Manufacturing of superconducting wire

Abstract

Provided herein is a second generation high temperature superconducting wire that prevents mechanical damage to the wire edge caused by cutting. The structure of a 2G HTS wire according to an embodiment of the present invention can prevent mechanical damage to the wire edge. This can be achieved by forming stripes at or near the edge of the wire, where the buffer layer and the superconducting layer are removed to prevent any extension of edge cracks from damaging the HTS wire.

Description

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 807,133, filed on February 18, 2019 by Fukushima et al., entitled “Manufacturing of Superconducting Wire,” which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention relates to a high temperature superconducting wire, and more particularly to a structure and a manufacturing method for reducing damage caused by mechanical cutting. Background Art

[0003] The potential of high temperature superconductors (HTS) to efficiently transmit, generate, convert, use and store electrical energy has been recognized. In particular, more efficient power systems rely on more efficient wire technology. Past technological advances have enabled brittle HTS materials to be formed into wires thousands of meters long, which can carry about 200 times more current than conventional copper and aluminum conductors of the same physical size. The term "wire" as used herein refers to any elongated structure, including ribbons or strips.

[0004] Recent research on HTS materials offers the potential for economically viable use of such materials in the power industry, including applications in power generation, transmission, distribution, and storage. The use of HTS devices in the power industry would significantly reduce the size (i.e., footprint) of power equipment, reduce environmental impact, improve safety, and increase capacity compared to conventional technologies.

[0005] Two generations of HTS wires have been developed. The first generation of HTS (hereinafter referred to as "1G") wires include the use of BSCCO high-Tc superconductors, which are usually embedded in a precious metal matrix (such as Ag). Unrestrictedly, 1G wires are manufactured by thermomechanical processing, in which superconducting powder ++8 / 96CF5er is filled into a silver billet, which is stretched, rolled and heat treated to form the wire. The disadvantages of 1G wires are high material cost (such as Ag), complex processing operations, and generally poor critical current performance in high magnetic fields at high temperatures, which limits the length of the wire.

[0006] Recently, rare earth-based HTS materials (RE) BCO have been used in second-generation (hereinafter referred to as "2G") HTS wires. Rare earth elements include but are not limited to yttrium, samarium and gadolinium. The processing of 2G HTS wires generally involves thin film deposition of multilayer stacks on nickel alloy tapes. In order to obtain a high critical current, that is, the maximum current of the superconductor, the superconducting film is epitaxially grown in a quasi-single crystal form on an oxide buffer layer, which can provide a quasi-single crystal template even when deposited on a polycrystalline metal substrate. In some cases, 2G HTS tapes use conductors coated with YBCO. 2G conductors (or wires) offer performance advantages (operating at higher temperatures and background magnetic fields) and cost advantages.

[0007] In recent years, the HTS industry has focused on increasing current carrying capacity, improving wire production capacity, and reducing manufacturing costs. The goal is to produce commercially viable high-performance HTS wire that can be used in the power industry to manufacture equipment such as grid transmission cables and transformers.

[0008] As described in more detail below, a method for manufacturing 2G HTS wire involves a combination of electroplating, sputtering and metal organic chemical vapor deposition (MOCVD) steps to deposit a buffer layer, a superconducting layer and one or more covering layers on a substrate. It is usually more cost-effective to manufacture HTS wires with relatively large widths (e.g., from 12 mm to 10 cm or more) as base conductors. The wire can then be cut along its length to produce multiple wires with a smaller width. The desired width of the wire depends on the specific application. For HTS cables, the width is usually preferably 4 mm, while for other applications, such as HTS transformer low-voltage windings, wide strips may be required to accommodate high operating currents. The manufactured HTS wire with a larger width can usually be cut to the desired width before the final application of the covering layer or stabilizer. For example, a 12 mm HTS wire can be cut into two 6 mm HTS wires, three 4 mm HTS wires, four 3 mm HTS wires, six 2 mm HTS wires, or even one 8 mm HTS wire and one 4 mm HTS wire.

[0009] Various known methods can be used to achieve the slitting of HTS base conductors, including using a laser slitter or a mechanical slitter that slitter the HTS base conductor with a metal blade. Mechanical slitting machines have lower costs and higher production capacity than many other types of slitting machines. Unfortunately, however, the mechanical slitting process can cause damage to the relatively brittle superconducting and buffer layers. This damage can lead to the formation of cracks, which can propagate, degrading the mechanical and electrical properties of the wire, and ultimately leading to delamination of the wire and deterioration of the critical current (Ic).

[0010] An improvement is needed to reduce or eliminate damage to superconducting wire caused by mechanical cutting. SUMMARY OF THE INVENTION

[0012] According to an embodiment of the present invention, a second generation high temperature superconducting wire is provided, which prevents mechanical damage to the wire edge caused by cutting. The structure of the 2GHTS wire according to an embodiment of the present invention can prevent mechanical damage to the wire edge. This can be achieved by forming stripes at or near the edge of the wire, where the buffer layer and the superconducting layer are removed to prevent any extension of edge cracks from damaging the HTS wire.

