JP4402928B2 - Oxide superconductor conducting element - Google Patents

Description

  The present invention relates to a current-carrying element using an oxide superconductor such as a current lead, a current limiter, and a permanent current switch.

  When an oxide superconductor is applied to an energization element such as a current lead, it is important to improve the mechanical strength of the energization element, and various reinforcing means have been proposed. The main means is (A) a means for forming a current-carrying element using a composite of an oxide superconductor and a support that supports the oxide superconductor, and (B) an oxide that is not a composite of the support. There is a means for forming a current-carrying element using a superconductor and then reinforcing it by providing a coating layer.

  First, as an example of means for forming a current-carrying element using a composite of the oxide superconductor (A) and a support that supports the oxide superconductor, for example, Patent Document 1 discloses an oxide. A current lead made of a composite of a superconductor and a support made of an insulator or a nonmagnetic metal has been proposed. Patent Document 2 discloses a composite of an oxide superconductor and a support made of a good electrical conductor. A current lead has been proposed.

  When a current-carrying element is formed of a composite of an oxide superconductor and a support, a thermal stress due to a difference in thermal expansion coefficient acts between the oxide superconductor and the support when cooled. As described in FIG. 3, “the thermal expansion coefficient of the support member is preferably as close as possible to the linear expansion coefficient of the oxide superconductor”. Proposed to be close.

  However, the structure such as the current lead described in Patent Document 1 and Patent Document 2 has a problem that there is no electrode terminal for connection to the outside, and connection to the outside is difficult.

  Further, it is difficult to attach an electrode terminal for connection to the outside, and even if the electrode terminal can be attached, there is a problem that the oxide superconductor is damaged at the joint between the electrode terminal and the oxide superconductor. It was.

  Next, as an example of the means for forming a current-carrying element using the oxide superconductor (B) and then reinforcing it by providing a coating layer, for example, Patent Document 4 discloses that both ends of the oxide superconductor are provided. There has been proposed a current lead in which a portion coated with a low resistance metal is provided, and then a portion not coated with metal is coated with a high electrical resistance material or an insulating material to improve the mechanical strength.

  With a structure like the current lead described in Patent Document 4, it is easy to attach electrode terminals for connecting to the outside to the metal covering portions at both ends of the oxide superconductor, and the connection to the outside becomes easy. However, since the junction between the oxide superconductor and the electrode terminal is not covered, there is a problem that the oxide superconductor is damaged in the vicinity of the junction with the electrode terminal.

  However, it has been difficult to sufficiently reinforce the junction between the oxide superconductor and the electrode terminal.

  For example, Patent Document 5 includes a method of applying a resin and a method of coating with FRP (fiber reinforced plastics) as conventional reinforcing techniques. Because of the difference in thermal expansion coefficient, the oxide superconductor side or the resin side cracks in the connection area with the electrode where stress is concentrated when cooling, causing deterioration of superconducting properties and reducing strength. In addition, regarding the coating reinforcement by FRP, “If the oxide superconductor is coated tightly with FRP, thermal stress is applied to the oxide superconductor due to the difference in the coefficient of thermal expansion during cooling, and the oxide superconductor is cracked. In order to generate this, it cannot be tightly coated and firmly fixed, and the oxide superconductor cannot be satisfactorily reinforced.

  Therefore, in Patent Document 5, as an effective reinforcing means, it is proposed that a reinforcing fiber layer is interposed on the surfaces of the oxide superconductor and the electrode terminal, and a resin layer is formed on the surface of the reinforcing fiber layer. Since the surface portion of the reinforcing fiber layer is impregnated with resin and has a structure like FRP, it is considered that it contributes to strength improvement.

JP 63-245909 A JP-A 63-245910 JP-A-4-218215 JP-A-1-133308 JP 2001-76924 A

  The manufacturing process of interposing the reinforcing fiber layer on the surfaces of the oxide superconductor and the electrode terminal and forming the resin layer on the surface of the reinforcing fiber layer is complicated in the manufacturing process of the oxide superconductor energization element. If the coating layer finally has a structure like FRP, the process is simple if the coating layer can be formed from the beginning using FRP.

  However, as described above, conventionally, when the coating layer is formed of FRP, the junction between the oxide superconductor and the electrode terminal cannot be sufficiently reinforced. If the joint between the oxide superconductor and the electrode terminal can be sufficiently and easily reinforced using a material having high strength and high rigidity such as FRP, the industrial value is also improved.

