JPH01128406A - Manufacture of ceramics system superconductive coil - Google Patents

Abstract

PURPOSE:To make it possible to form a coil concerned directly of raw material powder or a mixture of the raw material powder by firstly processing powder of a ceramics system superconductive material or its raw material powder in a coil, using a metallic container by drawing and coiling followed by sintering. CONSTITUTION:Superconductive material powder is densely filled in a metallic container to be drawn together with the metallic container so as to obtain a wire rod. Then, the wire rod obtained by drawing is coiled so as to obtain a coil having the desired size and shape for being put to a sintering process in order to sinter the superconductive material powder existing inside a coil wire rod. Next, the coil passed the sintering process is insulated, while, when there is a gap between the neighboring wires, the gap is impregnated with the electrically insulating varnish followed by heat-hardening or the like. In this case, when there is no gap between the neighboring wires at least a part of a metal housing originating in the metallic container on the wire surface is removed by chemical treatment or the like so as to provide the gap between the neighboring wires for insulation treatment. Thereby, the coil can be formed directly of powder of a raw material ceramics system conductive material or a mixture of the raw material powder so as not to require a coiling process of a wire rod.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a superconductor coil, and more particularly to a novel method for manufacturing a ceramic superconductor coil containing an oxide of a rare earth element. It is.

[Conventional technology]

Superconducting phenomenon refers to the phenomenon in which electrical resistance completely disappears below the temperature at which this superconducting phenomenon occurs (E!
! temperature) differs depending on the material. Since materials with high critical temperatures can be easily cooled, the development of materials with as high critical temperatures as possible has been particularly popular recently. In addition to a high critical temperature, the upper limit of current that can be passed in a superconducting state (critical current) is also an important point for the practical application of ceramic materials. This is because, for practical use, it must be made into a wire, for example, but since the current that can be passed per unit cross-sectional area of ceramic materials is small, the key to practical application is how high a critical current can be obtained. be.

By the way, alloy-based and ceramic-based materials are well known as materials that cause superconducting phenomena, and the development of ceramic-based materials has been particularly advanced recently, and the development of ceramic-based superconducting materials with high critical temperatures is progressing rapidly. However, although it is necessary to process superconducting materials into long wires, tapes, etc. for practical use, ceramic superconducting materials are hard and brittle and cannot be drawn into wires like metal materials. When ceramic superconducting wire is used as a motor coil, it is necessary to further wind the wire into a coil, but the wire may break during coil winding, or even if it does not break, the superconducting properties of the wire may be affected by applying winding stress. There are problems such as a decrease in

[Problem that the invention seeks to solve]

Therefore, in view of the above points, an object of the present invention is to provide a new method for directly manufacturing a coil of ceramic superconducting material from a powder of the material or a mixture of its raw material powder.

[Means for solving the problem] The purpose is to fill a metal container with powder of a ceramic M4 conductive material or its raw material powder, draw a wire together with the metal container, and cut the obtained wire into desired dimensions. This is achieved by a method for manufacturing a ceramic superconductor coil, which is characterized in that the coil is wound into a coil, the obtained coil is subjected to a sintering process, and then adjacent wires of the coil are insulated using an electrically insulating varnish. .

The manufacturing method of the present invention is characterized in that ceramic superconducting material powder or its raw material powder is processed in advance into a coil shape with desired dimensions and structure by wire drawing and coil winding using a metal container, and then sintered. Therefore, there is no need for coil winding of the wire, which has been a problem in the past, and all the various problems associated with coil winding can be solved.

The superconducting material is not particularly limited as long as it is ceramic-based, and ceramic-based materials containing rare earth element oxides are particularly preferred.

Such materials include, for example, barium/yttrium/copper/oxygen, barium/lanthanum/copper/oxygen, strontium/lanthanum/copper/oxygen, barium/scandium/copper/oxygen, or calcium/lanthanum/copper/oxygen as material components. There are ceramics with a composition of
Preferably, it is a material consisting of barium, yttrium, copper, and oxygen, which is a yttrium-based material that is becoming mainstream in ceramic materials. Furthermore, when using this yttrium-based superconducting material, the preferred blending ratio is Ba:
Y:Cu:O=2:1:3:6-7
It is.

In the present invention, ceramic powder having such a composition is used. The method for producing the powder may be any conventionally known method and is not particularly limited. etc.) → sintering → re-powdering of the sintered body.

Furthermore, in the present invention, a mixture of raw material powders such as barium carbonate, yttrium oxide, and copper oxide can also be used. Superconducting materials are called superconducting materials.

