JP4016547B2 - Oxide superconductor, strand for oxide superconductor, and method for producing them - Google Patents

Description

[0001]
[Industrial technical field]
The present invention relates to an oxide superconducting conductor on which a film of an inorganic insulating material is formed, the conductor wire, and a method for producing them.
[0002]
[Prior art]
As the oxide superconductor, a so-called silver sheath multi-core oxide superconductor in which the oxide superconductor is coated with silver or a silver alloy is known. In this case, the oxide superconductor constituting the core is a precursor powder of an oxide superconductor such as Bi-2223, Bi-2212, Tl-1223, Tl-2223, Y-123, and Nd-123. It is formed by combining with a metal material of silver or a silver alloy, optionally performing a surface reduction process, and finally performing a superconducting heat treatment. Such a composite structure is, for example, a method in which an oxide superconductor is divided into a plurality of strands, and the aggregate is further covered with silver or a silver alloy to form an oxide superconductor having a circular cross section, that is, a round wire. Is frequently used. In addition, a rolling process is performed on such a round wire to form a tape-shaped conductor having a rectangular cross section.
[0003]
In such an oxide superconducting conductor, the oxide superconductors of each superconducting wire are cut off by the coated silver or silver alloy. However, the high electrical conductivity of silver or silver alloy not only provides a low electrical resistance in the longitudinal direction of the superconducting strands, but also provides a low lateral electrical resistance between the strands. Therefore, when such a conductor is used for the conduction of alternating current, it will produce eddy currents with flow vortices that flow in opposite directions through several sections of superconducting wires with different currents inside the conductor. There is a huge loss of electrical energy.
[0004]
In order to suppress the generation of such eddy currents, an insulating layer capable of electrically interrupting each strand may be provided between the strands. As a method of manufacturing such an oxide superconducting conductor, an insulating layer having a higher electrical resistance than silver or a silver alloy, for example, BaZrO ₃ , SrZrO ₃ , Al ₂ O, is formed on the silver sheath of the strand that is each superconducting precursor. _3. It is known to coat an inorganic insulating material such as MgO.
[0005]
[Problems to be solved by the invention]
As a method for coating the inorganic insulating material, powder such as BaZrO ₃ is mixed with a solvent such as ethanol, applied and dried. However, in this method, since the solvent is completely volatilized after drying, the remaining powder of the inorganic insulating material such as BaZrO ₃ is peeled off immediately after being in contact with the outer periphery of the strand. As a result, there are a portion where the insulating film is partially present and a portion where the insulating film is not present.
[0006]
Also, after applying powder of inorganic insulating material mixed with solvent to the strands of oxide superconducting precursor, even if an attempt is made to make the thickness uniform using a die or the like, if the solvent volatilizes, inorganic insulation such as BaZrO ₃ Of course, the thickness of the material powder is not uniform because the powder of the material is partially peeled off.
[0007]
Furthermore, the oxide superconducting precursor wire coated with a suspension of an inorganic insulating material and a solvent is subjected to mechanical processing such as wire drawing or stranded wire processing before superconducting heat treatment for the same reason as described above. I can't.
[0008]
An object of the present invention is to provide an oxide superconducting conductor with little loss of electric energy even if it is machined before superconducting heat treatment.
[0009]
[Means for Solving the Problems]
According to the present invention, the object is to form a coating film of an organic substance on the outer periphery of a strand formed by coating an oxide superconductor or a precursor thereof with a metal material, and heat-treat the coating film of the organic substance. After coating a uniform thickness of a coating material formed by mixing an inorganic insulating material powder with a resin enamel paint, etc. on the outer periphery of the coating, a coating obtained by chemically reacting with an organic substance is cured. Heat treatment is performed on the wire on which the coating film of the material is formed, and the organic substance in the coating film is chemically reacted to be cured, and then, a plurality of the strands having a layer of the coating material containing the cured organic substance are formed. This can be achieved by inserting the metal material into a pipe to form an aggregate, and heat-treating the aggregate to decompose and remove organic substances in the film and the coating material layer.
[0010]
In this case, the oxide superconductor or a precursor thereof includes Bi-based materials such as Bi-2223 and Bi-2212 described above, Tl-based materials such as Tl-1223 and Tl-2223, and 123 such as Y-123 and Nd-123. A system or the like can be used.
[0011]
Further, as the metal material, metals other than the above-described silver or silver alloy can be used. Further, as the powder of the inorganic insulating substance, powders such as TiO ₂ as well as BaZrO ₃ , SrZrO ₃ , Al ₂ O ₃ and MgO described above can be used.
