YBCO (Yttrium Barium Copper Oxide)-based superconducting flywheel as well as preparation method and application thereof

Abstract

The invention provides a YBCO (Yttrium Barium Copper Oxide)-based superconducting flywheel as well as a preparation method and application thereof, and belongs to the technical field of intelligent manufacturing of high-temperature superconducting materials. Accurate construction of the complex-shaped YBCO superconductor is achieved through the additive manufacturing technology, meanwhile, quality improvement and efficiency improvement of the complex superconductor are achieved in combination with the crystal growth regulation and control technology, the critical current density and the magnetic performance of the complex superconductor are improved, and the YBCO superconducting flywheel with the excellent superconducting electromagnetic performance can be prepared; the blank that in the prior art, preparation of a superconducting complex three-dimensional structure with excellent electromagnetic performance cannot be achieved is filled up, and then application of the YBCO superconducting block in the key fields of energy, traffic, medical treatment, aerospace and the like is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent manufacturing of high-temperature superconducting materials, and particularly to a YBCO-based superconducting flywheel and its preparation method and application. Background Art

[0002] YBa 2 Cu 3 O 7-x (Yttrium barium copper oxide, YBCO) is one of the high-temperature superconducting materials widely studied and applied at present. Its critical transition temperature (Tc) is about 93K, and superconductivity can be achieved in the liquid nitrogen temperature range. Therefore, YBCO superconducting materials have great application value in the fields of magnetic levitation, MRI (Magnetic Resonance Imaging), high-field magnets, energy storage, and power transmission equipment. These application scenarios pose two key requirements for YBCO materials: one is the need for high superconducting properties, including high critical current density (Jc) and stable flux pinning ability, to meet the requirements of efficient operation of equipment; the other is the requirement that the material can achieve customized design of complex geometric structures to meet the needs of precision engineering and high-performance equipment.

[0003] However, due to the lattice mismatch, defects, and inhomogeneities that usually exist at the grain boundaries of YBCO materials. These microstructures and physical properties will interfere with the formation and transmission of superconducting electron pairs (i.e., Cooper pairs). Furthermore, it will significantly reduce its critical current density (Jc). Therefore, the monodomainization of YBCO superconducting materials has become a key research direction for improving its Jc performance. The monodomain YBCO superconducting bulk materials prepared by traditional methods are often used to manufacture large-sized magnets and magnetic levitation devices due to their high Jc and good flux capture ability. However, this method is limited to simple geometric shapes (such as cylinders or cubes), and due to the problems of intrinsic brittleness and internal stress, the bulk materials prepared by this method are extremely prone to cracking during processes such as cutting and engraving, and cannot meet the requirements of customized design of the structures of complex devices.

[0004] In recent years, additive manufacturing technology has provided new possibilities for the preparation of complex geometric structures of YBCO materials. For the preparation technology of complex-structured YBCO superconducting bodies, the 3D printing YBCO superconducting bulk preparation technology is an effective method for preparing YBCO high-temperature superconducting bulk materials with complex shapes and diverse structures, especially suitable for ultra-light and porous superconducting structures. This technology combines direct-write 3D printing, freeze-drying, and hierarchical sintering, and can efficiently prepare superconductors with complex shapes and multi-scale structures. Compared with traditional methods, the YBCO structures prepared by additive manufacturing technology can achieve complex designs and meet the complex structural requirements in aspects such as superconducting magnetic levitation bearings, energy storage flywheels, and navigation gyroscopes. However, the existing 3D printed YBCO superconductors are obtained by configuring precursor powders into slurries, printing, drying, and then directly sintering. Its essence belongs to the powder sintering method. The samples show particle agglomeration microscopically. The prepared YBCO superconductors are polycrystalline structures, and the grain boundaries in the structure will significantly inhibit the superconducting current transport ability, resulting in the critical current density of the material being much lower than that of single-crystal YBCO. In particular, the lattice mismatch and insufficient oxygen content at the grain boundaries will increase the resistance and reduce the superconducting performance. Therefore, the YBCO superconductors prepared by the existing technology are affected by grain boundaries, have poor superconducting performance, are difficult to prepare YBCO superconducting flywheels with complex geometric shapes and high superconducting characteristics, and cannot meet the actual application requirements. Summary of the Invention

[0005] The object of the present invention is to provide a YBCO-based superconducting flywheel, its preparation method and application. The YBCO-based superconducting flywheel has excellent superconducting electromagnetic characteristics and can realize the preparation of superconducting specimens with complex shapes.

