JPH01122511A - Oxide ceramic superconducting fiber - Google Patents

Abstract

PURPOSE:To obtain uniform and high-intensity oxide ceramic superconducting fibers with the diameter of 1000mum or below by using the fiber spinning technique and the ceramic molding technique. CONSTITUTION:A material containing (La, Ba)2CuO4 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 Ln, Ba, Cu in Y2O3, Y(NO3)2 or the like, BaCO3, Ba(NO3)2 or the like, and CuO, Cu(NO3)2 or the like is used. The oxide superconductor powder of the oxide superconductor material powder generated by heating is pulverized to the diameter of 0.2mum or below, it is dispersed in polyvinyl alcohol copolymer or the like and spun into fibers and baked to remove polymer. The diameter of the fibers is set to 1000mum or below, most preferably to 100mum or below. An oxide ceramic superconducting fibers with the critical temperature of 35K or above and the critical current of 1A/cm or above in the nonmagnetic field is obtained according to this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to oxide ceramic superconducting fibers that can be used in superconducting magnets and superconducting transmission lines.

The highest critical temperature of conventional superconductors is 23.3 for Nb3Ge.
K was the best. As a practical material, Nb3Sn 17
K 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. Materials with high critical temperatures include class 40 superconductors (La+-, Sry) 2CLI04[C
hem, L. ett, 429 (1987)], 90-class superconductors such as Ba, YCu307-, [Phys
, Rev, 1. ett, 58 (1987) 405] has already been found. With the advent of 1990-grade high temperature superconducting materials, it became possible to use 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 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. Furthermore, it is expected that new application fields or applications to superconducting power transmission lines will open up due to the dramatic improvement in economic efficiency.

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 a 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.

Incidentally, in order to achieve essential stabilization of the superconducting state within the wire, it is advantageous for the filament to be thin. 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 in order to reduce hysteresis loss. Although the oxide ceramic high temperature superconductor of the present invention has a high critical temperature, it can be used with a filament having a large diameter. However, the upper limit of this is also about 1000 μm, and it is desired that the filament is more preferably 100 μm or less.

Conventionally, as a method for forming such an oxide ceramic high-temperature superconductor into a wire, a method has already been proposed in which a hole is made in a silver alloy ingot, the wire is filled with ceramic powder, and the wire is 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 the conductivity is uniform over the entire wire region without causing any damage.There are two extremely serious problems mentioned above, and oxide ceramic superconducting fibers with a diameter of substantially 1000 μm or less have not been successful in the past. I wasn't getting it right.

C[I will decide. Under such circumstances, the present invention aims to provide ultrafine fibers of oxide ceramic high temperature superconductors.

Means for determining D9 Problem 1 The present inventors have 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 ceramic superconductor, an oxide ceramic superconductor Iff with uniformity, high strength, and a diameter of substantially 1000 μm or less was obtained, and the present invention was completed. The present invention will be explained in detail below.

It is essential that the oxide ceramic superconductor fiber of the present invention has a diameter of substantially 1000 μm or less. If the value is outside the range of the present invention, it is not practical.

A preferred diameter is 5004 m or less. The thickness is more preferably 200 μm or less, most preferably 100 μm or less. Furthermore, the critical temperature in the absence of a magnetic field (Tc
) is 35 or more, preferably 77 or more, and the critical current (Jc) in the absence of a magnetic field is IA/am2 or more, preferably IOA/cm2 or more. In addition, the porosity is 10% by volume or less, preferably 5% by volume.
The following are more preferable.

The greatest feature of the oxide ceramic superconducting fibers of the present invention is that they are extremely thin fibers as described above, but surprisingly, despite being extremely thin fibers, the fibers of the present invention have no It does not require a strong support, and as a single fibrous material without any support, it can be handled satisfactorily and is extremely practical. Of course, this does not preclude the use of a support in combination.

The oxide ceramic superconducting fiber of the present invention has no limitations on the manufacturing method, but examples of the manufacturing method include powder of an oxide superconductor or materials that can become an oxide superconductor by heat treatment. The powder can be obtained by dispersing the powder in a polymer binder, turning it into fibers by a fiber spinning technique, and removing the polymer binder by firing. In this case, manufacturing methods include aqueous solution dispersion, organic solvent dispersion, polymer melt dispersion, etc., depending on the type of powder dispersion medium; and wet spinning,
Wet-dry spinning methods, dry spinning methods, melt spinning methods, etc. can be employed in various combinations.

The above-mentioned oxide superconductor 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, but those containing copper oxide are particularly preferred. .

Specifically, (La, Ba), cuOt and general formula LnB
a, Cu5O, (however, Ln is Y, Lu, Yb,
Tm, Er, Ho, Dy.

At least one of Gd, Eu, and Sm, χ is 0<4
≦0.5. ).

Part of each of the above Ln, Ba, Cu, and O may be substituted with F or the like.

Further, examples of the substance that can be turned into an oxide superconductor by the heat treatment 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, Gd, 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. Also, for (c) above, C
gluconate or fluoride.

More specifically, as (a) above, y, o3゜Y(N
O, l) 3, etc., as in Section 1 (b), BaCO3゜Ba(NO3)2.8aF2, etc. as in (c) above, C
ub.

Examples include CLI (No. 3), CuF2.2H20, and the like.

These components may be used by mixing them so as to have the composition ratio of the oxide superconductor, but the mixture may be calcined in advance at a temperature of 800 to 1000°C for 1 to 5 hours. It is more effective when used.

