氮化硅纤维增强氮化硼基复合材料制备及高温性能研究OA

Aiming at the application requirements of hypersonic vehicles for new high-temperature transparent composite materials,Si3N4f/BN composite was prepared by using PIP process with three-dimensional woven fabric of Si3N4f fiber satin weave as reinforcement and borazine as ceramic precursor.The structure and properties of Si3N4f/BN composite were characterized by SEM,XRD,high temperature bending and ablation.The results show that Si3N4f/BN composite appears uniform and dense texture and the density reaches 1.82 g/cm3.They have excellent high temper-ature mechanical properties with a flexural strength of 76.9 MPa at 1 400 ℃ and a strength retention rate exceeding 70％.At 1 400 ℃,the composite still maintains an amorph structure.Si3N4f/BN composite also exhibits excellent ablation resistance with a linear ablation rate of 0.026 mm/s for the test that adopted oxygen-acetylene ablation test in accordance with GJB 323A-1996.The surface of ablative area and the area along the direction of heat flow are emerged the ablation center area,the ablation transition area,and the non-ablated matrix area.In the ablation cen-ter,the fibers are consumed,leaving only a porous BN matrix and a small amount of oxides.In the ablation transi-tion area,the surface of the fiber is wrapped by molten oxides.The non-ablated area is still a dense Si3N4f/BN ma-trix.