KR20100013594A - Apparatus and method for manufacturing mgb2 superconducting multi-core wire/tapes and mgb2 superconducting multi-core wire/tapes thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of a boridation magnesium superconduction multiple wire and the boridation magnesium superconduction multiple wire manufactured thereby are provided to protect a boridation magnesium superconduction layer when several fibers are combined. CONSTITUTION: A manufacturing method of a boridation magnesium superconduction multiple wire comprises the following steps: preparing carbon fiber(12) or carbon nanotube fiber on a reel-to reel(11); fixing the prepared carbon fiber or the carbon nanotube fiber on a vacuum evaporation chamber; and introducing the carbon fiber to a vacuum deposition chamber; evaporating boron and magnesium to the carbon fiber or the carbon nanotube fiber; and twisting a plurality of the boridation magnesium superconduction multiple wires.

Description

Method and apparatus for manufacturing magnesium boride superconducting multi-core wire and magnesium boride superconducting multi-core wire produced by the same

The present invention relates to a method for producing a magnesium boride superconducting multicore wire, a manufacturing apparatus, and a magnesium boride superconducting multicore wire produced by the present invention, and more particularly, physical vapor deposition and diffusion reaction heat treatment method on the surface of carbon fiber or carbon nanotube fiber, etc. The present invention relates to a method for producing a magnesium boride superconducting multi-core wire which forms a magnesium boride superconducting wire, and twists a plurality of the formed magnesium boride superconducting wire to produce a magnesium boride superconducting wire.

In general, superconducting wires have a characteristic that the electrical resistance becomes zero below the critical temperature. It is likely to be used in many fields that require it.

In the case of a metal superconductor, the wire rod can be freely formed, processed, and deformed using the metal's deformability (electricity and ductility). For example, in the case of a metal superconductor such as Nb ₃ Sn or NbTi, which is a niobium (Nb) alloy, wire rods can be formed without a complicated process of a tube or powder. However, such a metal type superconductor requires a high temperature liquid helium as a refrigerant because the temperature at which phase transition to the superconductor occurs is below 250 ° C. or less in the case of Nb ₃ Sn superconductor and below 258 ° C. or less in the case of NbTi. .

In the case of the oxide superconductor discovered in the late 1980s, since the temperature at which the phase transition occurs is below minus 197 ° C, it is possible to make a superconducting phase with zero resistance even by using liquid nitrogen, a low-cost refrigerant having a boiling point of minus 197 ° C. However, these materials are ceramics and their mechanical properties are weak, fragile and cannot be made into long wires. Therefore, a method of making a wire rod by making such an oxide superconductor into a powder and filling a tube has been proposed and studied, which is called a PIT (Powder-in-Tube) method.

In other words, the PIT (Powder-in-Tube) method fills a cylindrical tube made of a metal such as Ag with powder of a material having superconductivity to make a billet, and then swage and draw the billet. The process of reducing the diameter of the tube is repeated through the process, and finally a method of manufacturing a superconducting wire by rolling or the like.

However, when manufacturing magnesium boride wire by the conventional PIT method, there are various variables such as characteristics of raw powder of magnesium boride to be filled, mechanical process problem during drawing process, and subsequent heat treatment for synthesis and improvement of raw materials. It had a difficult point that the characteristic by

Particularly, in the case of wire rod manufactured by the conventional powder-in-tube method (PIT method), the density of wire rod is formed due to many pores in the wire rod formed by evaporation of magnesium during the heat treatment process for magnesium boride synthesis or the heat treatment process for improving characteristics. This decreases, resulting in a drop in current conduction characteristics of the manufactured wire rod. That is, the magnesium volatilizes to form boron with the combination of boron, but in the post-heat treatment process, the pores occur in the place where the magnesium is located as the volatilization of magnesium, MgB ₂ The current density decreases slightly because the connectivity between the particles constituting the powder is not completely secured, and even if magnesium boride (MgB ₂ ) is formed, once the heat treatment time exceeds an appropriate time, magnesium is again formed in the magnesium boride already formed. There was a problem that the superconducting properties are lowered as the volatilization changes to a non-stoichiometric composition.

In addition, since the diameter of the tube is reduced through swaging and drawing, and the superconducting wire is finally manufactured by rolling, the diameter of the wire itself is large to reduce the twist. It was difficult to manufacture a long wire rod because it had many microstructures.

On the other hand, sputtering, pulsed laser deposition, hybrid physical-chemical vapor deposition, etc. have been mainly used in the formation of thin films. Thus, it is possible to obtain a dense magnesium boride superconductor structure having almost no pores. However, there is a problem when applied to the wire form because it is deposited on a planar single crystal or a metal substrate.

