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CARBONNANOSTRUCTURES
Figure 5.10. Illustration of predicted structure of the N2, , molecule calculated by density
functional theory. (F. J. Owens, unpublished.)
dodecahedral structure shown in Fig. 5.10. The calculation also revealed that the
cluster would be a very powerful explosive, about 3 times more powerful than the
presently most energetic material. However Nzo may be very difficult to synthesize.
5.4. CARBON NANOTUBES
Perhaps the more interesting nanostructures with large application potential are
carbon nanotubes. One can think of a carbon nanotube as a sheet of graphite rolled
into a tube with bonds at the end of the sheet forming the bonds that close the tube.
Figure 5.1 l a shows the structure of a tube formed by rolling the graphite sheet about
an axis parallel to C-C bonds. A single-walled nanotube (SWNT) can have a
diameter of 2 nm and a length of 100 pm, making it effectively a one dimensional
structure called a nanowire.
5.4.1. Fabrication
Carbon nanotubes can be made by laser evaporation, carbon arc methods, and
chemical vapor deposition. Figure 5.12 illustrates the apparatus for making carbon
nanotubes by laser evaporation. A quartz tube containing argon gas and a graphite