关键词: C纤维, PIP, CVI, 氧化铝-莫来石, 复合材料

Abstract: 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.

Key words: C fiber, PIP, CVI, alumina-mullite, composites