  Therefore, the present invention has an object to provide an oxide superconductor energization element that solves the above problems, can sufficiently reinforce the junction between the oxide superconductor and the electrode terminal with a simple structure, and is not easily damaged during cooling. And

  The oxide superconductor energization element according to the present invention is as follows.

(1) A rod-shaped oxide superconductor, electrode terminals electrically joined to both ends of the oxide superconductor, and a joint covering body that covers the joint between the oxide superconductor and the electrode terminal. Do Ri, the joint covering body comes into close contact covers the joint portion of the electrode terminal and the oxide superconductor through an adhesive member, the absolute value of the thermal expansion coefficient of the current direction of the joint cover body, the oxide An oxide superconductor energization element characterized by being larger than the absolute value of the coefficient of thermal expansion in the ab axis direction of the superconductor.

( 2 ) The joint cover is an anisotropic material with respect to the coefficient of thermal expansion, and the absolute value of the coefficient of thermal expansion in at least one direction is larger than the absolute value of the coefficient of thermal expansion of the electrode terminal, The absolute value of the coefficient of thermal expansion in the direction perpendicular to the direction is smaller than the absolute value of the coefficient of thermal expansion of the electrode terminal. ( 1 ) The oxide superconductor energization element according to ( 1 ).

( 3 ) The direction in which the absolute value of the coefficient of thermal expansion of the joint covering body is large is the direction perpendicular to the joint surface parallel to the energization direction of the oxide superconductor and the electrode terminal. The oxide superconductor energizing element according to ( 2 ).

( 4 ) The oxide superconductor according to any one of (1) to ( 3 ), wherein the joint covering body is at least one selected from a fiber reinforced material, a metal material, or a ceramic material. Current-carrying element.

( 5 ) The oxide superconductor energization element according to (1), wherein the electrode terminal is a good electric conductor.

( 6 ) The oxide superconductor is an oxide in which a RE ₂ BaCuO ₅ phase is finely dispersed in a single-crystal REBa ₂ Cu ₃ O _x phase (RE is one or more selected from Y or a rare earth element). The oxide superconductor energization element according to (1), which is a physical superconductor.

( 7 ) The oxidation according to any one of (1) to ( 6 ) , wherein the two joint covering bodies at both ends are connected by a connector longer than the rod-shaped oxide superconductor. Superconductor conducting element.

( 8 ) The oxide superconductivity according to any one of (1) to ( 7 ) , wherein the two electrode terminals at both ends are connected by a connection body longer than the rod-shaped oxide superconductor. Body energization element.
(9) The oxide superconductor energization element according to (7) or (8), wherein the connection body is an electrically conductive material.

(1 0 ) The oxide superconductor energization element according to any one of (1) to ( 9 ), wherein a surface of the oxide superconductor is covered with the adhesive member.

(1 1 ) (1) to (1 0 ) characterized in that two joint covering bodies at both ends are integrated, and the joint covering body is longer than the rod-shaped oxide superconductor 1 conductor . The oxide superconductor energizing element according to any one of the above.

(1 2 ) The oxide superconductor energization element according to (1 1 ), wherein the joint covering body is an electrically conductive material.

(1 3 ) The oxide superconductor according to (1 2 ), wherein the electrical resistance of the joint covering body is 10 μΩcm or more and 1000 Ωcm or less, and the oxide superconductor energization element is a current lead. Current-carrying element.

(1 4 ) The oxide superconductor energization element according to (1 3 ), wherein the joint covering body is a composite of a resin and a good electric conductor.

(1 5 ) The oxide superconductor energization element according to (1 4 ), wherein the good electric conductor is carbon fiber.

  According to the present invention, it is possible to provide an oxide superconductor energization element that has a simple structure and is not easily damaged during cooling.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an oxide superconductor energization element according to the present invention, and FIG. 2 is an external view of the oxide superconductor energization element.

  1 and 2, the electrode terminal 3 is electrically joined to both ends of the oxide superconductor 1, and the region including the joint portion between the oxide superconductor 1 and the electrode terminal 3 is joined via the adhesive member 2. A structure in which the covering 5 is in close contact with the covering 5 is shown. The structure as shown in FIG. 1 or FIG. 2 can be manufactured by sandwiching the joint portion from above and below with the joint cover 5 divided into two parts.

  The joint cover 5 divided into two parts can be covered more firmly by being fixedly bonded by the bonding member 2 and mechanically fixed by the bolt 4. As shown in FIG. 1 and FIG. 2, the oxide superconductor energization element in the present invention has the electrode terminal 3 for connection to the outside, so that it is easy to connect to the outside.