[0013] The features and technical advantages of the present invention have been summarized quite extensively above so that the following detailed description of the present invention can be better understood. Additional features and advantages of the present invention will be described below. It should be understood by those skilled in the art that the disclosed concepts and specific embodiments can be easily used as a basis for modifying or designing other structures to achieve the same purpose of the present invention. It should also be recognized by those skilled in the art that such equivalent structures do not deviate from the spirit and scope of the present invention set forth in the appended claims.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a more thorough understanding of the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0016] Figure 1 Shown is an HTS conductive tape according to one embodiment of the present invention.

[0017] Figure 2 Shown is a cross section of an HTS tape according to another embodiment of the present invention, wherein the entire superconducting tape is encapsulated by an electroplated stabilizer.

[0018] Figure 3 The figure shows a schematic diagram of the process of cutting the base conductor of a 2G HTS wire using a mechanical cutting machine.

[0019] Figure 4 Shown is a photomicrograph of a magnified image of the edge of an HTS wire after cutting.

[0020] Figure 5A Shown is a cross section of a multi-layer HTS wire according to one embodiment of the present invention.

[0021] Figure 5B Shown is a top view of a multi-layer HTS wire according to one embodiment of the present invention.

[0022] Figure 6 Shown is a cross section of one of the two narrower HTS wires produced by the cut shown in FIG. 5 .

[0023] Figure 7 Shown is a diagram of a further cover layer after application according to one embodiment of the present invention. Figure 7 cross section.

[0024] Figure 8 Shown is a micrograph of an HTS wire according to one embodiment of the present invention, in which striations have been formed prior to slicing.

[0025] Fig. 9 Another embodiment of the present invention is shown, in which four separation stripes are formed so that the base HTS wire will be separated into three narrower final HTS wires.

[0026] Fig.10 Another embodiment of the invention is shown in which a single stripe is formed (for each desired cut) and then the HTS wire is cut within the stripe.

[0027] Fig.11 Shown is based on Fig.10 A cross section of a single multilayer HTS wire after cutting.

[0028] Figures 12A-12C Shown are different stripe shapes formed according to embodiments of the present invention.

[0029] Fig.13 Shown is a schematic diagram of an apparatus for cutting stripes and mechanically severing a base HTS wire according to one embodiment.

[0030] The accompanying drawings are not drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures is represented by the same numeral. For clarity, not every component may be labeled in every drawing. DETAILED DESCRIPTION

[0031] Embodiments of the present invention include second generation high temperature superconducting wires that prevent mechanical damage to the wire edges caused by cutting. The structure of the 2G HTS wire according to an embodiment of the present invention can prevent mechanical damage to the wire edges. This can be achieved by forming stripes at or near the edges of the wire, where the buffer layer and superconducting layer are removed to prevent any extension of edge cracks from damaging the HTS wire.

[0032] Figure 1 Schematic diagram of a typical 2G HTS wire 100 is shown. The wire includes a substrate 110, a buffer layer 112 (which may include multiple buffer layers) covering the substrate 110, an HTS layer 114, followed by a cap layer 116 (usually a noble metal layer) and a stabilizer layer 118 (usually a non-noble metal). Figure 1 In the illustrated embodiment, the buffer layer 112 , the HTS layer 114 , the cap layer 116 , and the stabilizer layer 118 are collectively referred to as a superconducting region, which is disposed along one major surface of the substrate 110 as shown.

[0033] The substrate 110 is typically a ribbon structure having a high aspect ratio. For example, the width of the ribbon is typically on the order of about 2-12 mm, and the length of the ribbon is typically at least about 100 meters, most typically greater than about 500 meters. Thus, the aspect ratio of the substrate can be quite high, on the order of not less than 10 3 , or even not less than 10 4 Some embodiments are longer, with an aspect ratio of 10 5As used herein, the term "aspect ratio" is used to refer to the ratio of the length of a substrate or a tape relative to the next longest dimension, ie, the width of the substrate or tape.

[0034] In one embodiment, the substrate is treated to have the desired surface properties for the subsequent deposition of the constituent layers of the HTS tape. For example, the surface can be lightly polished to a desired flatness and surface roughness. In addition, as is understood in the art, the substrate can be treated to be bi-directionally textured, such as by the known RABiTS (rolling assisted bi-directional textured substrate) technique.

[0035] Next, let's look at the buffer layer 111, which can be a single layer or, more commonly, a plurality of films. Most typically, the buffer layer comprises a bidirectional textured film having a crystal texture generally aligned along the crystal axes in and out of the plane of the film. This bidirectional texture can be accomplished by IBAD. As is understood in the art, IBAD is an abbreviation for ion beam assisted deposition, which technique can be advantageously used to form a buffer layer of appropriate texture for subsequent formation of a HTS layer of desired crystallographic orientation with excellent superconducting properties. Magnesium oxide is a typical material for IBAD films, which can be on the order of 50-500 angstroms, for example, 50-200 angstroms. Typically, an IBAD film has a rock salt-like crystal structure, as defined and described in U.S. Patent No. 6,190,752, which is incorporated herein by reference in its entirety.

