JP2018206521A - High-temperature superconducting wire and superconducting coil - Google Patents

Abstract

To provide a high-temperature superconducting wire and a superconducting coil that reduce peeling stress generated upon cooling and can maintain tensile strength.SOLUTION: A high-temperature superconducting wire 10 has a high-temperature superconductor and a stabilization layer. In the high-temperature superconducting wire 10, the stabilization layer 12 is composed of two stabilization layers 12a, 12b on at least one principal surface of the high-temperature superconducting wire 10 and the inner stabilization layer 12a of two stabilization layers has a Young's modulus lower than a Young's modulus of the outer stabilization layer 12b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a high-temperature superconducting wire and a superconducting coil.

  When using a superconducting coil in which a high-temperature superconducting wire is wound, cooling is necessary to develop superconducting characteristics. When the superconducting coil is cooled, a peeling stress is generated in the high temperature superconducting wire in the direction in which the high temperature superconducting layer peels from the base material due to a difference in thermal shrinkage between the impregnating resin and the high temperature superconducting wire. If delamination or cracks occur due to this peeling stress, stable superconducting characteristics may not be obtained.

  Conventionally, various structures have been proposed in order to reduce the peeling stress. For example, Patent Document 1 describes a structure in which a release material layer is provided on the surface of a superconducting wire. Patent Document 2 describes a structure in which a carbon layer is formed on the surface of a superconducting wire, and the carbon layer breaks with a weak force between the impregnating resin and the superconducting wire, thereby preventing damage to the superconducting layer. Has been.

JP 2010-267550 A JP-A-2006-134418

  When a flexible layer such as a release material layer or a carbon layer is provided on the superconducting wire, the Young's modulus of the entire wire is lowered, and the tensile strength of the superconducting wire is lowered. When the superconducting wire is wound into a coil, when the release material is applied or the carbon layer is formed, the manufacturing process of the superconducting coil becomes complicated.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the high temperature superconducting wire and superconducting coil which can reduce the peeling stress at the time of cooling and can maintain a tensile strength.

  In order to solve the above problems, the present invention is a high-temperature superconducting wire having a high-temperature superconductor and a stabilization layer, wherein the stabilization layer has two layers of stabilization on at least one main surface of the high-temperature superconducting wire. There is provided a high-temperature superconducting wire characterized in that, among the two stabilization layers, the Young's modulus of the inner stabilization layer is lower than the Young's modulus of the outer stabilization layer.

  The stabilization layer is formed on a tape-shaped substrate, an intermediate layer formed on the substrate, a superconducting layer formed on the intermediate layer and made of the high-temperature superconductor, and the superconducting layer. Provided on the outer periphery of the superconducting laminate having the protective layer, and the two stabilization layers may be provided at least on the surface of the protective layer.

  The present invention also provides a superconducting coil, wherein the high-temperature superconducting wire is wound and impregnated with a resin therebetween.

  According to the present invention, since the stabilizing layer having a low Young's modulus is provided inside the outer stabilizing layer, the peeling stress during cooling is reduced, and the tensile strength can be maintained.

It is a perspective view which shows typically an example of a superconducting coil. It is a partial expanded sectional view which shows an example of the superconducting coil of embodiment. It is sectional drawing which shows an example of a superconducting laminated body typically. 6 is a partial enlarged cross-sectional view showing an example of a superconducting coil of Comparative Example 1. FIG. 6 is a partial enlarged cross-sectional view showing an example of a superconducting coil of Comparative Example 2. FIG.

Hereinafter, based on a preferred embodiment, the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an example of a superconducting coil. FIG. 2 shows a cross section of part A of FIG. FIG. 3 shows an example of a superconducting laminate. The superconducting coil 20 of this embodiment is impregnated with a resin 21 while the high-temperature superconducting wire 10 is wound. The high-temperature superconducting wire 10 has a stabilization layer 12 around the superconducting laminate 11.

