Preparation method of high-temperature superconducting wire strip with high strength, high shunt and high heat-conducting property

Abstract

The invention discloses a preparation method of a high-temperature superconducting wire strip with high strength, high shunt and high heat-conducting property. The method comprises the following steps: 1, cleaning a semi-finished superconducting wire strip; 2, putting the cleaned semi-finished superconducting wire strip serving as a cathode and a copper electrode serving as an anode into copper sulfate electroplating liquid, and connecting with a direct-current power supply to form an electroplating device; and 3, after electroplating the cathode semi-finished superconducting wire strip, taking out the cathode semi-finished superconducting wire strip and staying in the air, and forming an electroplated layer of nano-scale copper grains by a process of repeatedly electroplating and taking out for multiple times, thereby obtaining the high-temperature superconducting wire strip. According to the invention, the surface of the semi-finished superconducting wire strip is plated with the electroplated layer of the nano-scale copper crystal grains through electroplating, and the high-temperature superconducting wire strip has high strength, high shunting and high heat-conducting properties by utilizing the strong pinning characteristic of the nano-copper crystal grains and the intrinsic high electric conductivity and high heat-conducting characteristics of copper, resists Lorentz force in a strong magnetic field, and has the characteristics of high conductivity and high heat conductivity. And the shunting and heat conduction capabilities of the high-temperature superconducting wire strip after quenching are improved, the process is simple, and industrial production is easy.

Description

Technical Field

[0001] The present invention belongs to the field of high-temperature superconducting wire tapes, and particularly relates to a preparation method of a high-temperature superconducting wire tape with high strength, high current sharing, and high thermal conductivity. Background Art

[0002] High-temperature superconducting wire tapes, with their zero-resistance characteristics, excellent upper critical field, and ultra-high superconducting transition temperature, exhibit great application potential in frontier fields such as superconducting cables, current limiters, magnets, transformers, magnetic confinement fusion, and hadron colliders, becoming a core technical difficulty that China urgently needs to overcome.

[0003] For the strong Lorentz force and high current sharing stability requirements in strong magnetic field environments above 20T, the superconducting wire materials used in strong magnetic field applications usually adopt an outer sheath design with a composite structure. Such a composite sheath cleverly combines high-strength Hastelloy to provide solid mechanical support, and is used in combination with highly conductive materials such as copper and silver to ensure the effective conduction of current. However, the electrical conductivity of Hastelloy is only 2% of that of copper, and it can hardly effectively carry current. Once the superconducting core wire loses its superconducting state, the current flowing through the Hastelloy will suddenly increase to more than ten times its critical current, directly causing the Hastelloy base tape and the superconducting layer to burn out, and then leading to the failure of the entire superconducting system. To address this challenge, the traditional approach is to thicken the silver layer or copper layer so that the quench current mainly flows through these highly conductive layers. However, this solution is not perfect either, because the relatively low strength of copper in strong magnetic fields above 20T is affected by the Lorentz force and is prone to cause the superconducting wire material to bear excessive tensile stress and break.

[0004] Therefore, the development of an outer sheath material that can meet both high-strength requirements and excellent current sharing performance has become a key bottleneck problem in the current development of high-temperature superconducting materials and urgently needs to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a high-temperature superconducting wire tape with high strength, high current sharing, and high thermal conductivity in view of the above-mentioned deficiencies of the prior art. This method prepares a high-temperature superconducting wire tape by electroplating an electroplated layer of nanoscale copper grains on the surface of a semi-finished superconducting wire tape. By utilizing the strong pinning characteristics of nanoscale copper grains and the intrinsic high conductivity and high thermal conductivity of copper, the high-temperature superconducting wire tape has both high strength, high current sharing, and high thermal conductivity, effectively resists the Lorentz force in a strong magnetic field, and solves the problems of low strength and easy fracture of existing superconducting wire tapes and poor current sharing and thermal conductivity and easy burnout and failure.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a preparation method of a high-temperature superconducting wire tape with high strength, high current sharing, and high thermal conductivity, characterized in that the method comprises the following steps:

[0007] Step 1. Preparation of superconducting sample: Wash the surface of the semi-finished superconducting wire strip with a thin metal layer covering the surface of the superconducting core wire using secondary water to remove surface contaminants;

[0008] Step 2. Assembly of electroplating device: Use the semi-finished superconducting wire strip after cleaning in Step 1 as the cathode and the copper electrode as the anode, both are placed in the copper sulfate electroplating solution and are respectively connected to the positive and negative electrodes of the DC power supply to assemble an electroplating device;

[0009] Step 3. Control of nano copper electroplating: Turn on the power of the electroplating device in Step 2, electroplate the semi-finished superconducting wire strip as the cathode in the copper sulfate electroplating solution for 3 s to 20 s, then take it out and stay in the air for 3 s to 20 s, and then put it back into the copper sulfate electroplating solution and repeat the above electroplating and taking out processes multiple times to form an electroplated layer of nano-scale copper grains on the semi-finished superconducting wire strip to obtain a high-temperature superconducting wire strip.

