Superconducting wire and preparation method thereof

Abstract

The invention discloses a superconducting wire and a preparation method thereof, and belongs to the technical field of superconducting wires. According to the invention, the ceramic insulating material is sprayed on the surface of the Nb3Sn superconducting wire through a plasma spraying process, and the superconducting wire containing the insulating layer is prepared. The prepared insulating layer is uniform and compact and is tightly combined with the Nb3Sn superconducting wire, and the insulation problem of the Nb3Sn superconducting wire after phase forming heat treatment is effectively solved. The preparation method provided by the invention has the advantages of high working efficiency, simple repairing process, high repeatability and the like, and can be widely applied to superconducting wires needing high-temperature phase forming heat treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting wires and relates to a superconducting wire and a preparation method thereof. Background Art

[0002] Nb3Sn superconducting wires have important application value in many fields such as energy transmission, magnetic resonance imaging and particle accelerators. However, high-performance Nb3Sn superconducting wires must undergo high-temperature heat treatment to complete the phase reaction. At the same time, in order to ensure its stable operation and avoid safety hazards such as leakage and performance degradation, the superconducting wires must also have good insulation properties.

[0003] Traditional insulation methods are difficult to meet the strict insulation performance requirements of superconducting wires in high-temperature environments. For example, some organic insulating materials will decompose or age under high temperature conditions, and then lose their insulation effectiveness; and some inorganic insulating materials, such as glass fiber insulating materials, are difficult to form a tightly bonded insulating layer with superconducting wires in practical applications. In addition, the mechanical properties of glass fiber materials are easily affected by environmental conditions, especially in high temperature and high humidity environments, their mechanical properties will decrease significantly, resulting in weakened insulation performance. The weaving process of glass fiber materials is time-consuming and inefficient, and they are prone to wear during the weaving process, forming weak points in the weaving, affecting the insulation effect. Once the insulation performance does not meet the standards, the repair process is also quite complicated, affecting the reliability and stability of superconducting wires in high temperature environments.

[0004] Therefore, a new method is developed to ensure that the surface insulation layer of Nb3Sn superconducting wire remains intact and has excellent insulation properties after phase heat treatment. Summary of the invention

[0005] The present invention aims to solve the problems and defects in the above-mentioned prior art. The present invention provides a method for preparing a high-temperature insulation layer of a Nb3Sn superconducting wire, which is used to solve the problems that the existing Nb3Sn superconducting wire uses glass fiber insulation, has low working efficiency, is difficult to repair, and has reduced mechanical properties and weakened insulation properties after high-temperature phase heat treatment.

[0006] In a first aspect, the present invention provides a method for preparing a superconducting wire, comprising: preparing an insulating layer on the surface of a superconducting wire element. The method of the present invention comprises: spraying insulating material on the surface of a superconducting wire element using a plasma spraying process to prepare a superconducting wire containing an insulating layer.

[0007] Furthermore, the superconducting element of the present invention is Nb3Sn; the preparation method of Nb3Sn is any one of the internal tin method and the bronze method.

[0008] Furthermore, the insulating material of the present invention is a mixture of any one of aluminum oxide and 8YSZ, any one of silicon nitride and aluminum nitride, and any one of polyimide, polyetheretherketone, and aramid fiber; The particle size of the mixture is 5-100 μm.

[0009] Furthermore, before preparing the insulating layer on the superconducting base wire of the present invention, the surface of the superconducting base wire needs to be polished and cleaned.

[0010] Furthermore, the plasma gas used in the plasma spraying of the present invention is any one of argon, helium, and nitrogen, or a mixture of the two, or any one of them mixed with hydrogen.

[0011] Furthermore, the flow rate of the plasma gas of the present invention is 10-60 L / min; The power of the plasma gas is 10-120 kW; The purity of the plasma gas is 99.99% or above.

[0012] Furthermore, when the plasma spraying process of the present invention is used for spraying, the distance between the spray gun and the superconducting baseline is 10 to 150 mm; The spraying method is 360° rotary spraying, and the rotation speed of the spray gun is 100~500rpm; The rotation method is forward-reverse alternating spraying.

[0013] Furthermore, when the plasma spraying process of the present invention is used for spraying, the line speed of the superconducting baseline is 5-30 m / min; The powder feeding rate is 5~30g / min.

[0014] Furthermore, after the plasma spraying of the present invention is completed, the superconducting wire is subjected to water cooling or air cooling.

[0015] In a second aspect, the present invention provides a superconducting wire, which is produced by the above-mentioned production method.

