We report the unexpected synthesis of SiC nanorods during thermally annealing single-walled carbon nanotube sheets (SWNTs) at 1000 degreesC between two silicon wafers. The exterior layers of the carbon nanotube sheets were converted into a network of SiC nanorods, while the carbon nanotubes interior to the sheet remain unchanged. The nanotube sheets that underwent this reaction were comprised of small diameter nanotubes made by a high-pressure carbon monoxide process (HiPco), which contain iron catalyst. Using the same reaction conditions, SiC formation was not observed for sheets of purified, larger diameter nanotubes made by laser ablation, which contained a small amount of residual metal catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.