Pressure Effects on the Morphology Development of C/C Composites During Carbonization

It is well known that the fabrication process of carbon/carbon composites is very complex. Above all, the carbonization process have major effect on the morphology development of carbon matrix. Carbon/carbon composites of 4-directional fiber preform were fabricated using the coal tar based pitch as a matrix precursor in this study. According to carbonization pressure of 1 bar, 100 bar, 600 bar, and 900 bar, morphological changes of cokes and matrix of composites were discussed. As the carbonization pressure increased to 600 bar, the flow pattern morphology of bulk mesophse was well developed. On the contrary, mosaic pattern morphology was found in case of 900 bar of carbonization pressure. It is confirmed that the carbonization pressure have profound effect on the degree of graphitization and crystal size of carbon matrix. Even in the highly densified carbon/carbon composites, large voids were still found in the matrix pocket region.