JPH0734333B2 - Method for producing oxide superconducting wire or tape - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an oxide superconducting wire or a tape-shaped body. More specifically, the present invention is
The present invention relates to a method for producing an oxide superconducting wire or tape that is useful for electric wires, coils, various electronic materials and the like.

(Prior Art) Conventionally, various methods have been known as a method for producing a wire or tape-shaped body made of an oxide superconductor.

For example, the raw material powder compounded to be an oxide superconductor is compressed and inserted into a metal pipe, wire-drawn or rolled into a predetermined thickness, and then heat-treated to give the raw material powder an oxide superconductor. A method of manufacturing a wire rod or a tape-shaped body as a multi-core wire structure by converting it into a body and bundling it as it is or from several to several tens, coating with metal, and further drawing and rolling .

In addition, by a method called suspension spinning method, superconducting oxide powder is dispersed together with a dispersant in a PVA water-based or PVA non-water-based solution, which is then spun in a PVA coagulation bath and heat-treated to obtain oxide superconductivity. A method of manufacturing a wire rod is also known.

In addition to these, the oxide or alloy of superconducting composition is melted by a method called melt spinning method, which is extruded from a nozzle and then rapidly cooled and solidified to be formed into a linear or tape shape, followed by heat treatment to superconducting wire or tape. There is a method of manufacturing the shaped body.

Further, by a method called a sol-gel method, a metal acetate having a superconducting composition is used as a raw material, and this aqueous solution is used for 60 to 80
There is also a method of producing a superconducting wire by heating and condensing the mixture into a viscous spinning solution, spinning the solution, and then heat treating the solution.

There is also a method in which a metal having a superconducting composition is adsorbed on a fibrous alginate gel or rayon and then heat-treated to produce a superconducting wire.

There is also known a method of producing a superconducting tape-like body by growing a superconducting precursor phase on a tape-like substrate from a vapor phase by CVD (chemical vapor deposition), PVD (physical vapor deposition), etc., and performing heat treatment. .

(Problems to be Solved by the Invention) However, each of these conventional methods has its own drawbacks and is therefore a reality.

That is, in the case of the method in which the raw material powder of the oxide superconductor is inserted into the metal pipe, many wire drawing and rolling steps are required to obtain a finer wire rod, and the workability is increased. As a result, a crack is generated inside the sheath and the superconductivity is impaired, so that it is difficult to manufacture the superconducting wire into a thin shape.

In the case of the suspension spinning method, the particle size of the superconducting oxide powder to be dispersed and the dispersing method have a great influence on the superconducting property, but it is difficult to form the dispersed state uniformly. For this reason,
It is difficult to obtain uniform superconductivity. In addition to this, nozzle clogging is likely to occur during spinning, and there is a limit to the fineness of the fibers to be formed.

In the case of the melt spinning method, it was very difficult to produce a long fibrous or tape-shaped superconducting material.

In the case of the sol-gel method, it is difficult to solidify into a fibrous state because the spinning solution obtained has a low viscosity. On the other hand, if an attempt is made to concentrate the spinning solution to increase its viscosity, the spinning solution becomes non-uniform, making it difficult to adjust the viscosity.

In the case of a method of adsorbing a metal on a fibrous alginic acid gel or rayon, a continuous treatment leads to a non-uniform composition, so that a batch system is unavoidable, but there is a drawback that productivity is lowered. Also, since the final composition depends on the adsorption power of alginate gel and rayon,
Since the nonuniformity of the alginic acid gel or rayon is directly reflected as the nonuniformity of the composition, it was also difficult to obtain a superconductor having a uniform composition.

Further, when the CVD method or the PVD method is used, there is a problem that special equipment such as a vacuum device, a plasma generator, a raw material heating device is required, and the productivity is low.

The present invention has been made in view of the circumstances as described above, eliminates the drawbacks of the conventional method, and has excellent uniformity and stability,
High quality oxide superconducting wires and tapes can be produced with good productivity by using a spinning solution that is suitable for forming long wires and tapes and can be easily prepared. The purpose is to provide a new manufacturing method.

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides a general formula
M ₁ Ba ₂ Cu ₃ O _7-x (In the formula, M represents Y or a rare earth element,
(x is 0 to 1.0) The composition of the oxide superconductor. A viscous or jelly-like spinning solution is prepared by adding 0.1 times or more of the total moles of the metal element to the solution containing the organic acid salt of the raw material metal element. The present invention provides a method for producing an oxide superconducting wire or tape, which comprises spinning this in an ammonia-containing atmosphere or a dry atmosphere and heat-treating it.

That is, the present invention uses a solution of an organic acid salt of each metal element forming an oxide superconductor, for example, an acetate salt and / or a formate salt, and by adding chitosan to the solution, a long, fine and homogeneous solution is obtained. It is intended to prepare an excellent spinning solution that enables the formation of various fibers. Furthermore, by spinning this spinning solution in a specific atmosphere, the surface adhesion between spun fibers is eliminated and the formability is improved. Alternatively, it improves the productivity of the tape-shaped body.

