How to 3D print superconducting strands of yttrium barium copper oxide

Abstract

This invention discloses a method for fabricating high-temperature superconducting wires made of yttrium barium copper oxide (YBCO) by 3D printing, which can be divided into four steps: first, preparing a nanoscale superconducting powder precursor; second, formulating a printing paste with appropriate viscosity and support properties; then, using CAD 3D modeling, exporting model data in STL format, slicing using specialized software; and twisting the print head to achieve one-step fabrication of stranded wires with low current loss. Finally, the printed stranded wires are formed into practical superconducting stranded wire cables through processes such as deplasticization, phase formation, oxygen replenishment, and packaging. This invention makes it possible for the first time to apply advanced direct-write 3D printing technology to high-temperature superconducting wires. Fabricating micro-nanoscale superconducting core wires by 3D printing enables a core thinning process and enables integrated design of materials and structures. This invention simplifies the fabrication process of high-temperature superconducting wires, improving the current-carrying performance and production efficiency of high-temperature superconducting wires and reducing production costs.

Description

[Technical field]

[0001] The present invention belongs to the technical field of producing superconducting strands, in particular yttrium barium copper oxide by 3D printing. (YBa 2 Cu 3 O 7 ) The present invention relates to a method for producing a superconducting stranded wire. [Background technology]

[0002] Superconducting materials are one of the few metamaterials in nature that have unique properties such as zero resistance, perfect diamagnetism and Joseph effect. Superconducting materials are expected to have a wide range of applications in many fields such as national defense, energy, transportation and communication, and have great prospects for use in superconducting current limiters, superconducting generators, superconducting filters, superconducting energy storage and other superconducting power and magnets. Here, superconducting wire is the main current-carrying unit for superconducting applications.

[0003] Currently, the main types of high-temperature superconducting tape wires in use are first-generation high-temperature superconducting conductors, mainly represented by Bi-based conductors, and high-temperature superconducting conductors, mainly represented by REBCO (RE stands for rare earth elements). The current carrying capacity of a single high-temperature superconducting tape wire is limited by the critical current, and in practical applications, multiple superconducting tape wires must be connected in parallel to obtain a high current carrying capacity. However, when wires are used in parallel, the proximity effect and skin effect occur under the action of AC, which causes AC loss, affecting the safety and stability of the superconducting cable in use, and increasing the risk of use and running costs. Currently, there are a series of solutions to this problem, such as changing the crystal structure, expanding the pitch of the superconducting core wire, twisting and dislocation of the superconducting core wire, and thinning the superconducting core wire. In recent years, superconducting tape wires have made great progress. The Karlsruhe Research Center in Germany designed a RACC cable with a periodic trapezoidal distribution along the length, the National Institute of Standards and Technology in the United States proposed to form a compact CORC conductor cable by spirally winding high-temperature superconducting tape material around a central skeleton, and the Massachusetts Institute of Technology proposed a TSTC cable conductor based on stacking and twisting superconducting tape material. At the same time, the technically mature CICC conductor and Rutherford flat cable are also cable conductors with the most basic form of twisting, so it can be said that twisted cables are the most common and mature technology for superconducting cables. However, the core wires for making superconducting cables are mainly Bi-based wires by the powder-in-tube method and filaments cut from YBCO tape material, and the twisting process is not only cumbersome and complicated, but also prone to cracks and breakage, making the current-carrying performance of superconducting cables unstable and reducing their mechanical properties.

[0004] Direct-write 3D printing technology is a new manufacturing process that does not require a mold, but rather extrudes micro- and nano-scale filaments and stacks them layer by layer to rapidly mold ceramic structures and devices with various complex shapes, shortening the production cycle of the product. Therefore, 3D printing-based technology makes it possible to fabricate micron and even nano-scale filaments and twist them together, providing ideas for improving the critical current and mechanical properties of superconducting wires. However, there is currently no relevant research on 3D printing technology for high-temperature superconducting wires. The present invention proposes a fast and accurate method for fabricating twisted wires based on 3D printing technology. Summary of the Invention

