PIP结合CVI制备氧化铝-莫来石陶瓷基复合材料

通过PIP结合CVI法制备了C纤维增初三维氧化铝-莫来石陶瓷基复合材料,采用CVD法制备了防氧化涂层,研究了复合材料致密化过程、复合材料的物相、微观结构、力学性能和抗氧化性能。结果表明,CVI能够将氧化硅引入到多孔氧化铝基体内部,1400℃处理后氧化硅与氧化铝完全反应生成莫来石,显著提高了仅以PIP法制备的多孔氧化铝基复合材料的力学性能,CVD制备的氧化硅涂层有效阻止了氧气的侵入,复合材料在1200℃大气环境下保温50h后,试样三点弯曲强度保持率为70％。

Preparation of C Fiber Reinforced Alumina-Mullite Composite by PIP and CVI

Continuous fibers reinforced ceramic composites are attractive for application as high temperature structural materials. 3D alumina-mullite ceramic matrix composite reinforced by C fibers was manufactured by PIP and CVI. C fiber preform with 0.2μm C interface layer was dipped in aluminium nitrate saturation sol for 2h, dried in an autoclave and subsequently heat treated at 900℃. After seven cycles, the specimen was heated to 1100℃ in Ar to convert the amorphous alumina to γ-Al₂O₃ and α-Al₂O₃. Then 10h CVI was performed to infiltrate the silica into the specimen. Subsequently 10h CVD was performed to manufacture the oxidation resistance coating. After CVI and CVD, the specimen was heated to 1400℃ for 2h in Ar to get C_f/A-M composite. XRD shows the matrix contains 53wt% alumina and 47wt% mullite. The density and relative density of the as-received composite are 1.96g·cm^-3 and 95% respectively. 3-points bend strength and fracture strain of C_f/A-M composite at room temperature are 245MPa and 0.9～1.0% respectively. The strength retention is 70% when the composite was heated at 1200℃ for 50h in air, which indicates the silica coating is very effective in preventing O₂ from entering the composite. The fracture surface of the composite shows a considerable fibers pull-out, which indicates there exists a weak fiber-matrix interface that can provide high damage tolerance to the composite. This result indicates the C interface is very usable.