JP2011159455A - Thin-film superconducting wire rod and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film superconducting wire rod and its manufacturing method which allows maintaining enough superconducting characteristics even in performing a bending process with a bending diameter smaller than before. <P>SOLUTION: In the manufacturing method of the thin-film superconducting wire rod with a copper protecting layer formed around a body part equipped with a substrate and a superconducting layer, a thickness of the copper protecting layer located at a superconducting layer side is made thicker than that of the same at a substrate side, and the copper protecting layer is formed by a plating method so that a distance from a neutral line showing a center position of the thickness of the thin-film superconducting wire rod to a surface of the superconducting layer is to be smaller than a given value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin film superconducting wire and a manufacturing method thereof, and more particularly, a thin film superconducting wire capable of maintaining sufficient superconducting characteristics even when bending is performed with a small bending diameter such as formation of a coil, and the manufacturing thereof. Regarding the method.

  Since the discovery of high-temperature superconductors, thin-film superconducting wires having an oxide superconducting layer on a substrate have been vigorously developed for application to power equipment such as cables, coils, and magnets.

  This thin film superconducting wire is generally composed of an intermediate layer and a superconducting layer sequentially formed on a long and flexible metal tape (metal substrate), and a protective layer provided on the intermediate layer and the superconducting layer. Has been.

  An example of such a conventional thin film superconducting wire is shown in FIG. As shown in FIG. 4, the conventional thin film superconducting wire comprises a substrate 1, an intermediate layer 2, a superconducting layer 3, and a superconducting body comprising a silver stabilizing layer 4 formed on the upper surface side of the superconducting layer 3 and the lower surface side of the substrate 1. Part and the copper protective layer 5 formed on the outer periphery thereof (Patent Document 1).

  And a coil etc. are formed by winding such a thin film superconducting wire so that the superconducting layer side may become the perimeter.

JP 2007-80780 A

  In recent years, miniaturization of superconducting equipment has been required, and in response to this, it is required to bend a thin film superconducting wire with a small bending diameter to form a coil or the like.

  However, when the above-described conventional thin film superconducting wire is bent with a small bending diameter, the superconducting characteristics may be deteriorated, and the above-described miniaturization of the superconducting device cannot be sufficiently coped with.

  That is, when bending is performed on the thin film superconducting wire, compressive strain is generated inside the thin film superconducting wire, tensile strain is generated outside, and stress (compressive stress and tensile stress) acts on each. The superconducting layer has a characteristic characteristic of ceramics that is strong against compressive strain but weak against tensile strain. For this reason, the smaller the bending diameter, the larger the tensile strain is generated in the superconducting layer located on the outer periphery, resulting in a large tensile stress, which deteriorates the superconducting characteristics and maintains sufficient superconducting characteristics as a coil. Difficult to do.

  For this reason, it has been desired to develop a thin-film superconducting wire having a small bending diameter limit (outside critical bending diameter) capable of maintaining sufficient superconducting characteristics when forming a coil.

  Therefore, the present invention can sufficiently meet the recent demand for miniaturization of superconducting equipment, and can maintain sufficient superconducting characteristics even when bending is performed with a smaller bending diameter than before. An object of the present invention is to provide a thin film superconducting wire having a small critical outer bending diameter and a method for producing the same.

The invention described in claim 1
A method of manufacturing a thin film superconducting wire in which a copper protective layer is formed around a superconducting body having a substrate and a superconducting layer,
The thickness of the copper protective layer located on the superconducting layer side is made larger than the thickness of the copper protective layer located on the substrate side, and the distance from the neutral line indicating the center position of the thickness of the thin film superconducting wire to the superconducting layer surface The method for producing a thin film superconducting wire characterized in that the copper protective layer is formed by a plating method so that is less than or equal to a predetermined value.

  As described above, when the thin film superconducting wire is bent, compressive strain occurs inside the thin film superconducting wire, and tensile strain occurs outside. At this time, if the superconducting layer is located on the neutral line of the thin film superconducting wire, that is, the virtual line indicating the center position of the thickness of the thin film superconducting wire, the compressive strain and the tensile strain are balanced, so the stress becomes zero and the strain is reduced. Does not occur. However, since the thickness of the substrate is much larger than the thickness of the superconducting layer, in the conventional thin film superconducting wire, the neutral line is located in the substrate and has a large distance from the superconducting layer. As a result, when a coil or the like is formed, a large tensile strain is generated in the superconducting layer located outside by bending, making it difficult to maintain sufficient superconducting characteristics as a coil. It was difficult to design with a high degree of freedom.