[0005] In order to solve the above technical problems in the prior art and the field, the present invention provides Follow these steps: 1) Preparation of superconducting powder precursor: The main raw material for printing is YBCO superconducting material or mixed powder that can be sintered to form the superconducting phase, which can be mechanically crushed. Crushed Thus, print powder with a particle size of 100-300 nm is obtained; 2) Print paste formulation: Add ground superconducting powder precursor to a mixture of appropriate proportions of polymer binder and lubricant to form a direct-write print paste. 3D Printing Form a paste; 3 )straight Printing of stranded wires is made possible by a direct-write 3D printer. ; Processing The processed model slice data is input to the computer numerical control side, and the computer transmits a digital signal to the communication board, and the communication board synchronously issues the ink supply communication command and the print drive command; after the ink supply communication command is issued, the gas electromagnetic control valve opens, and the air pressure is applied to the push plug of the trough; and, Transmitting pressure to the print paste , forming uniform and smooth print lines from the printing system.After the print drive command is issued, the three servo motors control the three-way drive of the XYZ axis, and the X-axis and Y-axis slide rail drives accurately move and position the printer needle on the XY plane, and the Z-axis high-precision roller screw drive raises and lowers the bottom platform; at the same time, the print drive command is also transmitted to the servo motor that drives the rotation of the needle, making the needle rotate stably; the three filaments extruded by the needle are fixed on the Z-axis platform, and twisted in the XY plane by the integrated continuous rotation of the needle; at the same time, the filament of the needle is continuously stretched in the Z-axis direction, Bottom The filament is elongated by synchronously lowering the platform. Integrated Needle rotation, Bottom In conjunction with the descent of the platform, stranded wire is produced; needle diameter, extrusion pressure, Bottom Platform By adjusting the descent speed, rotation speed, etc., a strand of wire with the desired parameters is produced; 4) Plastic removal and superconducting phase formation treatment; 5) Including encapsulation assembly, A method for 3D printing superconducting strands of yttrium barium copper oxide is provided.

[0006] Preferably, the mixed powder capable of sintering to form the superconducting phase is copper oxide, yttrium oxide and barium carbonate.

[0007] Preferably, the polymer binder is polyethylene glycol (PVA), polyvinylpyrrolidone (PVP), polyvinylbutyral (PVB) or sodium carboxymethylcellulose (CMC), and the lubricant is of mineral or vegetable origin; the binder is mixed with the lubricant in an appropriate ratio.

[0008] Preferably, the pre-printing preparation work in step 3) above is First, inject an appropriate amount of printing paste into the printer needle integrated trough via the ink injection and pressure supply port, then place the press plug into the trough, and finally connect the pressure supply air tube to the ink injection and pressure supply port with a universal joint.

[0009] Preferably, the deplasticization and superconducting phase formation treatment in step 4) above is specifically carried out as follows: The printed strand is placed in a high-temperature furnace for heat treatment to remove polymers and impurities from the strand; the plastic removal conditions are a constant temperature of 500°C for 12-24 hours with a heating rate of 0.5-1°C / min; the phase formation treatment conditions are sintering in an oxygen atmosphere at 900-960°C for 20-30 hours with a heating rate of 1°C / min; and finally, the sintered sample is supplemented with oxygen for 30 hours under conditions of an oxygen partial pressure of 0.5-2MPa and a temperature of 500°C.

[0010] Preferably, the encapsulation assembly in step 5) above comprises: In order to meet the requirements for mechanical strength, electrical conductivity, safety and other aspects during use of superconducting wire, the metal copper sleeve is seal-welded by mature laser welding technology or electron beam; complex composite wires with different cross-sectional dimensions and shapes are realized.

[0011] The present invention is mainly divided into three-axis synchronization and the rotation of the integrated needle for the print drive. The ink supply communication command is controlled by the air pressure, which is mainly the doping amount, and different air pressures affect the ink ejection speed. or print line speed The ink ejection speed is measured and the needle rotation speed is adjusted to match the ink ejection speed. Bottom Platform By varying the descent rate and continuously adjusting the feedback, strands with different diameters, cutoffs, lengths and cores were obtained.