  The superconducting laminate 11 includes a tape-like substrate 11a, an intermediate layer 11b formed on the substrate 11a, a superconducting layer 11c formed on the intermediate layer 11b, and a protective layer formed on the superconducting layer 11c. 11d. In the present specification, the direction in which the layers such as the base material 11a, the intermediate layer 11b, the superconducting layer 11c, and the protective layer 11d are laminated is the thickness direction. The width direction is a direction perpendicular to the longitudinal direction and the thickness direction.

  The base material 11a is a tape-shaped metal base material, for example, and has main surfaces on both sides in the thickness direction. The width of the base material 11a is, for example, about 5 to 20 mm. What is necessary is just to adjust the thickness of the base material 11a suitably according to the objective, for example, it is the range of 10-500 micrometers.

  The intermediate layer 11b is provided between the base material 11a and the superconducting layer 11c. The intermediate layer 11b may have a multilayer structure, and may include a diffusion prevention layer, a bed layer, an alignment layer, a cap layer, and the like in order from the base material 11a side to the superconducting layer 11c side. These layers are not necessarily one layer at a time, and some layers may be omitted, or two or more of the same kind of layers may be laminated repeatedly.

  The superconducting layer 11c is composed of a high temperature superconductor. The high-temperature superconductor is a superconductor having a transition temperature of about 25K or higher, and among them, a superconductor having a transition temperature of liquid nitrogen temperature (about 77K) or higher is preferable. Specific examples of the high-temperature superconductor include a RE-Ba-Cu-O-based oxide containing a rare earth element (RE) and a Bi-Sr-Ca-Cu-O-based oxide containing a bismuth element (Bi).

  The protective layer 11d has functions such as bypassing overcurrent generated at the time of an accident and suppressing a chemical reaction occurring between the superconducting layer 11c and a layer provided on the protective layer 11d. Examples of the material of the protective layer 11d include silver (Ag), copper (Cu), gold (Au), alloys of gold and silver, other silver alloys, copper alloys, and gold alloys. The protective layer 11d covers at least the surface of the superconducting layer 11c.

  The high-temperature superconducting wire 10 has a stabilization layer 12 made of metal such as metal plating or metal foil on the outer periphery of the superconducting laminate 11. The stabilization layer 12 is a part of a region selected from the surface of the protective layer 11d, the side surface of the protective layer 11d, the side surface of the superconducting layer 11c, the side surface of the intermediate layer 11b, the side surface of the base material 11a, or the back surface of the base material 11a. You may cover everything. As thickness of the stabilization layer 12, about 10-300 micrometers is mentioned, for example.

  In the high temperature superconducting wire 10 of the present embodiment, the stabilization layer 12 has two stabilization layers 12 a and 12 b on at least one main surface of the high temperature superconducting wire 10. The main surfaces of the high-temperature superconducting wire 10 are surfaces on both sides in the thickness direction of the high-temperature superconducting wire 10. As shown in FIG. 2, when the high-temperature superconducting wire 10 is wound in the superconducting coil 20, the resin 21 is impregnated while the main surfaces of the high-temperature superconducting wire 10 face each other. For example, on the outer periphery of the superconducting laminate 11 shown in FIG. 3, the surface of the protective layer 11 d or the back surface of the base material 11 a corresponds to the main surface of the high-temperature superconducting wire 10.

  In the two stabilization layers 12a and 12b, the stabilization layer 12a having a low Young's modulus is disposed on the inside, and the stabilization layer 12b having a high Young's modulus is disposed on the outside. Since it plays the role of a buffer material, the peeling stress applied to the high-temperature superconducting wire 10 can be reduced. In addition, the stabilization layer 12 b having a high Young's modulus on the outside can maintain the tensile strength in the longitudinal direction of the high-temperature superconducting wire 10 and can impart mechanical durability against thermal shrinkage of the impregnating resin 21. The two stabilization layers 12a and 12b are made of metal and excellent in adhesion.

