JPH01144514A - Ceramic-based superconductive cable - Google Patents

Abstract

PURPOSE:To obtain a ceramic-based superconductive cable having a high strength and facilitating making itself of a long size by disposing a sintered layer and a stabilizing layer made of a ceramic superconductive material in this order on the circumference of a long-sized ceramic fiber. CONSTITUTION:An SiC-based ceramic fiber 4 is passed over a lower guide reel 5 through a passage hole of an insert 6, passes through a melting crucible 1, and its circumference is applied by means of a die 7 with a molten liquid of YBa2Cu3 alloy 3 of a Y-Ba-Cu-O family contained in the crucible 1. A sintered layer of ceramic superconductive material is then formed by heating in an oxygen flow at 700-1000 deg.C. After sintering, the circumference of the wire is plated with silver or copper. Finally, an organic insulation paint, formal varnish for example, is applied and baked on the circumference of the plated layer. The plated layer is applied as a stabilization material and for mechanical protection and for facilitating terminal attachment. The ceramic superconductive cable 10 obtained has a construction in which a sintered layer 12, stabilization layer 13, and an insulation layer 14 in this order are formed on the circumference of the fiber 11.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a superconducting wire using a ceramic superconducting material.

(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 exhibits the highest critical temperature of Nb, G
It greatly exceeds 23K of e, and is Ba-La-Cu-
0 series ceramics (critical temperature 35K > , La-3r
-Cu-0 series ceramics (superconductivity starting temperature 37 or higher), La-Ca-Cu-0 series ceramics, Y-Ba-
In addition to Cu-0 ceramics (zero resistance temperature of 93K), ceramics that exhibit 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 economical, and when used in superconducting generators, etc., the structure is simple and the efficiency of the heat engine is improved. .

However, since ceramics are hard and brittle,
Unlike the Nb-Ti and Nb3Sn superconducting wires that are currently in practical use, it cannot be bent or coiled, and overcoming this point is the first step toward practical use.

Currently, methods for manufacturing wire rods include heat-treating amorphous tapes or wire rods in an oxygen atmosphere, and filling ceramics into copper-based alloy tubes, then heat-treating and rolling them to form wire rods or tapes. Proposed.

However, the wire rod made by the former method. In addition, extremely rapid cooling is required during manufacturing, and the wire after heat treatment is brittle, so when forming it into a coil, it cannot be wound with high tension to resist electromagnetic force. However, the wire produced by the latter method has the disadvantage that its fixed length is limited by the outer diameter of the copper alloy tube and that the processing process is complicated.

In this case, the heat treatment for producing the ceramic superconducting material cannot be performed after molding because the tube is covered with a copper-based alloy tube, and sufficient characteristics cannot be obtained. Furthermore, like the former, it also has the disadvantage that the necessary strength cannot be obtained during coil winding.

(Problems to be solved by the invention) The present invention has been made to solve the above-mentioned difficulties.
The object of the present invention is to provide a ceramic superconducting wire that does not require rapid cooling to become amorphous, can be easily made into a long length, and has high strength.

[Structure of the Invention] (Means for Solving the Problems) The ceramic superconducting wire of the present invention includes a sintered layer and a stabilizing layer made of a ceramic superconducting material, which are sequentially provided around the outer periphery of a long ceramic fiber. It is characterized by

As the ceramic fiber in the present invention, silicon carbide (SiC)-based or oxide-based ceramic fibers can be used.

These fibers are continuous filaments, with a diameter of 1000 to 1300
It has a high heat resistance of ℃ or more and a tensile strength of 200 to 250 ka/- or more, and its average diameter is, for example, 10 to 250 ka/- 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 Tyrano 11I fiber (5i-Ti-C-0 fiber trade name manufactured by Ube Industries, Ltd.) and Nicalon (SiC fiber trade name manufactured by Nippon Carbon Co., Ltd.). The latter oxide fiber is manufactured by Safil (Imperial Chemical Co., Ltd., UK).
Industries PLC-ICI ^12037
In addition to fiber (trade name), SiO2-based fibers can be used.