  In the oxide superconductor element according to the present invention, since the junction between the oxide superconductor and the electrode terminal is covered with the junction covering body, the oxide superconductor is hardly damaged near the junction with the electrode terminal. .

  Here, covering the oxide superconductor, the electrode terminal, and the joint does not only cover the boundary portion where the oxide superconductor and the electrode terminal are joined, but also the oxide superconductor at the joint boundary portion. It means that the surface of the oxide superconductor on the body side and the electrode terminal surface on the electrode terminal side of the junction boundary are also covered.

  Conventionally, when a coating layer is formed of FRP or the like, it is considered that thermal stress is applied to the oxide superconductor due to the difference in thermal expansion coefficient, and the joint between the oxide superconductor and the electrode terminal cannot be sufficiently reinforced. However, in the present invention, since the joint covering body and the oxide superconductor are in contact with each other through the adhesive member, the adhesive member is heated by the difference in thermal expansion coefficient between the oxide superconductor and the joint covering body. It plays the role of a cushioning material that relieves stress and can provide sufficient strength.

  Furthermore, as a result of earnest investigation on the joint strength between the oxide superconductor and the electrode terminal, the present inventors have found that the oxide superconductor is more than the thermal stress due to the difference in thermal expansion coefficient between the oxide superconductor and the coating layer. It was clarified that the thermal stress due to the difference in thermal expansion coefficient between the electrode terminal and the electrode terminal is more important.

  In the oxide superconductor energization element, a joint surface (see FIG. 1) parallel to the energization direction of the oxide superconductor and the electrode terminal (see X in FIG. 1) due to the difference in thermal expansion coefficient between the oxide superconductor and the electrode terminal. 6) tends to distort toward the electrode terminal side in the direction perpendicular to the bonding surface (see Y in FIG. 1), so that the tensile stress is applied to the surface near the bonding portion of the oxide superconductor. appear.

  An oxide superconductor is relatively weak against compressive stress, but very weak against tensile stress. In order to suppress the thermal distortion of the joint surface with the electrode terminal due to such a difference in the coefficient of thermal expansion, it is preferable to cover the joint covering body closely.

  Even if tightly covering only the joint cover, there is a gap between the joint cover and the interface of the oxide superconductor or electrode terminal from a microscopic viewpoint, suppressing the tensile stress generated in the oxide superconductor. The effect of doing becomes smaller.

  Therefore, in order to ensure the effect of suppressing the tensile stress generated in the oxide superconductor, it is necessary to closely bond the bonded portion covering body with no gap through the adhesive member.

  The joint covering body in the present invention is required not only to reinforce by simply covering the joint, but also to suppress the thermal distortion of the joint surface with the electrode terminal as described above.

  Accordingly, the joint covering in the present invention includes fiber reinforced materials such as GFRP (glass fiber reinforced plastics) and CFRP (carbon fiber reinforced plastics), metal materials such as stainless steel, NiCr alloy, Ti alloy, alumina, and nitride. A material having strength and rigidity, such as a ceramic material such as silicon, is preferable, and these materials may be used in combination.

  The adhesive member in the present invention is preferably an epoxy-based resin material, a conductive paste material, or the like. Moreover, as an electrode terminal in this invention, electrical good conductors, such as copper, silver, aluminum, are preferable since the Joule heat_generation | fever of electrode terminal itself can be made small.

In addition, as the oxide superconductor in the present invention, any oxide superconductor such as Y-based, Bi-based, and Tl-based can be used. Among these, as the oxide superconductor used for the energization element, the RE ₂ BaCuO ₅ phase in a single crystal REBa ₂ Cu ₃ O _x phase (RE is one or more selected from Y or rare earth elements). An oxide superconductor finely dispersed in is preferable because of its high critical current density in a magnetic field.

  As for the thermal expansion coefficient of the joint covering body, in the case of the conventional coating layer or support, the thermal expansion coefficient is preferably as close as possible to the thermal expansion coefficient of the oxide superconductor. In the case of the invention, since the purpose is to reinforce the strength of the joint, the absolute value of the coefficient of thermal expansion of the joint cover is preferably larger than the absolute value of the coefficient of thermal expansion of the oxide superconductor.

  The oxide superconductor is an anisotropy material in the ab axis direction and the c axis direction, and when the single crystal oxide superconductor is used, the ab axis direction in which the superconducting current easily flows is directed to the energization direction. It is preferable that the absolute value of the coefficient of thermal expansion of the joint covering body is larger than the absolute value of the coefficient of thermal expansion in the ab axis direction of the oxide superconductor.

