JPH0531491B2 - - 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 amplification, etc., and if these are put into full-scale practical use, they will have great 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.Additionally, the film formation rate is slow and it takes a long time to form a 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] The present invention provides a method of applying a composite oxide superconducting material containing a Cu _x O _y group onto the surface of the base material while heating the base material to a temperature of 500°C to 980°C. A superconducting material made of the base material and the film, heated to the temperature described above, was heated at 20°C/20°C.
The film is characterized in that it is cooled at a cooling rate of less than min, 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, a film 3 of a superconducting material made of an oxide such as Y--Ba--Cu--O is formed on the surface of a base material 2. Note that the thermal spraying apparatus 1 is capable of other than plasma spraying.
For example, gas spraying or the like may be used. 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 placed in a vacuum container 4, facing a thermal spray nozzle 5, together with a heater 9.
While heating the base material 2 to a temperature of 500 to 980°C with the heater 9, the pressure inside the vacuum vessel 4 is reduced, and a working gas such as argon or helium and a composite containing Cu _x O _y groups are injected into the thermal spray nozzle 5. Powder (10 to 100 μm) of a superconducting material made of oxide is continuously supplied, and the plasma power supply 7 is activated to generate a plasma arc between the thermal spray nozzle 5 and the electrode 6. After obtaining the superconducting material 8 in which the film 3 made of the superconducting substance is formed on the surface of the base material 2 in this way, the heating temperature by the heater 9 is gradually lowered, and the inside of the vacuum container 4 is made into an oxygen-containing atmosphere. maintain,
The superconducting material 8 is gradually cooled at a cooling rate of 20° C./min or less. In this way, when the superconducting material powder is thermally sprayed while heating the base material 2, the molten powder and the base material 2
The adhesion between the film and the film 3 is improved. At the same time, residual stress in the film is reduced, and the occurrence of microcracks in the film can be suppressed. Then, under an oxygen-containing atmosphere,
When the superconducting material 8 is slowly cooled, the crystal structure of the superconducting material 8 becomes orthorhombic, and the superconducting phenomenon is fully exhibited. Here, the base material heating temperature was set at 500 to 980°C because below 500°C, the bonding force and adhesion of the coating particles will be poor, the risk of cracking of the coating will increase, and the The amount of oxygen deficiency becomes excessive,
This is because it becomes difficult to obtain a predetermined crystal structure. Furthermore, if the substrate temperature exceeds 980° C., the solidification of the molten particles attached to the substrate will be delayed, the film shape will deteriorate, and problems such as solidification cracking and crystal structure (phase separation, etc.) will occur. 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 tend 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 plate-shaped base material 2 made of copper is set inside the heater 9.
While heating the base material 2 to 600°C using
is continuously supplied into the thermal spray nozzle 5, and a power of 15 Kw is supplied from the plasma power source 7 between the thermal spray nozzle 5 and the electrode 6 to generate a superelectric material powder consisting of Y _0.3 Ba _0.7 Cu ₁ O _3-y. (particle size 10 to 100μm) spray nozzle 5
and 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 made of Manufactured. Next, set the heating temperature of the base material 2 by the heater 9.
Another plate-shaped superconducting material was manufactured under the same conditions as in the above-mentioned example except that the temperature was changed to 800°C. A test piece (base material thickness: 2 mm, film thickness: 0.15 mm, width: 5 mm, length: 50 mm) was cut out from the superconducting material produced in this way, and it was heated in liquid nitrogen (77K).
The critical current density (Jc) was examined using a four-terminal resistance measurement method. In addition, the critical temperature (Tc) was similarly measured using the four-terminal resistance measurement method. The results are summarized in Table 1 in relation to the substrate heating temperature. When the substrate was not heated (substrate temperature: equivalent to room temperature), no superconducting phenomenon was observed at liquid nitrogen temperature (77K). This is thought to be due to the bonding and adhesion between film particles and the presence of microcracks in the film.

[Table] As is clear from Table 1, according to the method of the present invention, the crystal structure and oxygen content of the coating 3 are controlled by heating the base material, so that when the value of (Jc) remains as sprayed, It was found that it was significantly larger. X
The line diffraction results confirmed that the crystal structure of the film was orthorhombic. Next, the strength of the film 3 was examined. this is,
As shown in Figure 2, a test piece of superconducting material (standard thickness: 2 mm, film thickness: 0.15 mm, width: 5 mm, length 50
mm) was subjected to a three-point bending test, and evaluated based on the bending angle of the test piece when cracking occurred in the coating 3. The results are shown in Table 2 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 heating the base material, the particles of the superconducting material become stronger, improving the density, and suppressing microcracks in the film, which increases the value of (Jc) and Increasing the strength of the coating has several very beneficial effects.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing how a film made of superconducting material is formed on the surface of a base material by the method of the present invention, and Figure 2 is a front view showing the three-point bending test method. It is. 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.

Claims (1)

[Claims] 1. While heating the base material to a temperature of 500 ° C. to 980 ° C., a film of a composite oxide superconducting material containing Cu _x O _y groups is formed on the surface of the base material, and thus obtained, A superconductor, characterized in that a superconducting material consisting of the base material and the film heated to the temperature is cooled at a cooling rate of 20°C/min or less, thereby imparting predetermined superconducting properties to the film. Method of manufacturing wood.