Method for optimizing critical current after heating of nanostitch tape and tape structure

Abstract

The application provides a method for optimizing critical current of nano-pinning tape after heating and a tape structure, comprising: arranging a sealing layer for sealing oxygen loss channels outside a superconducting layer with nano-pinning; and / or performing annealing treatment on the tape with the superconducting layer after a deposition process of the superconducting layer is completed, so as to reduce oxygen loss channels of the superconducting layer. By sealing some holes and oxygen loss channels of the nano-pinning, oxygen loss of the tape is reduced, so that Ic attenuation effect after heating is reduced. By using the annealing treatment before a silver evaporation process for preparing the superconducting tape, amorphous regions and partial defect regions of the superconducting layer can be self-repaired or grown, oxygen loss of the whole system is reduced, and Ic thermal attenuation effect of the tape at 200 DEG C is greatly reduced. Adaptability and use performance of the tape to an actual application environment can be effectively improved, the tape has more stable performance, stronger environmental adaptability in working conditions, and better use requirements of actual application scenes are met.

Description

Technical Field

[0001] This invention belongs to the field of superconducting tape processing technology, specifically, it relates to a method for optimizing the critical current after heating of nano-pinned tape and the tape structure. Background Technology

[0002] Second-generation superconducting tapes using REBCO (Re being a rare earth element) as the material, also known as coated conductors, have broader and better application prospects in many fields such as medicine, military, and energy due to their stronger current-carrying capacity, higher magnetic field performance, and lower material cost compared to bismuth-based tapes. Because the REBCO core, which serves as the superconducting current-carrying core, is inherently hard and brittle, second-generation high-temperature superconducting tapes are generally produced using a multi-layer coating process on a nickel-based alloy substrate, hence the name coated conductors. They typically consist of a base tape, a buffer layer (transition layer), a superconducting layer, and a protective layer.

[0003] The metal substrate provides excellent mechanical properties for the strip. The transition layer serves two purposes: firstly, it prevents inter-element diffusion between the superconducting layer and the metal substrate; secondly, the topmost transition layer provides a good template for the epitaxial growth of the superconducting layer, improving grain alignment quality. To fabricate a coated conductor with excellent superconducting properties, the superconducting layer needs a consistent biaxial texture. Biaxial texture refers to a nearly uniform grain arrangement along both the a / b axis and the c axis (the c axis is perpendicular to the a / b plane).

[0004] Achieving a high degree of alignment (in-plane texture) in YBCO thin films along the a / b axes is relatively difficult, and poor in-plane texture can severely degrade superconducting performance. Therefore, it is necessary to epitaxially grow YBCO superconducting thin films on transition layers that already possess biaxial texture and matched lattices. There are two main technical routes for fabricating biaxial textures: one is roll-assisted biaxial texture substrate technology, and the other is ion beam assisted deposition technology.

[0005] There are several common techniques for fabricating REBCO superconducting layers, including pulsed laser deposition, metal-organic chemical vapor deposition, and reactive co-evaporation. The protective layer primarily protects the superconducting film and is typically deposited as a silver layer on both sides of the superconducting tape using magnetron sputtering or vapor deposition. The tape is then annealed in an oxygen environment. Depending on the specific application's width requirements, 10-12 mm tapes are cut into 2-8 mm pieces. Finally, copper plating or subsequent encapsulation reinforcement treatments are performed.

[0006] Currently, when using superconducting tapes with nanopinning, the Ic (critical current) of the superconducting tape decreases after heating, which urgently needs to be optimized. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for optimizing the critical current after heating of nano-stapled tape and the tape structure.

[0008] A method for optimizing the critical current of a nano-pinned tape after heating, according to the present invention, includes: setting a sealing layer for sealing oxygen loss channels on the outside of a superconducting layer having nano-pinnings; And / or, in the fabrication of superconducting layers with nanopinning, a fabrication process that reduces oxygen loss channels in the superconducting layer is employed.

[0009] Preferably, the sealing layer comprises a pure element layer.

[0010] Preferably, in the PLD process, a layer of doped superconducting layer is first deposited, and then a layer of pure element superconducting layer is deposited on top of that.

