Nanotubes Start to Show their Promise

Rei writes "Researchers at the University of Texas at Dallas have developed the highest quality nanotube sheets to date (the team previously set strength records with polymer-nanotube composites). Producable at a rate comparable to commercial wool spinning, the transparent cloth has exceedingly high conductivity, flexibility, has huge surface area to volume ratios, can potentially be made into very effective OLEDs and thin-film photovoltaic cells, and outperforms even our best bulk materials (such as Mylar and Kevlar) at strength normalized to weight. It strongly absorbs microwaves for localized heating (leading to applications in seamless microwave welding of sections and even windshield warming), changes conductivity little over a wide temperature range (very useful in sensors), and is expected to be used in commercial applications very soon. The research should even be expandable to artificial muscles! To head people off, while the exact tensile strength is not listed, it sounds like it is still far from the >100 GPa needed for a space elevator. Anyways, here's to process advancements!"

Comments

Producable at a rate...

[ArbiterOne]

Yes, it's producable at a certain rate- but what about the cost? Is it economically feasible?
Unfortunate about the space elevator. Looks like the highest we've gone is 63 GPa (http://en.wikipedia.org/wiki/Tensile_strength)

Re:Cost is irrelevant

[SimilarityEngine]

According to this article, Andrew Barron (Rice University) seems to think we could see this technology used in Formula One racing cars, as early as next season. Although he's probably being a little optimistic, something like a Formula One team would certainly have the sponsors to experiment with tech like this, and develop cheaper manufacturing processes (if possible).

Why they are weaker

[convex_mirror]

The reason why nanotube composites don't end up being nearly as strong as nanotubes is that nanotubes are very slippery inside of a composite, so once force is applied, it doesn't transfer through the interface and the ultimate tensile strength is primarily determined by the composite.

In this case, when they are weaving fibers together, the weakness in tensile strength will come from the interface between linked nanotubes which will have a tensile strength many orders of magnitude than that of an individual tube.

Sheet tensile strength

[The Evil Dwarf from]

According to the Science article(subscription required) abstract a stack of 18 sheets had a strength of 465MPa/(g/cm^3) (high strength steel listed as 125 MPa/(g/cm^3)).

They also built an OLED of 500 cd/m^2 with a onset voltage of 2.4V.

Re:But will it slice bread?

[fearofcarpet]

I'm no chemist or engineer, I don't know what potential carbon nanotubes have or don't have but whenever I read an article that seems to promise everything, I figure it is about 95% hyperbole and wishful thinking.

I am a chemist, I work in the "nanotechnology" field, and I have spent time in Engineering/MS labs making OLEDs, PV cells, and other thin film devices. Many of "us" consider nanotubes to be the only viable "nanotechnology" at the moment because of the fact that they can be used by spraying thin layers, making entangled sheets, or other easy-to-commercialize methods of preparation. As for the hybperbole, I think the fact that you're reading an article on MSNBC should give you a clue : ) If you read the Science article they make essentially none of the claims present in the MSNBC article. In fact all they really claim is a new method for preparing NT sheets that is way better than the current methods used for preparing NT 'paper' (it really looks and feels like paper).

Yes, nanotubes are cool. Yes, they conduct electricity. Yes, they emit white light in an OLED configuration. I'm not 100% sure where they're getting the artificial muscle thing, but from what I've read (from peer reviewed journals) don't hold your breath - but I'm no expert there. What generally happens here is the inventors like to hype their discovery up (in this case a method for preparing better NT sheets) as much as possible, but in "science speak". That is, this "may be used for ___" or "has the potential for ___" and then they rattle off stuff NTs can be used for which gets all mixed up in the in article. In this case NT sheets are nothing new and most of what they're claiming has been done before (IBM even got light out of a single NT, far more impressive if you ask me), but they're doing it better with higher quality NT sheets. When it was discovered that poly(aniline) had great mechanical properties as well as interesting "chemical switching" and conductive properties there were people that were sure it was going to be used in planes, clothes, computers... You name it. Too bad it is deliquescent - D'Oh. I can't remember whether this happened before or after the discovery that poly(acetylene) had a high tensile strength and people were claiming space elevators, lightweight electric motors, etc etc. Too bad it catches fire in air in its conductive form - D'Oh D'Oh.

At the end of the day this is another step towards some real nanotechnology applications, but you're reading about it because the editors at Science decided it was worth publishing. Only in the Science article they include all the references to the past work that made it possible :) Oh, and the microwave thing is neat because the NTs will spark like crazy in your microwave oven. So will graphite, which you can try at home if you like... If you don't know NTs are essentially "rolled up" graphite sheets, so they share a lot of common properties.

Here is the abstract:

Individual carbon nanotubes are like minute bits of string, and many trillions of these invisible strings must be assembled to make useful macroscopic articles. We demonstrated such assembly at rates above 7 meters per minute by cooperatively rotating carbon nanotubes in vertically oriented nanotube arrays (forests) and made 5-centimeter-wide, meter-long transparent sheets. These self-supporting nanotube sheets are initially formed as a highly anisotropic electronically conducting aerogel that can be densified into strong sheets that are as thin as 50 nanometers. The measured gravimetric strength of orthogonally oriented sheet arrays exceeds that of sheets of high-strength steel. These nanotube sheets have been used in laboratory demonstrations for the microwave bonding of plastics and for making transparent, highly elastomeric electrodes; planar sources of polarized broad-band radiation; conducting appliqués; and flexible organic light-emitting diodes.

So what they did was create sheets