[0012]
On the other hand, as a resin enamel paint, which is a component of the coating material, for example, a polyester resin, a polyesterimide resin, a polyamideimide resin, and the like are cured by causing a chemical reaction such as polymerization by an appropriate heat treatment, and further an appropriate heat treatment. It is possible to use a paint mainly composed of an organic substance that decomposes and disappears.
[0013]
The coating material, which is a mixture of inorganic insulating powder and organic paint, is an oxide superconductor or its precursor coated with a metal material such as silver or a silver alloy. After being coated on a certain wire, a chemical reaction such as polymerization is carried out by applying an appropriate heat treatment to cure. Then, after mechanical processing such as wire drawing and twisting is performed, the organic material is decomposed and disappears by performing an appropriate heat treatment. In many cases, the heat treatment for decomposing and disappearing can use superconducting heat treatment for the strands, but may be other heat treatment.
[0014]
In the case of the present invention, a layer having characteristics such as wear resistance, flexibility, peel resistance, and mechanical strength is formed by chemically reacting and curing an organic substance in the coating film of the coating material. The As a result, the wire having the coating material layer can be easily machined such as wire drawing and twisting, and the organic substance is not decomposed after the heat treatment such as superconducting heat treatment. However, it is preferable that the coating material layer be applied through a coating film of an organic material such as a resin enamel coating that does not contain powder of the inorganic insulating material. . By doing so, the applicability | paintability of the coating film of a coating material can be improved. Of course, since it is better for the characteristics such as abrasion resistance and peel resistance when the inorganic insulating material powder is not mixed, the coating of the organic material similar to the above without containing the inorganic material powder on the coating material layer. A film may be formed. The coating film or coating material layer composed solely of these organic substances may be a single layer or a plurality of layers, and they may be a combination of films containing different organic substances.
[0015]
Of course, the organic material that forms a film of only an organic material that does not contain an inorganic insulating material, like the organic material in the coating material layer, is cured by a chemical reaction caused by an appropriate heat treatment, and decomposed by a heat treatment such as superconducting heat treatment The one that disappears is used.
[0016]
In addition, the combination of the oxide superconductor or the precursor thereof and a metal material such as silver in the wire is a dip coating method, a doctor blade method, a powder in tube method, a jelly roll method, a thermal spraying method, a screen printing method, a vapor deposition method, Any of CVD method, sputtering method, laser ablation method, etc. can be used. In the surface coating method in the above method, the surface of the exposed oxide superconductor or its precursor is covered with a metal material similar to the base metal material, and finally, The outer periphery may be covered with a metal material.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0018]
[Example 1]
As one of the coating materials, polyester enamel paint (trade name WH-4068 of Hitachi Chemical Co., Ltd.), polyesterimide enamel paint (trade name EH-402 of Dainichi Seika Co., Ltd.), polyamide imide enamel paint (Hitachi Chemical Co., Ltd.) TiO ₂ powder (average 0.2 μm mesh) was selected as the inorganic insulating material powder, which is the other material of the company's trade name HI-406), and this TiO ₂ powder was used as a polyesterimide enamel. The coating material was mixed with the paint at a weight ratio of 1: 1.
[0019]
On the other hand, as a strand which is an oxide superconducting precursor, an oxide superconducting precursor powder having a composition of Bi _1.8 Pb _0.34 Sr _1.9 Ca _2.2 Cu _3.1 O _y (hereinafter referred to as Bi-2223) has an outer diameter of 15 mm, A silver pipe having an inner diameter of 13.5 mm and a length of 500 mm was filled and drawn to an outer diameter of 1 mm.
[0020]
As shown in FIG. 2, the polyester-based enamel paint is applied to the outer periphery of the prepared wire 1 to a thickness of 3 μm, and then heat-treated at 250 ° C. for 20 minutes to polymerize the enamel paint film to cure. I let you. Next, the coating material is applied to the polyester enamel film 2 to a thickness of 10 μm, and then heat-treated at 250 ° C. for 30 minutes to polymerize the polyesterimide in the coating film of the coating material. Cured. Finally, the polyamide-imide enamel paint is applied to the coating material layer 3 to a thickness of 3 μm, and then heat-treated at 250 ° C. for 20 minutes to polymerize the coating film to obtain a polyamide-imide enamel film. 4 was obtained, and an element wire 11 having two layers of enamel films 2, 4 and one layer 3 of a coating material was obtained. When each coating film was formed, a uniform coating thickness was obtained through a die immediately after coating.