[0036] The buffer layer may include an additional film, such as a barrier film placed between the IBAD film and the substrate and in direct contact therewith. In this regard, the barrier film may advantageously be formed of an oxide (such as yttrium oxide) and serve to isolate the substrate from the IBAD film. The barrier film may also be formed of a non-oxide (such as silicon nitride and silicon carbide). Suitable techniques for depositing the barrier film include chemical vapor deposition and physical vapor deposition, including sputtering. The typical thickness of the barrier film may be in the range of about 100-200 angstroms. In addition, the buffer layer may also include an epitaxial growth film formed on the IBAD film. In this case, the epitaxial growth film may effectively increase the thickness of the IBAD film, and may desirably be made primarily of the same material as used for the IBAD layer, such as MgO.

[0037] In embodiments utilizing MgO-based IBAD films and / or epitaxial films, there is a lattice mismatch between the MgO material and the superconducting layer material. Therefore, the buffer layer may further include another buffer film, which is particularly intended to reduce the lattice constant mismatch between the HTS layer and the IBAD film and / or epitaxial film thereunder. The buffer film may be formed of materials such as YSZ (yttria-stabilized zirconium oxide), strontium ruthenate, lanthanum manganate, and generally perovskite-structured ceramic materials. The buffer film may be deposited by various physical vapor deposition techniques.

[0038] Although the foregoing description is mainly centered around achieving bidirectional textured films in a buffer stack (layer) by a texturing process such as IBAD, alternatively, the substrate surface itself can be bidirectionally textured. In this case, the buffer layer is typically epitaxially grown on the textured substrate, thereby maintaining a bidirectional texture in the buffer layer. A process for forming a bidirectional textured substrate is a RABiTS (rolling assisted bidirectional textured substrate) process known in the art, which is generally understood in the art.

[0039] The high temperature superconducting (HTS) layer 112 is generally selected from any high temperature superconducting material that exhibits superconducting properties above the temperature of liquid nitrogen (77° K). Such materials may include, for example, YBa2Cu3O 7-x 、Bi2Sr2Ca2Cu3O 10+y 、Ti2Ba2Ca2Cu3O 10+y and HgBa2Ca2Cu3O 8+y One class of materials includes REBa2Cu3O 7-x , wherein RE is a rare earth element. In the above, YBa2Cu3O 7-x , also commonly referred to as YBCO. The HTS layer 112 can be formed by any of a variety of techniques including thick film and thin film formation techniques. Preferably, a thin film physical vapor deposition technique such as pulsed laser deposition (PLD) can be used for high deposition rates, or a chemical vapor deposition technique can be used for low cost and large surface area processing. Typically, the thickness of the HTS layer is on the order of about 1 to about 30 microns, most typically about 2 to about 20 microns, such as about 2 to about 10 microns, so as to obtain the desired ampere rating corresponding to the HTS layer 112.

[0040] The capping layer 114 and the stabilizer layer 116 are generally used for electrical stability, that is, they help prevent the HTS from burning out in actual use. More specifically, in the case of cooling failure or exceeding the critical current density, layers 114 and 116 help to keep the charge flowing along the HTS conductor, and the HTS layer leaves the superconducting state and becomes resistive. The capping layer 114 generally uses a noble metal to prevent unwanted interactions between one or more stabilizer layers and the HTS layer 112. Noble metals generally include gold, silver, platinum and palladium. In view of its cost and general accessibility, silver is generally used. The capping layer 114 is generally made thick enough to prevent components from undesirably diffusing from the stabilizer layer 116 into the HTS layer 112, but due to cost reasons (raw materials and processing costs), it is generally made thinner. The typical thickness of the capping layer 114 is in the range of about 0.1-about 10.0 microns, for example, 0.5-about 5.0 microns. Various techniques can be used to deposit the capping layer 114, including physical vapor deposition, such as DC magnetron sputtering.

[0041] According to the implementation, a stabilizer layer 116 is introduced to cover the superconducting layer 112, and in particular, Figure 1 In the illustrated embodiment, the cap layer 114 is covered and in direct contact therewith. The stabilizer layer 116 acts as a protective / shunt layer to enhance stability against harsh environmental conditions and superconducting quenching. This layer is typically dense, thermally and electrically conductive, and acts as a bypass current in the event of a superconducting layer failure. Typically, such a layer is formed by laminating a preformed copper tape onto a superconducting tape using an intermediate bonding material such as a solder or flux. Other techniques mainly revolve around physical vapor deposition, typically sputtering. However, this application technology is very costly and is not particularly economically feasible for large-scale production operations. The stabilizer layer 116 can be formed by electroplating. According to this technology, electroplating can quickly form a thick layer of material on a superconducting tape, and it is a relatively low-cost process that can effectively produce a dense thermally and electrically conductive metal layer. The stabilizer layer can be deposited without the use or reliance on an intermediate bonding layer (e.g., a solder layer (including a flux) having a melting point of less than about 300°C).

