Mechanical properties and thermal shock resistance of ZrB₂-SiC-AlN ultrahigh temperature ceramics

Two different AlN contents (5 vol%, 10 vol%) of ZrB₂-SiC matrix ultrahigh temperature ceramics were prepared by hot pressing sintering technigue. Microstructures and mechanical properties of the ceramics at room termperature were investigated. The results indicated that the composites with 5 vol% content of AlN exhibited higher density, higher flexural strength and fracture toughness (815.0 MPa and 6.16 MPa·m^1/2, respectively). Excessive adding of AlN reduced the mechanical properties of composite. The fracture surface of material showed an intergranular fracture pattern and the main toughening mechanism was crack deflection. At the same time, the thermal shock resistance of ZrB₂-15 vol%SiC-5 vol%AlN composite was investigated by water quenching. The results showed that the critical thermal shock difference in temperature was 300°C.