JPH04171612A - Manufacture of ceramic superconductive body - Google Patents

Abstract

PURPOSE:To improve superconductive characteristics by filling a raw material to become a ceramic superconductive body in an interpipe space part for making complex billet, applying extention work thereto for forming a complex wire body having a hollow part, and applying heat treatment to the complex wire body. CONSTITUTION:In side a raw material layer 4 being turned into a ceramic superconductive body filled in a metal pipe 1, a metal pipe 3 having an air permeation property at its wall surface are arranged at a required interval to form complex billet 5, and an extension work is applied thereto with a specified range of surface reduction ratio for remaining the metal pipe as a hollow part to form a complex wire body 7. Thereafter, heat treatment is applied to this complex wire body, whereby gas generated from a raw material 4 at the time of heat treatment passes through the pipe 3 to the hollow part. With the constitution, there is no fear that an outermost metal pipe 1 doesnot swell up. It is thus possible to have a ceramic superconductive body excellent in its shape and superconductive characteristics.

Description

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

[Conventional technology]

In recent years, B1-3r-Ca-Cu-0 series, Y-Ba-Cu-
0 system, Tl-Ba-Ca-Cu-0 system, etc.
A ceramic superconductor whose temperature (c) exceeds the temperature of liquid nitrogen has been discovered, and applied research is progressing 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 method is used in which a composite billet filled with the raw material 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 form the raw material material into a ceramic superconductor. It is being

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 superconductor. - 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 applied.

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.

Therefore, the heat treatment to make the raw material material into a ceramic superconductor, which is applied to the composite linear body as described above, is performed by, for example,
900-950'C for Y-based ceramic superconductor
, 850 to 900 for Bi-based ceramic superconductors
The process is carried out at a temperature of about °C in an oxygen-containing atmosphere to react the raw material to the ceramic superconductor.

[Problem to be solved by the invention]

However, when the above-described heat treatment is applied to the composite linear body, gas is generated from the raw material, and this gas is prevented from being released to the outside by the metal coating layer, and as a result, the sixth
As shown in the figure, a cavity 1 is formed between the ceramic superconductor layer 8 and the metal coating layer 9 of the obtained ceramic superconductor.
There was a problem in that 0 was formed, causing the ceramic superconductor to have a defective shape, and furthermore, the superconducting properties were significantly deteriorated.

[Means to solve problems]

The present invention has been made as a result of intensive research in view of the above situation, and its purpose is to provide a method for manufacturing a ceramic superconductor having excellent superconducting properties, free of bulges, good shape, etc. There is a particular thing.

That is, the present invention arranges a desired number of metal pipes with air permeability on their walls at intervals within a metal pipe, and fills the gaps between the pipes with raw material that can be made into a ceramic superconductor. The method is characterized in that the composite billet is filled with a substance to form a composite billet, the composite billet is then stretched to form a composite linear body having a hollow portion, and then the composite linear body is subjected to a predetermined heat treatment. It is something.

That is, in the method of the present invention, a desired number of metal pipes are arranged at intervals within a metal pipe, for example, metal pipes are made with a number of small holes in the wall surface to provide ventilation, and the metal pipes are arranged concentrically. When heating a composite linear body obtained by filling a gap between metal pipes with a raw material that can be made into a ceramic superconductor and subjecting it to drawing processing, the gas generated from the raw material is It is designed so that it can be released outward through a small hole in the wall of a metal pipe.

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.

Inside the metal pipe 1 for forming the outermost peripheral coating layer, a breathable metal pipe 3 with a small hole 2 in the wall surface is arranged concentrically (Fig. A), and then in the gap between the two pipes. A composite billet 5 is filled with a raw material material 4 that can be made into a ceramic superconductor (see Figure 5), and then this composite billet 5 is stretched to form a composite linear body 7 having a hollow portion 6. ), and then the composite linear body is subjected to a predetermined heat treatment to cause the raw material to react with the ceramic superconductor.

In the method of the present invention, the permeable metal pipe 3 has a small hole 2 formed in the wall surface of the metal pipe of any shape such as rectangular, circular, hexagonal, etc. as shown in Fig. 2 A to C. applies. In addition, if the hole diameter for providing the above-mentioned air permeability is too small, gas will not be able to escape sufficiently, and if it is too large, the molten raw material will leak out during heat treatment, so the hole diameter should be 0.1~
It is preferable to set the diameter to about 1 mmφ. Further, if the space factor of the small holes formed in the pipe wall surface is less than 5%, sufficient gas release will not be achieved, and if it exceeds 40%, the strength of the breathable metal pipe will decrease, so it is preferably in the range of 5 to 40%.

