Microwave sintering and properties of AlN/TiB₂composites

The effect of TiB₂on the densification behavior and properties of microwave-sintered AlN/TiB₂ceramic was investigated. The densification of the composite was significantly retarded in nitrogen atmosphere due to strong nitridation of TiB₂compared to sintering in argon atmosphere. The densities of the AlN/TiB₂composites containing different amounts of TiB₂all reached 99% of the theoretical density during 2 h of sintering at 1850 and 1900 °C. Microstructure analysis revealed that the TiB₂particles were dispersed in the AlN matrix while AlN grains retained its contiguity. This microstructure led to a composite with superior properties; thermal conductivity as high as 149 W/(m K) was achieved. The microwave sintered composites are harder and tougher than pure AlN. Microwave-sintered AlN/TiB₂composite is a promising material for structural applications in which high thermal conductivity and controlled dielectric loss are important.