JPH01144528A - Manufacture of ceramic-base superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a wire material of excellent flexibility and stability by covering the outer side of a ceramic fiber with a mixed solution containing dispersed fine particle of a ceramic superconductive material, heating and sintering the material and covering the sintered layer with a metallic stabilizing member. CONSTITUTION:An application device 3 and a baking oven 4 are arranged between a reel out bobbin 1 wound with SiC-based fiber W and a winding bobbin 2 so that the fiber W is routed. A mixed solution L held in an application tub 3b is prepared by dispersing crushed fine powder of a superconductive material in a polyurethane varnish liquid, with the superconductive material being made by mixing, heating and sintering Y2O3, BaCO3 and CuO. The fiber W is passed through the application tub 3b and the baking oven 4 for several times to produce a primary sintered layer of Y-Ba-Cu-O-based ceramic on the fiber W and is further heated to produce a sintered layer. The outer circumference of the sintered layer is further deposited with TiC as a stabilizing member. This makes it possible to easily manufacture a wire material having excellent flexibility and stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a superconducting wire, and particularly to a method for manufacturing a ceramic superconducting wire.

(Conventional Technology) In recent years, especially since last fall, the development of ceramic superconductors has been progressing at a rapid pace all over the world.

This superconductor is Nb3G, which has the highest conventional critical temperature.
It is more than 23 of e, and Ba-La-Cu-
0 series ceramics (critical temperature 35), La-8r-
Cu-0 ceramics (superconductivity starting temperature 37 or higher)
, La-Ca-Cu-0 ceramics, Y-Ba-C
In addition to u-0 series ceramics (zero resistance temperature of 93K), ceramics showing a critical temperature of 233 or more than 300 have been reported this year.

In this way, it is possible that ceramic superconducting materials can be used at critical temperatures higher than the liquid nitrogen temperature or at room temperature.
In this case, there is no need to use expensive liquid helium, which is extremely advantageous economically, and when used in a superconducting generator or the like, the structure is simple and the efficiency of the heat engine is improved.

However, since ceramics are hard and brittle,
It cannot be bent or coiled like the Nb-Ti-based or Nb-Sn-based superconducting wires that are currently in practical use, and overcoming this point is the first step toward practical use.

Currently, there are two ways to manufacture wire rods: 1. Heat-treating amorphous tape or wire in an oxygen atmosphere; 2. Filling an alloy tube (for example, Cu-Ni alloy) with raw material powder and pulling both ends to produce wire or tape. 2) A method of filling a copper alloy tube with ceramics, subjecting it to heat treatment, rolling, etc., and forming it into a wire or tape shape, etc. have been proposed.

However, the above method (■) requires extremely rapid cooling and can only yield extremely thin wire rods or thin film tapes, so it has disadvantages as a method for obtaining practical wire rods. However, it is difficult to continuously manufacture long wire rods, and in method (■) above, the fixed length of the wire rod is limited by the outer diameter of the initial copper alloy tube, and the processing process is complicated. . In this case, the heat treatment for producing the ceramic superconductor is performed after molding from the viewpoint of improving superconducting properties.
That is, it is desirable to carry out the process near the final diameter of the wire, but since the wire is coated with a copper-based alloy or a brass tube, it is extremely difficult to supply oxygen to the inside after forming, which is practically impossible.

(Problems to be Solved by the Invention) The present invention was made to solve the above-mentioned difficulties, and it is possible to easily manufacture a long wire rod without requiring rapid cooling to make it amorphous. It is an object of the present invention to provide a method for producing a ceramic superconducting wire, which can be heat-treated in an oxidizing atmosphere in the form of a long wire, and which can produce a practical wire with a high critical current density. That purpose.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a ceramic superconducting wire of the present invention includes (a) applying a ceramic superconducting material to the outer periphery of a ceramic fiber or heating it in an oxidizing atmosphere; A step of depositing a mixed solution in which fine powder consisting of the constituent materials to be produced is dispersed in a solvent, (b) a step of sintering the deposited material, and (c) a step of applying a conductive material to the outer periphery of this sintered layer. The method is characterized by a step of coating with a stabilizing material made of conductive ceramics or conductive polymer.

The above ceramic fiber is made of silicon carbide (SiC
) type or oxide type can be used.

