JP7110372B2 - Diffusion barrier for metallic superconducting wires - Google Patents

Description

(Related application)
This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/639,530, filed March 7, 2018, the entire disclosure of which is incorporated herein by reference.

In various embodiments, the present invention relates to the formation and processing of superconducting wires that incorporate diffusion barriers to prevent interdiffusion.

A superconducting material exhibits no electrical resistance when cooled below its characteristic critical temperature. High-temperature superconductor materials have been identified that have critical temperatures higher than the 77 K boiling point of nitrogen, but these materials are often exotic (e.g., perovskite ceramics) and difficult to process. , unsuitable for high field applications. Therefore, for practical superconducting applications requiring wires and coils and their bundles, the metallic superconductors Nb—Ti and Nb ₃ Sn are most often utilized. Although these materials have critical temperatures below 77 K, the relative ease of processing these materials (e.g., drawn into wires) and their ability to operate at high currents and magnetic fields limit their resulting in widespread use.

A typical metallic superconducting wire is characterized by multiple strands (or "filaments") of a superconducting phase embedded within a copper (Cu) conductive matrix. Nb--Ti is sufficiently ductile to be drawn directly into thin wires, but its applicability is typically limited to applications featuring magnetic fields with strengths below about 8 Tesla. . Nb ₃ Sn is a brittle intermetallic phase that cannot withstand wire drawing deformation, and is therefore typically formed after wire drawing via diffusion heat treatment. Nb ₃ Sn superconducting materials can typically be used in applications featuring magnetic fields having strengths up to at least 20 Tesla. Accordingly, several different techniques have been utilized to fabricate Nb ₃ Sn-based superconducting wires. For example, in the “bronze process,” large composites are fabricated from Nb rods and Cu—Sn alloy rods (eg, containing 13-15% Sn) surrounding the Nb rods. Due to the ductility of these materials, the composite may be stretched to a suitable diameter and then the stretched composite is annealed. A heat treatment results in interdiffusion and formation of a Nb ₃ Sn phase at the interface between Nb and Cu—Sn. Other processes for forming Nb3Sn _- based superconducting wires also involve the formation of brittle _Nb3Sn phases after wire drawing as well. For example, pure Sn or a Sn alloy with Cu or Mg may be incorporated inside the initial composite and annealed after stretching. Alternatively, Nb filaments may be embedded in a Cu matrix and drawn into wires. The resulting wire may subsequently be coated with Sn. The coated wire is heated to form a Sn--Cu phase which eventually reacts with the Nb filaments to form a Nb ₃ Sn phase.

Although the techniques detailed above have resulted in successful fabrication of metallic superconducting wires utilized in many different applications, the resulting wires often exhibit poor electrical performance. Typical superconducting wires are embedded in, placed around, and/or Cu or Cu-containing stabilizers that provide the wire with sufficient ductility for handling and incorporation within industrial systems. It contains many of the Nb ₃ Sn or Nb—Ti filaments described above surrounded by it. Although the stabilizer itself is not superconducting, the high conductivity of Cu can enable satisfactory overall electrical performance of the wire. Unfortunately, various elements (eg, Sn) from the superconducting filaments can react with portions of the Cu-based stabilizer and form low-conductivity phases that adversely affect the overall conductivity of the wire as a whole. Diffusion barriers have been utilized to shield the stabilizer from the superconducting filaments, but these barriers tend to have non-uniform cross-sectional areas, leading to non-uniformity during co-processing of the diffusion barrier and stabilizer. It can even rupture locally due to such deformation. Such a diffusion barrier can simply be made thicker, but such a solution affects the overall conductivity of the wire due to the lower conductivity of the diffusion barrier material itself. For state-of-the-art and future applications such as new particle accelerators and impactors, magnets are being designed beyond existing wire capabilities, such wires exceeding 2,000 A/mm ² at 15 Tesla Non-copper critical current densities would be required. Since the diffusion barrier is part of the non-copper piece, minimizing the volume of any barrier material is important, while any strength benefit is advantageous.

In light of the foregoing, substantially no detrimental reactions with stabilizers or various elements (e.g., Cu) while remaining uniformly thin so as not to occupy a significant amount of the overall cross-sectional area of the wire. There is a need for improved diffusion barriers for metallic superconducting wires that effectively prevent

According to various embodiments of the present invention, the superconducting wire and/or its precursors (e.g., composite filaments utilized to form the wire) comprise, consist essentially of, a niobium (Nb) alloy, or consisting of one or more diffusion barriers. A diffusion barrier is typically between at least a portion of the Cu wire matrix and the superconducting filament and/or within the superconducting filament and the superconducting wire for additional mechanical strength and/or or a stabilizing element incorporated around it. According to embodiments of the present invention, each monofilament comprises, consists essentially of, or may consist of, a Nb-based core within a Cu-based (e.g., Cu or bronze (Cu—Sn)) matrix, A laminated assembly of monofilaments may be placed in a Cu-based matrix and stretched to form a composite filament. Thus, each composite filament may comprise, consist essentially of, or consist of a plurality of Nb-based monofilaments within a Cu-based matrix. A diffusion barrier according to embodiments of the present invention may be disposed around each composite filament as the composite filaments are stacked to form the final wire, and/or the diffusion barrier may be a stack of composite filaments. and between the stack of composite filaments and the outer Cu stabilizer or matrix.

In various embodiments, a composite filament is placed in a Cu-based matrix (eg, a Cu-based tube), drawn into a superconducting wire (or precursor thereof), and heat treated. One or more of the composite filaments may themselves incorporate diffusion barriers therein and/or diffusion barriers are disposed within the Cu-based matrix of the superconducting wire and around the composite filaments. may be In various embodiments, the diffusion barrier is, for example, 0.1%-20% W, 0.2%-15% W, 0.2%-12% W, 0.2%-10% comprising, consisting essentially of, or consisting of W, 0.2% to 8% W, or an Nb—W alloy containing 0.2% to 5% W; For example, the diffusion barrier may be an alloy of Nb and about 11%-12% W (i.e., Nb-12W) or an alloy of Nb and about 5%-6% W (i.e., Nb-6W); or may comprise, consist essentially of, or consist of an alloy of Nb and about 2.5% to 3% W (ie, Nb-3W). In various embodiments, the diffusion barrier has one or more additional alloying elements therein, such as Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, and/or Si. comprising, consisting essentially of, or consisting of a Nb—W alloy (eg, Nb-12W, Nb-6W, or Nb-3W) with Such alloying elements may be up to 5% by weight or even up to 10% by weight (eg 0.05%-10%, 0.05%-5%, 0.1%-3%, 0 0.2%-2%, 0.2%-1%, or 0.2%-0.5%), individually or collectively, in the diffusion barrier. In various embodiments of the present invention, welds formed of Nb—W alloys incorporating one or more of these additional alloying elements are more uniform towards the center of such welds. It may have a grained structure that is axial, so welded tubes formed of these materials for use as diffusion barriers exhibit excellent mechanical properties when stretched to small sizes during wire processing. properties and processability.

According to various embodiments of the invention, the diffusion barrier may include one or more alloying elements such as W, Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, and/or Si. Such alloying elements may individually or collectively be up to 5% by weight or even up to 10% by weight (eg 0.05%-10%, 0.05%-5%, 0.1 %-3%, 0.2%-2%, 0.2%-1%, or 0.2%-0.5%) in the diffusion barrier. In various embodiments, filaments and/or diffusion barriers according to embodiments of the invention may be substantially free of Mg, B, Fe, Al, and/or Ni.

In various embodiments of the present invention, the diffusion barrier comprises, consists essentially of, an alloy or mixture containing both Nb and tantalum (Ta) and one or more alloying elements such as W or may consist of For example, the diffusion barrier may be an alloy of Nb, Ta, and about 2.5-3 atomic percent W (i.e., Nb—Ta -3W), may consist essentially of, or consist of. In various embodiments, the diffusion barrier may comprise, consist essentially of, or consist of a Nb--Ta--W alloy containing, for example, W within a concentration of 0.2-12 atomic percent. The diffusion barrier according to embodiments of the present invention comprises at least 1% Ta, at least 5% Ta, at least 8% Ta, at least 10% Ta, at least 15% Ta, at least 20% Ta, at least 25% Ta It may contain Ta, at least 30% Ta, at least 35% Ta, at least 40% Ta, or at least 45% Ta. Diffusion barriers according to embodiments of the present invention are up to 50% Ta, up to 45% Ta, up to 40% Ta, up to 35% Ta, up to 30% Ta, up to 25% Ta, It may contain Ta, up to 20% Ta, up to 15% Ta, up to 10% Ta, up to 5% Ta, or up to 2% Ta.

Diffusion barriers according to embodiments of the present invention comprise alloys or mixtures containing Nb (or Nb and Ta) and, instead of (or in addition to) W, one or more alloying elements, then essentially may consist of or consist of For example, such alloying elements may include C and/or N. Reference herein to diffusion barrier alloys containing W is understood to include alloys containing alloying elements such as C and/or N instead of or in addition to W.

Nb alloy diffusion barriers according to embodiments of the present invention may also exhibit advantageous ductility due, at least in part, to the low oxygen content and/or high level of purity. For example, diffusion barriers according to embodiments of the present invention have an oxygen content of less than 500 ppm, less than 200 ppm, less than 100 ppm, or even less than 50 ppm. The oxygen content may be at least 0.5 ppm, at least 1 ppm, at least 2 ppm, or at least 5 ppm. Additionally or alternatively, diffusion barriers according to embodiments of the present invention may have a purity greater than 99.9%, or even greater than 99.99%.

Advantageously, the Nb-alloy diffusion barrier according to embodiments of the present invention has a refined grain structure (e.g., small average grain size) when compared to conventional diffusion barrier materials, which is advantageous for superconducting wires. Allows deformation and processing of the diffusion barrier within to be substantially uniform without localized thinning, which can rupture the diffusion barrier and compromise wire properties. The small grain size of the diffusion barrier (eg, less than 20 μm, less than 10 μm, less than 5 μm, 1-20 μm, or 5-15 μm) is due to the presence of alloying elements, thus diffusion barriers according to embodiments of the present invention are: No additional processing (eg, forging, such as triaxial forging, heat treatment, etc.) is required to produce a refined grain structure. Overall manufacturing costs and complexity can thus be reduced through the use of diffusion barriers according to the present invention.

The superior grain structure and/or mechanical properties of diffusion barriers according to embodiments of the present invention allow the diffusion barriers to have a detrimental to provide protection from the spread of (In contrast, the use of various other diffusion barriers with poorer mechanical properties and/or less refined grain structure may affect the final wire ductility, electrical conductivity, and/or various other below their critical temperature, wires according to embodiments of the present invention exhibit good high-field, high-current superconducting properties. while retaining little or no interdiffusion with the Cu matrix.

The use of a Nb alloy diffusion barrier advantageously allows less cross-section of the superconducting wire to be occupied by the diffusion barrier, and thus more cross-section can be occupied by the current-carrying superconducting filament. However, diffusion barrier materials according to embodiments of the present invention also advantageously provide additional mechanical strength below their critical temperature to superconducting wires while retaining good high-field, high-current superconducting properties. provide to In various embodiments, the mechanical strength of the wire is determined without compromising the electrical performance of the wire and/or without causing cracks or fractures within the wire and/or its filaments, or otherwise its mechanical stability. It can facilitate mechanical deformation of the wire (eg, windings, coils, etc.) without damaging the In various embodiments, the diffusion barriers, collectively or individually, comprise at least 0.5%, at least 1%, at least 2%, at least 3%, at least 4%, at least 5% of the cross-sectional area of the final wire. %, or at least 7%. In various embodiments, the diffusion barriers, collectively or individually, are less than 20%, less than 15%, less than 12%, less than 10%, less than 9%, or less than 8% of the cross-sectional area of the final wire. , less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%. Thus, the diffusion barrier within the superconducting wire is with a minimum yield strength of at least 75 MPa, at least 100 MPa, or even 150 MPa (e.g., after any heat treatment of the wire and/or filament), according to various embodiments. Provide wires. Alternatively or additionally, wires containing one or more diffusion barriers according to various embodiments exhibit an ultimate tensile strength of at least 250 MPa, at least 300 MPa, or even at least 350 MPa. In various embodiments, the diffusion barriers, collectively or individually, are greater than 25% of the final wire cross-sectional area and/or less than 35% or less than 30% of the final wire cross-sectional area. may occupy. Mechanical properties, such as yield strength and ultimate tensile strength, of wires according to embodiments of the present invention are determined according to ASTM E8/E8M-15a, Standard Test Methods for Tension Testing of Metallic Materials, ASTM International, West Conshohocken, PA, 2015 (disclosure incorporated herein by reference).

The enhanced mechanical strength of superconducting wires according to embodiments of the present invention advantageously enables such wires to withstand the Lorentz forces exerted on them during operation at high magnetic field strengths. As is known in the art, the "self-field" in the magnet windings is higher than the centerline magnetic field and highest in the innermost winding. Additionally, the current required to create the magnetic field is the same in all wires within the magnet. The Lorentz force is F=B×I (ie, the magnetic field multiplied by the current) and the generated field is directly proportional to the current I, so the force is proportional to the square of the current. For example, the Lorentz force will be four times higher at 16 Tesla compared to 8 Tesla. Therefore, when the applied magnetic field is increased in magnitude, the mechanical strength of the wire to withstand the force (perpendicular to both the current and the field, via the cross product relation) must be higher as well. must. Superconducting wires according to embodiments of the present invention advantageously have a strength of at least 2 Tesla, at least 5 Tesla, at least 8 Tesla, or even at least 10 Tesla, i.e. at least 20,000 Gauss, at least 50,000 Gauss, It can be deployed for applications utilizing magnetic fields with magnetic flux densities of at least 80,000 Gauss, or even at least 100,000 Gauss.

In addition, since the diffusion barrier according to embodiments of the present invention comprises Nb, in various embodiments a portion of the diffusion barrier is advantageously subjected during the wire working process (e.g., one or more heat treatments/ During the annealing step), it can react (eg with Sn or Ti) to form a superconducting phase (eg Nb ₃ Sn or Nb-Ti) that contributes to the superconducting conductivity of the final wire. In such embodiments, the thickness of the diffusion barrier is typically large enough to prevent the entire diffusion barrier (or at least the Nb therein) from reacting, thus leaving the remainder of the diffusion barrier The unreacted portion not only provides resistance to interdiffusion, but also increased mechanical strength (eg, due to the presence of alloying elements such as W). In various embodiments, the reaction portion of the diffusion barrier thus exists within the wire as an annular (or other shape that mimics the shape of the diffusion barrier) reaction area. In various embodiments, the non-Nb alloying elements (e.g., Ta, W, etc.) cannot react to form a superconducting phase within the reaction region, thus they cannot diffuse during the reaction. It can be expelled from the reactive portion of the barrier. Therefore, at the interface between the reacted portion of the diffusion barrier and the unreacted remainder of the diffusion barrier, one or more (or even all) of such non-Nb elements may be present with the reacted portion of the diffusion barrier. It may be present in a higher concentration than in the opposite portion. In other embodiments, the unreacted remainder of the diffusion barrier comprises one or more such non-Nb elements that were present prior to reaction (e.g., when the diffusion barrier was introduced during the wire fabrication process). Contains higher concentrations. Therefore, even after a portion of the diffusion barrier reacts to form a superconducting phase and the thickness of the remaining diffusion barrier is reduced, a higher concentration of one or more non-Nb elements therein Despite its reduced thickness, it may increase the mechanical strength and/or diffusion resistance of the remaining thinner diffusion barrier.

In various embodiments, the diffusion barrier wherein one or more of the layers therein comprises, consists essentially of, or consists of a Nb alloy as detailed herein, Nb alloys in which one or more other layers contain Nb (or lower concentrations of one or more of the non-Nb alloying elements; referred to herein as "Nb layers" or "layers of Nb") Reference may also be to a multi-layered annular structure comprising, consisting essentially of, or consisting of (including such layers). For example, the diffusion barrier may comprise, consist essentially of, or consist of an inner layer of Nb surrounded by an outer layer of Nb alloy, or vice versa. In another embodiment, the diffusion barrier may comprise, consist essentially of, or consist of a layer of Nb alloy sandwiched between an inner layer of Nb and an outer layer of Nb. As detailed herein, during the heat treatment, all or part of the Nb layer of the diffusion barrier may be converted to the superconducting phase, while the Nb alloy layer remains unconverted.

Embodiments of the present invention may also incorporate stabilizing elements within the wire itself and/or within the composite filaments utilized to form the wire. For example, embodiments of the present invention are disclosed in US patent application Ser. No. 15/205,804, filed Jul. 8, 2016 ("'804 Applications”), Ta, a Ta alloy (e.g., an alloy of Ta and W such as Ta-3W), or one of Hf, Ti, Zr, Ta, V, Y, Mo, or W A stabilizing element comprising, consisting essentially of, or consisting of an alloy of Nb with one or more may be incorporated. In superconducting wires according to the invention, the stabilizing elements are typically separated from the monofilaments and/or composite filaments via one or more diffusion barriers therebetween.

