Cooperative accelerating effect of calcium carbonate and gaseous nitrogen on graphitization of carbon

Abstract

Heat treatments of a Polyvinylchloride coke in the presence of calcium carbonate were carried out under flow of nitrogen or argon. Under the flow of nitrogen, a graphitic component appeared above 1700°C and increased rapidly with HTT. Flaky particles giving graphite diffraction pattern were frequently found under electron microscope, some of them having singular discoidal appearance. Under the flow of argon, the graphitic component appeared above 1900° C and its amount was relatively small, less than 10% at 2000° C. Heat treatments of calcium carbide were also performed under the same condition. Graphite was obtained even at 1000° C and its amount was much larger under flow of nitrogen than under argon. The results suggest that there must be a cooperative accelerating effect on the graphitization of carbon of the calcium carbonate and gaseous nitrogen, through the calcium cyanamide process.