SOME ADVANCES IN X-RAY DIFFRACTOMETRY AND THEIR APPLICATION TO THE STUDY OF ANTHRACITES AND CARBONS

Special Research Report SR-25 The ultimate aim of the research of which this report is intended to be a contribution is to develop a reliable method for the measurement of crystal sizes and crystal size distributions in anthracites. The problem has been studied using X-ray diffraction methods and the emphasis throughout has been on the accurate measurement of the intensity of the X-rays scattered by carbonaceous solids; such work is a prime requirement for a detailed crystallographic analysis. The correct procedure for the determination of interlayer spacing and crystal size from the X-ray line broadening has been outlined; it is shown that the more rapid procedure normally employed gives erroneous results. It has not, unfortunately, been found possible to use satisfactorily the method devised by Diamond for the determination of crystal size distributions. It is shown that the results given by this method are very sensitive to perturbations in the X-ray intensity profile, and the factors influencing this have been considered. In addition, a number of improvements have been made in the experimental technique - these are described in detail in the reporL A new method has been proposed for the study of preferred orientation of crystallites in thin samples of anthracites and carbon blacks. Experimentally, this was readily applied to the blacks; technical difficulties encountered in the case of the anthracites could not be overcome. It was concluded that while at present crystal sizes must continue to be obtained from X-ray line broadening, more precise methods such as that devised by Diamond must be pursued if detailed information on crystal size distributions is to be obtained. For this purpose continued research on precision diffractometric techniques is desirable.