JP6442334B2 - Superconducting wire inspection method and manufacturing method - Google Patents

Description

  The present invention relates to a superconducting wire inspection method and a superconducting wire manufacturing method using the same.

As a structure of a superconducting wire using a Y-based oxide superconductor represented by REBa ₂ Cu ₃ O _7-x (RE123, RE: rare earth element), a superconducting layer is formed on a base material such as a metal tape via an intermediate layer. A structure in which a protective layer for protecting the superconducting layer is formed after the film is formed is known. The superconducting layer is likely to be deteriorated by moisture and has been devised such as plating on the outer periphery or covering with a copper foil or the like.

  When the superconducting wire is coated with a protective layer, plating, copper foil or the like, the superconducting wire is processed while being transported in the longitudinal direction by restraint, so that the coating may be broken during the processing. If there is a torn portion (opening portion) in the coating protecting the superconducting wire, there is a problem that moisture enters from the opening portion and the superconducting layer causes a chemical reaction to deteriorate the superconducting characteristics. As in the pressure cooker test (see Patent Document 1), by exposing the superconducting wire to high temperature and high humidity, it is possible to significantly deteriorate the superconducting layer from the opening and detect the position of the opening. However, if deterioration occurs to the normal part, the superconducting wire that has been inspected may not be able to be used normally.

JP 2014-17090 A

  This invention is made | formed in view of the said situation, and makes it a subject to provide the inspection method and manufacturing method of an oxide superconducting wire which can use a superconducting wire even if it implements a test | inspection.

  In order to solve the above-mentioned problems, the present invention is a method for inspecting a superconducting wire including an oxide superconductor and a coating, wherein after the superconducting wire is brought into contact with an acidic liquid, the critical current of the superconducting wire is measured. Accordingly, the present invention provides a method for inspecting a superconducting wire characterized by identifying the presence or absence of a location where the oxide superconductor has deteriorated in contact with the acidic liquid or the location of the location.

The step of bringing the superconducting wire into contact with an acidic liquid may include a step of immersing the superconducting wire in an acidic liquid.
After the superconducting wire is brought into contact with the acidic liquid, the superconducting wire brought into contact with the acidic liquid may be heated before the critical current value of the superconducting wire is measured.
In the step of heating the superconducting wire, the acidic liquid in contact with the superconducting wire may be concentrated.

The present invention also provides a method for producing a superconducting wire comprising an oxide superconductor and a coating, the method comprising inspecting a superconducting wire by the method for inspecting a superconducting wire. provide.
You may have the process of removing the location which the said oxide superconductor deteriorated after the said process to test | inspect.

  According to the present invention, when there is a defective portion such as an opening in the coating, by contacting the acidic liquid, the deterioration of the oxide superconductor at that portion is promoted, whereby the presence or absence of the defective portion or its position is determined. Can be identified.

It is explanatory drawing which illustrates the process of immersing a coil-shaped superconducting wire in a liquid. It is explanatory drawing which illustrates the process of immersing in a liquid, conveying a superconducting wire.

Hereinafter, the present invention will be described based on preferred embodiments.
The superconducting wire inspection method of this embodiment includes a step of bringing the superconducting wire into contact with an acidic liquid. When the superconducting wire is brought into contact with the acidic liquid, the acidic liquid enters from a portion where the coating is broken. When the oxide superconductor is in contact with an acidic liquid, the deterioration is promoted more than when it is in contact with moisture. By measuring the critical current of the superconducting wire, it is possible to specify the presence or absence of a portion where the oxide superconductor has deteriorated, and the position of the portion.

  The process of bringing a superconducting wire into contact with an acidic liquid includes a process of immersing the superconducting wire in an acidic liquid, a process of applying an acidic liquid to the superconducting wire, a process of pouring an acidic liquid into the superconducting wire, and an acid in the superconducting wire. And a step of spraying the liquid. When contacting the liquid, the superconducting wire may be transported or stopped. As the kind of the acidic liquid, one in which the oxide superconductor causes a chemical reaction and has a small influence on the coating of the superconducting wire or the base material is preferable. An acidic liquid is preferable because it easily deteriorates the oxide superconductor than water. It is also possible to use a corrosive gas such as an acidic gas. However, if a corrosive liquid such as an acidic liquid is used, it is less likely to penetrate the coating (a normal part that does not break) compared to the gas. It is possible to suppress the deterioration of various parts.

