JPH0531492B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a superconducting material. [Conventional technology and its problems] Superconducting materials have already been used in high-energy particle accelerators,
In MRI-CT physical property research equipment for medical diagnosis, etc.
It has been put into practical use in the form of superconducting magnets. Applications include generators, energy storage and conversion, linear motor cars, magnetic separation devices for resource recovery, nuclear fusion reactors, power transmission cables, magnetic shielding materials, etc.
Furthermore, superconducting elements using the Josephson effect are expected to be applied to ultra-high-speed computers, infrared detectors, low-noise amplifiers, etc., and if these are put into full-scale practical use, they will have significant industrial and social impact. The magnitude of the impact is still difficult to measure. Nb-Ti alloy is a typical superconducting material developed so far, and is currently widely used as a wire for generating magnetic fields up to 9T. Nb−
Tc of Ti alloy (critical temperature at which superconducting state exists)
is 9K. In addition, compound superconducting materials have been developed as materials with Tc much higher than Nb-Ti alloys, and currently Nb ₃ Sn (Tc: 18K) and V ₃ Ga
(Tc: 15K) has been made into wire and put into practical use. Furthermore, a Tc of 23K has been obtained with Nb ₃ Ge. Although efforts have been made to obtain high Tc superconducting materials for many years, Tc23K has become a major barrier to conventional alloy-based and compound-based superconducting materials. Expensive liquid He is required to cool superconducting materials with Tc below 23K.
This hinders the widespread application of superconducting materials. In 1986, Mr. Mu¨ller of IBM Zurich and others proposed Ba-La-
Since the announcement that signs of superconductivity were observed in Cu-O-based oxides, the race to develop oxide-based superconducting materials has accelerated. In 1986, Tc was 40K, but in early 1987, a Y-Ba-Cu-O based superconducting material was developed that exceeded the liquid nitrogen temperature of 77K, and Tc reached approximately 93K. Furthermore, vigorous development has continued since then, and there have been reports of the development of superconducting materials that exhibit superconductivity at room temperature, although there are currently safety issues. The discovery of high-temperature superconducting materials that can be used at liquid nitrogen temperatures has raised expectations for the aforementioned application fields, but for actual application, it is necessary to develop processing techniques such as wire rods and coatings. must be accompanied by [Problems to be solved by the invention] In order to form a film with a superconducting material, it is possible to apply the superconducting material onto a base material by a thermal spraying method or a vapor deposition method. The thickness of the film that can be formed using this method is approximately 1 μm at most, which limits the power supply capacity, and in addition, the film formation rate is slow and it takes a long time to form the desired film. The purpose of this invention is to form a thick film stably,
In addition, it is an object of the present invention to provide a method for producing a superconducting material that can form a film made of a superconducting material on a base material at a high film formation rate. [Means for Solving the Problems] This invention provides a method of spraying onto the surface of a base material by a thermal spraying method.
A film of a composite oxide superconducting material containing a Cu _x O _y group is formed, and then the thus obtained superconducting material consisting of the base material and the film is
Pressure is applied to the superconducting material while heating it to a temperature of 980°C, thereby improving the denseness of the film, and then cooling the superconducting material at a rate of 20°C/min or less in an oxygen-containing atmosphere. It is characterized in that it is cooled at a rapid rate, thereby imparting predetermined superconducting properties to the film. Next, one embodiment of the method for manufacturing a superconducting material according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of the method for manufacturing a superconducting material according to the present invention. Using a plasma spraying apparatus 1 as shown in FIG. 1, Y-Ba-Cu-O
A film 3 of a superconducting material made of an oxide such as a superconductor is formed. In addition, the thermal spraying apparatus 1 may be a gas thermal spraying method other than plasma thermal spraying. The plasma spraying apparatus 1 includes a vacuum vessel 4, a thermal spray nozzle 5 provided in the vacuum vessel 4, a tungsten electrode 6 provided in the thermal spray nozzle 5, and connected between the thermal spray nozzle 5 and the electrode 6. It consists of a plasma power supply 7. A plate-shaped or rod-shaped base material 2 is installed in a vacuum vessel 4 facing a thermal spray nozzle 5, and while the pressure inside the vacuum vessel 4 is reduced, a plasma gas such as argon or helium and Y-Ba are injected into the thermal spray nozzle 5. - Powder of superconducting material made of oxides such as Cu-O (from 10 to
100 μm), and then the plasma power source 7 is activated to generate a plasma arc between the thermal spray nozzle 5 and the electrode 6. Once the superconducting material 8 consisting of the base material 2 and the coating 3 is obtained by the above-described thermal spraying apparatus, the superconducting material 8 is then heated in a heating furnace 10 having a heater 9, as shown in FIG. While heating to a temperature of 500 to 980°C, pressure is applied to the film 3 using a press 11. This increases the degree of adhesion between the particles of the superconducting material sprayed onto the surface of the base material 2.
The porosity of the coating 3 is reduced. Furthermore, the degree of adhesion between the base material 2 and the film 3 also increases. After so-called hot pressing is applied to the superconducting material 8 in this manner, the superconducting material 8 is cooled at a rate of 20° C./min or less in the air or an oxygen atmosphere. As a result, the crystal structure of the film 3 made of the superconducting material becomes orthorhombic. As a result, a superelectric coating 3 is obtained. Here, the heat treatment temperature was set at 500 to 980℃ because
At temperatures below 500℃, it is difficult to obtain homogeneous orthorhombic crystals, and the amount of oxygen vacancies is large, making it difficult to obtain sufficient superconducting properties.
This is because if the temperature exceeds 980°C, the base material and the film will react, the base material will penetrate into the film, and the superconducting property will no longer be exhibited. In addition, the cooling rate was set to 20℃/min or less because
This is because, at a cooling rate exceeding 20°C/min, the risk of cracking in the film increases, the film and the base material are likely to peel off, and the amount of oxygen vacancies in the crystal increases. Next, embodiments of the invention will be described. Vacuum vessel 4 of plasma spraying apparatus 1 shown in FIG.
A copper plate-shaped substrate 2 is set inside the spray nozzle 5, and a mixed gas of argon gas and helium gas (Ar: 20/min, He: 40/min) is continuously supplied as plasma gas into the thermal spray nozzle 5. and plasma power supply 7
A power _of 15 Kw is supplied between the thermal spray nozzle 5 and _{the electrode 6} from Then, the atmospheric pressure inside the vacuum container 4 is
The pressure was reduced to 80 mbar, and a film 3 made of a superconducting material having a film thickness of 150 μm was formed on the surface of the base material 2. Next, the base material 2 and the film 3 obtained in this way
The superconducting material 8 consisting of was taken out from the vacuum container 4, placed in the heating furnace 10, and heated in the atmosphere at a temperature of 500° C. for 30 minutes while being reduced by the press 11 at 5 kgf/mm ² . Next, the superconducting material 8 heated while applying pressure in this manner is heated at 10°C/min.
A plate-shaped superconducting material was produced by cooling at a rate of . Next, another plate-shaped superconducting material was manufactured under the same conditions as in the above-mentioned example except that the heating temperature of the superconducting material 8 was changed to 800°C. A portion of each of the superconducting materials thus produced was vertically cut, the cut surfaces were polished, and the cut surfaces were observed with an optical microscope to examine the porosity. The results are shown in Table 1 together with the case where the superconducting material 8 was not subjected to hot press treatment, that is, the case where it was left as thermally sprayed.