In one aspect, embodiments of the invention include an outer wire matrix, a diffusion barrier disposed within the wire matrix, and a plurality of composite filaments surrounded by the diffusion barrier and separated from the outer wire matrix by the diffusion barrier. A superconducting wire comprising, consisting essentially of, or consisting of the same. The outer wire matrix comprises, consists essentially of, or consists of Cu. The diffusion barrier is a Nb--W alloy (eg, a Nb alloy containing 0.1%-20% W or 0.2%-12% W or 0.2%-10% W) or Nb--Ta comprising, consisting essentially of, or consisting of -W alloys. One or more, or even each, of the composite filaments comprises, consists essentially of, or consists of (i) a plurality of monofilaments and (ii) a cladding surrounding the plurality of monofilaments. The composite filament cladding may comprise, consist essentially of, or consist of Cu. One or more, or even each, of the monofilaments comprises, consists essentially of, or consists of a core and a cladding surrounding the core. The monofilament core may comprise, consist essentially of, or consist of Nb. The monofilament cladding may comprise, consist essentially of, or consist of Cu. The diffusion barrier extends through the axial dimension of the superconducting wire.

Embodiments of the invention may include one or more of the following, in any of a variety of combinations. The diffusion barrier may occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. The diffusion barrier is greater than about 1% of the cross section of the wire, greater than about 2% of the cross section of the wire, greater than about 5% of the cross section of the wire, greater than about 8% of the cross section of the wire, or may occupy more than about 10% of the cross-section of the The wire may include an annular region or layer positioned proximate to the diffusion barrier (e.g., on one or both sides thereof, e.g., positioned between the composite filament and the diffusion barrier), wherein at least A portion may comprise, consist essentially of, or consist of a Nb-based superconducting phase (eg, Nb—Ti and/or Nb ₃ Sn). A portion of the annular region may comprise, consist essentially of, or consist of a Nb alloy or Nb--Ta alloy having a composition different from that of the diffusion barrier. The annular region may conform to and/or be in direct mechanical contact with the diffusion barrier.

one or more of the monofilaments, or additionally each core, containing Nb and one or more of Ti, Zr, Hf, Ta, Y, or La, an alloy, pseudoalloy, or It may comprise, consist essentially of, or consist of a mixture (eg, Nb-Ti). One or more of the monofilaments or even each core may comprise, consist essentially of, or consist of Nb ₃ Sn. The diffusion barrier may comprise, consist essentially of, or consist of Nb-3W or Nb-6W or Nb-12W. The diffusion barrier may additionally contain one or more alloying elements selected from the group consisting of Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, or Si. The cross-sectional thickness and/or cross-sectional area of the diffusion barrier may be substantially constant along the thickness of the wire. One or more or even each of the composite filaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire). One or more or even each of the monofilaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire).

The wire may include stabilizing elements disposed within the plurality of composite filaments and surrounded by a diffusion barrier. The stabilizing element consists essentially of a Cu and/or Ta alloy containing 0.1% to 20% W or 0.2% to 12% W or 0.2% to 10% W may consist of or consist of At least part of the stabilizing element may be located substantially in the central core of the superconducting wire. The stabilizing element may occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. The stabilizing element is greater than about 1% of the cross-section of the wire, greater than about 2% of the cross-section of the wire, greater than about 5% of the cross-section of the wire, greater than about 8% of the cross-section of the wire, or It may occupy more than about 10% of the cross-section of the wire.

In another aspect, an embodiment of the invention features a superconducting wire comprising, consisting essentially of, or consisting of a wire matrix and a plurality of composite filaments embedded within the wire matrix. The wire matrix comprises, consists essentially of, or consists of Cu. one or more or even each of the composite filaments comprises: (i) a plurality of monofilaments; (ii) a diffusion barrier extending through an axial dimension of the composite filaments and surrounding the plurality of monofilaments; and (iii) ) a cladding surrounding a diffusion barrier, the diffusion barrier including, consisting essentially of, or consisting of a cladding separating the cladding from the plurality of monofilaments; The composite filament diffusion barrier is a Nb--W alloy or Nb--Ta--W (e.g. containing 0.1%-20% W or 0.2%-12% W or 0.2%-10% W containing, consisting essentially of, or consisting of Nb alloys or Nb--Ta alloys). The composite filament cladding comprises, consists essentially of, or consists of Cu. One or more, or even each, of the monofilaments comprises, consists essentially of, or consists of a core and a cladding surrounding the core. The monofilament core may comprise, consist essentially of, or consist of Nb. The monofilament cladding may comprise, consist essentially of, or consist of Cu.

Embodiments of the invention may include one or more of the following, in any of a variety of combinations. The diffusion barriers may collectively occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. . Diffusion barriers collectively greater than about 1% of the cross-section of the wire, greater than about 2% of the cross-section of the wire, greater than about 5% of the cross-section of the wire, greater than about 8% of the cross-section of the wire or more than about 10% of the cross-section of the wire. The wire is positioned proximate to at least one diffusion barrier (e.g., positioned on one or both sides thereof, e.g., between at least one diffusion barrier of the monofilament and the composite filament), an annular region or layer, and at least a portion of the annular region may comprise, consist essentially of, or consist of a Nb-based superconducting phase (eg, Nb—Ti and/or Nb ₃ Sn). A portion of the annular region may comprise, consist essentially of, or consist of a Nb alloy or Nb--Ta alloy having a composition different from that of the diffusion barrier. The annular region may conform to and/or be in direct mechanical contact with the diffusion barrier.

one or more of the monofilaments, or additionally each core, containing Nb and one or more of Ti, Zr, Hf, Ta, Y, or La, an alloy, pseudoalloy, or It may comprise, consist essentially of, or consist of a mixture (eg, Nb-Ti). One or more of the monofilaments or even each core may comprise, consist essentially of, or consist of Nb ₃ Sn. The diffusion barrier may comprise, consist essentially of, or consist of Nb3W, Nb-6W, or Nb-12W. The diffusion barrier may additionally contain one or more alloying elements selected from the group consisting of Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, or Si. The cross-sectional thickness and/or cross-sectional area of the diffusion barrier may be substantially constant along the thickness of the wire. One or more or even each of the composite filaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire). One or more or even each of the monofilaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire).

The wire may include stabilizing elements disposed within the plurality of composite filaments. The stabilizing element consists essentially of a Cu and/or Ta alloy containing 0.1% to 20% W or 0.2% to 12% W or 0.2% to 10% W may consist of or consist of At least part of the stabilizing element may be located substantially in the central core of the superconducting wire. The stabilizing element may occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. The stabilizing element is greater than about 1% of the cross-section of the wire, greater than about 2% of the cross-section of the wire, greater than about 5% of the cross-section of the wire, greater than about 8% of the cross-section of the wire, or It may occupy more than about 10% of the cross-section of the wire.

In yet another aspect, embodiments of the present invention include an inner wire stabilizing matrix, a diffusion barrier disposed about the wire stabilizing matrix, and a diffusion barrier disposed about the diffusion barrier such that the diffusion barrier prevents the wire stabilizing matrix from A superconducting wire comprising, consisting essentially of, or consisting of a plurality of composite filaments that are separated. The wire stabilization matrix comprises, consists essentially of, or consists of Cu. The diffusion barrier contains Nb--W alloy or Nb--Ta--W alloy (for example, 0.1%-20% W or 0.2%-12% W or 0.2%-10% W Nb alloy or Nb--Ta alloy). one or more, or even each, of the composite filaments comprises, consists essentially of, or consists of (i) a plurality of monofilaments and (ii) (iii) a cladding surrounding the plurality of monofilaments consists of The composite filament cladding comprises, consists essentially of, or consists of Cu. The diffusion barrier extends through the axial dimension of the wire.

Embodiments of the invention may include one or more of the following, in any of a variety of combinations. The diffusion barrier may occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. The diffusion barrier is greater than about 1% of the cross section of the wire, greater than about 2% of the cross section of the wire, greater than about 5% of the cross section of the wire, greater than about 8% of the cross section of the wire, or may occupy more than about 10% of the cross-section of the The wire may include an annular region or layer positioned proximate to the diffusion barrier (e.g., on one or both sides thereof, e.g., positioned between the composite filament and the diffusion barrier), wherein at least A portion may comprise, consist essentially of, or consist of a Nb-based superconducting phase (eg, Nb—Ti and/or Nb ₃ Sn). A portion of the annular region may comprise, consist essentially of, or consist of a Nb alloy or Nb--Ta alloy having a composition different from that of the diffusion barrier. The annular region may conform to and/or be in direct mechanical contact with the diffusion barrier.

one or more of the monofilaments, or additionally each core, containing Nb and one or more of Ti, Zr, Hf, Ta, Y, or La, an alloy, pseudoalloy, or It may comprise, consist essentially of, or consist of a mixture (eg, Nb-Ti). One or more of the monofilaments or even each core may comprise, consist essentially of, or consist of Nb ₃ Sn. The diffusion barrier may comprise, consist essentially of, or consist of Nb-3W or Nb-6W or Nb-12W. The diffusion barrier may additionally contain one or more alloying elements selected from the group consisting of Ru, Pt, Pd, Rh, Os, Ir, Mo, Re, or Si. The cross-sectional thickness and/or cross-sectional area of the diffusion barrier may be substantially constant along the thickness of the wire. One or more or even each of the composite filaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire). One or more or even each of the monofilaments may have a hexagonal cross-sectional shape (ie, in a cross-section perpendicular to the axial dimension of the wire).

