Preparation of ultrafine/nanometer MoO2 via the hydrogen reduction of H2MoO5

Owing to the wide application of Mo in a range of fields, the performance requirements for molybdenum products and molybdenum alloys have increased in recent years. In this study, a novel process is developed for the production of the main component of molybdenum powder, namely MoO ₂. Subsequently, the thermal stability of the component is measured, and the reduction mechanism is determined to evaluate its effects on the particle size and morphology. Evidently, the H ₂MoO ₅ raw material is completely stripped of O ₂ ²⁻ following a two-step heat-absorption reaction at 247 °C to produce MoO ₃ grains with a needle-like structure. These needle-like grains exhibit a lower reduction temperature than commercial MoO ₃, enabling part of the reduction reaction to occur at 440 °C. Additionally, the reaction rate is higher, and the reaction time at the same temperature is approximately half that of the commercial MoO ₃. The reaction mechanism associated with the needle-like MoO ₃ is mainly governed by chemical vapor transport (CVT), which leads to greater morphological changes, and can effectively regulate the nucleation and growth of MoO ₂. A more dispersed ultrafine/nano-MoO ₂ powder with an average particle size of 200–700 nm could be successfully prepared at low temperatures by adjusting the reduction temperature of MoO ₃, and to reduce the reduction temperature. It was found that the MoO ₂ grains began to grow continuously along the one-dimensional direction under the combined effects of the CVT and gas–liquid–solid growth mechanisms, forming MoO ₂ grains with a unique stripe-like morphology. These results are expected to contribute to the production of high-quality molybdenum powder to satisfy the requirements of various research and application fields.