Studies on the Graphitization. I. Changes of Crystallinity, Diamagnetic Susceptibility and Electrical Conductivity in the Process of Graphitization

Abstract

Three sorts of carbon black, two sorts of pitch coke, violanthrone, and polyvinyl chloride have been subjected to heat treatment up to 3000°C. Changes in crystallinity during the graphitization have been studied by X-ray referring to inter-layer spacings and growth of crystallites. It was found that pitch cokes are graphitized with more facility than carbon blacks, and the other two substances are intermediate.The magnetic susceptibility is determined solely by the size of plane molecules (La) irrespective of the sort of carbons, and tends to a limiting value −6.5×10−6 per gram which is coincident with the value of natural graphite, when La grows above 130 Å.The electrical resistivity decreases as growth of crystallites, but there is a region when La becomes above 40 Å, where it tends to a nearly constant value for each carbon. Those values are different among the groups of carbons, and graphitized pitch cokes have less resistivity than graphitized carbon blacks. It was discussed that fine structures of multi-crystalline states are reflected on the resistivity.