JPH01122512A - Oxide superconducting fiber - Google Patents

Abstract

PURPOSE:To obtain an excellent oxide superconductor with the fiber strength of 1MPa or above and the ductility of 0.5% or above by using the fiber spinning technique and the ceramic molding technique. CONSTITUTION:A material containing (La, Ba)2cCuO4 or expressed by a general formula LnBa2Cu3O7-x (where Ln is one kind of Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm and 0<x<=0.5) or containing Y2O3, Y(NO3)2 or the like, BaCO3, Ba(NO3)2 or the like, CuO, Cu(NO3)2 by heat treatment is pulverized to the grain size of 0.2mum or below, it is dispersed in a polymer binder of polyvinyl alcohol copolymer or the like into fibers and baked to remove the binder, and fibers with the fiber strength of 1MPa or above, preferably 5MPa or above, the ductility of 0.5% or above, preferably 2.5% or above, and the porosity of 10vol.% or below are obtained. Oxide superconducting fibers with the critical temperature of 80K or above and the critical current of 10A/cm<2> or above in the nonmagnetic field are obtained according to this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to oxide superconducting fibers that can be used in superconducting magnets and superconducting power transmission lines.

B. Prior art Conventionally, the highest critical temperature of a superconductor is Nb3Ge at 23.
3K was the best. As a practical material, Nb3Sn1
7K was the best. Using conventional materials required cooling with liquid helium.

Recently, it has been discovered that oxide superconductors have extremely high critical temperatures, and research in this field has become active. As a material with a high critical temperature, 40 class superconductor (La+-zsrz)2clJOt [Chem
.

Lett, 429 (1987)], Ba2YCu3O as a class 90 superconductor? --[Phys, Rev, L
ett, 58 (1987) 405] has already been found. With the advent of high-temperature superconducting materials in the 1990s, liquid nitrogen (
77K).

In addition to Y, Lu, Yb, Tm, Er, etc. also have 9
Superconductivity phenomena that appear to be on the order of zero have already been observed.

Applications of high-temperature superconductivity can be broadly divided into electronics applications, such as Josephson devices, and electrical equipment applications, such as superconducting generators, magnetic levitation trains, and superconducting power transmission lines. Application to the electronics field is also a very important issue, and the application of high-temperature superconductors in particular will begin with application to the electronics field. However, 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 NMR.
-, CT, etc. 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 drastic improvement in economic efficiency will open up new fields of application or application to superconducting power transmission lines.

However, in order for the superconductor to be used in a magnet, it is required that the superconductor be a wire that can be wound around the magnet. Although various wire and cable technologies have been established for superconducting materials (metals or intermetallic compounds) used at conventional liquid helium temperatures, recent high-temperature superconductors are oxide ceramics,
Conventional technology for making wires from superconducting materials cannot be applied.

By the way, in order to achieve essential stabilization of the superconducting state within the wire, it is advantageous for the fiber to be thinner, but if such a wire is made thinner, the strength and elongation inevitably decrease. .

For example, conventional superconducting materials with low critical temperatures are usually used at a thickness of about 20 μm or less for use as DC magnets, and for use as AC magnets, hysteresis loss must be reduced. Therefore, usually 0
．． Although the oxide high-temperature superconductor of the present invention has a high critical temperature, it can be used in filaments with a diameter of about 6 μm. However, the upper limit of this is also about 200 μm, and more preferably a filament of 0.0011 m or less is desired, but when such thinning is attempted, the problem of a decrease in strength and elongation cannot be avoided.

=3- Conventionally, as a method of making wire rods from such oxide high-temperature superconductors, a method has already been proposed in which holes are made in a silver alloy ingot, filled with ceramic powder to make wire rods, and then heat treated.

However, when high-temperature superconductors are packed into hollow tubes made of metal such as silver and made into wires, (1) it is extremely difficult to make ultra-fine wires with a diameter of 100 μm to 200 μm or less, and (2) the high-temperature superconductors may break. It is difficult to achieve a state in which conductivity is uniform over the entire wire range without causing any damage.As a result of these two extremely major problems, oxide superconducting fibers with excellent strength and elongation have not been successfully obtained. Ta.

