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Superconductivity in the news
Posted on Thursday, October 04, 2007 @ 21:50:54 UTC by vlad
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Physics professor probes superconductivity
When Eric Hudson was introduced to high-temperature superconductivity
as a graduate student, it was still, so to speak, a hot topic.
The phenomenon, discovered in the 1980s,
reflects the fact that if you develop the right types of compounds, you
can create electrical conductors that are completely resistance-free at
temperatures well above the threshold for conventional superconductors.
"With conventional systems, you get to about 25
degrees Kelvin [-415 F] and then plateau," says Hudson, now the Class
of 1958 Assistant Professor of Physics at MIT. "With high-temperature
superconductivity, you were suddenly at 90 degrees Kelvin."
That figure is well above the mark at which nitrogen gas turns
liquid. This meant you could create devices like the high-powered
electromagnets used in many MRI scanners without having to use costly
liquid helium to cool the magnets' coils to superconducting
temperatures. (Helium, which liquefies at a hyper-frigid 4 degrees
above absolute zero, is a must for conventional superconducting
devices.)
More exciting yet, the discovery seemed to signal that
room-temperature superconductivity was on its way. This triggered
claims that problems like electricity line -losses--the often-hefty
amount of power lost to resistance in electrical transmission
networks--would soon -disappear.
But tough technological hurdles dampened hopes of a resistance-free
electrical grid. And for physicists like Hudson, the prospect of
figuring out how high-temperature superconductivity (HTS) works at the
scale of electrons and protons also faded.
"Initially, a ton of people rushed into the
field," he notes. "But in the late 1990s, a lot of them got fed up and
left."
Hudson was one of them, switching to another challenging physics
problem. But the HTS issue continued to lure him, and after two years
he resumed his studies of the phenomenon.
Why? Basically because it's so compelling. "It's a very difficult
problem," he notes, "and I feel that when we do understand it, that
will open up a whole new world, not only in superconductivity but in
related systems."
Hudson has probably helped hasten that day. He's an expert in
scanning tunneling microscopy, which is based on the stunning fact that
by bringing the right type of tiny metal tip within a few atoms' width
of a surface, and generating a voltage between the tip and that
surface, you can actually map its individual atoms. (To get a notion of
the length scales he's dealing with, consider that an atom of copper--a
standard component of many HTS compounds--is to a ping pong ball as the
ball is to the moon.)
Now, Hudson and his co-workers have contributed an advance in the
technology that promises new progress in unveiling HTS's secrets. Given
the all-but infinitesimal size of individual atoms, tunneling
microscope users until recently haven't been able to track individual
atoms within a compound as they lowered the compound's temperature. By
tweaking the makeup of a key part of their microscope, though, the MIT
group has solved the problem. That matters, says Hudson.
"If you want to understand what's going on as a function of
temperature in these materials," he explains, "you need to be able to
follow individual atoms."
The group's recent studies have already undercut one popular theory
about the changes that affect HTS materials as their temperature falls.
That finding may in turn clear the way for competing hypotheses.
Such advances, and the fact that organizations such as the U.S.
Department of Energy are again giving priority to the HTS phenomenon,
show the field is regaining its momentum. Yet while the world's
first-ever HTS electrical transmission line--an underground Albany-area
cable cooled by liquid nitrogen--went live on test basis last year, the
steps forward so far don't mean dramatic new applications are imminent.
On the other hand, Hudson does think basic research on the HTS
phenomenon is making real head way. "Things are at a point now," he
says, "where I believe we'll solve this within my professional
lifetime."
Source: MIT (Reprinted from MIT SPECTRVM, by Richard Anthony)
Via: http://www.physorg.com/news110726111.html
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New research sheds light on shimmering superconductivity and the courtship of electrons
In their normal state, electrons repel each other because of their
charge, but in the state of superconductivity, electrons pair up. John
Schlueter, a chemist from the U.S. Department of Energy's Argonne
National Laboratory, collaborated with a team of researchers from the
University of Oxford to better understand how this unlikely courtship
occurs.
