Synthesis of molybdenum silicide/mullite composites for high-temperature applications

Molybdenum silicide/mullite composite having about 31 wt. % MoSi₂ has been SHS-produced from a reactive blend composed of MoO₃, SiO₂, and Al. Additional amounts of silica were added to undergo mulHte formation reaction. The overall reaction involves both exothermic and endothermic ones. The endothermic mullite formation reaction is loaded onto the exothermic reaction of the reactive mixture. The effects of Al grain size (from 45 to 20 μm) and pre-heating temperature (from room temperature to 500°C) on the synthesis of the target composite were studied. Al grain size and preheating temperature were found to have decisive influence on the mullitization reaction. The sample containing 36-μm Al and ignited at 400°C was found to undergo complete mullitization reaction. The mechanism of the overall combustion reaction was postulated. In addition, oxidation resistance of this composite at 1100–1300°C in open atmosphere was determined.