Preparation And Study Of 3D-C_f/SiC Ceramic Composites

Continuous carbon fiber reinforced Si C ceramic matrix composite becomes one of the ideal high-temperature structural materials due to its low density, high strength, good toughness, ablative resistance, erosion resistance and other outstanding features.Three-dimensional fabric made by continuous carbon fibers can guarantee Cf/Si C composite to form a three-dimensional network structure in X, Y, Z directions. This structure avoid the low inter laminar shear strength existed in conventional composite materials.There are three typical preparation methods of 3D-Cf/Si C ceramic matrix composites:chemical vapor infiltration method(CVI), precursor infiltration pyrolysis method(PIP) and reactive melt infiltration(RMI). Compared with CVI, PIP and RMI become highly competitive ceramic composites’ preparation technology due to their simple processes. In this paper, we carried out the study of preparing 3D-Cf/Si C ceramic matrix composites by PIP and RMI methods, and optimized their optimum process parameters. On the basis of the previous study, nanometer Si C powder was added as a filler to precursor solution, then introduced into a three-dimensional carbon fiber preform with the solution and we discussed the effect of the Si C filler addition on the preparation cycles and the properties of materials. The main conclusions are as follows:(1) The preparation of precursor solution in PIP study, when the ratio of PCS and its DVB solvent was 1: 0.6, the ceramic-yield of PCS can reach 63%, and the liquidity of prepared precursor solution increased significantly, which is advantageous to the impregnation.(2) In the research on impregnation- curing- pyrolysis of PIP: The best impregnation temperature was that carbon fiber was impregnated at 80 ℃ for 60 min, then impregnated at 35℃ for 30 min. The optimum curing-crosslinking process was that the impregnated carbon fiber was cured at 120 ℃ for 180 min, then crosslinked at 150 ℃ for 180 min. In the pyrolysis process, rapid heating rate at initial cleavage(1-5 cycles) and slow heating rate at later pyrolysis process were adopted.(3) In the PIP process, when mass ratio of Si C filler was 11.11% in precursor solution,the period of materials’ preparation could be shortened. Si C filler can not only fill the pores and reduce precursor volume shrinkage during pyrolysis process, it also had enhancing effect, which improved the physical and mechanical properties of 3D-Cf/Si C composite materials.(4) In the study on infiltration- Curing- carbonation of RMI method, the prepared3D-Cf/C that after two cycles of resin impregnation-carbonization-process were siliconized to prepare 3D-Cf/Si C material. The prepared 3D-Cf/Si C composites had higher density and lesser residual carbon and silicon than other materials.(5) Research in siliconizing process of the RMI method, when the siliconizing temperature was 1550℃, liquid silicon was easier to penetrate in 3D-Cf/C biscuit and dense 3D-Cf/Si C composites were prepared finally. Carbon fiber was also hardly damaged at this temperature. So 1550℃ was a suitable silicon infiltration temperature in this study.(6) In RMI process, when mass ratio of Si C filler was 8.33% in precursor solution,the density and flexural strength of 3D-Cf/Si C composites were improved. The addition of Si C powder can reduce contact area of silicon and carbon fiber in the process of siliconizing, and reduce the reaction between them. Then it would form an appropriate interface bond strength, which enables the fiber pull out and play an enhancement effect.