Phase Transitions and Morphology Evolutions during Hydrogen Reduction of MoO_3 to MoO_2

摘要

In the present work, studies of phase transitions and morphology evolutions during hydrogen reduction of MoO_3 to MoO_2 were carried out in the temperature range from 678 to 829 K. It was found that no intermediate phase was formed and MoO_2 was the unique detectable product during the reduction at 678 K. While above 713 K, an intermediate phase of Mo_4O_(11) was formed. The formation of Mo_4O_(11) was found to obey the consecutive mechanism under the experimental condition. Regarding the morphology evolution of MoO_2 during reduction, it was found that in the temperature range from 713 to 733 K, MoO_3 was firstly reduced to large spherical or oval Mo_4O_(11) grains, then to small spherical or oval MoO_2 ones. From 793 to 829 K, most of MoO_3 grains were firstly reduced to large plate-shaped Mo_4O_(11) grains, subsequently to small plate-shaped MoO_2 ones.