  In the superconducting laminate 11 having the base material 11a, since the thickness of the base material 11a generally occupies most of the thickness of the superconducting laminate 11, it is on the surface of the protective layer 11d rather than on the back surface of the base material 11a. This is closer to the superconducting layer 11c. Therefore, the two stabilization layers 12a and 12b are preferably provided on at least the surface of the protective layer 11d.

  As a material constituting the stabilization layer 12a having a low Young's modulus, for example, a metal material having a Young's modulus E of 50 GPa or less is preferable, and a metal material having an E of 40 GPa or less is more preferable. Specific examples include solders such as Sn-Ag-Cu (E = 31 GPa), Sn-Zn-Al (E = 37 GPa), Sn-Bi-Ag (E = 24 GPa), Sn-Pb (E = 22 GPa). It is done. The thickness of the stabilization layer 12a having a low Young's modulus is, for example, 5 μm or more, and examples thereof include about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, and about 50 μm. Since the stabilization layer 12a having a low Young's modulus functions as a buffer layer that reduces the peeling stress acting in the thickness direction of the high-temperature superconducting wire 10, the surface of the protective layer 11d and the base material 11a are more than the side surfaces of the high-temperature superconducting wire 10. It should be thick. On the other hand, on the side surface of the high-temperature superconducting wire 10, the stabilization layer 12a having a low Young's modulus is preferably formed thin in order to prevent the cross-sectional shape of the wire from becoming distorted.

  As a material constituting the stabilization layer 12b having a high Young's modulus, for example, a metal material having a Young's modulus E of 70 GPa or more is preferable, and a metal material having an E of 100 GPa or more is more preferable. Examples include copper (Cu), silver (Ag), and gold (Au). The thickness of the stabilization layer 12b having a high Young's modulus is, for example, 5 μm or more, and examples thereof include about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, and about 50 μm.

  Examples of the ratio of the thicknesses of the two stabilization layers 12a and 12b include 10%: 90% to 90%: 10%. As specific examples of this ratio, 10%: about 90%, 20%: about 80%, 30%: about 70%, 40%: about 60%, 50%: about 50%, 60%: about 40%, 70 %: About 30%, 80%: about 20%, 90%: about 10%.

For comparison, FIG. 4 shows a superconducting coil 201 produced from a high-temperature superconducting wire 101 in which only one stabilization layer 12c having a medium Young's modulus is laminated on the outer periphery of the superconducting laminate 11. In this case, since the stabilizing layer 12c does not have a buffering effect, it is considered that the peeling stress during cooling is not reduced and the deterioration of characteristics increases.
FIG. 5 shows a superconducting coil 202 made from a high-temperature superconducting wire 102 having a stabilization layer 12a having a low Young's modulus on the outside and a stabilization layer 12b having a high Young's modulus on the inside. In this case, since the stabilization layer 12a having a low Young's modulus is separated from the superconducting layer, it is considered that the effect of reducing the peeling stress is thin and the deterioration of the characteristics increases.

  In order to fabricate the superconducting coil 20 using the tape-shaped high-temperature superconducting wire 10, for example, the wire is wound around the outer peripheral surface of the winding frame to form a coil-shaped multi-layer winding coil and then wound. A method of fixing the superconducting wire by impregnating a resin such as an epoxy resin so as to cover the wire is mentioned.

As mentioned above, although this invention has been demonstrated based on suitable embodiment, this invention is not limited to the above-mentioned embodiment, A various change is possible in the range which does not deviate from the summary of this invention.
The high-temperature superconducting wire and the superconducting coil can have connection terminals to the outside and connecting portions between the wires. These portions may have a different cross-sectional structure from other portions.

Hereinafter, the present invention will be specifically described with reference to examples.
(Preparation of superconducting laminate)
A first intermediate layer made of Gd ₂ Zr ₂ O _{7 having a} thickness of 1 μm was formed on the surface of a Hastelloy (registered trademark) tape base material having a thickness of 75 μm and a width of 12 mm by an IBAD (ion beam assisted vapor deposition) method. Next, a second intermediate layer made of CeO _{2 having a} thickness of 0.5 μm was formed on the first intermediate layer by a pulse laser deposition (PLD) method. Next, a superconducting layer made of GdBa ₂ Cu ₃ O _7-x having a thickness of 2 μm was formed on the second intermediate layer by the PLD method. Next, a protective layer made of Ag having a thickness of 7 μm was laminated on the superconducting layer by sputtering. The obtained laminate was subjected to oxygen annealing at a temperature of 500 ° C. to obtain a superconducting laminate.