Problem 1 to be Solved by the C0 Invention Under such circumstances, the present invention aims to provide ultrafine fibers of oxide high temperature superconductors having excellent strength and elongation.

Means for Solving Problem D9 The inventors of the present invention made extensive studies in view of the above objectives, and by combining fiber spinning technology and ceramic molding technology,
As a result of attempts to thin the oxide superconductor, the fiber strength was 1.
The present invention has been completed by obtaining an oxide superconducting fiber with excellent strength and elongation, which has an M P a or more and a fiber elongation of 0.5% or more. The present invention will be explained in detail below.

The oxide superconductor fiber of the present invention has a fiber strength of] M
Second, it is essential that the fiber elongation is 0.5% or more. If the value is outside the range of the present invention, it is not practical.

A more preferable fiber strength is 5 MPa or more. A more preferable fiber elongation is 2.5% or more. Also, the critical temperature (
It is more preferable that Tc) is 35 or less, preferably 80 or less. In addition, in the absence of a magnetic field, the critical current (Jc) is more than IA/cm2, more preferably IOA/cm2 or more.
More preferably, it is cm' or more. Also, the porosity is 1
More preferably, it is 0% by volume or less, preferably 5% by volume or less.

The diameter of the oxide superconducting fiber of the present invention is not limited in any way, but in view of practicality, the diameter is usually 1000 μm or less.

The preferred diameter is 500 μm or less, and the more preferred diameter is 2
00μm or less, the preferred diameter of Toriwa () is 10011m
It is as follows. Although there is no limit to the lower limit, it is usually 1 μm or more.

The greatest feature of the oxide superconducting fiber of the present invention is that it has excellent strength and elongation even though it is an extremely thin fiber as described above, but surprisingly, the fiber of the present invention has such Although it is an extremely thin fiber, it has excellent strength and elongation properties, so it does not require any strength support, and as such, it can be used as a single fibrous material without any support. It is durable and has excellent practicality. Of course, this does not preclude the use of a support in combination.

The oxide superconducting fiber of the present invention is not limited in any way to its manufacturing method, but examples of the manufacturing method include powder of an oxide superconductor or powder of a substance that can become an oxide superconductor by heat treatment. After dispersing in a polymer binder, it is made into fibers by fiber spinning technology, and the polymer binder is removed by firing. In this case, the manufacturing method may be an aqueous solution dispersion method, an organic solvent dispersion method, a polymer melt dispersion method, etc., depending on the type of powder dispersion medium.
Depending on the type of spinning method, wet spinning, dry-wet spinning, dry spinning, melt spinning, etc. can be employed in various combinations.

The oxide superconductor mentioned in item 1 is not particularly limited as long as it forms a ceramic sintered body through heat treatment and exhibits a superconducting phenomenon below a certain temperature.
Among these, those containing copper oxide are preferred.

Specifically, (La, Ba), Cu14 and general formula LnB
a, Cu307-, (However, Ln is Y, 1., u,
Yb, Tm, Er, Ho, Dy.

At least one of Gd, Eu, and Sm, χ is 0〈χ≦
Represents 0.5. ). ”
- Part of each of Ln, Ba, Cu, and 0 may be replaced by F or the like.

Further, examples of the substance that can be turned into an oxide superconductor by heat treatment described in item 1 include those made of oxides, nitrates, carbonates, etc. of the respective metals forming the oxide superconductor.

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

At least one type of Sm) (b) Ba oxide, nitrate or carbonate; and (c) Cu oxide, nitrate or carbonate. The above (b) may be Ba acetate or fluoride. In addition, Cu gluconate or fluoride may be used as 1.(c).

More specifically, as (a) above, y2o3°Y(N
o3) 2, etc., as well as "1.(b)" BaCO3°Ba(NO3)2. BaF2 etc. are Cub as the above (C).

