JPH03154305A - Manufacture of superconducting coil - Google Patents

Abstract

PURPOSE:To eliminate cracks and improve mechanical strength by firing a green sheet obtained by sticking two ceramic raw sheets, extending it in the direction of axis, and then forming a thin film of an oxide superconductor on the surface. CONSTITUTION:A raw sheet 7b of a plate-shaped ceramic is placed on another raw sheet 7a of plate-shaped ceramic so that the upper surfaces and lower surfaces of both raw sheets of ceramic overlap each other and then they are applied to each other, thus forming a green sheet 8. Then, the green sheet 8 is wound around a core body while a die lubricating material is added to one surface and the firing is performed, thus producing a coil-shaped ceramic substrate 13 without any warpage and curving. This ceramic substrate 13 is oriented in the direction of axis and a thin film 20a of oxide superconductor is formed on the surface using a thin-film forming means, thus forming the homogeneous superconducting thin film 20a without any crazing and cracking.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a superconducting coil used in superconducting equipment such as magnets for nuclear magnetic resonance apparatuses, magnets for particle accelerators, superconducting magnetic levitation trains, and superconducting magnetic propulsion ships.

"Prior Art" In recent years, various oxide-based superconductors have been discovered that exhibit critical temperatures (Tc) higher than liquid nitrogen greenhouses.

These oxide superconductors include Y-BaCu-0 system, B1-8r-Ca-Cu-0 system, Tl-Ba-Ca
-Cu-0-based superconductors are known.

Conventionally, methods for producing these oxide superconductors include: (1) mixing and molding compound powder (mainly oxide powder) containing the constituent elements of the oxide superconductor, and then sintering the molded body; A method of molding and sintering a mixed powder obtained by a coprecipitation method, a method of forming a superconducting thin film on the surface of a plate-shaped substrate using a thin film forming method such as sputtering, vapor deposition, or CVD. Are known.

"Problem to be Solved by the Invention" However, the above-mentioned oxide superconductors generally have low strength and lack elasticity, so even if these oxide superconductors are made into wires and coils, the resulting superconducting coils are extremely difficult to obtain. It is extremely brittle, and a product strong enough to withstand practical use has not been obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an oxide-based superconducting coil with excellent mechanical strength.

"Means for Solving the Problem" In the invention described in claim 1, another raw ceramic sheet is placed on a plate-shaped raw ceramic sheet produced by a doctor blade method, and the upper surfaces of both raw ceramic sheets are The raw ceramic sheets are placed so that their bottom surfaces overlap each other, and the raw ceramic sheets are bonded together to form a green sheet. Next, a release material is attached to one side of the green sheet and it is wrapped around a core body, and then fired. to produce a coil-shaped ceramic substrate, and then, while stretching the ceramic substrate in the axial direction, a thin film of an oxide superconductor is formed on the surface using a thin film forming means to produce a superconducting coil. was taken as a means to solve the above problem.

Further, in the invention described in claim 2, another raw ceramic sheet is placed on the plate-shaped raw ceramic sheet produced by the doctor blade method so that the upper surfaces or lower surfaces of both raw ceramic sheets overlap. Then, using an adhesive containing a solvent of a different type from the binder contained in the green ceramic sheet, both green sheets are bonded together to form a green sheet, and then one side of the green sheet is separated. The shaped material is attached and wound around the core body, and then fired to form a fired sheet.The fired sheet is then divided from the bonded part to create two coiled ceramic substrates.Then, the ceramic substrate is The only means to solve the above problem is to manufacture a superconducting coil by forming a thin film of an oxide superconductor on the surface of the superconducting coil using a thin film forming means while stretching the superconducting coil in the axial direction.

Hereinafter, the method of the present invention will be explained in detail with reference to the drawings.

1 to 8 are diagrams for explaining an example of the method of the present invention.

In this example, first, a green sheet is produced from ceramic powder using a doctor blade method.

As the material for the ceramic substrate used in the method of the present invention, those having high toughness and plasticity are preferably used, and particularly preferred materials include 7. Yt to rot
03. Examples include partially stabilized zirconia (PSZ) in which a stabilizer such as MgO, CaO, and Ce0t is dissolved, and stabilized zirconia.

