Huge energy savings and reductions in harmful greenhouse gas emissions are a step closer with the development of a commercially viable superconducting tape. Scientists at the Los Alamos National Laboratory in the US have devised a process capable of producing kilometres of the tape in a day. The tape operates at liquid nitrogen temperatures - a relatively warm 77 K - and can carry around 200 times more electrical current than an equivalent copper wire. "Electric motors, transformers, transmission cables and levitated trains will be some of the applications demanding hundreds of kilometres of these flexible tapes each year", says Dean Peterson, Leader of the Superconductivity Research Center at Los Alamos.
Researchers at the laboratory first created a superconducting tape five years ago. They used a process known as Ion Beam Assisted Deposition (IBAD) to create a film of the ceramic superconductor yttrium barium copper oxide onto a buffer layer of zirconia sitting on a base of nickel alloy tape. The buffer layer stops the superconductor reacting with the nickel tape and encourages the superconductor grains to lie flat and close together, increasing the current flow. In the IBAD process, an argon ion beam removes material from a zirconia source and deposits it on the nickel tape. A second beam then aligns the zirconia grains in preparation for deposition of the superconducting layer, which can be 1 – 6 µm thick.
But the team has recently found that a magnesium oxide buffer layer a hundred times thinner aligns the superconductor grains just as well as the zirconia layer. “This difference means we can manufacture a metre of tape in under a minute instead of the several hours it took with the thicker zirconia layer”, Peterson told PhysicsWeb. “This clearly has a knock-on effect on the cost, making it more commercially attractive.” The Los Alamos laboratory has teamed up with American Superconductor Corporation, 3M Corporation and Intermagnetics General Corporation to speed up commercial development of the process. The world market for superconducting tape in electrical power technologies is estimated to be worth up to $50bn by 2020.