It is preferable that the above-mentioned fiber has a volume resistivity of 105ΩC1 or less.If the zero volume resistivity is within the above range, when the temperature of the superconducting wire rises above the critical temperature,
This is because current flows through the fiber more easily and it becomes difficult to break it. If the volume resistivity is high, the terminal voltage will increase when the temperature exceeds the critical temperature, making it easier to break down.9 If the volume resistivity is low, less loss will occur, which is advantageous.

The sintered layer formed on the outer periphery of the ceramic fiber is, for example, Y-Ba-Cu-0 based YBa2 Cu3.
Examples include 0x (x<14; perovskite) and those to which an element such as F is added. This sintered layer is made by coating a ceramic fiber with a superconducting material or a solution in which the fine powder is dispersed, and then sintering it, or by applying heat treatment in an oxidizing atmosphere to a ceramic material that produces a superconducting material. It is formed by depositing it on the fiber and then sintering it. The main methods of deposition are: ■Method of depositing Y-Ba-Cu alloy in a molten state;■Method of depositing Y-Ba-Cu alloy in a molten state;
, Ba, Cu oxides and carbonates are mixed and dissolved,
Methods for depositing this: ■Methods for depositing in a gas phase or ion state by plasma discharge, vapor deposition, thermal spraying, sputtering, etc.;■Y, Ba,
A method of depositing metal salts other than alkali salts such as fatty acids, resin acids, and naphthenic acids containing Cu, that is, metal soaps, ■Nitrates of Y, Ba, and GO? There are two methods: a method of depositing a mixed solution in which g-acid salts are dispersed in a solvent, and a method of depositing a mixed solution in which fine powder of vBa2 Cul Ox is dispersed in a solvent. Of course, the above method can also be applied to other ceramic superconducting materials. In this case, except for the method of depositing the superconducting material itself, it is desirable to mix the respective constituent materials in a predetermined atomic ratio.

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 in a concentration of, for example, 0.1 to 1.
It can be applied to a thickness of 0 μm.

In this case, metals that do not form oxides at high temperatures, e.g.
When 9, AU, Pt, or an alloy thereof is used as a stabilizing material, heat treatment for producing ceramic superconducting e1M can be performed after coating with this stabilizing material. These stabilizing materials do not react with the internal ceramics during heat treatment, moderately restrict the supply of oxygen from the outside, prevent powdering and combustion due to rapid reactions, and generate dense crystals over a long period of time. be able to.

Furthermore, conductive ceramics and conductive polymer materials are used as stabilizing materials. The former conductive ceramics include TiC, NbC, WC5TaC, ZrB, BN, Z
There are carbides such as rN, borides, and nitrides, and examples of the latter conductive polymer materials include polyacetylene and polypyrrole. It is preferable that these stabilizing materials have a volume resistivity of 10 5 ΩC1l 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.

Coatings with these stabilizing materials can be applied in the melt, gas phase or ionic state, similar to the deposition of superconducting materials.

An insulating coating is usually applied to the outside of the above-mentioned stabilizing material. Organic or inorganic materials are used as the insulating wave film, and the organic insulating film is UV-cured urethane resin or PvF enamel resin, while the latter is an inorganic insulating liquid, and the 1m material is alumina, polyborosiloxane resin, etc. be able to.

(Function) Since the present invention has a structure in which a sintered layer and a stabilizing layer of a ceramic superconducting material are sequentially provided on the outside of a ceramic fiber, a long wire can be easily manufactured, and the fiber is made of ceramic. Therefore, the difference in thermal expansion with the superconducting material is small, and the adhesion is also good.

