The reaction between MoO2 and water-vapor is inevitable during the H2 reduction of MoO2, and this process has a significant influence on the physicochemical properties (such as morphology, size, dispersity, and inoxidizability) of the prepared Mo powder. In order to control the properties of Mo powder, the study of the volatilization reaction of MoO2 and water-vapor is necessary, and the parameters of reaction temperature, Ar carrier gas flow-rate and its dew-point, are mainly considered. The results showed that the volatilization loss of MoO2 was gradually increased with increasing the reaction temperature (from 900 to 1000°C) and Ar flow-rate (from 2 to 10 L/min), while the influence degree of reaction temperature was more significant; as to the parameter of Ar dew-point (from 40 to 80°C), the results showed that the volatilization loss of MoO2 was gradually decreased with the increase of its value, and they were all in the range of 9–11%. During the volatilization process, the formation of Mo-O-H transport phase was responsible for the volatilization loss, among those the gaseous species of MoO2(OH)2 and H2 dominated. The study also discovered that when the condensation temperature TCT > 473°C, Mo-O-H transport phase was mainly condensed into platelet-shaped α-MoO3; while when TCT below that temperature, spherical-shaped β-MoO3 was the main deposition phase.
Wang et al. (Sun,) studied this question.
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