A high temperature X-ray diffractometer attachment was used to study the progress of graphitization of two cokes. By devising a quick electrical heating technique and using rapid scanning, the profiles of the ( 002), (loo), (lOl), ( 004), ( 110) and ( 112) reflections were measured as a function of time (l-60 min) under isothermal conditions at various temperatures (lOOO-2600ยฐC). Major changes in the widths of the ( 002), ( 004) and ( 110) reflections and in the positions of the (002) reflections occurred mainly within the first 10 min of isothermal heat-treatment.
In contrast, the progress in the formation of the three-dimensional ( 101) and ( 112) reflections continued up to 1 hr of heat-treatment time. The three-dimensional alignment was not discernible below 2300ยฐC but proceeded rapidly at 2 2500ยฐC. Upon cooling to room temperature the line-widths of the ( 002) and ( 110) bands remained invariant whereas those of the ( 112) and ( 004) bands showed decreases, 15% and lo%, respectively. The decrease suggests a stress relief upon cooling. The widths of the (004) bands of samples heat-treated to 2500ยฐC were about twice those of the (002) reflections, indicating a rather severe strain in the lattice along the c-axis. Intensities of the ( 002) and ( 004) reflections, especially the latter, of samples heat-treated to 2500ยฐC increased upon cooling, indicating a pronounced Debye-Waller effect at high temperatures. Because of the severe strain in the lattice, it was not possible to ascertain if temperature diffuse scattering influenced the widths of the bands.