  Examples of the acidic liquid include a liquid containing an acid and a substance other than the acid (such as a solution), and a liquid containing only the acid (the acid itself is a liquid). Examples of the acid (acidic substance) include inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, and organic acids such as carboxylic acid, sulfonic acid, and phosphonic acid. When an acid solution or the like is used, the acid itself may be solid or gas. Examples of the acid include non-volatile acids, volatile acids, strong acids, weak acids, oxidizing acids, reducing acids, and the like. Depending on the reactivity, the acid concentration, liquid temperature, flow rate, and the like may be adjusted as appropriate. Examples of the solvent for the acidic solution include water and organic solvents. The solvent may be a mixed solvent of two or more. As the organic solvent, polar solvents such as alcohol (hydroxy compound), ether, ketone, ester and the like are preferable.

  After immersing the superconducting wire in an acidic liquid for a certain period of time, it is preferable to wash the superconducting wire with water or a cleaning agent that is less likely to degrade the oxide superconductor. The process of cleaning the superconducting wire includes the step of immersing the superconducting wire in the cleaning agent, the step of applying the cleaning agent to the superconducting wire, the step of pouring the cleaning agent on the superconducting wire, the step of spraying the cleaning agent on the superconducting wire, etc. Can be mentioned. Examples of the cleaning agent include liquids such as organic solvents. As the organic solvent, polar solvents such as alcohol (hydroxy compound), ether, ketone, ester and the like are preferable. The solvent may be a mixed solvent of two or more. In the cleaning process, all of the acidic liquid adhering to the superconducting wire may be removed. Or you may remove the acidic liquid adhering to the coating | coated surface etc., leaving the acidic liquid which remained in the location with a tearing of a coating | cover.

  The configuration in the case where the superconducting wire is immersed in an acidic liquid or a cleaning liquid is illustrated in FIGS. FIG. 1 shows a step of immersing a coiled superconducting wire 10 in a liquid 21 in a bathtub 20. Two or more coils may be simultaneously immersed in the bath. In order to support the coil, a support jig (not shown) such as a frame or a shelf may be used. Moreover, FIG. 2 shows the process of immersing the superconducting wire 11 in the liquid 21 in the bathtub 20 while continuously conveying in the longitudinal direction. Two or more rollers 12 for guiding the superconducting wire 11 may be installed in the bathtub 20 and the superconducting wire 11 may be immersed in the liquid 21 over a longer distance. The liquid 21 in the bathtub 20 may be left still. Or in order to promote the contact with the liquid 21 and the superconducting wire 11, you may implement the application of an ultrasonic wave, stirring, shaking (vibration), etc.

  You may have the process of heating the superconducting wire contacted with the acidic liquid, after contacting the superconducting wire with the acidic liquid and before measuring the critical current value of the superconducting wire. The heating step promotes a chemical reaction with the acidic liquid and promotes deterioration of the oxide superconductor. The heating step can be performed before, during or after the step of cleaning the superconducting wire. In the case where the heating step is performed after the cleaning step, the acidic liquid remaining in the portion where the coating is broken may be concentrated in the heating step. As a result, the reactivity of the acidic liquid is increased, and deterioration of the oxide superconductor can be locally promoted. The heating temperature can be appropriately adjusted in consideration of the influence (effect) on the action of the acid and the influence on the superconducting wire, and examples thereof include 60 to 100 ° C.

  After the oxide superconductor is deteriorated with an acidic liquid at a location where the coating is broken, the presence or absence or location of the deteriorated location can be specified. For example, when the critical current is measured by the magnetization method, the position of the deteriorated portion can be specified by converting the response of the weak magnetic field along the longitudinal direction into the critical current by the measurement program. Further, for example, when the method for measuring the critical current is to determine whether or not the superconducting current flows over the entire length of the superconducting wire, it is possible to specify the presence / absence of the deterioration portion.

  The superconducting wire inspection method of the present embodiment can be implemented by being incorporated into the superconducting wire manufacturing process. A superconducting wire with high reliability can be manufactured by identifying the deteriorated part of the oxide superconductor through the inspection process of the superconducting wire and confirming that there is no deteriorated part or removing the deteriorated part. . By eliminating the deteriorated part of the oxide superconductor through inspection, it is possible to obtain a superconducting wire that does not have a coating breakage (opening), so that deterioration of the characteristics of the superconducting wire due to intrusion of moisture during use can be suppressed. .

