Study of the Evolution of a Graphitizing Carbon During Thermal Treatment Using the Radial Distribution Function

The transient presence of interstitial carbons during transformation of a coke into graphite is inferred. A peak corresponding to an abnormal C-C distance 1.90 A. is observed for samples heat treated to 2050 and to 2100 C. This distance is assigned to interstitial carbons located 1.2 A. above or below the hexagonal C layers at the center of hexagonal rings. The peak does not appear in the radial distribution function obtained either for 1700 or 2500 C. At "low temperature" the interstitials are probably randomly distributed while at 2500 C they are removed by the graphitization process. From other peaks observed in the distribution function the changes of the C-C distances in the rings can be determined and the dis tortions within the layers estimated. Observations agree with the graphitization mechanism proposed by Mering. 12 ref.--EPAA/AF.