[0010] The above method for preparing a high-temperature superconducting wire strip with high strength, high current sharing, and high thermal conductivity is characterized in that the thin metal layer covering the surface of the superconducting core wire in Step 1 is obtained by physical deposition method or by thinning a thick metal layer. By covering a thin metal layer on the surface of the superconducting core wire of the semi-finished superconducting wire strip, with a thickness usually of 20 nm to 5 μm, it can avoid direct contact between the electroplating solution and the superconducting layer and cause damage to the ceramic superconducting core wire.

[0011] The above method for preparing a high-temperature superconducting wire strip with high strength, high current sharing, and high thermal conductivity is characterized in that the concentration of the copper sulfate electroplating solution in Step 2 is 0.5 mol / L to 1 mol / L. The copper sulfate electroplating solution with this concentration is beneficial to plating an electroplated layer of nano-scale copper grains.

[0012] The above method for preparing a high-temperature superconducting wire strip with high strength, high current sharing, and high thermal conductivity is characterized in that the current density on the surface of the semi-finished superconducting wire strip during electroplating in Step 3 is 1 A / dm 2 ~5 A / dm 2 . By controlling the current density of electroplating, the electroplating effect is ensured to obtain an electroplated layer of nano-scale copper grains.

[0013] The above method for preparing a high-temperature superconducting wire strip with high strength, high current sharing, and high thermal conductivity is characterized in that the thickness of the electroplated layer in Step 3 is above 10 μm. Generally, there is no strict limit on the thickness of the electroplated layer, but the nano-scale copper grains in the electroplated layer need to be controlled; according to the application working conditions of the high-temperature superconducting wire strip, it is preferably that the thickness of the electroplated layer is above 10 μm.

[0014] The present invention has the following advantages compared with the prior art:

[0015] 1. The present invention prepares a high-temperature superconducting wire and strip by electroplating a plating layer of nanoscale copper grains on the surface of a semi-finished superconducting wire and strip with a thin metal layer covered on the surface of a superconducting core wire by an electroplating process. By utilizing the characteristics that the nanoscale copper plating layer has more grain boundaries and can effectively hinder the movement of dislocations, the strength of the high-temperature superconducting wire and strip is greatly improved, at least doubled or more, effectively resisting the damage or even fracture of the superconducting wire and strip by the Lorentz force in a strong magnetic field.

[0016] 2. Compared with the currently Hastelloy-reinforced superconducting wire and strip, the resistivity of the nanoscale copper in the electroplating layer of nanoscale copper grains electroplated in the present invention is only 1 / 50 of the resistivity of Hastelloy, ensuring that the high-temperature superconducting wire and strip has excellent electrical conductivity. When the high-temperature superconducting wire and strip experiences a quench, the current can be effectively shunted from the nanoscale copper electroplating layer, avoiding the burnout of the high-temperature superconducting wire and strip, that is, ensuring that the high-temperature superconducting wire and strip has high shunting performance.

[0017] 3. Compared with the currently Hastelloy-reinforced superconducting wire and strip, the thermal conductivity of the nanoscale copper in the electroplating layer of nanoscale copper grains electroplated in the present invention is 100 times that of Hastelloy. When the high-temperature superconducting wire and strip experiences a quench, the nanoscale copper can quickly conduct the heat in the high-temperature superconducting wire and strip to the outside, effectively avoiding the accumulation of heat and temperature rise, and further avoiding the burnout of the high-temperature superconducting wire and strip, that is, ensuring that the high-temperature superconducting wire and strip has high thermal conductivity.

[0018] 4. The high-temperature superconducting wire and strip prepared by the present invention has the characteristics of high strength, high shunting and high thermal conductivity, and can meet the working conditions of strong Lorentz force in a strong magnetic field, forced shunting and heat conduction of the metal layer after the superconducting core wire quenches, and has a wide range of applications.

[0019] 5. The present invention realizes the precise control of the growth time of copper grains by controlling the electroplating time, thus very conveniently realizing the preparation of the nanoscale copper electroplating layer, with simple operation and being convenient for industrial production.

[0020] The technical solution of the present invention will be further described in detail below through examples. Detailed implementation mode

[0021] Example 1

[0022] This example includes the following steps:

[0023] Step 1. Preparation of superconducting samples: The semi-finished Bi-based superconducting tape with a 5-μm-thick Ag layer covered on the surface of the superconducting core wire is cleaned with secondary water to wash away the surface contaminants; the semi-finished Bi-based superconducting tape is prepared by the powder-in-tube method and is heat-treated to make the semi-finished Bi-based superconducting tape obtain superconducting current-carrying performance, and then the covered Ag layer is thinned to 5 μm.

