Nanotube Threads Get Stronger

pythorlh writes: "NewScientist has an article about carbon-nanotube thread. Could this be the begining of "monofilament" that sci-fi has been drooling over for years?" Well, from the sound of the article, not yet. But soon, perhaps: according to the article, "The new nanotube threads are about 10 times stronger than buckypaper, and can be tied into knots without breaking. But they are still much weaker than many other fibres, such as iron thread."

Comments

Potential?

[addaon]

How much potential do these threads have? We've all been dreaming of space elevators since Clark suggested the idea. Does any of the more recent research suggest that the currently-weak threads can ever be developed to such a point that a space elevator would be possible?

Re:Potential?

[Tofof]

The other use could be space tethers. This goal is probably sooner in the future, though the first test (Feb 25, '96) failed a few years ago. That test, though was designed to generate electricity - the tether had a copper braid around a simple nylon string, and was encased in kevlar. That one failed because air was trapped in the nylon, and the 3500 volts being generated changed the air to plasma (similar to a fluorescent tube lighting up) which subsequently melted the tether. This material would likely be far, far superior to the nylon.

Re:Potential?

[NanoProf]

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.

Now if one wants to make a space elevator, one's material has to also be resistant to radiation damage, etc. I think a back of the envelope estimate shows carbon nanotubes or diamond nanowires as being in the right ballpark, so long as one allows the structure to taper, but once one factors in the necessary engineering margins and the need to be resistant to damage over long periods (don't want it to fall apart in a year or two :-) it's much less clear if it's really possible. It's all in the very very long run, of course.

I should admit- I have not yet read this specific article (New Scientist website is crashing on me) so I can't comment specifically on this current experimental result. My guess is they did a larger-scale version of Lieber's experiment and found that the resulting thread was alot weaker (not surpirising- their structure likely has lots more defects and possibly single tubes don't extend throughout the entire length- they overlap).

Re:Potential?

[ErikZ]

Clark? I heard it first in
http://www.amazon.com/exec/obidos/ASIN/039482472 5/ref=sim_books/103-3932858-0304665

Called them skyhooks...

Later
Erik Z

Uses

[Christ-0-Geek]

The uses of such material seem really quite incredible. Just think - outside the field of computing, these things could be used to reenforce bone material, or muscle tissue.

It seems that these might actually have a use, unlike the buckyballs mentioned, which don't seem to be doing much of, well, anything (or, am I wrong? If anyone has info on actual uses of C60, please enlighten me).

My estimate is that nanoscience will become actually useful and commonplace within 13 years... I hope :)


-CoG

"And with HIS stripes we are healed"

Monofilaments in Warhammer 40K

[SuuSt]

We're one step closer to having that oh-so-nasty monofilament gun one of the Harelquins had in Warhammer 40K.

It shot out a spinning web of monofilament fibers that would turn its target into, as the book put in, something the approximate consistency of soup.

high fashion

[Juliet]

is this where high fashion, technology, and practicality meet?!

i have a feeling new strong high tech fibers will be used for safety, practicality and bondage.. before they start making dresses using it..

Re:high fashion

[Mignon]

new strong high tech fibers will be used for safety, practicality and bondage

This sounds like just the material I need to keep my Buckyballs safe and warm!

TSS-1r results aren't what you claim

[Tau Zero]

Trapped air wouldn't have affected the insulating value (there is at least as much trapped air in nylon used dirtside). Instead the problem appears to have been some kind of puncture or porosity. Here is the press release on the report issued on the tether-break analysis. The most important paragraph:

The board found sufficient evidence to identify two possible causes of the breach in the insulation -- foreign object damage, or a defect in the tether itself. Debris and contamination found in the deployer mechanisms and in the tether itself could have been pushed into the insulation layer while the tether was still wound on its reel. The investigation found evidence of damage to copper wire in the tether, and also established that normal forces on the tether while on the reel could push a single copper strand or foreign debris through the insulation.

NASA's not that hard to search, you should go consult it more often.
--

Re:TSS-1r results aren't what you claim

[Tofof]

Also on Nasa's page will you find this article, written in 1999 rather than 1996, which is from where I took my information.

