JPH04179006A - Manufacture of ceramic superconductive wire materials - Google Patents

Abstract

PURPOSE:To obtain a ceramic superconductive wire material of better superconductivity characteristics and capable of preventing the formation of coarse voids by using as raw materials the stuff in which the metal particles of the same kind of materials as that of a metal pipe are dispersed. CONSTITUTION:The stuff containing the dispersed metal particles 2 of the same kind of materials as that of a metal pipe 1 is used for raw materials 3. Namely, when the metal particles 2 of the same kind of material as the composite materials are dispersed in the raw materials 3 for a ceramic superconductive conductor, the gas generated from the raw materials 3 is adsorbed by the surface of the metal particles to be minutely distributed. Accordingly, it is prevented that the generated gas coheres to be coarse. Thereby, the formation of coarse voids inside the ceramic superconductive layer is prevented, so that the superconductivity characteristics may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic superconducting wire with excellent electrical properties suitable for use in magnets, cables, current leads, and the like.

[Prior art] In recent years, B1-5r-Ca-Cu-0 system, Y-Ba-Cu-
0 system, Tl1-Ba-Ca-Cu-0 system, etc. critical temperature (
Ceramic superconductors whose Tc) exceeds the temperature of liquid nitrogen have been discovered, and applied research is underway in various fields.

By the way, since these ceramic superconductors are brittle, in order to process them into ceramic superconducting wire bodies of a predetermined shape, for example, raw material that can be made into a ceramic superconductor must be made into a powder compact of a predetermined shape, or a metal A composite billet filled with the raw material in a pipe is stretched to form a composite linear body of a predetermined shape, and then subjected to a predetermined heat treatment to transform the raw material into a ceramic super i! A method of forming a conductor is used.

Among the above-mentioned processing methods, the method of processing in combination with a metal pipe is suitable for manufacturing long materials, and research on its practical application is widely underway.

The metal pipe has the function of improving the workability of the internal raw material layer and imparting mechanical strength and electrical stability to the obtained ceramic superconducting wire. Metal pipe materials include Ag, Ag alloy, and C, which have excellent workability and thermal and electrical conductivity.
U, Cu alloy, etc. are used.

Conventional processing methods such as extrusion, rolling, drawing, and swaging may be used to stretch the composite billet. Furthermore, the cross-sectional shape of the composite linear body obtained by stretching the composite billet is circular.

Any shape such as ellipse, polygon, tape shape, etc. can be used.

Alternatively, a plurality of the above-mentioned composite wire bodies may be bundled, inserted into a metal pipe again, and stretched to form a multicore composite wire body, or the ceramic superconductor and the metal material may be alternately spirally shaped. Alternatively, it is also possible to form a concentric shape and subject it to elongation to form a multilayered or multicore composite linear body.

The heat treatment for converting the above-mentioned raw material into a ceramic superconductor is, for example, 900 to 950°C in the case of a Y-based ceramic superconductor and 850 to 900°C in the case of a 1B1-based ceramic superconductor. The reaction is carried out at a temperature in an oxygen-containing atmosphere to react the raw material into a ceramic superconductor.

[Problem to be solved by the invention]

However, when the above-described heat treatment is applied to the composite filament after the drawing process, a large amount of gas is generated from the raw material, and this gas coagulates, resulting in the resultant product shown in Figure 2. Coarse voids 7 are formed in the ceramic superconductor layer 6 of the ceramic superconductor, and as a result, the space factor of the ceramic superconductor layer at the void formation site becomes extremely small, reducing the mechanical strength of the wire. In addition, there is a problem in that the superconducting current is rate-limited by the small cross-sectional area portion, resulting in a significant decrease in the critical current value.

[Means to solve problems]

As a result of intensive research in view of the above situation, the present invention has found that if metal particles of the same grade as that used for the composite material are dispersed in a raw material material that can be made into a ceramic superconductor, It was discovered that the gas generated from the metal particles is adsorbed on the surface of the metal particles and distributed finely, and through further research, the present invention was completed.

That is, the present invention involves filling a metal pipe with a raw material that can be made into a ceramic superconductor to form a composite billet,
Next, in the method for manufacturing a ceramic superconducting wire, the composite billet is stretched to form a composite linear body, and then the composite linear body is subjected to a predetermined heat treatment. This method is characterized by the use of metal particles dispersed therein.

That is, the method of the present invention involves dispersing metal particles of the same grade as that used in the composite material into a raw material (hereinafter abbreviated as raw material) that can be used as a ceramic superconductor to be filled into a metal pipe, and then heating the material. The gas generated during processing is adsorbed on the surface of the metal particles to prevent the generated gas from coagulating and becoming coarse, and the metal particles include metal pipes and other materials used for composites. Materials for the metal pipe and metal particles used in the method of the present invention are made by using metal materials of the same grade so that the metal particles and the metal pipe do not react with each other and deteriorate even if they come into contact during heat treatment. as,
Ag, Cu, or an alloy thereof is a preferable material because it has excellent thermal and electrical conductivity, and Ag or an alloy thereof is particularly preferable because it has a high oxygen solidification ability. Also Ag
Among the alloys, Ag-Au, Ag-Pd, Ag-
Rh.

Because Ag-Pt etc. are non-reactive with ceramic superconductors,
Particularly suitable.

As mentioned above, the metal particles mixed into the raw material are made of the same material as the metal pipe used to form the outermost coating layer, but the same material does not mean the same material here. , not only metals of the same composition, but also Ag and Ag alloys or Cu
It may be a combination of Cu alloy and Cu alloy, and refers to a material that does not react with each other and change in quality even if the two come into contact at high temperature.