To produce a green sheet from this ceramic material, a solvent and chemicals necessary for producing a green sheet such as a plasticizer, a binder, and a dispersant are added and mixed with the ceramic powder.
A homogeneous slurry is made, and the obtained slurry is drawn out into a sheet using a doctor blade device, and then the solvent is volatilized and solidified by hot air drying to produce a green sheet.

FIG. 1 is a diagram showing an example of a doctor blade device suitably used for producing a green sheet. This device includes a supply port 2 for supplying a slip 1 in the form of a slurry containing a ceramic material, a belt 3 for conveying the slip 1 formed in a thin plate shape, and a belt 3 for conveying the slip 1 formed in a thin plate shape from the supply port 2 onto the belt 3. It comprises a doctor blade 4 for drawing out the slip 1, and a dryer 5 for heating and drying the thin plate-like slip 1 on the belt 3.

To produce a raw sheet using this doctor blade device, the slip 1 is put into the supply port 2, and the belt 3 is moved by rotating two rollers 6a and 6b for driving the belt 3. The slip l is pulled out in a thin plate form from the supply port 2 onto the belt 3 by a doctor blade 4,
It is conveyed by the belt 3 and enters the dryer 5, where it is heated and dried to become a rubber-like raw sheet 7a. The dried raw sheet 7a is separated from the belt 3 and wound around a winding roller.

The dimensions of the raw sheet produced in this way are limited in the width direction by the sheet forming width of the doctor blade device;
The length can be set to a certain arbitrary length. In addition, the thickness of the green sheet is set appropriately taking into consideration the mechanical strength after firing, but it is usually 10~2007z.
It is desirable to set it to about m. Also, this raw sheet is usually
It is cut to a predetermined width and length into a long tape.

Next, as shown in FIG. 2, another raw sheet 7b is placed on top of the produced long raw sheet 7a so that their upper surfaces or lower surfaces overlap, and then these raw sheets 7a, Paste 7b together and make green sheet 8
form.

As a method for bonding the two raw sheets 7a, 7b, a method of applying an adhesive between these raw sheets 7a, 7b to bond them together is preferably used.

In addition to the method described above, the two raw sheets 7a and 7b may be pasted together by stacking the two raw sheets 7a and 7b with their upper surfaces or lower surfaces stacked together as shown in FIG. After matching, a method of bonding by placing the sheets between a pair of pressure rollers 9 and pressing them together is also suitably used. Further, in this case, it may be preferable to perform pressure bonding while heating.

Next, as shown in FIG. 4, the green sheet 8 obtained by the above-described bonding is coated with a release material lO on one side.
It is wound around the cylindrical core body 11 in a coil shape while attaching it. This mold release material 10 is made of a material that does not exhibit adhesiveness or reactivity during firing with respect to the ceramic material used.
When using zirconia as a ceramic material, a sheet (or a powder) mainly composed of alumina powder or boron powder may be sprayed and sprinkled.

) is preferably used.

Next, the green sheet 8 wound around the core 11 is placed on the setter 12, and then the core 11 is gently removed. Next, this was placed in a firing furnace and heated at a temperature of about 1500°C.
Bake for several hours. By this firing, a coil-shaped ceramic substrate 13 shown in FIG. 5 is produced.

Next, the obtained ceramic substrate 13 is placed in a sputtering apparatus shown in FIG. 6, and while being stretched in the axial direction, a thin film of an oxide superconductor is formed on the surface of the ceramic substrate 13 to produce a superconducting coil. This sputtering apparatus includes a target 15 serving as a cathode and the ceramic substrate 1 in a vacuum chamber 14.
3 and a shutter 16 disposed between them, and an exhaust device and an Ar gas supply path 17 for evacuating the inside of the vacuum chamber 7<14. The top 8 target 15 is Y-Ba-C
A target made of an oxide superconductor such as a u-0 superconductor, a Bi-8r-Ca-Cu-0 superconductor, or a Tl-Ba-Ca-Cu-0 superconductor is used.

In this sputtering apparatus, a target 15 and a ceramic substrate 13 are placed in a vacuum chamber 14, and while being evacuated, Ar gas is introduced from an Ar gas supply path 17 to create a low-pressure Ar gas atmosphere in the vacuum chamber 14. 300 to 200 between the ceramic substrates 13
A voltage of 0 V is applied and sputtering is performed in a low-pressure Ar gas atmosphere.