(Example)
A first stabilizing layer having a thickness of 20 μm and a Young's modulus of 30 GPa was laminated on the outer periphery of the superconducting laminate. Next, a second stabilization layer having a thickness of 20 μm and a Young's modulus of 130 GPa was laminated on the first stabilization layer to produce a superconducting wire having two stabilization layers. The obtained superconducting wire was wound and impregnated with a resin such as epoxy between the wires to produce a superconducting coil having an outer diameter (OD) of 140 mm and an inner diameter (ID) of 100 mm. When 20 superconducting coils were prepared, cooled to liquid nitrogen temperature, and the superconducting wire was energized, one of the 20 coils was found to be deteriorated.

(Comparative Example 1)
A superconducting wire having one stabilization layer was prepared by laminating a stabilization layer having a thickness of 40 μm and a Young's modulus of 50 GPa on the outer periphery of the superconducting laminate. The obtained superconducting wire was wound and a resin such as epoxy was impregnated between the wires to produce a superconducting coil having an outer diameter (OD) of 140 mm and an inner diameter (ID) of 100 mm. When 20 superconducting coils were prepared, cooled to liquid nitrogen temperature, and the superconducting wire was energized, 6 of the 20 coils were found to be deteriorated.

(Comparative Example 2)
A first stabilizing layer having a thickness of 20 μm and a Young's modulus of 130 GPa was laminated on the outer periphery of the superconducting laminate. Next, a second stabilizing layer having a thickness of 20 μm and a Young's modulus of 30 GPa was laminated on the first stabilizing layer to produce a superconducting wire having two stabilizing layers. The obtained superconducting wire was wound and a resin such as epoxy was impregnated between the wires to produce a superconducting coil having an outer diameter (OD) of 140 mm and an inner diameter (ID) of 100 mm. When 20 superconducting coils were prepared, cooled to liquid nitrogen temperature, and the superconducting wire was energized, 10 out of 20 coils were found to be deteriorated.

  In Example 1, the Young's modulus of the entire superconducting wire was the same as in Comparative Examples 1 and 2, but the coil deterioration during cooling could be remarkably reduced. From this result, it was proved that Example 1 had a structure strong against peeling stress as compared with Comparative Examples 1 and 2.

DESCRIPTION OF SYMBOLS 10 ... High temperature superconducting wire, 11 ... Superconducting laminated body, 11a ... Base material, 11b ... Intermediate layer, 11c ... Superconducting layer, 11d ... Protective layer, 12 ... Stabilizing layer, 12a ... Stabilizing layer with low Young's modulus, 12b ... Stabilization layer with high Young's modulus, 20 ... superconducting coil, 21 ... impregnation resin.

Claims (3)

A high-temperature superconducting wire having a high-temperature superconductor and a stabilization layer,
The stabilization layer has two stabilization layers on at least one main surface of the high-temperature superconducting wire, and among the two stabilization layers, the Young's modulus of the inner stabilization layer is the outer layer. A high-temperature superconducting wire characterized by a lower Young's modulus of the stabilizing layer.   The stabilization layer is formed on a tape-shaped substrate, an intermediate layer formed on the substrate, a superconducting layer formed on the intermediate layer and made of the high-temperature superconductor, and the superconducting layer. 2. The high-temperature superconducting wire according to claim 1, wherein the high-temperature superconducting wire is provided on an outer periphery of a superconducting laminate having a protective layer, and the two stabilization layers are provided on at least a surface of the protective layer.   A superconducting coil, wherein the high-temperature superconducting wire according to claim 1 is wound and impregnated with a resin therebetween.

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