The World's Longest Carbon Nanotube 142
Roland Piquepaille writes "As you probably know, carbon nanotubes have very interesting mechanical, electrical and optical properties. The problem, currently, is that they're too small (relatively speaking) to be of much use. Now, researchers at the University of Cincinnati (UC) have developed a process to build extremely long aligned carbon nanotube arrays. They've been able to produce 18-mm-long carbon nanotubes which might be spun into nanofibers. Such electrically conductive fibers could one day replace copper wires. The researchers say their nanofibers could be used for applications such as nanomedicine, aerospace and electronics."
Wow (Score:5, Funny)
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Re:Wow (Score:5, Interesting)
Ted Stevens actually being prophetic, rather than just wrong.
You know, Stevens gets a totally bad rap on that whole thing. Exactly what is wrong with that analogy? Even UNIX uses the analogy with pipes; Ritchie* could have just easily called them tubes rather than pipes. And yes, the "tubes" of the Internet CAN get clogged up if there's too much flowing through them.
I've never understood why he took such a beating about it. I guess some people are just determined to believe the worst about people, as though the guy though the Internet was literally air-filled tubes.
Re:Wow (Score:5, Informative)
From wikipedia.
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The context it was said in, he did not say "The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP) [Wikipedia]... You can think of it as a series of tubes...".
Here's a clip [youtube.com] with interesting parts from his speech.
I'm also sure you can find the whole thing in the related clips pane. Listen to it (again?) and judge for yourself if he knows what he's
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Whatever happened to just calling them wires? I mean, like, DUUUH!
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that died when the wires became optical fibres.
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The analogy isn't too terrible. It conveys the notion that Internet bandwidth is a shared resource. However, Ted Stevens demonstrated very clearly that he has no idea what he's talking about. He seems to think that when somebody downloads a movie, the entire movie gets put into the 'tube' and all other data gets in line behind it. He thinks an e-mail he got several days after it was sent arrived late because too many movies were coming through the tubes. Not only that, but he referred to the e-mail as "an i
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I think its kinda dangerous to assume that he's stupid, because you fail to realize
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The proof of the analogy is in the reasoning. Senator Stevens, if you recall, was blaming net neutrality for the fact that his email sent by one of his staff on Friday morning didn't arrive in his inbox until the following Sunday morning.
So, yes, I think Senator Stevens deserves a round of jeers on this one. He's obviously bought a load of tosh about how net neutrality hurts users.
In any case, the correct analogy would be: "The Internet is a NETWORK of tubes."
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``Think the worst about people, and you'll usually be right.'' --Catbert.
My microtube is bigger than your nanotube (Score:4, Funny)
One nanotube: two birds (Score:5, Funny)
Voila! No more global warming!
8-)}
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Come again (Score:3, Funny)
Perhaps 18 mm stands for... 18 million miles?
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Re:Come again (Score:5, Informative)
That puts it in the area of useable length for macro-sized application.
Re:Come again (Score:4, Informative)
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If a weave of 10cm long fibres of some material is already failing by fibres breaking rather than fibres slipping, there's not much to be had from the fibres being instead 1 meter or 10 meter long individually.
I'm certain that 18mm long nanotubes are already long enough that a rope made of such would have 90%+ of t
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When a traditional fiber breaks, it's slipping on a molecular level. With macroscale nanotubes, the breakage would be right down at the covalent bond level, theoretically giving it a tensile strength on the same order as a perfect diamond. Admittedly, I don't know if that's any good or not.
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Strengths in the 60 - 100 GPa-range have been measured, which is fairly impressive when you consider that high-tensile steel tops out around 1.2 so basically, a carbon nanotube-rope of a given thickness should be able to hold 50-90 times the load that a similarily thick steel-cable can hold.
But it gets better; carbon nanotubes are (unlike steel) ligthweigth. Often, strength in relation to thic
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They conduct heat along their length *insanely* well.
If you take a square-meter of meter-thick copper and heat one side of the block so that it is 1 degree C (or K, same thing in this case) warmer than the other side, then 385W of power leaks through. A lot. Copper is a good thermal conductor. (as any overclocker would know.)