These fibers are continuous filaments, with a diameter of 1000 to 1300
It has high heat resistance of over ℃ and tensile strength of over 200 to 250k (1/■i), and its average diameter is, for example, 10
There are diameters as small as ~13 μIφ, and of course diameters larger than this can also be used. Examples of the former SiC fiber include Tyranno fiber (trade name of 5i-Ti-C-0 fiber manufactured by Ube Industries, Ltd.) and Nicalon (trade name of SiC fiber manufactured by Nippon Carbon Co., Ltd.).
The latter oxide fiber is manufactured by Safil (UK In+perial Chemical Co., Ltd.).
In addition to Industries PLC-ICI 81 to 03 fiber (trade name), 5102 series fiber can be used.

The above-mentioned fiber preferably has a volume resistivity of 10 5 ΩC1 or less. When the volume resistivity is within the above range, when the temperature of the superconducting wire rises above the critical temperature,
This lick makes it easier for current to flow through the fiber and makes it harder to break. If the volume resistivity is high, the terminal voltage will rise when the temperature exceeds the critical temperature, making it easy to break down.If the zero volume resistivity is small, loss will occur less, which is advantageous.

Examples of ceramic superconducting materials include YBa2
There are Cu30X (X <14; perovskite) and those with F cap added thereto, while constituent substances that produce it by heating in an oxidizing atmosphere include carbonates and oxides, such as Y2O3, BaCO3, Cu
Examples include O.

The above substances are dispersed in a solvent in the form of fine powder. In this case, it is preferable that the atomic ratio of each constituent element in the mixed solution matches the atomic ratio of the ceramic superconducting material.The fine powder of the superconducting material is one produced by a solid phase reaction method. Suitable. That is, after uniformly mixing oxides, carbonates, etc., the process of heating in air is repeated, then this is compressed, and then sintered in an oxidizing atmosphere and pulverized can be used.

Further, as a solvent for the mixed solution, an enamel varnish having a low decomposition temperature, such as a polyurethane varnish or a polyvinyl alcohol resin solution, is used.

The generation of a sintered layer of ceramic superconducting material is carried out at a temperature of 700 to 100 while adjusting oxidation in an oxygen stream or under oxygen pressure.
The properties are improved by heating to 0°C.

A stabilizing material is coated on the outside of this sintered layer, and as this stabilizing material, conductive ceramics or conductive polymer materials are used. The former conductive ceramic is Ti
There are carbides, borides, and nitrides such as C, NbC, WClTaC, ZrB, BN, and ZrN, and examples of the latter conductive polymer materials include polyacetylene and polypyrrole. These stabilizing materials preferably have a volume resistivity of 10 5 Ωcm or less. The reason for this is the same as in the case of ceramic fibers, but especially when conductive ceramics are used, the difference in thermal expansion of the constituent members of the wire can be reduced, which is extremely advantageous against thermal effects.

The stabilizing material coating can be applied in the melt, gas phase or ionic state.

An insulating coating is usually applied to the outside of the above-mentioned stabilizing material. Organic or inorganic materials are used as the insulating coating, and the former organic insulating coating includes UV@-cured urethane resin and PVF enamel, while the latter non-containing insulating coating includes alumina and polyborosiloxane resin. .

(Function) In the method of the present invention, a mixed solution containing a fine powder made of a ceramic superconducting material or a constituent material that generates it by heating in an oxidizing atmosphere is deposited on the outside of a ceramic fiber, and then sintered. Therefore, long wire rods can be easily manufactured, and since the fiber is made of ceramics, the difference in thermal expansion with the superconducting material is small.
Moreover, the adhesion is also good.

That is, by achieving the above-mentioned good adhesion and eliminating the need for processing ceramics, it is possible to manufacture long wire rods. Moreover, by using a mixed solution, a method similar to the manufacturing process of enamelled wire can be adopted.

(actual example) Examples of the present invention will be described below.

The figure schematically shows an apparatus for manufacturing a ceramic superconducting wire according to the present invention, in which a coating device r! L3 and baking furnace 4 are arranged in order, and the fiber W
By passing through the coating device 3 and the baking furnace 4 a predetermined number of times via the guide reels 5 to 8, the mixed solution contained in the coating tank 3b is coated and baked in multiple layers via the coating roll 3a. Ru. Note that 9 is a drawing die.