[0011] Preferably, after electrochemical polishing of the Hastelloy substrate, Al2O3 and Y2O3 films are sequentially magnetron sputtered, followed by ion beam-assisted deposition of MgO film; LaMnO3 film is magnetron sputtered; CeO2 is deposited by pulsed laser, or MgO film is magnetron sputtered, followed by LaMnO3 film; then a 3-7% BMO (BHO, BSO, BZO) doped ReBCO superconducting layer is deposited, and a pure elemental ReBCO superconducting layer is deposited on this basis, followed by magnetron sputtering of a silver layer and oxygen annealing.

[0012] Preferably, after the silver strip is cut, the cut strip is then side-mounted with silver.

[0013] Preferably, a copper-rich target is used to deposit the superconducting layer.

[0014] Preferably, PLD roller coating is used, with low roller speed and low strip pass rate.

[0015] Preferably, the speed of the roller is not higher than 50 m / h, and the number of strip passes is not higher than 10.

[0016] Preferably, after the superconducting layer deposition process is completed, the strip with the superconducting layer is annealed in a flowing N2 annealing atmosphere at a temperature of 650°C to 750°C.

[0017] Preferably, when annealing the strip with the superconducting layer: the temperature is raised to 700 degrees Celsius in 2 hours and then held for 10 minutes.

[0018] Preferably, after electrochemical polishing of the Hastelloy-based strip, Al2O3 and Y2O3 films are sequentially magnetron sputtered, followed by ion beam-assisted deposition of MgO film and magnetron sputtering of LaMnO3 film; CeO2 is deposited by pulsed laser, and then two layers of 3-7% BMO (BHO, BSO, BZO) doped ReBCO superconducting layer are deposited. In this process, the strip is placed in an annealing furnace with flowing nitrogen gas. The temperature is first increased to the target holding temperature in a programmed manner over 2 hours, and then held for 10 minutes. After the furnace cools naturally to 300°C, the furnace door is opened to take a sample, and then the strip is magnetron sputtered to evaporate a silver layer.

[0019] Preferably, the oxygen loss channels of the superconducting layer include amorphous interstitial spaces and columnar defect regions.

[0020] According to the present invention, a strip structure includes an element-doped superconducting layer and a pure element superconducting layer, wherein the pure element superconducting layer is disposed outside the element-doped superconducting layer.

[0021] According to a strip structure provided by the present invention, the side of the slit strip includes a supplementary silver layer.

[0022] The present invention provides a strip structure comprising an annealed superconducting layer.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes flowing N2 annealing before the silver evaporation process in the preparation of superconducting tapes. This allows the amorphous regions and some defective regions of the superconducting layer to self-repair or grow, reducing oxygen loss in the entire system. Consequently, it significantly reduces the Ic thermal decay effect of the tape at 200℃. This effectively improves the tape's adaptability and performance in practical application environments, enabling it to exhibit more stable performance and stronger environmental adaptability under operating conditions, thus better meeting the requirements of practical application scenarios.

[0024] 2. This invention designs a pure element layer without pinning on the outermost superconducting layer, which seals some voids and oxygen loss channels of the nano-pinning, reduces oxygen loss in the tape, and thus reduces the Ic decay effect after heating. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a strip structure in which a sealing layer is set on the outside of the superconducting layer, which is the main feature of this invention; Figure 2 This is a schematic diagram illustrating the main features of the invention: the superconducting layer is not annealed. Figure 3 This is a schematic diagram illustrating the superconducting layer after annealing, which is the main feature of this invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] Example 1 like Figures 1 to 3 As shown, a method for optimizing the critical current of nano-stapled tape after heating according to the present invention includes: setting a sealing layer for sealing oxygen loss channels on the outside of a superconducting layer with nano-staples; And / or, in the fabrication of superconducting layers with nanopinning, a fabrication process that reduces oxygen loss channels in the superconducting layer is employed.

[0028] The technical solution of this application has conducted extensive analysis on the attenuation of the critical current after heating the nano-pinned tape. The first step is to determine what factors affect the attenuation of the critical current after heating the nano-pinned tape. The second step is to provide an optimization scheme based on the factors affecting the attenuation of the critical current after heating the nano-pinned tape. The third step is to verify the optimization scheme and further optimize it.

[0029] This application optimizes the attenuation of the critical current after heating of nano-pinned tapes through the design of standardized experiments. The specific experiments are as follows: The standardized experimental equipment is a box-type annealing furnace without atmosphere (cleanroom atmospheric environment); the standardized experimental parameters are to hold at 200℃ for 150 minutes and then cool to room temperature with the furnace (the annealing furnace heating process is to heat to 190℃ in 30 minutes, heat to 210℃ in 20 minutes, cool down to 200℃ in 5 minutes, and then enter the set holding time process); the standardized experimental strip is placed on a copper plate with 4 thermocouples for temperature monitoring.

