JP2011008949A - Superconductive wire rod and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconductive wire rod with excellent superconductive characteristics, capable of suppressing intrusion of moisture into a superconductive layer and moreover suppressing deterioration of a critical current density by having a structure with which it hardly gets external mechanical or chemical damages, and provide a simple manufacturing method of the same.SOLUTION: The superconductive wire rod 100 is provided at least with a first base body 10 on which an intermediate layer 2, a superconductive layer 3, and a protective layer 4 are superimposed in order on one of the faces of a first base material 1 of a lengthy shape and a second base body 20 which is superimposed on the protective layer 4 and is made of a second base material 5 of a lengthy shape composed of a stabilizing material. On a face opposed to the protective layer 4 of the second base body 20, there is arranged a recess part continuing in the length direction, and an inner bottom face of the recess part is jointed with the protective layer 4 with a conductive jointing member 6 interposed, and moreover, the superconductive layer 3 is arranged so that its side face can be accommodated entirely in the recess part.

Description

  The present invention relates to a long superconducting wire that is being developed and applied to a superconducting power cable, a superconducting magnet, a superconducting energy storage device, a superconducting power generation device, a medical MRI device, a superconducting current lead, and the like.

  Conventionally, a superconducting conductor is formed by forming an oxide superconducting layer on a tape-like substrate by a film forming method such as a laser vapor deposition method or a CVD method. A thin-film oxide superconducting layer formed by this kind of film-forming method is known to exhibit a higher critical current density (Jc) than a powder conductor of a constituent element of a conventionally known oxide superconductor. ing. In addition, this type of superconducting conductor is said to have a small deterioration rate of superconducting characteristics due to the magnetic field when it is cooled to liquid nitrogen temperature (77K) to be in a superconducting state and a magnetic field is applied. Attempts have been made to produce a small and lightweight superconducting magnet by performing coil processing using a tape-shaped oxide superconducting conductor.

When an oxide superconducting layer is directly formed on a long substrate such as a metal tape, there is a problem that the crystal orientation is disturbed and good superconducting properties cannot be obtained. An in-plane oriented intermediate layer such as MgO, SrTiO ₃ , Gd ₂ Zr ₂ O ₇ , CeO ₂ , yttrium stabilized zirconia (YSZ) is formed, and an oxide superconducting layer is formed on the intermediate layer. A structure is used in which an oxide superconducting layer having excellent crystal orientation is arranged on a long base material such as a metal tape by forming a film.
By forming such an intermediate layer between the metal tape and the oxide superconducting layer, the accumulation of thermal strain due to the difference in thermal expansion coefficient can also be reduced, and the gap between the oxide superconducting layer and the metal tape can be reduced. Therefore, the oxide superconducting conductor provided with the oxide superconducting layer having excellent characteristics can be obtained.

However, if a long oxide superconductor is bent to produce a superconducting coil, strain is applied to the superconducting layer, which reduces the critical current density and thus degrades the superconducting characteristics. there were.
Therefore, the inventors of the present invention provided an intermediate layer on a metal tape made of Hastelloy or the like, and a superconducting layer made of a superconductor of ReBaCuO type (Re is a rare earth element such as Gd, Y, Ho, or Sn) among oxide superconductors. Various attempts have been made to produce long superconducting conductors having excellent superconducting characteristics by forming them sequentially and forming a highly conductive stabilized metal layer on the superconducting layer.

Among such attempts, the present inventors, for example, in Patent Document 1, by optimizing the material and thickness of the stabilizing metal layer, the superconducting layer is hardly strained even when bending is performed. We have found a configuration that does not easily cause degradation of superconducting properties.
FIG. 3 is a schematic view showing a structural example of a conventional oxide superconducting conductor. In the oxide superconducting conductor 200, an intermediate layer 202, a superconducting layer 203 made of a YBaCuO-based superconductor, and a highly conductive stabilizing layer 204 are sequentially laminated on a long base material 201 such as Hastelloy tape.
However, in this configuration, since the side surface of the superconducting layer 203 that is easily damaged by moisture is exposed to the outside, the penetration of moisture during the manufacturing process or the like may cause deterioration of superconducting characteristics.

