KR100750963B1 - Structure of low AC loss high temperature superconducting tapes and a fabrication method thereof - Google Patents

Abstract

Disclosed are a structure of a high temperature superconducting wire and a method of manufacturing the same. The structure of the high temperature superconducting wire according to the present invention is implemented by adding a diamagnetic layer on one surface of the tape-shaped superconducting layer. As a result, the AC loss of the high temperature superconducting wire is reduced, and the effect of reducing the AC loss is further increased as the superconducting layer is formed into a multilayer structure.

High Temperature Superconducting Wire, BSCCO, YBCO, PIT Method, CC Method, AC Loss

Description

Structure of low AC loss high temperature superconducting tapes and a fabrication method

1 is a view showing an example of a cross section of a BSCCO wire that is a high temperature superconducting wire,

2 is a view illustrating a high temperature superconducting wire structure according to the present invention;

3 is a flow chart showing an example of a method for manufacturing a high temperature superconducting wire according to the present invention;

4 is a view showing another example of a high temperature superconducting wire structure according to the present invention,

5 is a flowchart illustrating a manufacturing method of FIG. 4, and

6 is a diagram showing measured values of AC loss.

Explanation of symbols on the main parts of the drawings

10, 50: superconducting layer 20, 70: diamagnetic layer

30: magnetic layer 40: metal

60: insulation layer

The present invention relates to a superconducting wire, and more particularly, to a superconducting wire that can reduce the AC loss.

Superconductivity refers to the phenomenon that when a certain kind of metal or alloy is cooled near absolute zero (0K: -273.16 ℃), the electrical resistance suddenly disappears and the current flows without any obstacle.

The temperature at which superconductivity occurs depends on the type of metal. For example, mercury causes superconductivity at 4.2K, but in some alloys of tin and niobium, it is superconducting at 18K. At present, superconductivity has been found in 25 metals, thousands of alloys, and compounds, including lead and thallium. The superconductor causing such a superconducting phenomenon is a low temperature superconductor (LTS: Low Temperature Superconductor) such as Nb ₃ Sn, NbTi, and Nb ₃ Al, YBCO (Y-Ba-Cu-O), BSCCO (Bi-Sr-Ca). -Cu-O) Bi-2212 (Bi ₂ Sr ₂ CaCu ₂ O ₈ ) and Bi-2223 (Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ ), TCBCO (Tl-Ca-Ba-Cu-O) , HBCCO (Hg-Ba-Ca-Cu-O), such as high temperature superconductor (HTS: High Temperature Superconductor) (critical temperature is 25K or more).

Low temperature superconductor has a critical temperature of 25K or less, and has a property of becoming superconductor in liquefied helium. The low temperature superconductor has the advantage of being easy to process as a wire rod and having excellent current characteristics. However, the use of helium has the disadvantage that the cooling cost increases. On the other hand, the high temperature superconductor has a critical temperature of 25K or more, and has the advantage of reducing the cooling cost by using liquefied nitrogen as a refrigerant and having high application potential.

A superconducting material is a material exhibiting superconductivity, and may be classified into a wire rod, a thin film, and a bulk depending on the application form of the superconducting material. Among these, wire rod refers to a superconducting material having a zero electrical resistance at a specific temperature and processed into a wire-like shape for use in various applications. Since the resistance of the conductor is inversely proportional to the cross-sectional area, making wires from high-temperature superconductor materials allows the transfer of more current, resulting in higher power transfer efficiency and smaller current-carrying devices.

In general, superconducting wire is divided into metal-based superconducting wire and oxide-based superconducting wire. Metal-based superconducting wires include Nb ₃ Ti and Nb ₃ Sn wires as metal superconducting wires used at liquid helium temperature, and oxide superconducting wires include Bi-2212 and Bi-2223, which are Bi-based wires. Since Bi-2212 wire rod can be applied in the vicinity of 4K, it is applied to insert coil for NMR (Nuclear Magnetic Resonance), refrigerator conduction cooling magnet, and Superconduction Magnetic Energy Storage (SMES) system. Since Bi-2223 wire has high boundary current density at liquid nitrogen temperature, it is applied to power cable or transformer using liquid nitrogen cooling.

In general, low-temperature superconductors cooled with liquid helium have no problem in making wire rods because they are metallic. However, high temperature superconductors are brittle, making them difficult to wire. There are many methods for manufacturing high temperature superconductors from wire rods, but among these methods, PIT (Powder In Tube) method is considered in consideration of the mechanical and chemical stability of wire rod, possibility of mass production, reproducibility, and excellent critical current density (Jc) value. The CC (Coated Conductor) method is mainly used. The PIT method is a method of putting a high temperature superconducting powder into a metal tube and drawing it, and the CC method is a method of coating a high temperature superconductor on a metal tape. Since the high temperature superconductor has a flat structure due to the properties of the material, the wire efficiency is improved, so both the PIT method and the CC method are based on manufacturing a high temperature superconducting wire in the form of a tape.

