Effect of Pressure on Graphitization of Carbon. VI. Normal Pressure Heat Treatment of Soft Carbon Pre-Heat-Treated under High Pressure

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Abstract
Three different samples of polyvinylchloride coke (designated as N-1, N-2, and N-3 which were pre-heat-treated at 1470, 1590, and 1620°C, respectively, under 5 kbar) were heat-treated in a flow of nitrogen under normal pressure. Process of graphitization in these samples was investigated by analyzing (004) diffraction profile. Sample N-1 has a symmetrical profile and consists only of the trubostratic component As. Samples N-2 and N-3 have a composite profile and are composed of the turbostratic component As and the graphitic component Gs. Only the profiles corresponding to the turbostratic component As of these samples shift gradually to higher angle together with sharpening when the heat treatment temperature under normal pressure increases. Changes in c0-spacing and crystallite size Lc of the component As with heat treatment temperature follow the same course of change as in those of the original polyvinylchloride coke. However, heat treatment of the sample under normal pressure did not affect the quality and quantity of the component Gs which had been formed by the pre-heat-treatment under high pressure. These results indicate that the pre-heat-treatment of soft carbon under high pressure has no accelerating effect on the graphitization of the carbon in the subsequent heat treatment under normal pressure.