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 lOh CVI was performed to infiltrate the silica into the specimen. Subsequently lOh 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 Cf/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 Cf/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.