碳化硅粉体对熔融渗硅法制备C_f/SiC复合材料结构的影响

Effect of Silicon Carbide Powder on Preparation of C_f/SiC Composites by Molten Silicon Infiltration

以三维针刺碳纤维为预制体,含有微米级碳化硅粉体的酚醛树脂浆料为碳源,采用熔融渗硅(Molten Silicon Infiltration)法制备Cf/SiC复合材料,研究了碳化硅粉体的存在对制备Cf/SiC复合材料结构的影响。结果表明:预成型体中,微米级碳化硅粉体能有效的浸渍至纤维束中,并在裂解过程中因与基体碳热膨胀系数差异产生与粉体粒径相当的微裂纹,形成裂纹孔道结构,预成型体密度为1.32 g/cm3,开口气孔率为25%;复合材料中,裂纹的引入为熔融渗硅提供通道,但裂纹孔道尺寸过大影响了复合材料的进一步致密化,SEM表明在碳化硅颗粒周围形成闭气孔,复合材料密度为1.93 g/cm3,开口气孔率为7%。

Cf/SiC composites were fabricated by molten silicon infiltration using three-dimension needled carbon fiber as preform,phenol-formaidehyde resin contains micron SiC powder as carbon source.The effect of SiC powder on the microstructure of composites were investigated.The results indicated that the micron SiC powder can infiltrate to the fiber bundle and made lots of micro-cracks because of the mismatch of the coefficient of the thermal expanding between it and the matrix during the pyrolysis process.The density of perform was 1.32 g/cm3 and the open porosity was 25% before the molten silicon infiltration.The cracks,which were about micrometers in width,were in favor of the molten silicon infiltrate.The microstructure of the composites were characterized by SEM.The density was 1.93 g/cm3 and the open porosity was 7 % after the molten silicon infiltration.