[0024] Step 2. Assembly of the electroplating device: Take the semi-finished Bi-based superconducting tape after cleaning in Step 1 as the cathode and the copper electrode as the anode, and place them both in a copper sulfate electroplating solution with a concentration of 1 mol / L. Then connect them to the positive and negative electrodes of a DC power supply respectively to assemble the electroplating device;

[0025] Step 3. Control of nano copper electroplating: Turn on the power of the electroplating device in Step 2, and electroplate the semi-finished Bi-based superconducting tape in the copper sulfate electroplating solution for 20 s to grow electroplated copper grains. The current density on the surface of the semi-finished Bi-based superconducting tape during electroplating is 5 A / dm 2 , then take it out and stay in the air for 20 s to force the electroplated copper grains to stop growing. Then put it back into the copper sulfate electroplating solution and repeat the above electroplating and taking-out process 20 min. An electroplated layer of nano-scale copper grains with a thickness of 15 μm is formed on the semi-finished Bi-based superconducting tape to obtain a high-temperature superconducting tape.

[0026] After testing, the strength of the high-temperature superconducting tape prepared in this example is 1.1 times higher than that of the non-reinforced high-temperature superconducting tape, effectively resisting the Lorentz force under a strong magnetic field and preventing the high-temperature superconducting tape from being broken. At the same time, compared with the reinforced tapes of 304 stainless steel and Hastelloy commonly used, the nano copper electroplated layer on this high-temperature superconducting tape as a reinforcement layer has a shunt performance improvement of 49 times and a thermal conductivity improvement of 98 times. Furthermore, the superconducting performance of the high-temperature superconducting tape is increased by nearly 3.8 times, and the thermal conductivity is increased by 3.95 times. Therefore, when the high-temperature superconducting tape experiences a quench, the current can be shunted from the nano copper electroplated layer, and the generated heat can be transferred to the outside of the magnet faster, preventing the magnet from being burned out. Therefore, the present invention realizes the preparation of a high-temperature superconducting tape with high strength, high shunt performance, and high thermal conductivity.

[0027] Example 2

[0028] This example includes the following steps:

[0029] Step 1. Preparation of the superconducting sample: Wash the semi-finished YBCO superconducting wire with a 20-nm-thick Ag layer on the surface of the superconducting core wire using secondary water to remove surface contaminants. The semi-finished YBCO superconducting wire is first deposited with a superconducting layer by a deposition method, and then a 20-nm-thick silver barrier layer, i.e., an Ag layer, is deposited by a magnetron resonance method;

[0030] Step 2. Assembly of the electroplating device: Take the semi-finished YBCO superconducting wire after cleaning in Step 1 as the cathode and the copper electrode as the anode, and place them both in a copper sulfate electroplating solution with a concentration of 0.5 mol / L. Then connect them to the positive and negative electrodes of a DC power supply respectively to assemble the electroplating device;

[0031] Step 3. Control of nano electroplated copper: Turn on the power supply of the electroplating device in Step 2, and electroplate the semi-finished YBCO superconducting tape in the copper sulfate electroplating solution for 3 s to grow electroplated copper grains. The current density on the surface of the semi-finished YBCO superconducting wire during electroplating is 1 A / dm 2 , then take it out and stay in the air for 3 s to force the electroplated copper grains to stop growing, and then put it back into the copper sulfate electroplating solution and repeat the above electroplating and taking out processes many times for 20 min to form an electroplated layer of nano-scale copper grains with a thickness of 15 μm on the semi-finished YBCO superconducting wire, thereby obtaining a high-temperature superconducting wire.

[0032] After testing, the strength of the high-temperature superconducting wire prepared in this embodiment is 1.5 times higher than that of the non-reinforced high-temperature superconducting wire, thus effectively resisting the Lorentz force under a strong magnetic field and preventing the high-temperature superconducting wire from being broken; at the same time, the nano copper electroplated layer on the high-temperature superconducting wire, as a reinforcement layer, has a shunt performance 49 times higher and a thermal conductivity 99 times higher compared with the commonly used 304 stainless steel and Hastelloy reinforcement tapes. Furthermore, the superconducting performance of the high-temperature superconducting wire is increased by nearly 6 times and the thermal conductivity is increased by 99 times. Therefore, when the high-temperature superconducting wire experiences a quench, the current can be shunted from the nano copper electroplated layer, and the generated heat can be transferred to the outside of the magnet faster, preventing the magnet from being burned out. Therefore, the present invention realizes the preparation of a high-temperature superconducting wire with high strength, high shunt performance, and high thermal conductivity.

