Fabrication And Properties Of ZrO_2p/Bn-SiO₂ Composites

h-BN nano-film coated ZrO2 composites particles were prepared by chemical route using H3BO3, CO(NH2)2 and nano-ZrO2 powders as starting materials. The formation mechanisms and procedures for preparing BN coated ZrO2 nano-composites powders were investigated. ZrO2p/BN-SiO2 composite was fabricated by hot pressing. The as-prepared composites particles were characterized by DSC, XRD, SEM and TEM techniques. The effect of ZrO2 composites particles coated with h-BN nano-film on the microstructure, mechanical properties and thermal shock resistance of ZrO2p/BN-SiO2 composites material was discussed.The results indicate that h-BN nano-film coated ZrO2 composites particles can be prepared with the mole ratio of 1:3 for H3BO3 to CO (NH2)2 and the volume ratio 3:1 for BN to ZrO2, and nitridation is conducted at 750℃. TEM obsercation proves that ZrO2 particles were well coated by BN thin film whose thickness is 10~50 nm. h-BN nano-film coated ZrO2 composites particles can well prevent the reaction between SiO2 and ZrO2.For the ZrO2p/BN-SiO2 composite, the relative density decreases with the increasing content of ZrO2. And the bending strength and fracture toughness first increases and then decreases with the increasing content of ZrO2. When the content of ZrO2 is 4%, the bending strength and fracture toughness of the composite reached the maximum values, 212.9MPa and 2.55MPa·m1/2, respectively. And the elastic modulus, hardness and thermal expansion coefficient increase with the increaseing content ZrO2. Composite manifests excellent thermal shock resistance, the critical temperature diference of thermal shock is over than 1100℃. Better mechanical properties and thermal shock resistance of ZrO2p/BN-SiO2 composite can be obtained, when ZrO2 particles coated with h-BN nano-film were incorporated at the content of 4~6vol. %.