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 user 2007-03-05 at 12:08:00 pm Views: 53
  • #17364

    The ‘new age’ of super materials
    high-speed trains, super-efficient power generators and ultra-powerful
    supercomputers would become commonplace thanks to a new breed of
    materials known as high temperature superconductors (HTSC).”The
    breakthroughs in superconductivity bring us to the threshold of a new
    age,” said the president. “It’s our task to herald in that new age with
    a rush.”But 20 years on, the new world does not seem to have arrived.
    So what happened?

    Early promise
    was first discovered in 1911 by researchers at the University of Leiden
    who used solid mercury in their experiments.Superconductors have no
    electrical resistance, so unlike conventional conductors they allow an
    electric current to flow through without any loss.At the start, the
    phenomenon was only seen in materials cooled close to absolute zero,
    which according to theory is the state of zero heat
    energy.Three-quarters of a century later, the highest temperature
    achieved for the onset of superconductivity, the so-called transition
    temperature, was a frigid 23 Kelvin (-250C).This allowed scientists to
    exploit the phenomenon in specialist applications such as Magnetic
    Resonance Imaging (MRI) scanners and high energy physics particle
    colliders, cooled by liquid helium.But more day-to-day applications,
    such as replacing the electricity grid with superconducting wires,
    remained impossible without materials able to operate at higher

    Closer to zero
    breakthrough came in 1986.Two IBM researchers, Georg Bednorz and Alex
    Mueller, discovered a new family of ceramic superconductors, known as
    the copper oxide perovskites, that operated at 35K (-238C)The work was
    rapidly followed up Paul Chu, of the University of Houston, who
    discovered materials operating at 93K (-182C)The discovery meant that
    superconductors had entered the temperature range of liquid nitrogen
    (77K, -196C), an abundant and well understood coolant.”All of a sudden
    everything was different,” said Professor Chu. “There was a euphoric
    feeling. People in the field thought nothing was impossible.”The
    discovery prompted a huge gathering of physicists in New York to
    discuss the breakthrough, a meeting later called the “Woodstock of

    Precise structure
    large-scale commercialisation of the technology would prove more
    difficult.”The material was not as simple as we originally thought,”
    said Professor Chu.Despite an intensive two-decade search, the
    underlying mechanism of superconductivity in the ceramics is still
    disputed.In addition, their exact structure, requiring ultra-thin
    layers of different elements stacked on top of each other, means they
    are very difficult and expensive to manufacture.”Atomically, you have
    to line them up very precisely in order for the supercurrent to flow,”
    explained Professor Chu.This, coupled with the fact that ceramics are
    brittle and difficult to turn into flexible wires and films, meant that
    prospects for immediate exploitation were not good.”I think the
    expectations were a little unrealistic,” said Dr Dennis Newns of
    IBM.The typical time it takes from inventing a new concept to
    application is 20 years,” he said. “And that is exactly what we have

    Cool running
    in Japan, Europe, China, South Korea and the US are forging ahead with
    applications.In the US, American Superconductor has developed a way to
    “bend the unbendable”, creating HTSC wires that can carry 150 times
    more electricity than the equivalent copper cables.”Twenty years ago
    you would see people making ceramic fibres and trying to bend them and
    it was like a dry stick of spaghetti,” said Greg Yurek, CEO and founder
    of the company.To get around this brittleness, the company embeds up to
    85 tiny filaments of superconducting ceramic in a ribbon of metal 4.4mm
    (0.17 inches) wide.”Think of optical fibres,” said Dr Yurek. “If you
    have a rod of glass and you whack it on your desk it will shatter.”Drop
    down to a fine optical fibre and it becomes flexible – it’s the same
    principle here.”The company also produces wires with a coating of the
    ceramic just one micron (millionth of a metre) thick on a metal alloy.
    Both are cooled by a sheath of liquid nitrogen.Short sections of the
    wires have already been installed in Columbus, Ohio, and a further
    half-mile of cable will soon be laid on Long Island, New York.In the
    short term, longer stretches of the supercooled cable will be difficult
    to install, as it requires an infrastructure to pump liquid nitrogen
    around the grid.But Dr Yurek believes that it will not be long before
    other firms start to offer utility companies these cryogenic
    services.”This is the model they have used in the MRI industry to
    guarantee the cold,” he said.

    Shrinking motors
    company also promotes its HTSC wires for other advanced
    applications.Central Japan Railways uses coils of it for their
    superconducting experimental magnetic levitation (maglev)
    train.American Superconductor has also developed an electric motor
    using coils of superconducting wire for use in the next generation of
    US Navy destroyers.Electric motors are used by most commercial cruise
    liners, but are typically very bulky.Using HTSC technology dramatically
    shrinks their size and also increases their efficiency.The company is
    just about to start testing its latest 36.5-megawatt engine that is
    cooled by off-the-shelf liquid helium refrigerators and weighs 75
    tonnes. By comparison, an engine based on copper wires would weigh 300
    tonnes.”That’s great for cruise ships and the navy, because they can
    use that space for other things like passenger cabins or munitions,”
    said Dr Yurek.

    “New age”
    things have also moved on.New superconductors have been found. For
    example, a new mercury-based compound has a transition temperature of
    134K (-139C)”When we applied pressure we raised it up to 164K (-109C) -
    that’s a record,” said Professor Chu.”Of course from an application
    point of view, it’s hopeless.”However, other experimental work raises
    the possibility of discovering room temperature superconductors that
    would require no exotic cooling equipment.A new theory, outlined in a
    paper in the journal Nature Physics by Dr Newns and his IBM colleague
    Dr Chang Tsuei, seeks to explain the elusive mechanism of
    superconductivity in the class of ceramics discovered in 1986.”We don’t
    see any fundamental limits,” said Dr Tsuei.”If someone discovered a
    room-temperature superconductor tomorrow that fits with what is
    outlined by our theory, we wouldn’t be surprised at all,” added Dr
    Newns.This kind of optimism, seen for the first time in the mid-1980s,
    now seems to be deserved.There has been a crescendo of research, while
    at the same time the first commercial HTSC products are rolling out of
    factories.According to Dr Yurek, this is a sign that the new age
    promised by Ronald Reagan is finally here.”I think we’re on a launching
    pad here and we’re now ready to take off,” he said.