[0012] The integration of the rotating needle is key to printing stranded wire, with air pressure in the feed tube providing the power and control for the extrusion of the paste, while the drive shaft is powered by a servo motor. When a print program is started, paste is first evenly extruded from the printer needle through the feed tube, fixing the extruded line to the base plate. The drive shaft then Needle integration Drive the rotation and push out continuously. Bottom Platform The drop and twist of the needle affect the thickness of the needle, the extrusion pressure, Bottom Platform The descent speed and rotation speed are adjusted to form a stranded wire with the desired parameters. The present invention comprises the steps of: 1) Preparation of superconducting powder precursor: The main raw material of the print is YBCO superconducting material or mixed powder that can be sintered to form the superconducting phase; Mechanical grinding yields print powder with particle size of 100-300 nm; 2) Print paste composition: Add the ground superconducting powder precursor to a mixture of polymer binder and lubricant in the right ratio to form a direct-write 3D printing paste; 3) Bulk material structure printing: Vacuum-assisted evacuation of gases in the paste; The compounded print paste is then loaded into a print barrel and forced through the printer needle by air pressure or mechanical pressure; Applying computer modeling to design print paths for desired structures; Using direct-write 3D printing, replicate and fabricate the designed structure on the bottom plate of the stage by layer-by-layer deposition to form a wet sample; 4) Formation of powder compacts by freeze-drying: Place the printed wet sample in a low-temperature environment at -30 to -60 °C; Freeze-drying to eliminate ice crystals in the wet sample to form a powder compact; 5) Including plastic-free and superconducting phase formation treatments, A method for preparing 3D printed yttrium barium copper oxide bulk superconducting material is further provided. The mixed powder capable of sintering the above-mentioned superconducting phase is copper oxide, yttrium oxide and barium carbonate. Preferably, the polymer binder is polyethylene glycol (PVA), polyvinylpyrrolidone (PVP), polyvinylbutyral (PVB) or sodium carboxymethylcellulose (CMC), and the lubricant is of mineral or vegetable origin; the binder is mixed with the lubricant in an appropriate ratio. Preferably, the deplasticization and superconducting phase formation treatment in step 5) above is specifically The printed green compact is placed in a high-temperature furnace for heat treatment to remove polymers and impurities; the plastic removal conditions are a constant temperature of 500°C for 12-24 hours with a heating rate of 0.5-1°C / min; the phase formation treatment conditions are sintering in an oxygen atmosphere at 900-960°C for 20-30 hours with a heating rate of 1°C / min; finally, the sintered sample is oxidized for 30 hours under conditions of oxygen partial pressure of 0.5-2MPa and temperature of 500°C.

[0013] This invention makes it possible to apply the cutting-edge technology of direct-write 3D printing to high-temperature superconducting wire for the first time. The production of micro-nanoscale superconducting core wire by 3D printing has achieved the process of thinning the core wire, and by overcoming the difficulties that the production of high-temperature superconducting wire is limited by the molding die through modeling, slicing, twisting of printer needles, etc., it has made it possible to design the integrated material and structure. This invention simplifies the production process of high-temperature superconducting wire, reduces the difficulty of the phase formation treatment process and twisting, improves the current carrying performance and production efficiency of high-temperature superconducting wire, reduces production costs, and is suitable for promoting the large-scale practical application of superconducting wire, and has enormous scientific research and commercial value. [Brief description of the drawings]

[0014] Hereinafter, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments. [Figure 1] 1 is a principle diagram and a control flowchart of a twisted wire printing system. [Diagram 2] FIG. 1 is a top view of the printer needle integration. [Diagram 3] FIG. 13 is a left side view of the integrated printer needle. [Figure 4] FIG. 2 is a front view of the integrated printer needle. [Diagram 5] FIG. 1 is a perspective view of a printer needle integration. [Figure 6] 1 is a principle diagram and a control flowchart of a bulk material printing system. [Figure 7] Figure 1 shows the electromagnetic and structural properties of 3D printed YBCO bulk superconducting material. [Figure 8] FIG. 1 shows a wet sample of YBCO bulk superconducting material printed by a 3D printing based fabrication method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention discloses a method for fabricating superconducting strands of yttrium barium copper oxide by 3D printing.

[0016] Consider the following example: 1. The present invention discloses the preparation of superconducting powder precursor: the main raw material for printing is YBCO superconducting material or mixed powder ( for example, Copper oxide, yttrium oxide, barium carbonate Mixture of powder The main raw material for printing is mechanical powder. Crushed As a result, a print powder with a particle size of 100 to 300 nm is obtained. Here, the mechanical grinding may be performed by a different design, such as a ball mill.

[0017] 2. The present invention discloses a printing paste formulation: the polished superconducting powder precursor is added to a mixture of polymer binder and lubricant in the appropriate proportions to produce a direct-write type 3D Printing A paste is formed. The polymer binder used here may be polyethylene glycol (PVA), polyvinylpyrrolidone (PVP), polyvinylbutyral (PVB), sodium carboxymethylcellulose (CMC), etc., and the lubricant may be mineral or vegetable. The binder is mixed with the lubricant in an appropriate ratio.

[0018] 3. The present invention discloses the printing of stranded wire: the printing of stranded wire is realized by the improved direct-write 3D printer, and the printing flow is as shown in Figure 1.

[0019] Preparation work before printing: First, inject an appropriate amount of printing paste into the printer needle integrated trough through the ink injection and pressure supply port, then place the press plug into the trough, and finally connect the pressure supply air tube to the ink injection and pressure supply port with a universal joint. The structure of the needle integration is shown in Figures 2-5.

