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President's View Mail Class Notes Features
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* Nanotechnology

Controlling Nano Shapes

Rensselaer researchers have discovered a simple method for rapidly creating different shapes of carbon nanotube structures. To produce the minuscule structures on a commercial scale, manufacturers are looking for such techniques that make it possible to work with materials several billionths of a meter in size.

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The findings appeared in the March 23 issue of Proceedings of the National Academy of Sciences.

Since their discovery in 1991, carbon nanotubes have tantalized researchers because of their exceptional combination of size, strength, and physical properties. Their tiny dimensions raise hopes for a new generation of semiconductors and a host of other applications in medicine and materials science. But researchers must first develop techniques that allow for the commercial manufacture of precise structures.

The new method to control the shaping process is based on a commonly used chemical vapor deposition method. Researchers grow a carpetlike film of multiwalled nanotubes on a specially patterned silica base and bake it at 800 degrees centigrade. Then the nanotube film is oxidized and immersed in liquid. As the liquid evaporates, the nanotubes cling together and form predictable shapes based on the patterns of the underlying silica base. Once assembled, the resulting foamlike structures are stable and elastic.

“This method can be used to make stable nanotube foams that can be twisted, transferred to other substrates, or floated out to form free-standing macroscopic fabrics,” says Pulickel Ajayan, professor of materials science and engineering. “The assembly process provides a simple and rapid technique for fabricating nanocomposites, with great control over the length, orientation, and shape of the cellular structures,” Ajayan says.

“The resulting lightweight cellular foams made of condensed nanotubes could have applications as shock-absorbent structural reinforcements and elastic membranes,” says Ravi Kane, the Merck Assistant Professor of Chemical and Biological Engineering.

The foams could be used in a variety of applications, including new microchips and wherever strength and flexibility are needed, from repairing bone joints to reinforcing carbon-fiber-based aerospace products.
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Rensselaer Magazine: Summer 2004
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