Effect of Coexisting Minerals on Graphitization of Carbon under Pressure. III. Accelerating Effect of Calcium Hydroxide

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Abstract
The polyvinyl chloride coke was heat-treated under the pressure of 3.2 kbar at 600–850°C for 20–240 min in a simple piston-cylinder type vessel, being sandwiched between two disks of calcium hydroxide. By electron microscopic observations, particles having the six-fold symmetry diffraction pattern of graphite single crystal were found besides particles of amorphous carbon even in the specimen heat-treated at temperature as low as 600°C. Above 800°C, the sharp peak corresponding to the graphitic component appeared on (002) diffraction profiles, overlapping with the broad band of the turbostratic component. The formation of the graphitic component seems to be related to the recrystallization of coexisting calcium hydroxide, as in the case of limestone and calcium carbonate. However, the fact that a small amount of free calcium oxide formed by the decomposition of calcium hydroxide was detected in the heat-treated carbon specimens suggests a chemical theory for the accelerating effect of calcium compounds on the graphitization of carbon under pressure.