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Texas Scientists Spin Carbon Nanotube Fiber
RedCard writes "According to this article at news24.com, University of Texas scientists have managed to spin a fiber made of 60% carbon nanotubes that is five times stronger than steel and is "tougher than any natural or synthetic fibre described so far" - including spider silk! Previous attempts at making fibers like this have only produced relatively short lengths, but these guys have produced lengths of 100 metres at the rate of 70cm per minute!"
One can estimate theoretically the ultimate strength of a nanotube be examining the microscopic failure modes, i.e. the ways in which atoms rearrange in response to an external stress (i.e. stretching). In the case of perfect, defect-free nanotubes, there are two modes that seem to be important. First, the rotation of a single carbon-carbon bond by 90 degrees, which converts a patch of 4 hexagons (remember that carbon atoms are arranged in a chicken-wire or honeycomb pattern on the tube wall) into two pentagons and two heptagons (relevant references are Zhang & Crespi from Penn State in Physical Review Letters and work by Bernholc at NC State and Yacobson at Rice I think, but the exact journal escapes me at the moment). This mode is a plastic distortion of the tube; the tube with the bonds rearranged is a bit longer than it was before. The second failure mode is for one of the hexagonal rings of carbon atoms to break open, i.e. for a carbon-carbon bond to break. This is a more catastrophic event, in that the tube then quickly breaks near the point of failure. Which way a tube fails may actually depend on how the honeycomb pattern is rolled into a tube shape. Now that's just the microscopic theory on the ideal, defect-free system. In a real tube, one expects there to be pre-existing defects in the structure. The failure under tension will then be at the defective points But, since nanotubes are so small, it's plausible that a single tube or bunch of tubes might grow entirely defect-free, in which case one can access the ultimate theoretical failure strength. Experiments on trying to stretch and break single bundles of nanotubes (Lieber's group at Harvard) show that one can extend a nanotube by about 6% of it's length before it breaks. This is in good agreement with the theoretical predictions mentioned above (and it's a legit prediction- the theory came first!). So it appears that in small enough systems, one can attain the theoretical mechanical strength.
Kudos to you, my good man.
I seem to recall that a bright source of light can make carbon nanotubes burn up like ignited magnesium.
Yea, I'd be the first to wear or use this fabric.. "Smile for the camera!"
"No, wait!" *clic-FLASH* "AAAARGH THE HUMANITY!"
"Could this stuff, if produced cheaply enough in the next 20 years, be the end-all of condoms?"
Yeah because Slashdotters are all in immediate danger of unwanted pregnancies.
The effect only works with single walled carbon nanotubes, and even then only when in air. The effect actually happens because the tubes are very black and very porus, absorbing a large amount of light and rapidly converting it to a violent expansion of the surrounding Oxygen in the air igniting the nanotube. This will never occur if the tubes are incorporated into an epoxy string.
- "Hear that?! The percolations are imminent! Cease your ingress!"
I agree with the spirit of your post, however one should note that, in the article, they are only comparing tensile strengths. Steel also has a very high compressive strength which makes it useful for all kinds of structural members. It's unclear whether the nanotubes would be useful for situations where they're being pushed, bent or subjected to shear stress. Perhaps somebody else can shed some light on this.
This is definately good news, but it is only about 1/6th the strength needed for the elevator. At 5 times the tensile strength of steel (4.2GPa) it matches the strength of graphite whiskers (21GPa).
The elevator becomes feasible at around 130GPa, so there is a little ways to go yet. It is only a matter of time now.
FWIW, the theoretical limit of CNTsis thought to be around 300GPa.
Who cares about space elevator: But if it is *five times* stronger than steel, it must be also better than Immodium.
[Use with meal, do not exceed 120 meter recommended daily dose. Spiderman is a copyrighted work of art, ingesting Carbonfibre for this purpose without authorisation of Warner Bros is prohibited.]
I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
And if you think Mr. Willy is going to be sore, just imagine what the Mrs.'s naughty bits are going to be subjected to.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Again though, it's only good in tension. You do open up more applications though: a high-strength hammock, or a slash-resistant fabric, a drum-head, a high-strength net. Using the same techniques they use for kevlar, bullet-resistant materials.
I'm also envisioning it's use in large pnumatic dome structures, where the strength of the structure IS in the tension of the walls.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Highlift did not go down the toilet. They existed to be an entity to receive money from NASA for the NIAC Phase 1 and Phase 2 grants. Those phases are over, and therefore Highlift has no reason to exist (it wasn't really a 'company' per se).
Contrary to what Slashdot has said, LiftPort (www.liftport.com/www.liftport.org) is not a competitor to Highlift - it was simply the natural next step (in Michael Laine's opinion - Brad Edwards thought that the time wasn't right for a public push yet) of moving from a government-funded research lab to a privately-funded company.
Incidentally, if you haven't been to www.liftport.com recently, they overhauled their website (it looks very good now) and are in an investment phase - they've already received over $1M in funding (not bad!). The "public" end, akin to Highlift, is going to be at www.liftport.org.
"Requires" is a slippery word, because to some extent you can make up for a weaker material by tapering the cable so it's thicker in the middle where it's holding the "weight" of both ends, and thinner at the ends so there's less load.
The amount of taper gets absurd in no time for materials weaker than unobtainium. High Lift Systems quotes a taper ratio of 1.7E33 for steel and 2.6E8 for Kevlar, and that's apparently for a cable stressed to the breaking point.
10 or 20 times stronger than steel would be usable, in other words.
That's a very interesting thought, and worth expanding upon for anyone not familiar with the state of the art, or possibly unfamiliar with cars in general.
At first I was tempted to dismiss your statement because carbon fiber cloth is easy to get, is relatively cheap (it's the autoclave that makes it so expensive to use/make), is well understood, and works very well -- and has been in widespread use for exotic automotive applications for about a decade. A friend of mine recently had a minor crash in his F50, as an example, and the repairs involved $150,000 worth of new carbon fiber -- 8 layers for most body panels, with each layer being completely different than the others, with each layer put there for specific reasons. Some are straight weaves, some are cross-weaves, and some are honeycombs -- all in a car that is 8 years old. So carbon fiber in general is definitely well-understood.
However, in thinking about the properties of this specific application, I realized you might be on to something. Where this new strand-format CF might be interesting is places where steel tension cables are used today -- shifter cables, parking brake cables, wing adjustments, support structures, and so on. After all, in certain circles, any weight reduction is worth the money. I would expect to see it first in Formula-1 -- assuming the newly tech-averse rule-making idiots at the FIA don't make carbon fiber illegal, too.
Definitely an interesting thought.
Slashdot quality declines as the number of hot grits posts decreases. - Provolt's Law, Apr-09-2005
whoa...
On the other hand, Liftport has raised a million bucks in half the time they expected, and the gonzo attitude appeals to my Heinlein-educated sensibilities. I sent them a few hundred bucks yesterday, just in case.