In the method of the present invention, depending on the shape of the metal pipe used, the shape of the composite billet to be formed may be a metal pipe 1 having a rectangular, circular, or hexagonal cross section as shown in FIG. A material in which a raw material material 4 that can be made into a ceramic superconductor is arranged between a permeable metal pipe 3, or a fourth material
As shown in the figure, a plurality of air permeable metal pipes 3 are arranged in parallel to improve degassing performance, or as shown in Fig. There is a structure in which a plurality of metal pipes 3 are arranged concentrically at increased intervals, and the gap between each breathable metal pipe is filled with a raw material 4 that can be made into a ceramic superconductor to increase the strength. . Therefore, the above-mentioned raw material can be filled either by filling the raw material such as powder as is, or by filling the raw material such as powder with C.
IP molding Acid formed sintered molded material may be inserted and filled.

Further, the metal pipe and the permeable metal pipe do not necessarily have to have similar shapes.

As the breathable metal pipe used in the method of the present invention, in addition to the above-mentioned metal pipe with many small holes in the wall surface, it is also possible to use a pipe made of fine mesh or net. .

In the method of the present invention, the stretching process applied to the composite billet is
It is necessary to reduce the area by such a degree that a hollow portion remains in the composite linear body obtained after drawing. Further, any conventional processing method as described above may be applied to the stretching process.

As the material for the metal pipe or breathable metal pipe used in the method of the present invention, fi, gXCu, or an alloy thereof is preferable because it has excellent thermal and electrical conductivity, but Ag or an alloy thereof is particularly preferable. It is preferable because it has excellent oxygen permeability. Also, in Ag alloys, Ag-Au, A
g-Pd, Ag-Rh, Ag-Pt, etc. are particularly suitable because they are non-reactive with ceramic superconductors.

The raw materials that can be used as ceramic superconductors used in the method of the present invention include the aforementioned Bl-based and Y-based materials.

In addition to the wide application of Tl-based ceramic superconductors, intermediates used in the synthesis of ceramic superconductors, which are precursors of the above-mentioned ceramic superconductors, such as oxides and carbonates of ceramic superconductor constituent elements, etc. Powders such as mixtures or coprecipitation mixtures, oxygen-deficient composite oxides, or alloys of the above constituent elements can be used, and these precursors react with the ceramic superconductor by heat treatment in an oxygen-containing atmosphere. It is.

[Effect]

In the method of the present invention, a desired number of metal pipes having air permeability on the wall surface are arranged at predetermined intervals inside a layer of raw material that can be made into a ceramic superconductor filled in a metal pipe to form a composite billet. Then, this composite billet is stretched to form a composite linear body at a reduction in area within a range in which the above-mentioned air permeable metal pipe remains as a hollow portion, and then this composite linear body is subjected to a prescribed heat treatment. Therefore, the gas generated from the raw material during the heat treatment passes through the permeable metal pipe and exits into the hollow part. Therefore, the outermost layer of the metal pipe does not bulge, and a ceramic superconductor having excellent shape and superconducting properties can be obtained. Furthermore, since a metal pipe without small holes is used on the outermost periphery of the composite billet 1-, the resulting ceramic superconductor has an excellent appearance.

〔Example〕

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

Example I B 1z03. SrCO3, CaCC)+, CuO powder with an atomic ratio of Bi:Sr:Ca:Cu of 2:2.
: After mixing in a ratio of 1:2,
Heated at 00°C for 20 hours, pulverized this to create a calcined powder, and processed this calcined powder into a powder with an external dimension of 8 by CrP method.
It was molded into a rectangular pipe with dimensions of 4 mm x 4 mm and internal dimensions of 6 mm x 2 mm. Next, a pipe-shaped molded body of the above-mentioned pre-sintered powder was formed to have an external dimension of 10 mm x 6 +n+n.

It was inserted into an Ag pipe with internal dimensions of 8.1 mm x 4.1 mm, and a wall surface with external dimensions of 5.9 mm x 1.9 mm and internal dimensions of 5 mm x 1 mm was inserted into the pipe-shaped molded body of the pre-sintered powder. A composite billet was created by inserting a breathable metal pipe made of Ag with many small holes at equal intervals. Thereafter, the composite billet was rolled to form a hollow tape-shaped composite linear body with a width of 15 mm and a thickness of 3 m+n.

Example 2 The calcined powder produced in Example 1 was heated to an outer diameter of 7.5 mm by CIP method.
It was molded into a circular pipe with a diameter of 9 mm and an inner diameter of 6.0 mm. Next, a molded body of the above pre-fired powder was formed into an outer diameter of 10 mm.

It was inserted into an Ag pipe with an inner diameter of 8.0 mm, and further into the pipe-shaped molded body of the pre-sintered powder, an outer diameter of 5.9 mm and an inner diameter of 4 mm was inserted.
A composite billet was prepared by inserting a breathable metal pipe made of Ag with a large number of small holes equally spaced into the wall. Thereafter, the composite billet was subjected to swaging and drawing to form a hollow composite linear body with a diameter of 6.5 gates.

