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Researchers Explore Nanotubes as Minuscule Metalworking Tools

When a beam of electrons hits a carbon nanotube, some carbon atoms are knocked away, causing the remaining atoms to contract and the tube to shrink. Photo by Zina Deretsky/NSF

An international team of scientists, including Pulickel Ajayan, the Henry Burlage Professor of Materials Science and Engineering at Rensselaer, revealed that bombarding a carbon nanotube with electrons causes it to collapse with such incredible force that it can squeeze out even the hardest of materials, much like a tube of toothpaste. The researchers suggest that the carbon nanotubes can act as minuscule metalworking tools, offering the ability to process materials as in a nanoscale jig or extruder.

Engineers use a variety of tools to manipulate and process metals. For example, handy “jigs” control the motion of tools, and extruders push or draw materials through molds to create long objects of a fixed diameter. The researchers’ findings suggest that nanotubes could perform similar functions at the scale of atoms and molecules.

The results also demonstrate the impressive strength of carbon nanotubes against internal pressure, which could make them ideal structures for nanoscale hydraulics and cylinders. In the experiments, nanotubes withstood pressures as high as 40 gigapascals, just an order of magnitude below the roughly 350 gigapascals of pressure at the center of the Earth.

“Researchers will need a wide range of tools to manipulate structures at the nanoscale, and this could be one of them,” says Ajayan. “For the time being our work is focused at the level of basic research, but certainly this could be part of the nanotechnology tool set in the future.”

Carbon nanotubes have been hailed as some of the lightest, strongest materials ever made, and they are beginning to find use in a wide variety of materials. Yet while many of their distinctive properties have been studied in detail, the strength of carbon nanotubes against large internal pressures has yet to be fully explored, according to the researchers.

The researchers filled carbon nanotubes with nanowires made from two extremely hard materials: iron and iron carbide. When irradiated with an electron beam, the collapsing nanotubes squeezed the materials through the hollow core along the tube axis, as in an extrusion process. In one test, the diameter of iron carbide wire decreased from 9 nanometers to 2 nanometers as it moved through the tube, only to be pinched off when the nanotube finally collapsed.

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