[0042] Electroplating (also known as electrodeposition) is usually performed by immersing the superconducting tape in a solution containing the metal ions to be deposited. The surface of the tape is connected to an external power source and an electric current is passed through the surface into the solution, causing the metal ions (M z- ) and electron (e - ) reacts to form metal (M).

[0043] The capping layer 114 serves as a second layer for copper to be deposited thereon. In the special case of electroplating the stabilizer metal, the superconducting tape is typically immersed in a solution containing copper ions, such as a copper sulfate solution. An electric current is passed through the capping layer 114 to react the Cu 2+ +2e - →Cu occurs on the surface of the cover layer 114. The cover layer 114 acts as a cathode in the solution, so that the metal ions are reduced to Cu metal atoms and deposited on the belt. On the other hand, a copper-containing anode is placed in the solution, where an oxidation reaction occurs, so that copper ions enter the solution, are reduced and deposited on the cathode.

[0044] In the absence of any secondary reactions, the current delivered to a conductive surface during electroplating is proportional to the amount of metal deposited (Faraday's law of electrolysis). Using this relationship, the mass of deposited material forming the stabilizer layer 116, and therefore its thickness, can be easily controlled.

[0045] While the foregoing generally refers to copper, it should be noted that other metals may also be used, including aluminum, silver, gold, and other thermally and electrically conductive metals. However, in order to reduce the overall material cost for forming superconducting tape, it is generally desirable to utilize non-precious metals.

[0046] Despite the foregoing and Figure 1 Electroplating along one side of the superconducting tape to form the stabilizer layer 116 is described, but it should also be noted that the opposite main side of the superconducting tape may also be coated, and indeed, the entire structure may be coated to facilitate packaging. Those skilled in the art will note that in Figure 1 The above description of the HTS conductor 100 is provided by way of example only. The superconducting articles described below may use any suitable superconducting conductor.

[0047] Figure 2 Shown is a cross-sectional view of another embodiment of the present invention, in which the entire superconducting tape is encapsulated by a covering stabilizer layer 118, which includes a first stabilizer layer 118a, a second stabilizer layer 118b disposed on the opposite major surface of the superconducting tape, and the first and second stabilizer layers 118a, 118b are joined together along the side surface of the superconducting tape to form generally convex side portions or side bridges 120a and 120b. This particular structure is desirable in order to further improve current flow and further protect the HTS layer 114 in the event of low-temperature failure, quench, etc. By forming the first and second stabilizer layers 118a and 118b, the cross-sectional area of ​​the deposited stabilizer layer is essentially doubled, thereby providing a significant improvement in current carrying capacity. Electrical continuity between the stabilizer layers 118a and 118b can be provided by the lateral bridging portions 120a and 120b. In this regard, the lateral bridging portions 120a and 120b can desirably have a positive radius of curvature, thereby forming a generally convex surface, which can further reduce charge accumulation at high voltages that the HTS power device will experience. In addition, when a suitable conductive material is used for the substrate 110, such as Figure 2 As shown, further current carrying capacity can be provided by encapsulation (completely surrounding the constituent layers of the article). That is, bridging portions extending laterally and defining the side surfaces of the tape can provide electrical connections to the substrate itself, which can increase the current carrying capacity of the coated conductor (tape).

[0048] While one embodiment of the invention is particularly suitable for forming a continuous stabilizer layer having side bridges formed of the same material, other embodiments use different materials for the side bridges. For example, the side surfaces can be masked during stabilizer deposition, the mask subsequently removed and a different side bridge composition deposited. Particularly suitable are high melting point solders, such as lead-tin compositions. Typically, such solders have a melting point greater than about 180°C. It is important to use a high melting point solder or to use a surrounding stabilizer (whose melting point is also greater than 180°C) (e.g., copper). In particular, high melting point materials allow the end user to have improved flexibility in conductor processing, since, for example, a wider range of temperatures over which the conductor can be manipulated during a joining operation.

[0049] although Figure 2Not shown, it is generally desirable to deposit a noble metal layer along the entire superconducting tape, particularly along the side surfaces of the superconducting tape, to isolate the superconducting layer 114 from the material of the bridging portions 120a and 120b, which may be a non-noble metal such as copper or aluminum as described above.

[0050] Figure 3 The figure shows a schematic diagram of the process of cutting the base conductor of a 2G HTS wire using a mechanical slitting machine. As mentioned above, it is usually more cost-effective to manufacture HTS wire with a relatively large width (e.g., from 12mm to 10cm or more) as the base conductor. The wire can then be slit along its length to produce multiple wires with smaller widths. Due to cost and throughput speed reasons, the use of a mechanical slitting machine is very desirable. However, if Figure 3 As shown, mechanical shearing caused by the slitting blade 304 may damage the cut edge of the HTS wire in the area indicated by the dashed circle 320. Cracks in the relatively brittle HTS layers and buffer layers may propagate and extend beyond the edge region, causing wire expansion, layer delamination, and Ic degradation. Figure 4 Shown is a photomicrograph of a magnified image of the edge of the HTS wire 100 after slitting, showing a crack 420 in the buffer layer and the HTS layer 412 extending from the edge of the slit.