The same number for a block of tigthly compressed, perfe
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See... the bullet just bounced off... "balls of steel," I tell ya!
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Just to get some perspective on this, 18mm is about a third of the length of good quality wool fibres.
That puts it in the area of useable length for macro-sized application.
IIRC when Popular Mechanics discussed these nanotubes for building our space elevator, one of the technical hurdles they mentioned was needing nanotubes ~18" in length for the structure to be sound.
Obviously we've got a long ways to go then.
The other thing they mentioned was that given a mathematically perfect carbon nanotube structure, the highest building we could build before it would collapse on itself is something like 90 miles; and we need
Of course both of these are hearsay so take them with a grain
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Carbon nanotubes have their strength in tension, not compression.
A self-supporting building based on nanotubes would have to be a tensegrity structure of some kind, where you'd have nanotubes pulling against something else that's relatively incompressible; mayb
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What about a rope supported from the top.
Yes the figure that referenced as to how high we needed the carbon nanotubes to be able to support themselves structure wise was the number that was "several orders of magnitude" (~3 I seem to recall) higher than what the what the mathematically perfect nanotube structure could reach. That height that we needed the nanotubes to be able to reach structure wise was just as you say-- only far enough so that the rest of the tether could act as a counterbalance to the part of the tether closer to earth.
All in a
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Thats hardly something to sneeze about.
They are long enough to, for example, actually connect two macroscopic devices, for example two dies on a MCM.
Million times longer than they are wide (Score:2)
As Mork would say... (Score:3, Funny)
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That's na-NU, my man....
My understanding is that writers originally wrote the it as nano, and so in particular first season merchanise often used that spelling, but Robin Williams pronounced it as nanu.
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ZOMG BOYKOTT R0L4ND!1! (Score:5, Funny)
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Wee! (Score:1)
That's what she said (Score:3, Funny)
One more step toward a space elevator? (Score:3, Interesting)
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This isn't tomorrow's technology, it is something the human race might do a hundred years from now.
If we have the super strong, super light materials needed to make the space elevator, what else might we do with them? Might we not make better rockets? Or better planes? Might we not make single-stage-to-orbit vehicles which so drastically reduce the price of launch costs that building a space elevator is not only possible, but unnecessary?
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Re:One more step toward a space elevator? (Score:5, Interesting)
The problem with rockets has never been the mass of the rocket, but the mass of the fuel. There's only so much oomph you can get out of a million litres of hydrogen and oxygen chemically, and it's only marginally more than the power it takes to lift a million litres off the surface and into space. Sure, a lighter fuel tank, and lighter payload will help, but not significantly.
No, if we want cheap access to space, we either go nuclear [nuclearspace.com], or build some sort of space elevator. While we may just be at the threshold of being able to make materials with the tensile strength needed for a beanstalk, we have the tech to make gas core nuclear rockets right now.
Re:One more step toward a space elevator? (Score:5, Insightful)
It's not about the fuel prices. Never has been, and won't be for the foreseeable future. Propellant is cheap, it's the vehicle that's expensive. Elon Musk of SpaceX was recently quoted as saying propellant costs are comparable to the accounting errors.
Remember that the space elevator has to supply all the energy to the payload too, but it has to get it in a much more expensive form -- like electricity beamed from the ground by lasers or some such. Rockets aren't actually all that energy inefficient in comparison.
I used to be a huge fan of the space elevator idea, but then I started looking what those same materials do to rockets. SSTO is just the start. And remember, those materials will change rockets long before they make a space elevator.
Of course, I am a rocket engineer, so I might be a little biased, but I've also examined the problem in some detail :)
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Try to imagine how many launches you would need to, for example, build a mining and refining base on an asteroid. 25 million tons, in an escape orbit, anybody?
Thats a 1000 times of all launches in human history, for something that might be just a little thing if we ever go interplanetary.
Try a quick calculation of how it would cost...
