JPH01176606A - Manufacture of oxide superconductive fiber - Google Patents

Abstract

PURPOSE:To make it possible to obtain a superfine oxide superconductive fiber easily by using a solution including a high polymer compound in which an oxide superconductor or a substance to be an oxide superconductor by heat- treatment is scattered or solved as a spinning material solution, spinning in a dry type spinning to obtain a precursor fiber of a superconductive fiber, and then applying a heat treatment. CONSTITUTION:An oxide superconductor or a substance to be an oxide superconductor by heat-treating is scattered or solved in a solution including a high polymer compound to produce a spinning material solution, which is dry-spun into a precursor fiber of a superconductive fiber, and after that, a heat treatment is applied. The oxide superconductor or the substance to be an oxide superconductor by heat-treating to be used is preferably used as a powder, especially a powder less than 15mum, preferably less than 1mum, and more preferably as a micropowder less than 0.5mum. In such a way, a superfine wire material of an oxide superconductor can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field - The present invention relates to a method for producing an oxide super-WL conductor made into a wire that can be used for superconducting magnets, superconducting power transmission lines, etc.

Nb3Ge or Nb3Sn has traditionally been used as a superconductor.
Intermetallic compounds such as However, the critical temperature (Tc) of these materials is extremely low, at most 23.3K (Nb5Ge), and when these materials are used, industrial production is difficult and cooling with liquid helium, which is less economical, is required. This has been a significant constraint on the use of these materials for a wide range of industrial applications.

Recently, it has been discovered that oxide superconductors have extremely high critical temperatures, and research in this field has become active. Materials with high critical temperatures (hereinafter abbreviated as high-temperature superconducting materials) include superconductors of grade 40 (La
+-zsrr)zcuoa [Chem, Lett,
.

429 (19B?) Co, 90 class superconductor is Ba
2Y+Cu307-, [Phys, Rev, Lett
, 58 (1987) 405] has already been found, and 90
Superconducting phenomena of the highest order have already been observed.

With the advent of 90-grade high-temperature superconducting materials, liquid nitrogen (77K
), and there are prospects that industrial problems in cooling will be greatly improved.

U tries to decide. Problem 1: Applications of high-temperature superconductivity can be broadly divided into applications in the electronics field, as typified by Josephson devices, and applications in the electrical equipment field, as typified by superconducting generators, magnetic levitation trains, and superconducting power transmission lines. be done.

The application of high-temperature superconductivity to the electronics field is a very important issue, but when considering the magnitude of the impact it will have on industry and society, the application of high-temperature superconductivity to electrical equipment is important.

Superconducting magnet technology is an elemental technology for the application of high-temperature superconductivity to electrical equipment. Things that use superconducting magnets include MHD power generation, magnetic levitation trains, high-energy particle accelerators, superconducting generators, superconducting transformers, and NM.
Examples include R-CT. If high-temperature superconductors can be used in the field of magnets, the economic efficiency of superconducting magnet application equipment will be greatly improved. It is also expected that the dramatic improvement in economic efficiency will open up new application fields or applications to superconducting power transmission lines.

In order to use a high-temperature superconductor in a magnet, it must be a wire that can be wrapped around the magnet. Furthermore, in superconducting magnets, the interlayer that is of great practical importance is the stabilization of the magnet.

In conventional intermetallic compound superconductors such as Nb1Ge or Nb*Sn, for example, Cu5n alloy rod and Nb
b or Nb alloy rods are tightly bundled and heat treated to form Nb5
After forming a Sn compound layer, the superconductor is made into a wire by a very complicated method of repeating the drawing process many times to make the wire into a wire.

However, since high-temperature superconductors, ie, oxide superconductors, are made of ceramics, they have the problem of being significantly more difficult to form into wires than conventional superconductors.

In order to solve these problems, a method has already been proposed in which a hole is made in a silver alloy ingot and the material is filled with oxide superconductor powder or powder of a substance that can be made into an oxide superconductor through heat treatment to form a wire and then heat treated. ing.