[0051] Figure 5A A cross-section of a multilayer HTS wire 500 according to one embodiment of the present invention is shown. As described above, a buffer layer 112 and an HTS layer 114 are formed on a substrate layer 110. An encapsulating cover layer (typically a noble metal such as silver) is deposited over the entire structure. Figure 5B , two parallel stripes 502 are cut in the length direction, all the way to the HTS wire 500 base conductor, while the covering layer, HTS layer and buffer layer are removed. In some embodiments, the stripes are cut after the encapsulation metal layer is deposited and before the original HTS wire is cut, so as to minimize any positional errors. Although the stripes can be formed before the encapsulation layer is deposited, the additional processing steps tend to introduce undesirable positioning errors about the slit position relative to the stripes. In some embodiments, an additional covering layer is deposited after the stripes are cut and before the stripes are cut. This second layer (deposited on the stripes) is used to cover the edges of the HTS layer and the buffer layer to provide mechanical support and protect these layers from being exposed to the atmosphere or pollutants. Positional defects are reduced by depositing only a thin second layer. After cutting the stripes, the HTS wire can be mechanically cut along line 522 to form two HTS wires with narrower widths.

[0052] Figure 6 Shown by Figure 5BA cross section of one of the two narrower HTS wires resulting from the cut is shown. Damage such as crack 620 is formed in the region indicated by dashed circle 603. Since the brittle buffer layer and the HTS layer have been removed by forming stripe 502, when the damage extends throughout region 603, the crack cannot extend into the bulk of the HTS layer and buffer layer in the remainder of the HTS wire.

[0053] exist Figure 7 In the embodiment shown, another thin encapsulating cover layer 719 is applied to the HTS wire, which fills the stripes 502 with a cover material (e.g., silver) that covers the edges of the HTS and buffer layers exposed during stripe formation to provide mechanical protection to these layers and to protect the superconducting layers from chemicals during subsequent metal plating. In some embodiments, an encapsulating stabilizer layer may then be applied over the entire HTS wire in the manner described above.

[0054] Figure 8 Shown is a micrograph of an HTS wire 800 with striations 802 formed prior to slicing. Figure 8 As shown, cracks 820 caused by mechanical cutting are evident along the cut edge of the HTS wire in the HTS layer and buffer layer 812. However, none of the damage extends beyond the 802 line.

[0055] According to one embodiment of the present invention, stripes that block edge damage extension can be formed in various ways, including but not limited to laser ablation, etching, or ion beam or plasma milling. For example, in some embodiments, femtosecond pulsed lasers can be used to form stripes to remove material in desired locations. In other embodiments, stripes can be formed by patterning the buffer layer and the superconducting layer during deposition so that there is no deposition of the buffer layer or the superconducting layer within the stripes.

[0056] In order to completely prevent cracks from extending between the buffer layer and the HTS layer, it is ideal to remove all or substantially all of the buffer layer and HTS material in the stripe. In some cases, the stripe can extend into the substrate layer. In some embodiments, the width of the stripe will be at least 10 μm, for example at least 20 μm, at least 30 μm, at least 40 μm, at least 50 μm, at least 100 μm, or at least 500 μm. Since stripe processing renders a portion of the original HTS wire unusable, it is desirable to make the stripe as narrow as possible while still preventing the extension of damage caused by cutting. It is also generally easier and faster to form narrow stripes than to form wide stripes using, for example, laser ablation or ion beam milling.

[0057] In some embodiments, stripes will be formed on either side of the desired location of the mechanical incision, such as Figure 5A and 5BSee also Figure 6 , the position of each stripe can make the distance 512 between the edge of the effective HTS layer (the edge formed by the stripe) and the edge of the slit of the HTS wire be 500μm or less, such as 200μm or less, 100μm or less, or 50μm or less. In some embodiments, the position of each stripe can make the distance 510 between the edge of the effective HTS layer (the edge formed by the stripe) and the edge of the slit of the HTS wire greater than the maximum positioning error of the cutting process used. For example, when the positioning error of the cutting process is 10-50μm, the distance 510 can be greater than 50μm. This ensures that the slit is formed outside the inner edge of the stripe, so that the stripe can effectively prevent the extension of mechanical errors.

[0058] In one specific non-limiting example, the buffer layer and superconducting layer were deposited on a 50 μm thick and 12 mm wide Hastelloy substrate layer. In this specific example, the buffer layer was a buffer stack as described above with a combined thickness of ~0.2 μm, while the superconducting layer was a REBCO layer with a thickness of 1.6 μm. A silver encapsulation cover layer with a thickness of 1.0 μm was deposited over the entire structure. The base HTS wire was slit along its length to produce three separate HTS wires with a width of about 4 mm.

