JPH0197321A - Manufacture of superconductive member - Google Patents

Abstract

PURPOSE:To obtain a superconductive member in arbitrary shape having a high critical temperature by using, as raw material, a plural kinds of powder composed of one kind of elements selected in a plurality of groups in the periodic table or compounds including the above element and mixing the powder in liquid so as to form a slurry, thereby depositing the slurry on a substrate as a layer of compound oxide. CONSTITUTION:Powder composed of one kind alpha of elements selected in IIa group in the periodic table or a compound including the element alpha, powder composed of one kind beta of elements selected in IIIa group in the periodic table or a compound including the element beta, and powder composed of one kind gammaselected in Ib, IIb, IIIb, IVa, VIIIa groups in the periodic table or a compound including the element alpha are used for raw material and mixed in liquid so as to form a slurry. A substrate is dipped into the slurry so as to be deposited. The deposited substrate is heated, thereby the raw material is sintered so that a layer of compound oxide is formed on the surface of the substrate. Therefore, it is possible to obtain a superconductive member in arbitrary shape having a high critical temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing superconducting members. More specifically, the present invention relates to a novel method for manufacturing a superconducting member that can effectively utilize a superconducting material with a high superconducting critical temperature.

Conventional technology Under superconducting phenomena, materials exhibit complete diamagnetic properties, and no potential difference appears even though a finite steady-state current flows inside them. Therefore, various applications of superconductors as transmission media with no power loss have been proposed.

That is, its application fields include power fields such as MHD power generation, power transmission, and power storage, power fields such as magnetic levitation trains and electromagnetic propulsion ships, and NMR1π as an ultra-sensitive sensor for magnetic fields, microwaves, radiation, etc. There are many fields that can be mentioned, such as meson therapy, measurement fields such as high-energy physics experimental equipment, etc.

Furthermore, in the field of electronics, typified by Josephson devices, this technology is expected to not only reduce power consumption but also realize devices that operate at extremely high speeds.

By the way, superconductivity was once a phenomenon observed only at extremely low temperatures. That is, Nb, which is said to have the highest superconducting critical temperature Tc among conventional superconducting materials,
Even in Ge, an extremely low temperature of 23.2 K was considered to be the limit of superconducting critical temperature for a long time.

Therefore, conventionally, in order to realize the superconducting phenomenon, superconducting materials have been cooled to below Tc using liquid helium with a boiling point of 4.2. However, the use of liquid helium imposes an extremely large technical burden and cost burden due to cooling equipment including liquefaction equipment, which has hindered the practical application of superconducting technology.

However, in recent years, it has been reported that sintered bodies containing group A elements or oxides of group A elements can become superconductors at extremely high Tc, and the practical application of superconducting technology using non-low-temperature superconductors has been delayed. is about to be promoted. In the examples already reported, it is thought to have a crystal structure similar to that of perovskite oxides [La, Ba) 2c
u○4 or I:La.

Examples include 2NiF type oxides such as Sr]2CUO4.

In these materials, a dramatically higher Tc of 30 to 50 was observed, and in addition, Ba, Y, Cu
It has also been reported that superconducting materials made of oxides have a Tc of 70 or more.

Problems to be Solved by the Invention However, since these superconducting materials are obtained as sintered bodies, they are generally brittle and must be handled with care.

That is, it easily breaks or cracks due to mechanical stress, and particularly when it is made into a wire, it breaks very easily, so there are major restrictions on its actual use.

In addition, with sintered superconducting materials, it is difficult to form a completely homogeneous polycrystalline body consisting only of particles with superconducting properties, and as a general property of superconductors, localization may occur due to external magnetic fields or fluctuations in cooling temperature. The superconducting state may be broken. However, this type of sintered superconducting material has lower thermal conductivity and higher electrical resistance than conventional superconducting materials. Therefore, as mentioned above, at a location where the superconducting state is broken, local heat generation occurs due to the current flowing through the superconductor, and when the superconductor comes into contact with the cooling medium, explosive vaporization of the cooling medium is induced. Therefore, in conventional metal-based superconductors, the superconductor is formed as thin filaments, and many filaments are
Danger was avoided by integrally forming the superconductor with a good conductor such as U, and using it as a heat transfer body and current bypass in case the superconductor was broken.

On the other hand, it is difficult to adopt the above-mentioned configuration with the superconducting sintered bodies with high Tc that have been developed in recent years, and it is currently difficult to use them as wire materials. .

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to create a new material that can use a superconducting material having a high Tc as a wire material with high stability of superconducting properties and a large degree of freedom in shape. The object of the present invention is to provide a structure of a superconducting material.

Means for solving the problem, namely, according to the present invention, a powder of one element α selected from Group A of the Periodic Table or a compound containing the element α, and a powder of an element α selected from Group IA of the Periodic Table. powder of one kind of element β or a compound containing the element β, and a powder of one kind of element β or a compound containing the element β, and
One element T selected from group b, group a, group VIIIa
or a powder of a compound containing the element γ is mixed as a raw material powder in a liquid to form a slurry, and a base material is immersed in the slurry to adhere the raw material powder to the surface of the base material, By heating the base material to which the compound powder is attached, the raw material powder undergoes a sintering reaction, and the general formula: αWβx
Ty δ2 (However, element α is an element selected from Group IIa of the periodic table, element β is an element selected from Group IIIa of the periodic table, and element T is an element selected from Group IIIa of the periodic table. ,nb,
mb, one type of element selected from group VIIIa,
Element δ is ○ (oxygen), and W, X, V, and Z are each 1≦w≦5.1≦x≦5.1≦y≦15.1≦Z≦20
Provided is a method for manufacturing a superconducting member, which comprises manufacturing a superconducting member having a layer of a composite oxide represented by the following formula on its surface.

Operation The method according to the present invention involves immersing a base material in a slurry formed by mixing raw material powders in a liquid to uniformly adhere the slurry to the surface of the base material, and then sintering the raw material powders to form a superconducting material. This is its main feature.

That is, the general formula: α1β8γ, δ2 (However, element α is one type of element selected from Group IIa of the periodic table, element β is one type of element selected from Group 111a of the periodic table, and element T is the periodic table xb, nb,
mb, one type of element selected from group VIIIa,
The element δ is O (oxygen), and wXx, y, and z are each 1≦w≦5.1≦x≦5.1≦y≦15.1≦Z≦20
Based on the fact that the composite oxide sintered body shown by , and then sintered to form the superconducting material as described above.

In addition, as the above-mentioned complex oxide, especially Ba-Y
-Cu, Ba-Dy-Cu or 5r-La-Cu
Composite oxides such as these are listed as exhibiting particularly excellent properties.

However, since it is difficult to fix the raw material powder as it is on the substrate, according to the present invention, the raw material is dissolved in a liquid that has excellent adhesion to the substrate, such as polyvinyl butyral or dibutyl phthalate dissolved in isopropyl alcohol or methyl ethyl ketone as a solvent. By immersing the base material in a slurry formed by mixing powders, the raw material powder is uniformly and effectively applied to the surface of the base material.

Any material can be used as the base material as long as it can withstand the heat during sintering, but especially when the product is used as a superconducting material, it is difficult to use the current bypass during quenching and the heat dissipation path. Considering the function of the base material as a material, it is preferable to use a conductive material. Specifically, various metals, carbon fibers, etc. can be mentioned, but the material is not limited thereto.

In the step of dipping the base material into the slurry, the liquid in which the raw material powder is dispersed is stirred by ultrasonic waves or mechanical means, or the base material is vibrated or It is also preferable to rotate it. Although it varies depending on the adhesion force of the binder, etc., in order to ensure that the raw material powder adheres effectively to the base material until the subsequent process is completed and to improve the superconducting properties of the product, the particle size of the raw material powder should be 30 μm or less. It is preferable that there be.

The quality of the completed superconducting composite oxide can be improved by removing the binder from the base material to which the raw material powder has been attached, such as by heating it at a relatively low temperature. It is also preferable to treat the surface of the base material in advance to make it chemically stable to the superconducting material.

Here, the sintering treatment is preferably carried out at a temperature range with the upper limit being the melting point of the compound having the lowest melting point among the raw material powders, and a difference from this melting point being within 100°C.

This is because if the sintering temperature exceeds the melting point of the material powder, the material will melt or decompose, and the composite oxide that has undergone such a process will not exhibit effective superconducting properties. On the other hand, sufficient solid solution reaction does not occur at temperatures lower than the above range.

It is also known that the properties of superconducting sintered bodies made of composite oxides are greatly influenced by the oxygen content.
From this point of view, it is preferable to perform sintering in an appropriate oxygen-containing atmosphere to control the amount of oxygen contained.

On the other hand, when the shape of the base material is a wire or a plate, the superconducting properties are improved by further subjecting the superconducting material provided with the superconducting composite oxide layer to hot rolling treatment. this is,
This seems to be because the superconducting composite oxide layer was once physically destroyed and then re-sintered, resulting in a finer structure.

Note that the heating temperature during this treatment is preferably a temperature with the upper limit being the melting point of the composite oxide and the difference from the melting point being within 100°C. This seems to be because, in this temperature range, the structure of the composite oxide pulverized by mechanical processing by rolling is re-sintered by an in-phase reaction.

The operations according to the method of the present invention as described above can easily produce a superconducting wire using, for example, a wire as a base material,
Furthermore, this method is well suited for continuous processing. Therefore,
This is a method that can advantageously produce superconducting wires by continuously processing long linear base materials. Also,
When using a superconducting material as an electromagnetic shielding material, it can be advantageously applied by selecting a base material with an appropriate shape.