  On the other hand, for example, Patent Documents 2 and 3 describe a configuration in which a superconducting layer is sandwiched between metal tapes, and the metal tape is filled and joined with a joining member such as solder. In such a configuration, the side surface of the superconducting layer is not exposed to the outside, but in order to obtain sufficient bonding strength, a step of pressing and bonding the superconducting wire from the thickness direction is required. In that case, the superconducting layer may be damaged by the pressure applied in the thickness direction of the superconducting wire, and the superconducting characteristics may be deteriorated.

Japanese Unexamined Patent Publication No. 7-73758 Japanese Patent No. 3949960 JP 2008-243588 A

The present invention has been made in view of the above circumstances, and has a structure that suppresses the penetration of moisture into the superconducting layer and is resistant to mechanical or chemical damage from the outside, thereby reducing the critical current density. It is a first object to provide a superconducting wire that can be suppressed and consequently has good superconducting properties.
The second object of the present invention is to provide a method for producing a superconducting wire that can easily and stably form the above-described superconducting wire having good superconducting properties.

  In order to solve the above-mentioned problem, a superconducting wire according to claim 1 of the present invention is formed by stacking an intermediate layer, a superconducting layer, and a protective layer in this order on one surface of a long first base material. And at least a second substrate made of a long second substrate made of a stabilizing material and overlying the protective layer, the surface of the second substrate facing the protective layer A concave portion that is continuous in the longitudinal direction is disposed, the inner bottom surface of the concave portion is bonded to the protective layer via a conductive bonding member, and the side surfaces of the superconducting layer are all in the concave portion. It is characterized by being arranged to fit.

The superconducting wire according to claim 2 of the present invention is the superconducting wire according to claim 1, wherein the other surface of the first base is the same height as or lower than the surface of the second base on which the recess is formed. It is configured.
The superconducting wire according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the joining member is arranged so as to further cover the side surface of the superconducting layer.

  A method for producing a superconducting wire according to claim 4 of the present invention includes a first substrate formed by stacking an intermediate layer, a superconducting layer, and a protective layer in this order on one surface of a long first substrate; A manufacturing method comprising at least a second base made of a long second base material made of a stabilizing material and overlapping the protective layer, wherein the intermediate layer is formed on one surface of the first base material. , A superconducting layer and a protective layer are sequentially stacked to form the first substrate, a step A is formed in the longitudinal direction of the second substrate, and a step B is formed to form the second substrate. A step C in which a bonding member is sandwiched and disposed between the inner bottom surface of the concave portion provided on the base and the surface of the protective layer constituting the first base, and heating and pressure treatment are performed, and both are bonded. And at least step D.

The method for producing a superconducting wire according to claim 5 of the present invention is characterized in that, in claim 4, before the step D, the method includes a step E of performing preheating.
The method of manufacturing a superconducting wire according to claim 6 of the present invention is the method according to claim 4 or 5, wherein when the step C is performed, the other surface of the first base material forms the concave portion of the second base material. It is characterized in that it is arranged so as to be the same height or lower than the formed surface.
A superconducting wire manufacturing method according to a seventh aspect of the present invention is the superconducting wire according to any one of the fourth to sixth aspects, wherein when the step D is performed, the joining member is at least together with the inner bottom surface of the recess. Heating and pressurizing treatment is performed so as to cover the side portion of the.

  The superconducting wire according to the present invention (Claim 1) is arranged such that the entire side surface of the superconducting layer forms a recess by being disposed so that all the side surfaces of the superconducting layer are accommodated in the recess disposed on the second substrate. It is possible to realize a configuration that is surrounded by a material or invisible from the outside, and that the entire side surface of the superconducting layer is shielded from the outside. Such a configuration can prevent moisture from entering the superconducting layer, prevent chemical damage to the superconducting layer, and also has an effect of suppressing external mechanical influence on the superconducting layer. Thereby, since the reduction of the critical current density can be suppressed, the present invention contributes to provision of a superconducting wire having good superconducting characteristics.

  The method for manufacturing a superconducting wire according to the present invention (Claim 4) separately forms a first substrate that is a laminate including a superconducting layer and a second substrate made of a stabilizing material and provided with a recess, By using the process of joining the two, first, the two are separately manufactured under optimum conditions, and then can be integrated under appropriate conditions. Therefore, according to the present invention, a production method capable of forming a superconducting wire stably with a simple method is obtained.

