the surface appears to be smooth at the high reaction temperature (902 K); while at the low reaction temperature (750 K), the micrographs of final products MoO3 become rough and irregular. The intermediate product Mo4O11 will be formed only when the temperature is above 810 K. It is found that the oxidation reaction was controlled by the interface chemical reaction at the reaction interface (from MoO2 to Mo4O11) and diffusion (from Mo4O11 to MoO3), respectively, by using the dual-interface reaction model in the temperature range of 810 K to 902 K. While in the temperature range of 750 K to 779 K, the oxidation reaction (one-step reaction, from MoO2 to MoO3 directly) was controlled by the diffusion model.