Study on the preparation of molybdenum silicides by the silicothermic reduction of MoS2.

In this paper, a novel process about the silicothermic reduction of molybdenum disulfide was proposed to prepare molybdenum silicides. This new method has a short process, which is beneficial for energy saving, environmental protection and cost reduction relative to the traditional methods by using pure molybdenum and silicon as the raw materials. It was found that the phase compositions and microstructures of products were greatly influenced by the molar ratio of Si to MoS 2 and temperature. From the experimental results, it was concluded that MoSi 2 , Mo 5 Si 3 and Mo 3 Si can be prepared when the temperature was above 1100 °C, 1300 °C and 1500 °C, and the Si/MoS 2 molar ratio was 4, 2.6 and 7/3, respectively. When the Si/MoS 2 molar ratio was less than 4 and the temperature was below 1100 °C, only one Mo-Si compound (MoSi 2 ) was generated; while above 1200 °C, the excessive MoS 2 could react with MoSi 2 to generate Mo 5 Si 3 , but Mo 5 Si 3 can't react with excessive MoS 2 below 1300 °C; until above 1400 °C, Mo 5 Si 3 and MoS 2 can react to generate Mo 3 Si. However, even at 1600 °C, excessive MoS 2 couldn't react with Mo 3 Si but can be decomposed. Besides molybdenum silicides, other products SiS or SiS 2 can also be generated. SiS could escape from sample at 1100 °C in the form of gas while SiS 2 couldn't. Both the increases of temperature and molar ratio of Si to MoSi 2 were beneficial for the decrease of the residual sulfur content in the final products. From the experimental results, it was found that as increasing the temperature or the molar ratio of Si to MoS 2 from 7/3 to 4, the grain size of products increased and the sintering phenomenon among grains was more and more obvious. [ABSTRACT FROM AUTHOR]