THE ’NEW AGE’ OF SUPER MATERIALS

[Anonymous]

The ‘new age’ of super materials
Levitating
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
Superconductivity
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
temperatures.

Closer to zero
The
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
Physics”.

Precise structure
But
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
seen.”

Cool running
Companies
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
The
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”
Experimentally,
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. 

[Author]

March 5, 2007 at 12:08 PM