In order to improve the performance of the oxide ceramic superconducting fiber of the present invention, it is extremely important to reduce the porosity of the fiber. By lowering the porosity, the diameter of the oxide ceramic superconducting fiber can be made extremely thin, and various performances can be greatly 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 oxide superconductor powder described in 1.
Alternatively, as a powder of a substance that can become an oxide superconductor by heat treatment, the average particle size is 15 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less,
It is especially preferable to use a fiber with a diameter of 0.2 μm or less, as this can reduce the porosity of the obtained fibers, thereby making it possible to obtain thin fibers, and also to improve the physical properties of strength, elongation, and Jc.
This is desirable because it can increase the

In addition, the above-mentioned polymer used as a binder is soluble in water or an organic solvent, or is thermoplastic, and has the property of dispersing and maintaining the two series of inorganic powders without agglomerating them. Mention may also be made of all polymers which can be made into fibers by spinning.

Specifically, polyvinyl alcohol copolymers, hydroxypropylcellulose, hydroxydiylcellulose, methylcellulose, polyester, polyamide, polyethylene, polypropylene, polystyrene, polyacrylic ester, polymethacrylic ester, polyvinylpyrrolidone, etc. may be mentioned. Can be done. 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,
Several minutes to several hours at a temperature of 950°C to 1000°C,
Preferably, a method of baking for several minutes to several tens of minutes and then slowly cooling is mentioned.

The oxide ceramic superconducting fiber of the present invention has high strength and good flexibility, and is extremely suitably used as a superconducting fiber for a superconducting magnet or a superconducting power transmission line. 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 ceramic superconducting fiber of the present invention include MHD power generation, magnetic levitation trains, superconducting generators, NMR-CT, high energy accelerators, 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 + 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.

Y2O320g, BaCO369.9g and Cu
After thoroughly mixing 3.3 g of O4, 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 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 an 846 mesh filter to obtain oxide superconductor powder with a diameter of 15 μm or less.

Reference example 3 Y(NO3)3'6H20log, Ba(NO3),
13.6g and CLI (No, ), 3H2018,
Dissolve 9g of each in distilled water and mix, then add a total of 3
It was made into an aqueous solution of 00ml12. Pour this into a syringe fitted with a 0.8 mm diameter needle, and add 0.7 mol/Q of LCO.
3 aqueous solution was injected into 300 m (!) to obtain a fine coprecipitate powder. At this time, KOI +
Aqueous solution was added accordingly. 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℃ for 2 hours, and the particle size was reduced to 0.2μ.
A fine powder of less than m was obtained.

Example 1 Powder of 15 μm or less prepared in Reference Example 1] and Og were dispersed in 15 g of distilled water. (This will be referred to as Solution A) Separately prepared 5% polyvinyl alcohol (hereinafter referred to as PVA) (polymerization degree 1700, saponification degree 985 mol%) aqueous solution 1
5 g of polyoxyethylene (10) ocdyl 12 = enyl ether 0.04 g and sodium dodesol sulfate 0.
04g was added and mixed. (Let this be liquid B) Next, B
Solution A was added to the solution, and the total amount was concentrated to 30 g on a pot plate while stirring well to obtain a stock solution.

Next, 20g/ρ of N'aOH and u+og/σ of Na, S
An aqueous solution containing O4 kept at 40°C was used as a coagulating liquid, which was wet-spun into filaments and wound up. then t
oog/ρ I(, S04 and 300g#2 Na, SO
After neutralization in an aqueous solution containing No. 4, 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/H to obtain an oxide superconducting fiber with a diameter of 100 μm. Ta.

The critical temperature (Tc) of this fiber was 83, and the critical current (Jc) at 77K was 10 A/cm2. Further, the tensile strength was 2.5 MPa and the elongation at break was 30%.

Example 2 Using the oxide superconductor powder prepared in Reference Example 2, PVA
The procedure was the same as in Example 1, 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.
The tensile strength was 1.0M.
Pa, and the elongation at break was 0.5%.

Example 3 10 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 98.7 mol%) aqueous solution, 5 g of distilled water, 0.06 g of polyoxyethylene (10) octylphenyl ether, and dodecyl sulfuric acid. Sodium 0.
06g was added and mixed. (Let this be liquid D) Next, D
Solution C was added to the solution and the total amount was concentrated to 35 g on a hot plate while stirring well to obtain a stock solution.

Next, 20g/f2 Na OH and 400g#! of Na
An aqueous solution containing tSO+ kept at 40° C. was used as a coagulation solution, which was wet-spun into filaments and wound up. Then 100g/f2 H2SO, and aoog/ρ Naz
After neutralization in an aqueous solution containing SO4, 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/
Cool to room temperature under oxygen gas flow at a rate of
An oxide superconducting fiber of m was obtained.

The Tc of this fiber is 84, and the Jc at 77 is 10.
The tensile strength was 20 MPa, and the elongation at break was 2.6%.

Patent applicant RiRashi Co., Ltd.

Claims (5)

[Claims] (1) An oxide ceramic superconducting fiber characterized by having a diameter of substantially 1000 μm or less. (2) The oxide ceramic superconducting fiber according to claim 1, which has a diameter of substantially 500 μm or less. (3) The oxide ceramic superconducting fiber according to claim 1, which has a diameter of substantially 200 μm or less. (4) The oxide ceramic superconducting fiber according to claim 1, which has a diameter of substantially 100 μm or less. (5) The oxide ceramic superconducting fiber according to claim 1, which has a critical temperature of 35 K or higher and a critical current of 1 A/cm^2 or higher in the absence of a magnetic field.