[0030] S1; Cut the 4mm copper-plated strip to a suitable length, perform a four-lead test using a fixture, and mark the voltage lead criterion positions to ensure consistency of the criterion before and after heating. Test current flow rate: 200mA / s, quench criterion: 1μV / cm.

[0031] S2: After removing the solder joints, a heating experiment was conducted in a cleanroom and atmospheric environment using a box-type annealing furnace. The strip was placed on an empty copper plate. The experimental parameters were set to hold at 200℃ for 150 minutes, then cool to room temperature with the furnace. The annealing furnace heating process was as follows: heat to 190℃ in 30 minutes, heat to 210℃ in 20 minutes, cool to 200℃ in 5 minutes, and then proceed to the set holding time.

[0032] S3: After heat treatment, the strip is subjected to a four-lead test using a fixture, according to the previous voltage lead criteria. The test current rate is 200mA / s, and the quench criterion is 1μV / cm.

[0033] S4: Calculate and analyze the Ic attenuation rate before and after strip heating.

[0034] The Ic decay after heating the tape is due to oxygen escaping from the oxygen loss channels after the superconducting layer is heated and held at a certain temperature, thus affecting the electrical properties of the REBCO superconducting tape. These oxygen loss channels may be provided by crystal and amorphous interstitial defects in the superconducting layer, as well as columnar pinning. To fill or seal these oxygen loss channels, this invention provides the following optimization scheme to reduce the Ic decay effect after heating the tape and further improve the tape's performance. Furthermore, the oxygen loss channels in the superconducting layer include amorphous interstitial and columnar defect regions.

[0035] The first feasible method for optimizing the critical current after heating of nano-pinned tapes is as follows: a sealing layer for sealing oxygen loss channels is set outside the superconducting layer with nano-pinning. The sealing layer includes a pure element layer. In the PLD process, a doped element superconducting layer is first deposited, and then a pure element superconducting layer is deposited on top of it. In a specific embodiment, after electrochemical polishing of the Hastelloy substrate tape, Al2O3 and Y2O3 films are sequentially magnetron sputtered, followed by ion beam-assisted deposition of MgO film; LaMnO3 film is magnetron sputtered; CeO2 is deposited by pulsed laser, or MgO film is magnetron sputtered, followed by LaMnO3 film; then a 3-7% BMO (BHO, BSO, BZO) doped ReBCO superconducting layer is deposited, and then a pure element ReBCO superconducting layer is deposited on top of it, followed by magnetron sputtering of a silver layer and oxygen annealing.

[0036] The above optimization method was applied to the strip heating attenuation experiment: First, 4mm silver strip and copper-plated strip from the experimental group were tested with four leads. The test current rate was 200mA / s, and the quench criterion was 1μV / cm. Indium was soldered on both sides and a fixture was used for testing. The fixture position was marked to ensure that the voltage lead criterion was consistent before and after heating, thus preventing the detection of low or high current points. After the test, the solder joints were cut off, and it was ensured that there was no other contamination in the cavity during heating. The strip was then placed empty on a copper plate and heated using a box-type annealing furnace. The experimental parameters were as follows: heat treatment at 200℃ for 150 min, followed by furnace cooling to room temperature (the annealing furnace heating process was 30 min to 190℃, 20 min to 210℃, 5 min to 200℃, and then entering the set holding time process); the temperature of the copper plate and the cavity was monitored by a temperature monitoring instrument. Timing was started for 150 min when the lowest temperature thermocouple on the copper plate reached 195℃. After the holding time was completed, the heating was turned off, and the strip was allowed to cool naturally to room temperature with the cavity. After sampling, it was sent to the test IC.

[0037] The core of this experiment lies in the following: First, a layer of 3-7% BMO (BHO, BSO, BZO) is deposited in the PLD process. Then, a second layer of pure elemental ReBCO is deposited under different oxygen partial pressures (700, 800, 900 mTorr), and heating experiments are conducted on the strip. The aim is to investigate whether a pure elemental (pure elemental ReBCO) layer designed as the outermost superconducting layer can seal some of the voids and oxygen loss channels of the ReBCO + 3-7% BMO (BHO, BSO, BZO) layer, thereby reducing oxygen loss in the strip and thus reducing the Ic decay effect after heating.

