Characterization and adsorption modeling of silicon carbide-derived carbons

Abstract

We present characterization results of silicon carbide-derived carbons (Si-CDCs) prepared from both nano- and micron-sized ßSiC particles by oxidation in pure chlorine atmosphere at various synthesis temperatures (600-1000 °C). Subsequently, the adsorption modeling study of simple gases (CH₄ and CO₂) in these Si-CDC samples for a wide range of pressures and temperatures using our Finite Wall Thickness model [Nguyen, T. X.; Bhatia, S. K. Langmuir 2004, 20, 3532] was also carried out. In general, characterization results showed that the core of Si-CDC particles contains predominantly amorphous material while minor graphitization was also observed on the surface of these particles for all the investigated synthesis temperatures (600-1000 °C). Furthermore, postsynthetic heat treatment at 1000 °C for 3 days, as well as particle size of precursor (ßSiC) were shown to have slight impact on the graphitization. In spite of the highly disordered nature of Si-CDC samples, the adsorption modeling results revealed that the Finite Wall Thickness model provides reasonably good prediction of experimental adsorption data of CO₂ and CH₄ in all the investigated Si-CDC samples at the temperatures of 273 K, 313 K, and 333 K for a wide range of pressure up to 200 bar. Furthermore, the impact of the difference in molecular size and geometry between analysis and probing gases on the prediction of the experimental adsorption isotherm in a disordered carbon using the slit-pore model is also found. Finally, the correlation between compressibility of the Si-CDC samples under high pressure adsorption and their synthesis temperature was deduced from the adsorption modeling.