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Science

Superconductors that possibly work at room temp. 22

Posted by chrisd from the those-wily-carbon-tubules dept.
Anonymous Coward writes "University of Houston, Texas researchers have found subtle signs of superconductivity in nanotubes of carbon. They may conduct electricity without any resistance, at temperatures stretching up past the boiling point of water. See the story on EurekAlert"
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Superconductors that possibly work at room temp. More

Superconductors that possibly work at room temp.

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  • So... (Score:4, Funny)

    by Jeremiah Cornelius ( 137 ) on Wednesday November 28, 2001 @07:32PM (#2627889) Homepage Journal
    We make a GIANT nanotube, and power the whole city!
    • Not even for one...MILLION...dollars. ;)

      It's power transmission, not power production. Though, one could power cities more efficiently if one did not have to worry about losing power during transmission.
  • A non physicist/chemist guesses that it would take some really clean and pure carbon to get the "electrons to pair up" sufficently to superconduct.

    New Scientist is a pretty hep mag, tho. Maybe it's worth following this for the eventual IPO. :)

    • That's why the use nano-tubes. heard of a buckyball? same thing, in tube form. basically it's a superstable tube with carbon atoms linked to make the walls of the tube. It's also very strong, I heard rumours on the radio of useing nano-tubes to make a cable for a space elevator. (it was on a public radio science show, so it's somewhat reputable.) there are of course many problems to work through before this becomes a real possiblity.

  • The repugnant stench of New Scientist. (Score:3, Interesting)

    by deglr6328 ( 150198 ) on Wednesday November 28, 2001 @08:01PM (#2628022)
    Looking closely at the bottom of the page reveals the article's infamous origin:

    "PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS STORY AND, IF PUBLISHING ONLINE, PLEASE CARRY A HYPERLINK TO: www.newscientist.com"

    You see, New Scientist is a tabloid like sensationalistic uncredible rag. Trusting scientific information from New Scientist is like asking your auntie May who's an LPN to perform brain surgery on you.

    For instance one glaring oversight in the article:"To decide whether or not the nanotubes really are superconductors, you need to measure the resistance through a single tube, Alexandrov says."

    Alexandrov is apparently the only theoretical physicist left in the world who didnt see the Science article [www.ust.hk] 6 months ago finding that nanotubes superconduct. He also incorrectly states that "Superconductivity theories do not forbid the phenomenon at very high temperatures" this is totally incorect. Type one superconductors have a limit of about 40K and there are theories placing the upper limit of type II superconductors at 200K.
    • Granting, of course, that the upper limit on type I superconductors was 20K twenty years ago (check out good-old BCS theory). And, of course, type II superconductors were discovered by experimentalists before the theorists had any clue they existed.

      This field is still very much an experimental one.

      Alf

  • ...magnetic field?? (Score:3, Insightful)

    by Transcendent ( 204992 ) on Wednesday November 28, 2001 @09:49PM (#2628556)
    "For example, when the researchers put a magnetic field across a bundle at temperatures up to 400 kelvin (127 C), the bundle generated its own weak, opposing magnetic field. Such a reaction can be a sign of superconductivity."

    Correct me if I'm wrong, but I thought that all current carrying deviced generated their own opposing magnetic field.... even the wires going through most all buildings. The strenght of this magnetic field would allow us to calculate the resistance in the conductor, them stating that it produced a weak magnetic field doesn't prove much...

    • I thought that all current carrying deviced generated their own opposing magnetic field...

      Yup, where there's current, there's a field (unless there's something else going on that negates the field effect of the current... I've heard that buried electrical cables have no field because their sheathing is naturally grounded, for instance). Their point was that the induced magnetic field didn't go away after they shut off the main one. If the field was the result of induced current, then the fact that the field persists could mean that the induced current persists, indicating resistance close to zero. Then again, I can think of at least one other material that can retain a magnetic field and isn't superconducting... the ferroceramics used in hard disk platters.

      Note that I don't know much beyond high school physics and chemistry.

      • All conductors oppose changes in magnetic fields by having currents induced which try to preserve the original magnetic flux through the conductor. If there was no magnetic field, and you turn one on, a current will be induced so as to oppose the field. In a non-superconductor, those currents don't flow for very long before ohmic resistance does its thing. In a superconductor, they flow until the external magnetic field is removed, and the original flux is achieved without an induced current.

        Persistent currents, on the other hand, are created when you cool a superconducting ring (doesn't work with solid chunks because of the Meissner effect) below its critital temperature in a magnetic field, and then remove the external field. The superconductor has to maintain whatever magnetic flux through the ring that was present when it became superconducting, so a current is induced that mimics the external field. That current stays around until either the original external magnetic field is restored or the material ceases to be superconducting.

        And I'd damn well better know what I'm talking about, since this will be on the final in 2 weeks.

        (I didn't bother with much detail about the Meissner effect and its consequences. If you're confused about the persistent current part, I can explain that in detail.)

  • Done that... (Score:3, Funny)

    by zhiwenchong ( 155773 ) on Wednesday November 28, 2001 @10:11PM (#2628667)
    Researchers in Fairbanks Alaska announced last week that they have discovered a superconductor which will operate at room temperature.
    • Yeah, and a team at the University of Zagreb has found room temperature superconductors...

      Twice, now. (see Physica C, vol. 341-348 (2000), pages 723-725 for their latest attempt)

      Strangely, no one ever can seem to reproduce the results...

      Alf
  • Does anyone know of any realistic engineering applications of superconductivity? For example, products that one might see after a room-temperature superconductor is developed?

    I've heard all of these stories about stuff floating around, etc., but what's the real deal?

    • CPUs that produce no heat (or, at least, a lot less, if the transistors still produced heat but the rest of the circuits did not), super efficient long distance power transmission (look for this to be among the first uses, since it's among the simplest), power storage (get current going through a superconducting loop, then switch the loop back on itself so the current keeps going - though this might prove impossible to do, at least without losing small amounts of energy over time to the environment), all kinds of electromagnetic propulsion (technically available now, but can be done a lot better if one can use high amperages without worrying about melting the cables)...and that's just off the top of my head.
    • Effecient Powere transmission--no power loss due to resistance in the transmission lines.

      Extremly sensitive sensors: A macroscopic effect is that the magnetic field is fixed inside a superconducting ring. When the field changes, the superconductor generates a field to keep the field at its original value (to a limit of course). The amount of current is then easily measured and very sensitive measuresments can be done. This is all done at low temp now (450 below zero Far) but at room temperature you can see there things propogating into consumer electronics. Imagine one of those in a hard drive read head--your denisty could be HUGE and you have this nice tiny little sensor to read it all---
    • Does anyone know any application of transistors? They seem about equally useless.
    • 1) You save on electricity by using a power grid that does not dissipate electricity.

      2) You can have new kinds of memories, where instead of storing charge, you store a current, because you once you start a current going in a loop it keeps going forever.

      3) If you can make chips out of semiconductors and superconductors, then they won't warm up so much and you can use enormous clock speeds.

      4) You can make magnets that sustain fantastic magnetic fields without having to be cooled with liquid helium, thus reducing their cost dramatically. These are used in many scientific applications.

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