[0021]
Then, the obtained strand 11 was heat-processed at 840 degreeC for 100 hours, and the Bi-2223 precursor was converted into the Bi-2223 superconductor. By this heat treatment (superconducting heat treatment), all the organic substances in the enamel coatings 2 and 4 and the coating material layer 3 are decomposed and disappeared, and the TiO ₂ layer 31 has a uniform thickness as an insulating layer on the outer periphery of the strand 1. And it remained in the state without a spot, and obtained Bi-2223 oxide superconducting element wire with an insulating layer. At this time, it was confirmed that TiO ₂ had no adverse effect on the superconducting properties of the Bi-2223 oxide superconductor.
[0022]
In FIG. 2, 6 is a Bi-223 oxide superconducting precursor, and 7 is a silver coating.
[0023]
[Comparative Example 1]
The same TiO ₂ powder as used in Example 1 was prepared as an insulating material, and it was mixed with ethanol to prepare a suspension. On the other hand, the same wire as that prepared in Example 1 was prepared as the strand of the oxide superconducting precursor, and the suspension was applied to the outer periphery of the strand. At this time, the coating film had many spots.
[0024]
Next, the coated wire was dried at room temperature and in the air to dry the coated film. Then, at the same time as ethanol volatilized, about half of the TiO ₂ powder was peeled off from the strand.
[0025]
Next, the strand was subjected to a superconducting heat treatment in the same manner as in Example 1 to convert the Bi-2223 oxide superconducting precursor into a Bi-2223 oxide superconductor. However, most of the TiO ₂ powder remaining before the superconducting heat treatment was peeled off from the surface of the wire.
[0026]
[Example 2]
Seven strands 11 having the same two layers of enamel film subjected to polymerization heat treatment and one coating layer as those obtained in Example 1 were prepared. As shown in FIG. The material was assembled in a silver pipe 5 having a diameter of 7 mm, an inner diameter of 3.2 mm, and a length of 200 mm.
[0027]
Next, after drawing the material to an outer diameter of 1.5 mm, a superconducting heat treatment is performed at 840 ° C. for 100 hours, and the Bi-2223 oxide superconducting precursor 6 in each strand 1 is converted into Bi-2223 oxide superconducting. Converted into a body.
[0028]
The superconducting organic materials in the enamel layers 2 and 4 and the coating material layer 3 by heat treatment is eliminated decompose all, as shown in FIG. 1, layer 31 of TiO ₂ on the outer periphery of each wire 1 is substantially as an insulating layer It remained uniform and free from spots.
[0029]
In FIG. 1, 51 indicates a silver coating in which the silver pipe 5 is changed, and 61 indicates a Bi-2223 oxide superconductor.
[0030]
[Comparative Example 2]
Seven strands to which the TiO ₂ powder obtained in Comparative Example 1 was attached were prepared and assembled into a silver pipe in the same manner as in Example 2. At that time, about half of the TiO ₂ powder remaining on the surface of each strand was peeled off from each strand.
[0031]
Next, wire drawing and superconducting heat treatment were performed in the same manner as in Example 2 to convert the Bi-2223 oxide superconducting precursor 6 in each strand 1 into a Bi-2223 oxide superconductor. The TiO ₂ powder adhering to each strand was not peeled off because the outer periphery was covered with silver, but only about 20-30% remained for each strand.
[0032]
[Example 3]
Two strands 11 having the same heat-treated enamel films 2 and 4 and a coating material layer 3 as those obtained in Example 1 were prepared, and the two were twisted at a predetermined pitch as shown in FIG. After the processing, superconducting heat treatment was performed in the same manner as in Example 1. By this superconducting heat treatment, all the organic substances of the enamel coatings 2 and 4 and the coating material layer 3 in each strand 11 are decomposed and disappeared, and TiO ₂ has a uniform thickness as an insulating layer around each strand 1. Remains in the absence of.
[0033]
[Comparative Example 3]
_Two strands to which the TiO ₂ powder obtained in Comparative Example 1 was adhered were prepared and twisted in the same manner as in Example 3. As a result, most of the remaining TiO ₂ powder was peeled off from the strand, It was only partially left inside the wire, and at this point, there was almost no insulation effect.
