Densification Behavior of Thermal Gradient CVI of Large-scale C/C Composites

Using integral carbon felt as reinforced perform, large-scale C/C composites were prepared by thermal gradient-chemical vapor infiltration (TG-CVI) with two temperature controlling ways, namely keeping constant temperature of the inner wall or outer wall of the samples. The results indicated that, for keeping constant temperature of the outer wall, the composite density was merely 0.64 g/cm 3 , showing high-low-high distribution across the wall. Meanwhile, its structure comprised rough laminar and smooth laminar. For keeping constant temperature of the inner wall, the density of the sample showed evenly distribution across the wall and increased to 0.98 g/cm 3 , and densification efficiency was 73.79%, higher than that of the former. Under this temperature controlling way, the composite comprised only rough laminar carbon with superior properties. Compared to the outer wall temperature controlling, the composite prepared by the inner wall temperature controlling, needed higher temperature and more appropriate temperature gradient during densification, which was consistent well with the ideal densification model. Moreover, the inner wall temperature controlling way enabled the large-scale C/C composite densification from inner side to outside wall, and achieved uniform density distribution, high densification efficiency and excellent microstructure.