[0020] Print: After the processed model slice data is input to the computer numerical control side, the computer transmits a digital signal to the communication board, and the communication board issues the ink supply communication command and the print drive command synchronously. After the ink supply communication command is issued, , electric Magnetically controlled valve (For example, a gas solenoid control valve) The press plug is opened, and air pressure is loaded onto the press plug in the trough, and the press plug transmits the pressure to the print paste to form a pressurized paste, and the pressurized paste is uniformly extruded through the printer needle. After the print drive command is issued, three servo motors perform three-way control driving of the XYZ axes, the X and Y axis slide rail drives perform accurate movement and positioning of the printer needle on the XY plane, and the Z axis high-precision roller screw drive performs the lifting and lowering of the bottom platform. At the same time, the print drive command is also transmitted to the servo motor that drives the needle rotation, and the needle rotates stably. The three filaments extruded by the needle are fixed on the Z axis platform, and twisted together in the XY plane by the integrated continuous rotation of the needle. At the same time, the needle filament is continuously extended in the Z axis direction, Bottom The filament is elongated by synchronously lowering the platform. Integrated Needle rotation, Bottom The wire is stranded in conjunction with the descent of the platform. The needle diameter, extrusion pressure, Bottom Platform By adjusting the descent speed, rotation speed, etc., a stranded wire with the desired parameters can be produced.

[0021] 4. Plastic-free and superconducting phase formation treatment The printed strand is placed in a high-temperature furnace and heat-treated to remove polymers and impurities from the strand. The plastic removal conditions are a constant temperature of 500°C for 12-24 hours with a heating rate of 0.5-1°C / min. The phase formation treatment conditions are sintering in an oxygen atmosphere at 900-960°C for 20-30 hours with a heating rate of 1°C / min. Finally, the sintered sample is supplemented with oxygen for 30 hours under conditions of an oxygen partial pressure of 0.5-2MPa and a temperature of 500°C.

[0022] 5. Encapsulation and assembly In order to meet the requirements of mechanical strength, electrical conductivity, safety and other aspects during the use of superconducting wire, the metal copper sleeve is seal-welded by mature laser welding technology or electron beam. Complex composite wires with different cross-sectional dimensions and shapes are realized. The present invention further discloses a method for preparing a bulk yttrium barium copper oxide superconducting material by 3D printing, in which step 1) preparing a superconducting powder precursor and step 2) compounding a print paste are the same as step 1) and step 2) in the method for preparing a stranded yttrium barium copper oxide superconducting wire by 3D printing, and the steps for the print bulk material are as follows: In this step (defined as step 3) here), the gas in the print paste needs to be evacuated; preferably, a vacuum-assisted means is used for better gas evacuation. Then, the compounded print paste is loaded into a print barrel, and the paste is pushed out of the printer needle by air pressure or mechanical pressing. In this method, computer modeling needs to be applied to design the print path of the desired structure; further, the designed print structure is replicated and formed by depositing layer by layer on the bottom plate of the stage using direct-write 3D printing technology to form a wet sample. It is preferable to use a single printer needle in the above preparation method. Then, the freeze-drying step is carried out (defined as step 4). Specifically, the printed wet sample is placed in a freeze-drying cabinet that maintains a low temperature of, for example, -30 to -60°C for 24 to 48 hours. The ice crystals in the wet sample are eliminated, and a green compact is finally formed. The above-mentioned steps of removing plastic and forming the superconducting phase are the same as those of the method of producing a superconducting stranded wire of yttrium barium copper oxide by 3D printing, and the specific details will not be repeated. This invention combines direct-write 3D printing technology with freeze-drying measures to fabricate YBCO high-temperature superconducting bulk materials, which have the advantages of ultra-lightweight, porous, complex shape, high crystallinity, good electromagnetic properties, etc. The bulk materials with different structures can be printed, for example, into rectangular parallelepipeds, cubes, grids, flywheels, skeleton disks, etc.

[0023] This invention is the first to use advanced direct-write 3D printing technology to create a micro-nanoscale superconducting core wire, then print a superconducting strand through modeling, slicing, and twisting with a printer needle, and finally realize the creation of a superconducting strand wire through plastic-free, phase formation, and encapsulation assembly.

[0024] The present invention discloses a method for producing high-temperature superconducting wires of yttrium barium copper oxide (YBCO) by 3D printing, which can be divided into four steps: first, prepare a nanoscale superconducting powder precursor; second, formulate a print paste with suitable viscosity and support properties; then, use CAD three-dimensional modeling to write out the model data in STL format, slice using specialized software; and twist the print head to produce a one-step stranded wire with low current loss. Finally, the printed stranded wire is formed into a practical superconducting stranded cable through processes such as deplasticization, phase formation, oxygen replenishment, and packaging.

