High temperature mechanical properties of BN matric composites ceramics

Using BN, SiO₂, AlN as the raw materials, BN matric composites ceramics were fabricated by hot-press sintering. Effects of AlN content on high temperature mechanical properties and fracture behavior were studied. The results showed that the high bending strength increased at first and then decreased with the increase of temperature, and the maximum values reached at 1300°C. The increase of strength is due to the internal stress relief. While the composite with 5vol.% AlN content had a maximum flexural strength of 376.7 MPa at 1300°C, 52.5% higher than that at room temperature. When the temperature rose to 1500°C, the high temperature flexural strength was 272.0 MPa, showing a good high temperature mechanical property.