Anisotropic small-angle scattering of X-rays from a natural graphite and pyrolytic carbons

Abstract

The pyrolytic carbons have been prepared by pyrolysing benzene varpor mixed with nitrogen or argon in an atmospheric pressure at 1600°C. The samples used in this study are as-deposited pyrolytic carbons, pyrolytic carbons heat-treated at 2200°C in vacuum and a pressed disk of Madagascar graphite having high degree of preferential orientation. After the heat-treatment, the sizs of crystallite determind from the line-width of 0002 line have increased by about three times, while the degrees of preferential orientation have decreased to some extent.
The patterns of small-angle scattering were obtained by using pin-hole collimating system. When the layer in the specimen is parallel to the incident X-rays, the patterns are elongated to the direction normal to the layer and shortest in the direction parallell to the layer. In the case of graphite the asymmetry is especilly large. When the layer is normal to the X-rays, circular patters are obtaind and further it has been found that the radial intensity distribution in such a pattern is equal to the intensity distribution along the minimum radius of the asymmetrical pattern of the same specimen. The result obtained is accounted for by assuming plate-like particles.