Embodiment FIG. 1 is a diagram showing the configuration of an apparatus for carrying out the manufacturing method according to the present invention, and is intended to manufacture a long superconducting wire by continuous processing using a linear base material. There is.

The base material 2 supplied from the coiler 1 is immersed in a slurry 5 in a constant temperature bath 4 whose temperature is controlled by a water bath 3, and is then transferred upward, runs through a heating furnace 6, and is heated to an upper drum 7. It is configured so that it can be wound up.

The thermostatic chamber 4 is filled with inert gas supplied from the air supply hole 8 . In addition, an ultrasonic vibration plate 9 is immersed in the slurry 5 in the constant temperature bath 4, and when this device is in operation, vibration is applied to the slurry 5 to prevent the raw material powder from becoming uneven or sinking, and to prevent the slurry 5 from changing its composition. is maintained uniformly. Furthermore, a die 13 is provided near the exit side of the high temperature bath 4 for scraping off excess slurry 5 adhering to the base material.

On the other hand, the heating furnace 6 also includes an air supply hole 10, through which air or oxygen is supplied. That is, although the sintering reaction of superconducting materials, which will be described later, can be carried out in the atmosphere, oxygen is absorbed during the sintering reaction, so it is necessary to supply oxygen.

Therefore, a sufficient amount of air may be supplied as long as a drop in temperature within the heating furnace 6 can be avoided. In addition, this heating furnace 6 is
It is equipped with a relatively low-temperature heater 11 for preheating and debinding, and a high-temperature heater 12 for performing a sintering reaction. It has a long structure.

The superconducting wire was manufactured as follows using a device similar to the one described in "Double Series."

First, as a raw material powder, BaCO2, ¥2 (C03)3
Each powder of CuO was prepared, mixed with polyvinyl butyral and dibutyl slate, and then dissolved using isopropyl alcohol and methyl ethyl ketone as a solvent. This mixture was kneaded for 24 hours using a ball mill, then degassed using a vacuum defoaming machine, and then the viscosity was adjusted.

Viscosity adjustment is basically done by adjusting the temperature of the slurry.
In this example, 800 cps at 40°C was adopted.

Therefore, this slurry was placed in a constant temperature bath of the above-mentioned apparatus, and the constant temperature bath was kept at 40° C., and furthermore, the constant temperature bath was filled with N2 gas to about 1 atm to prevent solidification of the slurry.

For this constant temperature bath, Cu with a diameter of 0.5 mm was used as a base material.
The line was fed continuously. For comparison, the feeding speed of the base material was set to 50 mm/min, 100 mm/min, and 300 mm/min.
The Cu wire coated with the slurry as described above is transferred to the heating furnace at the same speed as each feed rate, and is first transferred to the low temperature heater of the heating furnace 6. 11 to 50 to 200° C. to remove binder. Subsequently, it is sintered by a high-temperature heater 12. Again, the substrate is transported at the same speed as the feed rate. Therefore, in the apparatus of this example equipped with a sintering heater of approximately 30 m length, sintering was performed for approximately 10 hours, 5 hours, 16 hours, 50 minutes, and 25 minutes, respectively, depending on the above-mentioned supply speed. . The heating temperature during sintering is approximately 900℃.
It was ℃.

Each of the wire rods thus obtained was cut by 1 m and used as a sample for measurement.

For measurement, electrodes were placed on both ends of each sample using Ag paste, and after cooling with liquid nitrogen in a cryostat,
After applying electricity to the sample and confirming that the electrical resistance had become completely zero, the temperature was gradually raised, and the critical temperature Tc and the temperature Tci at which the electrical resistance was perfect were measured. In addition, for samples that did not exhibit superconductivity in liquid nitrogen, their superconducting properties were measured after further cooling in liquid hydrogen.

The measurement results are shown in Table 1 below.

Note 2: The mark [*] in the figure means that the measurement was performed using liquid hydrogen.

Effects of the Invention As detailed above, according to the method of manufacturing a superconducting member according to the present invention, superconducting sintered materials, which have a high critical temperature7 but are mechanically fragile, have been severely restricted in processing or molding. The body can be used in any shape.

Further, since the base material of the superconducting member produced according to the present invention is a conductor, the superconducting member is configured to have a current bypass when the superconductivity is broken.

Furthermore, since the method according to the present invention is easily adapted to continuous processing, it can be used extremely effectively for long members such as wire rods.

[Brief explanation of the drawing]

FIG. 1 schematically shows the configuration of an apparatus for carrying out the method for manufacturing a superconducting material according to the present invention as a continuous manufacturing process for wire rods. [Main reference numbers] 1... Coiler, 2... Drum, 3... Water bath, 4... High temperature bath, 5... Slurry, 6... Heating furnace, 7... Drum , 8...N2 gas supply hole, 9...Ultrasonic diaphragm, 10...02 gas supply hole, 11...Low temperature heater, 12...High temperature heater, 13...Dice patent applicant Sumitomo Electric Industries, Ltd.