Example 1 Fine powder of a superconducting material was produced by a solid phase reaction method as follows. That is, Y2O3 is 2259, BaC0
The process of mixing 4,679 g of CuO and 239 g of CuO and heating this in air at 950°C for 8 hours was repeated three times, and the resulting powder was pressed by applying a compression force of 1.5 t/c/.
Then, after sintering in air at 950°C for 12 hours,
The H conductive fine powder 500 produced in this way was slowly cooled to 0°C, kept at this temperature for 2 hours, and then ground into powder.
g to polyurethane varnish (cresol solution, 120℃
90 minutes solids content 70χ) was mixed in 1000a.

This mixed solution was stored in the coating tank 3b, and the ceramic fiber W was a SiC fiber with an outer diameter of 10 μlφ and was made of Charon (trade name, manufactured by Nippon Carbon Co., Ltd.), using the above-mentioned coating device, furnace length of 5 m, and furnace temperature of 300 m. The ceramic fiber W is passed through the baking furnace 4 at ~400°C 6 times to form a film with a thickness of 6
．． After forming a primary sintered layer of 8 μm, 1000 wires thus obtained were collected and twisted, and then 950
It was heated at ℃ for 2 hours to form a sintered layer. The thickness of this sintered layer was 3.5 μm. Furthermore, Ti is added to the outer periphery of this sintered layer.
As a result of measuring the characteristics of the wire coated with C, we found that the critical temperature (T
c) is 88K, critical current density (JC) is (0,5~1
．． 0)×10”8/d (at77K).

In the above embodiments, after collective twisting, sintering and coating with a stabilizing layer were performed, but collective twisting may be performed after sintering and coating with a stabilizing layer.

Example 2 500 liters of fine powder of superconducting material prepared by the solid phase reaction method in the same manner as in Example 1 (20% of polyvinyl alcohol resin)
The mixture was uniformly mixed in 1000 G of ethanol solution, and similarly applied and baked onto a SiC fiber having an outer diameter of 10 μlφ. The film thickness at this time was 6.7 μm. 1000 of this wire
After the books were collectively twisted, they were sintered at 950° C. for 2 hours, and the thickness of the sintered layer was 2.8 μm. Furthermore, as a result of measuring the characteristics of the wire rod coated with C on the outer periphery, 'rc = 83K
, Jc = (0,3~0.7)X10"
A/c! (at77K).

[Effects of the Invention] As described above, according to the method for manufacturing a ceramic superconducting wire of the present invention, by forming a sintered layer of a ceramic superconducting material on the outside of a ceramic fiber, long mechanical and electrical It is possible to easily produce a wire rod that is stable in terms of properties, and also to obtain a superconducting wire with a high current density.

Since the superconducting wire manufactured according to the present invention has excellent flexibility, a plurality of these wires can be used to easily form an assembled wire, a stranded wire, or a braided wire, and the wire obtained in this way can be used to form a coil. After winding, it can be impregnated with enamel varnish to create a superconducting magnet.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of an apparatus used in the method of manufacturing a ceramic superconducting wire of the present invention. 3... Coating device 4... Baking furnace W... Ceramic fiber L...
・・・Mixed solution

Claims (7)

[Claims] (1) (a) A step of depositing a mixed solution in which fine powder made of a ceramic superconducting material or a constituent material that is generated by heating in an oxidizing atmosphere is dispersed in a solvent on the outer periphery of the ceramic fiber. (b) Next, the step of sintering the adhered substance; and (c) the step of coating the outer periphery of the sintered layer with a stabilizing material made of conductive ceramics or conductive polymer material. A method for manufacturing a ceramic superconducting wire. (2) The method for manufacturing a ceramic superconducting wire according to claim 1, wherein the ceramic fiber is a silicon carbide fiber or an oxide fiber. (3) The method for manufacturing a ceramic superconducting wire according to claim 1 or 2, wherein the superconducting material is a Y-Ba-Cu-O ceramic. (4) The method for producing a ceramic superconducting wire according to any one of claims 1 to 3, wherein the fine powder of the superconducting substance is produced by a solid phase reaction method. (5) The method for manufacturing a ceramic superconducting wire according to any one of claims 1 to 4, wherein the solvent is an enamel varnish having a low decomposition temperature. (6) Ceramic fiber has a volume resistivity of 10
The method for manufacturing a ceramic superconducting wire according to claim 2, wherein the ceramic superconducting wire has a resistance of ^5 Ωcm or less. (7) The stabilizing material made of conductive ceramics or conductive polymer material has a volume resistivity of 10^5Ωcm.
A method for manufacturing a ceramic superconducting wire according to any one of claims 1, 3 to 6 below.