In this figure, reference numeral 18 is an Ar ion, and 19 is a sputtered atom.

In addition, in this sputtering, the ceramic substrate 1
The ceramic substrate 13 is rotated gently so that a superconducting thin film is uniformly formed on the surface of the ceramic substrate 13. In addition, the ceramic substrate 1 is
It is preferable to heat 3 to several hundred degrees Celsius.

Through such sputtering, the ceramic substrate 1
A superconducting thin film is formed in a uniform state on three surfaces, and a superconducting coil is produced. Further, the film forming rate is several tens of people/second.

In this sputtering, in order to uniformly form a superconducting thin film on the surface of the coil-shaped ceramic substrate 13, the film is formed on the surface of the substrate while stretching the ceramic substrate 13 in the axial direction. FIG. 7 is for explaining an example of a method for forming a film on the ceramic substrate 13. In this example, a target layer 15 is disposed outside the ceramic substrate 13 formed in a coil shape, and the ceramic substrate 13 is A superconducting thin film 20a made of an oxide superconductor is formed on the outer surface of the ceramic substrate 13 by stretching a part of the ceramic substrate 13 and then rotating the substrate as shown by the arrow in the figure and sequentially winding it up on one side. Thus, a superconducting coil 21a is manufactured.

FIG. 8 is a diagram for explaining another example of the film forming method. In this example, the target 15 is arranged inside the ceramic substrate 13, and as in the previous example, the target 15 is placed inside the ceramic substrate 13. The superconducting thin film 20b is formed on the inside of the ceramic substrate 13 by stretching the part and winding it up to the other side.
A superconducting coil 21b is produced by forming a film. Forming the superconducting thin film 20b inside the ceramic substrate 13 in this manner is advantageous in terms of strength.

Furthermore, by performing the above sputtering in combination, it is also possible to form superconducting thin films on both the front and back surfaces of the ceramic substrate 13.

By each of the above operations, the coiled ceramic substrate 1
A superconducting coil having a superconducting thin film made of an oxide superconductor formed on the surface of the superconducting coil 3 is fabricated.

In the method for manufacturing a superconducting coil according to this example, a superconducting thin film made of an oxide superconductor is formed on the surface of a ceramic substrate 13 formed in a coil shape by sputtering while being stretched in the axial direction, thereby forming a superconducting coil. Since it is manufactured, a homogeneous superconducting thin film without cracks or cracks can be formed, and a high-strength superconducting coil can be manufactured.

Further, since the superconducting coil is produced by forming a superconducting thin film on the surface of a substrate that has been formed in a coil shape in advance, the production of the superconducting coil can be simplified.

FIG. 9 and FIG. 10 are diagrams for explaining other examples of the method of the present invention.

In the manufacturing method according to this example, first, a raw sheet is manufactured from the raw material of the ceramic substrate by the doctor blade method described in 5 above in the same manner as the manufacturing method according to the previous example.

Next, another raw sheet 7b is placed on the obtained long raw sheet 7a so that their upper surfaces or lower surfaces overlap, and further, these raw sheets 7a and 7b are placed between these raw sheets 7a and 7b. The sheets are bonded together using an adhesive containing a solvent of a different type from the binder contained in the raw sheet, and then pressed using a pressure roller to produce a green sheet. This adhesive is
When the binder contained in the raw sheet is an organic binder such as polyvinyl alcohol, a water-soluble adhesive such as acrylic adhesive or starch adhesive is used; In this case, organic solvent adhesives such as polyvinyl alcohol adhesives and chloroprene adhesives are used.

Next, the green sheet obtained by pasting is
A cylindrical core body 1 is formed with a mold release material lO attached to one surface thereof.
Wrap it around 1 into a coil.

Next is the core! The green sheet wrapped around the green sheet is placed on the setter 12, the core body 11 is gently removed, and then the green sheet is placed in a firing furnace and fired. By this firing, a coil-shaped fired sheet 22 shown in FIG. 9 is produced.

This fired sheet 22 is in a state in which two thin coil-shaped ceramic substrates 23a and 23b can be easily divided from the bonded portion caused by the adhesive portion of the two raw sheets.

