Effects of different additives on microstructure and crack resistance for an ultra-high temperature ceramic

ZrB2-20%SiC-10%graphite (ZSC) and ZrB2-20%SiC-10%AlN (ZSA) were fabricated by hot press sintering. Crack resistance was investigated for the two materials by the envelope method. These results indicated that ZSC had a relatively higher damage resistance than that of ZSA. Visible from the SEM images, the crack propagation path was more twisted in ZSC than that in ZSA, therefore, more energy was dissipated in ZSC.