Activated Carbon Fibers Prepared from a Phenolic Fiber by Supercritical Water and Steam Activation

Supercritical water (SCW) and steam were used to prepare activated carbon fibers (ACFs) to study the different behaviors of these two agents. The results showed that activation with SCW is much faster than with steam and that the lower activation energy observed when SCW is used suggests that the mechanism of gasification with SCW and with steam is different. All the ACFs prepared showed a highly developed micropore structure, with a large specific surface area. The ACFs prepared with SCW had a smaller micropore volume with a broader pore size distribution. In contrast, the ACFs prepared with steam had many small micropores. With SCW, external gasification was greater than with steam, fibers with smaller diameters being obtained, although these latter maintained their structure and their mechanical properties were scarcely altered. However, with steam, external gasification was less marked, but the fibers became fragile and friable.