  On the other hand, in the invention of this claim, when forming the copper protective layer, the thickness of the copper protective layer located on the superconducting layer side is made larger than the thickness of the copper protective layer located on the substrate side, so that the superconducting from the neutral line. Since the distance to the layer surface (the surface on the thick copper protective layer side) is reduced, even if bending is performed with a small bending diameter, large tensile strain does not occur in the thin film superconducting wire, and the thin film superconducting wire is deteriorated. There is no invitation.

  In the invention of this claim, when forming the copper protective layer on the superconducting layer side, a plating method is used as in the case of forming the copper protective layer in the conventional thin film superconducting wire. As described above, the plating method is a method that has been conventionally employed for forming the copper protective layer, and thus does not cause a significant increase in the manufacturing cost of the thin film superconducting wire.

  Furthermore, the thickness of the superconducting layer side and the copper protective layer on the substrate side can be easily adjusted by a method such as performing masking treatment on the substrate side and performing plating multiple times under the same plating conditions, and in the thickness direction It is also possible to form a copper protective layer with stable quality.

  The “superconducting body having a substrate and a superconducting layer” in the present invention is generally provided with layers such as an intermediate layer and a silver stabilizing layer in addition to the substrate and the superconducting layer. .

  In addition, the “predetermined value” in the present invention means the distance from the neutral line to the surface of the superconducting layer, which causes a tensile strain without any practical problem even when the thin film superconducting wire is subjected to a desired bending process. .

The invention described in claim 2
2. The method for producing a thin film superconducting wire according to claim 1, wherein the copper protective layer located on the superconducting layer side is formed to a thickness satisfying the following formula 1.
{A / (B + R)} × 100 <0.3 (Formula 1)
A: Distance from the neutral wire of the thin film superconducting wire to the surface of the superconducting layer (mm)
B: Distance from the surface of the thin film superconducting wire to the neutral wire (mm)
R: Bending diameter (mm)

  The present inventor measured the degree of tensile strain in the superconducting layer generated during bending and the degree of change in superconducting characteristics such as the critical current value Ic using various conventional thin film superconducting wires. The relationship between the two was examined.

  As a result, when the distance from the neutral wire to the surface of the superconducting layer is Amm, the distance from the surface of the thin film superconducting wire to the neutral wire is Bmm, and the bending diameter is Rmm, the definition is {A / (B + R)} × 100. When the tensile strain (%) is 0.3% or more, it was found that deterioration of superconducting characteristics due to bending (for example, reduction in Ic) occurred, leading to the invention of this claim.

  That is, by forming a thin copper superconducting wire by forming a thick copper protective layer located on the superconducting layer side, the position of the neutral wire can be brought closer to the superconducting layer side. By making this tensile strain less than 0.3%, it is possible to provide a thin film superconducting wire that does not cause deterioration of superconducting characteristics in bending.

The invention according to claim 3
The thin film superconducting wire has a thickness of 0.1 to 0.25 μm,
3. The method for producing a thin film superconducting wire according to claim 2, wherein the copper protective layer located on the superconducting layer side is formed with a thickness such that a distance from the neutral wire to the surface of the superconducting layer is 30 μm or less. is there.

  In general, bending of a thin film superconducting wire is performed with a bending diameter of 10 mm or more. In the case of a thin film superconducting wire having a thickness of 0.1 to 0.25 μm, which is the thickness of a general thin film superconducting wire, on the superconducting layer side so that the distance from the neutral wire of the thin film superconducting wire to the surface of the superconducting layer is 30 μm or less. When the thickness of the copper protective layer is thick, the tensile strain when the bending diameter (R) = 10 mm is less than 0.3% according to the calculation based on the above formula 1, so that bending work is performed with a bending diameter of 10 mm. Even if it is carried out, the superconducting characteristics are not deteriorated.

The invention according to claim 4
It is manufactured using the manufacturing method of the thin film superconducting wire of any one of Claim 1 thru | or 3, It is a thin film superconducting wire characterized by the above-mentioned.

  As described above, the thin film superconducting wire manufactured using the method for manufacturing a thin film superconducting wire according to any one of claims 1 to 3 is a thin film superconducting wire even if it is bent with a small bending diameter. Sufficient superconducting characteristics can be maintained without deteriorating superconducting characteristics. Moreover, the thin film superconducting wire with stable quality can be provided at a low cost.

