Effect of BN Addition on the Mechanical Properties of AlN

Aluminum nitride (AlN) has several attractive properties including high thermal conductivity, excellent electrical insulation, a thermal expansion coefficient close to that of Si and low density. Accordingly, it is considered a promising packing material and substrate for high power integrated circuits. However, its low fracture toughness at room temperature limits its wide industrial application. To improve its mechanical properties, the approach generally utilized has been to fabricate and add nanostructured materials as a second phase, to make composites. In this study highly dense nanostructured AlN and AlNBN composites were sintered for two minutes at 1400 oC. The effect of BN on the mechanical properties (fracture toughness and hardness) and the microstructure of the AlN-BN composites was investigated. The hardness and fracture toughness of AlN, AlN-1 vol% BN, AlN-3 vol% BN, AlN-10 vol% BN were 943, 1455, 1147, 1110 kg/mm2 and 4, 5.7, 5.5, 5.4 MPa·m1/2, respectively. The addition of BN to AlN simultaneously improved the hardness and fracture toughness of the AlN-BN composite by deterring crack propagation. This study demonstrates that BN can be an effective reinforcing material to improve the fracture toughness and hardness of AlN composites.