Processing of carbide-derived carbon (CDC) using biomorphic porous titanium carbide ceramics

Biomorphic porous TiC and TiC/TiO2 ceramics were covered with highly porous carbon, so-called carbide-derived carbon (CDC), by selective etching of Ti from TiC with chlorine containing gas in a temperature range 400-1000 degrees C. The etching rate of TiC is strongly affected by the chlorine concentration, but only slightly by the reaction temperature. No correlation was found between etching rate of TiC and specific surface area (SSA) of the resulting CDC with respect to temperature. Kinetic investigations show that for up to 80 min the etching process is controlled by the chemical reaction. At longer times a diffusion limitation has to be taken into account. Addition of hydrogen to the etching gas enhances the diffusion of the chlorine molecules, so that no diffusion limitation was observed. Microporous carbon with narrow pore size distribution was obtained at temperatures ranging from 400 to 800 degrees C. Treatment at higher temperatures leads to formation of mesopores. The CDC produced by chlorination of TiC at 400 degrees C is amorphous. Increased reaction temperature and addition of hydrogen to the chlorine gas lead to formation of regions with higher order like onion carbon and graphitic ribbons. The CDC coated TiC/TiO2 ceramics with predominantly anatase phase show enhanced photo catalytic activity. (c) 2007 Elsevier Ltd. All rights reserved.