The present invention, in order to solve the problems of the prior art as described above, unlike the conventional manufacturing method on the surface of the carbon fiber or carbon nanotube fibers already pre-wired, magnesium boride (MgB ₂ by physical vapor deposition and diffusion reaction heat treatment method ), To increase the density of the superconducting wires and to improve the interconnectivity, to provide a method, a manufacturing apparatus and a magnesium boride superconducting multicore wires produced by the magnesium boride superconducting multi-core wire with excellent critical current density The purpose.

In order to achieve the above object, the manufacturing method of the magnesium boride superconducting multi-core wire according to the present invention comprises a manufacturing process of the magnesium boride superconducting single-core wire, a process of twisting the plurality of magnesium boride superconducting single-core wire at a predetermined interval, Specifically

i) winding carbon fibers or carbon nanotube fibers having a circular cross section to a reel-to-reel to prepare them;

ii) fixing the carbon fibers or carbon nanotube fibers wound around the reel to reel in a vacuum deposition chamber and introducing them into the vacuum deposition chamber;

iii) depositing boron and magnesium while moving the carbon fibers or carbon nanotube fibers in the vacuum deposition chamber;

iv) gathering a plurality of magnesium boride superconducting single core wires formed by depositing boron and magnesium in step iii) to prepare a magnesium boride superconducting multicore wire.

In the case of the present invention, it is possible to supplement the mechanical strength of the manufactured magnesium boride superconducting fibers because carbon or carbon nanotube fibers are used as the center portion of the superconducting wire in step i), and the length of the magnesium boron superconducting fibers is not limited. Do not.

Simultaneous deposition of boron and magnesium in the step iii) is characterized in that the temperature range is 500 ~ 1000 ℃, preferably 700 ~ 800 ℃ in an atmosphere within the range of 10 ^-5 ~ 10 ^-1 torr including argon do.

Simultaneous deposition of boron and magnesium in step iii) can be deposited sequentially or simultaneously by each deposition apparatus, the boron deposition unit, the magnesium deposition unit is a physical vapor deposition apparatus sputtering (Sputtering), electron beam deposition (E-beam) Evaporation, Thermal evaporation, Laser Molecular Beam Epitaxy (L-MBE), Pulsed Laser Deposition (PLD), etc. may be configured as a device well known to those skilled in the art. In the case of the present invention, boron is by sputtering, magnesium may be deposited by thermal evaporation, and the material of the evaporative heating boat used in thermal evaporation of magnesium may be tungsten, molybdenum, or the like.

In the case of the present invention, in order to improve superconductivity in iii) depositing boron and magnesium in the vacuum deposition chamber, one selected from carbon, carbon nanotubes (CNT) and silicon carbide may be added as an additive. The additive is added at the time of boron target production so as to be deposited at the time of deposition of the boron, specifically, may be added within the range of 10% by weight.

The added additive may serve to increase the magnetic properties under the magnetic field when the super current flows to the superconductor, which forms a very small nano point inside the superconducting phase when forming the superconducting phase, and exhibits a weak characteristic under the magnetic field.

In the case of the manufacturing method of magnesium boride superconducting multi-core wire of the present invention, a plurality of magnesium boride superconducting single-core wire fibers formed in step iii) are combined to form a multi-core wire, and when composed of the multi-core wire, a plurality of single cores The wire rods can be joined to give twisting at regular intervals.

In the manufacturing method of the magnesium boride superconducting multi-core wire of the present invention, a plurality of single-core wire fibers are combined to form a multi-core wire in step iv), and v) post heat treatment may be performed in the process of twisting.

The v) post-heat treatment step is argon or argon in the range of 0.1 ~ 100 mTorr in the temperature range of 500 ~ 1000 ℃, preferably 700 ~ 800 ℃ during twisting a plurality of magnesium boride superconducting single wire in step iv) Heat treatment at a partial pressure of% hydrogen gas mixture. In the post-heat treatment step, magnesium boride is synthesized by simultaneously heating boron and magnesium on the carbon or carbon nanotube fibers, or by depositing boron and magnesium on carbon or carbon nanotube fibers, and then post-heat treatment. It is also possible to synthesize magnesium boride through.

In addition, the manufacturing process of the magnesium boride superconducting multi-core wire of the present invention may form a cladding of metal on the surface of the magnesium boride superconducting multi-core wire made by the steps i) to iv).

