Fabrication of Al-Si₃N₄ Composites Using a High-Strength Porous Si₃N₄ Ceramic and Their Thermal Conductivity

Abstract

Al-Si₃N₄ composites were fabricated by infiltration of Al melt with Si contents from 0 to 22vol% into a porous Si₃N₄ ceramic and their thermal conductivity was evaluated. A porous Si₃N₄ ceramic having a porosity of 39.5% and consisting of elongated β-Si₃N₄ grains connected at random in three dimensions was used as a substrate. The Al-Si₃N₄ composites were fabricated by infiltration of Al-Si alloys melt into the porous Si₃N₄ ceramic at 800°C under a pressure of 90MPa using hot isostatic pressing (HIP). Although increasing Si content significantly decreased the thermal conductivity of the Al-Si alloys, the decrease in thermal conductivity of the resulting composites was small due to increased thermal barrier conductances of the interfaces between Al and Si₃N₄.