Nanotubes show superplasticity

Carbon nanotubes can become extraordinarily plastic at high temperatures, a study published in Nature says.

Carbon nanotubes, the microscopic hollow fibres that are billed as the next revolutionary material, can become extraordinarily plastic at high temperatures, a study published on Thursday in

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Nature

, the British science weekly, says.

Nanotubes have until now been thought as being tough, thanks to their carbon lattice structure, but also rigid.

But Boston College physicist Jianyu Huang and colleagues heated some single-walled nanotubes to 2,000 Celsius (3,632 Fahrenheit) and found that the tubes suddenly started to behave more like a plastic.

In one case, a tube that was 24 nanometres (24 billionths of a metre) stretched to 91nm before finally breaking. In the process, its diameter slimmed from 12nm to just 0.8nm.

At normal temperatures, nanotubes may break after stretching to only 15 percent of their original size.

The discovery that this substance may have properties of "superplasticity" could interest engineers looking for ways to strengthen ceramics that operate in high-temperature environments, the authors say.

Carbon nanotubes, discovered in 1991 by Japanese electron microscopist Sumio Iijima, are hollow, cylindrical, hexagonal threads made of a web of carbon atoms that are many thousands of times narrower than the human hair.

They are created by vaporising graphite rods by electric arc in a chamber filled with a gas such as helium or hydrogen, and then allowed to cool slowly.

Stronger than steel but conductive and stable, the material has many potential outlets in nanoscale robotics, consumer electronics, computing, medicine and the environment.