At this time, the material of the metal coating film is a metal such as silver (Ag), copper (Cu), nickel (Ni), iron (Fe), aluminum (Al), titanium (Ti), cobalt (Co), lead (Pb) And their binary or ternary alloys or carbon (C), and are formed using a sputter or a thermal evaporator. The coating film made of the above metal is for protecting the magnesium boride phase when each fiber is in contact with the magnesium boride superconducting multicore wire of the present invention.

Magnesium boride superconducting wire prepared according to the manufacturing method of the present invention has a carbon fiber or carbon nanotube fibers in the center and surrounded by a magnesium boride superconducting material to the outside, the outermost metal layer to protect the magnesium boride superconducting material Characterized by presence.

The apparatus for manufacturing the magnesium boride superconducting wire of the present invention is a vacuum deposition chamber, as shown in Figure 1, the reel-to-reel of the carbon fiber or carbon nanotubes to introduce carbon fibers or carbon nanotubes into the vacuum deposition chamber A device and a reel-to-reel winding device of a magnesium boride superconducting wire wound around a magnesium boride superconducting wire produced in the vacuum deposition chamber, and a boron deposition unit, a magnesium vapor deposition unit, and a multicore wire are placed inside the vacuum deposition chamber. It is characterized in that the twist portion for manufacturing, the post-heat treatment portion is arranged continuously.

As another apparatus for manufacturing the magnesium boride superconducting wire of the present invention, as shown in FIG. 2, a coating film forming unit for forming a cladding made of metal may be further formed on the surface of the magnesium boride superconducting multicore wire.

According to the method of manufacturing magnesium boride according to the present invention, when the superconducting wire is manufactured with a long wire, the central carbon fiber or carbon nanotube fiber can supplement the mechanical strength of the superconducting fiber, and the magnesium boride superconducting layer can maximize the formation of pores. The intergranular connectivity is good because it can be suppressed, and the outermost metal coating layer can protect the magnesium boride superconducting layer when combining multiple fibers or twisting the fiber bundles.

In addition, the carbon fiber or carbon nanotube fiber is released from the mandrel, and processes such as the deposition of boron and magnesium, the twisting process for the manufacture of magnesium boride superconducting multi-core wire, and the post-heat treatment are performed in one reactor in a continuous process. Since the heat treatment is performed for the time necessary for the formation of magnesium boride, the volatilization of magnesium is prevented from the already formed magnesium boride, thereby increasing the density of the superconducting wire and improving the interconnectivity.

In addition, when manufacturing a multi-core wire by the conventional PIT method, the process of reducing the diameter of the tube through the swaging (drawing) and drawing process is repeated, and finally the superconducting wire by rolling or the like method Since it is difficult to give a twist of the wire rods to suppress the magnetic field degradation phenomenon and the alternating current loss which cause the current density to decrease under the magnetic field, in the present invention, the diameters of the wire rods on which each of the deposited magnesium boride superconducting layers are formed are 10 Since the micrometer is thin, it is possible to form a fiber bundle by combining several fibers of a composite structure in which a magnesium boride superconducting layer is formed, and also give a constant pitch to the fiber bundle to suppress magnetic degradation. Can be used, there is no problem that the length is limited because the carbon fiber or carbon nanofibers are already manufactured in wire form, continuous Tablet can be produced magnesium diboride superconducting multi-core wire with.

Hereinafter, a method of manufacturing a superconducting wire of a preferred embodiment according to the present invention with reference to the accompanying drawings. This embodiment is not intended to limit the scope of the invention, but is presented by way of example only.

1 schematically shows a method and apparatus for manufacturing a superconducting wire according to the present invention.

As shown in FIG. 1, according to the method of manufacturing a superconducting wire according to the present invention, first, a carbon fiber or carbon nanotube fiber having a circular cross section is wound on a reel-to-reel device.

The carbon fiber or carbon nanotube wound on the reel-to-reel device thus prepared is introduced into the vacuum chamber through an inlet tube connected to the vacuum chamber as shown in FIG. 1. 13 is a boron evaporation unit, 14 is a magnesium evaporation unit, and as described above, the boron evaporation unit 13 and the magnesium evaporation unit 14 are sputtering, E-beam evaporation, and thermal evaporation method ( Thermal evaporation, laser molecular beam deposition (L-MBE, Laser Molecular Beam Epitaxy), pulsed laser deposition (PLD, Pulsed Laser Deposition) and the like can be configured. In this embodiment, sputtering is used as the boron evaporation section 13, and thermal evaporation is applied as the magnesium evaporation section 14. 15 denotes a post heat treatment furnace, and 16 denotes a wire twisting device for twisting the produced magnesium boride superconducting single-core wire.