Then, an extremely thin piece of metal or a knife is inserted into the bonded part of the fired sheet 22, and the two ceramic substrates 23a, 2 are bonded together.
By dividing them into 3b and gently separating them,
As shown in the θ diagram, two ceramic substrates 23a, 23
b is obtained.

Next, the obtained ceramic substrate is placed in a sputtering apparatus shown in FIG. 6, and a superconducting thin film made of an oxide superconductor is sputtered on the outer or inner surface of the ceramic substrate in the same manner as in the sputtering method according to the previous manufacturing method. Create a coil.

In the manufacturing method according to this example, two thin ceramic substrates are manufactured from one fired sheet and a superconducting coil is manufactured using these ceramic substrates, so a thin ceramic substrate is obtained and a thin superconducting coil is manufactured. There is an effect that can be done.

In each of the above cases, sputtering was used as a means to form a superconducting thin film made of an oxide superconducting material on the surface of a ceramic substrate, but other thin film forming methods such as vapor deposition or chemical vapor deposition (CVD) may also be used. It is also possible to form a superconducting thin film using this method.

Hereinafter, the effects of the present invention will be clarified through Examples.

(Example 1) A superconducting coil was manufactured based on the invention set forth in claim 1.

First, a ceramic substrate was produced using the following raw materials by the doctor blade method.

Raw material powder "3io1% Y, ZrO containing 0.

Solvent...MEK (methyl ethyl ketone) plasticizer...
D-butyl phthalate binder, polyvinyl alcohol dispersant, triolein These raw materials were pulverized and mixed in a ball mill (for about 72 hours) to obtain a uniform slurry. Next, this slurry was formed into a sheet using a doctor blade method, and then dried with hot air to remove the solvent by volatilization and solidify, and then cut into sheets with a width of 10+.
11111. A raw sheet with a length of 1 meter and a thickness of 100 μm was produced.

Place another raw sheet on top of the obtained raw sheet so that the upper surfaces of both sides overlap, and then apply polyvinyl alcohol adhesive between both sides to adhere the two raw sheets to form a green sheet. A sheet was produced. Next, on one side of the green sheet, a sheet-shaped release material (width 10mm+, length 1m, thickness 15mm) mainly composed of boron powder was applied.
0 um) was attached and wound around a cylindrical core material with a diameter of 10 cm with the release material facing inside. Next, this is placed on a setter, the core material is gently pulled out, and then placed in a firing furnace.
A firing treatment was performed at 1500° C. for 1 hour.

Through the above operations, a ceramic substrate in which a long plate made of zirconia was wound into a coil was obtained.

Next, the obtained ceramic substrate was placed in a sputtering apparatus shown in FIG. -0 series superconducting material was sputtered.

Voltage...800■ Gas pressure...LOPa (Ar gas) Temperature...
・・350℃ Film forming rate・・・・50 people/sec.

Then, as shown in Figure 7, a part of the substrate is stretched, rotated and rolled up to one side while sputtering is performed.
A superconducting coil was obtained by forming a Y-Ba-Cu-0 based superconducting thin film on the outer surface of the substrate.

The thickness of the superconducting thin film of the obtained superconducting coil reached IOμ.

In addition, the obtained superconducting coil has a liquid window* (77K"')
It showed a superconducting state inside.

(Example 2) Using the same raw materials as in Example 1 and using the same doctor blade method, a product with a width of 10 mm, a length of 1 meter, and a thickness of 5 mm was prepared.
A 0 μm thin green sheet was produced.

Another green sheet is placed on top of the obtained green sheet so that the top surfaces of both sides overlap, and at this time, acrylic adhesive is applied between both sides to adhere the two green sheets to create a green sheet. did.

Next, on one side of this green sheet, a sheet-like release material (width 10 mm) containing alumina powder as the main component.

1 meter in length and 150 μm in thickness), and was wound around a cylindrical core material with a diameter of ioam with the release material inside.

Next, this was placed on a setter, the core material was gently pulled out, and then placed in a firing furnace and fired at 1500°C for 1 hour.

Next, a thin metal piece was inserted into the bonded portion of the obtained fired sheets to separate them, and the two ceramic substrates were then gently separated to obtain two coiled ceramic substrates.

Next, the obtained ceramic substrate (one piece) was placed in the sputtering apparatus used in Example 1, and a target of Y-Ba-Cu-0 based superconducting material was placed inside the ceramic substrate. Sputtering was performed under sputtering conditions.

