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Nanotube yarn sweater? Made in China to stop speeding bullets

Scientists in China have developed a strong, highly conductive carbon yarn that could be used to make spacesuits, bullet-proof vests, and radiation suits.

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Tiny carbon nanotube fibers can conduct electricity, and be 100 times stronger than steel at one-sixth the weight.

Kai Liu courtsey of TechNews Daily

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Super-strong, highly conductive yarns made from extraordinarily thin carbon tubes could one day find use in spacesuits, bulletproof vests and radiation suits, researchers now suggest.

Carbon nanotubes are hollow pipes just nanometers or billionths of a meter in diameter — dozens to hundreds of times thinner than a wavelength of visible light. They can possess a range of extraordinary physical and electrical properties, such as being roughly 100 times stronger than steel at one-sixth the weight.

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Scientists have feverishly explored ways to make textiles from carbon nanotubes for years. However, yarns made from these nanotubes lacked the attractive properties seen in lone fibers. The problem is rooted in how the nanotubes are typically about 200 to 400 millimeters long.

When these get woven together into a yarn, the connections between the nanotubes act as gaps that weaken the yarn's overall conductivity, and these connections are not as strong as the tubes themselves, explained researcher Kai Liu at the Tsinghua-Foxconn Nanotechnology Research Center in Beijing.

Simultaneously enhancing both the strength and conductivity of yarns made from these nanotubes has proven difficult. Additives that increased the strength of these yarns often inadvertently left behind poorly conductive residues that reduced the overall conductivity of the yarn. On the other hand, treatments with super-acids that boosted the conductivity of these yarns by adding oxygen-containing molecules also weakened the yarns by introducing physical defects.

Now scientists in China reveal they have made composite yarns from carbon nanotubes and plastic that are both very strong and electrically conductive.

The researchers first wove pure carbon nanotube yarns as free of physical defects as possible, to ensure it had good electrical conductivity. They next impregnated a strengthening plastic into the empty spaces inside this yarn, using a solvent that did not leave any leftovers behind that would detract from the yarn's electrical properties.

The strength of these new yarns — up to about five times stronger than steel — combined with their flexibility makes them attractive for protective fabrics such as bulletproof vests. At the same time, the fact they are so electrically conductive means they could be easily heated, making them valuable for use in super-cold environments such as outer space. In addition, since carbon nanotubes can absorb a wide range of electromagnetic waves, "this kind of woven fabric is also expected to be used in radiation protection suits," Liu told TechNewsDaily.

Future yarns could have more potential applications, "especially in biology and medicine," Liu added.

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The scientists detailed their findings online September 10 in the journal ACS Nano.