Study on the preparations of Mo and W powders via carbothermal pre-reduction process of MoO3 or WO3

In this paper, ultrafine Mo (W) powders were obtained by a two-stage reduction process consisting of carbo-thermal pre-reduction of MoO3 (WO3) and deep hydrogen reduction. The increase of reaction time was conducive to reduce the residual carbon contents of carbothermally pre-reduced products without significantly affecting the particle sizes. The particle sizes of carbothermic reduction products of MoO3 and WO3 were 186-192 nm and 141-146 nm as increasing holding time from 1 h to 4 h, respectively, while the residual carbon contents decreased from 0.036 wt% to 0.025 wt%, as well as from 0.045 wt% to 0.032 wt%, respectively. In addition, with the decrease in particle size of carbon black from 200 to 300 nm to 50 nm, the particle sizes of carbothermic reduction products of MoO3 and WO3 were gradually decreased from 322 nm to 188 nm and from 261 nm to 146 nm, respectively, while their residual carbon contents were 0.025-0.028 wt%, as well as 0.028-0.031 wt%, respectively. After the deep hydrogen reduction of carbothermal reduction products, the residual carbon contents of finally obtained ultrafine Mo and W powders were further reduced.