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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.
It seems like apples to oranges when they compare its strength to steel. Steel can be easily formed into large solid structures. Their measurement of nanotube strength is just for a single microscopic strand. You'd have to somehow combine the strands to form a useful macroscopic structure. And the strentgh of that structure would be more dependent on how the strands are connected.
Software sucks. Open Source sucks less.
It seems my chances of living to ride the space elevator have just increased.
:-)
AFAIK the space elevator requires a material roughly 30 times stronger than steel. True, these guys are "only" five times stronger, which leaves just another factor of five (ok, six) to reach the required strength. So in a way we are about half-way there
I'm not clear about the cost of their material, though. Anyone have an idea of how hard is it to create enough nano-tubes raw material to feed their process?
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.
This fiber is not measured for a single nano-tube. What they do is taking a gelatine-like glue with tubes dispersed in it and extrude it and bake it. The tubes are aligned and glued together in the process. So this is the real, macroscopic parameter.
By the way, from the simple chemicals named as a starting material, it seems like they got a good shot at producing this cheaply. You know, until now the nanotubes were pretty expensive. (More than gold by weight)
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
Unfortunately it's only strong in tension. If you have ever worked with carbon fiber, it's REALLY easy to cut, sideways. Think of it like a really strong, really thin nylon string.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
A random noodle arrangement like you see in fiberglass might work, but you loose a lot of your flexibility.
"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.
Not really. It's only strong in one direction, and even then, only in tension.
the same is true of the kevlar and spectra fibres commonly used in bulletproof vests today.
Everything should be made as simple as possible, but not simpler. -- A.E.
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.