JPS63308813A - Manufacture of superconductive ceramics wire material - Google Patents

Abstract

PURPOSE:To obtain a superconductive ceramics wire material by spinning from polymer solution which contains dispersed superconductive ceramics powder. CONSTITUTION:Rare earth compound, alkali earth metal compound and cupric oxide, etc., are mixed by the specified amount and heated so as to cause solid phase reaction to make raw material, which is clashed in grains of 5mum or less in diameter with a ball mill. The superconductive ceramics powder obtained is mingled and dispersed in polymer solution. The polymer solution is one that, for example, oligomer having yarn extending property is dissolved in soluble solvent, i.e., cellulose-cupri.ammonium solution, etc. When the raw material is mingled uniformly in the polymer solution, the quantity ratio of the raw material to the polymer and oligomer of the polymer solution is determined as 20-90% by weight and mingled uniformly with a ball mill, etc. The mixture is supplied from a die into the spinning solution and solified there. A superconductive ceramics material can be obtained without using extrusion method or rolling method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a superconducting wire, particularly a superconducting ceramic wire, which is applied to superconducting magnets, power transmission lines, etc.

[Prior Art] Many materials have been known to exhibit superconductivity, and among alloys, Nb-based alloys such as NbxGe and NbN exhibit a high superconducting critical temperature (hereinafter referred to as TC). N
It was reported about 10 years ago that bxGe has a Tc of 23.6 [Applied Phys.
sics Letters, 23480 (1973)]
Until recently, no substances with higher TC were known.

On the other hand, in the composite oxide system, 1-iTiQ4 is 13.7
It has been reported that the TC of [Hat
erials Research Bulletin,
8.

777 (1973)], its T c is low and its practicality as a superconducting material is low.

Superconducting materials have a wide range of applications, and the main area of development is in magnet applications.Superconducting magnets have zero electrical resistance, so they can generate a strong magnetic field with only a small amount of power required for cooling. becomes possible. Therefore, it can be expected to be applied to fields that require a strong magnetic field, such as nuclear fusion, magnetic levitation trains, MHD power generation, accelerators, and motors. In the power field, there are applications for power generation, power storage, and power transmission lines.
For the electronics field, computer elements such as logic and memory (Josephson elements),
It has applications in sensors that detect weak magnetic fields (quantum interference devices) and microwave elements that can be used in millimeter-wave mixers and transmitters.

Superconducting materials used in such applications are required to have a high Tc, and the search for materials is still ongoing. If a material with a high Tc is developed, liquid nitrogen (boiling point 77.3 K), which is inexpensive and abundant in resources, can be used as a refrigerant instead of liquid helium (boiling point 4.2 K), which is expensive and problematic in terms of resources. It is expected that its applications will further expand dramatically.

[
Zeitschrift fur physik.

B 64,189 (198B)], roughly high T c
(As a substance with 90K>, Y-Ba-Cu-0
Rare earth complex oxides have also been reported [Physical Review Letter
s, 58.91t (1987)].

[Problems to be Solved by the Invention] Conventional alloy superconductors represented by Nb-Ti, Nb3Sn, etc. have ductility and are processed into wire rods by rolling, extrusion, or the like.

On the other hand, since superconducting ceramics are brittle, their molded bodies have low strength against bending and twisting, and their processing and application ranges are limited.

The present invention aims to provide a new method different from the conventional method for manufacturing superconducting ceramic wire.

[Means for Solving the Problems] As a result of intensive research in order to solve the above-mentioned problems, the present inventors have found that by mixing and dispersing superconducting ceramic powder in a polymer solution and spinning this solution, wires can be created. The present inventors have discovered that superconducting ceramics having a shape of

That is, the present invention is a method for producing a superconducting ceramic wire by spinning a polymer solution containing dispersed superconducting ceramic raw material powder.

The method for manufacturing the superconducting ceramic wire of the present invention will be described in detail below.

The superconducting ceramic powder used in the present invention refers to powders of superconducting composite oxides, sulfides, nitrides, etc., and any of these can be used. Among these, L r -T + -o type (TO1
3,7k>, Ba-(Pb-Bi)-0 system (TO13
K), Rb-W-0 series (Tc6.4K), or copper-based composite oxides.

Lr-Tro system, 3a-(Pb-[3i)
-〇 series and Rb-W-〇 series composite oxides have low TC, so
Liquid helium, which is expensive and scarce in resources, must be used, which limits its practical use. On the other hand, some copper-based composite oxides have Tc higher than liquid nitrogen, so
Liquid nitrogen, which is low cost and abundant in resources, can be used for cooling, making it more preferable from an industrial perspective.

The superconducting copper-based composite oxide has the general formula % where Ml is at least one selected from Ca, 3r and 3a, M2 is Sc, Y, La, Ce, Pr, Nd,
Pm, Sm, Eu, Gd, Tb, DV, HOlEr, T
It is at least one selected from m, Yb, and Lu. Roughly speaking, the composition ratio of a, b, and x is 0.5≦a≦3 0.01≦X≦0.9 1.0≦b≦4.0 in a highly Tc superconducting composite It is preferable because it forms oxides.

