Effect of Geometrical Factors on the Shape of Diffraction Profile for Natural Graphite and Petroleum Coke

Abstract

Half maximum breadth (Bo) of a diffraction profile of carbon increased with the increase of sample thickness. When sample thickness was less than 0.2mm, Bo value came closely to the value obtained by the reflection only from the surface. When silicon powder was used as an internal standard, Bo value of (002) diffraction line was almost constant regardless of sample thickness. But Bo value of (004) and (110) lines showed still some broadness due to penetration of X-ray beam into sample, even if silicon powder was used as an internal standard. Therefore, it is concluded that it is preferable to use sample thickness less than 0.2mm and to use slit width as small as possible in order to reduce low absorption effect of the sample.Shape of (00l) diffraction profiles was also affected by the reflection from an internal well-oriented layer in the sample which might be produced during mounting process. If the internal well-oriented layer is made at a distance from the rotation axis, the reflection from the layer appears at displaced position, and the reflection overlaps the profile which is reflected from surface layer.