Carbon structures in silicon carbide derived carbon

Carbide derived carbon (CDC) produced by etching SiC in halogens has been investigated using transmission electron microscopy (TEM). Depending on experimental conditions, CDC may contain sp(3)- or sp(2)-bonded carbon phases. Amorphous carbon, poorly ordered turbostratic carbon with lattice spacing exceeding values of 0.35 mn as well as highly ordered graphite were observed. sp(3)-Bonded structures consist of mainly lonsdaleite and cubic diamond nanocrystals. Hexagonal diamond polytypes and n-diamond have been synthesized. During the annealing process, diamond nanocrystals eventually transform to sp(2)-bonded carbons. The transformation process of hexagonal diamond nanocrystals produces spherical onion type structures. These structures appear either hollow or dense. The latter shows a decrease in lattice spacing compared to d/n values for graphite. Graphitic structures include multi-wall nanotubes, polyhedral particles and ribbons. The graphitization during chlorination of samples may eventually lead to the formation of planar graphite. (c) 2006 Elsevier B.V. All rights reserved.