  Regarding the thermal expansion coefficient in the energization direction, when the absolute value of the thermal expansion coefficient of the joint covering body is larger than the absolute value of the thermal expansion coefficient of the electrode terminal, at the boundary between the joint covering body and the oxide superconductor, Since a large tensile stress may occur, it is preferable that the absolute value of the thermal expansion coefficient of the bonded portion covering is smaller than the absolute value of the thermal expansion coefficient of the electrode terminal.

  On the other hand, regarding the coefficient of thermal expansion in the direction perpendicular to the joint surface parallel to the energization direction of the oxide superconductor and the electrode terminal, in order to suppress the thermal distortion of the joint surface with the electrode terminal as described above, The absolute value of the coefficient of thermal expansion of the part covering body is preferably larger than the absolute value of the coefficient of thermal expansion of the electrode terminal.

  Therefore, the joint cover is formed using a material having anisotropy with respect to the coefficient of thermal expansion, and the absolute value of the coefficient of thermal expansion in at least one direction is larger than the absolute value of the coefficient of thermal expansion of the electrode terminal, The absolute value of the thermal expansion coefficient in the vertical direction is preferably larger than the absolute value of the thermal expansion coefficient in the ab axis direction of the oxide superconductor, and smaller than the absolute value of the thermal expansion coefficient of the electrode terminal. The direction in which the absolute value of the coefficient of thermal expansion of the covering is large is arranged in the direction in which the joint surface with the electrode terminal is distorted, that is, in the direction perpendicular to the joint surface, and the absolute value of the coefficient of thermal expansion of the joint covering is It is preferable to arrange the small direction in the energization direction.

  In the case of an oxide superconductor energization element, since it is used after being cooled from room temperature, it will be thermally contracted, and the sign of the coefficient of thermal expansion will be negative, but the magnitude relationship of the coefficient of thermal expansion will be absolute without a sign. We will compare by value. For example, when the oxide superconductor has a coefficient of thermal expansion in the ab-axis direction of −0.16% when cooled from room temperature to liquid nitrogen temperature, and copper is used for the electrode terminal, the coefficient of thermal expansion of copper is −0. .32%.

  In this case, the absolute value of the coefficient of thermal expansion in the energizing direction of the joint covering body is preferably 0.16% or more and 0.32% or less, and more preferably 0.2% or more and 0.25% or less. That is, the coefficient of thermal expansion is preferably −0.32% or more and −0.16% or less, more preferably −0.25% or more and −0.2% or less. The coefficient of thermal expansion in the direction perpendicular to the energization direction of the bonded portion covering is preferably -0.32% or more, such as -0.5% or -0.7%.

  In the oxide superconductor energization element according to the present invention, as shown in FIG. By connecting the two joint covering bodies 5, the mechanical strength of the energization element is further improved and the ease of handling is improved.

  Moreover, in the oxide superconductor energization element in the present invention, two electrode terminals 3 may be connected by a connection body 8 as shown in FIG. By connecting the two electrode terminals 3, the mechanical strength of the energization element is further improved, and the ease of handling is improved.

  Further, in the oxide superconductor energization element according to the present invention, as shown in FIG. 5, the adhesive member 2 is placed on the surface of the oxide superconductor other than the joint portion of the oxide superconductor 1 and the joint cover 5, for example. The entire surface of the oxide superconductor may be coated. By covering the surface of the oxide superconductor other than the bonding surface, the mechanical strength of the current-carrying element is further improved, and the ease of handling is improved.

  The structures shown in FIGS. 3, 4, and 5 may be used singly, but by combining them, the mechanical strength of the energization element is further improved and the handling is improved.

  In addition, usually, in order to join the electrode terminals to both ends of the oxide superconductor, it is necessary to provide the joint covering body at two places on both ends of the oxide superconductor. In the oxide superconductor energization element of the present invention, As shown in FIG. 6, the two joint covering bodies at both ends may be integrated.

  In the structure shown in FIG. 6, two joint covering bodies are manufactured from the beginning, and the oxide superconductor and the electrode terminal are electrically joined, and then the integral joint covering body is made of an epoxy resin or the like. The adhesive superconductor is tightly coated on the junction between the oxide superconductor and the electrode terminal.

