Preparation of nanocrystalline molybdenum disilicide (MOSi2) by a chlorine-transfer reaction

Reaction Of MoCl3 and Si at 500 degreesC produces phase-pure MoSi2 powders in near-quantitative yields. Use of an inert diluent (LiCl or ZnCl2) enable s the production of nanocrystalline powders. The diluent can be subsequentl y removed by washing with methanol or by sublimation. Consolidation of dilu ent-free powders by hot pressing at 1400 degreesC and 375 MPa for 0.5-4 h a ffords dense compacts (> 95% theoretical density) possessing nanocrystallin e grains (< 50 nm) and exhibiting hardnesses of 15.0-16.3 GPa. This constit utes a 60-75% enhancement in hardness over conventional, microcrystalline M OSi2.