JPH01149316A - Manufacture of ceramic superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a long, mechanically and electrically stable superconductive wire with high strength and current density by forming a sintered layer of ceramic superconductive substance on the periphery of a ceramic fiber strand. CONSTITUTION:A strand 11 of ceramic fibers is covered with a ceramic superconductive substance or a substance to produce it by heating in oxidative atmosphere. Then this substance is sintered, and the resultant sintered layer 12 is covered with a stabilizing material 13 consisting of metal or an alloy therefrom. The ceramic fiber shall preferably be of SiC type or of oxygen type, and its volume specific resistance be favorably under 10<5>OMEGAcm. This allows easy formation of a long wire, wherein heat treatment in oxidative atmosphere can take place while it is long, and a practically applicable wire with high strength and critical current density can be obtained.

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 much more than 23 of e, and it is Ba-La-Cu-
0 series ceramics (critical temperature 35K), La-5r
-Cu-0 series ceramics (B conductivity start temperature 37 or higher), La-Ca-Cu-0 series ceramics, Y-Ba-
In addition to Cu-0 ceramics (zero resistance temperature of 93 degrees), ceramics showing a critical temperature of 233 degrees or higher than room temperature 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, ceramics are hard and brittle,
Unlike the Nb-Ti and NblSn superconducting wires currently in practical use, it cannot be bent or coiled, and overcoming this point is the first step toward practical use.

Currently, there are two methods for manufacturing wire rods: 1) A method of heat-treating amorphous tape or wire in an oxygen atmosphere; 2) A method of filling raw material powder inside a 0 alloy tube (for example, Cu-Ni alloy) 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. In this case, continuous production of long wire rods is the key to continuous production, and in method ① 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. be. In this case, the heat treatment for producing the ceramic superconductor is performed after forming, from the perspective of improving superconducting properties.
In other words, it is desirable to apply this near the final diameter of the wire, but since it is covered with a copper-based alloy tube, it is extremely difficult to supply oxygen to the inside after forming, which is practically impossible.

Furthermore, wire rods manufactured by any of the above methods have problems in terms of strength, and have the disadvantage that they cannot be wound with high tension in order to resist electromagnetic force during coil formation.

(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. 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 high strength and critical current density. Its purpose is to

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a ceramic superconducting wire of the present invention includes: (a) A ceramic superconducting material or an oxidizing material is added to the outer periphery of the stranded wire obtained by twisting a plurality of lamic fibers. (b) Next, sintering the deposited material; and (c) depositing a metal or its alloy on the outside of this sintered layer. The method is characterized by comprising a step of coating with a stabilizing material.

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 °C and tensile strength of over 200-250 kg/-, and its average diameter is, for example, 10-250 kg/- or more.
There is one as extremely small as 13 μlφ, but of course one with a larger diameter 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.); As the oxide fiber, Sapphire (UK 11perial Chemical In
In addition to SiO2-based fibers such as AhOa fiber manufactured by PLC-ICI (trade name), SiO2-based fibers can also be used.

The above-mentioned fiber preferably has a volume resistivity of 10 5 Ωcm or less. When the volume resistivity is within the above range, when the temperature of the superconducting wire rises above the critical temperature,
If the zero volume resistivity, which is the point at which current flows through the fiber easily and makes it difficult to break down, is high, the terminal voltage will rise when the temperature exceeds the critical temperature, making it easy to break down. If the volume resistivity is small, loss will occur less, which is advantageous.

The above ceramic fibers are used by forming a plurality of them into a twisted wire structure. Good flexibility and significantly greater strength can be achieved in this way.

The at-conducting material to be deposited on the outer periphery of the stranded wires is, for example, YBa2 Cul Ox (x < 14: perovskite) or a material to which F or the like is added. Examples of constituent substances that produce
, aa, Cu or their oxides, carbonates, etc. are used, and by immersing the stranded wire in a melt of these, it is coated on the outer periphery to a thickness of, for example, about 0.1 to 20 μm. Of course, other ceramic-based superconducting materials and constituent materials for producing them can also be used.

In addition to the above-mentioned deposition from the melt state, it is also possible to deposit from the gas phase or ionic state. Examples of such methods include plasma discharge, vapor deposition, thermal spraying, and sputtering.

In this case, it is difficult to adhere to the gaps between the strands of the outermost layer of the stranded wire, thereby further improving the flexibility.

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, for example, silver, copper, aluminum, or an alloy thereof is plated or vapor-deposited to form a layer of 0.1 to 1.
It can be applied to a thickness of 0 μm, and an insulating coating is usually applied on the outside. Organic or inorganic materials are used as the insulating coating, and examples of the former organic insulating coating include UV-cured urethane resin and PVF enamel, while examples of the latter inorganic insulating coating include alumina and polyborosiloxane resin.