In general, the loss of a superconductor is a limited story when the current and the magnetic field do not change. When an alternating magnetic field is applied or an alternating current flows, a loss occurs in the superconductor, which is called AC loss. If there is an alternating current loss, the size of the cooling device must be large, and the heat generated by the alternating current loss may cause the temperature of the superconductor to rise so that the superconducting state cannot be maintained.

One way to reduce this AC loss is to thin the superconducting wire. In other words, several strands of thin superconducting wire have less AC loss than one thick superconducting wire.

In the case of NbTi, a low-temperature superconductor, a French company, Alstom, has developed a "superconducting wire for alternating current" by collecting tens of thousands of very thin superconducting wires with diameters of less than 1 µm. However, high temperature superconductors are difficult to make thin superconductors as in the case of low temperature superconductors due to the characteristics of the material, and it is difficult to make the thickness of 0.1 mm or less with current technology. A cross section of a BSCCO wire, which is a first generation high temperature superconducting wire recently developed by Korea Electrical Research Institute, is shown in FIG. 1.

As described above, since the thickness of the high temperature superconductor is thicker than that of the low temperature superconductor, there is a problem that the AC loss is considerably larger than that of the low temperature superconductor.

The present invention was devised to solve the above problems, and an object of the present invention is to provide a structure of a high temperature superconducting wire and a method for manufacturing the same, which can reduce AC loss.

Embodiment of the high-temperature superconducting wire structure according to the present invention for achieving the above object is characterized in that it comprises a superconducting layer of the tape-shaped, and a diamagnetic layer padded on one surface of the superconducting layer.

Here, the high temperature superconducting wire may be manufactured by a powder in tube (PIT) method, or may be manufactured by a coated conductor (CC) method. In this case, when the high temperature superconducting wire is manufactured by the CC method, the high temperature superconducting wire preferably further includes an insulating layer formed between the superconducting layer and the diamagnetic material layer.

The high temperature superconducting wire may further include a second diamagnetic layer padded on the other surface of the superconducting layer. In this case, when the high temperature superconducting wire is manufactured by the CC method, it is preferable that the high temperature superconducting wire further includes a second insulating layer between the other surface of the superconducting layer and the second diamagnetic material.

Here, the superconducting layer, the diamagnetic layer, and the second diamagnetic layer are LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), and TBCCO (Ti-Ba-Ca-), respectively. Cu-O), HBCO (Hg-Ba-Cu-O), and BSCCO (Bi-Sr-Ca-Cu-O) can be implemented with any one of the high temperature superconductor.

On the other hand, such a high temperature superconducting wire structure, the step of forming a multi-layer structure by applying a diamagnetic layer on one surface of the tape-shaped superconducting layer; And drawing and / or rolling the formed multilayer structure.

In addition, the high temperature superconducting wire structure, the high temperature superconducting wire including coating a superconducting layer on a tape-shaped metal, coating the superconducting layer with an insulating layer, and coating the insulating layer with a semimagnetic layer It also provides a method of preparation.

Another embodiment of the high temperature superconducting wire structure according to the present invention includes a plurality of superconducting layers each having a tape shape and formed in a layer; And a diamagnetic layer padded on an outer surface of the plurality of superconducting layers. Here, the high temperature superconducting wire structure may further include a second diamagnetic layer padded on the outer surface of the plurality of superconducting layers.

As a result, the structure of the high temperature superconducting wire according to the present invention can reduce the AC loss, thereby reducing the size of the cooling device, and more easily maintaining the superconducting state.

Hereinafter, with reference to the accompanying drawings will be described in detail the structure of the high temperature superconducting wire according to the present invention and its manufacturing method.

FIG. 2 is a view illustrating a high temperature superconducting wire structure according to the present invention, and FIG. 2A shows a diamagnetic material on one surface of the superconducting layer, and FIG. 2B shows a diamagnetic material on both sides of the superconducting layer, and FIG. 2C. Indicates that the magnetic material is added to one surface of the superconducting layer. 3 is a flowchart illustrating an example of a method for manufacturing a high temperature superconducting wire according to the present invention.

