Preparation and structural characterization of nano-sized amorphous powders of MoS 2 by γ-irradiation method

Abstract

Nano-sized amorphous powders of molybdenum disulfide have been prepared by γ-irradiation method in ambient pressure and at room temperature. The obtained precipitate was dried at 60°C, then crystallized by calcination in a flow of argon at 160–650°C. All the samples were characterized by X-ray diffraction (XRD) and Extended X-ray Absorption Fine Structure (EXAFS). The results from X-ray diffraction analysis reveal that the powder dried at 60°C is in an amorphous state, it was partly crystallized when calcined at above 300°C. The size of particles in the sample calcined at 500°C is about 10 nm. EXAFS analysis demonstrates that the Mo species in the sample dried at 60°C are present in the form of a chain-like structure with MoSMo bonds as basic building units, similar to that in the crystalline MoS 2 compound, and with a high level of disorder in the nearest coordination shell. The amorphous sample is partly crystallized by treating at above 300°C, and some of the MoSMo bonds are fractured to form Mo=S bonds in the process of crystallization, but the level of crystallization is still low even when treated at 650°C. Total sulfur analysis shows that the sulfur is partly lost when the sample was calcined at above 300°C.