[0025] Finally, please note that the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiment, those skilled in the art can still modify the technical solutions described in the above embodiment, or make equivalent substitutions for some of its technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. [Explanation of symbols]

[0026] 1 Drive shaft 2 Ink injection and pressure supply ports 3 Trough 4 Drive disc 5 Feed Tube 6 Printer Needle 7 Print Barrel 8 Bulk Materials

Claims

1. Steps below: 1) Preparation of superconducting powder precursor: The main raw material of the print is YBCO superconducting material or a mixed powder that can be sintered to form the superconducting phase; Mechanical grinding yields print powder with particle size between 100 and 300 nm; 2) Print paste composition:

2. Adding the prepared superconducting powder precursor to a mixture of polymer binder and lubricant in appropriate proportions to form a direct-write 3D printing paste; 3) Printing of stranded wires is realized by direct-write 3D printer; After the processed model slice data is input to the computer numerical control side, the computer transmits a digital signal to the communication board, and the communication board synchronously issues an ink supply communication command and a print driving command; After the ink supply communication command is issued, the gas solenoid control valve opens, and the air pressure is applied to the push plug of the hopper of the direct-write 3D printer, and the pressure is transmitted to the printing paste by the push plug, so as to form a uniform and smooth printing line from the printing system; After the print drive command is issued, three servo motors control the three-way drive of the XYZ axis, the slide rail drives of the X and Y axes precisely move and position the printer needle on the XY plane, and the high-precision roller screw drive of the Z axis lifts and lowers the bottom platform; The print drive command is transmitted to the three servo motors and simultaneously transmitted to a servo motor that drives the rotation of the needle to perform stable rotation of the needle; the three filaments extruded by the needle are fixed to a Z-axis platform and twisted in the XY plane by the continuous and unified rotation of the needle; The needle filament is continuously extended in the Z-axis direction, and the bottom platform is synchronously lowered, so that the continuous, integrated rotation of the needle and the lowering of the bottom platform are performed simultaneously in conjunction with the extension of the filament, to produce a stranded wire; by adjusting the needle thickness, extrusion pressure, the lowering speed of the bottom platform, and the rotation speed, a stranded wire with desired parameters is produced; 4) Plastic-free and superconducting phase formation treatment; 5) Characterized in that it includes an encapsulation assembly; How to 3D print superconducting strands of yttrium barium copper oxide.

2. The mixed powder capable of sintering to form a superconducting phase is copper oxide, yttrium oxide, and barium carbonate.

2. A method for producing a yttrium barium copper oxide superconducting strand by 3D printing according to claim 1.

3. The polymer binder is polyethylene glycol (PVA), polyvinylpyrrolidone (PVP), polyvinyl butyral (PVB) or sodium carboxymethylcellulose (CMC), and the lubricant is mineral or vegetable; and the binder is mixed with the lubricant in an appropriate ratio.

2. A method for producing a yttrium barium copper oxide superconducting strand by 3D printing according to claim 1.

4. The preparation work before printing in step 3) is as follows: First, inject a suitable amount of printing paste into the printer needle integrated trough via the ink injection and pressure supply port; Next, place the push plug into the trough; Finally, the pressure supply air tube is connected to an ink injection and pressure supply port that is not aligned in the same line as the axial direction of the pressure supply air tube.

2. A method for producing a yttrium barium copper oxide superconducting strand by 3D printing according to claim 1.

5. The plastic removal and superconducting phase formation treatment in step 4) is specifically as follows: The printed strand is put into a high-temperature furnace to perform heat treatment to remove polymers and impurities from the strand; the plastic removal conditions are 500°C at a constant temperature for 12-24 hours, with a heating rate of 0.5-1°C / min; the phase formation treatment conditions are sintering in an oxygen atmosphere at 900-960°C for 20-30 hours, with a heating rate of 1°C / min; and finally, the sintered sample is supplemented with oxygen at an oxygen partial pressure of 0.5-2MPa and a temperature of 500°C for 30 hours.

2. A method for producing a yttrium barium copper oxide superconducting strand by 3D printing according to claim 1.

6. The encapsulation assembly in step 5) is In order to meet the requirements of mechanical strength, electrical conductivity and safety during use of superconducting wire, the metal copper sleeve is sealed and welded by laser welding technology or electron beam; it is characterized by realizing complex composite wires with different cross-sectional dimensions and shapes.

2. A method for producing a yttrium barium copper oxide superconducting strand by 3D printing according to claim 1.

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