The HREM observation of cross-sectional structure of carbon nanotubes

Cross-sectional structural features of Carbon nanotubes have been investigated by high resolution electron microscopy (HREM). Carbon nanotube-bundles with 0.2-0.6 mm in diameter and 5-10 mm in length were produced by means of an arc-discharge method, which is suitable for preparing TEM cross-sectional samples of carbon nanotubes. Our HREM observations have shown that most of carbon nanotubes have a polyhedral and elliptical shape in a cross section, and there are many defects in the microstructure of carbon nanotubes, including edge-type dislocations and variable spacing between adjacent tube sheets, revealing that the seamless cylindric and scroll-shaped graphene sheets co-exist within the same nanotube. The abnormal structure features are closely related to the non-equilibrium growth conditions of carbon nanotubes in the arc-discharge process, and also to the accommodations of various strains taking place simultaneously in tube sheets. (C) 1997 Elsevier Science Ltd.