Mechanism and kinetics of hydrogen reduction of ultrafine MoO2 for preparing ultrafine Mo powder

Abstract

In this study, ultrafine Mo powder was synthesized via hydrogen reduction of MoO2 at various temperatures for different durations. The outcomes indicated that the higher temperature (in the range of 650–900 °C) could effectively enhance the reaction rate, leading to a substantial reduction in the time needed to complete the reduction reaction. Nevertheless, the obtained ultrafine Mo powder exhibited little change in overall particle morphology, and basically retained the sheet shape of the precursor MoO2, attributed to the dominance of pseudomorphic transformation mechanism in the reduction process. Additionally, various phase compositions of the products were observed across diverse material layers, illustrating the impact of gaseous mass transfer in the material layer on the reduction reaction. Moreover, a comprehensive kinetic model incorporating the diffusion of gases within the material layer and the interfacial chemical reaction of single particle was introduced. The utilization of this model confirmed its effectiveness in accurately characterizing the reduction kinetics of ultrafine MoO2, with the extracted apparent activation energy of 74.5 kJ/mol.