COMBUSTION SYNTHESIS OF TRANSITION-METAL CARBOSULFIDES

The combustion synthesis of ternary and quaternary carbosulfides of th e transition metals was investigated to obtain high-purity materials t o be tested as solid lubricants in high-temperature environments. The main carbosulfide formation mechanisms have been clarified in the case of the technologically interesting tantalum carbosulfide, enabling th e preparation of reaction products with controlled purity. The formati on of molten tantalum sulfide as an intermediate product was found to play a key role for obtaining a homogeneous reaction product, and the presence of excess carbon reduced the oxygen content of the carbosulfi de. However, the higher the overall carbon contents, the higher is the amount of carbide impurities in the reaction products. Use of iodine or hexachlorobenzene as a catalyzer minimized the need of excess sulfu r in the raw powder mixture, reduced the amount of carbide impurities, and contributed to the homogenization of the reaction products. (C) 1 998 Academic Press.