[0016] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: 1. The present invention adopts plasma spraying technology to cover a uniform and dense ceramic insulation layer on the surface of the Nb3Sn superconducting wire. The insulation layer can still maintain good insulation performance after the high-temperature phase heat treatment of the superconducting wire, effectively isolate the superconducting wire from the external environment, prevent leakage and the like, and ensure the normal operation of the superconducting wire after the high-temperature phase heat treatment.

[0017] 2. The present invention adopts plasma spraying technology to achieve Nb3Sn superconducting wire insulation. In terms of work efficiency, plasma spraying insulation can accurately and quickly form a uniform, continuous and thickness-controlled insulating layer on the surface of the superconducting wire through automated equipment, greatly improving the working speed, while traditional glass fiber insulation is slow and time-consuming.

[0018] 3. The present invention adopts plasma spraying technology to realize Nb3Sn superconducting wire insulation. In terms of repair characteristics, when the plasma sprayed insulation layer is partially damaged, it can be quickly repaired through a specific plasma spraying process. The operation is simple and the insulation performance is highly restored after repair. Once the traditional glass fiber insulation is damaged, the repair process is complicated and cumbersome, and it often requires large-scale removal of the glass fiber insulation layer and rewinding, which is costly and time-consuming to repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Process flow chart for preparing insulating layer for plasma sprayed Nb3Sn superconducting wire. DETAILED DESCRIPTION

[0020] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0021] Example 1 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0022] S1: Select a Nb3Sn superconducting baseline made by conventional internal tin method, the wire diameter of the Nb3Sn superconducting baseline is Φ2.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0023] S2: Alumina powder, silicon nitride powder and polyimide powder are mixed evenly according to mass percentages of 70%, 25% and 5%, and a powder with a particle size of 20-50 μm is prepared by mechanical ball milling as an insulating material. The purity of the aluminum oxide powder, silicon nitride powder and polyimide powder is not less than 99.99%.

[0024] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: the plasma gas is a mixture of argon and helium, the purity of argon and helium reaches more than 99.99%, the argon flow rate is 30L / min, and the helium flow rate is 10L / min; the power is set to 40kW. The distance between the spray gun and the superconducting baseline is 70mm, the spray gun rotation speed is 100rpm, the superconducting baseline feed speed is 30m / min, and the powder feeding rate is 5g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0025] S4: The superconducting wire after spraying is post-processed by cooling it through air cooling to further improve the density and bonding strength of the insulation layer.

[0026] Example 2 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0027] S1: Select a Nb3Sn superconducting baseline made by conventional bronze method, the wire diameter of the Nb3Sn superconducting baseline is Φ1.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0028] S2: 8YSZ (8% yttria-stabilized zirconia) powder, aluminum nitride powder and polyetheretherketone powder are mixed evenly in a mass percentage of 45%, 45% and 10%, and a powder with a particle size of 5-15μm is prepared by a sol-gel method as an insulating material. The purity of 8YSZ powder, aluminum nitride powder and polyetheretherketone powder is not less than 99.99%.

[0029] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: the plasma gas is a mixture of argon and helium, with an argon flow rate of 40L / min and a helium flow rate of 5L / min; the power is set to 100kW. The distance between the spray gun and the superconducting baseline is 20mm, the spray gun rotation speed is 500rpm, the superconducting baseline feed speed is 5m / min, and the powder feeding rate is 30g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0030] S4: The superconducting wire after spraying is post-processed by cooling it through air cooling to further improve the density and bonding strength of the insulation layer.

[0031] Example 3 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0032] S1: Select a Nb3Sn superconducting baseline made by conventional bronze method, the wire diameter of the Nb3Sn superconducting baseline is Φ1.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0033] S2: 8YSZ (8% yttria-stabilized zirconia) powder, silicon nitride powder and aramid fiber powder are mixed evenly in mass percentages of 45%, 45% and 10%, and sieved to form a powder with a particle size of 50-70 μm as an insulating material. The purity of 8YSZ powder, silicon nitride powder and aramid fiber powder is not less than 99.99%.

[0034] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: the plasma gas is a mixture of hydrogen and nitrogen, with a hydrogen flow rate of 5L / min and a nitrogen flow rate of 55L / min; the power is set to 120kW. The distance between the spray gun and the superconducting baseline is 150mm, the spray gun rotation speed is 500rpm, the superconducting baseline feed speed is 5m / min, and the powder feeding rate is 30g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0035] S4: The superconducting wire after spraying is post-processed by cooling it through air cooling to further improve the density and bonding strength of the insulation layer.