However, when high-temperature superconductors, that is, oxide superconductors, are packed into hollow tubes made of metal such as silver and made into wires, (1) it is extremely difficult to make ultrafine wires with a diameter of 100 μm to 200 μm or less; (2) ) There were extremely serious problems such as the difficulty of maintaining a high temperature superconductor, that is, an oxide superconductor, without disconnection and with uniform conductivity over the entire line area.

In other words, the production of stabilized superconducting wires is the most important issue for the practical application of high-temperature superconducting materials, and the production of ultrafine wires of high-temperature superconductors, that is, oxide superconductors, is strongly required as the most necessary step for this purpose. The current situation is that

D, cx" - In view of the above-mentioned current situation, the present inventors have conducted intensive studies and have discovered that an oxide superconductor or a substance that can become an oxide superconductor through heat treatment is dispersed in a solution containing a polymer compound. Alternatively, the inventors discovered that oxide superconducting fibers can be obtained by dissolving the solution to prepare a spinning solution, dry-spinning this spinning solution to obtain precursor fibers for superconducting fibers, and then heat-treating the fibers, thereby completing the present invention. reached.

The present invention will be explained in detail below.

The oxide superconductor used in the present invention is one that forms a ceramic sintered body through heat treatment, and is not particularly limited as long as it exhibits a superconducting phenomenon below a certain temperature, but it is particularly one that contains copper oxide. is preferred.

Specifically, (La, Ba)*CuO4 and the formula LnB
a*Cu50? −, (However, Ln is Y, Lu, Yb
, Tm, Er, Ho, Dy.

At least one of Gd, Eu, S+*, χ is 0<
Represents χ≦0.5. ). Part of each of the above Ln, Ba, Cu, and O may be substituted with F or the like.

Examples of substances that can be turned into oxide superconductors by heat treatment include those made of oxides, nitrates, carbonates, etc. of the respective metals forming the oxide superconductors.

Specifically, (a) an oxide, nitrate or carbonate of Ln (however, Ln
n is Y, Lu, Yb, Tm, Er,
Ito, Dy, Gd, Eu.

At least one type of Ss) (b) Ba oxide, nitrate or carbonate; and (c) Cu oxide, nitrate or carbonate. The above (b) may be Ba acetate or fluoride. Also, for (c) above, C
It may be gluconate or fluoride of u.

More specifically, as the above (a), YtOs.

Y(NOs)s etc., and BaC0* as above (b)
.

B11(NOs)*, Balt, etc. are Cub as above (c).

Examples include Cu(No;)t, CuFt.2HtO, and the like.

A spinning stock solution may be prepared by dispersing or dissolving each of these components in a solution containing a polymer compound in a composition ratio of the oxide superconductor. Better effects can be obtained by calcining the mixture at a temperature of 900° C. to 1100° C. for 1 hour to 5 hours before dispersing or dissolving it in the solution.

The oxide superconductor used in the present invention or the substance that can become an oxide superconductor by heat treatment is preferably used as a powder, particularly 15 μm or less, preferably 1 μm or less.
It is preferable to use it as a fine powder with a particle diameter of μ- or less, more preferably 0.5 μm or less.

Examples of the polymer compounds used in the present invention include polyacrylonitrile, polyethylene, polypropylene, polyamide, polyester, etc., polyvinyl alcohol polymer (hereinafter, polyvinyl alcohol may be abbreviated as PVA), methylcellulose-snoethyl methyl cellulose, etc. Among them, PVA-based polymers are most preferably used.

The degree of saponification and degree of polymerization of the PVA polymer is usually 70 to 100 mol%, preferably 85 to 100.
mol%, most preferably 95-100 mol%, degree of polymerization 500-20000, preferably 1000-150
Selected from the range 00.