Referring to the drawings, the superconducting layer 10 is a high-temperature superconducting material, LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O). ), HBCO (Hg-Ba-Cu-O), and BSCCO (Bi-Sr-Ca-Cu-O). Most low temperature superconducting materials are not economical because their critical temperature (Tc) is so low below 30K that expensive cooling media such as liquid helium must be used in the operation of the application. The high temperature superconducting material makes it possible to overcome the application limitation of such low temperature superconducting material. In particular, YBa ₂ Cu ₃ O _7-d (Y123, Tc = 90K), Bi-Sr-Ca- of the Y-Ba-Cu-O system having a critical temperature Tc of not less than the liquid nitrogen temperature (at normal pressure, 77.3K). Cu ₂ O ₂ Bi ₂ Sr ₂ CaCu ₂ O ₈ (Bi-2212, Tc = 85K), Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ (Bi-2223, Tc = 110K), Tl-Ca-Ba-Cu Metal oxide superconducting materials such as -O-based (maximum Tc = 125 K) and Hg-Ba-Ca-Cu-O-based (maximum Tc = 134K) are used to replace inexpensive, lean liquid helium with low-cost liquid nitrogen. Make it available. However, among these materials, high-temperature superconducting materials having practical applicability are Y-Ba-Cu-O-based (hereinafter referred to as 'YBCO-based') and Bi-Sr-Ca-Cu-O-based (hereinafter 'BSCCO-based'). And other materials have very low applicability due to hazards and chemical instability, even at high critical temperatures.

The diamagnetic material layer 20 refers to a layer made of a material having diamagnetism. Here, diamagnetic refers to a phenomenon in which the direction of magnetization occurs opposite to the direction of the magnetic field when a magnetic field is applied to a substance. Diamagnetics are a common phenomenon of matter. However, most diamagnetisms are so weak that if a substance has some paramagnetism, it becomes paramagnetic as a whole. Such materials exhibiting diamagnetic properties include metals such as gold (Au), silver (Ag), zinc (Zn), and copper (Cu), and most gases and organic materials except oxygen. On the other hand, the superconductivity is strong in the superconductor. Due to the strong diamagnetism of the superconductor, the superconductor shows the property of pushing out the superconductor without passing the magnetic field lines from the magnet. This property is called the "Meissner's Effect," and the diamagnetism that represents the Meissner effect is called the complete diamagnetism. The semimagnetic material 20 constituting the high temperature superconducting wire according to the present invention is preferably a material having a strong antimagnetic property, and thus may be implemented with the same superconducting layer as the superconducting layer 10.

In FIG. 2A, the diamagnetic layer 20 is padded on one surface of the tape-shaped superconducting layer 10 as shown in FIG. 2A, or the diamagnetic layer 20 is padded on both sides of the tape-shaped superconducting layer 10 as shown in FIG. 2B. Although only the high temperature superconducting wire of the structure is illustrated, the present invention is not limited thereto, and may be formed as a multilayer structure of a diamagnetic layer padded on one or both surfaces of the plurality of superconducting layers. That is, each of the tape-like superconducting layers are formed to overlap each other, and a multi-layered structure having a three-layer structure or more is formed by adding a diamagnetic layer on one outer surface of the plurality of superconducting layers, or by adding a diamagnetic layer on both outer surfaces. You may. In this case, the effect of reducing the AC loss is further increased.

In addition, in FIG. 2C, unlike the case of FIGS. 2A and 2B, the superconducting layer 10 is provided with a magnetic material 30 such as iron (Fe) and nickel (Ni). This is for comparing and explaining the alternating current loss in the case where the semimagnetic layer 20 is padded on the superconducting layer 10 and the case where the magnetic layer 30 is padded on the superconducting layer 10, which will be described later.

In the case of manufacturing the high temperature superconducting wire according to the present invention according to the PIT method, after forming the multilayer structure of the superconducting layer 10 and the diamagnetic material layer 20 as described above (S101), the formed multilayer structure Drawing (S103) and / or rolling (S105) to produce a high temperature superconducting wire having a multilayer structure.

Here, the PIT method is also referred to as a 'powder filling method', and is a method of sintering after putting superconducting powder in a silver (Ag) tube and sealing it, followed by processing such as swaging, drawing and rolling. At this time, since YBCO-based superconducting materials are fundamentally deformable, it is virtually impossible to make wire rods by powder filling. This is because YBCO has a problem of 3-axis alignment in addition to the deformation problem in order to make a high-quality YBCO wire. Therefore, in the field of high temperature superconducting wires, most of the wires manufactured by the powder filling method are preferably implemented by BSCCO-based superconductors. The advantage of the BSCCO system is that texturing and grain arrangement, which govern the superconductivity (critical current conductance) of the wire rod, can be easily achieved by final thermal and mechanical processes. In addition, the critical current density of the BSCCO wires manufactured in this way is higher than that of conventional low temperature superconductors such as NbTi and Nb ₃ Sn at an absolute temperature of 4.2K and high magnetic field.

The YBCO wire rod has to be manufactured in a new and different way because of the above problems. On the other hand, a CC (Coated Conductor) method, which is a method of coating a YBCO-based coating on a nickel tape, is used.

Figure 4 shows the structure of the high temperature superconducting wire in the case of producing a high temperature superconducting wire according to the CC method, Figure 5 is a flow chart showing the manufacturing method of FIG.

