The carbon nanotubes formed at the cathode of the electric arc discharge apparatus used to produce fullerenes were imaged using high-resolution transmission electron microscopy. Besides nanotubes, two other phases which were frequently the main components in the deposits were detected: concentric polyhedral carbons and microporous carbon. The nanotubes were a few nanometers to a few tens of nanometers in diameter and up to a few micrometers in length. They were often closed by two or three parallel sheets bent at a limited number of angles. These values were correlated with typical defects occurring during the growth of aromatic layers. Primary defects with one atom missing (pentagon) or in excess (heptagon) and also more complex combinations of pentagons and heptagons were identified. It was deduced that the general conditions for closing the nanotubes were given by Euler’s rule (the presence, at each tip, of six pentagons).

Electron Microscopy, Growth and Defects of Carbon Nanotubes. C.Clinard, J.N.Rouzaud, S.Delpeux, F.Beguin, J.Conard: Journal of Physics and Chemistry of Solids, 1994, 55[7], 651-7