  Thus, the manufacturing process can be simplified by using the joint covering body integrated from the beginning. Even if integrated in this way, the joint covering body reinforces the joint between the oxide superconductor and the electrode terminal, and is not a support that supports the oxide superconductor. As described above, the value is preferably larger than the absolute value of the coefficient of thermal expansion in the ab-axis direction of the oxide superconductor.

  When the absolute value of the coefficient of thermal expansion of the integrated joint covering is larger than the absolute value of the coefficient of thermal expansion in the ab-axis direction of the oxide superconductor, the coefficient of thermal expansion of the entire oxide superconductor is reduced when cooled. Although the compressive stress acts due to the difference, the oxide superconductor is relatively strong against the compressive stress although it is very weak against the tensile stress. Since there is an adhesive member between them, the adhesive member plays the role of a stress buffer, so even if an integrated joint covering is used, sufficient strength can be obtained and the oxide superconductor is not easily damaged An element can be obtained.

  In FIG. 3, if the connection body 7 that connects the joint cover 5 and the joint cover 5 is made of an electrically conductive material, or the connection body 8 that connects the electrode terminal 3 in FIG. 4 is electrically conductive. If it is made of a material, the connection body can also serve as a bypass circuit when an abnormal situation such as quenching or breakage of the oxide superconductor occurs.

  Similarly, in a structure having an integrated joint cover 5 as shown in FIG. 6, if the joint cover is made of an electrically conductive material, an abnormal situation such as quenching or breakage of the oxide superconductor When this occurs, the connection body can also serve as a bypass circuit.

  In order to have the role of such a bypass circuit, as an adhesive member that closely adheres between the joint covering body and the electrode terminal, not an electrically insulating material such as an epoxy resin, but an electrically conductive material, For example, it is necessary to use silver paste or the like.

  Among oxide superconductor energization elements, the current lead is required to have a function of suppressing the amount of heat penetration in addition to the function of energizing a large current. In the case of a structure having a body, it is preferable to suppress the heat flow that enters through the joint covering body.

  Electrically conductive materials are known to have an inverse relationship between electrical resistivity and thermal conductivity, and good electrical conductors such as copper and silver are also good thermal conductors, so an integrated joint for current leads It is not preferable as a material for the partial covering.

  The electrical resistivity of a good electrical conductor such as copper or silver is about 1 to 10 μΩcm, and the electrical resistivity of the material of the integrated joint covering for current leads is preferably 10 μΩcm or more.

However, an insulator having an electrical resistivity of about 10 ¹² Ωcm such as GFRP cannot play the role of a bypass circuit, and a material having an appropriate electrical conductivity with an electrical resistivity of 1000 Ωcm or less is preferable.

  Accordingly, the electrical resistivity of the material of the integrated joint covering for the current lead is preferably 10 μΩcm or more and 1000 Ωcm or less. Examples of the material having such electric resistivity include alloy metal materials such as stainless steel, titanium alloy, and nichrome (NiCr) alloy, composites of resin and good electric conductors, and conductive plastics.

  An example of a composite of a resin and a good electrical conductor is carbon fiber reinforced plastics (CFRP), which is a composite of an epoxy resin, which is an electrically insulating material, and a carbon fiber, which is a good electrical conductor.

Example 1
Oxygen-free copper electrode terminals are soldered to both ends of an oxide superconductor in which the Y ₂ BaCuO ₅ phase is finely dispersed in a single-crystal YBa ₂ Cu ₃ O _x phase having a cross-sectional area of 4 mm x 3 mm and a length of 40 mm By using stycast 2850FT (manufactured by Nippon Able Stick Co., Ltd.) which is an epoxy resin, GFRP having a thickness of 3 mm is coated tightly on the junction of the oxide superconductor and the electrode terminal, A joint covering as shown in FIG. 1 was produced.

  The joint covering body made of GFRP, which was divided into two in the vertical direction, was bonded and fixed with stycast 2850FT and further mechanically fixed with a stainless steel bolt.

  The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0... In the ab axis direction of the oxide superconductor, the electrode terminal, the direction in which the thermal expansion coefficient of GFRP is small, and the direction in which the thermal expansion coefficient of GFRP is large. 16%, -0.32%, -0.24%, and -0.7%. The direction in which the absolute value of the thermal expansion coefficient of GFRP is small is directed to the energizing direction, and the direction in which the absolute value of the thermal expansion coefficient of GFRP is large is perpendicular to the joint surface parallel to the energizing direction of the oxide superconductor and the electrode terminal. Towards.

  Although the rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 10 times, no breakage such as cracks was found in the oxide superconductor. The critical current was measured before and after the quenching step, and the critical current at the liquid nitrogen temperature was the same as 2400 A before and after the quenching step.

