Chlorine fixation on anthracites and carbon blacks and its effect on electrical resistivity

Abstract

A medium and a high volatile matter (VM) anthracite and a medium and low VM carbon black have been exposed to chlorine gas, at one atmosphere pressure, at temperatures between 200–1400°C. For the high VM anthracite, chlorine fixation occurred at low heat treatment temperatures (HTT) primarily by substitution of chlorine for hydrogen in aliphatic groups. At higher HTT, fixation occurred primarily by substitution of chlorine for hydrogen at the edges of aromatic platelets. For the medium VM anthracite, chlorine fixation at all HTT occurred primarily by the latter process. For the medium VM carbon black, chlorine fixation at all HTT occurred primarily by substitution of chlorine for hydrogen at the edges of aromatic platelets and by addition of chlorine on new active sites produced upon removal of the oxides of carbon from the edges of aromatic platelets. Little fixation of chlorine on the low VM carbon black occurred. Electrical resistivities of samples heated in chlorine were compared with samples heated in nitrogen. The atmosphere used influenced the change in resistivity with HTT. The effect of atmosphere on resistivity is explained on the basis of the chlorine fixation results.