Their recent research appears in the October 4 issue of Nature
and finds that a form of shimmering superconductivity exists at
temperatures well above that at which ordinary superconductivity is
destroyed. This electron courtship is characterized by a tension
between the conflicting urges for electrons to pair up (which leads to
superconductivity) and to repel each other (which leads to insulating
behavior).
Superconductors conduct electricity with absolutely no resistance
when cooled below a certain critical temperature, Tc.
“Superconductivity already has important applications and many more
uses are possible if critical temperatures are high enough,” Schlueter
explained.
Much research over the past decade has focused on inorganic cuprate
superconductors. Although molecular superconductors currently have
maximum Tcs near 10 K (nearly an order of magnitude lower than the
cuprates), they have many features that make them ideal for the study
of the fundamental properties of superconductivity. In the organic
materials, lower temperatures and magnetic fields are required to reach
the boundaries between superconducting and normal states, thus making
these experiments much easer to perform in a laboratory.
Although such shimmering superconductivity above the usual
temperature barrier has previously been observed in cuprate materials,
this is the first time it has been seen in an extremely clean and well
controlled system that doesn't have to be chemically doped to produce
superconductivity. This means that scientists can be sure that the
effect is not associated with impurities. In fact, the team believes
that such an effect should be found in all superconductors in which
conflicting interactions are finely balanced. This is an important step
forward in the quest to understand superconductivity in what are known
as "highly correlated" materials: the superconductors of the future.
The Argonne group has long been recognized as an
international leader in the discovery and crystallization of high
quality crystals of molecular superconductors. “We use an
electrocrystallization technique both as a discovery tool and a means
to enable sophisticated measurements aimed at unraveling some of the
outstanding mysteries of superconductivity,” Schlueter explained. This
research was performed on a superconducting material discovered by the
Argonne group in 1990, addresses a longstanding question relating to
the pairing of electrons in superconducting materials. The study
identifies similarities between the high and low temperature
superconductors.
The discovery was made by Moon-Sun Nam in collaboration with
Arzhang Ardavan and Stephen Blundell in Oxford University's Department
of Physics, using crystals grown by John Schlueter. The team exploited
a particularly sensitive probe of superconducting fluctuations called
the "vortex-Nernst effect". This effect provides a way of detecting
that superconducting vortices are present, even when zero electrical
resistance (the characteristic of traditional superconductivity) is not
exhibited.
Source: Argonne National Laboratory Via: http://www.physorg.com/news110726933.html
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Re: Ultraconductors(tm) - equivalent to Room Temperature Superconductors (Score: 1)
by Overtone on Thursday, October 04, 2007 @ 22:24:30 UTC
(User Info | Send a Message) http://www.magneticpowerinc.com | Polymer eyed for room-temp superconductivity
Chappell Brown 9/12/2005 EE Times
Peterborough, N.H. — In the early 1980s, a Russian physicist embarked
on a search for a room-temperature semiconductor. Twenty-five years
later, a U.S. company is looking to build on that quest and turn the
results into products.
The work centers on a form of polypropylene with an unusually high
conductivity first examined by Leonid Grigorov, a physicist at the
Polymer Institute of the Russian Academy of Sciences in Moscow. As a
dielectric, it should have been an effective insulator. The compound,
which was an unusual "atactic" form of the polymer, set Grigorov and
some of his colleagues off on the hunt for a room-temperature
superconductor.
Today
the torch has passed to Room Temperature Superconductors Inc.
(Sebastopol, Calif.), and although it is still not clear that an
ionized form of the polymer is actually a superconductor, CEO Mark
Goldes has become an evangelist for what he believes is a new "Type 3"
superconductor. Room Temperature Superconductors holds two (actually 3)
U.S. patents on the technology and has product plans for using it.
"Everything about this compound is counterintuitive," Goldes said.
"This was a waste material. It's atactic, which means that it is an
amorphous compound. It is a thermal insulator which conducts and it is
also magnetic, something that is never seen in polymers."