(Comparative Example 1)
For comparison, an oxide superconductor energization element having a structure as shown in FIG. 7 was manufactured. The oxide superconductor and the electrode terminal were made of the same material as in Example 1, but the joint cover was made of a material having a lower shrinkage than the GFRP, and the joint between the oxide superconductor and the electrode terminal was used. The outer peripheral portion of the oxide superconductor except for this was bonded and fixed by stycast 2850FT.

  The energization direction of the low-shrinkage GFRP between room temperature and liquid nitrogen temperature and the thermal expansion coefficient in the direction perpendicular to the energization direction were −0.16% and −0.28%, respectively. The same experiment as in Example 1 was performed for the energization element for comparison, but cracks were observed in the oxide superconductor in the third rapid cooling, and when the rapid cooling was repeated twice, the electrode terminals were joined. The oxide superconductor was damaged at the boundary.

(Example 2)
Electrode terminals made of oxygen-free copper plated with tin are attached to both ends of an oxide superconductor in which a Ho ₂ BaCuO ₅ phase is finely dispersed in a single crystal HoBa ₂ Cu ₃ O _x phase having a cross-sectional area of 3 mm × 3 mm and a length of 40 mm. Electrically bonded by soldering and tightly covering the junction between the oxide superconductor and the electrode terminal using NiCr alloy with a thickness of 3 mm and stycast 2850FT, which is an epoxy resin, and silver paste as an adhesive member Thus, an oxide superconductor energizing element having a joint covering as shown in FIG. 3 was produced.

  The NiCr joint part covering body divided in the vertical direction was bonded and fixed with stycast 2850FT, and further mechanically fixed with stainless steel bolts. The silver paste of the adhesive member was used for adhering the joint surface between the joint cover and the electrode terminal.

  Moreover, the same NiCr alloy was also manufactured on the connection body to which the joint covering body was connected, and was connected by bolting. The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0.16%, −0.32%, and −0.23 for the ab axis direction of the oxide superconductor, the electrode terminal, and the NiCr alloy, respectively. %Met.

  The rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 50 times. The critical current was measured before and after the quenching step, and the critical current at the liquid nitrogen temperature was the same as 1800 A before and after the quenching step.

(Example 3)
Silver-plated aluminum electrode terminals are soldered to both ends of an oxide superconductor in which a Y ₂ BaCuO ₅ phase is finely dispersed in a single crystal YBa ₂ Cu ₃ O _x phase having a cross-sectional area of 4 mm × 3 mm and a length of 40 mm The GFRP having a thickness of 5 mm was coated tightly on the junction between the oxide superconductor and the electrode terminal using stycast 2850GT (trade name) which is an epoxy resin.

  The joint covering body made of GFRP, which was divided into two in the vertical direction, was bonded and fixed with stycast 2850GT, and further mechanically fixed with a bolt made of stainless steel. Thereafter, the connection body between the electrode terminals made of stainless steel was connected to the electrode terminals by soldering to produce an oxide superconductor energization element as shown in FIG.

  The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0... In the ab axis direction of the oxide superconductor, the electrode terminal, the direction in which the thermal expansion coefficient of GFRP is small, and the direction in which the thermal expansion coefficient of GFRP is large. 14%, -0.34%, -0.2%, and -0.55%.

  The direction in which the absolute value of the thermal expansion coefficient of GFRP is small is directed to the energizing direction, and the direction in which the absolute value of the thermal expansion coefficient of GFRP is large is perpendicular to the joint surface parallel to the energizing direction of the oxide superconductor and the electrode terminal. Towards. A rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 50 times, but no breakage such as cracks was found in the oxide superconductor.

  The critical current was measured before and after the quenching step, but the critical current at the liquid nitrogen temperature was the same as 2400 A before and after the quenching step.

Example 4
A silver electrode terminal is electrically connected to both ends of an oxide superconductor in which a Gd ₂ BaCuO ₅ phase is finely dispersed in a single crystalline GdBa ₂ Cu ₃ O _x phase having a cross-sectional area of 3 mm × 3 mm and a length of 40 mm. Then, GFRP with a thickness of 2 mm is tightly coated on the junction between the oxide superconductor and the electrode terminal using Stycast 2850FT, which is an epoxy resin, and then between the two junction coverages. An oxide superconductor energization element as shown in FIG. 5 was manufactured by applying the oxide superconductor surface to the thickness of 1 mm with the same stycast 2850FT.

