Consolidation behavior of Mo powder fabricated from milled Mo oxide by hydrogen-reduction

Abstract

Nano-sized Mo powder was synthesized by ball-milling and subsequent hydrogen-reduction of MoO3 powder. The crystalline size of the MoO3 powder was decreased to below 10 nm by a 20 h ball-milling process. Hygrometric measurement was performed to understand hydrogen-reduction behavior of MoO3 with different milling time. The peak temperature for the reduction was shifted to lower temperatures by increasing the milling time. The peak for the reaction Of MoO3 -> MoO2 was more effective than that for the reaction of MoO2 -> Mo. This result is due to the transformation steps for the reaction of MoO3 -> MoO2 take place via chemical vapor transport (CVT) by generation of a gaseous transport phase. After hydrogen-reduction at 800 degrees C, the crystalline size of the Mo powder was about 60 nm. The sinterability of the nano-sized Mo powder was considerably enhanced compared with that of a commercial Mo power.