[0038] Experimental results: The attenuation rates of all strips under different oxygen partial pressures (700, 800, 900 mTorr) tend to be consistent, indicating that the oxygen partial pressure has little effect on the strips in this embodiment. The average attenuation rate of the silver strip after the heating experiment is about 4%, and the average attenuation rate of the copper-plated strip is about 5%.

[0039] Experimental results show that the above optimization method can effectively seal the oxygen loss channels of the strip, thereby reducing the oxygen loss of the strip after heating, and thus reducing the Ic decay effect after heating.

[0040] A second feasible method for optimizing the critical current after heating of nano-pinned tapes is as follows: After the superconducting layer deposition process, the tape with the superconducting layer is annealed to reduce oxygen loss channels in the superconducting layer. After the superconducting layer deposition process, the tape with the superconducting layer is annealed at a temperature of 650°C to 750°C in a flowing N2 annealing atmosphere. During the annealing of the tape with the superconducting layer: the temperature is raised to 700°C over 2 hours, and then held for 10 minutes. In one feasible implementation, after electrochemical polishing of the Hastelloy-based strip, Al2O3 and Y2O3 films are sequentially magnetron sputtered, followed by ion beam-assisted deposition of MgO film and magnetron sputtering of LaMnO3 film; CeO2 is deposited by pulsed laser, and then two layers of 3-7% BMO (BHO, BSO, BZO) doped ReBCO superconducting layer are deposited. In this process, the strip is placed in an annealing furnace with flowing nitrogen gas, and the temperature is first increased to the target holding temperature in a programmed manner over 2 hours. After holding for 10 minutes, the furnace door is opened to take a sample when the furnace cools naturally to 300°C. Then, the strip is magnetron sputtered to evaporate a silver layer.

[0041] Because the entire superconducting layer system contains crystalline, amorphous interstitial, and columnar defect regions, oxygen loss or transport is relatively easy or fast in the amorphous and defective regions. Annealing at 650℃-750℃ in a flowing N2 annealing atmosphere allows the amorphous and some defective regions to self-repair or grow, forming crystalline regions, thereby reducing oxygen loss from the entire system.

[0042] The core scheme is as follows: Take a 12mm superconducting layer black strip produced in the same furnace of the PLD equipment, perform a normal silver evaporation process on a section, and retain the remaining black strip as a sample. Simultaneously, perform flowing N2 annealing on both the silver-evaporated strip and the black strip. The annealing process involves heating to 650℃, 700℃, and 750℃ over 2 hours, holding for 10 minutes, with the holding temperature as the experimental variable. After flowing N2 treatment, the black strip undergoes the subsequent silver evaporation process, followed by annealing of all strips. After annealing, all strips are cut to 4mm, and a single-cut silver strip from one side is used for 5μm copper plating. It should be noted that the black strip refers to the strip with only the superconducting layer.

[0043] The above optimization method was applied to the strip heating attenuation experiment: First, 4mm silver strips and copper-plated strips corresponding to different variables were tested with four leads. The test current rate was 200mA / s, and the quench criterion was 1μV / cm. Indium was soldered on both sides and a fixture was used for testing. The fixture position was marked to ensure that the voltage lead criterion was consistent before and after heating, thus preventing the detection of low or high current points. After the test, the solder joints were cut off, and it was ensured that there was no other contamination in the cavity during heating. The strip was then placed empty on a copper plate and heated using a box-type annealing furnace. The standardized experimental parameters are: holding at 200℃ for 150 min and then cooling to room temperature in the furnace (the annealing furnace heating process is: heating to 190℃ in 30 min, heating to 210℃ in 20 min, cooling to 200℃ in 5 min, and then entering the set holding time process); the temperature of the copper plate and the cavity is monitored by a temperature monitoring instrument. When the lowest temperature thermocouple on the copper plate reaches 195℃, the timer starts for 150 min. After the holding time is completed, the heating is turned off, and the strip is allowed to cool naturally to room temperature in the cavity. After sampling, it is sent to the test IC.

[0044] Experimental results: The decay rate of all black ribbons after N2 annealing was reduced compared to that of the control group silver ribbons. The Ic decay rate of the control group silver ribbons was about 15% at different annealing temperatures (650℃, 700℃, 750℃), while the Ic decay rate of the black ribbons decreased with increasing annealing temperature at different annealing temperatures (650℃, 700℃, 750℃), with the lowest decay rate of about 3% at 700℃.

