Carbon Nanotubes

You learned on the C₆₀ pages that fullerenes tend to form by "rolling up" a graphite sheet and adding pentagons to achieve curvature. What if you just roll the sheet like a cylinder, then cap off the ends with pentagon-curved hemispheres?

You have a carbon nanotube. These materials are quite different from the traditional fullerene-type materials (ie, roundish cages), and so they have rather different properties. Most of the current research centers on nanotubes that have metal atoms incorporated into the carbon structure.

These metal-carbon tubes have some really cool properties, such as switching from insulating to metallic depending on the exact shape of the cylindrical region. You don't have to roll the tubes "straight," such that the carbon chains make circles around the cylindrical surface. You can roll them with a twist so the carbons spiral up the cylinder-- looking something like like twisted bread sticks. As you twist one additional unit at a time, the tube alternates between metallic and insulating.

There is also the hope that we will be able to put a string of metal atoms down the center of the cylindrical carbon cage. Such a structure is called a "nanowire," and is surely the world's smallest BNC cable. These wires are incredibly strong-- if they could be made as thick as a steel cable, they would be able to bear hundreds of times as much weight as steel.

Although, as noted on the page called What Are These Things Good For?, the regular fullerenes will probably not turn out to have economical practical applications, research into fullerenes has led to research into carbon nanotubes, which may in fact be practical.

In January 2002, Carbon Nanotechnologies, Inc. (founded by one of the winners of the Nobel Prize for the discovery of C60), licensed its laser-oven "buckytube" production process to DuPont. This hardly guarantees that anything practical will come from nanotubes, but it shows that interest is still keen among the big players. And the round fullerenes never reached a serious licensing stage like this. So stay tuned.

There is an excellent site created by the main nanotube researchers, called The Nanotube Site. Check it out to delve more deeply into these materials.

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Email: kimall (at symbol) mindspring.com