When the carbon fibers or carbon nanotubes wound on the reel-to-reel are released and moved into the vacuum deposition chamber, the deposition of boron by sputtering and the deposition of magnesium by thermal evaporator are simultaneously carried out individually by each device. Proceed.

During the deposition of boron and magnesium, the sputter in the vacuum deposition chamber was fixed at a constant output of 200 W, and the deposition was performed for 30 minutes while maintaining the temperature of the thermal evaporator at 700 ° C and the temperature near the substrate at 800 ° C. At this time, the atmosphere inside the vacuum deposition chamber used a reducing atmosphere, that is, argon gas, and the pressure was 2 × 10 ⁻² Torr.

In this embodiment, carbon fibers are used in one vacuum chamber, boron is sputtered, and magnesium is simultaneously deposited on the carbon fiber by thermal evaporation. Magnesium is diffused between boron through high temperature heat treatment under magnesium vapor pressure. Let's do it. By using the simultaneous deposition of boron and magnesium to form an optimal magnesium boride superconducting single core wire, a plurality of magnesium boride superconducting single core wires are gathered in the same vacuum chamber and twisted to form a magnesium boride superconducting multicore wire.

During the deposition and heat treatment in one vacuum deposition chamber section, the inside of the vacuum deposition chamber was maintained at a temperature range of 700 to 800 ° C. The magnesium boride superconducting phase was formed through the heat treatment in the heating and slow cooling process, and then subjected to the post heat treatment process. The magnesium boride superconducting multicore wire is formed while controlling the atmosphere by argon gas and argon and hydrogen mixed gas in the vacuum chamber.

In this embodiment, iii) to prepare a target containing 10% by weight of carbon in the boron target in the step of depositing boron and magnesium on the carbon fiber or carbon nanotube inside the vacuum deposition chamber, by using the target By deposition, the carbon was deposited with boron during the deposition process.

Magnesium boride superconducting single-core wire synthesized by depositing boron and magnesium was fabricated in the form of multicore wire by combining 10 strands of carbon fiber having a thickness of 7 μm using a wire twisting device (16), and twisting at intervals of about 1-5 mm. ). In addition, a post-heating furnace (15) is installed on the wire twisting device (16) in the reaction chamber, and a post-heating furnace (furnace) in which the magnesium boride superconducting multicore wire produced by twisting is maintained at 700 to 800 ° C. 15) The post-heat treatment was performed while moving slowly within.

In addition, a sputter for forming a metal coating layer is provided in the reaction chamber, and a coating film of Cu, Cu alloy, Ag, Ag alloy, Fe, Fe alloy, etc. is formed on the surface of the synthesized magnesium boride superconducting multicore wire by using a sputter. It was.

Figure 3 is a schematic diagram showing the shape of the final wire rod and the magnesium oxide boron superconducting wire deposited by the manufacturing method according to the present invention, 21 represents carbon or carbon nanotube fibers, 22 is deposited magnesium boride, 23 represents a deposited magnesium boride superconducting phase, and 24 represents a metal coating film. As shown in Figure 2 it can be seen that the magnesium boride superconductor of the present invention exhibits a fine microstructure without pores.

4 is an X-ray diffraction result of a magnesium boride superconducting wire deposited according to the embodiment. It can be seen that the magnesium boride superconducting phase was formed from the magnesium boride peak of the X-ray diffraction test result, and carbon appeared because the carbon fiber was used at the center, and the unreacted magnesium phase appeared during the production of magnesium boride.

5 is a scanning electron micrograph of the cross section of the magnesium boride superconductor deposited according to the present invention, it can be seen that the magnesium boride superconductor is synthesized on the surface of the carbon fiber. In the present embodiment, it can be seen that the magnesium boride superconducting layer synthesized by deposition on the surface of the carbon fiber is uniformly formed and is in close contact with the carbon fiber.

FIG. 6 is an energy dispersive spectrometer picture of qualitatively analyzing the surface of a magnesium boride superconductor deposited according to the present embodiment. Since boron and magnesium phase are present, it can be seen that the formed phase is magnesium boride. In addition, the gold shown in Figure 6 is a coating material appeared in the microstructure analysis, the oxygen appeared by the magnesium oxide present in the surface layer.

1 is a schematic diagram of a superconducting wire manufacturing apparatus according to the present invention.

Figure 2 is a schematic diagram of a superconducting wire manufacturing apparatus according to the present invention.

Figure 3 is a photograph showing the cross-sectional schematic diagram of the superconducting multi-core wire according to the present invention and the microstructure of the superconductor.

Figure 4 is an X-ray diffraction photo of the magnesium boride superconductor prepared according to an embodiment of the present invention.

