Effect of Graphitization on the Structures and Conducting Property of Carbon Nanotubes

Turbostratic carbon nanotubes (CNTs) were treated in nitrogen atmosphere at 2700 Higha2resolution transmission electron microscope (HRTEM) was used to investigate the structural changes of CNTs. Meanwhile, the conducting property was measured via a selfa2built setup installed in TEM. The structures of CNTs are found to change into bambooa2like or tubular cones after graphitization. The apex angles of cones rang from 10 o 30 and the tubular diameter ranges from 10nm to 40nm. Electron diffraction analysis reveals that an additional overlap angle is involved in the disclination operation of cones, suggesting the helicala2conical structural characteristics of CNTs. The highly curved filamental structures are stabilized via interlayer coincidence site lattices of 3a2, a2, and 9a2type. The conducting measurement indicates that the helical conical CNTs are semiconductors.