(Function) In the method of the present invention, a ceramic superconducting material or a constituent material that generates it by heating in an oxidizing atmosphere is deposited on the outer periphery of a stranded wire made of ceramic fibers, and then sintered. It is possible to easily produce a long wire with excellent flexibility and high strength, and since the fiber is made of ceramics, the difference in thermal expansion with the superconducting material is small and the adhesion is good.

That is, by achieving the above-mentioned good adhesion and eliminating the need for ceramic processing, it is possible to manufacture a long wire rod.6 (Example) Examples of the present invention will be described below.

Example 1 A strand of seven SiC ceramic fibers (Tyranno wt fiber; trade name of MSi-Ti-C-Q fiber, manufactured by Ube Industries, Ltd.) with an outer diameter of 12 μmφ was twisted as shown in Fig. 3. , the melt is passed through a melting crucible 1 made of platinum or quartz, and YBa2 CU3 alloy is deposited on its outer periphery. This crucible 1 is heated by an external drawer 2 to keep the YBa2 CU3 alloy 3 contained therein in a molten state. The thickness of the deposited area is 5 to 6 μm.

The above ceramic fiber strands 4 are connected to the lower guide reel 5
The melt is passed through the inside of the crucible through a hole in an insert 6 disposed at the lower part of the crucible 1, and a predetermined thickness of melt is applied to the outer periphery of the crucible by a die 7. The insert 6 and the die 7 are made of HO or a Ni-Cr-Al alloy.

Then, in an oxygen flow of 2 kgf/c or less, 700 to 10
A sintered layer of ceramic superconducting material is formed by heating to 00°C. This sintering step can also be carried out continuously following the above-described deposition step.

The outer periphery of the sintered wire is plated with silver or copper, and finally, a coated and baked layer of an organic insulating paint, such as formal varnish, is formed on the outside of this plating layer. The above-mentioned plating layer is provided for the purpose of functioning as a stabilizing material, providing mechanical protection, and facilitating terminal attachment.

As shown in FIG. 1, the ceramic superconducting wire 10 manufactured in this manner has a sintered layer 12 of a ceramic superconducting material on the outer periphery of the ceramic fiber strands 11, and a stabilizing layer 11.
3 and an insulating layer 14 are formed in this order.

Example 2 5 to 6 μl of ceramics consisting of YBa2 Cu30x (x <14>) was applied by sputtering to the outer periphery of a twisted wire made by twisting seven SiC fibers (Nicalon; trade name manufactured by Nippon Carbon Co., Ltd.) with an outer diameter of 10 μmφ. After sintering the above ceramic by heating in an oxidizing atmosphere at 950°C, copper was deposited on the outer periphery of the ceramic to a thickness of 150 strands. Figure 2 shows the results of measuring the critical temperature (Tc) of the bundled set wires.

Furthermore, the result of measuring the critical current density (,yc) of the above-mentioned aggregated wires showed that Jc = 200OA/c ((77K>).

[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 outer periphery of a stranded ceramic fiber wire, sintering at high temperature and for a long period of time is possible. It is possible to easily produce a long mechanically and electrically stable wire rod without fiber breakage even under such conditions, and a superconducting wire with high strength and current density can be obtained.

Since the superconducting wire manufactured according to the present invention has excellent visibility, multiple wires can be used to easily form aggregated wires, stranded wires, or braided wires, and the wires obtained in this way can be used to improve After being coiled under tension, it can be impregnated with enamel varnish to produce superconducting magnets.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a ceramic superconducting wire manufactured by the method of the present invention, FIG. 2 is a graph showing its critical temperature, and FIG. 3 is a schematic diagram of its manufacturing apparatus. 1......Melting crucible 3...YBa2 Cu3 alloy liquid 4.1
1... Ceramic fiber strand 7...
Dice 10... Ceramic superconducting wire 12...
...... Ceramic superconducting material sintered layer 13.
・・・・・・Stabilizing layer 14・・・・・・Insulating layer Fig. 1'A Ancho IK) Fig. 2

Claims (7)

[Claims] (1) (a) A step of depositing a ceramic superconducting material or a constituent material produced by heating in an oxidizing atmosphere on the outer periphery of a stranded wire made by twisting a plurality of ceramic fibers; (b) Next, A method for producing a ceramic superconducting wire, comprising the steps of: sintering the adhered material; and (c) coating the outside of the sintered layer with a stabilizing material made of metal or an alloy thereof. (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) A method for manufacturing a ceramic superconducting wire according to any one of claims 1 to 3, wherein the superconducting material or its constituent materials are deposited in a molten state. (5) A method for manufacturing a ceramic superconducting wire according to any one of claims 1 to 3, wherein the superconducting material or its constituent materials are deposited in a gas phase or in an ionic state. (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 sintered layer is formed on the outer periphery of the stranded wire excluding the strand gaps in the outermost layer constituting the stranded wire. A method for producing a ceramic superconducting wire according to item 1.