The wire may include stabilizing elements disposed within the plurality of composite filaments or within or adjacent to the inner wire stabilizing matrix. The stabilizing element consists essentially of a Cu and/or Ta alloy containing 0.1% to 20% W or 0.2% to 12% W or 0.2% to 10% W may consist of or consist of At least part of the stabilizing element may be located substantially in the central core of the superconducting wire. The stabilizing element may occupy less than about 20% of the cross-section of the wire, less than about 15% of the cross-section of the wire, less than about 10% of the cross-section of the wire, or less than about 5% of the cross-section of the wire. The stabilizing element is greater than about 1% of the cross-section of the wire, greater than about 2% of the cross-section of the wire, greater than about 5% of the cross-section of the wire, greater than about 8% of the cross-section of the wire, or It may occupy more than about 10% of the cross-section of the wire.

These and other objects, along with the advantages and features of the invention disclosed herein, will become more apparent through reference to the following description, accompanying drawings, and claims. Furthermore, it should be understood that features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. As used herein, the terms "about" and "substantially" mean ±10%, in some embodiments ±5%. The term "consisting essentially of" means excluding other materials that contribute to the function, unless otherwise defined herein. Nonetheless, such other materials, collectively or individually, may be present in minor amounts. For example, a structure consisting essentially of multiple metals may generally be detectable via chemical analysis with only these metals, but do not contribute to function (and, for example, 5 ppm, 2 ppm, 1 ppm, 0.5 ppm, 5 ppm, 2 ppm, 0 . 5 ppm, or may be present in concentrations less than 0.1 ppm), and unintentional impurities only (which may be metallic or non-metallic). As used herein, "consisting essentially of at least one metal" refers to one metal or a mixture of two or more metals, but includes metals and non-metals such as oxygen, silicon, or nitrogen. It does not refer to compounds between metal elements or species (eg, metal nitrides, metal silicides, or metal oxides). Such non-metallic elements or species, for example, as impurities, collectively or individually, may be present in trace amounts.
The present invention provides, for example, the following items.
(Item 1)
A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
an outer wire matrix comprising Cu;
a diffusion barrier, said diffusion barrier being disposed within said wire matrix and comprising a Nb alloy containing 0.1%-20% W or a Nb--Ta alloy containing 0.1%-20% W a diffusion barrier comprising
a plurality of composite filaments, said plurality of composite filaments surrounded by said diffusion barrier and separated from said outer wire matrix by said diffusion barrier;
with
each composite filament comprising: (i) a plurality of monofilaments; and (ii) a cladding comprising Cu surrounding the plurality of monofilaments;
each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core;
the diffusion barrier occupies 1% to 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein the diffusion barrier extends through an axial dimension of the superconducting wire.
(Item 2)
The wire of item 1, further comprising an annular region comprising a Nb-based superconducting phase disposed between said composite filament and said diffusion barrier.
(Item 3)
_3. The wire of item 2, wherein the annular region comprises Nb3Sn.
(Item 4)
3. The wire of item 2, wherein the annular region conforms to and contacts the diffusion barrier.
(Item 5)
The wire of item 1, wherein the diffusion barrier occupies between 1% and 10% of the cross-sectional area of the superconducting wire.
(Item 6)
The wire of item 1, wherein the diffusion barrier occupies between 2% and 10% of the cross-sectional area of the superconducting wire.
(Item 7)
The wire of item 1, wherein the diffusion barrier occupies 3% to 10% of the cross-sectional area of the superconducting wire.
(Item 8)
The wire of item 1, wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La.
(Item 9)
The wire of item 1, _wherein the core of each monofilament comprises Nb3Sn.
(Item 10)
The wire of item 1, wherein the diffusion barrier comprises Nb-6W or Nb-Ta-3W.
(Item 11)
The wire of item 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. .
(Item 12)
The wire of item 1, wherein each of said composite filaments has a hexagonal cross-sectional shape.
(Item 13)
The wire of item 1, wherein each of said monofilaments has a hexagonal cross-sectional shape.
(Item 14)
Further comprising a stabilizing element disposed within said plurality of composite filaments and surrounded by said diffusion barrier, said stabilizing element comprising a Ta alloy containing 0.1%-20% W, 0.1%- The wire of item 1, comprising a Nb alloy containing 20% W or a Nb--Ta alloy containing 0.1% to 20% W.
(Item 15)
The wire of item 1, wherein the superconducting wire has a yield strength of at least 100 MPa.
(Item 16)
A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
a wire matrix containing Cu;
a plurality of composite filaments embedded within the wire matrix;
with
Each composite filament comprises: (i) a plurality of monofilaments; and (ii) a diffusion barrier, wherein the diffusion barrier is a Nb alloy containing 0.1%-20% W or a diffusion barrier comprising a Nb--Ta alloy containing W and extending through the axial dimension of said composite filaments and surrounding said plurality of monofilaments; and (iii) a cladding comprising Cu surrounding said diffusion barrier. wherein the diffusion barrier comprises a cladding separating the cladding from the plurality of monofilaments;
the diffusion barriers collectively occupy between 1% and 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core.
(Item 17)
17. The wire of item 16, further comprising an annular region disposed between said monofilament and a diffusion barrier of at least one of said composite filaments and comprising a Nb-based superconducting phase.
(Item 18)
18. The wire of item 17, _wherein the annular region comprises Nb3Sn.
(Item 19)
18. The wire of item 17, wherein the annular region conforms to and contacts the diffusion barrier.
(Item 20)
17. The wire of item 16, wherein the diffusion barriers collectively occupy between 1% and 10% of the cross-sectional area of the superconducting wire.
(Item 21)
17. The wire of item 16, wherein said diffusion barriers collectively occupy between 2% and 10% of the cross-sectional area of said superconducting wire.
(Item 22)
17. The wire of item 16, wherein said diffusion barriers collectively occupy between 3% and 10% of the cross-sectional area of said superconducting wire.
(Item 23)
17. The wire of item 16, wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La.
(Item 24)
17. The wire of item 16, _wherein the core of each monofilament comprises Nb3Sn.
(Item 25)
17. The wire of item 16, wherein the diffusion barrier comprises Nb-6W or Nb-Ta-3W.
(Item 26)
17. The wire of item 16, 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. .
(Item 27)
17. The wire of item 16, wherein the superconducting wire has a yield strength of at least 100 MPa.
(Item 28)
17. The wire of item 16, wherein each of said composite filaments has a hexagonal cross-sectional shape.
(Item 29)
17. The wire of item 16, wherein each of said monofilaments has a hexagonal cross-sectional shape.
(Item 30)
Further comprising a stabilizing element disposed within the plurality of composite filaments, the stabilizing element comprising a Ta alloy containing 0.1% to 20% W, a Ta alloy containing 0.1% to 20% W 17. A wire according to item 16, comprising a Nb alloy or a Nb--Ta alloy containing 0.1% to 20% W.
(Item 31)
A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
an inner wire stabilization matrix comprising Cu;
a diffusion barrier, said diffusion barrier being disposed around said wire stabilization matrix and made of Nb alloy containing 0.1% to 20% W or Nb containing 0.1% to 20% W; - a diffusion barrier comprising a Ta alloy;
a plurality of composite filaments, said plurality of composite filaments disposed about said diffusion barrier and separated from said wire stabilizing matrix by said diffusion barrier;
with
each composite filament comprising: (i) a plurality of monofilaments; and (ii) a cladding comprising Cu surrounding the plurality of monofilaments;
each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core;
the diffusion barrier occupies 1% to 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein the diffusion barrier extends through an axial dimension of the wire.
(Item 32)
32. The wire of item 31, further comprising an annular region disposed between said composite filament and said diffusion barrier and comprising a Nb-based superconducting phase.
(Item 33)
33. The wire of item 32, _wherein the annular region comprises Nb3Sn.
(Item 34)
33. The wire of item 32, wherein the annular region conforms to and contacts the diffusion barrier.
(Item 35)
32. The wire of item 31, wherein the diffusion barrier occupies between 1% and 10% of the cross-sectional area of the superconducting wire.
(Item 36)
32. The wire of item 31, wherein the diffusion barrier occupies between 2% and 10% of the cross-sectional area of the superconducting wire.
(Item 37)
32. The wire of item 31, wherein the diffusion barrier occupies between 3% and 10% of the cross-sectional area of the superconducting wire.
(Item 38)
32. The wire of item 31, wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La.
(Item 39)
32. The wire of item 31, _wherein the core of each monofilament comprises Nb3Sn.
(Item 40)
32. The wire of item 31, wherein the diffusion barrier comprises Nb-6W or Nb-Ta-3W.
(Item 41)
32. The wire of item 31, 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. .
(Item 42)
32. The wire of item 31, wherein the superconducting wire has a yield strength of at least 100 MPa.
(Item 43)
32. The wire of item 31, wherein each of said composite filaments has a hexagonal cross-sectional shape.
(Item 44)
32. The wire of item 31, wherein each of said monofilaments has a hexagonal cross-sectional shape.