The superconducting wire to which the present invention is applicable is not particularly limited as long as it includes an oxide superconductor and a coating covering the oxide superconductor. Examples of the oxide superconductor include a Y-based superconductor represented by a general formula REBa ₂ Cu ₃ O _7-X (RE123), a general formula Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} (Bi2212), or Bi ₂ Sr ₂ Ca. A Bi-based superconductor represented by ₂ Cu ₃ O _{10 + δ} (Bi2223) can be given. Examples of the coating include one or more of a protective layer, a plating layer, a solder layer, a stabilizing layer, a stabilizing material, a metal tape, and the like.

  As a structure of a superconducting wire using a Y-based superconductor as an oxide superconductor, a laminate (superconducting laminate) including a base material and a superconducting layer is provided. Further, around the superconducting layer or the superconducting laminate, The structure further covered with 1 type (s) or 2 or more types, such as plating, solder, a stabilizing material, a metal tape, is mentioned. Part or all of the substrate (such as the back surface) may be exposed outside the coating, but it is preferable that each surface (upper surface and end surfaces on both sides in the width direction) other than the substrate side of the superconducting layer is covered with the coating. . Examples of the superconducting laminate include a configuration in which a tape-like base material, an intermediate layer, a superconducting layer, and a protective layer are laminated in this order. The substrate is tape-shaped, for example, a metal substrate. Specific examples of the metal constituting the substrate include nickel alloys typified by Hastelloy (registered trademark), stainless steel, and oriented Ni—W alloys in which a texture is introduced into the nickel alloy.

  The intermediate layer is provided between the base material and the superconducting layer. The intermediate layer 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 side to the superconducting layer side. These layers are not necessarily provided one by one, and some layers may be omitted, or two or more of the same kind of layers may be laminated repeatedly.

Examples of the material for the diffusion preventing layer include Si ₃ N ₄ , Al ₂ O ₃ , GZO (Gd ₂ Zr ₂ O ₇ ), and the like.
Examples of the material of the bed layer include Y ₂ O ₃ , Er ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , and La ₂ O ₃ .
Examples of the material of the alignment layer include Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , Examples thereof include metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ . This alignment layer is preferably formed by an IBAD (Ion-Beam-Assisted Deposition) method.
The material of the cap layer, for _{example, CeO 2, Y 2 O 3} , Al 2 O 3, Gd 2 O 3, ZrO 2, YSZ, Ho 2 O 3, Nd 2 O 3, LaMnO 3 , and the like.

  The superconducting layer (oxide superconducting layer) is composed of an oxide superconductor. Although it does not specifically limit as an oxide superconductor, The above-mentioned Y type oxide superconductor is mentioned. Examples of the rare earth element RE include one or more of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is done. The superconducting layer is formed by sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, pulsed laser deposition (PLD), chemical vapor deposition (CVD), metal organic coating pyrolysis (MOD), etc. Can be laminated.

  The protective layer has functions such as bypassing overcurrent generated at the time of an accident and suppressing a chemical reaction occurring between the superconducting layer and the layer provided on the protective layer. Examples of the material for the protective layer include silver (Ag), gold (Au), an alloy of gold and silver, other silver alloys, and gold alloys.

  Examples of the stabilizing material include highly conductive metals such as copper, copper alloys, aluminum and aluminum alloys, and Ni-based alloys such as Ni-Cr. The highly conductive metal can function as a bypass that commutates an overcurrent that is generated at the time of transition to the normal conducting state. The high resistance metal can instantaneously suppress the overcurrent generated at the time of transition to the normal conducting state in a superconducting current limiting device or the like. The stabilizing material may be bonded to the superconducting laminate by a bonding material. Examples of the material constituting the bonding material include Sn—Pb, Pb—Sn—Sb, Sn—Pb—Bi, Bi—Sn, Sn—Cu, Sn—Pb—Cu, and Sn—Ag. Examples thereof include metals such as solder, Sn, Sn alloy, In (indium), and In alloy. The stabilizing material may be formed on the superconducting laminate as a stabilizing layer by plating or the like via the bonding material or without the bonding material.

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.
A superconducting cable, a superconducting coil, etc. can be produced using a superconducting wire. For example, in order to manufacture a superconducting coil, a superconducting wire is wound around the outer peripheral surface of the winding frame to form a coil shape (multilayer winding coil) and then a resin such as an epoxy resin so as to cover the wound superconducting wire. Can be impregnated to fix the superconducting wire.

