Study of difference in reaction and properties of molybdenum powders along hydrogen flow in hydrogen reduction of molybdenum oxides process

This study investigated the effect of water vapor partial pressure variations along the hydrogen flow direction on the phase transformation of molybdenum oxide (MoOx) and the properties of resulting molybdenum (Mo) powder. The results indicated that the reduction process of MoO3 → MoO2 → Mo exhibited variations in particle size, oxygen content, and morphology along the hydrogen flow directions. In both the first-stage and second-stage reduction processes, the reduction rates decreased by 1.7%/cm and 2.6%/cm at minimum hydrogen flow along the direction of hydrogen flow, respectively. And the average particle size of fully reduced Mo powder increased from 1.23 μm to 1.61 μm, whereas its oxygen content decreased from 1400 ppm to 1100 ppm. Besides, the increase in the hydrogen flow rate leads to reduced variations in reduction rates, average particle size, and oxygen content along the hydrogen flow direction. These findings lay the theoretical foundation for the industrial production and preparation of high-quality Mo powder.