Reactive synthesis and phase stability investigations in the aluminum nitride-silicon carbide system

The effect of AIN on the structure formation of SIC was investigated. SiC was synthesized in the presence of AIN under vacuum at 1500 degrees C, and the result was cubic SIG. The synthesis of AIN-SiC composites through the reaction Si3N4 + 4Al + 3C = 3SiC + 4AlN was also investigated and compared with synthesis via field-activated self-propagating combustion (FASHS). Reactants were heated in a vacuum furnace at temperatures ranging from 1130 degrees to 1650 degrees C. Below 1650 degrees C, the reaction is not complete and at this temperature the product phases are AIN and cubic SiC. At 1650 degrees C, the product contained an outer layer which contained beta-SiC only and an inner region which contained AIN and cubic SiC, 2H-SiC and AIN composites synthesized via field-activated self-propagating combustion were annealed at 1700 degrees C under vacuum. The AIN dissociated and evaporated and the 2H-SiC transformed to the cubic beta phase. Reasons for the differences in products of furnace heating and FASHS are discussed.