[0059] like Fig. 9 As shown, a commercially available femtosecond pulse laser is then used to cut four separate stripes (901, 902, 903, and 904) in the length direction in the base HTS wire 900. The width 912 of each stripe is about 20 μm and the depth is about 2 μm. Fig.13 Starting from the left side 910 of the base HTS wire shown in , the first stripe 901 is cut so that the distance 911 from the left edge of the base HTS wire to the left edge of the first stripe is about 3.94 mm. Then the second stripe 902 is cut so that the distance 914 from the left edge of the base HTS wire to the left edge of the second stripe is about 4.01 mm. As a result, the distance 913 between the two stripes (from the right edge of the first stripe to the left edge of the second stripe) is about 50 microns. The third stripe 903 is cut so that the distance 915 from the left edge of the base HTS wire to the left edge of the third stripe is about 7.97 mm. Then the fourth stripe is cut so that the distance 916 from the left edge of the base HTS wire to the left edge of the fourth stripe is about 8.04 mm. Therefore, the distance between the right edge of the third stripe and the left edge of the fourth stripe is also about 50 microns.

[0060] Afterwards, a mechanical slitter is used to slit the base HTS wire at the position indicated by the dashed line 922 to form three final HTS wires 320 with a width of about 3.94 mm. The slitter is positioned to slit the base HTS wire through the 50 μm shoulder between the first and second stripes and between the third and fourth stripes. For this example, if the maximum position error of the mechanical slitter is ±15 μm, it can be ensured that the slit is separated from the edge of the effective HTS layer produced by the stripes.

[0061] Fig.10 Another embodiment of the present invention is shown in which a single stripe 1002 is formed (for each desired kerf) and then the HTS wire 1000 is cut within the stripe as shown by the dashed line 1022. Fig.11 As shown, in the resulting structure, the HTS layer and the buffer layer are removed, forming a “notch” 1130 at the slit edge of the final HTS wire 1100 . Figure 10-11 One problem with embodiments of the present invention is that it is difficult, if not impossible, to reliably cut the HTS wire within a stripe unless very large stripes are used. The positional error of the mechanical cut is as high as 10-50 μm. Especially for high-speed production, it is difficult to ensure that the cut occurs within a narrow stripe. Due to positioning errors, attempting to cut within a stripe will result in a certain number of actual cuts occurring on or even within the stripe, completely eliminating any advantage of the stripe. Applicants have found that an optimal balance of reliability, production speed, and reduced waste of HTS wire can be achieved by using a relatively narrow stripe width and cutting the wire within a wider shoulder between two stripes (or between the outermost stripe and the edge of the HTS wire) as described above.

[0062] For ease of illustration, the stripes shown in the schematics herein all have a rectangular cross-section. However, it will be appreciated by those skilled in the art that the actual shape of the stripes will depend greatly on the equipment used to form the stripes. For example, stripes cut using a laser will tend to have a circular base rather than the rectangular shape shown in the figures. Furthermore, in some embodiments, it may be desirable to form stripes with different cross-sectional shapes, such as Fig. 12A The V-shaped stripes 1230 shown, or Fig. 12B and Fig. 12C The inclined edge stripes (1230B, 1230C) shown in FIG.

[0063] Fig.13A device is schematically shown for forming stripes using laser ablation and then separating a base HTS wire into multiple HTS wires of narrower width using mechanical slitting. The base HTS wire is wound on a delivery spool 1302 and fed into the device 1300 via guide and tension rollers 1303. As the base HTS wire is fed into the device, one or more lasers 1304 can be used to form a desired number of parallel stripes in the base HTS wire. As described above, the mechanical slitting machine blade 1305 can be oriented so that the base HTS wire is slit so that the stripes prevent mechanical damage from extending into the active HTS layer of the final separated HTS wire. After slitting, the final HTS wire can be fed through a guide roller 1306 and rolled onto a take-up spool 1307.

[0064] The present invention has wide applicability and can provide many advantages, as described and shown in the above examples. Depending on the specific application, the implementation will vary greatly, and not every implementation will provide all the advantages and all the goals that can be achieved by the present invention. The implementation can be based on any one or more of the following items:

[0065] Item 1: A superconducting article comprising:

[0066] Metal strip substrate;

[0067] a buffer layer covering the substrate;

[0068] a superconducting layer covering the buffer layer;

[0069] At least one stripe extending along the length of the superconducting article, in which a large part or all of the superconducting layer and the buffer layer are removed in an area, and at least a portion of the substrate is retained, the width of the stripe is about 500 μm or less, and the outer edge of the stripe is located between about 10 μm and about 500 nm from the outer edge of the superconducting article.

[0070] Item 2: The superconducting article of Item 1, wherein the at least one stripe extending along the length of the superconducting article comprises two stripes extending along the length of the superconducting article, the two stripes being located on opposite sides of the superconducting article.