Example 3 A large number of small holes were made at equal intervals in a metal tube with an outer diameter of 10 mm and an inner diameter of 8.5 mm.The outer and inner diameters were 8.0, 7.5, 6.5, and 6.0.5, respectively. Three breathable metal pipes of 0 and 4.5 mm were arranged concentrically, and then the gap between each pipe was filled with the same calcined powder as used in Example 1 to form a composite billet. Thereafter, this was subjected to drawing processing to form a hollow composite linear body with a diameter of 5 mm.

In Examples 1 to 3 above, the diameter and space factor of the small hole drilled in the breathable metal pipe were varied as shown in Table 1.

Comparative Example 1 Example 1 was repeated except that an Ag pipe without a small hole was inserted into the pipe-shaped molded body of the calcined powder.
A hollow composite linear body was manufactured using the same method as described above.

Comparative Example 2 The same calcined powder used in Example 1 was formed into a square bar with external dimensions of 8 mm x 4 mm by the CIP method, and this square bar was shaped into a square bar with external dimensions of 10 mm x 6 mm and internal dimensions of 8.1 mm.
After inserting it into a Ag pipe measuring 4.1 mm x 4.1 mm to form a composite billet, the composite billet was rolled to produce a hollow tape-shaped composite linear body with a width of 15 m+n and a thickness of 3 mm.

Comparative Example 3 The same procedure as Example 2 was performed except that an Ag pipe without a small hole was inserted into the pipe-shaped molded body of the calcined powder.
A composite linear body was manufactured by the same method as above.

Comparative Example 4 The calcined powder produced in Example 1 was processed by the CTP method to have an outer diameter of 7.
The round bar molded body was formed into a 9 mm round bar, and the outside diameter was 0.
The same method as in Example 2 was used except that the billet was inserted into an Ag vibrator with an inner diameter of 8.0 mm and a composite billet.
．． A solid composite linear body having a diameter of 5 mm was manufactured.

Comparative Example 5 In Example 3, all three breathable metal pipes were
Example 3 except that the pipe was replaced with an Ag pipe without small holes.
A hollow composite linear body having a diameter of 6 mm was manufactured by the same method as described above.

Comparative example 6 In Example 3, the calcined powder had an outer diameter of 10.0 mm.

A solid composite linear body with a diameter of 6 mm was manufactured in the same manner as in Example 3, except that it was inserted into an Ag pipe with an inner diameter of 8.5 mm to form a composite billet.

Each of the composite linear bodies thus obtained was subjected to a heat treatment of 850''C x 50 hours in the atmosphere to form a ceramic superconductor.

The shape of the obtained ceramic superconductor was investigated and the critical current density (Jc) was measured. The results are shown in Table 1.

Note that Jc was measured in liquid nitrogen (77K) under zero magnetic field.

Table 1 * Value obtained by dividing Tc by the average cross-sectional area I 5 As is clear from Table 1, the product manufactured by the method of the present invention (N).

1 to 21) have almost no cavities and almost good shape,
Jc was also high.

Among the method products of the present invention, No. 6-7.14-1
520, the hole diameter of the ventilation pipe or the traffic area ratio is too large, and the ceramic superconductor inside leaks out, or the inner layer of the ventilation metal pipe does not have the strength and the hollow part becomes clogged. , the density of the ceramic superconductor layer decreased, and No. 8, No. 16.21 had a too low turnout rate and did not allow enough gas to escape, causing slight swelling, so Jc was somewhat low in all cases. The value was .

On the other hand, in the comparison method products (No. 22 to 27), the generated gas did not escape at all, so blistering occurred frequently and Jc decreased significantly.

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

〔effect〕

As described above, according to the method of the present invention, a ceramic superconducting body having a good shape and excellent superconducting properties can be easily manufactured, and a remarkable effect is produced industrially.

[Brief explanation of the drawing]

FIGS. 1A to 1C are process explanatory diagrams showing embodiments of the method of the present invention,
Figures 2A to 2C are perspective views showing embodiments of the permeable metal pipe used in the method of the present invention, and Figures 3.4.5 are sectional views showing embodiments of the composite billet used in the method of the invention. , FIG. 6 is a cross-sectional view of a conventional ceramic superconductor. Engineering...metal pipe, 2...small hole, 3...breathable metal pipe, 4...raw material that can be made into a ceramic superconductor, death...composite billet, 6...hollow part, 7・
... Composite linear body, 8 ... Ceramic superconductor layer, 9
...Metal coating layer, 10...Cavity.

Claims (1)

[Claims] A desired number of metal pipes with permeable walls are arranged at intervals within the metal pipe, and the gaps between the pipes are filled with a raw material that can be used as a ceramic superconductor to form a composite. Production of a ceramic superconductor, characterized in that the composite billet is made into a billet, the composite billet is then subjected to elongation processing to form a composite linear body having a hollow portion, and then the composite linear body is subjected to a predetermined heat treatment. Method.