The polyvinyl alcohol polymer in the present invention includes not only ordinary unmodified polyvinyl alcohol but also so-called modified polyvinyl alcohol. Examples of the modified polyvinyl alcohol include saponified copolymers of vinyl acetate and a comonomer copolymerizable with vinyl acetate. Comonomers include vinyl esters other than vinyl acetate (for example, vinyl propionate, vinyl stearate, vinyl benzoate, vinyl saturated branched fatty acids, etc.), unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, or alkyl esters thereof. , maleic acid,
Unsaturated polycarboxylic acids such as maleic anhydride, fumaric acid, itaconic acid, or their partial or complete esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, olefin sulfonic acids (e.g. ethylene sulfonic acid, allyl sulfonic acid, (methallylsulfonic acid, etc.) or its salts, ethylene, propylene, butene, α-octene, α-dodecene, α-
α-olefins such as octadecene, vinyl ethers,
Examples include silane-containing monomers. The proportion of these comonomers in the copolymer is less than 20 mol %, preferably less than 10 mol 5 .

Another group of modified polyvinyl alcohols are post-modifications of vinyl acetate homopolymers or saponified products of the aforementioned copolymers. Examples of post-modification include acetalization, urethanization, phosphoric acid esterification, sulfuric acid esterification, and sulfonic acid esterification.

The spinning dope used in the present invention contains an oxide superconductor (preferably in powder form) or a substance that can become an oxide superconductor by heat treatment (preferably in powder form). It can be prepared by dispersing or dissolving the molecular compound in a solution.

The solvent in the solution containing the polymer compound of the present invention includes:
It means water or a solvent other than water that can dissolve the polymeric compound that is used.

As solvents other than water, alcohols, ketones, ethers, aromatics, amides, amines, sulfones, etc. can be used without particular limitation. These also include mixed solvents containing water in an appropriate proportion.

In the present invention, polyvinyl alcohol-based polymers are preferably used as the polymer compound, but in this case, water, dimethyl sulfoxide, glycerin, ethyl
Solvents such as hornoglycol, diethylene gelicol, N-methylpyrrolidone, and dimethylformamide are advantageously used alone or as a mixed solvent.

Dry spinning as referred to in the present invention includes a method of extruding or drawing out the spinning stock solution through a die or into the air or gas using a guifree device.
It is not limited to various conditions at all.

The spinning draft is O. 1 to 2,0 is good, preferably 0,
8 to 1.2 is good.

The precursor fibers are then heat treated. Of course, there is no problem in stretching the film as appropriate prior to heat treatment. The heat treatment conditions include, for example, 95% in the presence of oxygen.
An example is a method of firing at fA degree of 0° C.-LIGQoC for several minutes to several hours, preferably several minutes to several tens of minutes, and then slowly cooling.

Although the diameter of the oxide superconducting fiber obtained by the production method of the present invention is not limited in any way, in view of practicality, the diameter is usually 1000 μm or less. A preferred diameter is 500 μm or less, a more preferred diameter is 200 μm or less, and an especially preferred diameter is 100 μm.
m or less. Although there is no restriction on the lower limit, it is usually 14 m or more.

The weight ratio of the above-mentioned oxide superconductor or a substance that can become an oxide superconductor by heat treatment and the polymer compound in the spinning stock solution is 15% by weight or less of the latter to the former,
3% by weight or more, preferably 10% by weight! n% or less, 3% by weight
It is preferable that the values are staggered so that the above values are met.

Further, when preparing the above-mentioned spinning dope, it is permissible to use a dispersant of the above-mentioned oxide superconductor or a substance that can become an oxide superconductor by heat treatment. As the dispersant in this case, anionic emulsifiers, nonionic emulsifiers, and cationic emulsifiers can be used. For example, polyoxene ethylene (10) octylphenyl ether, sodium dodenol sulfate, etc. can be used. Furthermore, polymer-based dispersion stabilizers such as polyacrylic acid and its salts, polystyrene, neutralized products of copolymers of maleic anhydride, and neutralized products of maleic anhydride-ibutene copolymers can also be used.

The total solid content concentration in the above-mentioned spinning dope is not particularly limited, but is usually selected from a range of about 20 to 70% by weight.

Continuous precursor fibers can be obtained by drying the above-mentioned spinning dope after dry spinning.