[0071] Item 3: The superconducting article of any of the preceding items, wherein the width of the stripes is about 200 μm or less, about 100 μm or less, about 50 μm or less, or about 20 μm or less.

[0072] Item 4: The superconducting article of any of the preceding items, wherein the width of the stripes is about 20 μm.

[0073] Item 5: The superconducting article of any of the preceding items, wherein the depth of the stripes is about 2 μm.

[0074] Item 6: The superconducting article of any preceding item, wherein the depth of the striations is at least equal to the total thickness of any material layers deposited on the metal substrate.

[0075] Item 7: The superconducting article of any preceding item, wherein the depth of the stripes is greater than the total thickness of any material layers deposited on the metal substrate.

[0076] Item 8: A method of forming a superconducting article, the method comprising:

[0077] Providing a base superconducting article comprising a metal tape substrate, a buffer layer covering the substrate, and a superconducting layer covering the buffer layer;

[0078] forming at least two substantially parallel stripes along the length direction of the substrate superconducting article, the stripes comprising two gaps having substantially no superconducting layer or buffer layer covering the substrate;

[0079] The base superconducting article is cut through its entire thickness in the lengthwise direction in the portion of the superconducting article between the two stripes.

[0080] Item 9: The method of Item 8, wherein the two stripes are formed using laser ablation, etching, or ion beam or plasma milling.

[0081] Item 10: The method as described in Item 8, wherein the two stripes are formed using laser ablation or etching by femtosecond pulse laser.

[0082] Item 11: The method of Item 8, wherein the two stripes are formed by patterning the buffer layer and the superconducting layer during deposition such that no buffer layer or superconducting layer is deposited within the stripes.

[0083] Item 12: The method of any one of Items 8-11, wherein slitting the base superconducting article comprises slitting the superconducting article using a mechanical slitting machine.

[0084] Item 13: The method of any one of Items 8-11, wherein slicing the base superconducting article comprises slicing the superconducting article using a laser.

[0085] Item 14: A method as described in any one of Items 8-13, wherein cutting the base superconducting product in the length direction includes cutting the base superconducting product in the length direction so that the distance between the cut and the relative edges of each of the two substantially parallel stripes is greater than the maximum position error of the cutting process.

[0086] Item 15: The method of any one of Items 8-13, wherein the base superconducting article has a starting width of at least 12 mm before slitting.

[0087] Item 16: The method of any one of Items 8-13, wherein the initial width of the base superconducting article before slitting is 12 mm to 10 cm.

[0088] Item 17: The method of any one of Items 8-16, wherein a distance between two parallel stripes is about 50 microns.

[0089] Item 18: The method of any of Items 8-17, wherein slitting the base superconducting article between the at least two parallel stripes produces a plurality of final superconducting articles, each of which has a width less than the base superconducting article.

[0090] Item 19: The method of any of items 8-17, wherein slitting the base superconducting article between the at least two parallel stripes produces a plurality of final superconducting articles, each of which has approximately the same width.

[0091] Item 20: The method of any of Items 8-19, further comprising depositing a protective cap layer on the superconducting layer before forming the at least two substantially parallel stripes.

[0092] Item 21: The method of any one of Items 8-19, wherein a cover layer is applied to the base superconducting article after forming the at least two substantially parallel stripes and before slitting the base superconducting article in the length direction.

[0093] Item 22: The method of any of Items 20-21, wherein the capping layer comprises silver.

[0094] Item 23: A method of forming a superconducting article, the method comprising:

[0095] Providing a base superconducting article comprising a metal tape substrate, a buffer layer covering the substrate, and a superconducting layer covering the buffer layer;

[0096] forming a first pair of two substantially parallel stripes along the length of the substrate superconducting article, the stripes comprising two gaps having substantially no superconducting layer or buffer layer covering the substrate;

[0097] forming a second pair of two substantially parallel stripes along the length of the base superconducting article, the stripes comprising two gaps having substantially no superconducting layer or buffer layer covering the base;

[0098] The base superconducting article is slit lengthwise through its entire thickness in the portion of the superconducting article between two parallel stripes in each pair of substantially parallel stripes.

[0099] Whenever the terms "automatic", "automated" or similar terms are used herein, these terms will be understood to include manual initiation of automatic or automated processes or steps. In the specification and claims, the terms "including" and "comprising" are used in an open manner and should therefore be interpreted as "including but not limited to...". As long as no term is specifically defined in this specification, the purpose is to give the term its simple and ordinary meaning. The accompanying drawings are intended to aid in understanding the present invention and, unless otherwise indicated, are not drawn to scale. As used herein, "right", "left", "lower", "upper", "lower", "horizontal", "vertical" and the like indicate reference directions in the accompanying drawings. These terms are used for convenience only and are not restrictive.

