Composite metallic sheathes: the key to low-cost, high strength (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀-based tapes?

Abstract

(Bi,Pb)2Sr2Ca2Cu3O10-based superconducting tapes were prepared by the powder-in-tube process, using a bimetallic sheath consisting of Ag and Ni. Ag was in contact with the superconducting ceramic core and acted as a protective layer against reaction between the external Ni sheath and the core. (Bi,Pb)2Sr2Ca2Cu3O10 phase formation was possible if a path for oxygen diffusion was opened in the Ni sheath. This was achieved by removing Ni on one edge of the tape edges by polishing. Transport critical current densities as high as 35 000 A cm−2 (77 K, self-field), corresponding to a je of about 11 000 A cm−2, were achieved in a single heat-treatment. The efficient protection offered by the Ag layer against Ni diffusion into the ceramic core suggests that Ag layers as thin as 5 µm may be applied, thus reducing the production costs. The superior stiffness of Ni provides a stronger sheath, greatly improving the mechanical stability of the composite, and may be responsible for the high ceramic densities and critical current densities obtained without intermediate densification.

Fabrication and Properties of Ag–Ni Bimetallic Sheathed (Bi,Pb)-2223 Tapes

“…The white and black regions are the Ag layer and the ceramic core, respectively, 3 μm, respectively. However, due to the finite diffusing depth of Ni toward Ag during sintering periods [15,17], the thickness of Ag layer can be much thinner in industrial production. Meanwhile, Figs.…”

“…However, it is reported that in composite Ag-Ni ribbons, which are used as substrates for Bi-2212 tapes, Ag can prevent the diffusion of Ni toward the Bi-2212 layer [15,16]. Thereafter, Ag-Ni composite-sheathed Bi-2223 tapes using Ni as the outer sheath were successfully manufactured by Grivel et al [17] and Li et al [18]. Though this tape is promising for enhancing mechanical properties and reducing production costs, tapes with long length and multi-filament core have not yet been successfully fabricated.…”

Deformation analysis for the superconductor-silver interface in the Bi-2223/Ag tape rolling process

“…As the silver and silver alloys can meet these requirements, silver is mainly used as the inner tube material and silver alloy is used as outer tube structure during the preparation of Bi-2223/Ag tapes. Grive l [10] replaced the outer sheath material by nickel and improved the mechanical stability and current performance of composite. Liang [11] investigated that the superconducting tapes using silver alloy as the outer tube and inner tube had the better mechanical strength compared to the commercial tapes.…”

Bi-2223 grain growth in Ag/Ni composite-sheathed tapes sintered at different oxygen partial pressures

“…Bi 1.8 Pb 0.33 Sr 1.87 Ca 2.0 Cu 3.0 O 10 + δ (Bi‐2223) material is a typical ceramic material. Ag/Ni composite‐sheathed Bi‐2223 (Bi‐2223/Ag/Ni) superconducting tapes have been fabricated successfully by Grivel and Chen et al in recent years. Owing to the advanced Ag/Ni composite‐sheathed technique, Bi‐2223/Ag/Ni tapes that have lower cost and higher strength show great superiority relative to traditional Bi‐2223/Ag tapes.…”