Example 1
An intermediate film was formed on the tape-shaped metal substrate using the IBAD method or the like. A superconducting layer (GdBa ₂ Cu ₃ O _X layer) having a thickness of about 2 μm was formed thereon by the PLD method, and then a silver layer was formed by the sputtering method. A tape-shaped copper foil having a thickness of 20 μm was bonded to the superconducting laminate thus obtained with solder. At this time, in order to protect edge portions (both ends in the width direction) of the superconducting layer, the copper foil was processed so as to cover both side surfaces of the superconducting laminate, thereby producing a superconducting wire having a coating.

  In order to inspect the superconducting wire, the superconducting wire was wound into a pancake, placed in a container filled with sulfuric acid (concentration 5%), and immersed for 1 hour. Thereafter, the superconducting wire was taken out, washed with running water, and then dried by blowing. The dried superconducting wire was placed in an electric furnace and held at 80 ° C. for 1 hour to perform heat treatment. The critical current value in the longitudinal direction of the superconducting wire after the heat treatment was measured by a magnetization method using a Hall sensor. As a result, four locations where the characteristics (critical current values) were locally lowered were found for the superconducting wire having a length of about 300 m. When the periphery of these portions was cut out and observed with a microscope, an opening (coating breakage) of about 0.1 to 0.2 mm was found in the copper foil covering the surface of the superconducting wire.

  On the other hand, when a critical cooker test was performed on a portion where no characteristic deterioration was found by measurement (normal part), the critical current was measured again, and no characteristic deterioration was found. It can be said that the portions where no local characteristic degradation was found by the first measurement were not broken, and the internal superconducting layer was reliably protected.

(Comparison 1)
The inspection was carried out in the same manner as in Example 1 except that instead of sulfuric acid (5%), only water was put in a container and the superconducting wire was immersed. Although a local degradation point was found in the critical current measurement, the degree of degradation is small, and it is difficult to say that the coating breakage point can be reliably detected. Therefore, it can be said that it is desirable to use a liquid having high reactivity with the superconducting layer as in Example 1.
From the above results, it was confirmed that the normal part of the superconducting wire was not affected and the position where the coating was broken could be identified from the decrease in the critical current value.

(Example 2)
A superconducting wire was produced in the same manner as in Example 1. A treatment tank with a length of about 3 m filled with sulfuric acid (5%) and a washing tank filled with water for washing the superconducting wire were placed adjacent to each other, and the two tanks were passed while conveying the superconducting wire in the longitudinal direction. . The conveyance speed was set to 10 m / min, and ultrasonic waves were applied to all the tanks to promote liquid contact and reaction. The superconducting wire after washing was dried by blowing and wound on a winding reel.
The wound superconducting wire was put into an electric furnace and heat-treated in the same manner as in Example 1, and the critical current value in the longitudinal direction was measured. As a result, deterioration was found in a plurality of locations in the longitudinal direction. Moreover, the opening part of the coating | cover was able to be specified similarly to Example 1 about these deterioration locations. Therefore, it was confirmed that the position where the coating was broken could be specified even by the method of immersing the superconducting wire in the liquid while transporting it.

DESCRIPTION OF SYMBOLS 10 ... Coiled superconducting wire, 11 ... Superconducting wire, 12 ... Roller, 20 ... Bathtub, 21 ... Liquid.

Claims (6)

A method for inspecting a superconducting wire including an oxide superconductor and a coating,
After contacting the superconducting wire with an acidic liquid, by measuring the critical current of the superconducting wire, the presence or absence of a location where the oxide superconductor deteriorates due to contact with the acidic liquid is determined. A superconducting wire inspection method characterized by specifying.   The method for inspecting a superconducting wire according to claim 1, wherein the step of bringing the superconducting wire into contact with an acidic liquid includes a step of immersing the superconducting wire in an acidic liquid.   The step of heating the superconducting wire brought into contact with the acidic liquid after contacting the superconducting wire with the acidic liquid and before measuring a critical current value of the superconducting wire. The superconducting wire inspection method according to 1 or 2.   The method for inspecting a superconducting wire according to claim 3, wherein in the step of heating the superconducting wire, the acidic liquid in contact with the superconducting wire is concentrated. A method of manufacturing a superconducting wire including an oxide superconductor and a coating,
A method for manufacturing a superconducting wire, comprising a step of inspecting a superconducting wire by the method for inspecting a superconducting wire according to any one of claims 1 to 4.   6. The method of manufacturing a superconducting wire according to claim 5, further comprising a step of removing a portion where the oxide superconductor has deteriorated after the step of inspecting.

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