[0036] Example 4 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0037] S1: Select a Nb3Sn superconducting baseline made by conventional internal tin method, the wire diameter of the Nb3Sn superconducting baseline is Φ2.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0038] S2: Aluminum oxide powder, aluminum nitride powder and polyimide powder are mixed evenly in a mass ratio of 7:2:1, and sieved to prepare a powder with a particle size of 70-100 μm as an insulating material. The purity of the aluminum oxide powder, aluminum nitride powder and polyimide powder is not less than 99.99%.

[0039] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: argon is used as the plasma gas, the purity of which reaches more than 99.99%, and the argon flow rate is 10L / min; the power is set to 10kW. The distance between the spray gun and the superconducting baseline is 10mm, the rotation speed of the spray gun is 100rpm, the feed speed of the superconducting baseline is 30m / min, and the powder feeding rate is 5g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0040] S4: The superconducting wire after spraying is post-processed by cooling it through air cooling to further improve the density and bonding strength of the insulation layer.

[0041] Example 5 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0042] S1: Select a Nb3Sn superconducting baseline made by conventional internal tin method, the wire diameter of the Nb3Sn superconducting baseline is Φ2.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0043] S2: Alumina powder, silicon nitride powder and polyetheretherketone powder are mixed evenly in a mass ratio of 10:9:1, and sieved to prepare a powder with a particle size of 70-100 μm as an insulating material. The purity of the aluminum oxide powder, silicon nitride powder and polyetheretherketone powder is not less than 99.99%.

[0044] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: helium is used as the plasma gas, the purity of which reaches more than 99.99%, and the helium flow rate is 30L / min; the power is set to 50kW. The distance between the spray gun and the superconducting baseline is 60mm, the rotation speed of the spray gun is 100rpm, the feed speed of the superconducting baseline is 30m / min, and the powder feeding rate is 5g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0045] S4: The superconducting wire after spraying is post-processed by cooling it with water to further improve the density and bonding strength of the insulation layer.

[0046] Example 6 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0047] S1: Select a Nb3Sn superconducting baseline made by conventional bronze method, the wire diameter of the Nb3Sn superconducting baseline is Φ1.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0048] S2: Aluminum nitride powder, 8YSZ (8% yttria-stabilized zirconia) powder and aramid fiber powder are mixed evenly in mass percentages of 45%, 45% and 10%, and sieved to form a powder with a particle size of 50-70 μm as an insulating material. The purity of aluminum nitride powder, 8YSZ powder and aramid fiber powder is not less than 99.99%.

[0049] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: nitrogen is used as the plasma gas, and the nitrogen flow rate is 60L / min; the power is set to 60kW. The distance between the spray gun and the superconducting baseline is 80mm, the rotation speed of the spray gun is 500rpm, the superconducting baseline feed speed is 5m / min, and the powder feeding rate is 30g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0050] S4: The superconducting wire after spraying is post-processed by cooling it with water to further improve the density and bonding strength of the insulation layer.

[0051] Example 7 This embodiment provides a method for achieving high temperature insulation of Nb3Sn superconducting wire based on plasma spraying.

[0052] S1: Select a Nb3Sn superconducting baseline made by conventional bronze method, the wire diameter of the Nb3Sn superconducting baseline is Φ1.0mm. Use ethanol to clean the surface of the Nb3Sn superconducting baseline to remove the surface oil, then use a scouring pad to polish the surface to remove the oxide layer, so that the surface of the Nb3Sn superconducting baseline has a certain degree of roughness, ultrasonically clean the superconducting baseline and dry it, so that the surface of the Nb3Sn superconducting baseline is clean and conducive to the attachment of the insulating layer.

[0053] S2: 8YSZ (8% yttria-stabilized zirconia) powder, aluminum nitride powder and aramid fiber powder are mixed evenly in mass percentages of 45%, 45% and 10%, and sieved to form a powder with a particle size of 50-70 μm as an insulating material. The purity of 8YSZ powder, aluminum nitride powder and aramid fiber powder is not less than 99.99%.

[0054] S3: Start the plasma spraying equipment, feed the prepared insulating powder into the plasma jet through the powder feeding device, and spray it on the surface of the Nb3Sn superconducting baseline to form an initial insulating layer. The plasma spraying parameters are: the plasma gas is a mixture of hydrogen and helium, with a hydrogen flow rate of 5L / min and a helium flow rate of 50L / min; the power is set to 100kW. The distance between the spray gun and the superconducting baseline is 100mm, the spray gun rotation speed is 500rpm, the superconducting baseline feed speed is 5m / min, and the powder feeding rate is 30g / min. During the spraying process, 360° rotary spraying is adopted, and the rotation method adopts positive-reverse alternating spraying to ensure that the insulating material can be evenly sprayed on the surface of the superconducting baseline. The spraying situation is observed in real time through the monitoring equipment, and the equipment parameters are adjusted in time to ensure the uniformity and stability of the spraying.

