界面涂层对气相渗硅C_f／SiC复合材料力学性能的影响

Effect of Interphase on Mechanical Properties of C_f/SiC Composites Fabricated by Vapor Silicon Infiltration

在1650℃气相渗硅(Vapor Silicon Infiltration-VSI)制备了3D碳纤维增强SiC基复合材料(C_f/SiC),其密度约为1.85g/cm^3.当C/SiC界面涂层存在时,气相渗硅C_f/SiC强度为239.5MPa;而无界面涂层存在时,C_f/SiC弯曲强度大幅下降,约为67.4MPa.无界面涂层保护时,气相渗硅过程中纤维与硅蒸气发生反应,使得纤维硅化,造成材料性能下降.纤维表面沉积的C/SiC涂层,不仅保护纤维,避免被硅侵蚀,而且具有弱化界面、偏转裂纹等作用,复合材料的断裂功得到显著提高.将气相渗硅温度提高到1700℃后,有界面涂层存在情况下C_f/SiC复合材料密度显著提高,达到2.25g/cm^3,强度基本与1650℃时相当.

3D carbon fiber reinforced silicon carbide matrix composites （Cf/SiC） were fabricated by vapor silicon infiltration （VSI） at 1650℃. Densities of the composites with or without C/SiC interphase are about 1.85g/cm^3. The characterization of the Cf/SiC composites was investigated. When C/SiC interphases exist, the carbon fibers are protected from the reaction with silicon gas and the fibers remain intact. The fiber-matrix bonding is weakened and the distinct fiber pull-outs occur in Cf/SiC composites with interphases. The composite shows non-brittle fracture behaviour and its flexure strength reaches around 239.5MPa. However, the Cf/SiC composite without interphase has very poor mechanical performance. Its flexure strength is only 67.4MPa. Results indicate that the carbon fibers are siliconized during vapor silicon infiltration without interphase. When the vapor infiltration temperature increases to 1700℃, density of Cf/SiC composites with interphase increases to 2.25g/cm^3. Strength of this composite is nearly the same as that fabricated at 1650℃.