73. Effects of some process temperatures on radiation induced contraction of graphite

Abstract

Abstract The dimensional change that occurs during the thermal processing of graphite and the subsequent dimensional change that occurs when graphite is irradiated have been explored. Raw material bias was removed by fabricating seven sets of graphite from one formulation. A systematic dimensional change during processing was achieved by controlling the graphitization rate to the same final temperature. A second series of samples is used to demonstrate the degree to which binder graphitization (or binder heat-treatment) determines radiation induced dimensional change. The filler for the formulation was graphitized to 2900°C and then mixed with a graphitizable binder. Subsequently, the samples were heattreated to temperatures appropriate for a broad range of crystallite development in the binder phase. As the crystallite size in the filler is the same, differences in radiation induced contraction can be attributed to the binder phase. The dimensional stability of both perpendicular and parallel orientations under irradiation shows a definite effect of the binder graphitization. However, unlike a system in which all constituents have the same graphitization temperature, this series does not show a uniform increase in contraction rate with decreasing graphitization temperature. For this series, there is little effect of heat-treatment temperature down to 2000°C; at heat-treatment temperatures below 2000°C there is a sharp increase in contraction rate for both orientations.