[0006] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions: The present invention provides a preparation method of a YBCO-based superconducting flywheel, comprising the following steps: 1) Mix the Y 2 BaCuO 5 printing powder, cerium oxide powder, and poly(lactic-co-glycolic acid), dichloromethane, dimethyl phthalate, and ethylene glycol monobutyl ether, and obtain a precursor slurry through extrusion grinding; according to the three-dimensional structure required for the superconducting flywheel, perform 3D printing on the precursor slurry, and after freeze-drying, obtain a supporting crystal network structure; 2) YBa 2 Cu 3 O 7-x matrix powder and Ba 3 Cu 5 O 5React and mix the powders, mix the obtained mixed powders, poly(lactic-co-glycolic acid), dichloromethane, dimethyl phthalate, and ethylene glycol monobutyl ether, and perform extrusion grinding to obtain a sacrificial body slurry; design the geometric shape according to the size and requirements of the superconducting flywheel described in step 1), perform 3D printing on the sacrificial body slurry, and after freeze-drying, obtain a sacrificial embryo block; 3) Place Y on the zirconia ceramic substrate from bottom to top in sequence 2 O 3 Isolation embryo block, sacrificial embryo block, support crystal network structure, and growth guiding layer to obtain an assembled assembly; the size of the sacrificial embryo block > the size of the support crystal network structure; the sacrificial embryo block and the support crystal network structure are provided with a fitting interface; the growth guiding layer includes an MgO single crystal plated with an NdBCO thin film, a SmBCO single-domain superconducting bulk material, or a GdBCO single-domain superconducting bulk material; 4) After pre-sintering the assembled assembly, raise the temperature to the melting temperature, lower the temperature to the temperature at which crystal growth starts, and then lower the temperature to the temperature at which crystal growth stops, and after cooling, obtain a YBCO superconducting bulk material; The temperature at which crystal growth starts is 1010 - 1015 °C; the temperature at which crystal growth stops is 970 - 980 °C; 5) Remove the Y from the YBCO superconducting bulk material 2 O 3 Isolation embryo block layer, sacrificial embryo block layer, and growth guiding layer, and perform sintering under an oxygen atmosphere condition to obtain a YBCO-based superconducting flywheel.

[0007] Preferably, in step 1), the mass ratio of the Y 2 BaCuO 5 printing powder, poly(lactic-co-glycolic acid), and dichloromethane is 1:0.09 - 0.12:2.4 - 2.7; the mass of the cerium oxide powder accounts for 0.1 - 3% of the total mass of the Y 2 BaCuO 5 printing powder; the mass of the dimethyl phthalate accounts for 2 - 10% of the total mass of the precursor slurry; the mass of the ethylene glycol monobutyl ether accounts for 1 - 5% of the total mass of the precursor slurry.

[0008] Preferably, in step 2), the YBa 2 Cu 3 O 7-x parent phase powder and Ba 3 Cu 5 O 5The molar ratio of the reactive powder is 1:1; the mass ratio of the mixed powder, poly(lactic-co-glycolic acid) copolymer to dichloromethane is 1:0.09 - 0.12:2.4 - 2.7; the mass of dimethyl phthalate accounts for 2 - 10% of the total mass of the sacrificial body slurry; the mass of ethylene glycol monobutyl ether accounts for 1 - 5% of the total mass of the sacrificial body slurry.

[0009] Preferably, the types of the chimeric interface include W-type interface or concave-convex lattice interface.

[0010] Preferably, the temperature of the pre-sintering is 920 - 950 °C, and the heat preservation time is 2 - 10 h.

[0011] Preferably, the heating rate for rising to the melting temperature is 60 - 180 °C / h, and the melting temperature is 1040 - 1060 °C.

[0012] Preferably, it is cooled to the temperature at which crystal growth starts at a rate of 30 - 120 °C / h, and cooled to the temperature at which crystal growth stops at a rate of 0.1 - 0.5 °C / h.

[0013] Preferably, the temperature of the sintering is 400 - 500 °C, and the time is 200 - 300 h.

[0014] The present invention provides a YBCO-based superconducting flywheel prepared by the preparation method described in the above technical solution.

[0015] The present invention provides the application of the YBCO-based superconducting flywheel described in the above technical solution in power grid frequency modulation and energy storage, energy recovery and stable power supply in rail transit, navigation and energy management in aerospace, medical or national defense fields.