The perspective view which shows an example of the superconducting wire of one Embodiment which concerns on this invention. The schematic diagram which shows an example of the manufacturing apparatus of the superconducting wire of one Embodiment which concerns on this invention. The perspective view which shows one Embodiment of the conventional oxide superconducting tape.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a perspective view showing an embodiment of the superconducting wire 100 of the present invention, and FIG. 1B is a perspective view showing a part of FIG.
A superconducting wire 100 according to the present embodiment includes a first base body 10 formed by stacking an intermediate layer 2, a superconducting layer 3, and a protective layer 4 in this order on one surface of a long first base material 1, and The second base 20 is formed of a long second base material 5 made of a stabilizer and overlapping the protective layer 4. Further, the second base body 20 is provided with a concave portion that is continuous in the longitudinal direction, and the inner bottom surface of the concave portion and the protective layer 4 are joined via a conductive joining member 6, and the superconducting layer The three side surfaces are all disposed in the recess.

As the first base material 1, a tape-like base material made of a metal material having sufficient mechanical strength and flexibility, heat resistance, and oxidation resistance as a base material for the superconducting wire 100 is generally used. In addition, any of various metal materials typified by stainless steel, copper, etc., or those composed of various types of glass or ceramics may be used. The length, width, and thickness of the first base material 1 can be appropriately set according to the use of the superconducting wire 100 to be manufactured, but in this embodiment, the width is 2 to 10 mm, more preferably 5 to 10 mm. Things shall be used.
The intermediate layer 2 has a crystal structure close to the crystal of the superconducting layer formed on the intermediate layer 2 later (for example, a cubic crystal structure), and has a thermal expansion coefficient close to that of the superconducting layer. The thin film which has is preferable. Therefore, the material constituting the intermediate layer 2 is preferably a ceramic material such as MgO, SrTiO ₃ , Gd ₂ Zr ₂ O ₇ , CeO ₂ , YSZ.

As a material constituting the superconducting layer 3, an oxide superconductor having a high critical temperature represented by a composition such as a ReBaCuO-based composition (Re is a rare earth element such as Gd, Y, Ho, or Sn) is preferably used.
The protective layer 4 is made of a noble metal such as Ag, Pt, or Au or an alloy thereof according to the application, and the second base material 5 is a highly conductive metal material that is less expensive than a noble metal such as Cu or Al. A high resistance material such as NiCr or NiCu is used. For example, solder is used as the joining member 6, but the present invention is not limited to this, and any other conductive material may be used.

  According to the structure of the superconducting wire 100 of the present invention, the superconducting layer 3 is disposed so that all the side surfaces of the superconducting layer 3 are accommodated in the recesses provided in the second substrate 20. By covering with the chemical, a configuration in which the superconducting layer 3 is shielded from the outside can be realized. By adopting such a configuration, it is possible to suppress moisture from entering the superconducting layer 3 and prevent chemical damage to the superconducting layer 3. As a result, the reduction of the critical current density can be suppressed, and a superconducting wire having good superconducting characteristics can be obtained.

Furthermore, in the superconducting wire 100 of the present invention, it is preferable that the other surface of the first substrate 1 is arranged at the same height or lower than the surface of the second substrate 20 on which the concave portion is formed. . Thus, when all the side surfaces of the first substrate 10 including the superconducting layer 3 are accommodated in the recesses, the effect of suppressing the intrusion of moisture into the superconducting layer 3 is further improved, and a structure that is not susceptible to chemical damage is obtained. At the same time, even when pressure is applied in the thickness direction to join the first substrate 10 and the second substrate 20, the superconducting layer 3 has a structure that is not easily damaged by external pressure. As a result, the decrease in critical current density can be further suppressed, and a superconducting wire having good superconducting characteristics can be obtained.
At this time, it is further preferable that the joining member 6 is arranged so as to cover at least the side surface of the superconducting layer 3, more preferably all the side surfaces of the first substrate 10 together with the bottom surface in the recess. By setting it as such a structure, since all the side surfaces of the superconducting layer 3 are covered with the joining member 6, and the exposure to the outside is prevented, the effect of suppressing the penetration of moisture into the superconducting layer 3 can be further enhanced.

