Nanotube Strands Are Centimeters
Growing carbon nanotubes as long as 1
mm was once considered a big deal. For many applications, though,
much longer tubes are required. Such tubes are now a step closer. A
China-U.S. team has synthesized single-walled carbon nanotube (SWNT)
strands some 20 cm long [Science, 296, 884 (2002)].
These are the longest and strongest assemblies thus far made
entirely of carbon nanotubes, according to one scientist familiar
with the report.
which look and feel much like human hair, were prepared by
mechanical engineering professor Dehai Wu of Tsinghua
University, in Beijing, and coworkers by pyrolyzing n-hexane at
1,150 ēC in the presence of ferrocene catalyst and thiophene in
flowing hydrogen gas. The strand shown here consists of hundreds of
nanotubes and is about 10 mm wide.
IMAGE BY BINGQING
Characterization of the nanotube strands was carried out by
materials engineer Pulickel M. Ajayan and coworkers at Rensselaer Polytechnic
Institute. They find that the strands are about five times
stiffer than SWNT fibers and ribbons spun from nanotube/surfactant
slurries reported in 2000 by a French group led by Philippe
Nevertheless, the properties of Wu's strands still fall far short
of the ideal predicted values, undoubtedly because of defects in the
strands. Researchers would get closer to the predicted values for
nanotube properties if they could just figure out how to make
aligned nanotubes extend continuously from one end of a strand to
the other, Ajayan says.
Now that would be a big deal.