JPH04174913A - Manufacture of ceramic superconductor - Google Patents

Abstract

PURPOSE:To improve superconductive characteristic by boring small holes on a metal sheet or a pipe used when molding a composite sheet for air permeability. CONSTITUTION:A raw material layer 3 is formed on a metal sheet 2 bored with small holes for air permeability to obtain a composite sheet 4, the sheet 4 is spirally wound on a metal pipe 5 bored with small holes 1 while the layer 3 is faced to the inside to obtain a spirally wound body 6, the wound body 6 is filled in a metal pipe 8 to obtain a composite billet 9, it is drawn to obtain a composite linear body, and it is heat-treated. A ceramic superconductor which has a good shape and excellent superconductive characteristic and is adaptable to large-capacity excitation in particular is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a hollow ceramic nex superconductor that is passed through a large-capacity current 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, 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, these ceramic superconductors are brittle, so in order to process them into ceramic superconducting wire bodies of a predetermined shape, raw material that can be used as a ceramic superconductor is filled into a metal pipe to form a composite billet, and then A method is used in which this composite billet is stretched to form a composite filament of a predetermined shape, and then subjected to a predetermined heat treatment to cause the raw material to react with a ceramic superconductor.

However, since ceramic superconductors have the disadvantage of being inferior in mechanical strength and thermal/electrical conductivity, especially when forming a thick ceramic superconductor layer, a metal sheet is placed inside the superconductor layer in a spiral or The above drawbacks are compensated for by combining them in a concentric cylindrical shape.

In this way, the metal pipes and metal sheets that are combined with ceramic superconductors are made of ceramic.

The material serves to improve the workability of the raw material layer that can be made into a ceramic superconductor, and also to impart mechanical strength and electrical stability to the obtained ceramic superconductor, and the metal Ag, which has excellent workability and thermal and electrical conductivity, is used as a material for manufactured pipes and metal sheets.
Alloys, Cu, Cu alloys, etc. are used.

Further, as a method for stretching the composite billet, conventional processing methods such as extrusion, rolling, drawing, and swaging can be applied. 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.

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
It is applied in an atmosphere containing oxygen at a temperature of about 1000 yds., and the raw material reacts to form a ceramic superconductor.

[Problems to be Solved by the Invention] However, when the heat treatment temperature applied to the composite linear body is high, especially when the heat treatment is performed at a temperature higher than the half-melting temperature of the raw material, a large amount of gas is generated from the raw material. This gas is prevented from being released to the outside by the aforementioned metal sheet or metal pipe, and as a result, the ceramic superconductor layer 12 and metal coating I of the ceramic superconductor obtained as shown in FIG. ! There is a problem in that a cavity 14 is formed between the ceramic superconductor 13 and the ceramic superconductor, which causes a defect in the shape of the ceramic superconductor and further causes a significant deterioration of the superconducting properties.

[Means to solve problems]

The present invention was made as a result of intensive research in view of the above situation, and its purpose is to create a ceramic superconductor that is free from bulges, has a good shape, has excellent superconducting properties, and is especially suitable for large-capacity current flow. The purpose of this invention is to provide a method for manufacturing various types of bodies.

That is, the present invention forms a composite sheet by forming a layer of a raw material that can be used as a Cerami-Nox superconductor on a metal notebook provided with air permeability, and then placing the composite sheet with the raw material layer on the inside. , the spirally wound body or concentric cylindrical body is formed into a spirally wound body on a metal pipe whose wall surface is provided with air permeability, and then the spirally wound body or concentric cylindrical body is placed inside the metal pipe. The composite billet is filled to form a composite billet, and then the composite billet is stretched to form a composite linear body having a desired shape having a hollow portion, and then the composite linear body is subjected to a predetermined heat treatment. It is something to do.

That is, the method of the present invention involves forming a composite sheet by forming a layer of raw material that can be made into a ceramic superconductor (hereinafter abbreviated as "raw materials") on a metal sheet, and spirally forming the composite sheet. For example, a metal sheet or metal pipe that is used as a core when rolled up or formed into a concentric cylindrical shape is made with many small holes to provide ventilation, and the gas generated during heat treatment is passed through the small holes. It is designed so that it can be released to the outside through.

The method of the present invention will be specifically explained below with reference to the country. FIGS. 1 to 1 are process explanatory diagrams showing embodiments of the method of the present invention.