Through this sputtering, a superconducting coil was obtained in which a 10 μm thick superconducting thin film was formed on the inner surface of a thin ceramic substrate (40 to 50 μm thick).

This superconducting coil exhibited superconductivity in liquid nitrogen.

"Effects of the Invention" As explained above, the method for manufacturing a superconducting coil according to the present invention has the following effects.

In the present invention, another raw ceramic sheet is placed on a plate-shaped raw ceramic sheet produced by the doctor blade method so that the upper surfaces or lower surfaces of both raw ceramic sheets overlap each other, and then these ceramic raw sheets are The green sheets are pasted together to form a green sheet, then a release material is attached to one side of the green sheet and the green sheet is wound around a core, and then fired, thereby creating a coiled ceramic without warping or waviness. By manufacturing a superconducting coil by forming a thin film of an oxide superconductor on the surface of the ceramic substrate by stretching it in the axial direction using a thin film forming means, It is possible to form a homogeneous superconducting thin film without cracks or cracks, and has the effect of producing a high-strength superconducting coil.

Further, since the superconducting coil is produced by forming a superconducting thin film on the surface of a substrate that has been formed in a coil shape in advance, the production of the superconducting coil can be simplified.

Furthermore, a green sheet is formed by bonding both green sheets together using an adhesive containing a solvent of a different type from the binder contained in the green ceramic sheet, and then a release material is applied to one side of the green sheet. Then, the fired sheet is made into a fired sheet.The fired sheet is then divided from the bonded part to produce two coil-shaped ceramic substrates.Then, the surface number of this ceramic substrate is Since a thin film of an oxide superconductor is formed, a thin ceramic substrate can be obtained, and a thin superconducting coil can be manufactured.

[Brief explanation of the drawing]

1 to 8 are for explaining an example of the method of the present invention. FIG. 1 is a block diagram showing an example of a doctor blade device suitably used to carry out the method of the present invention, and FIG. FIG. 3 is a side view of the green sheet, FIG. 4 is a perspective view of the green sheet wound into a coil, FIG. 5 is a perspective view of the ceramic substrate, and FIG.
The figure is a schematic configuration diagram of a slotting device suitably used to carry out the method of the present invention, and FIG. 7 is a perspective view of essential parts for explaining an example of a method for forming a superconducting thin film on a ceramic substrate.゛Figure 8 is a perspective view of essential parts for explaining another example of forming a superconducting thin film, Figures 9 and 10 are for explaining other examples of the method of the present invention, and Figure 9 is a perspective view of the main parts for explaining another example of forming a superconducting thin film. A perspective view of the sheet, FIG. 1θ is a perspective view of a ceramic substrate obtained by dividing the fired sheet. 7a, 7b... raw sheet, 8... green sheet,
10---Release material, + 1- Core body, 13.23a
. 23b...Ceramics substrate, 20a, 20b
...Superconducting thin film, 21a, 21b...
Superconducting coil, 22...Sintered sheet.

Claims (2)

[Claims] (1) Place another raw ceramic sheet on top of the plate-shaped raw ceramic sheet produced by the doctor blade method so that the top or bottom surfaces of both raw ceramic sheets overlap, and then The sheets are bonded together to form a green sheet, and then a release material is attached to one side of the green sheet, which is then wound around a core, and then fired to produce a coiled ceramic substrate. A method for manufacturing a superconducting coil, comprising forming a thin film of an oxide superconductor on the surface of a substrate using a thin film forming means while stretching the substrate in the axial direction. (2) Place another raw ceramic sheet on the plate-shaped raw ceramic sheet produced by the doctor blade method so that the upper surfaces or lower surfaces of both raw ceramic sheets overlap, and then place the raw ceramic sheet on top of the raw ceramic sheet. A green sheet is formed by bonding both raw sheets together using an adhesive containing a solvent of a different type than the binder contained therein, and then a release material is attached to one side of the green sheet and a core is attached. The fired sheet is then wrapped around the body and then fired to form a fired sheet.The fired sheet is then divided from the bonded portion to produce two coiled ceramic substrates.Then, while stretching the ceramic substrate in the axial direction, A method for manufacturing a superconducting coil, comprising forming a thin film of an oxide superconductor on the surface using a thin film forming means.