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.

	IMAGE BY BINGQING WEI

The strands, 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 ºC 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.

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 Poulin.

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.

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Copyright © 2002 American Chemical Society