Posted on 02/15/2006 4:19:40 AM PST by Neville72
Physicists in Japan have shown that "entirely end-bonded" multi-walled carbon nanotubes can superconduct at temperatures as high as 12 K, which is 30 times greater than for single-walled carbon nanotubes. The discovery has been made by a team led by Junji Haruyama of Aoyama Gakuin University in Kanagawa. The superconducting nanotubes could be used to study fundamental 1D quantum effects and also find practical applications in molecular quantum computing (Phys. Rev. Lett. 96 057001).
Superconductivity is the complete absence of electrical resistance and is observed in certain materials when they are cooled below a superconducting transition temperature (Tc). Physicists agree that superconductivity relies on getting electrons to overcome their mutual Coulomb repulsion and form "Cooper pairs". In the Bardeen-Cooper-Schrieffer (BCS) theory of low-temperature superconductivity, the electrons are held together because of their interactions with phonons -- lattice vibrations in the material.
However, 1D conductors like carbon nanotubes -- rolled up sheets of graphite just nanometres in diameter -- are not naturally superconducting. One reason for this is the presence of so-called Tomonaga-Luttinger liquid (TLL) states in the material, which cause the electrons to repulse each other and so destroy Cooper pairs.
Now, however, Haruyama and colleagues have designed a system in which there is a superconducting phase that can compete with the TLL phase and even overcome it -- a feat hitherto believed impossible. The system consists of an array of multi-walled carbon nanotubes, each of which consists of a series of concentric nanotube shells. Electrical contacts made of metal are bonded to the tubes so they touch the top of all the shells. Conventional "bulk junction" contacts, in contrast, touch only the outermost shell of a tube and along its length.
Haruyama and co-workers grew their multiwalled nanotubes from a template of porous alumina. Next, they cut the tops off the nanotubes using ultrasound or etching techniques and then evaporated a gold electrode onto the exposed ends of the tubes. In this way, nearly all of the nanotube shells were made electrically active.
The Japan team find that the end-bonded nanotubes lose all resistivity at temperatures below 12 K. According to the researchers, this is because the TLL states are suppressed so that superconductivity can appear. Moreover, the Tc depends on the numbers of electrically activated shells and the physicists will now try to increase this figure by making more or all of the shells active.
Gold medal for the nanotubes?
So its taking it up from .4 Kelvin to 12 Kelvin. In the sense of practicality this doesn't appear to be a banner event.
quantumn computing takes a step closer :-) good news indeed
This will give me something to talk about at the Possum hunt this weekend.
I can't wait to use the super-cooler to help with my air conditioning costs in the summer.
Gay electrons?...........
I always thought John Williams was a super conductor that works at room temperature.
How big were the tubes?
LOL!
All I want to know is how this will improve my downloading speed...
Buckyballs bond strongly with DNA.
No, it's absolutely huge. The simplest way of cooling something off is to surround it in a cooler fluid. There ain't a hell of a lot of stuff -- if anything -- that stays fluid at .4K. On the other hand, Helium boils at 4 degrees Kelvin. Now, I have no idea how it affects the nanotubules or their superconductivity, but if all you need to do to create an environment that's adequately cold is to pump it full of super-cooled Helium gas, we're talking being able to use these superconductors in computer labs!
*sigh* Most of the great conductors have reached room temperature. I still think Williams is super-cool, though.
That's really, really bad. LOL.
Beethoven's gone but his music lives on,
And Mozart don't go shoppin' no more,
You'll never meet Liszt or Brahms again,
And Elgar doesn't answer the door.
Schübert and Chopin used to chuckle and laugh,
Whilst composing a long symphony,
But one hundred and fifty years later,
There's very little of them left to see.
Chorus: They're decomposing composers,
There's nothing much anyone can do,
You can still hear Beethoven,
But Beethoven cannot hear you.
Verse: Händel and Haydn and Rachmaninov,
Enjoyed a nice drink with their meal,
But nowadays no-one will serve them,
And their gravy is left to congeal.
Verdi and Wagner delighted the crowds,
With their highly original sound,
The pianos they played are still working,
But they're both six feet underground.
Chorus: They're decomposing composers,
There's less of them every year,
You can say what you like to Debussy,
But there's not much of him left to hear.
Finish: Claude Achille Debussy, died 1918.
Christophe Willebaud Gluck, died 1787.
Carl Maria von Weber, not at all well
1825, died 1826. Giacomo Meyerbeer,
still alive 1863, not still alive 1864.
Modeste Mussorgsky, 1880 going to parties,
no fun anymore 1881. Johan Nepomuck
Hummel, chatting away nineteen to the
dozen with his mates down the pub every
evening 1836, 1837 nothing.
This will be a major helping to the advancement of man portable battlefield lasers, or lightsabers!
Realistically it really is important, almost as big by a good percentage compared to the advent of the silicon wafer or transistor as we know it, a switch with no contact points or moving parts.
If there was a much need worldwide device that would really take us a big leap into various fields is a battery containment device that has the output of a commercial truck battery the size of a D cell.
If it was possible it would nearly remove our dependence of third world oil, cars would not have to be miniscule and limited in speed or range anymore. Thats just one singular application.
I expect in less than 10 years we will se examples available, already batteries for cars are smaller and not of the traditional lead acid design.
But back to the article these nanotubes can be motors the size of a coffe cup putting out a 100 hp at high amperage through very small windings and no overheating. I can visualize not to mention what they can be used in submarines like hydromagnetic propulsion.
Yay. Quantum mechanics rule, mr goodwrench drools.
The benefit to us normal folks isn't here....yet. But this, along with a bunch of other buckyall, nanotube, etc, etc research is eventually going to make:
computers run 'faster'. So bill gates can roll out windows 2010, that needs 500 GB of ram just to boot
better body armor for the military. so muslim extremist nutjobs will shoot at individual troops with nothing less than rockets, 20 mm cannon or photonic burster incindiary rounds....
and flat screen tv will get flatter and larger. so hitachi, sony, etc, etc will develop a new format for movie storage and all the dvd players and discs will be obe....
but what's new about all that?
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