  The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0... In the ab axis direction of the oxide superconductor, the electrode terminal, the direction in which the thermal expansion coefficient of GFRP is small, and the direction in which the thermal expansion coefficient of GFRP is large. 16%, -0.33%, -0.22%, and -0.6%. The direction in which the absolute value of the thermal expansion coefficient of GFRP is small is directed to the energizing direction, and the direction in which the absolute value of the thermal expansion coefficient of GFRP is large is perpendicular to the joint surface parallel to the energizing direction of the oxide superconductor and the electrode terminal. Towards.

  Although the rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 50 times, no damage such as cracks was observed in the appearance of the oxide superconductor conducting element. The critical current was measured before and after the quenching step, and the critical current at the liquid nitrogen temperature was the same as 1900A before and after the quenching step.

(Example 5)
At both ends of an oxide superconductor in which (Dy, Ho) ₂ BaCuO ₅ phase is finely dispersed in a single crystal (Dy, Ho) Ba ₂ Cu ₃ O _x phase having a cross-sectional area of 4 mm × 4 mm and a length of 60 mm, The plated oxygen-free copper electrode terminals are electrically joined by soldering, and the joint between the oxide superconductor and the electrode terminals is tightly coated with GFRP having a thickness of 3 mm using stycast 2850FT which is an epoxy resin. Thus, an oxide superconductor energization element having an integrated joint covering as shown in FIG. 6 was manufactured.

  The joint cover made of GFRP, in which the joint covers at two locations are integrated, is divided into two parts in the vertical direction, bonded and fixed with stycast 2850FT, and further mechanically fixed with a stainless steel bolt. .

  The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0... In the ab axis direction of the oxide superconductor, the electrode terminal, the direction in which the thermal expansion coefficient of GFRP is small, and the direction in which the thermal expansion coefficient of GFRP is large. 16%, -0.32%, -0.24%, and -0.7%.

  The direction in which the absolute value of the thermal expansion coefficient of GFRP is small is directed to the energizing direction, and the direction in which the absolute value of the thermal expansion coefficient of GFRP is large is perpendicular to the joint surface parallel to the energizing direction of the oxide superconductor and the electrode terminal. Towards.

  Although the rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 50 times, no damage such as cracks was observed in the appearance of the oxide superconductor conducting element. The critical current was measured before and after the quenching step, and the critical current at the liquid nitrogen temperature was the same as 3200A before and after the quenching step.

(Example 6)
At both ends of an oxide superconductor in which (Dy, Ho) ₂ BaCuO ₅ phase is finely dispersed in a single crystal (Dy, Ho) Ba ₂ Cu ₃ O _x phase having a cross-sectional area of 4 mm × 4 mm and a length of 60 mm, The plated oxygen-free copper electrode terminals are electrically joined by soldering, and a 3 mm thick CFRP is bonded to the oxide superconductor and electrode terminals using stycast 2850FT epoxy resin and silver paste. As a result, the oxide superconductor energization element having an integrated joint covering as shown in FIG. 6 was produced.

  The CFRP joint cover, which is a joint of the two joint cover bodies at the two ends, is bonded and fixed by stycast 2850FT, which is divided into two in the vertical direction, and is also mechanically fixed with a stainless steel bolt. . The silver paste of the adhesive member was used for adhering the joint surface between the joint cover and the electrode terminal.

  The coefficient of thermal expansion between room temperature and liquid nitrogen temperature is −0... In the ab axis direction of the oxide superconductor, the electrode terminal, the direction in which the thermal expansion coefficient of CFRP is small, and the direction in which the thermal expansion coefficient of CFRP is large. 16%, -0.32%, -0.25%, and -0.72%. The direction in which the absolute value of the coefficient of thermal expansion of CFRP is small is directed to the energizing direction, and the direction in which the absolute value of the coefficient of thermal expansion of CFRP is large is perpendicular to the joint surface parallel to the energizing direction of the oxide superconductor and electrode terminal Towards.

  Although the rapid cooling process of immersing the oxide superconductor conducting element having the above structure in liquid nitrogen from room temperature was repeated 50 times, no damage such as cracks was observed in the appearance of the oxide superconductor conducting element. The critical current was measured before and after the quenching step, and the critical current at the liquid nitrogen temperature was the same as 3150A before and after the quenching step.

