Can you believe that carbon nanotubes can resist to pressures as high as 40 gigapascals -- or about a tenth of the one at the center of the Earth? When this limit is reached, they collapse. But before breaking, they propagate this pressure to whatever has been put inside them, squeezing nanowires for example. This could become another tool to manipulate structures at the nanoscale. In fact, these nanotubes could one day be used as metalworking tools, acting like nanoscale jigs or extruders. Read more...
Here are some excerpts from a Rensselaer Polytechnic Institute news release, which has collaborated with the Johannes Gutenberg University in Mainz, Germany, the Institute for Scientific and Technological Research (IPICyT) of San Luis Potosi, Mexico and the University of Helsinki in Finland.
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, according to an international team of scientists. The researchers suggest that carbon nanotubes can act as minuscule metalworking tools, offering the ability to process materials as in a nanoscale jig or extruder.
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.
Let's look at some of the results obtained by the researchers. On the picture below, you can see an iron carbide wire thinning and moving through the nanotube as it collapses (Credit: Florian Banhart, Johannes Gutenberg University, Germany).
And on this one, the nanotube finally collapses, pinching off the nanowire (Credit: Florian Banhart, Johannes Gutenberg University, Germany).
Now, here is a short overview of the experimental conditions.
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.
These jigs could be perfect nanoscale laboratories to study the effects of deformation in nanostructures by observing them directly in an electron microscope, the authors suggest.
This research work has been published by the journal Science under the title "Carbon Nanotubes as High-Pressure Cylinders and Nanoextruders" (Vol. 312, No. 5777, pages 1199 - 1202). Here are two links to the abstract and to more figures.
Finally, you might want to read another article on this subject published by Science News Online, "Gripping Tale: Metal oozes in nanotubes' grasp" (by Peter Weiss, May 27, 2006).
Sources: Rensselaer Polytechnic Institute, May 25, 2006; and InvenSense web site
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