Figure 5 is a scanning electron micrograph of the cross section of the magnesium boride superconductor prepared according to an embodiment of the present invention.

FIG. 6 is a view showing an energy dispersive spectrometer (EDS) on the surface of a magnesium boride superconductor manufactured according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

11 Carbon Fiber Reel-to-Reel Winding Device 12 Carbon Fiber Strand

13 Boron evaporation section 14 Magnesium evaporation section

15 Wire twisting device with 15 post-heat treatment

17 Twisted Magnesium Boride Superconductor 18 Vacuum Atmosphere Chamber

19 Metal film deposition part 21 Carbon or carbon nanotube fiber

22 Deposition Magnesium Boride 23 Deposition Magnesium Boride Superconducting Phase

24 Metal Cladding

Claims (13)

i) winding carbon fibers or carbon nanotube fibers to reel-to-reel to prepare them; ii) fixing the prepared carbon fibers or carbon nanotube fibers to a vacuum deposition chamber and introducing them into the vacuum deposition chamber; iii) depositing boron and magnesium on the carbon fibers or carbon nanotube fibers while moving the carbon fibers or carbon nanotube fibers in the vacuum deposition chamber; And iv) a method of manufacturing a magnesium boride superconducting multi-core wire comprising a step of gathering a plurality of magnesium boride superconducting single-core wire formed by depositing boron and magnesium in step iii). The method of claim 1, The deposition of boron and magnesium in step iii) is a method of producing a magnesium boride superconducting multi-core wire which is made in an atmosphere within the range of 10 ^-7 ~ 10 ^-1 torr including argon. The method of claim 2, Simultaneous deposition of boron and magnesium in step iii) is a method of manufacturing a magnesium boride superconducting multi-core wire, characterized in that deposited in the range of 500 to 1000 ℃. The method of claim 1, Simultaneous deposition of boron and magnesium in step iii) is a method of manufacturing a magnesium boride superconducting multi-core wire, characterized in that the deposition by sequentially or simultaneously with each deposition apparatus. The method of claim 1, The method of manufacturing a magnesium boride superconducting multi-core wire, characterized in that when the boron and magnesium of the step iii) is simultaneously deposited by the sputtering method. The method of claim 1, Magnesium is deposited by thermal evaporation during simultaneous deposition of boron and magnesium in step iii), and the material of the evaporative heating element used in the deposition is tungsten, molybdenum, or the like. The method of claim 1, The iv) after heat treatment step is characterized in that after the deposition of boron and magnesium in step iii), at a temperature in the range of 500 ~ 1000 ℃, argon in the range of 0.1 ~ 100 mTorr, or heat treatment at a partial pressure of argon and hydrogen mixed gas Method for producing magnesium boride superconducting multicore wire. The method of claim 1, Iii) Magnesium boride, characterized in that the addition of one additive selected from carbon, carbon nanotubes (CNT), silicon carbide, pure carbon in order to improve the superconductivity in the deposition of boron and magnesium in the vacuum deposition chamber Method for manufacturing superconducting multi-core wire. The method of claim 8, The additive is a method of producing a magnesium boride superconducting multi-core wire, characterized in that the addition in the range of 10% by weight during the production of boron target to be deposited with boron during the deposition of boron. The method of claim 1, And depositing a metal-coated thin film on the surface of the produced magnesium boride multicore wire in order to prevent destruction of the magnesium boride superconducting multicore wire. The method of claim 10, The metal-coated thin film may be formed of metals such as silver (Ag), copper (Cu), nickel (Ni), iron (Fe), aluminum (Al), titanium (Ti), cobalt (Co), and lead (Pb). A method for producing a magnesium boride superconducting multicore wire selected from binary or ternary alloys or carbon (C). Vacuum deposition chamber; A reel-to-reel winding apparatus of carbon fibers or carbon nanotubes for introducing carbon fibers or carbon nanotubes into the vacuum deposition chamber; And It is composed of a reel-to-reel winding device of the magnesium boride superconducting wire wound around the magnesium boride superconducting wire produced in the vacuum deposition chamber, The boron deposition unit, the magnesium deposition unit and the post-heat treatment unit is arranged in the vacuum deposition chamber, characterized in that the magnesium boron superconducting multi-core wire manufacturing apparatus. Magnesium boride superconducting multicore, in which a carbon fiber or carbon nanotube fiber is in the center, a magnesium boride superconducting material is formed on the outside of the carbon fiber or carbon nanotube fiber, and a metal coating layer is present on the outside of the magnesium boron superconducting material. Wire rod.

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