[0045] Experimental results show that before the silver evaporation process for preparing superconducting tapes, using flowing N2 annealing (heating to 700℃ for 2 hours and holding for 10 minutes) can allow the amorphous regions and some defective regions of the superconducting layer to self-repair or grow, reducing oxygen loss in the entire system and thus significantly reducing the Ic thermal decay effect of the tape at 200℃.

[0046] The applicant should note that both the first and second feasible optimization methods described above can effectively optimize the critical current decay of the nano-stapled tape after heating. This embodiment also includes technical solutions that simultaneously employ both optimization methods.

[0047] According to a strip structure provided by the present invention, based on a first optimization method, it includes an element-doped superconducting layer and a pure element superconducting layer, wherein the pure element superconducting layer is disposed outside the element-doped superconducting layer.

[0048] According to a strip structure provided by the present invention, and based on a second optimization method, it includes an annealed superconducting layer.

[0049] Comparative Example 1 Based on Example 1, a method for optimizing the critical current after heating of nano-stapled tape according to the present invention is used to conduct heating experiments based on commercially available nano-stapled tape.

[0050] The core scheme is as follows: Mass-produced strip is extracted, slit into 4mm silver strips, and then plated with 5μm copper. The silver strips and copper-plated strips are then used for heating experiments. This comparative example aims to study the Ic decay of the strips after heating.

[0051] When applying this scheme to the strip heating attenuation test, firstly, take 4mm silver strip and copper-plated strip from the corresponding experimental group for four-lead testing. The test current rate is 200mA / s, and the quench criterion is 1μV / cm. Indium is soldered on both sides and a fixture is used for testing. The fixture position is marked to ensure that the voltage lead criterion is consistent before and after heating, thus preventing the measurement of low or high current points. After the test, the solder joint is cut off, ensuring that there is no other contamination in the cavity during heating. The strip is then placed empty on the copper plate and heated using a box-type annealing furnace. The experimental parameters were as follows: heat treatment at 200℃ for 150 min, followed by furnace cooling to room temperature (the annealing furnace heating process was 30 min to 190℃, 20 min to 210℃, 5 min to 200℃, and then entering the set holding time process); the temperature of the copper plate and the cavity was monitored by a temperature monitoring instrument. Timing was started for 150 min when the lowest temperature thermocouple on the copper plate reached 195℃. After the holding time was completed, the heating was turned off, and the strip was allowed to cool naturally to room temperature with the cavity. After sampling, it was sent to the test IC.

[0052] After the above scheme was implemented, the Ic decay rate of all experimental strips after heating was about 11 to 15%. The difference in the decay rate of the strips may be related to the number and distribution of voids or defects in the superconducting layer of the nano-pinned strips.

[0053] Comparative Example 2 Based on Example 1 and Comparative Example 1, this invention provides a method for optimizing the critical current after heating of nano-pinned tapes, focusing on the influence of the number and distribution of voids in the superconducting layer of the nano-pinned tape on the attenuation of Ic after heating. In Comparative Example 1, the attenuation rates of mass-produced nano-pinned tapes differ, which may be related to the distribution and number of voids in the superconducting layer of the tape.

[0054] The core approach is to select tapes with few or no voids on their optical and SEM surfaces as the experimental group. This comparative example aims to investigate whether voids in the superconducting layer of the tape are one of the channels for oxygen loss during heating.

[0055] When applying this scheme to the strip heating attenuation test, firstly, 4mm silver strip and copper-plated strip from the experimental group were used for four-lead testing. The test current rate was 200mA / s, and the quench criterion was 1μV / cm. Indium was soldered on both sides and a fixture was used for testing. The fixture position was marked to ensure that the voltage lead criterion was consistent before and after heating, thus preventing the measurement of low or high current points. After the test, the solder joints were cut off, ensuring that there was no other contamination in the cavity during heating. The strip was then placed empty on a copper plate and heated using a box-type annealing furnace, and the process was standardized. The experimental parameters were as follows: heat treatment at 200℃ for 150 min, followed by furnace cooling to room temperature (the annealing furnace heating process was 30 min to 190℃, 20 min to 210℃, 5 min to 200℃, and then entering the set heat treatment time process); the temperature of the copper plate and the cavity was monitored by a temperature monitoring instrument. Timing was started for 150 min when the lowest temperature thermocouple on the copper plate reached 195℃. After the heat treatment time was completed, the heating was turned off, and the strip was allowed to cool naturally to room temperature with the cavity. After sampling, it was sent to the test IC.

