Researchers produce strong, transparent carbon nanotube sheets (big advance)

University of Texas at Dallas , physorg.com ^ | 18 Aug 05 | staff

[Arkie2]

Carbon nanotubes are like minute bits of string, and untold trillions of these invisible strings must be assembled to make useful macroscopic articles that can exploit the phenomenal mechanical and electronic properties of the individual nanotubes. In the Aug. 19 issue of the prestigious journal Science, scientists from the NanoTech Institute at UTD and a collaborator, Dr. Ken Atkinson from Commonwealth Scientific and Industrial Research Organization (CSIRO), a national laboratory in Australia, report such assembly of nanotubes into sheets at commercially useable rates.

Starting from chemically grown, self-assembled structures in which nanotubes are aligned like trees in a forest, the sheets are produced at up to seven meters per minute by the coordinated rotation of a trillion nanotubes per minute for every centimeter of sheet width. By comparison, the production rate for commercial wool spinning is 20 meters per minute. Unlike previous sheet fabrication methods using dispersions of nanotubes in liquids, which are quite slow, the dry-state process developed by the UTD-CSIRO team can use the ultra-long nanotubes needed for optimization of properties.

Strength normalized to weight is important for many applications, especially in space and aerospace, and this property of the nanotube sheets already exceeds that of the strongest steel sheets and the Mylar and Kapton sheets used for ultralight air vehicles and proposed for solar sails for space applications, according to the researchers. The nanotube sheets can be made so thin that a square kilometer of solar sail would weigh only 30 kilograms. While sheets normally have much lower strength than fibers or yarns, the strength of the nanotube sheets in the nanotube alignment direction already approaches the highest reported values for polymer-free nanotube yarns.

The nanotube sheets combine high transparency with high electronic conductivity, are highly flexible and provide giant gravimetric surface areas, which has enabled the team to demonstrate their use as electrodes for bright organic light emitting diodes for displays and as solar cells for light harvesting. Electrodes that can be reversibly deformed over 100 percent without losing electrical conductivity are needed for high stroke artificial muscles, and the Science article describes a simple method that makes this possible for the nanotube sheets.

The use of the nanotube sheets as planar incandescent sources of highly polarized infrared and visible radiation is also reported in the Science article. Since the nanotube sheets strongly absorb microwave radiation, which causes localized heating, the scientists were able to utilize a kitchen microwave oven to weld together plexiglas plates to make a window. Neither the electrical conductivity of the nanotube sheets nor their transparency was affected by the welding process -- which suggests a novel way to imbed these sheets as transparent heating elements and antennas for car windows. The nanotube sheets generate surprisingly low electronic noise and have an exceptionally low dependence of electronic conductivity on temperature. That suggests their possible application as high-quality sensors - which is a very active area of nanotube research.

"Rarely is a processing advance so elegantly simple that rapid commercialization seems possible, and rarely does such an advance so quickly enable diverse application demonstrations," said the article's corresponding author, Dr. Ray H. Baughman, Robert A. Welch Professor of Chemistry and director of the UTD NanoTech Institute. "Synergistic aspects of our nanotube sheet and twisted yarn fabrication technologies likely will help accelerate the commercialization of both technologies, and UTD and CSIRO are working together with companies and government laboratories to bring both technologies to the marketplace."

The breakthroughs resulted from the diverse expertise of the article's co-authors. Dr. Mei Zhang and Dr. Shaoli Fang, NanoTech Institute research scientists, first demonstrated the nanotube sheet fabrication process, and this result was translated into diverse applications by the entire team. The other team members include Dr. Anvar Zakhidov, associate director of the NanoTech Institute; Christopher Williams, Zakhidov's graduate student from the UTD Physics Department; Dr. Sergey Lee and Dr. Ali Aliev, research scientists at NanoTech Institute, in addition to Atkinson and Baughman.

The applications possibilities seem even much broader than the present demonstrations, Baughman said. For example, researchers from the Regenerative Neurobiology Division at Texas Scottish Rite Hospital for Children, Dr. Mario Romero, Director, and Dr. Pedro Galvan-Garcia, Senior Researcher Associate, and Dr. Larry Cauller, associate professor in UTD's neuroscience program, have initial evidence suggesting that healthy cells grow on these sheets - so they might eventually be applied as scaffolds for tissue growth.

Baughman said that numerous other applications possibilities exist and are being explored at UTD, including structural composites that are strong and tough; supercapacitors, batteries, fuel cells and thermal-energy-harvesting cells exploiting giant-surface-area nanotube sheet electrodes; light sources, displays, and X-ray sources that use the nanotube sheets as high-intensity sources of field-emitted electrons; and heat pipes for electronic equipment that exploit the high thermal conductivity of nanotubes. Multifunctional applications like nanotube sheets that simultaneously store energy and provide structural reinforcement for a side panel of an electrically powered vehicle also are promising, he said.

UTD researchers began collaborating with their counterparts at CSIRO last year. In November 2004, the organizations achieved a breakthrough by downsizing to the nanoscale methods used to spin wool and other fibers to produce futuristic yarns made from carbon nanotubes.

The latest research was funded by the Defense Advanced Research Projects Agency, an agency of the United States Department of Defense, the U.S. Air Force Office of Scientific Research, the Texas Advanced Technology Program, the Robert A. Welch Foundation and the Strategic Partnership for Research in Nanotechnology.

