Posted: December 18, 2008 |
It's huge - but is it still a carbon nanotube? |
(Nanowerk News) A carbon nanotube of micrometer dimensions offers the same conceptual challenge as does a jumbo shrimp: How can something so small become large, yet remain in its category?
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A relatively huge, lightweight carbon tube with good strength and electrical properties is desirable, all right, because it can be manipulated in the far more accessible micrometer regime.
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But is it still a nanotube?
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Jianyu Huang at the Sandia/Los Alamos Center for Integrated Nanotechnologies (CINT), and colleagues elsewhere, got around this problem by naming their new creation “colossal carbon tubes” in a paper published in an October issue of Physical Review Letters.
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“The structures are remarkable because they are very light, possess good electrical conductivity, and have mechanical properties similar to carbon fibers,” Jianyu says.
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Among possible uses are so-called textile electronics and body armor.
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Because of their strange, surprising sponginess — walls of graphite-like carbon kept apart by hollow, rectangular compartments — the colossal fibrous tubes have a density of 0.1 gram, compared with 2 grams for the comparable amount of carbon fibers.
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The colossal tubes are about the same length as carbon fibers — in the centimeter range. And they appear to be slightly stronger — a very desirable, and until now unheard of, property in large carbon tubes.
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MIT carbon technology specialist Mildred Dresselhaus was quoted in an online news column of the journal Nature: “This is a new form of carbon that was unexpected to me.”
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Jianyu, who did the microstructure analysis that confirmed that the walls of such tubes consist of graphitic structure, describes the new creation as “a porous, giant, carbon fiber-like tubular structure” of diameters ranging from 40 to 100 micrometers. Conventional carbon nanotubes are about 10 nanometers in diameter.
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The material was made at Los Alamos National Laboratory. Researchers there led by Yuntian Zhu and Huisheng Peng found that heating ethylene and paraffin oil produced a carbon vapor that condensed into tubes of pure carbon tens of micrometers wide and up to several centimeters long.
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