Next, a method for producing a superconducting composite oxide will be explained.

Complex oxides include, for example, rare earth compounds such as rare earth oxides and rare earth hydroxides, alkaline earth metal compounds such as barium oxide, barium carbonate, strontium oxide, and strontium carbonate, and cupric oxide and cupric carbonate. A method in which an aqueous solution of oxalate is added to a mixture of aqueous solutions of rare earth elements, alkaline earth metals such as strontium and barium, and soluble compounds such as copper chlorides and nitrates. There is a method of co-precipitating and then heating and reacting. Further, after producing a precipitate by a coprecipitation method using two of these metal salts, a predetermined composite oxide can also be obtained by mixing the precipitate with other metal compounds.

Although the conditions for the heating reaction vary depending on the composition, it is preferable to carry out the reaction at 600° C. to 1000° C. for 0.5 hours to 1 week in a predetermined atmosphere.

The superconducting ceramic obtained as described above is pulverized using a pulverizing means such as a ball mill or a jet mill, if necessary.

It is preferable that the particle size of the superconducting ceramic powder used in the present invention is minute in order to uniformly mix it with the polymer solution, and it is usually desirable that the particle size is 5 μm or less.

Next, the polymer solution used in the present invention will be explained. The polymer solution of the present invention refers to a solution in which, for example, a polymer or oligomer having residual thread properties is dissolved in a soluble solvent. Polymers of the present invention, oligomers such as cellulose,
Natural polymers such as nitrocellulose, casein, alginic acid and their derivatives and their oligomers, polyvinyl alcohol, polyvinyl acetate, polyvinylidene chloride,
Synthetic polymers such as polyvinyl chloride, polyacrylonitrile, polyethylene terephthalate, polyurethane, polymethyl methacrylate, polystyrene, polyvinyl butyral, and polyphenylene oxide, homopolymers of oligomers thereof, and copolymers thereof can be used. However, without being limited to the above-mentioned substances, a thermoplastic polymer having no soluble solvent can also be heated and melted and used as the polymer solution of the present invention. As the thermoplastic polymer, for example, polyacetal, nylon, polyethylene, polypropylene, etc. can be used.

Solvents in which these polymers and oligomers are soluble vary depending on the type, molecular weight, and molecular structure of the polymer. Therefore, combinations of polymers, oligomers and soluble solvents in the polymer solution include, for example, cellulose-copper ammonia aqueous solution, nitrocellulose-isopropanol, casein-sodium hydroxide aqueous solution, alginic acid-sodium carbonate aqueous solution, polyvinyl alcohol-water, polyacetic acid. Vinyl-methyl ethyl ketone, polyvinylidene chloride-tetrahydrofuran, polyvinyl chloride-acetone/benzene mixed solvent, polyacrylonitrile-dimethylformamide, polyethylene terephthalate-chlorinated acetic acid, polyurethane [(hexamethylene diisocyanate-polytetramethylene glycol (average molecular weight 1000) Copolymers (average molecular weight 50,000>)-toluene/methyl ethyl ketone mixed solvent, polymethyl methacrylate-toluene, polystyrene-toluene, polyvinyl butyral-methyl ethyl ketone/toluene mixed solvent, cellulose acetate-acetone, polyphenylene oxide-toluene, etc. can.

The ratio of the polymer or oligomer to the soluble solvent in the polymer solution varies depending on the type of polymer or oligomer, but is preferably in the range of 1 to 95% by weight, more preferably in the range of 5 to 90% by weight. In order to improve the dispersibility of the superconducting ceramic powder raw material, surfactants, dispersants and polymers are mixed into the polymer solution, and plasticizers, curing agents, cross-linking agents, etc. are mixed in to improve the mechanical properties of oligomers. can be used.

When the superconducting ceramic powder raw material is uniformly mixed into the polymer solution, the amount ratio of the superconducting ceramic powder raw material to the polymer or oligomer in the polymer solution is preferably 10 to 95% by weight, more preferably 20% by weight.
It is in the range of ~90% by weight. The mixing method can be a conventional ball mill, a rotational mill, a kneader, a homogenizer, an ultrasonic dispersion, a strong stirring, or the like, and a uniform mixture can be obtained.

Next, the mixture is spun, and the spinning method will be explained. The spinning method of the present invention includes, for example, a wet spinning method in which the mixture is continuously fed from a die into a spinning solution in which the polymer or oligomer coagulates to solidify the mixture, and a wet spinning method in which the mixture is fed from a die into a coagulation atmosphere such as a reduced pressure atmosphere or a heating atmosphere. A linear superconducting ceramic raw material composite can be obtained by using a dry spinning method in which the mixture is continuously supplied to solidify the mixture. In addition, a process such as stretching or pressing may be added to improve the mechanical strength and moldability of the linear composite.

