Development of pore structure in carbon cloth by HNO3 activation

Abstract

A study has been made of the changes in the adsorptive behaviour of a carbon cloth with aqueous oxidative activation. It has been demonstrated that molecular-sieve action initially present in the cloth can be eliminated by progressive activation but eventually restored after the total pore volume of the cloth has been greatly increased. A comparison with samples produced by thermal air oxidation indicates that the restoration of molecular-sieve action during aqueous oxidative activation is probably due to a slow removal of carbon from the organized skin of the fibres, which is graphitic or polymeric in nature, and rearrangement of the skin into a more compact structure. A similar process probably occurs during air activation except that much carbon is also lost from the polymeric layers with a consequent pore enlargement.