[0034]
【The invention's effect】
According to the present invention, when an insulating layer is coated with an inorganic insulating material, the powder is mixed with an organic material paint such as a resin enamel paint, and applied to the organic material by a chemical reaction such as polymerization. Therefore, machining such as wire drawing and twisting can be performed before the superconducting heat treatment. Moreover, after the superconducting heat treatment, the organic substance decomposes and disappears, leaving only the inorganic insulating substance. However, when the organic substance decomposes, the oxide superconductor and the metal such as silver constituting the outer periphery of the oxide superconductor are separated. When the resulting conductor is used for alternating current because it reacts somewhat to the extent that it does not affect, so that the inorganic insulating material in the organic material adheres closely to the metal such as silver and acts effectively as an electrical insulator. In addition, there is an effect that the loss of electric energy can be minimized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an oxide superconducting conductor according to the present invention.
FIG. 2 is a cross-sectional view of a wire showing a manufacturing process of an oxide superconducting conductor according to the present invention.
FIG. 3 is a cross-sectional view of a material in the manufacturing process of an example of an oxide superconducting conductor according to the present invention.
FIG. 4 is an explanatory view showing a manufacturing process of another example of the oxide superconducting conductor according to the present invention.
[Explanation of symbols]
1, 11 Wire 2 Polyester-based enamel coating 3 Coating material layer 4 Polyamideimide-based enamel coating 5 Silver pipe 6 Oxide superconducting precursor 7, 51 Silver coating 31 TiO ₂ layer 61 Oxide superconductor

Claims (11)

In the oxide superconducting conductor in which a plurality of oxide superconducting wires formed by coating an oxide superconductor with a metal material are closely arranged in the metal material and divided through an inorganic insulating material layer , the inorganic superconductor A coating film of a coating material, in which an insulating material layer is applied to the outer periphery of the oxide superconducting wire in a uniform thickness and without any spots, and a powder of an inorganic insulating material is mixed with an organic material The organic material in the coating film of the coating material is cured by chemical reaction and cured, and then the heat treatment is performed again to decompose and remove the organic material in the coating material layer. Superconducting conductor. An organic material coating film is formed on the outer periphery of the strand formed by coating the oxide superconductor or its precursor with a metal material, and heat-treated, and the organic material in the organic material coating film is chemically reacted to be cured. After forming a uniform coating film with a uniform thickness on the outer periphery of the coating by mixing an inorganic insulating material with an organic paint, the wire coated with the coating material is heat treated. Then, the organic material in the coating film of the coating material is chemically reacted to be cured, and then a plurality of strands having a coating material layer in which the organic material is cured are inserted into a metal pipe to form an aggregate. The method for producing an oxide superconducting conductor , characterized in that the aggregate is heat-treated to decompose and remove the organic substance in the coating and coating material layer of each strand . Before inserting a plurality of strands into a metal pipe, an organic material coating is formed on the outer periphery of the coating layer on which the organic material has been cured and heat-treated, and the organic material in the organic coating is removed. The method for producing an oxide superconductor according to claim 2 , wherein the oxide superconductor is cured by chemical reaction . 4. The method for producing an oxide superconducting conductor according to claim 2, wherein the organic material coating is a resin enamel coating . The method for producing an oxide superconducting conductor according to any one of claims 2 to 5 , wherein the heat treatment for decomposing and removing the organic substance is a superconducting heat treatment . An oxide superconductor or a precursor thereof is coated with a metal material, and a coating material layer is formed with a uniform thickness on the outer periphery of the metal material via a cured organic material film , the coating The material layer is formed by mixing a powder of an inorganic insulating material with an organic material to form a coating film of a coating material, and then heat-treating and curing the organic material in the coating material of the coating material by chemical reaction. An elemental wire for an oxide superconducting conductor. The strand for oxide superconducting conductors of Claim 6 which has the film | membrane of the hardened organic substance on the outer periphery of the layer of the said coating material . The strand for oxide superconducting conductor according to claim 6 or 7, wherein the cured organic substance is a resin enamel . An organic material coating film is formed on the outer periphery of the strand formed by coating the oxide superconductor or its precursor with a metal material, and heat-treated, and the organic material in the organic material coating film is chemically reacted to be cured. Then, after forming a coating film of a coating material formed by mixing an inorganic insulating material with an organic material paint on the outer periphery to a uniform thickness, the wire having the coating material coating film is heat-treated to heat the coating material. A method for producing a strand for an oxide superconducting conductor , characterized in that an organic substance in a coating film is chemically reacted to be cured . After forming the coating layer in which the organic material is cured, an organic material coating film is formed on the outer periphery of the coating layer and heat-treated, and the organic material in the organic material coating film is chemically reacted to be cured. Item 10. A method for producing an oxide superconducting conductor wire according to Item 9 . The method for producing an oxide superconducting conductor wire according to claim 9 or 10 , wherein the organic paint is a resin enamel paint .

Images