In-situ formation of AlN/Al composite

Abstract

The present authors have found that the in-situ type composite of AlN plus Al can be formed by having Al react with powder BN and by fixing the weight ratio of the former to the later to a suitable value under a certain condition of heating temperature and pressurized atmosphere of N2. The most recommended conditions for the reaction is such that heating at 1373 K under 1.013 MPa of N2 with the mass ratio of Al to BN to 6 : 1. Volume fraction of AlN in the primary composite ingot is around 40%. If we secondarily heat-treat this composite under the suitable condition of higher temperature and higher pressure of N2 than those for the primary composite, the volume fraction of AlN can be raised to a value more than 90%. The properties such as thermal expansion coefficient and hardness of this high ratio AlN composite are very close to those of the commercial AlN which is usually made by the sintering method. So, the present type of AlN+Al composite, which is expected to be produced at a low cost, may be used for such as the heat-sink substrate for semiconductor devices, and also may be used as the light weight heat-resisting material.