Credit: Science/AAAS/UTD NanoTech Institute
Recently I wrote about Israeli-based TorTech, which says it will soon be manufacturing carbon nanotube fiber yarns that it claims to be stronger than Kevlar, yet still flexible and lightweight. While Tor-Tech plans to implement the technology for military use, spinning nano yarns has potential for many applications.
MIT’s Technology Review reported on research out of the University of Texas at Dallas, demonstrating a way to spin yarn out of nanotubes infused with nano powders. According to the article, the researchers have used the method to make strips of yarn that have a wide array of properties, allowing them to function in diverse applications, such as a battery electrodes, superconducting materials and self-cleaning yarns.
These fibers could solve a big practical problem: Powders without form are difficult to use, yet they are a very important component to functional materials because they have very high surface area. Sintering and binding are complicated processes typically used to give form to powder materials.
Ray Baughman, director of the MacDiarmid NanoTech Institute at the University of Texas at Dallas, says nano yarns should make it easier to work with a wide range of powdered materials. “You can take almost any powder and make a sewable, knittable, knotable, braidable yarn,” he tells Technology Review.
According to the article:
The researchers start by growing a forest of vertically aligned carbon nanotubes in a chemical reactor. Then they drag a roller over the nanotubes, which separate from the surface and get tangled up in a long, stretchy ribbon — a so-called nanotube web . . . The researchers spray the surface of the web with the powder and then twist it into a yarn. The powder is confined inside the spirals of the nanotube web. “When you wash it, almost all the powder is retained,” he says. The resulting yarns can be 95 to 99 percent powder by weight.
Baughman’s group used a mixture of powdered boron and magnesium to make superconducting yarns by a simple process. The conventional process for making superconducting wires involves packing the powders in copper tubes and heating and drawing them tens of times to stretch them into wires. But the superconducting yarns are heated just once to anneal the powders and form a superconducting thread.
Some applications in which Baughman has applied the technology includes battery-electrode fabric using lithium-iron-phosphate powders. Since the fabric is about 99 percent active material, he thinks it could be used to make less-heavy batteries. The yarns could also be used to produce material for structural manufacturing.
On the NanoTech Institute’s website, researchers note, “We have spun carbon nanotube composite fibers at a hundred times the prior-art rate, and obtained fibers that pound-per-pound have twice the strength and stiffness and 70 times the toughness of strong steel wire. In addition to other functionalities, we have used these fibers for both electrical energy transmission and sensor devices in electronic textiles.”
First, its important to find appropriate markets. “Right now it’s more sensible to talk about batteries, not airplane wings, because of the tonnage [of materials] required,” says Baughman.
The powers can be applied via spraying techniques or even using inject printing A video demonstrating titanium dioxide powder being sprayed onto a moving nanotube web can be viewed on MIT’s website here.