Study on Hydrogen Reduction of Ultrafine MoO₂ To Produce Ultrafine Mo

In the present study, the hydrogen reduction of ultrafine MoO 2 to produce ultrafine Mo powders has been carried out. It is found that ultrafine spherical Mo powders can be obtained when the reaction temperature is above 923 K, and the reduction reaction obeys the chemical vapor transport (CVT) mechanism. Whereas when the reduction temperature is below 883 K, the final products of Mo powders appear to have the same morphology as the initial materials MoO 2 . In this case, the reduction reaction obeys the pseudomorphic transport mechanism. It was found that when the temperatures are in the range of 923–1023 K, the rate-controlling step for the reduction reaction is interfacial chemical reaction. While in the range of 863–883 K, the rate-controlling step changes with the reduction extent: when the reduction extent is in the range of 0–0.8, it obeys the nucleation and growth model; when the reduction extent is in the range of 0.8–1, the diffusion model is obeyed.