  In the method for manufacturing a superconducting wire according to the present embodiment, an intermediate layer 2, a superconducting layer 3, and a protective layer 4 are sequentially stacked on one surface of a long first base material 1 to form a first substrate 10. A step A, a step B in which the concave portion is provided in the longitudinal direction of the long second base material 5 made of the stabilizing material, and the second base body 20 is formed; A step C in which the bonding member 6 is placed between the inner bottom surface of the recess and the surface of the protective layer 4 constituting the first base 10, and a step D in which heating and pressurizing treatments are performed and both are bonded. And at least.

Hereinafter, an embodiment of a method for producing the superconducting wire 100 of the present invention will be described.
An intermediate layer 2 as a diffusion barrier is formed on one surface of the long first substrate 1 by a film forming method. As a method for forming the intermediate layer 2, any film forming method such as sputtering, vacuum vapor deposition, laser vapor deposition, or chemical vapor deposition (CVD) may be used. In order to obtain a film having good crystallinity, it is manufactured by an IBAD method capable of continuously forming a uniform film on a long base material for a long time.

Next, the superconducting layer 3 is formed on the intermediate layer 2. In this case as well, various film forming methods can be used in the same manner as described above. However, it is preferable to use a laser vapor deposition method capable of forming a uniform film continuously for a long time. As a base material at this time, for example, an oxide or oxide superconductor target having a composition of Y ₁ Ba ₂ Cu ₃ O _7-x is used, and the substrate is heated to a desired temperature of about 700 to 1000 ° C. The film formation process may be performed in a reduced pressure atmosphere containing oxygen. Furthermore, a process A for forming the first substrate 10 by forming the protective layer 4 also serving as a base stabilizing layer on the superconducting layer 3 by a film forming method so as to have a thickness of about several μm to several tens of μm. Complete. In this case as well, various film forming methods can be used as described above.

  Next, the process B which provides a recessed part in the longitudinal direction of the 2nd base material 5 which consists of stabilizers, such as Cu, and forms said 2nd base | substrate 20 is performed. This recess can be formed by, for example, extrusion molding or mechanical grinding. Note that the method of forming these recesses is not limited to this, and physical processing such as wet etching using a solution of acid or alkali, sandblasting, laser, or the like is also possible.

  Thereafter, a joining member 6 made of a conductive metal material such as solder is uniformly formed in the recess by plating, and the inner bottom surface of the recess and the surface of the protective layer 4 constituting the first base body 10 are formed. Step C is arranged so as to face each other. In addition, the process C is not limited to the plating method. For example, the deposition method, the sputtering method, the CVD method, or the like is used. The process C is uniformly applied to the bottom surface of the recess or uniformly in the recess (inner bottom surface and side surface). The joining member 6 made of a conductive metal material may be formed.

  Furthermore, the superconducting wire 100 having sufficient bonding strength and excellent superconducting characteristics is obtained by performing the step D of bonding the first substrate 10 and the second substrate 20 while performing heat treatment and pressure treatment. Can do. At this time, for example, by using a manufacturing apparatus having a structure as shown in FIG. 2, the first substrate 10 and the second substrate 20 wound around the individual carry-out rolls A and B are moved in the directions of arrows α and β, respectively. And then proceeding in the direction of the arrow γ while both are overlapped by the guide rolls C1, C2, joined together while pressing with the metal roll located in the subsequent stage, and then led out in the direction of the arrow δ, A method of manufacturing a desired superconducting wire 100 can be used by winding and storing it on a winding roll E.

Thus, by using the process of forming separately the 1st base 10 which is a layered product containing superconducting layer 3, and the 2nd base 20 which consisted of a stabilizing material and in which a crevice was arranged, and joined both together First, the two can be separately produced under optimum conditions and then integrated under appropriate conditions. Therefore, it is possible to stably form a superconducting wire by a simple method.
In this joining, the joining member 6 a (6) may be disposed at least in the contact area between the inner bottom surface of the recess provided in the second substrate 20 and the first substrate 10. However, it is more preferable to provide the bonding member 6b (6) so as to cover all the side surfaces of the first base 10 as well as the side surfaces of the superconducting layer 3 together with the bottom surfaces in the recesses. Thereby, since the side surface of the first substrate 10 is further shielded from the outside, it is possible to improve the effect of avoiding the mechanical or chemical influence from the outside on the superconducting layer 3.