  According to the present invention, it is possible to provide a thin film superconducting wire having a smaller critical outer bending diameter than that of the prior art and a method for manufacturing the same, and sufficiently meet the recent demand for miniaturization of superconducting equipment.

It is a figure explaining the relationship between the bending diameter in a thin film superconducting wire, and Ic (1) / Ic (0). It is sectional drawing which shows typically the outline of a structure of the thin film superconducting wire which concerns on this invention. It is a figure which shows typically the outline of the manufacturing process of the thin film superconducting wire in this invention. It is sectional drawing which shows the outline of a structure of the conventional thin film superconducting wire typically.

  Hereinafter, the present invention will be specifically described based on examples.

1. Effect of bending diameter on degradation of superconducting properties First, the effect of bending diameter on degradation of superconducting properties was examined.

  First, a conventional thin film superconducting wire having the structure shown in Table 1 was prepared, and its critical current value Ic (hereinafter referred to as “Ic (0)”) was measured.

  Thereafter, the thin film superconducting wire was bent at bending diameters of 10 mm, 15 mm, 20 mm, 30 mm and 40 mm, and the critical current value Ic (hereinafter referred to as “Ic (1)”) was measured in the same manner. Ic (1) / Ic (0) was obtained. A result is shown in FIG. 1 by the relationship between a bending diameter and Ic (1) / Ic (0).

  As can be seen from FIG. 1, when the bending diameter is smaller than 20 mm, Ic (1) / Ic (0) interrupts 1, and the thin film superconducting wire is deteriorated.

  Further, the tensile strain (%) generated in the superconducting layer when bending was performed at each bending diameter was calculated using the above formula 1 {A / (B + R)} × 100. As described above, A is the distance (mm) from the neutral line of the thin film superconducting wire to the surface of the superconducting layer, B is the distance (mm) from the surface of the thin film superconducting wire to the neutral line, and R is the bending diameter (mm). ). The results are shown in Table 2.

  From Table 2, it can be seen that when the bending diameter is smaller than 20 mm, which is known to cause deterioration from FIG. 1, tensile strain of 0.3% or more is generated. This shows that the distortion must be less than 0.3%.

2. Relationship between the increase in the thickness of the copper protective layer on the superconducting layer side and strain Next, using the same thin film superconducting wire, increase the thickness of the copper protective layer on the superconducting layer side, and the increased amount gives tensile strain The effect was measured and the distance from the neutral line to the superconducting layer surface was examined.

  Specifically, the thin film superconductor adopts a bending diameter of 10 mm, which is a desirable bending diameter at the time of wire processing, and adopts 0.29% as a value of less than 0.3% that does not cause deterioration of tensile strain. Change the distance (A) from the neutral line of the thin film superconducting wire to the superconducting layer surface by changing the distance (B) from the surface of the wire to the neutral line by increasing the thickness of the copper protective layer on the superconducting layer side. Asked. The results are shown in Table 3.

  From Table 3, in the case of a thin film superconducting wire having a thickness of 0.05 to 0.4 mm, that is, a thickness of 0.1 to 0.8 mm used in the experiment, deterioration is caused if A is 30 μm (0.030 mm) or less. It turns out that it does not occur.

3. Production of Thin Film Superconducting Wire Next, a thin film superconducting wire in this example was produced.

(1) Configuration of Thin Film Superconducting Wire FIG. 2 schematically shows the configuration of the thin film superconducting wire in this example. As shown in FIG. 2, the thin film superconducting wire in the present embodiment is made of copper on the outer periphery of a superconducting main body 11 in which a silver stabilizing layer 4 is formed on both upper and lower surfaces of a substrate 1 on which an intermediate layer 2 and a superconducting layer 3 are formed. A protective layer 5 is formed. And the copper protective layer 5 is comprised from the 1st copper protective layer 5a and the 2nd copper protective layer 5b, and the thickness of the copper protective layer located in the superconducting layer side is the copper protective layer located in the board | substrate side. It is formed thicker than the thickness.

  In order to clearly show each layer in FIG. 2, the neutral line is positioned slightly below the center of the thin film superconducting wire in the drawing.

(2) Production Procedure of Thin Film Superconducting Wire The thin film superconducting wire in this example is produced according to the production process shown in FIG.

(A) Production of Superconducting Main Body First, a superconducting main body 11 having a thickness of 132.5 μm was produced using a known method.

Specifically, a total thickness of 0.5 μm consisting of three layers of CeO ₂ layer / YSZ layer / CeO ₂ layer is formed on an oriented metal substrate (thickness 120 μm) 1 made of Ni and Cu by RF sputtering. Then, a superconducting layer 3 made of GdBCO having a thickness of 2 μm was formed on the intermediate layer 2 by using the PLD method.

