High temperature thermo-physical properties and thermal shock behavior of metal-diborides-based composites

The thermo-mechanical properties and thermal shock resistance of two metal diborides composites, HfB2 with 20 vol.% SiC and HfB2 with 20 vol.% SiC and 10 vol.% AlN, were investigated. Results showed that the composite HfB2-SiC-AlN had a higher specific heat capacity than that of composite HfB2-SiC. However, the occurrence of a Si-Al-O phase in the grain boundaries increased the heat flow resistance at grain boundaries, resulting in decrease thermal diffusivity and thermal conductivity. The calculated thermal shock resistance parameters indicated that the addition of AlN increased the resistance against crack initiation and crack propagation of composite, corresponding to the increase in critical thermal shock temperature difference from 400 to 600 °C.