[0100] In addition, it should be appreciated that an embodiment of the present invention can be implemented by computer hardware or software or a combination of the two. According to the method and accompanying drawings described in this specification, the method can be implemented in a computer program using standard programming techniques, which includes a computer-readable storage medium configured with a computer program, wherein the storage medium so configured enables the computer to operate in a specific and predefined manner. Each program can be implemented in a high-level process or object-oriented programming language to communicate with a computer system. However, if necessary, the program can be implemented in assembly language or machine language. In any case, the language can be a compiled or interpreted language. In addition, the program can be run on a dedicated integrated circuit programmed for this purpose.

[0101] The scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, material compositions, means, methods and steps described in the specification. A person of ordinary skill in the art should easily understand from the disclosure that processes, machines, manufactures, material compositions, means, methods or steps that currently exist or will be developed in the future and perform substantially the same functions as the corresponding embodiments herein or achieve substantially the same results can be used according to the present disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, means, methods or steps within their scope. The figures described herein are generally schematic and do not necessarily depict an embodiment of the present invention in appropriate proportions or ratios.

Claims

1. A superconducting product, comprising: Metal strip substrate; a buffer layer covering the substrate; a superconducting layer covering the buffer layer; At least two stripes extending along the length of the superconducting article, in which a large part or all of the superconducting layer and the buffer layer are removed in an area, and at least a part of the substrate is retained, the width of the stripes is 50 μm or less, and the outer edge of the stripes is located between 10 μm and 500 nm from the outer edge of the superconducting article, wherein: Where the stripes are formed, the stripes extend into a portion of the substrate.

2. The superconducting product according to claim 1, wherein: The at least one stripe extending along the length of the superconducting article includes two stripes extending along the length of the superconducting article, the two stripes being located on opposite sides of the superconducting article.

3. The superconducting product according to claim 1 or claim 2, wherein: The width of the stripes is 20 μm or less.

4. The superconducting product according to claim 1, wherein: The depth of the stripes is 2 μm.

5. A method of forming a superconducting article, the method comprising: Providing a base superconducting article comprising a metal tape substrate, a buffer layer covering the substrate, and a superconducting layer covering the buffer layer; forming at least two parallel stripes along the length direction of the substrate superconducting article, the stripes comprising two gaps having no superconducting layer or buffer layer covering the substrate, wherein the stripes extend into a portion of the substrate at the locations where the stripes are formed; The base superconducting article is cut through its entire thickness in the lengthwise direction in the portion of the superconducting article between the two stripes.

6. The method of claim 5, wherein: The two stripes are formed using laser ablation, etching, ion beam or plasma milling.

7. The method of claim 5, wherein: The two stripes were formed using laser ablation, etching with a femtosecond pulsed laser.

8. The method of claim 5, wherein: The two stripes are formed by patterning the buffer layer and the superconducting layer during deposition, so that no buffer layer or superconducting layer is deposited within the stripes.

9. The method of claim 5, wherein: Slitting the base superconducting article includes slitting the superconducting article using a mechanical slitting machine.

10. The method of claim 5, wherein: Slicing the base superconducting article includes slicing the superconducting article using a laser.

11. The method of claim 5, wherein: Cutting the base superconducting product in the length direction includes cutting the base superconducting product in the length direction so that the distance between the cut and the opposite edge of each of the two parallel stripes is greater than the maximum position error of the cutting process.

12. The method of claim 5, wherein: The initial width of the base superconducting article before slitting is at least 12 mm.

13. The method of claim 5, wherein: The initial width of the base superconducting article before slitting is 12 mm to 10 cm.

14. The method of claim 5, wherein: The distance between two parallel stripes is 50 microns.

15. The method of claim 5, wherein: Cutting the base superconducting article between the at least two parallel stripes produces a plurality of final superconducting articles, each of which has a width smaller than the base superconducting article.

16. The method of claim 5, wherein: Cutting the base superconducting article between at least two parallel stripes produces a plurality of final superconducting articles, each of which has the same width.

17. The method of claim 5, further comprising depositing a protective cap layer on the superconducting layer before forming the at least two parallel stripes.

18. The method of claim 5, wherein: After forming the at least two parallel stripes and before slitting the base superconducting article in the length direction, a cover layer is applied to the base superconducting article.

19. The method of claim 5, wherein: The cover layer contains silver.

20. A method of forming a superconducting article, the method comprising: Providing a base superconducting article comprising a metal tape substrate, a buffer layer covering the substrate, and a superconducting layer covering the buffer layer; forming a first pair of two parallel stripes along the length of the substrate superconducting article, the stripes comprising two gaps having no superconducting layer or buffer layer covering the substrate, wherein the stripes extend into a portion of the substrate at the locations where the stripes are formed; forming a second pair of two parallel stripes along the length of the base superconducting article, the stripes comprising two gaps having no superconducting layer or buffer layer covering the base material, wherein the stripes extend into a portion of the base material at the locations where the stripes are formed; The base superconducting article is cut lengthwise through its entire thickness in the portion of the superconducting article between two parallel stripes in each pair of parallel stripes.

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