The raw material metal elements of the composition of the oxide superconductor used in the present invention are Ba and Cu, and M of the general formula M ₁ Ba ₂ Cu ₃ O _7-x .
Is selected from the group of Y and rare earth elements, and more specifically, Y, Nd, Sm, Eu, Gd, Dy, Ho, Er,
Tm, Yb, Lu and the like can be used alone or in combination.

The components of such Y or rare earth elements and the Ba and Cu components which are the other raw material metal elements of the oxide superconductor are solutions containing these organic acid salts, more preferably acetate salts and / or formate salts. To use as. It may be a salt of propionic acid, butyric acid, oxalic acid or the like. It is possible to use the acetate solution or formate solution or the like of the metal elements of each of the constituents alone or as a mixed solution of acetate and formate.

In this case, it is preferable that the amount of the organic acid such as acetic acid or formic acid with respect to the raw material metal element in the solution is excessive, and particularly, it is preferable that the amount of acetic acid and formic acid is equal to or more than twice the equivalent amount of the constituent raw material metal element. is there. Thereby, when chitosan is added to this solution to prepare a spinning solution, the spinning solution can be made viscous or jelly-like to improve spinnability.

A solution containing an organic acid salt of such a composition raw material metal element should be prepared in any amount of an organic acid salt such as an acetate salt or a formate salt or a carbonate salt for each composition raw material metal element of each oxide superconductor. It can be easily produced by dissolving them in an acetic acid aqueous solution or a formic acid aqueous solution.

When preparing a solution containing twice or more equivalents of acetic acid or formic acid with respect to the raw material metal element, for example, Y or an acetate salt of each raw material metal element of the rare earth element component, Ba component, Cu component in acetic acid aqueous solution, Dissolve formate or carbonate.
At that time, the ratio of use of each raw material metal element acetate, formate, carbonate and aqueous acetic acid solution is such that acetic acid containing acetic acid in the same amount or more as the sum of the equivalents of the raw metal element components as acetate or formate. Use an aqueous solution. When carbonate is used as the salt of the starting material metal element, the carbonate releases CO ₂ with acetic acid to become an acetate, and therefore acetic acid containing acetic acid in an amount equal to or more than twice the total equivalent amount of the metal components. Use an aqueous solution. When acetate, formate and carbonate are used together as the salt of the raw material element of the composition, the use ratio of the salt of each raw element and the aqueous acetic acid solution may be similarly determined.

As a matter of course, the raw material metal elements of each composition are blended so as to have the composition of the oxide superconductor.

The amount of water used when preparing such a solution is such that the acetate and formate salts of the raw metal elements in the solution can be completely dissolved. If the amount of water is insufficient and undissolved acetate or formate remains, the composition of the oxide superconductor obtained by the final heat treatment becomes non-uniform, which is not preferable.

In the present invention, chitosan is added to a solution containing an organic acid salt such as an acetate salt and / or a formate salt of the raw material metal element as described above, and the mixture is stirred to prepare a viscous or jelly-like spinning solution. In this case, the chitosan used should be 0.1 times or more the total number of moles of the raw material metal elements of the composition. As a result, the spinning solution is excellent in that it is long and forms fine fibers.
It is considered that this is because the acetate or formate of the starting metal element of the composition reacts with the polymer of chitosan to form a fibrous polymer in which metal ions are stably incorporated in the molecular structure.

The prepared spinning solution is spun in an ammonia-containing atmosphere or a dry atmosphere. The ammonia-containing atmosphere may be, for example, a state in which ammonia gas is mixed in the air. When spinning is performed in this ammonia-containing atmosphere, the surface adhesion between the fibers is eliminated, and the spinnability is improved. It is considered that this is because the surface of the spun fiber is neutralized with ammonia and becomes insoluble in water. Also,
When spinning in a dry atmosphere, it is presumed that the water content on the surface of the fibers is removed to make them insoluble, the surface adhesion between the fibers is eliminated, and the spinnability is improved.

In spinning, a nozzle may be used when forming a wire rod, and a slit may be used when forming a tape-like body.

The spun wire or tape is then fired by heat treatment to obtain an oxide superconductor.

In this heat treatment, first, it is preferable to dry the wire or tape-shaped body by sufficiently evaporating water, acetic acid, formic acid or the like with a dryer or the like. If drying is insufficient, moisture, acetic acid, formic acid, etc. evaporate violently or decompose during the heat treatment to foam, and the denseness of the resulting oxide superconductor decreases, resulting in a fibrous wire or tape form. Can no longer hold.

In the heat treatment after drying, for example, it is preferable to raise the temperature to 950 ° C. and hold it for several hours, then lower it to 300 to 400 ° C. and hold it for 10 to 20 hours, and then rapidly cool it to room temperature. By such heat treatment operation, sufficient superconducting properties can be obtained.

In particular, it is preferable to raise the temperature gradually. If the rate of temperature increase is too fast, foaming occurs during heat treatment, the denseness of the fired product is reduced, and the fibrous wire rod or tape-shaped body cannot be held.