According to the manufacturing method of the present invention, the above-mentioned arbitrary diameter is suitable, the porosity is IO volume % or less, the tensile strength is IMPa or more,
Oxide superconducting fibers having a critical temperature (Tc) of 80 or less can be obtained.

The oxide high temperature superconducting fiber of the present invention has high strength and good flexibility, and is extremely effectively used as a superconducting fiber for superconducting magnets and superconducting power transmission lines. Although the oxide high-temperature superconducting fiber of the present invention may be used alone, it is preferable to wrap a single fiber with a metal such as copper or aluminum and use it as a stabilized superconducting wire. When producing a stabilized superconducting wire, the use of high-temperature superconducting fibers with a diameter of 200 mm or less, preferably 100 μm or less increases the cooling effect and improves the flexibility of the superconducting wire. .

Specific applications of the oxide high temperature superconducting wire of the present invention include MHD power generation, magnetic levitation trains, superconducting generators, N
MR-CT, a high-energy accelerator, can be mentioned again.

The present invention will be explained more specifically from Example 1 below.

The critical temperature (Tc) and current density (Jc) of the superconducting fiber were determined by measuring the electrical resistance of the superconducting fiber using the standard four-terminal method. This terminal was a platinum wire with a diameter of 70 μm, and a silver conductive adhesive was used to adhere the sample. Sample temperature was measured using a (chromel-gold + 0.007% iron) thermocouple.

The tensile strength and elongation of the superconducting fibers were measured using an Instron type tensile testing machine at room temperature, with a chuck distance of 5 mm, and a tensile speed of 0.033 m/sec.

Powder; 5 yarn considerations; Reference example 1 YtOs 20g, BaC0* 89.9g and C
After thoroughly mixing 3.3 g of uO, the mixture was calcined at 950°C for 5 hours, pulverized, and passed through an 846 mesh filter to obtain calcined powder with a diameter of 15 μM or less.

Reference example 2 Y(No,)3・6+1. Olog, Ba(NO3)
213.6g and Cu(NOa)t・3tlt013
．． 9 g of each were dissolved in distilled water and mixed to give a total of 300 mQ aqueous solution. This is 0.3mm in diameter
adult bird, 1) Put 1 into a syringe and add 0.7 mol/
Q KtCO3 aqueous solution 300m0. A fine powder of coprecipitate was obtained by injecting it into the solution. At this time, a Koji aqueous solution was appropriately added so that the pi of the system was 7 to 8. The obtained powder was filtered, washed three times with water, washed with alcohol, and then dried at 45°C. Subsequently, calcination was performed at 850°C for 2 hours, resulting in a temperature of 0.
A fine powder of 2 μm or less was obtained.

Example 1 Y(NO3)+・611.05g, Ba(NO3)2
6.8g.

Cu (Not) t・3) 1 tO 9.5 g was mixed with separately prepared 5% polyvinyl alcohol (hereinafter referred to as PVA) (
Polymerization degree 1700, saponification degree 98.5 mol%) aqueous solution 60
1 g of sodium dodecyl sulfate and 40 g of distilled water were added to the solution. To this, 7.4 g of the calcined powder prepared in Reference Example 1 was gradually added and dispersed while stirring. Subsequently, this dispersion was concentrated while stirring on a hot plate until the total weight became 60 g, and this was used as a spinning dope.

Subsequently, while maintaining the spinning dope at 50° C., the filamentous dope was pulled upward, wound onto a drum covered with a Teflon sheet, and air-dried. Next, this fiber was heated at 980°C under oxygen flow for 5 minutes.
The mixture was held for 10 minutes and cooled to room temperature at a rate of 100° C./hour to obtain an oxide superconducting fiber with a diameter of 801 Zm.

The critical temperature (Tc) of this fiber was 82 and the critical current (Jc) at 77K was 0.4 A/ca''.

Further, the tensile strength was 1.2 MPa and the elongation at break was 2.6%.

