JPH0559861B2 - - 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 Conventionally, in order to produce a superconducting material made of Y-Ba-Cu-O system, a mixture of Y ₂ O ₃ , CuO and BaCO ₃ powders in a desired ratio is first fired, and then pulverized to a predetermined particle size. A powdered superconducting raw material was prepared, and this raw material was molded into a desired shape and then subjected to secondary firing. [Problems to be solved by the invention] However, in the conventional method described above, the superconducting material obtained is not dense, that is, the porosity is large and the bonding force between particles is weak, so the critical current density (Jc )
was small and had low strength. An object of the present invention is to provide a method for manufacturing a superconducting material that is dense and has high strength. [Means for solving the problem] This invention covers the surface of a powdery raw material of a composite oxide superconducting material containing a CuxOy group with Cu,
Next, the powdery raw material is heated to form a film made of CuO on the surface of the powdery raw material, and then the powdery mixed raw material thus obtained is formed into a desired shape and fired, or The method is characterized in that the sintered particles and the coating particles are firmly bonded to each other by thermally spraying the powdery mixed raw material onto the surface of the base material to form a coating. Next, the method of manufacturing a superconducting material by the liquid phase sintering method of the present invention will be explained in more detail. This invention first provides Y ₂ O ₃ , BaCO ₃ and CuO
A mixture of powders in a predetermined ratio is first fired, and then pulverized to a predetermined particle size to prepare a powdered superconducting raw material made of Y--Ba--Cu--O. Next, a Cu film is formed on the surface of the raw material by electroless plating. Thereafter, the raw material is heated to oxidize Cu. As a result, a film made of CuO is formed on the surface of the raw material. The powdered superconducting raw material thus obtained is molded into a desired shape or sprayed onto the surface of a base material, and then fired. As a result, CuO forms a eutectic with Y--Ba--Cu--O, melts, and sinters through the liquid phase. Therefore,
Superconducting particles are strongly bonded to each other. The reason why a CuO film is formed on the surface of the powdered superconducting raw material is that if CuO powder is mechanically mixed into the raw material, it will not mix uniformly and the effect of adding CuO will not be fully realized. It is. Next, embodiments of the invention will be described. Example 1 Y ₂ O ₃ , BaCO ₃ , and CuO powder at 0.5:2:
3 (molar ratio), and heated and baked at 950°C for 10 hours.
By crushing the superconducting raw material consisting of YBa ₂ Cu ₃ O ₇ ,
A powdered superconducting raw material having a particle size of 5 μm was prepared from Next, a Cu film having a thickness of about 0.1 μm was formed on the surface of the powdered superconducting raw material thus obtained by electroless plating. After this,
The powdered superconducting material on which the Cu film was formed was heated to 600°C for 30 minutes to oxidize the Cu. and,
The powdered superconducting raw material on which the CuO film was formed in this way was pressed and formed into a plate shape at 150 kg/cm ² and sintered by heating at a temperature of 980° C. for 10 hours in the air. The critical current density (Jc) and bending strength of the plate-shaped superconducting material produced in this manner were investigated. The results are shown in Table 1 together with a comparative material in which CuO powder was mechanically mixed without forming a CuO film on the surface of the powdered superconducting raw material.

[Table] As is clear from Table 1, the material of the present invention is superior to the comparative material in both (Jc) and strength. Example 2 Powdered superconducting raw material on which a CuO film similar to that used in Example 1 was formed was coated onto a copper substrate (plate thickness: 2
mm) onto the surface. 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 substrate 2 is placed in a vacuum container 4 facing a thermal spray nozzle 5.
is installed, the pressure inside the vacuum vessel 4 is reduced, and the thermal spray nozzle 5 is
A gas such as argon or helium and a powdered superconducting raw material are each continuously supplied into the chamber, and the power source 7 is activated to generate a plasma arc between the thermal spray nozzle 5 and the electrode 6. A superconducting film 3 having a thickness of 0.3 mm is formed on the surface of the substrate 2 by the thermal spraying device 1, and a superconducting material 8 is formed on the surface of the substrate 2.
was prepared. Next, the superconducting material 8 was heated to 900°C in the atmosphere.
The coating 3 was sintered by heating at a temperature of .degree. C. for 1 hour. The (Jc) and strength of the superconducting material made of the substrate 2 and the superconducting film 3 produced in this manner were investigated. As shown in FIG. 2, the strength was evaluated by subjecting the superconducting material to a three-point bending test and determining the bending angle of the substrate 2 when the film 3 cracked. These results are shown in Table 2 together with the results of a comparative material in which CuO powder was mechanically mixed without forming a CuO film on the surface of the powdered superconducting raw material.

〔Effect of the invention〕

As explained above, according to the present invention, by forming a CuO film on the surface of the powdered superconducting raw material in advance, the pores between the superconducting particles are reduced and the superconducting particles are firmly bonded to each other. Useful effects such as increased critical current density (Jc) and high strength are brought about. These effects do not form a CuO film on the surface of the powdered superconducting raw material, and the CuO
This is more noticeable than when powder is mixed with the raw materials.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a state in which powdered superconducting raw material is thermally sprayed onto the surface of a substrate, and FIG. 2 is a front view showing a three-point bending test method. In the drawings, 1... plasma spraying device, 2... base material, 3...
Film, 4... Vacuum container, 5... Thermal spray nozzle, 6...
...Electrode, 7...Plasma power supply, 8...Superconducting material.

Claims (1)

[Claims] 1. The surface of a powdery raw material of a composite oxide superconducting material containing a CuxOy group is coated with Cu, then the powdery raw material is heated to form a film made of CuO on the surface of the powdery raw material, and then, The powdery mixed raw material obtained in this way is molded into a desired shape and fired, or the powdery mixed raw material is thermally sprayed onto the surface of the base material to form a film. A method for producing a superconducting material, characterized by strongly bonding cohesive particles and film particles to each other.