C/C坯体对RMI C/C-SiC复合材料组织的影响

Influence of different C/C performs on microstructure of C/C-SiC composites fabricated by RMI

以PAN基炭纤维(Cf)针刺整体毡为预制体,用化学气相渗透(CVI)、浸渍炭化(IC)方法制备了不同炭纤维增强炭基体的多孔C/C坯体,采用反应熔渗(RMI)法制备C/C-SiC复合材料,研究了渗Si前后坯体的密度和组织结构。结果表明:不同C/C坯体反应溶渗硅后复合材料的物相组成为SiC相、C相及单质Si相;密度低的坯体熔融渗硅后密度增加较多;密度的增加与开口孔隙度并不是单调增加的关系,IC处理的坯体开口孔隙度低,但渗硅后复合材料的密度增加较多;IC坯体中分布分散的树脂C易与熔渗Si反应,CVI坯体中的热解C仅表层与熔渗Si反应,在Cf和SiC之间有热解C存在;坯体密度相同时,IC处理的坯体中SiC量较多,单质Si相含量少且分散较好,而CVI坯体中SiC量较少,单质Si相的量较多;制备方法相同时,高密度的C/C坯体,渗硅后C相较多。

C/C-SiC composites were fabricated by reactive melt infiltrating（RMI） Si to different C/C preforms prepared by chemical vapor infiltration（CVI） or resin impregnation and carbonization （IC）. The changes of the density and microstructure of the preforms before or after infiltrating Si were studied. The results show that RMI C/C-SiC composites fabricated by infiltrating Si into different performs consist of SiC, C and residual Si phases. The lower the density of preform , the higher the densification of C/C-SiC composites after infiltrating Si is. But the increment of the density after infiltrating Si does not monotonely increase with the open porosity of preform. The density after infiltrating Si only increases more in preform fabricated by IC although its open porosity is lower. The resin carbon in preforms is easier to react with infiltrating Si , but pyrolytic carbon of on outer surface of the carbon fiber（Cf） reacts with infiltrating Si, leading to some pyrolytic carbon between Cf and SiC which protects Cf. The amount of each phase in the composites is related to the type of carbon and the density of C/C preforms. At same density of preforms, the amount of SiC is more, and the amount of residual Si is litter and distribution of Si is more dispersive in the composites prepared by IC than that by CVI after infiltrating Si.