JP2013246881A - Insulation coating structure of superconducting wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation coating structure of a superconducting wire rod in which interlayer delamination of the superconducting wire rod can be suppressed, and excellent superconducting characteristics can be maintained.SOLUTION: A tape-like superconducting wire rod 11 is constituted by forming a superconductive layer 14 of a rare-earth-based oxide superconductor on a substrate 12 with an intermediate layer 13 interposed therebetween, forming stabilization layers 15, 16 on the superconductive layer 14, and then forming an insulation coating layer 17 on the outer periphery thereof. An insulation coating layer 17a at the end of the superconducting wire rod 11 in the width direction has a thickness D thicker than the thickness d of the insulation coating layer 17 in the intermediate part. Preferably, the thickness D of the insulation coating layer 17a is 15-35% thicker than the thickness d of the insulation coating layer 17 in the intermediate part. Furthermore, the thickness D of the insulation coating layer 17a is preferably 15-100 μm.

Description

  In the present invention, for example, a superconducting layer made of a rare earth-based oxide superconductor is formed on a metal substrate, and an insulating coating layer is formed on the superconducting layer, so that peeling of the superconducting layer at the end in the width direction is suppressed. The present invention relates to a superconducting wire insulation coating structure capable of maintaining superconducting characteristics.

  Since a superconducting wire using this kind of rare earth oxide superconductor has a tape shape, when the superconducting wire is wound to form a superconducting coil (pancake coil), the width of the superconducting wire is reduced. Bending stress acts on the end portion to become a starting point of peeling, and the superconducting layer is easily peeled off. Furthermore, when the tape of the superconducting wire is thinned in order to cut it in the longitudinal direction, the superconducting layer is likely to be peeled off with the cross section obtained by the cutting as the starting point of the peeling.

  This kind of insulating coating oxide superconducting wire is disclosed in Patent Document 1. That is, in this superconducting wire, an insulating material layer is formed so as to cover the entire circumferential surface with a substantially equal thickness, and a parting material layer is formed on a part of the outer surface of the insulating material layer. Then, the superconducting wire is wound to form a superconducting coil, and when it is cooled, the release material layer is peeled off, and the superconducting wire does not have a peeling force, so that the superconducting wire is hardly deteriorated.

JP 2011-198469 A

  In the superconducting wire having the conventional configuration described in Patent Document 1 described above, the release material layer is specifically provided only on one surface of the superconducting wire, and is not provided in other portions. When a superconducting coil formed from a superconducting wire is cooled or used, or when a superconducting coil is manufactured, stress such as bending stress tends to concentrate on the end portion in the width direction of the superconducting wire. For this reason, the end portion in the width direction of the superconducting wire becomes a starting point of delamination of the superconducting wire, the delamination expands inside, and delamination occurs in the superconducting layer. Therefore, there is a problem that the superconducting wire cannot maintain its superconducting characteristics.

  Accordingly, an object of the present invention is to provide an insulation coating structure for a superconducting wire that can suppress delamination of the superconducting wire and maintain good superconducting properties.

  In order to achieve the above object, the superconducting wire insulation coating structure according to the first aspect of the present invention has a superconducting layer of a rare earth oxide superconductor formed on a substrate via an intermediate layer, on the superconducting layer. A superconducting wire-like insulating coating structure in which a stabilizing layer is formed and an insulating coating layer is formed on the outer periphery thereof, and the insulating coating layer at the end in the width direction of the superconducting wire The structure is characterized in that the thickness is larger than the thickness of the insulating coating layer in the intermediate portion.

  The superconducting wire insulation coating structure according to claim 2 is the invention according to claim 1, wherein the thickness of the insulation coating layer at the end in the width direction of the superconducting wire is the thickness of the insulation coating layer at the intermediate portion. It is characterized by being 15-35% thicker than that.

  The insulation coating structure of the superconducting wire according to claim 3 is the invention according to claim 1 or 2, wherein the thickness of the insulation coating layer at the end portion in the width direction of the superconducting wire is 15 to 100 μm. It is characterized by being.

