Diffusion barriers for metallic superconducting wires
In various embodiments, superconducting wires incorporate diffusion barriers composed of Nb alloys or Nb—Ta alloys that resist internal diffusion and provide superior mechanical strength to the wires.
1. A superconducting wire possessing diffusion resistance and mechanical strength, the superconducting wire comprising:
a wire matrix comprising Cu; and
a plurality of composite filaments embedded within the wire matrix,
wherein:
each composite filament comprises (i) a plurality of monofilaments, (ii) a diffusion barrier comprising a Nb alloy containing 0.1%-20% W or a Nb—Ta alloy containing 0.1%-20% W and extending through an axial dimension of the composite filament and surrounding the plurality of monofilaments, and (iii) a cladding comprising Cu surrounding the diffusion barrier, the diffusion barrier separating the cladding from the plurality of monofilaments,
the diffusion barriers collectively occupy 1%-20% of a cross-sectional area of the superconducting wire, and
each monofilament comprises a core comprising Nb and, surrounding the core, a cladding comprising Cu.
2. The wire of claim 1 , further comprising, disposed between the monofilaments and the diffusion barrier of at least one of the composite filaments, an annular region comprising a Nb-based superconducting phase.
3. The wire of claim 2 , wherein the annular region comprises Nb 3 Sn.
4. The wire of claim 2 , wherein the annular region conforms to and is contact with the diffusion barrier.
5. The wire of claim 1 , wherein the diffusion barriers collectively occupy 1%-10% of the cross-sectional area of the superconducting wire.
6. The wire of claim 1 , wherein the diffusion barriers collectively occupy 2%-10% of the cross-sectional area of the superconducting wire.
7. The wire of claim 1 , wherein the diffusion barriers collectively occupy 3%-10% of the cross-sectional area of the superconducting wire.
8. The wire of claim 1 , wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La.
9. The wire of claim 1 , wherein the core of each monofilament comprises Nb 3 Sn.
10. The wire of claim 1 , wherein the diffusion barrier comprises Nb-6W or Nb—Ta-3W.
11. The wire of claim 1 , wherein the diffusion barrier additionally contains one or more alloying elements selected from the group consisting of Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, or Si.
12. The wire of claim 1 , wherein a yield strength of the superconducting wire is at least 100 MPa.
13. The wire of claim 1 , wherein each of the composite filaments has a hexagonal cross-sectional shape.
14. The wire of claim 1 , wherein each of the monofilaments has a hexagonal cross-sectional shape.
15. The wire of claim 1 , further comprising a stabilizing element disposed within the plurality of composite filaments, the stabilizing element comprising a Ta alloy containing 0.1%-20% W, a Nb alloy containing 0.1%-20% W, or a Nb—Ta alloy containing 0.1%-20% W.
16. The wire of claim 1 , wherein the diffusion barrier comprises the Nb alloy containing 0.1%-20% W.
17. The wire of claim 1 , wherein the diffusion barrier comprises the Nb—Ta alloy containing 0.1%-20% W.
18. The wire of claim 15 , wherein the stabilizing element comprises the Ta alloy containing 0.1%-20% W, the Ta alloy being substantially free of Nb.
19. The wire of claim 15 , wherein the stabilizing element comprises the Nb alloy containing 0.1%-20% W, the Nb alloy being substantially free of Ta.
20. The wire of claim 15 , wherein the stabilizing element comprises the Nb—Ta alloy containing 0.1%-20% W.