Examples include CI(NOs)t, CuF2.2H70, and the like.

Each of these components may be mixed and used in such a manner that the composition ratio of the oxide superconductor is obtained.
The effect will be greater if the material is calcined for 1 hour to 5 hours at a temperature of 00°C to 1000°C.

In order to improve the performance of the oxide superconducting fiber of the present invention, it is extremely important to reduce the porosity of the fiber. By reducing the porosity, the performance of oxide superconducting fibers can be significantly improved. In order to reduce the porosity of oxide superconducting fibers, it was necessary to use a precursor with a small particle size.

In this sense, the powder of the above-mentioned oxide superconductor, or the powder of a substance that can be turned into an oxide superconductor by heat treatment, has an average particle size of 15 μm or less, preferably 1 μm or less, and more preferably 0.5 μm or less. 5 μm or less, particularly preferably 0.2 μm or less, is used.
This is desirable because the porosity of the resulting fibers can be reduced and, in turn, the strength and elongation properties and Jc can be increased.

In addition, the polymer used as the binder is one that is soluble in water or an organic solvent, or is thermoplastic, has the property of dispersing and holding the above-mentioned inorganic powder without agglomerating it, and is suitable for spinning. Mention may be made of all polymers that can be made into fibers.

Specific examples include polyvinyl alcohol copolymers, hydroxypropylcellulose, hydroxyethylcellulose, methylcellulose, polyester, polyamide, polyethylene, polypropylene, polystyrene, polyacrylic ester, polymethacrylic ester, polyvinylpyrrolidone, and the like. It is also possible to use various dispersants in combination for the purpose of maintaining the dispersion of the inorganic powder.

As a method for firing the fiber after spinning, for example, in the presence of oxygen,
An example is a method of firing at a temperature of 9506C to 1000C for several minutes to several hours, preferably several minutes to several tens of minutes, followed by slow cooling.

E. Effects and Effects of the Invention The oxide superconducting fiber of the present invention has excellent strength and elongation and good flexibility, and is extremely suitably used as a superconducting fiber for superconducting magnets or superconducting transmission lines. Although the fibers may be used alone, it is preferable to wrap each fiber with a metal such as copper or aluminum and use it as a stabilized superconducting wire.

Specific applications of the oxide superconducting fiber of the present invention include MHD power generation, magnetic floating train, superconducting generator, NM
Examples include R-CT, high energy accelerator, and the like.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Measurement method: The critical temperature (Tc) and current density (Jc) of the superconducting fiber were determined by measuring the electrical resistance of the superconducting fiber using a standard four-probe 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+0007% 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.

Y2O320g, BaCO369.9g and Cu0
After thoroughly mixing 113.3 g of the mixture, it was calcined at 950° C. for 5 hours, then ground and passed through an 846 mesh filter to obtain calcined powder with a diameter of 15 μm or less.

Reference example 2 Y20320g, BaCO369.9g and CuO
After thoroughly mixing 43.3 g of YBa, Cu307-
, an oxide superconductor was obtained. This was pulverized and passed through a 846 Metsushiko filter to obtain oxide superconductor powder with a diameter of 151 m or less. Reference example 3 Y(NOs)3'6Hz010g, Ba(NO3)2
13.6g and Cu(NO3)2-3H2018,9
Dissolve each g in distilled water, mix, and then add a total of 30
0m (as an aqueous solution of 2. Stiff.

into a syringe fitted with a 0.8mm diameter needle.
A fine coprecipitate was obtained by injecting 10.7 mol/Q of 2Go into 300 mQ of an aqueous solution. At this time, the pH power of the system (7
KOI (an aqueous solution was added as appropriate) so that the KOI was ~8. The obtained powder was filtered, washed three times with water, washed with alcohol, and then dried at 45°C. Subsequently, it was calcined at 850°C for 2 hours. A fine powder with a particle size of 0.2 μm or less was obtained.