[0056] After the above scheme was implemented, the Ic decay rate of all experimental tapes after heating was 9% to 11%, which is an improvement compared with the randomly sampled nano-pinned tapes. This indicates that the voids on the surface of the superconducting layer of the tape after heating are channels for oxygen loss, and reducing the number and distribution of voids can effectively improve the Ic decay effect after the tape is heated.

[0057] Comparative Example 3 Based on Example 1, Comparative Example 1, and Comparative Example 2, this invention provides a method for optimizing the critical current after heating nano-pinned tapes, based on the study of the Ic attenuation effect after heating voidless superconducting tapes. Pinning in the superconducting layer is a channel for oxygen loss after tape heating, combined with Comparative Example 1 and Comparative Example 2.

[0058] The core solution of this embodiment is: Unpinned pure elemental tape (pure elemental ReBCO tape) was selected as the experimental group, while ReBCO doped with certain amounts of Eu₂O₃, BZO, BSO, and BHO served as the control group. The comparative study aimed to investigate whether the reduction in oxygen loss channels in the unpinned tape improved the oxygen loss effect upon heating.

[0059] When applying this scheme to the strip heating attenuation test, firstly, 4mm silver strip and copper-plated strip from the experimental group were used for four-lead testing. The test current rate was 200mA / s, and the quench criterion was 1μV / cm. Indium was soldered on both sides and a fixture was used for testing. The fixture position was marked to ensure that the voltage lead criterion was consistent before and after heating, thus preventing the measurement of low or high current points. After the test, the solder joints were cut off, ensuring that there was no other contamination in the cavity during heating. The strip was then placed empty on a copper plate and heated using a box-type annealing furnace, and the process was standardized. The experimental parameters were as follows: heat treatment at 200℃ for 150 min, followed by furnace cooling to room temperature (the annealing furnace heating process was 30 min to 190℃, 20 min to 210℃, 5 min to 200℃, and then entering the set heat treatment time process); the temperature of the copper plate and the cavity was monitored by a temperature monitoring instrument. Timing was started for 150 min when the lowest temperature thermocouple on the copper plate reached 195℃. After the heat treatment time was completed, the heating was turned off, and the strip was allowed to cool naturally to room temperature with the cavity. After sampling, it was sent to the test IC.

[0060] After implementing the above scheme, the control group (ReBCO doped with a certain amount of Eu2O3, BZO, BSO, and BHO) showed different degrees of Ic decay after heating. The Ic decay rates of the silver strip were 11%, 8%, 13%, and 9%, respectively, while those of the copper-plated strip were 23%, 10%, 26%, and 15%, respectively. As the experimental group, the unpinned pure element strip (pure element ReBCO strip) was used to select multiple samples. The average decay rate of the silver strip was 2%, and the average decay rate of the copper-plated strip was 3%.

[0061] This comparative example shows that the oxygen loss of the strip after heating is mainly due to pinning in the superconducting layer as the oxygen loss channel. The more pinning and voids there are, the more severe the oxygen loss of the strip after heating, which in turn leads to a significant decrease in Ic.

[0062] Example of variation 1 Based on Example 1, according to the present invention, a method for optimizing the critical current after heating of a nano-pinned tape is provided. In the preparation process of a superconducting layer with nano-pinning, a preparation process that reduces oxygen loss channels in the superconducting layer is adopted, including: after slicing the silver tape, side-filling silver onto the sliced ​​tape. The resulting tape structure has a supplementary silver layer on the sides of the sliced ​​tape.

[0063] This example illustrates the treatment of the cut edges after precision or laser slitting of a 12mm silver strip. Depending on the specific application, the 12mm silver strip needs to be slid to a width of 4mm in the subsequent copper plating process. After slitting, the strip has cut edges, which are channels for oxygen loss after heating the superconducting strip. Therefore, side silver filling is used to fill these oxygen loss channels, reducing the Ic decay effect caused by oxygen loss after heating the strip.

[0064] Variation Example 2 Based on Example 1, according to the present invention, a method for optimizing the critical current after heating of nano-pinned tapes is provided. In the preparation process of a superconducting layer with nano-pinning, a preparation process that reduces oxygen loss channels in the superconducting layer is adopted, including: using a copper-rich target to deposit the superconducting layer. Specifically, a target with a Cu content ratio of 3.2 is prepared, and the superconducting layer is deposited using a conventional mass production process. The copper richness allows the liquid phase to fill voids and defects in the tape, thereby reducing oxygen loss channels and minimizing the Ic decay effect after heating.

