A new method was reported for creating crystal defects on the surface of multi-walled carbon nanotubes, using cobalt oxide as the oxidant for breaking up the carbon surface. The air oxidation of CoO deposited onto multi-walled carbon nanotubes created various kinds of defect on their surface. Transmission electron micrograph images showed clear defects such as broken crystal lines and asymmetrical walls after air oxidation. X-ray powder diffraction data showed that CoO on multi-walled carbon nanotubes changed into Co3O4 following air oxidation. After removing Co3O4 from multi-walled carbon nanotubes by acid treatment, defective multi-walled carbon nanotubes were obtained and exhibited defects giving clear traces of where cobalt oxide had existed. This resulted from the reaction of air oxidation of CoO and carbon reduction of Co3O4, leading to the crystallinity defect of multi-walled carbon nanotubes.

Crystal Defects on Multi-Walled Carbon Nanotubes by Cobalt Oxide. D.H.Kim, K.Waki: Journal of Nanoscience and Nanotechnology, 2010, 10[4], 2375-80