[0033] Example 3

[0034] This embodiment includes the following steps:

[0035] Step 1. Preparation of superconducting sample: Wash the semi-finished Bi-based superconducting round wire with a 2.5-μm-thick Ag layer on the surface of the superconducting core wire with secondary water to remove surface dirt; the semi-finished Bi-based superconducting round wire is prepared by the powder-in-tube method and is heat-treated to endow the semi-finished Bi-based superconducting round wire with superconducting current-carrying performance, and then the thickness of the Ag layer on the surface is reduced to 2.5 μm;

[0036] Step 2. Assembly of electroplating device: Use the semi-finished Bi-based superconducting round wire after cleaning in Step 1 as the cathode and the copper electrode as the anode, and place them both in a copper sulfate electroplating solution with a concentration of 0.75 mol / L, and connect them to the positive and negative poles of a DC power supply respectively to assemble an electroplating device;

[0037] Step 3. Control of nano electroplated copper: Turn on the power supply of the electroplating device in Step 2, and electroplate the semi-finished Bi-based superconducting round wire in the copper sulfate electroplating solution for 10 s to grow electroplated copper grains. The current density on the surface of the semi-finished Bi-based superconducting round wire during electroplating is 3 A / dm 2, then take it out, let it stay in the air for 10 s to force the growth of electroplated copper grains to stop, and then put it into the copper sulfate electroplating solution and repeat the above electroplating and taking-out processes for 20 min. An electroplated layer of nano-scale copper grains with a thickness of 30 μm is formed on the semi-finished Bi-based superconducting round wire to obtain a high-temperature superconducting wire.

[0038] After testing, the strength of the high-temperature superconducting wire prepared in this embodiment is increased by 2 times compared with that of the non-reinforced high-temperature superconducting wire, so as to effectively resist the Lorentz force under a strong magnetic field and prevent the high-temperature superconducting wire from being broken; at the same time, the nano-copper electroplated layer on the high-temperature superconducting wire, as a reinforcement layer, has a 49-fold improvement in shunt performance and a 98-fold improvement in thermal conductivity compared with the conventional 304 stainless steel and Hastelloy reinforcement tapes. Furthermore, the superconducting performance of the high-temperature superconducting wire is increased by nearly 4 times and the thermal conductivity is increased by 4.2 times. Therefore, when the high-temperature superconducting wire experiences a quench, the current can be shunted from the nano-copper electroplated layer, and the generated heat can be transferred to the outside of the magnet faster to prevent the magnet from being burned out. Therefore, the present invention realizes the preparation of a high-temperature superconducting wire with high strength, high shunt performance, and high thermal conductivity.

[0039] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength, high-current splitting, and high-thermal-conductivity high-temperature superconducting wire strip, characterized in that: The method comprises the following steps: Step 1: Preparation of superconducting samples: The surface of the semi-finished superconducting wire strip with a thin metal layer on the surface of the superconducting core wire is cleaned with secondary water to remove surface dirt; Step 2: Assembling the electroplating device: placing the semi-finished superconducting wire strip cleaned in step 1 as a cathode and the copper electrode as an anode in a copper sulfate electroplating solution, and connecting them to the positive and negative electrodes of a DC power supply, respectively, to assemble an electroplating device; Step 3: Control of nano-electroplating copper: Turn on the power of the electroplating device in step 2, electroplate the cathode semi-finished superconducting wire strip in the copper sulfate electroplating solution for 3s to 20s, then take it out and let it stay in the air for 3s to 20s, then put it into the copper sulfate electroplating solution and repeat the above electroplating and taking out process many times to form an electroplated layer of nano-scale copper grains on the semi-finished superconducting wire strip to obtain a high-temperature superconducting wire strip.

2. The method for preparing a high-strength, high-current splitting, and high-thermal-conductivity high-temperature superconducting wire strip according to claim 1, characterized in that: The thin metal layer covering the surface of the superconducting core wire in step 1 is obtained by physical deposition or by thinning a thick metal layer.

3. The method for preparing a high-strength, high-current splitting, and high-thermal-conductivity high-temperature superconducting wire strip according to claim 1, characterized in that: The concentration of the copper sulfate electroplating solution in step 2 is 0.5 mol / L to 1 mol / L.

4. The method for preparing a high-strength, high-current splitting, and high-thermal-conductivity high-temperature superconducting wire strip according to claim 1, characterized in that: The current density on the surface of the semi-finished superconducting wire strip during electroplating in step 3 is 1A / dm 2 ~5A / dm 2 .

5. The method for preparing a high-strength, high-current splitting, and high-thermal-conductivity high-temperature superconducting wire strip according to claim 1, characterized in that: The thickness of the electroplating layer in step three is greater than 10 μm.