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

In this study, porosity and graphitizability of coal tar pitch with the tre atment pressure were investigated. 4-directional carbon/carbon composites ( 4D C/C) were made from the matrix precursor of coal tar pitch through the p rocess of impregnation and carbonization. Then the effects of applied press ure during the densification on the composites were observed. The matrix pi tch 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 pitc h was heat treated up to 2300 degrees C after the high pressure carbonizati on, the degree of graphitization was improved on a small scale and the crys tal size tended to reduce. As the applied pressures to 4D C/C composites in creased 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 we re applied. (C) 1999 Kluwer Academic Publishers.