Influence of Ni and Cu contamination on the superconducting properties of MgB 2 filaments. Jung, A., Schlachter, S., I., Runtsch, B., Ringsdorf, B., Fillinger, H., Orschulko, H., Drechsler, A., & Goldacker, W. Superconductor Science and Technology, 23(9):095006, 9, 2010.
abstract   bibtex   
Technical MgB2 wires usually have a sheath composite consisting of different metals. For the inner sheath with direct contact to the superconducting filament, chemically inert Nb may be used as a reaction barrier and thermal stabilization is provided by a highly conductive metal like Cu. A mechanical reinforcement can be achieved by the addition of stainless steel. In order to illuminate the influence of defects in the reaction barrier, monofilament in situ wires with direct contact between the MgB2 filament and frequently applied reactive sheath metals like Cu, Ni or Monel are studied. Reactions of Mg and B with a Cu-containing sheath lead to Cu-based by-products penetrating the whole filament. Reactions with Ni-containing sheaths lead to Ni-based by-products which tend to remain at the filament-sheath interface. Cu and/or Ni contamination of the filament lowers the MgB 2-forming temperature due to the eutectic reactionbetween Mg, Ni and Cu. Thus, for the samples heat-treated at low temperatures Jc and (partly) Tc are increased compared to stainless-steel-sheathed wires. At high heat treatment temperatures uncontaminated filaments lead to the highest Jc values. From the point of view of broken reaction barriers in real wires, the contamination of the filament with Cu and/or Ni does not necessarily constrain the superconductivity; it may even improve the properties of the wire, depending on the desired application. © 2010 IOP Publishing Ltd.
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 title = {Influence of Ni and Cu contamination on the superconducting properties of MgB 2 filaments},
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 abstract = {Technical MgB2 wires usually have a sheath composite consisting of different metals. For the inner sheath with direct contact to the superconducting filament, chemically inert Nb may be used as a reaction barrier and thermal stabilization is provided by a highly conductive metal like Cu. A mechanical reinforcement can be achieved by the addition of stainless steel. In order to illuminate the influence of defects in the reaction barrier, monofilament in situ wires with direct contact between the MgB2 filament and frequently applied reactive sheath metals like Cu, Ni or Monel are studied. Reactions of Mg and B with a Cu-containing sheath lead to Cu-based by-products penetrating the whole filament. Reactions with Ni-containing sheaths lead to Ni-based by-products which tend to remain at the filament-sheath interface. Cu and/or Ni contamination of the filament lowers the MgB 2-forming temperature due to the eutectic reactionbetween Mg, Ni and Cu. Thus, for the samples heat-treated at low temperatures Jc and (partly) Tc are increased compared to stainless-steel-sheathed wires. At high heat treatment temperatures uncontaminated filaments lead to the highest Jc values. From the point of view of broken reaction barriers in real wires, the contamination of the filament with Cu and/or Ni does not necessarily constrain the superconductivity; it may even improve the properties of the wire, depending on the desired application. © 2010 IOP Publishing Ltd.},
 bibtype = {article},
 author = {Jung, A and Schlachter, S I and Runtsch, B and Ringsdorf, B and Fillinger, H and Orschulko, H and Drechsler, A and Goldacker, W},
 journal = {Superconductor Science and Technology},
 number = {9}
}
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