Processing of carbide-derived carbons with enhanced porosity by activation with carbon dioxide

Abstract

Carbide-derived carbon (CDC) materials were synthesized by high temperature chlorination of biomorphic TiC and SiC ceramic structures. CDC allows the control over the pore size by choosing an appropriate carbide precursor as well as the reaction temperature. However, the pore volume is limited by the fraction of metal in the carbide structure. Since activation procedures such as treatment in CO 2 significantly increase the porosity of the carbon structure it is applied to pyrolyzed paper preforms and CDC materials. The activation procedure raises the specific surface area (SSA BET) and the pore volume of the carbon-based materials. The effect of variation of activation conditions like temperature, time and flow rate of CO 2 on the resulting pore structure is investigated. SSA BET up to 2300 m 2 g −1 and pore volumina of about 1.3 cm 3 g −1 are obtained. Activation times up to 6 h increase the micropore volume whereas longer activation times result in a decreased micropore volume by simultaneous transformation into mesopores. Activated CDCs from biomorphic ceramics are structured materials compared to powders described mainly in the literature.