Further, the electrical resistivity of GFRP of Example 5 was 10 ¹² Ωcm, and the electrical resistivity of CFRP of Example 6 was 0.8 Ωcm. In the state where the oxide superconductor energization element of Example 5 and Example 6 is immersed in liquid nitrogen, it is quenched by energizing a current higher than the critical current, and immediately after the quench, the current power supply is turned off and the energization current is cut off. did.

  In this experiment, the energization element of Example 5 could not be energized again because it was melted, but the energization element of Example 6 could be energized again without being melted.

  According to the present invention, an oxide superconductor energization element that has a simple structure and is not easily damaged during cooling can be provided, so that the industrial application range of the oxide superconductor is expanded.

It is sectional drawing which shows the structure of one Example of the oxide superconductor energization element of this invention. It is an external view of one Example of the oxide superconductor energizing element of the present invention. It is sectional drawing which shows the structure of another Example of the oxide superconductor energization element of this invention. It is sectional drawing which shows the structure of another Example of the oxide superconductor energization element of this invention. It is sectional drawing which shows the structure of another Example of the oxide superconductor energization element of this invention. It is sectional drawing which shows the structure of another Example of the oxide superconductor energization element of this invention. It is sectional drawing which shows the structure of the conventional oxide superconductor energization element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oxide superconductor 2 ... Adhesive member 3 ... Electrode terminal 4 ... Bolt 5 ... Joining film body 6 ... Joining surface 7 parallel to the energization direction of an oxide superconductor and an electrode terminal ... Connection body 8 between junction film bodies ... Connector 9 between electrode terminals ... Coating body

Claims (15)

An oxide superconductor rod-shaped, and the electrode terminal electrically joined at both ends of the oxide superconductor, Ri Do junction cover member for covering the joint between the oxide superconductor and the electrode terminal, wherein A junction covering body tightly coats the junction between the oxide superconductor and the electrode terminal via an adhesive member, and the absolute value of the coefficient of thermal expansion in the energizing direction of the junction covering is the oxide superconductor An oxide superconductor energization element characterized by being larger than the absolute value of the coefficient of thermal expansion in the ab axis direction . The joint cover is an anisotropic material with respect to the coefficient of thermal expansion, and the absolute value of the coefficient of thermal expansion in at least one direction is greater than the absolute value of the coefficient of thermal expansion of the electrode terminal and is perpendicular to the direction. 2. The oxide superconductor energization element according to claim 1 , wherein an absolute value of a coefficient of thermal expansion in a direction is smaller than an absolute value of a coefficient of thermal expansion of the electrode terminal. Claim 2, wherein the large direction of the absolute value of the thermal expansion of the bonding portion covering member and a direction perpendicular to the parallel bonding surface conduction direction of the electrode terminal and the oxide superconductor The oxide superconductor energizing element described in 1. The oxide superconductor energization element according to any one of claims 1 to 3 , wherein the joint covering body is at least one selected from a fiber reinforced material, a metal material, or a ceramic material.   The oxide superconductor energization element according to claim 1, wherein the electrode terminal is a good electrical conductor. The oxide superconductor is an oxide superconductor in which a RE ₂ BaCuO ₅ phase is finely dispersed in a single-crystal REBa ₂ Cu ₃ O _x phase (RE is one or more selected from Y or a rare earth element). The oxide superconductor energization element according to claim 1, wherein: The oxide superconductor energization element according to any one of claims 1 to 6 , wherein the two joint covering bodies at both ends are connected by a connection body longer than the rod-shaped oxide superconductor. . The oxide superconductor energization element according to any one of claims 1 to 7 , wherein the two electrode terminals at both ends are connected by a connector longer than the rod-shaped oxide superconductor . The oxide superconductor energizing element according to claim 7 or 8, wherein the connection body is an electrically conductive material. The oxide superconductor energization element according to any one of claims 1 to 9 , wherein a surface of the oxide superconductor is covered with the adhesive member. Integrating two of the joint covering body at both ends, an oxide superconductor according to any of claims 1 to 1 0, wherein the bond coat material is equal to or is longer than the oxide superconductor of the rod-shaped Body energization element. Oxide superconductor current device according to claim 1 1, wherein the joint portion covering member is an electrical conductive material. The electrical resistivity of the bonding portion covering member is higher 10 .mu..OMEGA.cm, at most 1000 .OMEGA.cm, the oxide superconductor current device according to Claim 1 2, wherein the oxide superconductor current element is a current lead. Oxide superconductor current device according to claim 1 3, characterized in that the joint cover body is a composite of a resin and the electric conductor. Oxide superconductor current device according to claim 1 4 wherein the electrical conductor is characterized in that it is a carbon fiber.

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