Kinetics of intercalate desorption from carbon fibers intercalated with bromine

This paper reports the kinetics of intercalate desorption from pitch-based carbon fibers intercalated by exposure to Br₂. The kinetics was studied by thermogravimetric analysis of brominated Thornel P-100 and P-X-7 carbon fibers of Amoco Corp., as P-X-7 was more graphitic than P-100. Comparison was made with previous kinetic data on highly oriented pyrolytic graphitic (HOPG) intercalated with bromine. The activation energies of desorption below 100°C were 9, 12, and 17 kcal/ mol Br₂, respectively, for P-100, P-X-7, and HOPG. The values above 100°C were 8, 5, and 4 kcal/ mol Br₂, respectively, for P-100, P-X-7, and HOPG. A high degree of order of the intercalate increases the activation energy below 100°C, whereas a high degree of graphitization decreases the activation energy above 100°C. Brominated P-100 retained a stable bromine concentration of 17.5 wt.% up to at least 200°C. This thermal stability is attributed to the relatively high activation energy of desorption of brominated P-100 above 100°C.