Effects of pressure on the pore formation of carbon/carbon composites during carbonization

Abstract

In this study, porosity and graphitizability of coal tar pitch with the treatment pressure were investigated. 4-directional carbon/carbon composites (4D C/C) were made from the matrix precursor of coal tar pitch through the process of impregnation and carbonization. Then the effects of applied pressure during the densification on the composites were observed. The matrix pitch which had 600 bar applied during the carbonization process had one and a half times less pore area ratio than that treated at 1 bar. When the pitch was heat treated up to 2300°C after the high pressure carbonization, the degree of graphitization was improved on a small scale and the crystal size tended to reduce. As the applied pressures to 4D C/C composites increased from 1 to 600 bar, the densification ratio was greatly improved. In the pore size distribution of the 4D C/C composites, the macropore portion was decreased while the mesopore portion increased, when high pressures were applied.