Size and shape of crystallites and internal stresses in carbon blacks

The effect of graphitization and pressure treatment on the microstructure and internal stresses of carbon blacks is studied by X-ray diffraction peak profile analysis. The Fourier transforms of the experimental line profiles are fitted by theoretical functions based on the model of the microstructure. In this model the crystallites are ellipsoids with log-normal size distribution. It was found that in raw carbon blacks crystallites have lateral dimensions twice the size in the hexagonal c direction. During graphitization process caused by heat treatment the crystallites grow and their shapes becomes more spherical. The pressure has no effect on the size and shape of crystallites. The internal strains and stresses in the crystallites are determined from the X-ray diffraction profiles by the Griffith model. It was established that the internal stresses increase due to pressure treatment while they are reduced by graphitization.