The effect of hydrogen on the formation of carbon nanotubes and fullerenes
- PDF / 1,722,401 Bytes
- 7 Pages / 576 x 792 pts Page_size
- 98 Downloads / 231 Views
M. Mesleha) Materials Research Center, Northwestern University, Evanston, Illinois 60208
M. F. Jarrold Department of Chemistry, Materials Research Center, Northwestern University, Evanston, Illinois 60208
V. P. Dravid Department of Materials Science and Engineering, Materials Research Center, Northwestern University, Evanston, Illinois 60208
J. B. Ketterson Department of Physics and Astronomy, Materials Research Center, Northwestern University, Evanston, Illinois 60208
R. P. H. Chang Department of Materials Science and Engineering, Materials Research Center, Northwestern University, Evanston, Illinois 60208 (Received 13 February 1995; accepted 24 April 1995)
A novel method to synthesize "clean" carbon nanotubes with relatively high yield in a hydrogen arc discharge has been developed. The quality and yield of the tubes depend sensitively on the gas pressure in the arc discharge. Sharp, open-ended nanotubes with clear lattice fringes at the edges and empty interiors have been observed. The existence of these frozen-open-ended tubes as part of nanotube-bundles provides evidence for an open-ended growth model for nanotubes. Using time of flight mass spectrometry, it was found that fullerenes, such as Cgo and C 70 , are almost absent from the soot collected in the hydrogen arc discharge. The effect of hydrogen on the formation of fullerenes, both in the laboratory and in space, will be discussed.
I. INTRODUCTION Since the discovery of buckyballs 12 and buckytubes,3-4 a great deal of effort has been made to synthesize, process, and purify such materials and understand mechanisms for their formation. Inert gases, such as helium and argon, have been extensively used to produce buckytubes in macroscopic quantities. All experiments reported to date have shown that carbon nanotubes produced in inert gas arcs are usually capped at the ends.5"9 The nanotube ends can be opened by postoxidation; however, the tubes then become filled with carbonaceous debris. Thus filling these open-ended tubes with other material has proven to be difficult. Other problems with carbon nanotubes synthesized in inert gases include the formation of highly defective tubes containing amorphous carbon deposits (on the outer surface and inside the tubes), and the presence of discontinuous graphite sheets.10 At present, the
a) NSF
Research Experience for Undergraduate participant. J. Mater. Res., Vol. 10, No. 8, Aug 1995
http://journals.cambridge.org
Downloaded: 17 Mar 2015
important challenge, both for characterization and practical applications, is to find a simple and effective method to synthesize high quality carbon nanotubes. Several growth models for carbon nanotubes have been proposed for multishell tubes, including openended growth,17 close-ended growth,11 "inside out" growth,12-13 and "outside in" growth.9 But the actual growth processes for carbon nanotubes remain unknown In the fullerene generation process it is believed that the inert gas as a "quencher" for the carbon vapor, which attains supersaturation followed by nucleation an
Data Loading...
