Effect of lattice structure of silicon carbide on crystal formation of carbide-derived carbon

Nanostructured carbide-derived carbons (CDCs) were synthesized from hexagonal SiC (α-SiC) and cubic SiC (β-SiC) powders via chlorination at temperatures between 900 and 1200°C. The content of the sp2- and sp3-bonded carbon phases and their crystallinity were analyzed by Raman spectroscopy. The nanocrystalline phases of the synthesized CDCs were observed and characterized by transmission electron microscopy and electron energy-loss spectroscopy. The morphology of CDCs showed interesting features that varied with the starting SiC powder. Diamond nanocrystals were more frequently observed in α-SiC-derived carbons than in β-SiC-derived carbons, and the rate of graphitization was affected by the SiC polytype, synthesis temperature and hydrogen content. A possible mechanism responsible for the observed results was also investigated.