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

Example 1 A SiC ceramic fiber (Tyranno fiber; 5i-Ti-C-0 fiber trade name manufactured by Ube Industries, Ltd.) with an outer diameter of 12 μtφ was placed in a melting crucible 1 made of platinum or quartz as shown in FIG. YBa on the outer periphery of the
2 Cu is deposited on the alloy. This crucible 1 is heated by an external heater 2, and the YBa2 contained therein is heated by an external heater 2.
Cu3 alloy 3 is maintained in a molten state.

The thickness after deposition is 5-6 μl.

The ceramic fiber 4 is passed through the crucible through a hole in an insert 6 disposed at the bottom of the crucible 1 via a lower guide reel 5, and a die 7 covers the outer periphery of the crucible with a predetermined thickness of melt. It will be worn. The above insert 6 and die 7 are N.

Or it is made of old -C "-^1 series alloy etc.

Then, in an oxygen flow of 2kc+r/ct or less, 700 to 1
000° C. to form a sintered layer of ceramic superconducting material. 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.

Ceramic superconductor 1110 manufactured in this way
As shown in FIG. 1, a sintered layer 12 of a ceramic superconducting material, a stable layer 1,
3 and an insulating layer 14 are formed in this order.

Example 2 A SiC fiber with an outer diameter of 10 μmφ was coated with YBa2Cu30x on the outer periphery of Charon (trade name manufactured by Nippon Carbon Co., Ltd.).
(x < 14) was coated to a thickness of 5 to 6 μm by sputtering method and then heated at 950°C.
After the ceramic was sintered by heating in an oxidizing atmosphere, copper was deposited on the outer periphery of the ceramic. The critical temperature (Tc
) is shown in Figure 2.Furthermore, the result of measuring the critical current density (Jc) of the above-mentioned collective line is JC=
It showed 200OA/cze (at 77).

[Effects of the invention As described above, the ceramic superconducting wire of the present invention has
By sequentially forming a sintered layer and a stabilizing layer of ceramic superconducting material on the outside of the ceramic fiber, it is possible to easily manufacture a long mechanically and electrically stable wire rod, and it also has high strength and A superconducting wire with high current density can be obtained.

Since the superconducting wire 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 after the wire obtained in this way is wound into a coil, , a superconducting magnet can be fabricated by impregnating it with enamel varnish.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the ceramic superconducting wire of the present invention, FIG. 2 is a graph showing the critical temperature of the embodiment, and FIG. 3 is a schematic diagram of an apparatus for manufacturing the same. l・・・・・・Melting crucible 3・・・・・・YBa2 Cu3 alloy company liquid 4.1
1...Ceramic fiber 7...Dice 10...Ceramic superconducting wire 12...
...... Ceramic superconducting material sintered layer 13.
......Stabilizing layer 14...Insulating layer Applicant Showa Cable and Wire Co., Ltd. Agent Patent attorney Suyama Sa - (1 other person) Figure 1 J/1TtK> Figure 2

Claims (7)

[Claims] (1) A ceramic superconducting wire characterized in that a sintered layer and a stabilizing layer made of a ceramic superconducting material are sequentially provided on the outer periphery of a ceramic fiber. (2) The ceramic superconducting wire according to claim 1, wherein the ceramic fiber is a silicon carbide or oxide fiber. (3) The ceramic superconducting wire according to claim 1 or 2, wherein the superconducting material is a Y-Ba-Cu-O ceramic. (4) The ceramic superconducting wire according to any one of claims 1 to 3, wherein the stabilizing layer is made of a metal or an alloy. (5) The ceramic superconducting wire according to any one of claims 1 to 3, wherein the stabilizing layer is made of a conductive ceramic or a conductive polymer material. (6) Ceramic fiber has a volume resistivity of 10
The ceramic superconducting wire according to claim 2, which has a resistance of ^5 Ωcm or less. (7) The ceramic superconducting wire according to claim 5, wherein the conductive ceramic or conductive polymer material has a volume resistivity of 10^5 Ωcm or less.