The culprit turned out to be the innermost core, made of a porous material which, during its manufacture, trapped many bubbles of air, at atmospheric pressure. Later vacuum-chamber experiments suggested that the unwinding of the reel uncovered pinholes in the insulation. That in itself would not have caused a major problem, because the ionosphere around the tether, under normal circumstance, was too rarefied to divert much of the current. However, the air trapped in the insulation changed that. As it bubbled out of the pinholes, the high voltage ("electric pressure") of the nearby tether, about 3500 volts, converted it into a plasma (in a way similar to the ignition of a fluorescent tube), a relatively dense one and therefore a much better conductor of electricity. The instruments aboard the tether satelite showed that this plasma diverted through the pinhole about 1 ampere, a current comparable to that of a 100-watt bulb (but at 3500 volts!), to the metal of the shuttle and from there to the ionospheric return circuit. That current was enough to melt the cable.

Remember, when it comes to science, the first conclusion drawn after the fact is not always the best.

What's the alternative?

[2nd Post!]

What does this *research* offer us, you mean?

What was the point in researching electricity, 200 years ago? Nothing useful was built of it... for almost 200 years.

Yet if that research were not done, we would not have, in the intervening years, radio, speakers, solenoids, TVs, CPUs, etc.

So what will we have from C60 and buckyball research? No one knows... and that's all that can be said.

Do you want speculation? How about a different class of material? In one state superconducting, in another insulative, and in another, conducting? Different strength and material properties, maybe? How about a new class of allows using C60 instead of straight carbon? Or new optical devices using crystals doped with C60? It's sci fi, for now.

The nick is a joke! Really!

Re:monofilament in SF books

[AltGrendel]

I think Larry Niven wins that one, he mentions them in his universe early on, before his "Ringworld" book(s).

Re:Buckballs..... when?

[NanoProf]

Buckyballs don't have any important current application that I know of (there was some work in nonlinear optical materials, but I don't know if it panned out).

Carbon nanotubes have a pretty good chance of appearing as field emitters in flat-panel displays before too long. They have great conductivity, they're very pointy and extremely robust under the relevant electrical conditions. They are already at the simple prototype stage. Batteries might also pan out (they store lithium quite well) but tubes are still much too expensive for that.

The tubes will very likely find many more commercial applications than buckyballs.

Oh- and there's one application out there right now. Mass-produced (and very low-quality) multiwalled tubes are currently sold to mix into plastic parts to add conductivity to the plastic so that they can be charged up uniformly and electrostatically painted. Nice shiny plastic car bumpers. Not quite an elevator to geosynchronous, but it makes (a little) money.

Re:/. SysAdmins meet Mister Wizard

[NanoProf]

Hi,

I am a slashdotter myself occasionally. I am also currently performing research on nanotubes at a major research unversity, with publications in Science, Nature, and other places on nanoscience.

Perhaps the slashdot readership is a bit more diverse than you though. I find it an interesting place to visit, with some very intelligent conversation. (And thanks much to the moderators).

Re:Buckballs..... when?

[nomadic]

Might have actually been Buckminster Fuller himself. I know he didn't expect his inventions to come into use right away, but had a timeline which was often decades long before he expected them to be used.
--

Nanotubes

[Life Blood]

Just a few problems with these nanotubes.

1) Assuming perfectly defect free nanotubes above the single fiber level is implausible. Nanotubes work fine as single fibers, however stringing them together requires either using them in some sort of fiber composite or somehow connecting the tubes together to form some sort of tube honeycomb. A honeycomb cannot be assume to be defect free so properties will be degraded and a composite will weight the fiber properties with the weaker but tougher matrix.

2) Nanotubes will likely be quite brittle no matter what form they take. This poses big problems. The usual method for overcoming this is by compositing them with a weaker but tougher matrix, but that will lower the end strength of the composite.

3) Construction of tall buildings and the like requires big compressive loads. Tube/fiber composites suck in compression because the fibers buckle before they ever even get close to their ultimate strength. This is a problem if you wish to build a space elevator since such a structure is bound to have huge compressive loads at its base.

Re:If...

[WolfWithoutAClause]

To be honest, if someone's got a suitcase nuke, I'd prefer them to take out a tether than use it on the earth!

The cable wouldn't wrap around the earth- it would burn up as it re-enters. You wouldn't want to be in the few hundred miles east of the cable, but other than that its not a problem that can't be dealt with.

So the idea is that the cable would be built on an east coast and other design features would ensure cable wouldn't reach the earths surface after a catastrophic failure.