The method of the present invention will be specifically explained below with reference to the drawings. FIG. 1 is a process explanatory diagram showing an embodiment of the method of the present invention.

A metal pipe 1 for forming the outermost peripheral coating layer is filled with a raw material 3 in which metal particles 2 of the same type as the metal pipe 1 are dispersed to form a composite billet 4 (Figure A), Next, this composite billet 4 is stretched to form a tape-shaped composite linear body 5 (Fig. It causes a reaction.

As shown in Figure 1, if the metal particles 2 mixed with the raw material are too large, they will come into contact with the metal pipe in the composite filament after drawing, reducing the contact area with the raw material 3. Therefore, the diameter of the metal particles 2 depends on the workability of the metal particle material used, but the diameter is less than 0.
A thickness of about 5 to 0.03 mm is preferable.

The mixing ratio of the metal particles with the raw material is 5% (volume %).
), the amount of gas that can be adsorbed by metal particles is small;
If it exceeds 0%, the space factor of the ceramic superconductor layer decreases and the critical current decreases, so it is preferably in the range of 5 to 30%.

As a method for mixing the metal particles with the raw material, a conventional mixer, ball mill, or the like is used. Further, the shape of the metal particles is not particularly limited, and the size thereof may be mixed.

In addition, as a method of filling a metal pipe with a raw material in which metal particles are dispersed, it is possible to fill the metal pipe with powdered material, or to insert and fill a material that has been preformed by CIP or sintering. good.

The raw materials used in the method of the present invention include the above-mentioned Bi-based materials,
In addition to Y-based, Tf-based, and other ceramic superconductors, which are widely used, intermediates used in the synthesis of ceramic superconductors, which are precursors of the above-mentioned ceramic superconductors, such as oxides of constituent elements of ceramic superconductors, etc. Powders such as mixtures or coprecipitated mixtures of carbonates, oxygen-deficient composite oxides, or alloys of the above constituent elements can be used, and these precursors can be heated in an oxygen-containing atmosphere to form ceramic superconductors. It is something that reacts to.

[Function] In the method of the present invention, metal particles of the same grade as the metal pipe are dispersed in the raw material to be filled into the metal pipe, and gas generated from the raw material during heat treatment is adsorbed on the surface of the metal particles. Therefore, the generated gas does not aggregate and grow into coarse voids. Since the metal particles mentioned above are made of the same material as the metal pipe, even if they come into contact during heat treatment, they will not react with each other and deteriorate.

〔Example〕

The present invention will be explained in detail below using examples.

B 1zoff+ 5rCOs, CaCO3, CuO
The atomic ratio of Bi:Sr:Ca:Cu is 2=
After blending and mixing in a ratio of 2:1:2, it was heated in the air at 800°C for 20 hours and crushed to create a calcined powder with an average particle size of about 5 μm. Ag particles were mixed in various amounts, and the whole was thoroughly mixed using a mixer. The prepared mixture was filled into an Ag pipe to form a composite billet, and then this composite billet was sequentially rolled using grooved rolls and flat rolls to form a tape-shaped composite linear body. Next, each of the composite linear bodies thus produced was subjected to heat treatment at 850°C for 50 hours in the atmosphere to produce a tape-shaped ceramic superconducting wire.

The particle size and mixing amount of the Ag particles, and the shapes of the metal pipe and composite linear body were varied as shown in Table 1. For comparison, a similar tape-shaped ceramic superconducting wire was manufactured by the same method as in the example except that metal particles were not mixed into the raw material.

For each ceramic superconducting wire obtained in this way, void observation by SEM and critical current value (
Ic) was measured. The results are shown in Table 1. still,
Jc was measured in liquid nitrogen (77K) under zero magnetic field.

As is clear from Table 1, the products manufactured by the method of the present invention (floors 1 to 16)
) did not produce any coarse voids and had a high Tc value.

Among the products manufactured by the method of the present invention, Nn7 and 15 have large metal particles, and 8.16 has a small amount of metal particles mixed, so both have reduced gas adsorption ability. Since the amount of metal particles dispersed was large, the space factor of the ceramic superconductor layer was reduced, and the Ic was somewhat low in both cases.

On the other hand, since the comparative method products (Ntl17,18) were not mixed with metal particles, the gas generated from the raw materials aggregated and became coarse, forming coarse voids, resulting in a significant decrease in Ic.

In the above embodiment, the case of a Bi-based superconductor was explained, but the method of the present invention can also be applied to other ceramic superconductors to achieve similar effects. When the reaction is carried out by heating to , the effect of the final method becomes noticeable because a large amount of gas is generated from the raw materials.

〔effect〕

As described above, according to the method of the present invention, the gas generated during heat treatment is finely adsorbed on the surface of the metal particles, and the formation of coarse voids is prevented, so the ceramic superconducting wire has excellent superconducting properties. is obtained, and has a remarkable industrial effect.

[Brief explanation of drawings]

Figure 1A3 is a process explanatory diagram showing an embodiment of the method of the present invention;
FIG. 2 is a cross-sectional view of a tape-shaped ceramic superconducting wire produced by a conventional method. DESCRIPTION OF SYMBOLS 1... Metal vibrator, 2... Metal particles, 3... Raw material, 4... Composite billet, 5... Composite linear body,
6... Ceramic superconductor layer, 7... Coarse voids. Patent applicant Furukawa Electric Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A metal pipe is filled with a raw material that can be made into a ceramic superconductor to form a composite billet, and then the composite billet is stretched to form a composite linear body, and then the composite linear body is heated to a predetermined temperature. A method for producing a ceramic superconducting wire that is subjected to a treatment, the method comprising using a raw material in which metal particles of the same grade as a metal pipe are dispersed.