  According to a fourth aspect of the present invention, there is provided the insulating coating structure for a superconducting wire according to any one of the first to third aspects, wherein the outer surface of the insulating coating layer at the end in the width direction of the superconducting wire is curved. It is characterized by comprising.

  The superconducting wire insulating coating structure according to claim 5 is the invention according to claim 4, wherein the outer surface of the insulating coating layer at the end in the width direction of the superconducting wire is formed in an arcuate cross section. Features.

  The superconducting wire insulating coating structure according to claim 6 is the invention according to any one of claims 1 to 5, wherein the insulating coating layer is formed of a synthetic resin mainly composed of a polyimide resin. It is characterized by being.

According to the present invention, the following effects can be exhibited.
The insulation coating structure of the superconducting wire of the present invention is configured such that the thickness of the insulation coating layer at the end in the width direction of the superconducting wire is greater than the thickness of the insulation coating layer at the intermediate portion. For this reason, when the bending stress when forming the superconducting wire into a coil shape or the stress when cooling the coil of the superconducting wire acts on the superconducting wire, the insulation coating formed on the thickness of the end portion in the width direction of the superconducting wire The layer absorbs the stress and the superconducting wire easily retains its original shape, and the occurrence of delamination of the superconducting wire at the end in the width direction is suppressed.

  Therefore, according to the insulation coating structure of the superconducting wire of the present invention, it is possible to suppress delamination of the superconducting wire and to maintain the superconducting characteristics well.

It is sectional drawing which shows the superconducting wire of embodiment which actualized this invention, Comprising: (a) is sectional drawing which shows the superconducting wire of 1st Embodiment, (b) is sectional drawing which shows the superconducting wire of 2nd Embodiment. . Sectional drawing which shows the superconducting wire of 3rd Embodiment. (A) is a top view which shows the superconducting coil by a superconducting wire, (b) is sectional drawing which shows the superconducting coil. The graph which shows the superconducting characteristic of the superconducting coil of 1st Embodiment, and shows the relationship between an electric current and a voltage. The graph which shows the superconducting characteristic of the superconducting coil of 2nd Embodiment, and shows the relationship between an electric current and a voltage. The graph which shows the superconducting characteristic of the superconducting coil of 3rd Embodiment, and shows the relationship between an electric current and a voltage. (A) And (b) is sectional drawing which shows another example of the insulation coating layer in the superconducting wire of this invention.

(First embodiment)
Hereinafter, a first embodiment of the superconducting wire insulation coating structure of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1A, the superconducting wire 11 of the first embodiment has a tape shape, and a superconducting layer 14 is formed on a substrate 12 via an intermediate layer 13, and the first stable on the superconducting layer 14 is formed. The insulating layer 15 and the second stabilizing layer 16 are covered, and the insulating covering layer 17 is covered so as to cover these layers. The substrate 12 is made of a metal such as nickel alloy (Hastelloy), silver, or silver alloy, and has a thickness of 100 μm and a width of 10 mm, for example. Note that Hastelloy (registered trademark) is an alloy containing nickel as a main component and containing chromium, molybdenum, and the like, and has good heat resistance, mechanical strength, and the like. The intermediate layer 13 includes gadolinium / zirconium oxide (Gd / Zr oxide), magnesium oxide (MgO), yttrium-stabilized zirconium (YSZ), barium / zirconium oxide (Ba / Zr oxide), cerium oxide (CeO ₂ ). ) And the like, for example, a thickness of 500 nm and a width of 10 mm.

  The superconducting layer 14 is formed, for example, to a thickness of about 1 μm and a width of 10 mm by a rare earth oxide superconductor CVD method (chemical vapor deposition method). As rare earth elements, lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), yttrium (Y), And ytterbium (Yb). Examples of rare earth oxides include RE, Ba, Cu, and O. However, RE represents a rare earth element. Specific examples of the superconducting layer 14 include yttrium / barium / copper oxide (Y / Ba / Cu oxide) and lanthanum / barium / copper oxide (La / Ba / Cu oxide).