In the drawings, like reference characters generally refer to identical parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings.

FIG. 1A is a schematic cross-sectional view of a tube utilized to form monofilaments, according to various embodiments of the present invention. FIG. 1B is a schematic cross-sectional view of a rod utilized to form monofilaments, according to various embodiments of the present invention; FIG. 1C is a schematic cross-sectional view of a monofilament utilized to form composite filaments, according to various embodiments of the present invention. FIG. 2A is a schematic cross-sectional view of a tube utilized to form composite filaments, according to various embodiments of the present invention. Figure 2B is a schematic cross-sectional view of a tube utilized to form a diffusion barrier within a composite filament, according to various embodiments of the present invention. FIG. 2C is a schematic cross-sectional view of a stack of monofilaments utilized to form composite filaments, according to various embodiments of the present invention. FIG. 2D is a schematic cross-sectional view of a composite filament at an early stage of processing, according to various embodiments of the present invention. FIG. 2E is a schematic cross-sectional view of a composite filament utilized to form superconducting wires, according to various embodiments of the present invention. FIG. 3A is a schematic cross-sectional view of a tube utilized to form a stabilizing element, according to various embodiments of the present invention; Figure 3B is a schematic cross-sectional view of a rod utilized to form a stabilizing element, according to various embodiments of the present invention; FIG. 3C is a schematic cross-sectional view of a stabilizing element utilized to form stabilized composite filaments and/or superconducting wires, according to various embodiments of the present invention. FIG. 3D is a schematic cross-sectional view of a composite filament incorporating stabilizing elements, according to various embodiments of the present invention; FIG. 4A is a schematic cross-sectional view of a tube utilized to form superconducting wires, according to various embodiments of the present invention. Figure 4B is a schematic cross-sectional view of a stack of composite filaments utilized to form a superconducting wire, according to various embodiments of the present invention. Figure 4C is a schematic cross-sectional view of a tube utilized to form a diffusion barrier within a superconducting wire, according to various embodiments of the present invention. Figure 4D is a schematic cross-sectional view of a superconducting wire at an early stage of processing, according to various embodiments of the present invention. FIG. 4E is a schematic cross-sectional view of a superconducting wire, according to various embodiments of the invention. FIG. 4F is a schematic cross-sectional view of a stabilized superconducting wire at an early stage of processing, according to various embodiments of the present invention. FIG. 4G is a schematic cross-sectional view of a stabilized superconducting wire, according to various embodiments of the present invention. FIG. 5 is a cross-sectional photomicrograph of a superconducting wire featuring a Cu internal stabilizer and a diffusion barrier disposed around the stabilizer, according to various embodiments of the present invention. FIG. 6 is a cross-sectional photomicrograph of a superconducting wire featuring a Cu outer matrix and a diffusion barrier positioned between the outer matrix and the wire filament, according to various embodiments of the present invention.

1A-1C depict the components of an exemplary monofilament 100 and their components. According to embodiments of the present invention, rod 105 is disposed within tube 110 comprising, consisting essentially of, or consisting of Cu or a Cu alloy (eg, bronze). The composition of rod 105 may be selected based on the particular metallic superconductor desired in the final wire. For example, rod 105 may comprise, consist essentially of, or consist of Nb, Ti, Nb--Ti, or alloys thereof. In other embodiments, rod 105 comprises, consists essentially of, or even consists of Nb alloyed with one or more of Ti, Zr, Hf, Ta, Y, or La. good. Such alloying elements, for example, in concentrations of 0.2% to 10% (eg, 0.2% to 5% or 0.5% to 1%), individually or collectively, rod 105 within (and thus within the core of the monofilament 100). In various embodiments, tube 110 (and/or any other tube described herein) may be formed by wrapping a metal sheet around rod 105 . In such embodiments, the ends of the sheets may overlap. Rod 105 coated with tube 110 may then be stretched to reduce its diameter by, for example, 0.5 inches to 1.5 inches. The coated rod may be stretched in multiple stages and may be heat treated during and/or after any or each of the stretching steps, eg, for strain relief. Once drawn, the coated rod may be drawn through a forming die to process the shaped monofilament 100 for efficient lamination with other monofilaments. For example, as shown in FIG. 1C, a hexagonal die may be utilized to form a monofilament 100 having a hexagonal cross-section. In other embodiments, the monofilaments may have other cross-sections, such as square, rectangular, triangular, and the like. As shown in FIG. 1C, monofilament 100 typically includes a single annular cladding disposed about and surrounding a single cylindrical core having a substantially uniform composition. , consisting essentially of, or consisting of. Thus, a region of superconducting wire according to embodiments of the present invention contains multiple claddings, with separate cylindrical cores corresponding to multiple "monofilaments" or a single "composite filament."

Once a monofilament 100 is processed, other monofilaments 100 may also be processed in the same manner, or one or more monofilaments 100 may be split into multiple pieces. A plurality of monofilaments may be stacked together to form at least a portion of the composite filament. 2A-2E depict various components and assemblies of composite filament 200. FIG. A plurality of monofilaments 100 may then be stacked together in an array that will then become at least part of the core of the composite filament 200, as shown in FIG. 2C. Although FIG. 2C depicts a stack of nineteen different monofilaments 100, embodiments of the invention may include more or less monofilaments 100. FIG. A laminated assembly of monofilaments 100 may be disposed within a tube 205 comprising, consisting essentially of, or consisting of Cu or a Cu alloy (eg, bronze). A tube 210 may be disposed within the tube 205 and around the stack of monofilaments 100, as shown in FIG. 2B. The main tube 210 becomes a diffusion barrier 215 in the final composite filament, impeding interdiffusion between the monofilament 100 and the material of the tube 205 becoming the outer matrix 220 of the resulting composite filament, or practically prevent. Thus, tube 210 may be Nb-W (eg Nb-12W or Nb-6W or Nb-3W) or Nb-Ta-W (eg Nb-Ta-12W or Nb-Ta-6W or Nb-Ta-3W ) or Nb--Ta alloys such as, consist essentially of, or consist of. Before and/or after monofilament 100 is placed within tube 205 and tube 210, monofilament 100, tube 205, and/or tube 210 are cleaned, for example, to remove surface oxides and/or other contaminants. , may be cleaned and/or etched (eg, via a cleaning agent comprising, consisting essentially of, or consisting of one or more acids).

Tube 210 may be fabricated via alloying pure Nb or Nb--Ta alloys with one or more other alloying elements placed within a diffusion barrier. For example, with respect to a diffusion barrier (and thus tube 210) comprising, consisting essentially of, or consisting of an alloy of Nb and W, Nb and W are melted as desired through processes such as electron beam melting and/or arc melting. may be alloyed together in an amount of Similarly, for a diffusion barrier (and thus tube 210) comprising, consisting essentially of, or consisting of an alloy of Nb, Ta, and W, Nb, Ta, and W are electron beam and/or arc melted. may be alloyed together in desired amounts via processes such as. The resulting material may be processed into a sheet, and the sheet may be formed into a tube by, for example, rolling, deep drawing, extrusion, pilger rolling, and the like.

As shown in FIG. 2D, tube 205 and tube 210 may be consolidated onto monofilament 100 by, for example, swaging, extrusion, and/or rolling. The coated laminated monofilament 100 may be annealed to promote bonding between the various monofilaments 100 in the laminated assembly. For example, the coated laminated monofilament may be annealed at a temperature of about 300° C. to about 500° C. (eg, about 400° C.) for a period of time of about 0.5 hours to about 3 hours (eg, about 1 hour). Advantageously, the presence of diffusion barrier 215 between monofilament 100 and outer matrix 220 substantially prevents diffusion between Cu of matrix 220 and monofilament 100, thereby reducing conductivity (e.g., prevent the formation of metallic phases with Cu and/or a lower conductivity than the material of matrix 220). Diffusion barrier 215 also exhibits its superior mechanical properties ( (eg, strength, yield strength, tensile strength, stiffness, Young's modulus, etc.) provide additional mechanical strength to the final wire.

