A study of the combustion synthesis of MoSi2 and MoSi2-matrix composites

The combustion synthesis of MoSi2 from elemental powders was investigated. Higher completion of the reaction was achieved by the use of prior compaction of powders and higher heating rates. The reaction mechanism was studied by performing experiments at a heating rate of 20 K/min. It was established that reaction occurred via capillary motion accompanying the flow of molten silicon to the molybdenum powder particles. During the synthesis of MoSi2/TiC composites, two ternary (Mo,Ti) Si-2 phases were observed, in contradiction to the thermodynamic predictions of the Mo-Si-Ti-C system. Combustion synthesis of (Mo, W) Si-2 yielded an inhomogeneous product where the composition of the solid solution varied throughout the sample. These observations were discussed in terms of the characteristics of the reaction process.