[JustAnotherOkie]

You could sew them into and invisible Bucky Ball Sack.

[solzhenitsyn]

"The latest research was funded by the Defense Advanced
Research Projects Agency, an agency of the United States
Department of Defense, the U.S. Air Force Office of Scientific
Research..."

Is DARPA trying to take credit for another one of Al Gore's inventions?!!

[Noumenon]

Yep

[darth]

Yup. Nanotubes, in theory, are 600X as strong as steel of the same weight. We should be able to run an elevator to geosychronous orbit and beyond. That's the real payoff.

[bayourod]

"We should be able to run an elevator to geosychronous orbit and beyond"

Who cares about that? I just want a giant flat screen TV that I can hang on the wall without having to use those damn expansion bolt thingies.

[<1/1,000,000th%]

Transparent aluminum has already been done. There was a thread on it.

[q_an_a]

just think what might be happening in Texas if Newt and a bunch of penny pinching GOP had not shut down the Super Collider 8 years ago. We spent more money on an overpass project called the High 5, conservative but short sighted GOP leaders stopped the idea machine and sent it to the Swiss.

Now we see funding for NanoTechnology by the Defense Dept, like money for the Internet spent 20 years ago. Good ideas are part of building and defending the country. Jobs come from research like this and the research is often funded by government. /broken promises for science research rant off.

[Lauretij2]

I have to agree, the shutting off to the Super Collider was one of the biggest mistakes Republicans ever did.

[q_an_a]

thanks for your post.

[doc30]

If the nanotubes break of and form dust, it would have health issues similar to asbestos dust. No company would dare to make or use them for fear of lawsuits. The trial lawyers would salivate at that prospect.

[TommyDale]

Spider webs are stronger than steel in the same size or weight.

[Graymatter]

Artificial muscles from nanotechnology? Wake me when human wings are over-the-counter. I want to fly. You can have the electric cars and the elevator to the moon, even the teleporter. Just give me wings.

[Drammach]

I think you're ahead of the curve and not (too) paranoid at all..

I read an article ( I have to locate it again ) concerning China's "big push" in Nanotech R&D..
They recognize it's future and want to get in on the ground floor, be a leader in the new technology..

I have no doubt that the Chinese are on this like a dog on a bone..
Unlimited Budget..

[RinaseaofDs]

What about tanks that move as fast as funny cars? Tanks with four times the rate of fire, where the whole thing is a highly sensitive antennae array for intercepting not just radiofrequency comms and radar, but even sound.

Somebody in a trench's stomach starts growling and you have four carbon nanotube armored tanks bearing down on you.

Body armor would probably render bullets obsolete. Best thing you could do with a machine gun is literally beat somebody to death with it. The impact of the round would still knock somebody over like a punch, but the bullet wouldn't go through.

[JamesP81]

Artificial muscles from nanotechnology? Wake me when human wings are over-the-counter. I want to fly. You can have the electric cars and the elevator to the moon, even the teleporter. Just give me wings.

Seriously, there is a number of books written by John Ringo (There Will be Dragons, Emerald Sea, Against the Tide) that deal with this stuff. In the future, mankind has genetically engineered himself and his environment. For kicks, someone engineered a real, live dragon. And his wings were made of carbon nanotubes so they could suppport their own weight.

We're talking about real science fiction here.

[JamesP81]

Body armor would probably render bullets obsolete.

Unlikely, for several reasons. First of all, and the most obvious solution, is to make carbon nano-tube ammunition, that is assuming that the nanotubes have good ballistic impact characteristics, which nothing I read in the article suggested.

Secondly, such armor would suffer from many of the same shortcomings that kevlar does. When a person is hit by a bullet, it's not the 30 caliber hole through them that kills. When you think about how redundant a human body is, it's hard to find a single place you could punch a small hole through someone and gurantee a kill.

This is where hydrostatic shock comes in. The human body is mostly water. When you throw a rock in a pond, you get a ripple effect from the center of where the rock landed in the pond. A similar thing happens when a bullet hits you, except the ripples are violently powerful. These ripples in the water in your body rupture your cells. This is what kills you. It's one of a couple of the reasons why gunshot wounds cause so much internal bleeding and leave large exit wounds. While nanotube armor may stop bullets (or may not, as I mentioned above), the armor still will not protect from the deadliest effect of a firearm: hydrostatic shock. If you're wearing armor and it stops a 30-06 moving at 3000 feet per second, you will still have to have medical attention within a short period, or you'll still die.

[Moral Hazard]

"Who cares about that? I just want a giant flat screen TV that I can hang on the wall without having to use those damn expansion bolt thingies."

And I want a giant flexible screen so I can create something like Circlevision, but in real time in my own house playing video games.

[Moral Hazard]

"just think what might be happening in Texas if Newt and a bunch of penny pinching GOP had not shut down the Super Collider 8 years ago."

Yeah, they might have discovered the Higgs Boson. Just think of the commercial implications!

[Moral Hazard]

"Body armor would probably render bullets obsolete."

I think there's an additional point here. The transparent nanotubes sheets may make it practical to create a bullet resistant face shield that a soldier can still see through.

[RinaseaofDs]

That's the point I was making when I said that the bullet would essentially serve only to beat a person to death. Can't violate the rules of physics.