Investigation of High Pressure Gas-solid Self Propagating High Temperature Synthesis h-BN-SiO_2 Ceramics

h-BN-SiO2 ceramics were prepared by means of high pressure gas-solid self-propagating high temperature synthesis technology from powders of B, h-BN and SiO2. The nitrogen pressure and porosity of reactants that influence on ignition, and products have a scope, 48% 52%,75MPa p 85MPa, in which the non-cracked combustion products can be obtained. The density of product is up to 1.79g.cm-3 and the bending strength and hardness of h-BN-SiOZ ceramic are up to 76MPa and 212(HV) respectively. The higher tile nitrogen pressure the bigger the h-BN particles. The h-BN particles are isotropy. Crystalline B7O and glasses SiO2 exist in the product. Crystalline SiO2 was disappeared because of rapid cooling from combustion temperature to 1000℃. Glass's phases that are not found among the h-BN particles only exist at the edge of B7O, which demonstrates that SiO2 is the cause of B7O formation.