JPH01149307A - Ceramic superconductive wire - Google Patents

Abstract

PURPOSE:To form easily a long wire having good flexibility and high strength by furnishing a sintered layer of ceramic superconductive substance and an insulating layer one over the other on the periphery of a ceramic fiber strand. CONSTITUTION:A sintered layer 12 consisting of ceramic superconductive substance is formed on the periphery of a strand 11 made from a plurality of long ceramic fibers, and outside it an insulating layer 13 is furnished. The ceramic fiber shall Consi of silicon carbide(SiC) or some oxide, while the sintered layer formed on the periphery of the ceramic fiber strand consist of YBa2Cu3Ox of Y-Ba-Cu-Ox type (x<14; perovskite) or a one with such an element as F as additive. Examples of the insulating film 13 applied to the outside of this sintered layer are UV hardened urethane resin or alumina. This allows easily making in long stretching form, provided with high strength and good flexibility.

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 conventional critical temperature of Nb3
It greatly exceeds Ge's 23K, and Ba-La-Cu
-0 series ceramics (critical temperature 35K), La-5r
-Cu-0 ceramics (superconducting starting temperature 37 or higher), La-Ca-Cu-0 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, 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 is difficult to wind it with high tension to resist electromagnetic force. However, the wire produced by the latter method has the drawback that its fixed length is limited by the outer diameter of the copper-based alloy tube, and 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 and good flexibility.

[Structure of the Invention] (Means for Solving the Problems) The ceramic superconducting wire of the present invention has a sintered layer made of a ceramic superconducting material on the outer periphery of the stranded wire made by twisting a plurality of long ceramic fibers. The feature is that an insulating layer is sequentially provided on the outer side of the insulating layer.

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 250K (1/- or more), and its average diameter is, for example, 10
There is one with an extremely small diameter of ~13 μmφ, and of course one with a larger diameter can also be used. Examples of the former SiC fiber include Tyranno fiber (trade name of Si-T 1-C-0 fiber manufactured by Ube Industries, Ltd.).
and Nicalon (trade name of IJsic fiber by Nippon Carbon Co., Ltd.), and examples of the latter oxide fiber include Safil (Imper, UK; at Cheli).
cal Industries PLC-ICI Al
In addition to 2O3 fiber (trade name), 5102 series fiber 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 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.

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 sintered layer formed on the outer periphery of the ceramic fiber strands is, for example, Y-Ba-Cu-0 based YBa 2 C.
Examples include ut ox (x<14: perovskite) and those to which an element such as F is added. This sintered layer is formed by depositing a superconducting material or a solution containing this fine powder on the ceramic fiber strands and then sintering it, or by heat-treating it in an oxidizing atmosphere to produce a superconducting material. It is formed by depositing on ceramic fiber strands and then sintering them. 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 vapor 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, i.e., metal soap, ■ A mixed solution in which nitrates and oxalates of Y, Ba, and Cu are dispersed in a solvent. (2) A method of depositing a mixed solution in which fine powder of YBa2 Cu30x 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.

In forming the above-mentioned sintered layer, flexibility can be further improved by forming the sintered layer on the outer periphery of the stranded wire excluding the strand gaps in the outermost layer of the stranded wire.

For example, when applying the above-mentioned liquid substance to the outer periphery of the stranded wires, a paint that volatilizes at the sintering temperature may be applied in advance to the gaps between the strands in the outermost layer, or synthetic resin fibers or the like may be twisted together. I can tell you how to keep it.

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.

An insulating coating is applied to the outside of the sintered layer. Organic or inorganic materials are used for the insulating liquid and film, and the former organic insulating film can be UV-cured urethane resin or PVF enamel resin, while the latter inorganic insulating film can be alumina, polyborosiloxane resin, etc. can.

(Function) Since the present invention has a structure in which a sintered layer of ceramic superconducting material and an insulating layer are sequentially provided on the outside of the stranded ceramic fiber wire, long wire rods with good flexibility and high strength can be easily manufactured. Since the fiber strands are made of ceramic, the difference in thermal expansion with the superconducting material is small, and the adhesion is good.

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

Example 1 A strand of seven SiC ceramic fibers (Tyranno fiber: 5i-Ti-C-0 fiber trade name manufactured by Ube Industries, Ltd.) with an outer diameter of 12 μmφ was twisted as shown in FIG. The melt is passed through one width of a melting crucible made of platinum or quartz, and YBa2 Cua alloy is coated on the outer periphery of the melting crucible. This crucible 1 is heated by an external heater 2 to maintain the YBa 2 Cu 3 alloy 3 housed inside in a molten state. The thickness after application is 5-6 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 die 7 are made of No or Ni-Cr-^1 alloy.

700 in an oxygen flow of no more than 2 kg gf/d.
Heating to ~1000°C forms a sintered layer of ceramic superconducting material. This sintering step can also be carried out continuously following the deposition step described above.

After sintering, a coated and baked layer of an organic insulating paint, such as formal varnish, is formed on the outer periphery of the wire.

As shown in FIG. 1, the ceramic superconducting wire 10 manufactured in this manner has a structure in which a sintered layer 12 of a ceramic superconducting material and an insulating layer 13 are sequentially formed around the outer periphery of the ceramic fiber strands 11.

Example 2 On the outer periphery of a stranded wire made by twisting seven SiC fibers (Nicalon; trade name manufactured by Nippon Carbon Co., Ltd.) with an outer diameter of 10 μmφ,
Ceramics consisting of YBa2Cu30x (x < 14) was coated to a thickness of 5 to 6 μm by sputtering.Then, the above ceramics were sintered by heating in an oxidizing atmosphere at 950°C, and then PVF was applied around the outer periphery of the ceramics. Covered with enamel resin. Figure 2 shows the results of measuring the critical temperature (Tc) of the bundle of 150 stranded wires obtained in this way, and the results of measuring the critical current density (Jc) of the bundle of wires described above are shown in Figure 2. J c =200OA/
c/(77K).

[Effects of the invention As described above, the ceramic superconducting wire of the present invention has
By sequentially forming a sintered layer of ceramic superconducting material and an insulating layer around the outer periphery of the stranded ceramic fiber, the fiber remains mechanically and electrically stable even under high-temperature and long-term sintering conditions without causing 'tlRm. It is possible to easily produce a wire with high strength, and also to obtain a superconducting wire with high strength and high current density.

Since the superconducting wire according to the present invention has excellent flexibility, 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 at high tension. After coiling, the enamel face can be impregnated to produce a superconducting magnet.

[Brief Description of the Drawings] 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 the manufacturing equipment thereof. It is a diagram. 1・・・・・・・・・Melting crucible 3・・・・・・・・・YBa2 Cut alloy liquid 4.1
1... Ceramic fiber strand 7...
Dice 10... Ceramic superconducting wire 12...
... Ceramic superconducting material sintered stone 13.
・・・・・・Insulating layer Fig. 1, ]JT(K) Fig. 2

Claims (5)

[Claims] (1) A sintered layer made of a ceramic superconducting material is formed on the outer periphery of a twisted wire of multiple ceramic fibers,
A ceramic superconducting wire characterized by having an insulating layer provided on the outside. (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) 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. (5) The ceramic superconductor according to any one of claims 1 to 4, wherein 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. line.