The thermal expansion of the interlayer spacmg bnd the intensity ratio ~(004)/1(00?) of the diffraction lines of graphite-bromine residue compounds were measured at temperature5 between room temperature and 700ยฐC by using a high temperature X-ray diffractometer.
At about 330ยฐC. both the c-spacing and the intensity ratio of diffraction lines were found to show a break. That i, the [.-spacing of the residue compound which shows normal linear expansion below 33O"C, has a considerably smaller thermal expansion coefficient between 330 and 500ยฐC. Over this temperature. the c-spacing of the residue compound becomes nearly equal to that of original graphite. On cooling, the anomaly in the reverse direction occurs between 330 and 100ยฐC. The intensity ratio of the diffraction line5 of the residue compound is smaller below 330ยฐC ah compared with that of original graphite. but above SOO'C, both are almost rhe same. The thermal diffusivity and the heat-capacity studie, were alro performed in the same temperature range. The thermal diffusivity curve shows a break, and the heat-capacity curve ha9 a small hump around 330ยฐC. At temperatures higher than 330ยฐC. both of these properties agree with those of original graphite. The structure of graphite-bromine residue compound and the nature of its change at high temperatures are discussed. and a model to explain all of these peculiar behavior of the residue compound iq proposed.