The resulting assembly may be stretched one or more times to reduce its diameter, followed by a forming die to provide a composite filament 200 with a cross-sectional shape configured for efficient lamination. may be stretched through For example, as shown in FIG. 2E, a hexagonal die may be utilized to form a composite filament 200 having a hexagonal cross-section. In other embodiments, the composite filament 200 may have other cross-sections, such as square, rectangular, triangular, circular, non-circular, elliptical, and the like. In various embodiments, the cross-sectional size and/or shape of composite filament 200 after processing and shaping is similar to the cross-section of monofilament 100 utilized in the initial lamination assembly before being reduced in size (i.e., shown in FIG. 2C). Equal in size and/or shape. (Diffusion barrier 215 due to incorporation of tube 210 is depicted in FIGS. 2D and 2E as having a variable cross-sectional thickness, but in various embodiments of the invention diffusion barrier 215 is Having a substantially uniform cross-sectional thickness around its perimeter, the diffusion barrier 215 is tightly packed in cross-section around an annular ring (e.g., filament (or other structure) inside thereof), as shown in FIGS. A diffusion barrier having an annular cross-section, according to embodiments of the present invention, generally has a cylindrical shape extending along the axial dimension of the wire. )

Superconducting wires according to embodiments of the present invention may also incorporate stabilization elements that provide additional mechanical strength while not compromising the drawability and/or electrical performance of the wire. 3A-3C depict fabrication of stabilizing element 300 via methods similar to those detailed above with respect to monofilament 100. FIG. According to embodiments of the present invention, a rod 305 is positioned within a tube 310 comprising, consisting essentially of, or consisting of Cu or a Cu alloy. Rod 305 comprises, consists essentially of one or more metals having mechanical strengths (e.g., tensile strength, yield strength, etc.) greater than those of rod 105 utilized to fabricate monofilament 100; or may consist of For example, the rod 305 may be Ta or a Ta alloy (eg, a Ta—W alloy such as Ta-3W), Nb or a Nb alloy (eg, a Nb—W alloy such as Nb-12W, Nb-6W, or Nb-3W). , Nb--Ta alloys, Nb--Ta alloys containing one or more additional alloying elements such as Hf, Ti, Zr, Ta, V, Y, Mo, or W, or diffusion barriers such as may comprise, consist essentially of, or consist of any other material disclosed herein. In other embodiments, the rod 305 may comprise, consist essentially of, or consist of a Nb alloy having a mechanical strength substantially greater than that of pure Nb. For example, according to embodiments of the present invention, rods 305 (and thus stabilizing elements) may alloy Nb with one or more of Hf, Ti, Zr, Ta, V, Y, Mo, or W. may comprise, consist essentially of, or consist of; For example, according to embodiments of the present invention, the stabilizing element is about 10% Hf, about 0.7%-1.3% Ti, about 0.7% Zr, about 0.5% It may comprise, consist essentially of, or consist of a NbC103 alloy comprising Ta, about 0.5% W, and the balance Nb. In other embodiments, the stabilizing element may comprise, consist essentially of, or consist of NbB66 and/or NbB77 alloys.

Rod 305 coated with tube 310 may then be stretched to reduce its diameter by, for example, 0.5 inches to 1.5 inches. The coated rod may be stretched in multiple stages and may be heat treated during and/or after any or each of the stretching steps, eg, for strain relief. Once drawn, the coated rod may be drawn through a forming die to fabricate a shaped stabilizing element 300 for efficient lamination with monofilaments 100 and/or composite filaments 200. For example, as shown in Figure 3C, a hexagonal die may be utilized to form a stabilizing element 300 having a hexagonal cross-section. In other embodiments, stabilizing element 300 may have other cross-sections, such as square, rectangular, triangular, and the like. In various embodiments, stabilizing element 300 may have a cross-sectional size and/or shape that is substantially the same as the cross-sectional size and/or shape of monofilament 100 and/or composite filament 200 .

Once processed, one or more stabilizing elements 300 may be inserted into the stack of monofilaments 100 and the resulting assembly surrounded by diffusion barrier and matrix materials, stretched and optionally 3D, stabilized composite filaments 315 (e.g., described above with reference to FIGS. as described). In various embodiments of the invention, the composite filament may include a diffusion barrier between the stabilizing element 300 and the remaining monofilament 100 to impede or substantially prevent interdiffusion therebetween. In various embodiments, the stabilizing element 300 may be replaced or supplemented with an internal stabilizing matrix comprising, consisting essentially of, or consisting of, for example, Cu or a Cu alloy. A region may be separated from the monofilament 100 via one or more diffusion barriers. Although FIG. 3D depicts stabilizing element 300 as having a cross-sectional area that is substantially identical to that of one of monofilaments 100, in various embodiments of the invention stabilizing element 300 It has a cross-sectional area greater than that of the single monofilament 100 . For example, the cross-sectional area of the stabilizing element 300 may be at least 1.5 times, at least 2 times, at least 3 times, at least 4 times, at least 5 times, or at least 6 times the cross-sectional area of the monofilament 100 .

In embodiments of the invention incorporating stabilizing elements and diffusion barriers, the amount of wire cross-sectional area that imparts additional mechanical strength may be beneficially divided between the diffusion barriers and the stabilizing elements. That is, the greater the cross-sectional area of the wire occupied by the one or more stabilizing elements, the greater each diffusion barrier is thick enough to impede or substantially eliminate diffusion between the various portions of the wire. less cross-sectional area of the wire needs to be occupied by the diffusion barrier. Conversely, the use of diffusion barriers according to embodiments of the present invention may themselves collectively result in less breakage of the wire while still imparting the desired mechanical strength (and/or other mechanical properties) to the wire. Allows the use of more than one stabilizing element, occupying area. In various embodiments, the diffusion barriers may collectively occupy at least 1%, at least 2%, at least 3%, at least 4%, or at least 5% of the cross-sectional area of the wire. In various embodiments, the diffusion barriers collectively represent less than 15%, less than 12%, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, or 5% of the cross-sectional area of the wire. may occupy less than In embodiments of the invention featuring stabilizing elements, the stabilizing elements and the diffusion barrier collectively occupy less than 25%, less than 20%, less than 15%, or less than 10% of the cross-sectional area of the wire. may The stabilizing element itself may occupy less than 15% or less than 10% (eg, about 2% to about 8% or about 5% to about 15%) of the cross-sectional area of the wire. The stabilizing element may occupy at least 2%, at least 3%, at least 5%, or at least 8% of the cross-sectional area of the wire.

In addition to or instead of being incorporated within one or more composite filaments 200, 315, diffusion barriers according to embodiments of the present invention advantageously impede interdiffusion within the superconducting wire, or It may be disposed between the outer stabilizing matrix (and/or the inner stabilizing matrix and/or stabilizer proximate the center of the wire) and the composite filament so as to substantially prevent. That is, the superconducting wire and/or wire preform utilizes diffusion barriers disposed around composite filaments 200, stabilized composite filaments 315, and/or assemblies of composite filaments lacking their own diffusion barrier. and may be processed. 4A-4E depict various stages of fabrication of an exemplary superconducting wire 400. FIG. A plurality of composite filaments 405, each lacking their own internal diffusion barrier, may then be stacked together in an array that will become at least part of the core of superconducting wire 400, as shown in FIG. 4B. good. Each composite filament 405 may be fabricated, for example, similar to composite filament 200 detailed above, but without incorporation of diffusion barrier 215 resulting from use of tube 210 during fabrication. In other embodiments, the stack of composite filaments may comprise or consist of composite filaments 200 , composite filaments 315 , and/or mixtures thereof, with or without composite filaments 405 . Although FIG. 4B depicts a stack of 18 different composite filaments 405, embodiments of the invention may include more or fewer composite filaments.

A laminated assembly of composite filaments may be disposed within a tube 410 comprising, consisting essentially of, or consisting of Cu or a Cu alloy. Additionally, as shown in FIG. 4C, tube 210 may be disposed around and within tube 410 of the laminated assembly of composite filaments, thus forming a diffusion barrier in the final wire. good too. Before and/or after the composite filaments are placed within tubes 510 and 210, the composite filaments, tube 210, and/or tube 410 may be cleaned, for example, to remove surface oxides and/or other contaminants. , may be cleaned and/or etched (eg, via a cleaning agent comprising, consisting essentially of, or consisting of one or more acids). Tube 410 and tube 210 may be consolidated onto the composite filament by, for example, swaging, extrusion, and/or rolling, and tube 210 may become a diffusion barrier 415, as shown in FIG. 4D. , tube 410 may become outer matrix 420 . The coated laminated composite filaments may be annealed to promote bonding between the various composite filaments in the laminated assembly. For example, the coating stack may be annealed at a temperature of about 300° C. to about 500° C. (eg, about 400° C.) for a time of about 0.5 hours to about 3 hours (eg, about 1 hour). Advantageously, the presence of the diffusion barrier 415 between the composite filaments 405 and the outer matrix 420 substantially prevents diffusion between the Cu of the matrix 420 and the composite filaments 405, thereby resulting in low conductivity ( For example, it prevents the formation of metallic phases with Cu and/or a lower conductivity than the material of matrix 420). The resulting assembly may be stretched one or more times to reduce its diameter, as shown in FIG. 4E. Before or after stretching, superconducting wire 400 may be annealed, for example, to relieve residual stress and/or promote recrystallization therein.