[Table] As is clear from Table 1, according to the method of the present invention, by hot-pressing the superconducting material, the porosity of the film was found to be smaller than when it was sprayed as is. . Next, a test piece (base material thickness: 2 mm,
A piece (film thickness: 0.15 mm, width: 5 mm, length: 50 mm) was cut out, immersed in liquid nitrogen (77K), and examined for critical current density (Jc) using the four-terminal method. The results are shown in Table 2 together with the as-sprayed case.

[Table] As is clear from Table 1, according to the method of the present invention, the porosity of the film is reduced and the adhesion between the particles of the superconducting material is increased by the hot press treatment, so that (Js) It was found that the value was larger than that of the as-sprayed case. Next, take a test piece with the same dimensions as the above test piece.
An adhesion strength test between the base material 2 and the film 3 was conducted in accordance with ASTMC633-79. The results are shown in Table 3 together with the as-sprayed case.

[Table] As is clear from Table 3, according to the method of the present invention, the adhesion strength between the coating and the base material is higher due to the hot press treatment than when the coating is as-sprayed. Next, a test piece having the same dimensions as the above test piece was subjected to a three-point bending test, and the bending angle of the test piece at the time of cracking of the film was measured, thereby examining the strength of the film. The results are shown in Table 4 together with the as-sprayed case.

〔Effect of the invention〕

As explained above, according to the present invention, by forming the coating by thermal spraying, the thickness of the coating can be increased, and moreover, the coating can be formed in a short time. Furthermore, by hot-pressing the film, the particles of the superconducting material firmly adhere to each other, which reduces the porosity of the film and increases the value of (Jc). When the adhesion strength between the film and the film increases, extremely useful effects are brought about.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing how a film made of a superconducting substance is formed on the surface of a substrate by the method of the present invention, and FIG. FIG. 3 is a cross-sectional view showing a state in which the material is hot-pressed, and FIG. 3 is a front view showing a three-point bending test method. In the drawings, 1... plasma arc thermal spraying device, 2... base material, 3... film, 4... vacuum vessel,
5... Thermal spray nozzle, 6... Electrode, 7... Plasma power source, 8... Superconducting material, 9... Heater, 10
...Heating furnace, 11...Press.

Claims (1)

[Claims] 1. A film of a composite oxide superconducting material containing a Cu _x O _y group is formed on the surface of a base material by a thermal spraying method, and then a film consisting of the base material and the film obtained in this way is formed. While heating the superconducting material to a temperature of 500 to 980°C, applying pressure to the superconducting material,
This improves the density of the film, and then cools the superconducting material in an oxygen-containing atmosphere at a cooling rate of 20°C/min or less, thereby giving the film a predetermined superconductivity. A method for producing a superconducting material, the method comprising: