Catalytic Synthesis of Single-Layer Carbon Nanotubes with a Wide Range of Diameters
We have synthesized single-layer carbon nanotubes by co-vaporizing cobalt with carbon in an arc fullerene generator and have identified conditions that lead to high yields. The diameter distribution of the tubes and their morphologies are studied using transmission electron microscopy. For nanotubes produced using cobalt and carbon, the tube diameters range from 1 to 2 nm with distribution peaks at 1.3 and 1.5 nm. When sulfur is added to the carbon and cobalt, production of single-layer nanotubes is enhanced and the tubes have a wider range of diameters (from 1 to 6 nm). The diameter distribution for these nanotubes shows prominent peaks at 1.3 and 1.5 nm and additional maxima at 2.7 and 3.6 nm. Cobalt-containing crystallites, some encapsulated in graphitic polyhedra, are produced with the nanotubes and are found in the soot away from the cathode.
© 1994 American Chemical Society. Received: March 4, 1994; In Final Form: April 22, 1994. We thank R. Savoy for X-ray data. We also thank M. Endo, S. Iijima, A. Nazzal, R. D. Johnson, P. van Loosdrecht, and K. Tanigaki for helpful discussions. This research is partially supported by the NSF (ASC-9217368) and by the Materials and Molecular Simulation Center.