Doping of Bromine into Carbon Materials with Different Heat-Treatment Temperatures.

Abstract

Behavior of bromine doping into carbon materials with different heat-treatment temperatures (HTT) from 1000 to 2800°C were investigated, together with the characteristics such as XRD patterns, Raman spectra and electric conductivities of the respective bromine residue compounds prepared by debromination of the doped samples. It was found that there are two different cases in the behavior of the carbon materials for bromine doping depending on their HTTs; one is the carbons with high HTT (HTT ≥ 2000°C), the other those with low HTT (HTT ≤ 1900°C). The carbons of high HTT group form intercalation compounds with compositions up to C 10 Br, and considerable fractions, such as 13-25%, of the intercalated bromine remain in the interlayer space of graphite after the debromination process, thus forming the bromine residue compounds. On the other hand, the carbons of HTT ≤ 1900°C, except for HTT1000, absorb only small amounts of bromine, which are almost completely expelled by the debromination process. They apparently do not form residue compounds with bromine. The carbon with HTT1000 was found to have an unique character: It absorbed an appreciable amount of bromine and the remaining fraction of the bromine after debromination was rather large, although the XRD pattern and the electric conductivity were unchanged. It is thus suggested that the remaining bromine may exist on the edge of the crystallites by forming weak bonding with carbon atoms.