In the method of the present invention, first, a metal container is densely filled with superconducting material powder, and the metal container is drawn into a wire to obtain a wire. Metal containers include silver, copper, stainless steel,
A bottomed pipe made of aluminum or the like is preferred.

The wire obtained by drawing is then coiled to form a coil of desired dimensions and shape, and the obtained coil is subjected to a sintering process to sinter the superconducting material powder present inside the coil wire. .

The sintering temperature varies depending on the ceramic used, but
In the case of the superconducting material powder described above, the temperature is 700 to 1000°C.
1 Preferably, the temperature is about 800 to 950°C, and the time required for sintering is about 1 to 24 hours. In addition, in order to supply a sufficient amount of oxygen to the superconducting material powder in the wire during this sintering, conventionally known methods such as sintering in an oxygen atmosphere,
It is preferable to take the following measures.

If the coil obtained through the sintering process has a gap between the adjacent wires, the gap can be insulated by impregnating the gap with electrically insulating varnish and then hardening. If there is no gap between the soil and the adjacent wire, remove at least part of the metal sheath derived from the metal container on the surface of the wire by chemical treatment, etc., create a gap between the soil and the adjacent wire, and then insulate it in the same manner as above. Bye.

(Examples) Hereinafter, the method of the present invention will be explained in more detail based on Examples.

Example 1 A ceramic superconducting material whose composition is barium, yttrium, copper, and oxygen, with a mixing ratio of Ba:Y:Cu.
:O=2:1:3:6. A material powder with an average particle diameter of 5 μm prepared in a diameter of 6 III sealed at one end
It was densely packed into a silver pipe with a diameter of 1'I0.5ms under vacuum and drawn using a cassette die to obtain a wire with an outer diameter of In. Next, this wire rod was tightly spirally wound around a ceramic cylinder with an outer diameter of 10 mm and a length of 50 mm to form a coil, and then sintered at 900'C in an oxygen atmosphere for 24 hours, and finally Most of the silver sheath of the coil was dissolved and removed using a wt % nitric acid aqueous solution, and the superconducting coil was thoroughly washed with water and dried to obtain a superconducting coil. The obtained coil was immersed in polyimide varnish under reduced pressure, and the process of baking at 250° C. with sufficient sag removed was repeated five times to electrically insulate between the coil wires.

Example 2 Electrical insulation treatment was carried out using the same method and conditions as in Example i using material powder with an average particle size of 5 μm prepared at a blending ratio of Ba:Y:Cu:O=22L:3:1.0. I got a coil.

Example 3 A ceramic superconducting material whose composition is barium, lanthanum, copper, and oxygen, with a mixing ratio of Ba:Y:Cu:
An electrically insulated coil was obtained in the same manner and under the same conditions as in Example 1 using material powder with an average particle size of 5 μm prepared in the ratio of 0=0.15:0.85:1:4.

The critical temperature and critical current density of each coil obtained in each example were measured by the following method, and the results shown in Table 1 were obtained.

(Method for measuring critical temperature and critical current density) 1) A critical temperature sample (2 to 3 cm long) at a current density of 0.1 A/c
(d) After cooling with liquid helium, changes in electrical resistance and temperature were measured using an X-Y recorder using a four-terminal method, and the temperature at which the electrical resistance value became zero was determined.

2) Immerse the critical current density sample (length 2 to 3C11) in liquid helium together with the power lead, gradually increase the current value, and measure the iR drop and current change with an X-Y recorder using the four-terminal method. ! The current value at which R drop appears was determined.

Table 1 [Effects of the Invention] As explained above, according to the manufacturing method of the present invention, it is possible to directly manufacture a coil made of a ceramic superconducting material powder or a mixture of its raw material powders.

Therefore, there is no need for coil winding of the wire, which has been problematic in the past, and all the various problems associated with coil winding are solved.

Claims (2)

[Claims] (1) Fill a metal container with ceramic superconducting material powder or its raw material powder, draw a wire together with the metal container, wind the obtained wire into a coil to the desired size, and bake the obtained coiled material. A method for manufacturing a ceramic superconductor coil, which comprises insulating adjacent wires of the coil using an electrically insulating varnish during the tying process. (2) The components of the superconducting material are barium/yttrium/copper/oxygen, barium/lanthanum/copper/oxygen, strontium/lanthanum/copper/oxygen, barium/scandium/copper/oxygen, or calcium/lanthanum/copper/oxygen. A method for manufacturing a ceramic superconductor coil according to claim (1), characterized in that: