Crystallite size effects on the radial distribution analysis of carbon fibres

Radial distribution functions obtained from polycrystalline materials are influenced by both the atomic bonding and the crystallite size. A modified radial distribution function has been deduced which is independent of crystallite size and a function solely of the bonding within the crystallite. This modified radial distribution function has been computed for various samples of carbon fibre material, produced by pyrolysis at different temperatures, and the materials have been shown to be almost identical in atomic structure although differing considerably in crystallite size. For the particular ease of a layer structure a planar distribution function has been derived which has certain advantages over the radial distribution function at large atomic separations. The agreement between the measured planar distribution function for the carbon fibre material and that calculated for graphite is good.