  The first stabilization layer 15 is formed to have a thickness of about 15 μm and a width of 10 mm, for example, by sputtering metal such as silver. The second stabilization layer 16 is formed, for example, by bonding a copper foil having a thickness of 100 μm to the first stabilization layer 15.

  The insulating coating layer 17 is formed by a coating method or an electrodeposition method so as to cover the outer peripheral portion of each layer with a synthetic resin having flexibility and electrical insulation. The thickness D of the insulating coating layer 17a at both ends in the width direction of the superconducting wire 11 is configured to be thicker than the thickness d of the insulating coating layer 17 at the intermediate portion. Furthermore, the outer surface of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 is formed by a curved surface 17b having an arcuate cross section.

  The synthetic resin for forming the insulating coating layers 17 and 17a is preferably a synthetic resin containing a polyimide resin as a main component, and a polyimide resin alone, a synthetic resin containing a polyimide resin as a main component and containing an epoxy resin, or the like can be used. . By using a synthetic resin having such flexibility and electrical insulation, stress such as bending stress received at the end in the width direction of the superconducting wire 11 can be received, the shape can be maintained, and electric field concentration can be reduced. it can.

  The thickness D of the insulating coating layer 17a at the end portion in the width direction of the superconducting wire 11 is preferably formed to be 15 to 35% thicker than the thickness d of the insulating coating layer 17 at the intermediate portion. When the thickness D of the insulating coating layer 17a at the width direction end is less than 15% of the thickness d of the insulating coating layer 17 at the intermediate portion, the thickness of the insulating coating layer at the width direction end is insufficient. It becomes difficult to suppress delamination of the superconducting wire 11 due to stress such as bending stress. On the other hand, if it exceeds 35%, delamination of the superconducting wire 11 due to stress such as bending stress cannot be further suppressed, and it becomes difficult to form the insulating coating layer 17a uniformly.

  Moreover, it is preferable that the thickness D of the insulation coating layer 17a in the edge part of the width direction of the superconducting wire 11 is 15-100 micrometers. When the thickness D of the insulating coating layer 17a is less than 15 μm, the thickness D of the insulating coating layer 17a is insufficient, and it becomes difficult to sufficiently suppress delamination of the superconducting wire 11 due to stress. On the other hand, if the thickness exceeds 100 μm, the effect of increasing the thickness of the insulating coating layer 17a at the end in the width direction cannot be expected any more, and it becomes difficult to form the insulating coating layer 17a uniformly.

  As shown in FIGS. 3A and 3B, a superconducting coil (pancake coil) 20 is formed by winding a tape-shaped superconducting wire 11 into a cylindrical shape. Electrodes (not shown) are connected to each other. In this case, the superconducting coil 20 can be easily formed by using a cylindrical inner peripheral frame (not shown) and winding the superconducting wire 11 around the outer periphery. The insulating coating layers 17 and 17a are formed by coating the outer peripheral surface of the superconducting coil 20 with a synthetic resin for the insulating coating layers 17 and 17a by a coating method or an electrodeposition method. In the coating method, the synthetic resin is heated and melted and applied to the outer periphery of the superconducting wire 11, and in the electrodeposition method, the synthetic resin is charged to cover the outer peripheral surface of the superconducting wire 11 having the opposite charge. In addition, by disposing an outer peripheral frame (not shown) on the outer periphery of the superconducting coil 20, when the superconducting coil 20 receives a hoop stress (electromagnetic stress) due to a high magnetic field, the diameter of the superconducting coil 20 can be suppressed.

Next, an effect | action is demonstrated about the superconducting wire 11 comprised as mentioned above.
Now, the thickness D of the insulating coating layer 17a at the end portion in the width direction of the superconducting wire 11 of the present embodiment is configured to be thicker than the thickness d of the insulating coating layer 17 at the intermediate portion, and the superconducting wire rod at the end portion in the width direction. 11 holding power is increased. For this reason, the stress based on the difference in the thermal expansion coefficient received when cooling the superconducting coil 20 with liquid helium, liquid nitrogen, etc. acted on the superconducting wire 11 when manufacturing the superconducting coil 20 from the superconducting wire 11. At that time, the stress is sufficiently received and buffered at the end of the superconducting wire 11 in the width direction, and the original shape of the superconducting wire 11 is maintained. Therefore, it is avoided that the superconducting wire 11 becomes the starting point of peeling of each layer of the superconducting wire 11, particularly the superconducting layer 14, at the end in the width direction of the superconducting wire 11.

  Further, the outer surface of the insulating coating layer 17a at the end portion in the width direction of the superconducting wire 11 is constituted by a curved surface 17b having an arc shape. Therefore, when the superconducting coil 20 is used as a high magnetic field magnet or the like, when the superconducting wire 11 receives an electric field, there is no edge in the insulating coating layer 17a at the widthwise end of the superconducting wire 11, and the electric field is dispersed. , Local concentration of the electric field is avoided.

The effects obtained by the first embodiment described in detail above are collectively described below.
(1) The superconducting wire 11 according to the first embodiment is configured such that the thickness D of the insulating coating layer 17a at the end in the width direction is greater than the thickness d of the insulating coating layer 17 at the intermediate portion. . For this reason, when a stress such as a bending stress acts on the superconducting wire 11, the insulating coating layer 17a formed in the thickness of the end portion in the width direction of the superconducting wire 11 absorbs the stress, and the superconducting wire 11 has the original shape. It can hold | maintain and generation | occurrence | production origin of peeling of the superconducting layer 14 is suppressed in the width direction edge part.

Therefore, according to the insulation coating structure of the superconducting wire 11 of the first embodiment, delamination of the superconducting wire 11 can be suppressed, and the superconducting characteristics can be maintained well.
(2) The thickness D of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 is 15 to 35% thicker than the thickness of the insulating coating layer 17 at the intermediate portion. For this reason, the effect of suppressing delamination of the superconducting wire 11 based on the thick portion of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 can be sufficiently obtained.
(3) The thickness of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 is set to 15 to 100 μm. In this case, the thickness of the insulating coating layer 17a at the end portion in the width direction of the superconducting wire 11 can be sufficiently ensured, and particularly, the original shape can be maintained by sufficiently dealing with bending stress and stress at the time of cooling. And delamination of the superconducting wire 11 can be satisfactorily suppressed.
(4) The outer surface of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 is composed of a curved surface 17b having an arcuate cross section. For this reason, when an electric field is received when the superconducting coil 20 is used with the superconducting wire 11, there is no edge on the outer surface of the insulating coating layer 17a at the widthwise end of the superconducting wire 11, and the electric field is in the widthwise end of the superconducting wire 11. It is possible to suppress concentration on the screen.
(5) The insulating coating layers 17 and 17a are formed of a synthetic resin whose main component is a polyimide resin. Therefore, the original shape can be sufficiently retained against bending stress and cooling stress, and the outer surface of the insulating coating layer 17a at the end in the width direction of the superconducting wire 11 can be easily shaped into a curved shape. And concentration of the electric field can be easily suppressed.
(Second Embodiment)
Next, a second embodiment in which the insulation coating structure of the superconducting wire 11 of the present invention is embodied will be described with reference to the drawings. In the second embodiment, portions that are different from the first embodiment will be mainly described, and description of overlapping portions will be omitted.

  As shown in FIG. 1B, the second stabilizing layer 16 covers the entire periphery of the substrate 12, the intermediate layer 13, the superconducting layer 14, and the first stabilizing layer 15 by plating with a metal such as copper. It is configured. The second stabilization layer 16 is formed with a thickness of about 100 μm, for example. The insulating coating layers 17 and 17a are formed so as to cover the second stabilization layer 16, and are formed in a circular arc shape in cross section so that both end portions in the width direction of the superconducting wire 11 are thicker than the intermediate portion.

In the second embodiment, the second stabilization layer 16 is configured to cover the entire circumference of the substrate 12, the intermediate layer 13, the superconducting layer 14, and the first stabilization layer 15, and the insulating coating layers 17, 17a. Is formed so as to cover the entire circumference of the second stabilization layer 16. For this reason, the stress and electric field acting on the end portion in the width direction of the superconducting wire 11 are less likely to reach the layers such as the superconducting layer 14 as compared with the case of the first embodiment. Therefore, delamination and dielectric breakdown of the superconducting wire 11 can be further suppressed as compared with the case of the first embodiment, and the superconducting characteristics can be maintained better.
(Third embodiment)
Next, a third embodiment that embodies the insulation coating structure of the superconducting wire 11 of the present invention will be described with reference to the drawings. In the third embodiment, portions that are different from the second embodiment will be mainly described, and descriptions of overlapping portions will be omitted.

  As shown in FIG. 2, the superconducting wire 11 of the third embodiment is obtained by cutting the superconducting wire 11 of the second embodiment in the longitudinal direction at an intermediate portion in the width direction, and the end portion in the width direction cut and processed. Insulating coating layers 17 and 17a are coated. The insulating coating layers 17 and 17 a are formed so as to cover the substrate 12, the intermediate layer 13, the superconducting layer 14, the first stabilization layer 15, and the second stabilization layer 16. The insulating coating layers 17 and 17a are formed so as to cover the second stabilization layer 16 at one end in the width direction of the superconducting wire 11, and so as to cover the cut surface at the other end.

  Therefore, according to the third embodiment, the effect of the second embodiment can be obtained at one end of the superconducting wire 11 in the width direction, and the effect of the first embodiment can be obtained at the other end. Therefore, even when the superconducting wire 11 is cut in the longitudinal direction at the intermediate portion in the width direction and thinned, delamination and dielectric breakdown of the superconducting wire 11 can be effectively suppressed, and the superconducting characteristics can be maintained well. Can do.

Below, the superconducting characteristic was measured and evaluated about the superconducting wire 11 of the said 1st Embodiment-3rd Embodiment.
Example 1
In Example 1, a single pancake coil having an inner diameter of 50 mm was manufactured using the superconducting wire 11 having the shape of the first embodiment and the superconducting wire 11 having a width of 10 mm and a length of 6 m. This single pancake coil was subjected to 10 cycles of cooling and heating between liquid nitrogen (77K) and room temperature, and then the current-carrying characteristics (current-voltage curve) were measured in liquid nitrogen to evaluate the critical current and n value. did. For comparison, a similar test was performed on a single pancake coil that was not subjected to a thermal cycle. In addition, n value shows the exponent of the exponential function in the critical current vicinity of a current-voltage curve, and is a numerical value which judges the quality as a superconducting wire.

As a result, n value showed 21-23 and was favorable as the superconducting wire 11. In addition, the results of the energization characteristics are shown in FIG.
In FIG. 4, “x” indicates the result of the single pancake coil subjected to the cooling cycle, and “Δ” indicates the result of the single pancake coil not subjected to the cooling cycle.

From the results shown in FIG. 4, the single pancake coil that was subjected to the thermal cycle was able to obtain almost the same characteristics as the single pancake coil that was not subjected to the thermal cycle, and the superconducting characteristics were maintained even after repeated stress. .
(Example 2)
In Example 2, a single pancake coil having an inner diameter of 50 mm was manufactured using the superconducting wire 11 having the shape of the second embodiment and the superconducting wire 11 having a width of 10 mm and a length of 6 m. About this single pancake coil, after repeating the cooling-heating cycle similarly to Example 1, the current-carrying characteristics were measured in liquid nitrogen, and the critical current and the n value were measured and evaluated. For comparison, a similar test was performed on a single pancake coil that was not subjected to a thermal cycle. As a result, n value showed 22-23 and was favorable as the superconducting wire 11. In addition, the results of the energization characteristics are shown in FIG.