=13-12 - Example 1 10 g of the powder of 15 μm or less prepared in Reference Example I was dispersed in 15 g of distilled water. (This is called liquid A) Separately prepared 5% polyvinyl alcohol (hereinafter referred to as PVA)
(Polymerization degree 1700, saponification degree 98.5 mol%) Aqueous solution 1
004 g of polyoxyethylene (10) octylphenyl ether and 0.04 g of sodium dodecyl sulfate were added to 5 g and mixed. (This will be referred to as Solution B.) Subsequently, Solution A was added to BtL, and the total amount was concentrated to 30 g on a hot plate while stirring well to obtain a stock solution.

Next, 20g/ρ of Na0)1 and 400g/12 of Na2
An aqueous solution containing SO4 kept at 40°C was used as a coagulation liquid, which was wet-spun into filaments and wound up. Then 100g/θ of H, SO, and 300g/12 of Na,
After neutralization in an aqueous solution containing SOt, it was washed with water and wound up on a bobbin. After drying this filament in a dryer at 50°C, it was placed in a 980°C oven for 5 minutes, and then heated to 100°C/
Cooled to room temperature under oxygen gas flow at the current speed,
A μm oxide superconducting fiber was obtained.

The critical temperature (Tc) of this fiber is 83 and the critical current (Jc) I, OA/cm'' at 77K!
:there were. Further, the tensile strength was 2.5 MPa and the elongation at break was 3.0%.

Example 2 Using the oxide superconductor powder prepared in Reference Example 2, PVA
A diameter of 100 μm was prepared in the same manner as in Example I except that a polymer with a degree of polymerization of 2400 and a degree of saponification of 98.5 mol% was used.
oxide superconducting fibers were obtained.

The Tc of this fiber is 81 and the Jc at 77K.
It was 0.4A/cm2. Also, the tensile strength is l,
At 0 MPa, the elongation at break was 0.5%.

Example 3 1.0 g of powder having an average particle size of 0.2 μm or less prepared by the coprecipitation method of Reference Example 3 was dispersed in 15 g of distilled water.

(This will be referred to as Solution C) 10 g of a separately prepared 5% PVA (polymerization degree 3300, saponification degree 987 mol%) aqueous solution, 5 g of distilled water, 0.06 g of polyoxyethylene (10) octylphenyl ether, and 0.06 g of sodium dodecyl sulfate.
g and mixed. (This will be referred to as Solution D.) Subsequently, Solution C was added to Solution D, and the total amount was concentrated to 35 g on a hot plate while stirring well to obtain a stock solution.

Next, 20g/ρ of N a OH and 400g#! Na,
An aqueous solution containing SOt kept at 40° C. was used as a coagulation liquid, which was wet-spun into filaments and wound up. Then 100g/(! of H3SO, and 300g/ρ of Na2S
After neutralization in an aqueous solution containing O4, it was washed with water and wound up on a bobbin. After drying this filament in a dryer at 50°C, it was placed in a furnace at 980°C and held for 5 minutes, and then cooled to room temperature under a flow of oxygen gas at a rate of 100°C/hour to obtain an oxide superconducting fiber with a diameter of 80 μm. Ta.

The Tc of this fiber is 84 and the Jc at 77 is 1 [
It was 14A/cm2. Also, the tensile strength is 20MPa.
The elongation at break was 26%.

Patent applicant RiRashi Co., Ltd.

Claims (1)

[Scope of Claims] (1) An oxide superconducting fiber characterized by having a fiber strength of 1 MPa or more and a fiber elongation of 0.5% or more. (2) The oxide superconducting fiber according to claim 1, which has a fiber strength of 5 MPa or more. (3) Fiber elongation is 2.
The oxide superconducting fiber according to claim 1, which has a content of 5% or more. (4) The oxide superconducting fiber according to claim 1, which has a critical temperature of 80K or higher. (5) The oxide superconducting fiber according to claim 1, wherein the critical current is 10 A/cm^2 or more in the absence of a magnetic field. (6) The oxide superconducting fiber according to claim 1, which has a porosity of 10% by volume or less.