[0055] S4: The superconducting wire after spraying is post-processed by cooling it through air cooling to further improve the density and bonding strength of the insulation layer.

[0056] Example 8 This embodiment provides performance parameters of superconducting wires.

[0057] Table 1 Performance parameters of Nb3Sn superconducting wire

[0058] As shown in Table 1, the present invention sprays an insulating layer on the Nb3Sn superconducting baseline through plasma spraying technology. Compared with traditional glass fiber insulation, the working efficiency is increased from 10m / h to 300~1800m / h, which is 30~180 times higher; the insulation resistance is also increased from 500MΩ to 2000MΩ, which is 4 times higher; the leak repair rate is also increased from 5h / time to 0.5h / time, which is 10 times higher. The insulation efficiency and insulation resistance of the Nb3Sn superconducting baseline are effectively improved, and the leak repair time is greatly reduced, which improves the working efficiency and reduces the repair cost.

[0059] The present invention controls the thickness of the insulating layer by controlling the plasma gas, gas flow, power, spray distance, spray gun rotation speed, powder feeding rate and line speed. When the gas flow rate increases and the power increases, the plasma jet speed and the powder particle flight speed will increase, and the insulating layer will be denser. In addition, after the insulating layer is sprayed on the Nb3Sn superconducting wire by plasma spraying technology, water cooling or air cooling is performed to further improve the density and bonding strength of the insulating layer, prevent the insulating layer from cracking, peeling and other defects caused by excessive temperature, and refine the structure of the insulating layer, which is helpful to improve the quality of the insulating layer. Among them, the cooling rate is 200~500℃ / min. If the cooling rate is too low, the excessive temperature will affect the bonding strength between the insulating layer and the substrate, causing the insulating layer to peel off; if the cooling rate is too fast, the insulating layer and the substrate will be damaged due to excessive thermal stress.

[0060] In addition, the main purpose of using plasma spraying technology to spray ceramics on alloy wires is to improve the wear resistance, corrosion resistance and high temperature resistance of the alloy wires, where "high temperature resistance" refers to the ability of the alloy material to resist deformation of the workpiece under special working environments, such as high temperature and high-intensity working conditions. The purpose of spraying the ceramic layer in the present invention is to ensure the insulation effect under low temperature working conditions after high-temperature phase heat treatment, and the main function is still insulation.

[0061] The embodiments described above are part of the embodiments of the present invention, but not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A method for preparing a superconducting wire, comprising: The invention discloses a method for preparing an insulating layer on the surface of a superconducting wire, which is characterized by comprising: adopting a plasma spraying process to spray an insulating material on the surface of the superconducting wire to prepare a superconducting wire containing an insulating layer.

2. The preparation method according to claim 1, characterized in that: The superconducting element is Nb3Sn; the preparation method of Nb3Sn is any one of the internal tin method and the bronze method.

3. The preparation method according to claim 1, characterized in that: The insulating material is a mixture of any one of aluminum oxide and 8YSZ, any one of silicon nitride and aluminum nitride, and any one of polyimide, polyetheretherketone, and aramid fiber; The particle size of the mixture is 5-100 μm.

4. The preparation method according to claim 1, characterized in that: Before preparing the insulating layer on the superconducting base wire, the surface of the superconducting base wire needs to be polished and cleaned.

5. The preparation method according to claim 1, characterized in that: The plasma gas used in the plasma spraying is any one of argon, helium, nitrogen and hydrogen, or a mixture of the two, or a mixture of any one of the three and hydrogen.

6. The preparation method according to claim 5, characterized in that: The flow rate of the plasma gas is 10-60 L / min; The power of the plasma gas is 10-120 kW; The purity of the plasma gas is 99.99% or above.

7. The preparation method according to claim 1, characterized in that: When the plasma spraying process is used for spraying, the distance between the spray gun and the superconducting base line is 10-150 mm; The spraying method is 360° rotary spraying, and the rotation speed of the spray gun is 100~500rpm; The rotation method is forward-reverse alternating spraying.

8. The preparation method according to claim 1, characterized in that: When the plasma spraying process is used for spraying, the line speed of the superconducting baseline is 5-30 m / min; The powder feeding rate is 5~30g / min.

9. The preparation method according to claim 1, characterized in that: After the plasma spraying is completed, the superconducting wire is subjected to water cooling or air cooling.

10. A superconducting wire, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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