Further, it is preferable that the temperature is lowered to 300 to 400 ° C. and then held for 10 to 20 hours, but the oxygen amount in the crystal structure can be increased by holding such temperature.

Further, thereafter, by rapidly cooling to room temperature, it is possible to suppress the reaction with carbon dioxide gas, water and the like in the air.

Such heat treatment operation can be performed in the atmosphere,
It is preferable to carry out in an oxygen atmosphere because the superconducting property can be further improved.

Although the manufacturing method of the present invention has been described in detail above, various modes are possible for carrying out the present invention. For example, it is possible to control and improve the superconducting property of the oxide superconducting wire or tape-like body to be produced by appropriately setting the diameter of the nozzle during spinning, the rate of temperature increase or the rate of temperature decrease during firing.

Hereinafter, the method for producing the oxide superconducting wire or the tape-shaped body of the present invention will be specifically described with reference to examples. Of course, the present invention is not limited to the following embodiments.

(Example) Example 1 Barium carbonate (1.97 g) and yttrium carbonate (3) were added to 50 ml of an aqueous solution containing 10 ml of acetic acid so that the composition would be YBa ₂ Cu ₃ O _7-x.
Hydrate 1.03 g and copper acetate monohydrate 3.00 g were added. The solution was stirred until it was completely dissolved, and a blue transparent uniform solution was obtained. Next, 2.42 g of chitosan was added to this solution, and when stirred, the viscosity increased and a blue transparent and uniform jelly-like solution was obtained.
Note that these operations were performed at room temperature.

The jelly solution was spun in an atmosphere containing ammonia from a nozzle having a pore diameter of 1.5 mm to obtain blue transparent long fibers having a diameter of 1.5 mm.

The fiber was dried in air and then at 100 ° C. for about 2 days. As a result, the fiber became a dark green fiber with a diameter of 0.5 mm, which was close to black.

This fiber was heated from room temperature to 960 ° C. at a heating rate of 100 ° C./hr and kept at that temperature for 3 hours. Then, the temperature was lowered to 350 ° C. at a temperature lowering rate of 200 ° C./hr, held for 15 hours, and then rapidly cooled to room temperature.

The wire thus obtained was black and had a diameter of about 0.1 mm.

When the superconducting property of this wire was measured, the critical temperature Tc
₍₀₎ is 82K, the critical current density Jc at liquid nitrogen temperature
_(77K) was 0.5 A / cm ² .

Example 2 A tape-shaped body was manufactured in the same manner as in Example 1. This tape-shaped body also exhibited the same superconducting properties as in Example 1.

Examples 3 to 7 NdBa ₂ Cu ₃ O _7-x (Example 3), GdBa ₂ Cu ₃ O _7-x (Example 4), YbBa ₂ Cu ₃ O _7-x (Example 5), DyBa ₂ A wire rod was prepared in the same manner as in Example 1 by mixing the starting metal carbonates and acetates so that the compositions were Cu ₃ O _7-x (Example 6) and ErBa ₂ Cu ₃ O _7-x (Example 7). Was manufactured.

As a result, in each case, an oxide superconducting wire having a uniform and excellent superconducting property was obtained.

(Effects of the Invention) As described in detail above, according to the present invention, a spinning solution that is excellent in uniformity and stability, is suitable for solidification molding of long wire rods and tape-like bodies, and can be easily prepared is used. By doing so, a high-quality and high-characteristic oxide superconducting wire or tape-shaped body can be manufactured with good productivity.

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Claims (6)

[Claims] Claims: 1. A composition of an oxide superconductor represented by the general formula M ₁ Ba ₂ Cu ₃ O _7-x (wherein M represents Y or a rare earth element), and a solution containing an organic acid salt of a metal element. To 0.1% or more of the total moles of this metal element chitosan is added to form a viscous or jelly-like spinning solution, which is spun in an ammonia-containing atmosphere or in a dry atmosphere, and heat-treated. Manufacturing method of wire or tape. 2. M in the general formula of an oxide superconductor is Y, N
The method for producing an oxide superconducting wire or tape according to claim 1, which is selected from d, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu. 3. The composition of an oxide superconductor according to claim 1, wherein acetic acid or formic acid in the solution containing acetate and / or formate of the metal element of the starting material is more than twice the equivalent of the metal element of the starting material. Method for producing oxide superconducting wire or tape. 4. A composition raw material metal element acetate, or formate or carbonate of an oxide superconductor is dissolved in an acetic acid aqueous solution or a formic acid aqueous solution to obtain an oxide superconductor composition raw material metal acetate and / or The method for producing an oxide superconducting wire or tape according to claim 1, wherein a solution containing a formate is obtained. 5. Drying after spinning, heating to 950 ° C. and holding for several hours, then lowering to 300 to 400 ° C. and holding for 10 to 20 hours, and then rapidly cooling to room temperature for heat treatment. )
A method for producing the oxide superconducting wire or the tape-shaped body as described. 6. The method for producing an oxide superconducting wire or tape according to claim 1, wherein the heat treatment after spinning is performed in the air or an oxygen gas atmosphere.