Fabrications, microstructure and mechanical behaviors of h-BN matrix ceramic

Turbostratic boron nitride (t-BN) powders have been synthesized through reactive sintering process using B and N₂, h-BN matrix ceramic has been sintered using the obtained t-BN powders and the commercial h-BN as raw materials and Al₂O₃/Y₂O₃ as sintering aids. The compositions, morphologies, porosity, and mechanical properties of the as fabricated composites were investigated. The results show that after sintering at 1850°C for 2 h, the unique uniform with card- house structure of h-BN was observed. The combination effect of sintering-aids densification and card-house structure densification is the main mechanism which controls the microstructure evolution of h-BN. When the reactive synthetic temperature of t-BN is 1350℃ for 2h, the Al₂O₃/Y₂O₃ ratio is 3: 2 and total contents of sintering ads is 15wt%, the porosity and flexural strength of the sintered body reaches the optimum, respectively.