A similar methodology is utilized to fabricate a stabilized superconductor wire 425 that incorporates one or more diffusion barriers 415 and one or more stabilization elements 300, as shown in FIGS. 4F and 4G. may For example, an assembly of laminated composite filaments may each define one or more voids therein that are sized and shaped to accommodate one or more stabilizing elements 300 . Before or after the composite filaments are placed in tube 410 and tube 210, one or more stabilizing elements 300 may be placed inside each of the voids, as shown in FIG. 4F. The resulting assembly may have its diameter reduced, for example by stretching and/or extrusion, as shown in FIG. 4G. In various embodiments, the diffusion barrier is, in particular, the stabilizing element comprising, consisting essentially of, or consisting of Cu, in embodiments between the stabilizing element 300 and the filament within a wire or wire preform. may be placed in For example, a tube of desired diffusion barrier material may be placed around the stabilizing element when the wire preform assembly is assembled, and the entire assembly may be stretched to the desired wire dimensions. FIGS. 4F and 4G depict a superconducting wire 425 having a single stabilizing element 300 substantially centrally located in the laminated assembly of composite filaments, but according to embodiments of the present invention, one or more The stabilizing element 300 may be placed elsewhere in the laminate assembly in addition to or instead of the centrally located stabilizing element 300 . Although FIGS. 4F and 4G depict stabilizing element 300 as having a cross-sectional area that is substantially identical to that of one of composite filaments 405, in various embodiments of the invention stabilizing element 300 has a cross-sectional area greater than that of single composite filament 405 . For example, the cross-sectional area of stabilizing element 300 may be at least 1.5 times, at least 2 times, at least 3 times, at least 4 times, at least 5 times, or at least 6 times the cross-sectional area of composite filament 405 .

In various embodiments, the superconducting wires 400, 425 lack diffusion barriers 415 inside thereof, and thus the tube 210 is not utilized in its formation, but rather one or more of the individual composite filaments. A medium diffusion barrier 215 is utilized to impede or substantially prevent interdiffusion. In other embodiments, as shown in FIGS. 4D-4G, individual composite filaments 405 may lack diffusion barriers within them, and diffusion barriers 415 are present within superconducting wires 400, 425. FIG. In such embodiments, the tubes 110 and/or 205 advantageously have Sn on their interior that reacts with the Nb of the filaments during subsequent heat treatment to form a superconducting phase (e.g. _, Nb3Sn). may be incorporated into In other embodiments, diffusion barriers 415 are present within the individual composite filaments in addition to diffusion barriers 215 .

In various embodiments, superconducting wire 400, superconducting wire 425, composite filament 4015, composite filament 200, and/or stabilized composite filament 315 are used for diameter reduction and/or for their components. It may be mechanically treated prior to the wire drawing step to promote bonding between them. For example, superconducting wire 400, superconducting wire 425, composite filament 4015, composite filament 200, and/or stabilized composite filament 315 may be extruded, swaged, and/or rolled prior to the final drawing step. good too. In various embodiments, superconducting wire 400, superconducting wire 425, composite filament 4015, composite filament 200, and/or stabilized composite filament 315 are each subjected to a plurality of different drawing steps for strain relaxation. It may be heat treated in between and/or after. For example, during and/or after one or more of the drawing steps, superconducting wire 400, superconducting wire 425, composite filament 4015, composite filament 200, and/or stabilized composite filament 315 are subjected to, for example, It may be annealed at a temperature of about 360° C. to about 420° C. for a period of about 20 hours to about 40 hours.

In various embodiments of the present invention, superconducting wire 400 or superconducting wire 425 may be cooled below the critical temperature of the filament inside it and utilized to conduct electrical current. In some embodiments, multiple superconducting wires 400 and/or superconducting wires 425 are coiled together to form a single superconducting cable.

Although some superconducting wires 400, 425 (eg, those incorporating Nb—Ti containing filaments) may be utilized directly in superconducting applications, fabrication processes for various other superconducting wires 400, 425 may incorporate one or more steps to incorporate a portion of the superconducting phase. For example, the Nb ₃ Sn superconducting phase, once formed, is typically brittle and may not be further stretched or otherwise mechanically deformed without damage. Accordingly, embodiments of the present invention may be utilized to fabricate superconducting wires 400, 425 that incorporate Nb and Sn separate from each other, once the wires 400, 425 are mostly or completely fabricated. , the wires 400, 425 may be annealed to interdiffuse Nb and Sn and form a superconducting Nb ₃ Sn phase inside thereof. For example, the drawn wire may be annealed at a temperature of about 600° C. to about 700° C. for a period of time of about 30 hours to about 200 hours, for example. In various embodiments, one or more of the Cu-based tubes 110, 205, or 310 may incorporate Sn inside thereof, for example, one or more of the tubes may be Cu- It may comprise, consist essentially of, or consist of a Sn alloy (eg, containing 13-15% Sn). Such materials are ductile and allow processing of various filaments and wires as detailed herein. The wires 400, 425 may then be annealed, resulting in interdiffusion and formation of a superconducting Nb ₃ Sn phase at least at the interface between the Nb and Cu—Sn.

In other embodiments, pure Sn or Sn alloys (eg, Sn alloys with Cu or magnesium (Mg)) are used to form composite filaments 200, stabilized composite filaments 315, and/or wires 400, 425. The composite filament 200 as detailed herein, stabilized composite After formation of filaments ₃₁₅ and/or wires 400, 425, an annealing step may be performed to form the superconducting Nb3Sn phase.

In various embodiments, at least Nb within a portion of one or more diffusion barriers within the wire reacts as described above to form a superconducting phase, and this reacted portion of the diffusion barrier thus: During operation, it can contribute to the superconducting conductivity of the wire. For example, the inner or outer portion of the diffusion barrier may react with, for example, Sn or a Sn alloy to form a superconducting phase substantially the same or similar to that formed from filaments of wire. In such embodiments, the thickness of the diffusion barrier is typically large enough so that the entire diffusion barrier does not react and form a superconducting phase. Thus, at least a portion of the diffusion barrier remains unreacted and contributes to resistance to interdiffusion and mechanical strength to the wire, as described herein. In various embodiments, the diffusion barrier comprises one or more annular layers comprising, consisting essentially of, or consisting of Nb and a Nb alloy or Nb—Ta alloy, as detailed herein. It may be a multi-layer structure comprising, consisting essentially of, or containing one or more annular layers. The alloy layer may provide most of the diffusion resistance, while at least part of the Nb layer may react (e.g. with the surrounding Sn in the Cu matrix) during heat treatment and become part of the superconducting phase. . For example, the diffusion barrier may comprise, consist essentially of, or consist of an alloy layer sandwiched between two different Nb layers. In another embodiment, the inner Nb layer may be surrounded by the outer alloy layer or vice versa.

FIG. 5 is a cross-sectional view of a superconducting wire 500 incorporating a diffusion barrier, according to an embodiment of the invention. As shown, a diffusion barrier 510 is placed between the Cu-stabilized core 520 of wire 500 and an outer bronze matrix 530 containing Nb-based filaments 540 . FIG. 6 is a cross-sectional view of another superconducting wire 600 incorporating a diffusion barrier according to embodiments of the invention. As shown, a diffusion barrier 610 is positioned between an inner Sb—Cu—Nb based filament 620 and an outer Cu stabilizer 630 in the core of wire 600 .

(Example)
A series of experiments were performed to evaluate Nb—W alloy materials in terms of their processability in heavily drawn superconducting wires and thus their suitability for use as diffusion barriers. Material processing began with the melting of three different Nb--W alloys in a button furnace. Three different samples had W of 2.9 weight percent, W of 5.7 weight percent, and W of 11.4 weight percent, and all three buttons weighed 680.4 grams after processing. was the weight of A center section was extracted from each of the buttons via cutting on a bandsaw and deburring with a file. The thickness of each section was measured and used as the starting thickness for a series of rolling experiments. Samples were rolled on a rolling mill at a nominal 5% through schedule. Periodically, during rolling, the thickness of the samples was measured and a portion of each sample was extracted for hardness testing. No intermediate anneal or other treatment was performed on the samples. The results of the rolling experiments are shown in Table 1 below, which reports thickness and corresponding reduction in area (ROA).

