Preparation and structural characterization of nano-sized amorphous powders of MoS2 by γ-irradiation method

Nano-sized amorphous powders of molybdenum disulfide have been prepared by gamma-irradiation method in ambient pressure and at room temperature. The obtained precipitate was dried at 60 degrees C, then crystallized by calcination in a flow of argon at 160-650 degrees 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 degrees C is in an amorphous state, it was partly crystallized when calcined at above 300 degrees C. The size of particles in the sample calcined at 500 degrees C is about 10 nm. EXAFS analysis demonstrates that the Mo species in the sample dried at 60 degrees 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 MoS2 compound, and with a high level of disorder in the nearest coordination shell. The amorphous sample is partly crystallized by treating at above 300 degrees 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 degrees C. Total sulfur analysis shows that the sulfur is partly lost when the sample was calcined at above 300 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.