Fabrication of Al-Si3N4 composites using a high-strength porous Si3N4 ceramic and their thermal conductivity

Al-Si3N4 composites were fabricated by infiltration of Al melt with Si cont ents from 0 to 22 vol% into a porous Si3N4 ceramic and their thermal conduc tivity was evaluated. A porous Si3N4 ceramic having a porosity of 39.5% and consisting of elongated beta -Si3N4 grains connected at random in three di mensions was used as a substrate. The Al-Si3N4 composites were fabricated b y infiltration of Al-Si alloys melt into the porous Si3N4 ceramic at 800 de greesC under a pressure of 90 MPa using hot isostatic pressing (HIP). Altho ugh 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 i nterfaces between Al and Si3N4.