‘Macrocrystalline’ Carbon

Abstract

FROM a mathematical analysis of the X-ray diffraction patterns of products obtained at various stages during the graphitization of carbon, Franklin¹, and later Houska and Warren², have shown that only two carbon interlayer spacings are possible : 3.35 A. for the orientated stacking in graphite, and 3.44 A. for the random orientation of the planes in carbon. Precise measurement of the interlayer spacing of cokes and carbons is not possible because of the very diffuse nature of the diffraction maxima, and it is therefore of interest to report that ‘macrocrystalline’ carbon with an interlayer spacing of 3.45 A. has been prepared by sublimation of artificial graphite under high vacuum. The material, as deposited, has a nodular surface with a grey metallic sheen. It has a low porosity, a hardness of between 1 and 2 on the Moh scale (compared with a value of less than 1 for graphite) and a true density of 2.22. The carbon content is greater than 99 per cent and the ash less than 0.4 per cent. The carbon planes of the individual crystallites are found to lie very approximately parallel to the surface on which deposition occurs, and the crystallite size, as shown by the sharpness of the lines in the diffraction pattern, is similar to that of artificial graphite. A diffraction pattern of this material together with patterns of graphite and a sample found to be a mixture of the two phases is shown in Fig. 1.