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

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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 MoS2 and temperature. From the experimental results, it was concluded that MoSi2, Mo5Si3 and Mo3Si can be prepared when the temperature was above 1100 °C, 1300 °C and 1500 °C, and the Si/MoS2 molar ratio was 4, 2.6 and 7/3, respectively. When the Si/MoS2 molar ratio was less than 4 and the temperature was below 1100 °C, only one Mo-Si compound (MoSi2) was generated; while above 1200 °C, the excessive MoS2 could react with MoSi2 to generate Mo5Si3, but Mo5Si3 can't react with excessive MoS2 below 1300 °C; until above 1400 °C, Mo5Si3 and MoS2 can react to generate Mo3Si. However, even at 1600 °C, excessive MoS2 couldn't react with Mo3Si but can be decomposed. Besides molybdenum silicides, other products SiS or SiS2 can also be generated. SiS could escape from sample at 1100 °C in the form of gas while SiS2 couldn't. Both the increases of temperature and molar ratio of Si to MoSi2 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 MoS2 from 7/3 to 4, the grain size of products increased and the sintering phenomenon among grains was more and more obvious.