Effect of Pressure on Graphitization of Carbon. IV. Abrupt Graphitization of Hard Carbon under 5 kbar

Abstract

A hard carbon, phenolformaldehyde resin char carbonized to 700°C, was heat-treated under a quasi-hydrostatic pressure of 5 kbar at various temperatures between 1100–1800°C for the residence times of 3, 20 and 60 min. The graphitization process of the hard carbon under pressure consisted of three stages. In the first stage of the graphitization, the profile of (002) diffraction line was symmetrical. It means that there is only one component A_H in the sample. In the second and third stages of graphitization, the (002) profile became composite. In the second stage, three components A_H, G′_H and G″_H coexisted in the sample. The sum of the contents of the components G′_H and G″_H was less than 20% and increased gradually with heat treatment temperature. In the third stage, two components A_H and G″_H coexisted. The content of the component G″_H increased abruptly up to more than 70% at about 1400, 1500 and 1700°C for the residence time of 60, 20 and 3 min, respectively. The components A_H and G″_H have the turbostratic and graphitic structures, respectively. The component G′_H seemed to have the intermediate structure between turbostratic and graphitic structures.