Referring to the drawings, when manufacturing the high-temperature superconducting wire according to the present invention according to the CC method, a tape-shaped metal 40 such as nickel (Ni) is coated with a superconducting layer 50 (S201), the superconducting layer ( 50) is again coated with an insulating layer 60 (S203). The superconducting layer 50 coated by the insulating layer 60 is coated with the diamagnetic layer 70 again (S205). At this time, the diamagnetic material layer 70 is preferably implemented with a YBCO system.

When the AC loss of the high temperature superconducting wire manufactured according to the present invention is measured, the value is as shown in FIG. Here, each of the high temperature superconducting wires were manufactured according to the PIT method, and the superconducting layer 10 and the diamagnetic layer 20 were made of the same BSCCO-based superconducting material. In addition, in order to explain the effect of the high temperature superconducting wire according to the present invention, the configuration as shown in Figure 2c was implemented by adding the BSCCO-based superconducting layer 10 and nickel (Ni) (30).

Referring to FIG. 6, the high temperature superconducting wire (c) formed by applying the diamagnetic material 20 to the superconducting layer 10 according to the present invention has a considerably reduced effect of alternating current loss compared to the high temperature superconducting wire (a) composed of only a superconducting tape. You can see that it is large. On the contrary, as shown in FIG. 2C, the high temperature superconducting wire (b) formed by applying the magnetic material 30 to the superconducting layer 10 has a higher AC loss than the high temperature superconducting wire (a) composed of only the superconducting tape. This may indicate that the reduction of alternating current loss by the superconducting tape is due to the fact that the superconductor is diamagnetic.

 Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

According to the present invention, the AC loss can be reduced by adding a diamagnetic material to the superconducting layer, and the effect of reducing the AC loss is further increased as the superconducting layer is implemented in a multilayer structure.

Claims (15)

Tape-shaped superconducting layer; And It includes a diamagnetic layer padded on one surface of the superconducting layer, The diamagnetic layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba-Cu- O) and BSCCO (Bi-Sr-Ca-Cu-O) is any one of the structure of the high temperature superconducting wire. The method of claim 1, The high temperature superconducting wire is a structure of a high temperature superconducting wire, characterized in that produced by the PIT (Powder In Tube) method. The method of claim 1, The structure of the high temperature superconducting wire further comprises an insulating layer formed between the superconducting layer and the diamagnetic material layer. The method of claim 3, wherein The high temperature superconducting wire is a structure of a high temperature superconducting wire, characterized in that produced by the CC (Coated Conductor) method. The method of claim 1, The structure of the high temperature superconducting wire further comprises a second diamagnetic layer padded on the other surface of the superconducting layer. The method of claim 5, The second diamagnetic layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba) -Cu-O), and BSCCO (Bi-Sr-Ca-Cu-O) -based structure of the high temperature superconducting wire, characterized in that any one. The method of claim 1, The superconducting layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba-Cu- O) and BSCCO (Bi-Sr-Ca-Cu-O) is any one of the structure of the high temperature superconducting wire. A plurality of superconducting layers each having a tape shape and formed in layers; And The structure of the high temperature superconducting wire, characterized in that it comprises a diamagnetic layer padded on one outer surface of the plurality of superconducting layers. The method of claim 8, The structure of the high temperature superconducting wire further comprising a second diamagnetic layer padded on the outer surface of the plurality of superconducting layers. Forming a multilayer structure by applying a diamagnetic layer on one surface of the tape-shaped superconducting layer; And Taking at least one of drawing and rolling on the formed multilayer structure, The diamagnetic layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba-Cu- O) system, and BSCCO (Bi-Sr-Ca-Cu-O) -based high temperature superconducting wire manufacturing method characterized in that any one of. The method of claim 10, The multilayer structure is formed by coating a second diamagnetic layer on the other surface of the superconducting layer, The second diamagnetic layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba) -Cu-O), and BSCCO (Bi-Sr-Ca-Cu-O) system, characterized in that any one of the high temperature superconducting wire manufacturing method. Coating a superconducting layer on the tape-shaped metal; Coating the superconducting layer with an insulating layer; And A method of manufacturing a high temperature superconducting wire, comprising coating the insulating layer with a diamagnetic layer. The method of claim 12, The metal is nickel (Ni) high temperature superconducting wire manufacturing method, characterized in that. The method of claim 12, The diamagnetic layer is a high temperature superconducting wire manufacturing method, characterized in that implemented in YBCO (Y-Ba-Cu-O) system. The method of claim 12, The superconducting layer is LBCO (La-Ba-Cu-O), YBCO (Y-Ba-Cu-O), TBCCO (Ti-Ba-Ca-Cu-O), HBCO (Hg-Ba-Cu- O) system, and BSCCO (Bi-Sr-Ca-Cu-O) -based high temperature superconducting wire manufacturing method characterized in that any one of.

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