The Stanly News and Press (Albemarle, NC)

State & National News

April 22, 2014

NCSU STUDY: Impurity Size Affects Performance of Emerging Superconductive Material

Tuesday, April 22, 2014 — Research from North Carolina State University finds that impurities can hurt performance – or possibly provide benefits – in a key superconductive material that is expected to find use in a host of applications, including future particle colliders. The size of the impurities determines whether they help or hinder the material’s performance.

At issue is a superconductive material called bismuth strontium calcium copper oxide (Bi2212). A superconductor is a material that can carry electricity without any loss – none of the energy is dissipated as heat, for example. Superconductive materials are currently used in medical MRI technology, and are expected to play a prominent role in emerging power technologies.

“Bi2212 is the only high-temperature superconductor that can be made as a round wire, and is expected to have applications in magnets for use in everything from magnetic resonance imaging technologies to the next generation of super colliders – almost anything that falls under the category of high-energy physics or requires a very high magnetic field,” says Golsa Naderi, a Ph.D. student at NC State and lead author of a paper describing the work.

To use Bi2212 for any of these potential applications, the material needs to be formed into a multifilamentary wire, which contains 500 to1,000 Bi2212 filaments embedded in silver, and then heat-treated to nearly 900 degrees C. However, this processing results in impurities in the material. These impurities largely consist of porosity and bismuth strontium copper oxide (Bi2201).

“We know that porosity, or the formation of voids in the Bi2212, is problematic. But we wanted to go beyond porosity and learn more about the Bi2201 impurities and how they could help or hurt Bi2212’s performance,” says Dr. Justin Schwartz, senior author of the paper and Kobe Steel Distinguished Professor and head of the Department of Materials Science and Engineering at NC State. “That would help us determine how to optimize the material’s superconducting characteristics through better processing.”

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