PROVIDENCE, R.I. [Brown University] A pipefitter knows how to make an exact cut on a metal rod. But it's far harder to imagine getting a precise cut on a carbon nanotube, with a diameter 1/50,000th the thickness of a human hair.
In a paper published this month in the British journal Proceedings of the Royal Society A, researchers at Brown University and in Korea document for the first time how single-walled carbon nanotubes are cut, a finding that could lead to producing more precise, higher-quality nanotubes. Such manufacturing improvements likely would make the nanotubes more attractive for use in automotive, biomedicine, electronics, energy, optics and many other fields.
"We can now design the cutting rate and the diameters we want to cut," said Kyung-Suk Kim, professor of engineering in the School of Engineering at Brown and the corresponding author on the paper.
The basics of carbon nanotube manufacturing are known. Single-atom thin graphene sheets are immersed in solution (usually water), causing them to look like a plate of tangled spaghetti. The jumbled bundle of nanotubes is then blasted by high-intensity sound waves that create cavities (or partial vacuums) in the solution. The bubbles that arise from these cavities expand and collapse so violently that the heat in each bubble's core can reach more than 5,000 degrees Kelvin, close to the temperature on the surface of the sun. Meanwhile, each bubble compresses at an acceleration 100 billion times greater than gravity. Considering the terrific energy involved, it's hardly surprising that the tubes come out at random lengths. Technicians use sieves to get tubes of the desired length. The technique is inexact partly because no one was sure what caused the tubes to fracture.
Materials scientists initially thought the super-hot temperatures caused the nanotubes to tear. A group of German researchers proposed that it was the sonic boomlets caused by collapsing bu
|Contact: Richard Lewis|