Claims (21)

[Claims] (1) Powder of one type of element α selected from Group IIa of the Periodic Table or a compound containing the element α, and one type of element β selected from Group III of the Periodic Table or containing the element β Powder of compounds and groups Ib, IIb, IIIb, IVa of the periodic table,
One element γ selected from Group VIIIa or a powder of a compound containing the element γ is mixed in a liquid as raw material powder to form a slurry, and a base material is immersed in the slurry to form a slurry. The powder is attached to the surface of the base material, and the base material to which the compound powder is attached is heated to cause the raw material powder to undergo a sintering reaction. The element β is a selected element from group IIIa of the periodic table, and the element γ is a group Ib, IIb, II of the periodic table.
One type of element selected from groups Ib and VIIIa, element δ is O (oxygen), and w, x, y, and z are each 1≦
The method is characterized by producing a superconducting member having a layer of a composite oxide on its surface, which satisfies w≦5, 1≦x≦5, 1≦y≦15, 1≦z≦20. A method for manufacturing a superconducting member. (2) The compound powder is a powder of one or more oxides of the element α, the element β, and the element γ (where α, β, and γ are each as defined above). A method for manufacturing a superconducting member according to scope 1. (3) The compound powder is a hydroxide, carbonate, sulfate, or nitrate of one or more of the elements α, β, and γ (α, β, and γ are each as defined above). A method for manufacturing a superconducting member according to claim 1, characterized in that: (4) The method for manufacturing a superconducting member according to claim 2 or 3, wherein the raw material powder in the slurry is mixed in the same composition ratio as the composite oxide. (5) The compound powder is an oxide, hydroxide, carbonate, sulfate, or nitrate of one or more of the elements α, β, and γ (α, β, and γ are each as defined above). The method for manufacturing a superconducting member according to claim 1, wherein the composite oxide fired body powder is obtained by pulverizing a fired body obtained by mixing and firing powders of the composite oxide. (6) The method for manufacturing a superconducting member according to claim 1 or 5, wherein the raw material powder has a particle size of 40 μm or less. (7) The superconductor according to any one of claims 1 to 6, characterized in that the raw material powder is mixed with polyvinyl butyral and dibutyl phthalate dissolved in isopropyl alcohol and methyl ethyl ketone as a solvent. Method for manufacturing sex parts. (8) Claims 1 to 7, characterized in that the slurry is stirred or rocked, or the base material is rocked, vibrated, or rotated when the raw material powder is attached to the base material. A method for manufacturing a superconducting member according to any one of the above. (9) The slurry according to any one of claims 1 to 8 is characterized in that the slurry is placed in a constant temperature bath and the temperature is controlled when the raw material powder is attached to the base material. A method for manufacturing a superconducting member. (10) Any one of claims 1 to 9, wherein the slurry and the surface of the base material are protected by an inert gas when the raw material powder is attached to the base material. A method for manufacturing a superconducting member according to item 1. (11) The superconductor according to any one of claims 1 to 10, wherein the base material is surface-treated in advance when the raw material powder is attached to the base material. Method for manufacturing sex parts. (12) The method for manufacturing a superconducting member according to any one of claims 1 to 11, characterized in that the base material is continuously supplied into the slurry. (13) The method for manufacturing a superconducting member according to any one of claims 1 to 12, wherein the base material is a wire rod. (14) The method for manufacturing a superconducting member according to any one of claims 1 to 13, wherein the base material is made of a conductive material. (15) Prior to the sintering process, the base material to which the raw material powder is attached is heated to perform a binder removal process. A method of manufacturing the superconducting member described above. (16) The sintering process has an upper limit of the melting point of the compound with the lowest melting point among the raw material powders, and the difference from the melting point is 100%.
16. The method for manufacturing a superconducting member according to any one of claims 1 to 15, characterized in that the method is carried out at a temperature within a temperature range of .degree. (17) The method for manufacturing a superconducting member according to any one of claims 1 to 16, wherein the sintering is performed in an oxygen-containing atmosphere. (18) The method for manufacturing a superconducting member according to any one of claims 1 to 17, characterized in that the deposition treatment of the raw material powder and the heat treatment are performed continuously. (19) The element α is Ba, the element β is Y, and the element γ is Cu according to any one of claims 1 to 18. A method for manufacturing a superconducting member. (20) The element α is Ba, the element β is Dy, and the element γ is Cu according to any one of claims 1 to 18. A method for manufacturing a superconducting member. (21) The element α is Sr, the element β is La, and the element γ is Cu according to any one of claims 1 to 18. A method for manufacturing a superconducting member.