X-ray small-angle scattering of non-graphitizable carbons

The small-angle scattering of a non-graphitizable carbon produced from polyacrylonitrile is studied. The evaluation of the scattering data has been based on recent developments in small-angle scattering theory. The results show the existence of a micropore system with diameters in the 10–30 Å range. The average pore diameter increases linearly with heat-treatment temperature from 2000 to 3000°C. The volume fraction of micropores determined by absolute intensity measurements varies between 0.17 and 0.25 and is equal to, or smaller than, the volume fraction of pores inaccessible to helium. The pore shapes are very probably irregular polyhedra bounded by graphitic layer planes. A second component of the small-angle scattering can be detected and separated from the scattering of the micropores. This component is due to density fluctuations in the bulk of the carbon material and is produced by the fluctuation of the interlayer spacing and the fluctuation of the layer diameter in a given stack of layers.