You might be thinking in current terms "All we send up is highly tec
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I never really understood this bit. There you are with a highly conductive material that will conduct that same as graphite sheets in the high strength direction (which is straight up the wire) and people are talking about broadcast power? Even if it is well columnated not a lot of power is going to hit your
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Re:One more step toward a space elevator? (Score:4, Informative)
People don't seem to get this somehow. Yes, mass ratio matters. A lot. Let's look at LOX+Kerosene, a very typical combination in many ways. You get an ISP of about 3000 m/s in a medium-high performance vacuum engine (the case for most of the way to orbit). LEO takes about 9000 m/s of delta-v by the time you account for aerodynamic and gravity losses. That means the mass ratio of your rocket needs to be about e^(9000/3000) = e^3 = 20. So 5% of your rocket makes it to orbit. Yup, that sucks. LOX costs about $0.07/lb in bulk, kerosene about $0.30. So propellant costs are about $0.15/lb for propellant, or $3/lb of orbited mass.
Now lets look at the space elevator. Climbing to geosynchronous orbit is equivalent to about 8000 m/s of delta-v (roughly... don't have the exact number off hand and I don't feel like calculating it). From 1/2M*v^2, that's 32MJ/kg. That's about the energy you get from burning 6 kg of LOX-kerosene. So from an energy equivalence standpoint, you're using 6 kg of propellant worth of energy instead of 19 -- a factor of 3 improvement.
The problem with the space elevator is twofold. First, the required *form* of the energy is different. You can't just use cheap hydrocarbon fuels -- you have to convert it to electricity, and then get that electricity up to the elevator either by beaming it or along wires, and neither option is efficient in the slightest. In fact, by the time you turn the hydrocarbon fuel into electricity and then get it to the elevator car, you're under 50% efficient; being as high as 30% would take a lot of work and be quite impressive. But the rocket was 30% efficient! Space elevators are *not* particularly more efficient than rockets.
The second problem is the infrastructure of the space elevator -- the required capital investment for a certain payload rate (kg delivered per day) is higher than for the rocket (we won't even discuss non-reusable rockets). Even if you got the space elevator more energy-efficient than the rocket, this fact combined with the slower transit time, the geosynchronous orbit as the only one available, and the more complicated technological requirements, the rockets win.
Yes, the space elevator tech is harder. The ribbon itself and the beamed power are the obvious examples, but there are others. For example, the tires on the car that work against the ribbon -- you need tires that run at about Mach 3 and are good for 27000 miles. That's not even remotely easy. You need motors that have higher power to weight ratios than currently exist. Etc, etc, etc. Rockets, in comparison, are easy. Especially if you have space-elevator class building materials available -- at that point you can do SSTO with pressure fed rockets, and get rid of the pumps altogether -- the pumps being the hardest part of rocket engine development by far in a conventional design.
When people say that for space elevators you only have to provide the energy to climb up, and aren't wasting the energy carrying propellant, they often forget that it's actually a *lot* of energy to climb up, and that rockets are actually remarkably good at converting available chemical energy into exhaust kinetic energy -- some are better than 80% efficient by that metric.
Energy needed for climbing... (Score:2)
Can't you have a pulley system with two cars - one goes down when the other goes up. That would reduce energy costs to practically zero. All you need to do is fill the one at the top with atmospheric water and it would pull the other car up as it descends.
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Atmospheric water? What atmospheric water? You're out of the atmosphere...
This probably works better with a bunch of cars on the cable and wired power transmission; instead of space-elevator length *moving* cables you just need regenerative braking. It helps some, but most payloads probably stay up there, so you only recover the car energy, which is supposed to be a small fraction of the total. The passenger trade will run on rockets, the elevator is for things like satellites, propellant, and other b
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The whole thing is about economics. You want high speed for short transit times, obviously, but the important reason is to get the car off the bottom of the elevator. You need to do this because of the weight limit on your cable. Once the car is a ways up it counts less against the weight limit. This implies high speed tires, high power motors, and high power transmission rates. The reason I say Mach 3 is nothing magic, just that many elevator proponents talk about speeds around 1000 m/s.
Even if your
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To make a far more energy efficient design you need to run the cars at constant speed. You also need to attach each car together. That way you can use the energy of the cars on the way down to help power the cars on the way up, much more like how a real elevator works. This means that the whole system requires a much more constant energy input.