The hardness of the rolled samples was subsequently tested using a Vickers hardness test using a Vickers test force (HV) of 0.5 kg on a 401 MVD Knoop/Vickers Microindentation Tester available from Wilson Wolpert Instruments (Aachen, Germany). evaluated using. Each sample was ground and mounted prior to hardness testing. Three measurements were made according to ASTM E384 standard (ASTM International, West Conshohocken, PA), the entire disclosure of which is incorporated herein by reference, using a 136° pyramidal diamond indenter. was performed on each sample and the mean and standard deviation were calculated. The hardness test results are reported in Tables 2-4 below.

As shown on the data table above, all three of the samples tested exhibited good ductility when processed via cold working to ROA values greater than 70%. The measured behavior is similar to that exhibited by pure niobium samples, demonstrating the suitability of these sample alloys for use as diffusion barriers in state-of-the-art superconducting wires. The hardness of each alloy increased slightly as a function of increased W content and increased ROA, as expected, but all samples exhibited good ductility in all conditions tested. . None of the samples were cracked or otherwise damaged by the cold working utilized in the test procedure and all samples deformed very uniformly during testing.

The terms and expressions employed herein are used as terms of description and not of limitation and use of such terms and expressions does not imply any equivalents of the features shown or described, or portions thereof. There is no intention to exclude objects. Additionally, while certain embodiments of the invention have been described, it will be appreciated by those skilled in the art that other embodiments incorporating the concepts disclosed herein may also be used without departing from the spirit and scope of the invention. will be clear to Accordingly, the described embodiments are to be considered in all respects only as illustrative and not restrictive.

Claims (41)

A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
an outer wire matrix comprising Cu;
a diffusion barrier, said diffusion barrier disposed within said outer wire matrix and comprising 2.5 % to 12 % W and the group consisting of Ru, Pt, Pd, Rh, Os, Ir, Re, or Si a diffusion barrier comprising a Nb alloy containing one or more alloying elements selected from
a plurality of composite filaments, said plurality of composite filaments surrounded by said diffusion barrier and separated from said outer wire matrix by said diffusion barrier;
each composite filament comprising: (i) a plurality of monofilaments; and (ii) a cladding comprising Cu surrounding the plurality of monofilaments;
each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core;
the diffusion barrier occupies 1% to 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein the diffusion barrier extends through an axial dimension of the superconducting wire. 2. The superconducting wire of claim 1, further comprising an annular region comprising a Nb-based superconducting phase disposed between said composite filament and said diffusion barrier. _3. The superconducting wire of claim 2, wherein said annular region comprises Nb3Sn. 3. The superconducting wire of claim 2, wherein said annular region conforms to and contacts said diffusion barrier . The superconducting wire of claim 1, wherein the diffusion barrier occupies 1% to 10% of the cross-sectional area of the superconducting wire. The superconducting wire of claim 1, wherein the diffusion barrier occupies 2% to 10% of the cross-sectional area of the superconducting wire. The superconducting wire of claim 1, wherein the diffusion barrier occupies 3% to 10% of the cross-sectional area of the superconducting wire. 2. The superconducting 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. A superconducting wire according to claim 1, wherein the core of _each monofilament comprises Nb3Sn. The superconducting wire of claim 1, wherein each of said composite filaments has a hexagonal cross-sectional shape. The superconducting wire of claim 1, wherein each of said monofilaments has a hexagonal cross-sectional shape. Further comprising a stabilizing element disposed within said plurality of composite filaments and surrounded by said diffusion barrier, said stabilizing element comprising a Ta alloy containing 0.1%-20% W, 0.1%- 2. The superconducting wire of claim 1, comprising a Nb alloy containing 20% W or a Nb--Ta alloy containing 0.1% to 20% W. 2. The superconducting wire of claim 1, wherein the superconducting wire has a yield strength of at least 100 MPa. A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
a wire matrix containing Cu;
a plurality of composite filaments embedded within the wire matrix;
Each composite filament comprises: (i) a plurality of monofilaments; and (ii) a diffusion barrier, said diffusion barrier comprising 2.5 % to 12 % W , Ru, Pt, Pd, Rh, Os, Ir, a diffusion barrier comprising a Nb alloy containing one or more alloying elements selected from the group consisting of Re, or Si, extending through the axial dimension of the composite filaments and surrounding the plurality of monofilaments; , (iii) a cladding comprising Cu surrounding said diffusion barrier, said diffusion barrier separating said cladding from said plurality of monofilaments;
the diffusion barriers collectively occupy between 1% and 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core. 15. The superconducting wire of claim 14 , further comprising an annular region disposed between the monofilament and the diffusion barrier of at least one of the composite filaments and comprising a Nb-based superconducting phase. 16. The superconducting wire of claim 15 _, wherein said annular region comprises Nb3Sn. 16. The superconducting wire of claim 15 , wherein the annular region conforms to and contacts the diffusion barrier . 15. The superconducting wire of claim 14 , wherein said diffusion barriers collectively occupy between 1% and 10% of the cross-sectional area of said superconducting wire. 15. The superconducting wire of claim 14 , wherein said diffusion barriers collectively occupy between 2% and 10% of the cross-sectional area of said superconducting wire. 15. The superconducting wire of claim 14 , wherein said diffusion barriers collectively occupy between 3% and 10% of the cross-sectional area of said superconducting wire. 15. The superconducting wire of claim 14 , wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La. 15. The superconducting wire of claim 14 , wherein the core of _each monofilament comprises Nb3Sn. 15. The superconducting wire of claim 14 , wherein the superconducting wire has a yield strength of at least 100 MPa. 15. The superconducting wire of claim 14 , wherein each of said composite filaments has a hexagonal cross-sectional shape. 15. The superconducting wire of claim 14 , wherein each of said monofilaments has a hexagonal cross-sectional shape. Further comprising a stabilizing element disposed within the plurality of composite filaments, the stabilizing element comprising a Ta alloy containing 0.1% to 20% W, a Ta alloy containing 0.1% to 20% W 15. A superconducting wire as claimed in claim 14 , comprising a Nb alloy or a Nb--Ta alloy containing 0.1% to 20% W. A superconducting wire possessing diffusion resistance and mechanical strength, said superconducting wire comprising:
an inner wire stabilization matrix comprising Cu;
a diffusion barrier, said diffusion barrier disposed around said inner wire stabilization matrix and comprising 2.5 % to 12 % W and Ru, Pt, Pd, Rh, Os, Ir, Re, or Si a diffusion barrier comprising a Nb alloy containing one or more alloying elements selected from the group consisting of
a plurality of composite filaments, said plurality of composite filaments disposed about said diffusion barrier and separated from said inner wire stabilizing matrix by said diffusion barrier;
each composite filament comprising: (i) a plurality of monofilaments; and (ii) a cladding comprising Cu surrounding the plurality of monofilaments;
each monofilament comprises a core comprising Nb and a cladding comprising Cu surrounding said core;
the diffusion barrier occupies 1% to 20% of the cross-sectional area of the superconducting wire;
A superconducting wire, wherein the diffusion barrier extends through an axial dimension of the superconducting wire. 28. The superconducting wire of claim 27 , further comprising an annular region disposed between said composite filament and said diffusion barrier and comprising a Nb-based superconducting phase. 29. The superconducting wire of claim 28 _, wherein said annular region comprises Nb3Sn. 29. The superconducting wire of claim 28 , wherein said annular region conforms to and contacts said diffusion barrier . 28. The superconducting wire of claim 27 , wherein the diffusion barrier occupies between 1% and 10% of the cross-sectional area of the superconducting wire. 28. The superconducting wire of claim 27 , wherein the diffusion barrier occupies between 2% and 10% of the cross-sectional area of the superconducting wire. 28. The superconducting wire of claim 27 , wherein the diffusion barrier occupies between 3% and 10% of the cross-sectional area of the superconducting wire. 28. The superconducting wire of claim 27 , wherein the core of each monofilament comprises Nb alloyed with at least one of Ti, Zr, Hf, Ta, Y, or La. 28. A superconducting wire according to claim 27 , wherein the core of _each monofilament comprises Nb3Sn. 28. The superconducting wire of claim 27 , wherein the superconducting wire has a yield strength of at least 100 MPa. 28. The superconducting wire of claim 27 , wherein each of said composite filaments has a hexagonal cross-sectional shape. 28. The superconducting wire of claim 27 , wherein each of said monofilaments has a hexagonal cross-sectional shape. The superconducting wire of claim 1, wherein said diffusion barrier comprises Nb-3W. 15. The superconducting wire of claim 14, wherein said diffusion barrier comprises Nb-3W. 28. The superconducting wire of claim 27, wherein said diffusion barrier comprises Nb-3W.

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