Next, by heating the composite, a superconducting wire can be obtained. That is, by this firing, the polymer and oligomer can be decomposed and removed, and the superconducting ceramic powder can be sintered. The conditions for heating the composite vary depending on the composition, but range from 600'C to 12
．． It is preferable to carry out the test at 00° C. for 0.5 hours to 1 week in a predetermined atmosphere.

Further, after heating the composite, a normal conductor layer such as copper for stabilization and countermeasures against fault currents, a moisture-proof protective layer such as SiN for moisture-proofing, etc. can be provided.

[Example] The present invention will be explained in more detail below using examples.

Example 1 Yttrium oxide, barium nitrate, and copper nitrate were each dissolved in ion-exchanged water to a concentration of 1 mo 115 t. One portion of yttrium chloride aqueous solution, two portions of barium nitrate, and three portions of nitric acid aqueous solution were taken to prepare a mixed aqueous solution.

Then, 957 g of Shu r1i dihydrate (stoichiometric amount of 1.
1 times) was added to the aqueous solution to coprecipitate yttrium, barium, and copper oxalates while adjusting the DH to 6.5.

The obtained precipitate was filtered, washed with water, and then calcined in air at a temperature of 900°C for 12 hours to obtain a composition (Y□, 33Ba
□, 67) A composite oxide containing CuO2,27 was obtained. The composite oxide was then ground into powder with an average particle size of 1 μm using an automatic punch and a Geno 1-mill.

The composite oxide 40 (J is a dimethylformamide solution (polyacrylonitrile content 10% by weight solution) of polyacrylonitrile (homopolymer, average molecular ff 110,000)
100 g was added and kneaded for 3 hours using a kneader to obtain a homogeneous mixture.

The mixture was extruded into a 40% by weight aqueous solution of dimethylformamide through a die having a diameter of 2 mm to obtain a linear composite oxide-polyacrylonitrile composite having a diameter of 500 μm.

The composite was then heated at a temperature of 930'C in an oxygen atmosphere for 12 hours to obtain a composite oxide wire.

When an electrode was attached to the wire and the electrical conductivity was measured in a taliostat, it was found that Tc (resistance zero temperature > 92 k,
It was found to be a superconductor with J Cl 600 A/cm2.

Example 2 Yttrium oxide 226 (], barium nitrate 1045 g
, and 477 g of cupric oxide were mixed in a ball mill at a temperature of 900°C for 12 hours in air to obtain the composition (Yo, 338 aO, 67> CuO2,3
A composite oxide having 0 was obtained.

The composite oxide 500 (J is a copolymer of polyurethane [(hexamethylene diisocyanate-polytetramethylene glycol (average molecular weight 11,300) (average molecular weight 50,000)
] was mixed with 1 kg of a polymer solution (polymer content 12% by weight) dissolved in a mixed solvent of toluene and methyl ethyl ketone (toluene/methyl ethyl ketone = 3/7) using a strong stirrer to obtain a homogeneous mixture.

The mixture was then continuously fed into isopropanol through a die having holes with a diameter of 500 μm, and stretched for 3
A linear composite oxide-polyurethane composite having a diameter of 5 μm was obtained.

The composite was then heated at a temperature of 930'C in an oxygen atmosphere for 12 hours to obtain a composite oxide wire. Copper was vacuum deposited on the surface of the bonded oxide wire to provide a copper coating with a thickness of 5 μm.

When the copper-coated wire was cut into 6 mm length and the change in magnetic susceptibility with temperature was measured using a vibrating magnetometer, it showed a diamagnetic transition at 85 k, and a magnetic susceptibility of -6 at 77 k and H=10 oersteds.
, 5×10″3 emu/g (after weight of gold oxide).

Example 3 Erbium oxide 383g, barium nitrate 1045g,
Cu
A composite oxide having a molecular weight of 02.3 was obtained.

Polyvinyl butyral (average molecular weight 50,000) was added to 500 g of the composite oxide in a toluene-methyl ethyl ketone mixed solvent (
1 kg of a polymer solution (polymer content: 12% by weight) dissolved in toluene/methyl ethyl ketone (1) was added and mixed in a kneader to obtain a homogeneous mixture. .

Next, the mixture was continuously fed into heated air at 50° C. through a die having holes with a diameter of 1.7 mm to obtain a linear composite resistor-borivinyl butyral composite with a diameter of 500 μm.

Further, the composite was heated in an oxygen atmosphere at a temperature of 930° C. for 12 hours to obtain a composite oxide wire.

When an electrode was attached to the wire and its electrical conductivity was measured in a cryostat, it was found to be a superconductor having Tc (zero resistance temperature > 90 k).

[Effects of the Invention] As explained above, according to the method of the present invention, a superconducting ceramic wire can be easily manufactured.

Claims (1)

[Claims] A method for producing a superconducting ceramic wire, which comprises spinning a polymer solution containing dispersed superconducting ceramic powder.