Activation studies of vapor-grown carbon fibers with supercritical fluids

The objective of this research was to investigate the feasibility of activa ting vapor-grown carbon fibers (VGCFs) with supercritical fluids (SCFs). VG CFs with a mean diameter of 150 nm and a length of a few micrometres were t reated using water or carbon dioxide under supercritical conditions for 10 min. Hydrochloric acid and nitric acid were utilized for the oxidation of t he VGCFs prior to the treatment of the SCFs. The nitrogen adsorption result s at 77 K showed that the BET surface area of the treated VGCFs can be incr eased from 9 m(2)/g to about 35 m(2)/g. The adsorption of benzene vapor on the VGCFs revealed that the adsorption capacity of benzene was enhanced aft er the activation treatments. However, in comparison with commercial activa ted carbon fibers (ACF), the adsorption amount of benzene is still relative ly low. Based on the CHN elemental analysis and X-ray photoelectron spectro scopy (XPS), it was found that oxygen compounds were contained on/in the VG CFs after the treatment by oxidation and by SCFs. (C) 2001 Elsevier Science Ltd. All rights reserved.