  Furthermore, in the method of manufacturing a superconducting wire of the present invention, it is more preferable to perform the step E of performing preheating before the step D. By this heat treatment, distortion of the first substrate 10 or the second substrate 20 made of a stabilizing material, which is a superconducting laminate, can be alleviated, and thus the superconducting wire 100 having stable characteristics that is hardly affected by the distortion of each member is provided. Is possible.

  Further, in step C, the surface of the first base material 1 constituting the first base 10 is arranged so as to be the same height or lower than the surface of the second base 20 on which the concave portion is formed. More preferably. Thereby, the 1st base | substrate 10 and the 2nd base | substrate 20 can be joined, without applying a big pressure directly to the superconducting layer 3 in the case of a pressurization process. Also, when processing into a coil shape, the pressure applied to the superconducting layer 3 can be similarly reduced. Therefore, the superconducting layer 3 is not easily damaged, and a superconducting wire having good superconducting characteristics can be easily formed. Therefore, this arrangement significantly contributes to an improvement in yield during mass production.

  In addition, after forming the intermediate layer on the metal substrate by the IBAD method, instead of the method of providing the superconductor, for example, the crystal orientation of the metal substrate is aligned by rolling, and the crystal orientation is aligned on the surface. A method of providing a superconductor after forming the intermediate layer by a film forming method other than the IBAD method may be employed. Even when the latter method is adopted, the operation and effect according to the present invention can be obtained.

  In the present invention, the superconducting laminate is arranged so as to be accommodated in a recess formed in a long base made of a stabilizing material, and the side surface of the superconducting layer is covered with a stabilizing material or a joining member. In this way, it is possible to use the superconducting wire which can suppress the intrusion of moisture into the superconducting layer and hardly receive mechanical or chemical damage from the outside, and can suppress the decrease in the critical current density, and the production thereof. For example, it can be expected to be applied to various devices such as superconducting motors and superconducting magnets that are expected to be replaced with superconducting wires among coils that have been conventionally made of a metal conductor such as copper.

  DESCRIPTION OF SYMBOLS 1 1st base material, 2 intermediate | middle layer, 3 superconducting layer, 4 protective layer, 5 2nd base material, 6 joining member, 10 1st base | substrate, 20 2nd base | substrate.

Claims (7)

A long base made of a stabilizing material that overlaps the protective layer and a first base layer formed by overlapping an intermediate layer, a superconducting layer, and a protective layer in this order on one surface of the long first base material A superconducting wire comprising at least a second substrate composed of a second base material,
A concave portion that is continuous in the longitudinal direction is disposed on a surface of the second substrate that faces the protective layer, and an inner bottom surface of the concave portion is bonded to the protective layer via a conductive bonding member, and The superconducting wire is characterized in that the superconducting layer is arranged so that all of its side faces are accommodated in the recess.   2. The oxide according to claim 1, wherein the other surface of the first base material is configured to have the same height as or lower than the surface of the second substrate on which the concave portion is formed. Superconducting wire.   The superconducting wire according to claim 1, wherein the joining member is further disposed so as to cover a side surface of the superconducting layer. A long base made of a stabilizing material that overlaps the protective layer and a first base layer formed by overlapping an intermediate layer, a superconducting layer, and a protective layer in this order on one surface of the long first base material A superconducting wire manufacturing method comprising at least a second substrate made of a second base material,
On one surface of the first base material, an intermediate layer, a superconducting layer, and a protective layer are sequentially stacked to provide the first base, and
Providing a recess in the longitudinal direction of the second substrate to form the second substrate; and
A step C in which a bonding member is disposed between the inner bottom surface of the recess provided in the second substrate and the surface of the protective layer constituting the first substrate;
Process D which performs heating and pressurizing treatment and joins both,
A process for producing a superconducting wire characterized by comprising:   The method for producing a superconducting wire according to claim 4, further comprising a step E of performing preheating before the step D.   In the step C, the other surface of the first base material is disposed so as to be the same height as or lower than the surface of the second substrate on which the concave portion is formed. A method for producing a superconducting wire according to 4 or 5.   7. The process D according to claim 4, wherein in the step D, the joining member is subjected to a heating and pressurizing process so as to cover at least the side surface of the superconducting layer together with the bottom surface in the recess. A manufacturing method of the superconducting wire described.

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