Microstructure, mechanical properties and thermal shock behavior of h-BN-AlN ceramic composites prepared by combustion synthesis

h-BN-SiC-AlN-TiN ceramic composites with volume content of AlN-TiN ranging from 20% to 70% were prepared by combustion synthesis from powder compacts of B₄C, Si, Al and TiN under 100 MPa nitrogen pressure. The volume fraction of AlN-TiN was found to have a significant influence on the microstructure, mechanical properties and thermal shock resistance of the composites. With the increasing volume content of AlN-TiN, the mechanical properties of the composites were improved remarkably, while thermal shock resistance decreased. Thermal shock tests showed that the critical thermal shock temperature (ΔT) was higher than 1200 °C for the composites with AlN-TiN contents of 30 vol%; while it was decreased to 850 and 670 °C for the composites with AlN-TiN contents of 50 and 70 vol%, respectively.