Effect of Pressure on Graphitization of Carbon. I. Heat Treatment of Soft Carbon under 1,3 and 5 kbar

Abstract

Polyvinylchloride coke was heat-treated under the quasi-hydrostatic pressure of 1,3, and 5 kbar by using a simple piston cylinder type high pressure apparatus. The process of graphitization under pressure was studied kinetically by analyzing the profile of the (002) diffraction line. It was found that the accelerating effect of pressure on the graphitization of carbon became more pronounced at higher pressure. The process of graphitization under 3, and 5 kbar seemed to take place in at least two stages. In the first stage, the profile of the (002) line shifted simply from the position of the original line to 26.0° in 2θ, which corresponded to a c0-spacing of 6.85 Å. In the next stage, a new component, having a c0-spacing of about 6.72 Å, appeared in addition to the first component, having a c0-spacing of 6.85 Å. Therefore, the profiles of the (002) line became composite. Under 1 kbar, however, no composite profiles were observed and the c0 Spacing decreased gradually with heat treatment. Approximate values for the activation energy and activation volume for graphitization under 3–5 kbar were estimated to be 80–120 kcal/mol, and −7–−9 cc/mol, respectively.