A raw material layer 3 is formed on a metal sheet (hereinafter abbreviated as breathable metal sheet) 2 (Figure A) which has been provided with small holes 1 to provide air permeability (apertures are formed into a composite sheet 4), and then this composite sheet is formed. 4, with the raw material layer 3 inside, make a small hole 1 in the wall surface.
A spirally wound body 6 is formed by winding the composite sheet 4 in a spiral shape on a metal pipe (hereinafter abbreviated as a permeable metal pipe) 5 which has been provided with air permeability (Fig. C), or the composite sheet 4 has different diameters. Molded into a cylindrical shape, each cylindrical body is connected to a breathable metal pipe 5.
The spirally wound body 6 or the concentric cylindrical body 7 is then filled into a metal pipe 8 to form a composite billet 9. Kuzuho, he),
Next, the composite wire 9 is subjected to elongation processing to form a composite linear body 11.21 having a hollow portion lo in its cross section.
h) After that, the composite linear body 11.21 is subjected to a predetermined heat treatment to form a ceramic superconductor.

The permeable metal pipe used in the method of the present invention includes
A breathable metal pipe 5 with a small hole 1 drilled in the wall of a metal pipe of any shape such as rectangular, circular, hexagonal, etc. as shown in C.
applies. Also, if the diameter of the small hole drilled in the breathable metal pipe or breathable metal sheet 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 diameter of the small hole should be about 0.1 to 111 mφ. It is preferable to set the size to . In addition, if the space factor of the small holes drilled in the wall of the metal sheet or metal pipe is less than 5%, sufficient gas release will not be achieved, and if it exceeds 40%, the strength of the breathable pipe will decrease, so it should be in the range of 5 to 40%. is preferred.

In the method of the present invention, the shape of the composite billet to be formed is as follows:
As shown in FIG.
Air permeable metal pipes 5 of similar shapes are arranged concentrically at intervals, and are arranged in a composite structure.

Note that the outermost metal pipe and the innermost permeable metal pipe do not necessarily have to be similar in shape.

The raw materials used in the method of the present invention include the above-mentioned Bl-based materials,
In addition to the wide application of ceramic superconductors such as Y series and 71 series, intermediates used in the synthesis of ceramic superconductors, which are precursors of the above 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.

As a method for forming the above-mentioned raw materials on a breathable metal sheet, for example, a predetermined amount of the above-mentioned primary raw materials such as oxides and carbonates are blended and mixed, and this mixed powder is heat-treated. This calcined powder is kneaded with a binder to form a slurry, which is formed into a sheet by a doctor blade method to form a green sheet, and this green sheet is stacked on a breathable metal sheet. A method of lightly rolling this to make it stick together is commonly used.

Further, in the present invention, the composite sheet may be created by forming raw material layers on both sides of a breathable metal sheet. In addition, a composite sheet using a metal sheet without small holes is placed on the outermost layer, and it can be placed as is without filling the metal pipe.
It may also be used as a composite billet.

The breathable metal sheet or pipe used in the method of the present invention includes a metal sheet or metal pipe with many small holes as described above, as well as a sheet or pipe made of fine mesh or net. It is also possible to use a molded product.

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 can be applied to the stretching process.

Materials for the metal pipe, breathable metal sheet, or breathable metal pipe used in the method of the present invention include Ag, Cu,
Ag or an alloy thereof is a preferable material since it has excellent thermal and electrical conductivity, and Ag or an alloy thereof is particularly preferable because it has excellent oxygen permeability. Among Ag alloys, there is Ag-Au.

Ag-Pd, Ag-Rh, Ag-Pt, etc. are particularly allowed to pass through because they are non-reactive with ceramic superconductors.

[Effect]

In the method of the present invention, a raw material is formed in layers on a breathable metal sheet to form a composite sheet, and this composite sheet is rolled up in a spiral shape on a breathable metal pipe with the raw material layer inside, or in a concentric tube. This is formed into a spirally wound body or a concentric cylindrical body, which is then filled into a metal pipe to form a composite billet, and then this composite billet is stretched to form a composite having a hollow part. Since the linear body is heat-treated, the gas generated from the raw material during the heat treatment is extracted to the outside through the small holes and hollow portions of the breathable metal sheet and the breathable metal pipe. Therefore, a ceramic superconductor with excellent shape and superconducting properties can be obtained without causing any bulges in the outermost layer of the metal pipe. Furthermore, since a metal pipe without small holes is used for the outer periphery of the composite billet, the resulting ceramic superconductor has an excellent appearance.

〔Example〕

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

Example I BjzOz, 5rCO, CaCO3, CaO powder in an atomic ratio of Bi:Sr:Ca:Cu of 2=2:l
: After blending and mixing so that the ratio is 2, 800
'CX heated for 20 hours, pulverized to make a calcined powder, then kneaded with a binder to make a slurry,
This slurry was made into a thickness of 0.2m using the doctor blade method.
It was molded into a green sheet of m.

