Thermal properties of pressureless melt infiltrated AlNaSiaAl composites

Thermal properties of AlN-Si-Al composites produced by pressureless melt infiltration of Al/Al alloys into porous alpha -Si3N4 preforms were investigated in a temperature range of 50-300 degree C. SEM and TEM investigations revealed that the grain size of AlN particles was less than 1 mu m. In spite of sub-micron grain size, composites showed relatively high thermal conductivity (TC), 55-107 W/(m.K). The thermal expansion coefficient (CTE) of the composite produced with commercial Al source, which has the highest TC of 107 W/(m.K), was 6.5X10-6 K-1. Despite the high CTE of Al (23.6X10-6 K-1), composites revealed significantly low CTE through the formation of Si and AlN phases during the infiltration process.