This also does away with the idea that each car ever stops. It presents a problem of how you load and
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In any case, that's not required. It's a long way (36000km) to geosynch, but gravity falls of very rapidly.
If we ignore the contributions of the centripetal force, then gravity scales with the square of the distance. When starting at equator you're about 6500km from the core of
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The elevator car isn't on the ground. You have to get power to it somehow. The basic options are solar generation on the car, beamed power (either laser or microwave... both have problems), or wires (which have resistance problems). So yes, you use ground based power -- the power isn't the problem, it's the power transmission.
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Do we have the tech to deal with the fallout of the inevitable accidents?
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we have the tech to make gas core nuclear rockets right now.
With nuclear rockets, you would have to solve vast PR problems though. Just consider the demands by the greens to close nuclear power stations, which are firmly on the ground. A nuclear-powered rocket, with the significant risk of an accident and its fuel being released into the environment, could face much more severe problems than nuclear power stations.
Even to me, who is usually pro-nuclear, it isn't clear that nuclear rockets launching from the surface of the earth is a good idea. Considering the hi
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I think you're wrong about that, as do the people doing most of the research on the subject.
In this discover.com article [discovermagazine.com] covering Brad Edwards' NASA-sponsored research into Space Elevator technology, his completed work under a $500,000 NASA research grant reveals the technological and economic feasibility of space elevators.
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Carbon fibre (Score:4, Interesting)
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Note that nanotubes != CF.
That said, people are already starting to incorporate nanotubes in composite materials. The two hard parts are that they're really slippery and it's hard to get the matrix to stick to them, and that they tend to clump up a lot. The increased length helps with the first problem -- slippery is less of a problem if there's more surface to stick to. I don't know about the dispersion.
Nanotube composites are already impressive. You can get things with 30-50% more stiffness, 50-20
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18 mm... Great! (Score:4, Funny)
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World's Tallest Midget (Score:2, Funny)
-l
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Great... (Score:4, Funny)
The real killer commercial application (Score:2, Interesting)
Then we will really see what Arthur C was talking about.
The applications for "diamond" fibre are enormous.
some perspective (Score:5, Informative)
Isolated nanotubes have been grown longer than this (I've grown isolated nanotubes longer than this, and I'm not a growth specialist), as have bundles of nanotubes. This is the longest array of pure, aligned, continuous nanotubes.
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The technology does not yet exist to piece together nanotubes strongly enough to make a space elevator... which is why I was careful to use the word "grow." If one could piece nanotubes together well enough, then everything does get much easier.
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a clarification (Score:1, Informative)
Remember also that the figure of merit of a CNT when used for its mechanical properties is the growth defect density per meter, and even for the best growth techniques so far this ends up being
Tag: Biotech (Score:1)
Is the word 'carbon' enough to be classified as 'biotech'? Is a pencil 'biotech' now?
RTFA (Score:2, Informative)
This is not "The World's Longest Carbon Nanotubes." It's the longest mass-producable parallel carbon nanotubes.
Space Elevator Progress Report anyone? (Score:2)
To be held up, a space elevator needs a FABRIC with a tensile strength of about 65GPa.
To build it, you'd want a safety factor of about two, thereby a tensile strength of about 120-130GPa.
I do not know the specs of the tubes from TFA, however
Very short INDIVIDUAL single-walled carbon nanotubes have been created (in a lab, in small quantities, using processes that may be prohibitively expensive) with measured individual fiber strength of about 60GPA.
"Very long" ones wer
whats the aspect ratio of these long tubes? (Score:2)
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Forget space. I just want my flying car they promised me ten years ago.
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The economics of space travel has very little to do with the technology w
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There's nothing particularly revolutionary about any of the physics underlying the SE. Once a point (that is not moving further and further away) of tensile strength (in polymer fabric you can weave, not in the individual material you build it from) is reached, you build it. Period.
If you can make fibers that behave more like thread and less like sand pebbles, you can load more into the fabric
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You do that while listening to your Nano? (Ipod Nano, that is)