  Furthermore, a silver stabilizing layer having a thickness of 8 μm and 2 μm was formed on the superconducting layer 3 and on the back surface of the substrate 1, respectively, by using a DC sputtering method, thereby producing a superconducting body 11.

(B) Forming the first copper protective layer After feeding and transporting the tip of the superconducting body 11 wound around the supply reel 12, the masking material 20 is brought into contact with the silver stabilizing layer on the substrate side. It was immersed in the 1st Cu plating tank 13 in which the plating solution (sulfuric acid: copper sulfate = 150 g: 100 g) was accommodated.

In the first Cu plating tank 13, three surfaces excluding the substrate side of the superconducting body 11 by applying a voltage (current density: 5 A / dm ² ) between the superconducting body 11 and an electrode (positive electrode) (not shown). A first copper protective layer 5a having a thickness of 100 μm was formed.

(C) Formation of the second copper protective layer After removing the superconducting body 11 having the copper protective layer 5a formed from the first Cu plating tank 13 and carrying the masking material 20, the second Cu is removed. It was immersed in the plating tank 14.

  In the second Cu plating tank 14, a voltage was applied to form a second copper protective layer 5 b having a thickness of 10 μm on the outer peripheral surface 4 of the superconducting main body 11 on which the copper protective layer 5 a was formed.

  Thus, although formation of the copper protective layer was performed in two steps, since it was performed under the same plating conditions using the same plating equipment, a copper protective layer with a stable quality could be formed integrally.

(D) Winding After the completion of the second plating, the film is taken out from the second Cu plating tank 14, subjected to post-treatment such as water washing and drying, transported, wound up by the winding reel 16, and thin film superconducting The production of the wire was completed.

  In the manufactured thin film superconducting wire, it was confirmed that the distance from the neutral wire of the thin film superconducting wire to the surface of the superconducting layer was 20 μm and 30 μm or less, and the strain was 0.19% and less than 0.3%.

4). Confirmation of superconducting characteristics The produced thin film superconducting wire was drawn out from a take-up reel, and the critical current value Ic was measured. Thereafter, bending was performed with a bending diameter of 10 mm, and the critical current value Ic was measured again.

  Two critical current values Ic measured before and after bending were compared, and it was confirmed that there was no significant difference in the measured values. Thereby, it turns out that deterioration does not arise even if it bends with a bending diameter of 10 mm.

  As described above, it can be seen that, according to the present invention, it is possible to provide a thin film superconducting wire capable of maintaining sufficient superconducting characteristics without causing deterioration of superconducting characteristics even when bending is performed with a small bending diameter.

  The present invention is not limited to the above embodiment. Various modifications can be made to the above within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Intermediate | middle layer 3 Superconducting layer 4 Silver stabilization layer 5 Copper protective layer 5a 1st copper protective layer 5b 2nd copper protective layer 11 Superconducting main-body part 12 Supply reel 13 1st Cu plating tank 14 2nd Cu Plating tank 16 Take-up reel 20 Masking material

Claims (4)

A method of manufacturing a thin film superconducting wire in which a copper protective layer is formed around a superconducting body having a substrate and a superconducting layer,
The thickness of the copper protective layer located on the superconducting layer side is made larger than the thickness of the copper protective layer located on the substrate side, and the distance from the neutral line indicating the center position of the thickness of the thin film superconducting wire to the superconducting layer surface The method for producing a thin film superconducting wire, characterized in that the copper protective layer is formed by a plating method so that is less than or equal to a predetermined value. The method for producing a thin film superconducting wire according to claim 1, wherein the copper protective layer positioned on the superconducting layer side is formed to a thickness that satisfies the following formula 1.
{A / (B + R)} × 100 <0.3 (Formula 1)
A: Distance from the neutral wire of the thin film superconducting wire to the surface of the superconducting layer (mm)
B: Distance from the surface of the thin film superconducting wire to the neutral wire (mm)
R: Bending diameter (mm) The thin film superconducting wire has a thickness of 0.1 to 0.25 μm,
The method for producing a thin film superconducting wire according to claim 2, wherein the copper protective layer located on the superconducting layer side is formed to have a thickness such that the distance from the neutral wire to the surface of the superconducting layer is 30 µm or less.   A thin film superconducting wire manufactured using the method for manufacturing a thin film superconducting wire according to any one of claims 1 to 3.

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