| Micropyretic synthesis has tremendous potential as an economical processing technique for synthesizing intermetallics, ceramics and composites. One class of reactions is the thermite reaction using the heat of formation of oxides of aluminum and magnesium. Molybdenum disilicide alumina composites can be synthesized using the reaction between molybdenum oxide, aluminum and silicon to form molybdenum disilicide and aluminum oxide. Molybdenum disilicide composites have the potential to improve the room temperature toughness and high temperature strength of molybdenum disilicide.; In this dissertation, the reaction between molybdenum oxide, aluminum and silicon is examined. The experimental part of the dissertation examines the aluminothermic reaction between molybdenum oxide and aluminum. The porosity formation as well as the microstructure and phase formation during the reaction between molybdenum oxide, aluminum and silicon is examined. The results indicate that the porosity can be decreased by increasing the temperature and the amount of liquid phase. The microstructure and phases obtained depend on the composition and the temperature obtained during the reaction.; The numerical study involves the simulation of the combustion wave propagation using a two step reaction sequence. The first step in the sequence is the reaction between molybdenum oxide and aluminum to form molybdenum and aluminum oxide. The second step is the reaction between molybdenum and silicon to form molybdenum disilicide. The results show that for the aluminothermic reaction, the first reaction, between aluminum and molybdenum oxide is the rate controlling reaction.; The second part of the model considers the interaction of gas and solid as well as gas evolution to estimate the pressure developed within the pores, which could cause porosity formation. The results show that there can be significant increase in gas pressure due to gas evolution. The increase is maximum when the gas evolution takes place in the combustion zone. |
