CaO-assisted H 2 reduction of MoS 2 for preparing ultrafine Mo powder

Abstract

In the work, the method of CaO-assisted H₂ reduction of MoS₂ was proposed for the preparation of ultrafine Mo powder using reagent grade MoS₂ (98%) as the Mo source. The influence of reaction temperature (1120 to 1273 K) and CaO/MoS₂ molar ratios (1.5 to 3.0) on the reaction behaviour and product phase were investigated, and different technologies such as thermogravimetry, X-ray diffraction, field emission scanning electron microscopy, and thermodynamics calculation were used to analyse the experimental data. The thermodynamic calculation result demonstrated that the H₂ reduction of MoS₂ with the help of CaO is feasible with the initial reaction temperature of about 1120 K. Under an Ar atmosphere, the work found that the reaction between CaO and MoS₂ could occur with the formation of partial metallic Mo and calcium molybdate (CaMoO₄). However, after introducing H₂ gas, the newly as-formed CaMoO₄ can be rapidly reduced, leading to the resulting product composed of metallic Mo and CaS. The optimal conditions for the preparation of ultrafine Mo powder by this method are also obtained, that is, CaO/MoS₂ molar ratio: 2 : 1, reaction temperature: 1273 K. After the hydrochloric acid treatment, the work found that the formed CaS existed in the resulting product can be effectively removed, and then ultrafine Mo powder with the average size of 0.48 μm and yield of 92.3% was obtained.