Induction-field-activated self-propagating high-temperature synthesis of AlN-SiC solid solutions in the Si3N4-Al-C system

The synthesis of AlN-SiC solid solutions from Si3N4, Al, and C was investig ated using the induction-field-activated/self-propagating high-temperature synthesis/static pseudo-isostatic compaction technique. Careful x-ray diffr action analyses were made on the products of combustion to determine reacti on routes. Optical microscopy as well as scanning electron microscopy with an electron probe microanalysis was used for microstructural analysis. It w as found that initially molten aluminum reacted with silicon nitride produc ing an AI-Si alloy. At higher temperatures, aluminum evaporated from the Al -Si liquid and the synthesis of AlN via a vapor phase process took place. S ubsequently, dissolution of AIN into molten Si resulted in the formation of an AlN-SiC solid solution from the Al-N-Si-C liquid phase. However, below 1850 degreesC, the resulting solid solution of 4AlN-3SiC was not fully crys tallized. Combustion temperatures above or equal to 1850 OC were required t o prepare a highly crystallized solid solution with a morphology exhibiting hexagonal platelets. Based on these observations, a model for the formatio n of AlN-SiC solid solution is proposed.