In FIG. 5, “x” indicates the result of the single pancake coil that was subjected to the cooling cycle, and “Δ” represents the result of the single pancake coil that was not subjected to the cooling cycle.
From the results shown in FIG. 5, the single pancake coil that was subjected to the cooling and heating cycle obtained characteristics substantially equivalent to the single pancake coil that was not subjected to the cooling and heating cycle, and the superconducting characteristics were maintained.
(Example 3)
In Example 3, a single pancake coil having an inner diameter of 50 mm was manufactured using the superconducting wire 11 having the shape of the third embodiment and a width of 5 mm and a length of 6 m. About this single pancake coil, after carrying out the cooling-heat cycle 5 times or 10 times similarly to Example 1, the electricity supply characteristic was measured in liquid nitrogen, and the critical current and n value were measured and evaluated. For comparison, a similar test was performed on a single pancake coil that was not subjected to a thermal cycle. As a result, the n value was 18 to 21, and it was good as the superconducting wire 11. In addition, the results of the energization characteristics are shown in FIG.

  In FIG. 6, ◯ indicates the result of the single pancake coil that was subjected to the cooling cycle 5 times, the broken line indicates the result of the single pancake coil that was subjected to the cooling cycle 10 times, and × represents the single pancake that was not subjected to the cooling cycle Coil results are shown.

  From the results shown in FIG. 6, the single pancake coil that had been subjected to the thermal cycle 5 or 10 times had substantially the same characteristics as the single pancake coil that was not subjected to the thermal cycle.

It should be noted that the embodiments described above can be modified and embodied as follows.
-As shown to Fig.7 (a), you may form the insulation coating layer 17a in the width direction edge part of the superconducting wire 11 so that a cross section may become a substantially square shape. However, the corner portion of the insulating coating layer 17a is chamfered (rounded) so as not to become an edge.

  -As shown in FIG.7 (b), you may form the insulation coating layer 17a in the width direction edge part of the superconducting wire 11 so that it may become a cross-sectional fan shape. However, the corner portion of the insulating coating layer 17a is chamfered (rounded) so as not to become an edge.

-You may comprise so that the shape, thickness, etc. of the insulation coating layer 17a in the one end part of the width direction of the said superconducting wire 11 may differ from the insulation coating layer 17a in the other end part.
The insulating coating layer 17a at the end in the width direction of the superconducting wire 11 may be formed by stacking two or more layers using different synthetic resins.

  -You may comprise so that the thickness of the insulating coating layer 17a in the width direction edge part of the said superconducting wire 11 may become uniform on the whole.

  DESCRIPTION OF SYMBOLS 11 ... Superconducting wire, 12 ... Board | substrate, 13 ... Intermediate | middle layer, 14 ... Superconducting layer, 15 ... 1st stabilization layer, 16 ... 2nd stabilization layer, 17, 17a ... Insulation coating layer, 17b ... Curved surface, D ... Width The thickness of the insulating coating layer at the end in the direction, d... The thickness of the insulating coating layer at the intermediate portion in the width direction.

Claims (6)

A superconducting layer of a rare earth oxide superconductor is formed on a substrate via an intermediate layer, a stabilization layer is formed on the superconducting layer, and an insulating coating layer is formed on the outer periphery thereof. A superconducting wire insulation coating structure,
An insulation coating structure for a superconducting wire, characterized in that the thickness of the insulation coating layer at the end in the width direction of the superconducting wire is greater than the thickness of the insulation coating layer at the intermediate portion. 2. The superconducting wire according to claim 1, wherein a thickness of the insulating coating layer at an end portion in the width direction of the superconducting wire is formed to be 15 to 35% thicker than a thickness of the insulating coating layer in an intermediate portion. Insulation coating structure. The insulation coating structure for a superconducting wire according to claim 1 or 2, wherein a thickness of the insulation coating layer at an end portion in the width direction of the superconducting wire is 15 to 100 µm. The insulation coating structure for a superconducting wire according to any one of claims 1 to 3, wherein an outer surface of the insulation coating layer at an end portion in the width direction of the superconducting wire is configured by a curved surface. The insulation coating structure for a superconducting wire according to claim 4, wherein an outer surface of the insulation coating layer at an end portion in the width direction of the superconducting wire is formed in an arc shape in cross section. The insulation coating structure for a superconducting wire according to any one of claims 1 to 5, wherein the insulation coating layer is made of a synthetic resin containing a polyimide resin as a main component.