Mosaic Texture of Graphites

Abstract

CRYSTAL sizes in graphitic carbons are commonly in the μ or sub-μ range. The average dimensions of the crystallites (that is, the parallel-layer groups of condensed aromatic ring networks) in any particular material are usually deduced from measurements of the widths of X-ray powder diffraction maxima. Although the measurements are complicated by the presence of stacking disorders, techniques exist¹ for eliminating the effects due to these. The dimensions thus obtained are : La the average diameter of layer-network over which there is considerable perfection, t the average height of parallel-layer group over which the stacking is fully ordered, Lc the total height of the group irrespective of the presence of disordered (turbostratic) stacking. With crystallite dimensions greater than about 200 Å. the accuracy of the determination depends very considerably, and to an extent increasing rapidly with crystal size, on the corrections for extraneous (instrumental, absorption, etc.) line-broadening effects. Nevertheless, for good natural graphites the crystallite dimensions are consistently found to be not more than a few thousand Å. (ref. 2 and Steward, E. G., and Cook, B. P., unpublished work). For artificial graphites the dimensions are usually less than 1000 Å. (refs. 2,3,4 and Steward, E. G., and Cook, B. P., unpublished work).