On the other hand, a breathable Ag sheet with a thickness of 0.2 ml1 was prepared with a large number of small holes made at regular intervals, and the above-mentioned green sheet was overlaid on this breathable Ag sheet and lightly rolled to make them adhere to each other. It is made into a composite notebook with a diameter of 0.4 mm, and this composite sheet is made with an outer diameter of 5 mm with many small holes made at equal intervals.
1/ A layer of raw material is placed on an Ag breathable pipe with an inner diameter of 4.5 mm and wound up into 10 layers to form a spirally wound body. Inner diameter 15mm
A composite fillet was prepared by filling the inside of the Ag pipe. Next, apply swaging to this composite fin and
A composite linear body having an outer diameter of 14 mm and having a hollow portion of mmφ was manufactured.

Example 2 The composite sheets produced in Example 1 were
Three cylindrical bodies with a diameter of 7.6 am were formed, and these cylindrical bodies were arranged concentrically on a breathable Ag pipe with an outer diameter of 5 mm and an inner diameter of 4.51 mm to form a concentric cylindrical body. The cylindrical body was filled into an Ag pipe having an outer diameter of 10 mm and an inner diameter of 81 mm to produce a composite fillet. Next, the composite billet was subjected to a swaging process to produce a composite linear body having an outer diameter of 61 and having a hollow portion of 3 mmφ.

In Examples 1 and 2, the diameter and space factor of the small holes formed in the breathable Ag sheet and the breathable Ag pipe were varied as shown in Table 1.

Comparative Example 1.2 Same as Example 1 or 2, respectively, except that an Ag sheet without small holes was used in place of the breathable Ag sheet used to prepare the composite sheet. A hollow composite linear body was manufactured by this method.

Comparative Example 3.4 In Example 1 or 2, an Ag sheet and an Ag pipe without small holes were used instead of the breathable Ag sheet and breathable Ag pipe used to produce the composite sheet, respectively. A hollow composite linear body was manufactured by the same method as in Example 1 or 2.

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 conductor was investigated and the critical current density (Jc) was measured. The result is the first
Shown in the table.

As is clear from Table 1, the product produced by the method of the present invention (N.

1 to 16), almost no swelling occurred and the shape was almost good,
It was a first shift job with a high Jc.

Among the method products of the present invention, No. 6-7.14-1
5 is that the hole diameter or hole space factor of the breathable Ag sheet and the breathable Ag pipe is too large, causing the internal Ceraminox superconductor to leak out, or the strength of the inner layer of the breathable Ag pipe to be insufficient. The hollow part may be deformed, and the density of the ceramic superconductor layer will decrease. Also, the small hole diameter and space factor of Nα8 and Nα16 are too small, so gas cannot escape sufficiently, causing a slight bulge. The value of Jc was also somewhat low.

On the other hand, for the comparison method product Nα17.18, most of the gas remained without escaping even though the gas from the raw material near the breathable Ag pipe escaped, and for Nci 19.20, no gas escaped at all. Blistering also occurred, and Jc decreased significantly.

In the above example, 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 a temperature of , there is a lot of gas generated from the original #J substance, so Honjo's effect becomes noticeable.

[Effects] As described above, according to the method of the present invention, the ceramic/
The DIS superconductor can be easily and eco-manufactured and has remarkable industrial effects.

[Brief explanation of the drawing]

Figures 1 to 1 are process explanations showing embodiments of the present invention;
Figures A to C are perspective views showing embodiments of a permeable pipe used in the present invention, and Figure 3 is a cross-sectional view of a conventional ceramic superconductor. ■...Small hole, 2...Breathable metal sheet, 3-layer raw material layer, 4...Composite sheet, End...Breathable metal pipe, 6...Spiral winding body, 7...Concentric Cylindrical body, 8... Metal pipe, 9... Composite billet,
1o...Hollow part, 11.21...Composite linear body,
12... Ceramic superconductor layer, I3... Metal coating layer, 14 River cavity. Patent applicant Furukawa Electric Co., Ltd. Figure 1 Figure 1

Claims (1)

[Claims] A composite sheet is formed by forming a layer of raw material that can be used as a ceramic superconductor on a metal sheet with air permeability, and then the composite sheet is placed on a metal pipe whose wall surface is made of air permeable material. With the layer on the inside, it is wound into a spiral shape or formed into a concentric cylindrical body, and then the spirally wound body or concentric cylindrical body is filled into a metal pipe to form a composite billet. A method for producing a ceramic superconductor, comprising: first subjecting the composite billet to elongation processing to form a composite linear body having a hollow portion, and then subjecting the composite linear body to a predetermined heat treatment.