Example 2 Powder Log having an average particle diameter of 0.2 μm or less prepared by the coprecipitation method of Reference Example 2 was dispersed in 15 g of distilled water (this was referred to as liquid A). Separately prepared 5% PVA (polymerization degree 33
00, saponification degree 98.7 mol%) aqueous solution log 5 g of distilled water 1 polyoxyethylene (10) octylphenyl ether 0.06 g and sodium dodecyl sulfate 0.06 g
were added and mixed (this is referred to as Solution B). Subsequently, Solution A was added to Solution B, and the total amount was concentrated to 25 g on a hot plate while stirring well to obtain a stock solution.

Next, this stock solution was maintained at 80° C. and dry-spun into a 70° C. air stream to form a filament, which was then wound up. followed by 980
The fibers were placed in a furnace at .degree. C. and held for 5 minutes, and cooled to room temperature under a flow of oxygen gas at a rate of 100.degree. C./II to obtain oxide superconducting fibers with a diameter of 90 .mu.m.

The Tc of this fiber is 8H, and ? Jc at 7 is 20^
/cs'. Further, the tensile strength was 15 MPa, and the elongation at break was 3.1%.

Patent applicant RiRashi Co., Ltd.

Claims (16)

[Claims] (1) A spinning stock solution is prepared by dispersing or dissolving an oxide superconductor or a substance that can become an oxide superconductor through heat treatment in a solution containing a polymer compound, and this spinning stock solution is dry-spun. A method for producing an oxide superconducting fiber, which comprises preparing a precursor fiber for a superconducting fiber and then heat-treating the precursor fiber. (2) The method for producing an oxide superconducting fiber according to claim 1, wherein the oxide superconductor or the substance that can become an oxide superconductor by heat treatment contains Cu. (3) The oxide superconductor has the general formula LnBa_2Cu_3O
_7_-_x (However, Ln is Y, Lu, Yb, Tm, E
At least one of r, Ho, Dy, Gd, Eu, and Sm, and x represents 0<x≦0.5. ) The method for producing an oxide superconducting fiber according to claim 2, which is represented by: (4) The oxide superconductor is YBa_2Cu_3O_7_-
Claim 3 where __x (0<x≦0.5)
A method for producing an oxide superconducting fiber as described in Section 1. (5) Substances that can become oxide superconductors by heat treatment include (a) Ln oxide, nitrate or carbonate (however, Ln
are Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, E
u, Sm) (b) Ba oxide, nitrate, carbonate, acetate, or fluoride; and (c) Cu oxide, nitrate, carbonate, gluconate, or fluoride. A method for producing an oxide superconducting fiber according to claim 2. (6) The method for producing an oxide superconducting fiber according to claim 5, wherein Ln is Y. (7) The method for producing an oxide superconducting fiber according to claim 1, wherein the polymer compound is a polyvinyl alcohol polymer. (8) The diameter of the oxide superconducting fiber is substantially 1000 μm
A method for producing an oxide superconducting fiber according to claim 1, which is as follows. (9) The method for producing an oxide superconducting fiber according to claim 8, wherein the diameter of the oxide superconducting fiber is substantially 500 μm or less. (10) The diameter of the oxide superconducting fiber is substantially 200 μm
A method for producing an oxide superconducting fiber according to claim 9, which is as follows. (11) The diameter of the oxide superconducting fiber is substantially 100 μm
A method for producing an oxide superconducting fiber according to claim 10, which is as follows. (12) The method for producing an oxide superconducting fiber according to claim 11, wherein the diameter of the oxide superconducting fiber is substantially 10 μm or less. (13) The method for producing an oxide superconducting fiber according to claim 1, wherein the oxide superconductor or the substance that can become an oxide superconductor by heat treatment is in powder form. (14) The method for producing an oxide superconducting fiber according to claim 13, wherein the powder has a substantially average particle size of 15 μm or less. (15) The method for producing an oxide superconducting fiber according to claim 14, wherein the powder has a substantially average particle size of 1 μm or less. (16) The method for producing an oxide superconducting fiber according to claim 15, wherein the powder has a substantially average particle size of 0.5 μm or less.