[0065] Example of variation 3 Based on Example 1, this invention provides a method for optimizing the critical current after heating nano-pinned tape. In the preparation of a superconducting layer with nano-pinning, a preparation process that reduces oxygen loss channels in the superconducting layer is employed, including: using a PLD roller coating process with low roller speed and low tape pass count. The roller speed is no higher than 50 m / h, and the tape pass count is no higher than 10 passes. The aim is to slow down the crystallization process of the superconducting layer, resulting in fewer surface defects and voids.

[0066] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0067] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for optimizing the critical current after heating of nano-stapled tape, characterized in that, The method includes at least one of the following technical solutions: Option 1: A sealing layer for sealing oxygen loss channels is provided outside the superconducting layer with nano-pinning, the sealing layer comprising a pure elemental ReBCO superconducting layer without nano-pinning; Option 2: After the deposition of the superconducting layer with nanopins is completed, before the deposition of the protective silver layer, the tape with the superconducting layer is annealed at a temperature of 650℃ to 750℃ in a flowing N2 annealing atmosphere. During the annealing of the tape with the superconducting layer: the temperature is raised to 700℃ in 2 hours and then held for 10 minutes.

2. The method for optimizing the critical current after heating of nano-stapled tape according to claim 1, characterized in that, For Option 1, in the PLD process, a superconducting layer with nanopinning is first deposited, and then a superconducting layer without nanopinning is deposited on top of that.

3. The method for optimizing the critical current after heating of nano-stapled tape according to claim 1, characterized in that, For Option 1, after electrochemical polishing of the Hastelloy substrate, Al2O3 and Y2O3 films are sequentially magnetron sputtered. The subsequent buffer layer is then formed using either step A or step B: Step A: Ion beam-assisted deposition of MgO film, magnetron sputtering of LaMnO3 film, and pulsed laser deposition of CeO2; Step B: Magnetron sputtering of MgO film, magnetron sputtering of LaMnO3 film, pulsed laser deposition of CeO2; then deposition of a 3-7% BMO, BHO, BSO or BZO doped ReBCO superconducting layer, followed by deposition of a pure element ReBCO superconducting layer, then magnetron sputtering of a silver layer and oxygen annealing.

4. The method for optimizing the critical current after heating of nano-stapled tape according to claim 1, characterized in that, In the fabrication process of the superconducting layer with nanopinning, a fabrication process that reduces oxygen loss channels in the superconducting layer is adopted, using PLD roller coating with low roller speed and low strip pass rate. And / or, when depositing the superconducting layer, a copper-rich target is used to deposit the superconducting layer.

5. The method for optimizing the critical current after heating of nano-stapled tape according to claim 4, characterized in that, The speed of the rollers shall not exceed 50 m / h, and the number of strip passes shall not exceed 10.

6. The method for optimizing the critical current after heating of nano-stapled tape according to claim 1, characterized in that, For Scheme 2, after electrochemical polishing of the Hastelloy base strip, Al2O3 and Y2O3 films are sequentially magnetron sputtered, followed by ion beam-assisted deposition of MgO film and magnetron sputtering of LaMnO3 film; CeO2 is deposited by pulsed laser, and then two layers of 3-7% BMO, BHO, BSO or BZO-doped ReBCO superconducting layer are deposited. In this process, the strip is placed in an annealing furnace with flowing nitrogen gas. The temperature is first programmed to rise to the target holding temperature in 2 hours, and after holding for 10 minutes, the furnace door is opened to take samples when the furnace cools naturally to 300°C. Then, the strip is magnetron sputtered to evaporate silver layer.

7. A strip structure, characterized in that, The material is processed using the critical current optimization method for heating nano-pinned tape as described in any one of claims 1 to 3. For Scheme 1, it includes an element-doped superconducting layer and a superconducting layer without nano-pinning, wherein the superconducting layer without nano-pinning is disposed outside the element-doped superconducting layer.

8. A strip structure, characterized in that, The material is processed using the critical current optimization method for heating nano-stapled tape as described in claim 1. For scheme two, after the tape is slit, silver is applied to the sides of the slit tape, and the sides of the slit tape include a supplementary silver layer.

Images