In the industrial form of polypropylene, the side chains attached to
the molecule's carbon backbone are arranged in a regular pattern. This
geometry promotes a type of crystalline packing that makes the polymer
very strong. In the atactic form, which can be produced by using too
much catalyst when the polymer is forming, the side chains are arranged
in a totally random pattern.
Air Force interest
Goldes first heard about the compound in 1991, when he saw an abstract
of a paper by Grigorov claiming the demonstration of superconduction at
room temperature in a polymer. Intrigued, Goldes contacted Grigorov and
got a fax of the paper in Russian, which he had translated. The paper
appeared six months later in a journal published by the American
Institute of Physics.
A year later, Goldes traveled to Grigorov's lab to look at the work
firsthand. "They had three floors of labs in Moscow and a number of
PhDs working on this," he said. "I came back and started looking for
backing to develop applications."
The U.S. Air Force was interested in the possibilities for the
compound, and Goldes eventually got four Small Business Innovative
Research grants to develop applications. "We eventually moved Grigorov
and his lab over here," he related. "That included 26 crates of lab
equipment and a very sensitive magnetic balance, which has been
critical in studying the superconductive properties of these polymers."
Subsequent work has shown that a number of polymers exhibit similar
conducting capabilities: olefin, acrylate, urethane and silicone-based
plastics. But the advent of this new class of highly conductive
polymers has not set off a stampede of research similar to what
happened when high-critical-temperature superconductors were discovered
in the 1980s.
Goldes explained that neither his small company nor the Air Force were
interested in publicizing the development. Now that two (three) patents
have been approved, he believes it is time to push the idea publicly.
The scientific community may be indifferent due to the inconclusive
experimental results with regard to superconductivity. So far, the
polymers have not exhibited all the characteristic signatures of
genuine superconductivity, although some are present. It is also
difficult to decouple the resistive behavior of the electrodes from the
polymer at room temperature.
"We can measure zero resistance with tin electrodes when the whole
system is cooled to 3.5 Kelvin, at which point the tin becomes a
superconductor," Goldes said. So far, attempts to measure zero
resistance at room temperature have come up against the problem of
resistance at the contact between the electrode and the film.
...The problem is evaluating a new compound that is being held as a
proprietary product. Goldes said independent groups have prepared
samples of the polymer and duplicated the same basic results.
The basic process for producing the highly conducting channels leads to
thin films on a conducting substrate. The atactic polymer is initially
in a liquid state and is ionized by UV radiation, which generates a
population of polarons (the form that free electrons take in a
polymer). By applying a large electric field perpendicular to the film,
the polarons form into thin threads, 1 to 2 microns in diameter, that
extend from the bottom to the top of the film. The polymer is then
cured, forming a solid dielectric with highly conducting threads
distributed through it.
The second patent describes methods for creating the films and lifting
them off to produce thermally insulating conducting films for a variety
of applications. The films could provide a protective layer between
metal electrodes and a corrosive substance without eliminating
electrical conductivity, for example. Another application cited is a
dense interconnecting layer for flip-chip mounting of ICs. The films
could also be used to form an electrical contact between
room-temperature electronics and cooled superconductors, or even long
wires of the conducting polymer for electric power. Goldes says his
company is pursuing approaches to doing that.
(Note: Three U.S. Patents have issued, and a very large application
is pending that will be broken into at least five more.
Ultraconductors have been independently reproduced under an Air Force contract. Earlier in 2007, a sucessful test was performed at Battelle Memorial Institute. MG).
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WARNING regarding Mark Goldes (aka Overtone) and Tom Bearden (Score: 1)
by DoItDontJustWriteAboutIt on Friday, October 05, 2007 @ 12:17:56 UTC
(User Info | Send a Message) | | If you are new to this site, be aware that two two guys are extraordinary BS artists who have been making unproven and irreproducible claims for years. Ignore them and hang onto your wallet. |
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