EE Times Article about Ultraconductors
Date: Wednesday, September 14, 2005 @ 18:38:51 GMT
Topic: General


Polymer eyed for room-temp superconductivity

Chappell Brown 9/12/2005

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 claims in the (first) two published patents are more conservative than what is published on Room Temperature Superconductors' Web site (www.ultraconductors.com). The patent states that films 100 microns thick have a "room-temperature conductivity in excess of 106 S/cm"; the Web site says conductivities exceed 1011 to 1024. The minimum figure in the patent is about 10 times the room-temperature conductivity of normal metal conductors. Of course, this may represent progress since the patent was issued in 1998.

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 now issued, and a very large application is pending. This will be broken into at least five more).

Mark Goldes
mgoldes@msn.com





This article comes from ZPEnergy.com
http://www.zpenergy.com

The URL for this story is:
http://www.zpenergy.com/modules.php?name=News&file=article&sid=1510