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

Nano-sized amorphous powders of molybdenum disulfide have been prepared by gamma-irradiation method in ambient pressure and at room temperature. The o btained precipitate was dried at 60 degrees C, then crystallized by calcina tion in a flow of argon at 160-650 degrees C. All the samples were characte rized by X-ray diffraction (XRD) and Extended X-ray Absorption Fine Structu re (EXAFS). The results from X-ray diffraction analysis reveal that the pow der dried at 60 degrees C is in an amorphous state, it was partly crystalli zed when calcined at above 300 degrees C. The size of particles in the samp le calcined at 500 degrees C is about 10 nm. EXAFS analysis demonstrates th at the Mo species in the sample dried at 60 degrees C are present in the fo rm of a chain-like structure with Mo-S-Mo bonds as basic building units, si milar to that in the crystalline MoS2 compound, and with a high level of di sorder in the nearest coordination shell. The amorphous sample is partly cr ystallized by treating at above 300 degrees C, and some of the Mo-S-Mo bond s 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 sam ple was calcined at above 300 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.