[0016] Aiming at the production and preparation bottleneck of high-quality superconductors with complex electromagnetic characteristics and complex structures, the present invention designs the structural forms of the sacrificial embryo block and the supporting crystal network based on the required superconducting flywheel structure, controls the size relationship between the sacrificial embryo block and the crystal network structure, and the chimeric interface between the sacrificial embryo block and the supporting crystal network structure to ensure the stable growth of crystals in the complex structure body. During the heat treatment process, the complex crystal network, the sacrificial embryo block and the growth guiding layer act together to realize the regulation of crystal growth, so as to obtain crystals with complex shapes and only 3 domain regions, which can effectively realize the preparation of superconducting flywheels with both complex customized structures and excellent superconducting characteristics, and solve the problem that it is difficult to prepare YBCO superconducting materials with both complex structures and excellent superconducting characteristics by the existing methods.

[0017] The present invention utilizes additive manufacturing technology to achieve precise construction (optimized structure) of complex-shaped YBCO superconductors. Meanwhile, combined with crystal growth regulation technology, it improves the quality and efficiency of complex superconductors, enhances their critical current density and magnetic properties, and can fabricate YBCO superconducting flywheels with excellent superconducting electromagnetic properties. The present invention introduces the structural design of 3D printed superconducting flywheels, breaking through the limitation that the preparation method of traditional single-domain YBCO bulk materials is difficult to achieve customized design of complex flywheel structures, filling the gap in the prior art that cannot realize the preparation of superconducting complex three-dimensional structures with excellent electromagnetic properties, and thus promoting the application of YBCO superconducting bulk materials in key fields such as energy, transportation, medical treatment, and aerospace. Therefore, the present invention combines additive manufacturing technology and crystal growth regulation technology, successfully solving problems such as weak connection at multiple grain boundaries and poor superconducting performance in the prior art, and having the following remarkable effects: 1) Significantly improved technical performance. By regulating crystal growth, the present invention achieves consistent grain orientation at the macroscopic scale, effectively reducing the problem of weak connection at grain boundaries (such as Figure 4 ), and significantly enhancing the superconducting performance of the YBCO navigation flywheel. In a high magnetic field environment, the material exhibits excellent stability, meeting the performance requirements of high-field magnets and magnetic levitation devices. In addition, by breaking through geometric limitations through additive manufacturing technology, high-precision manufacturing of complex structures can be achieved, with a printing accuracy of up to 100 μm, which can be used for the production of other complex devices such as superconducting rings and navigation gyroscopes.

[0018] 2) Remarkable economic and social benefits. The method of the present invention can significantly reduce manual intervention and the need for mold processing, and greatly reduce production costs through efficient additive manufacturing technology and crystal growth regulation technology. Its innovative breakthrough promotes the in-depth application of high-performance complex structure YBCO superconducting devices in the fields of aerospace, clean energy, and medical technology, providing important technical support for the development of strategic industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the assembly structure and a schematic diagram of the principle of crystal-controlled growth of the combination of the present invention; Figure 2 is a schematic diagram of the additive manufacturing and assembly structure of the present invention; wherein, 1 is a 2 mm × 2 mm MgO single crystal wafer coated with a 300 nm NdBCO thin film, 2 is a supporting crystal network structure, 3 is a sacrificial embryo block, 4 is a Y 2 O 3 isolation embryo block, and 5 is a zirconia ceramic bottom plate; Figure 3 is a schematic diagram of the structure of the YBCO superconducting material prepared in Example 1 of the present invention; Figure 4 is a comparison diagram of the microstructures of the YBCO superconducting materials prepared in Comparative Example 1 and Example 1, wherein, (a) Comparative Example 1; (b) Example 1. Detailed implementation mode

[0020] In the present invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well-known to those skilled in the art.

[0021] The present invention provides a preparation method of a YBCO-based superconducting flywheel, comprising the following steps: 1) Mix Y 2 BaCuO 5 printing powder, cerium oxide powder, and poly(lactic-co-glycolic acid), dichloromethane, dimethyl phthalate, and ethylene glycol monobutyl ether, and obtain a precursor slurry through extrusion and grinding; according to the three-dimensional structure required for the superconducting flywheel, perform 3D printing on the precursor slurry, and after freeze-drying, obtain a support crystal network structure; 2) Mix YBa 2 Cu 3 O 7-x matrix powder and Ba 3 Cu 5 O 5 reaction powder, mix the obtained mixed powder, poly(lactic-co-glycolic acid), dichloromethane, dimethyl phthalate, and ethylene glycol monobutyl ether, and perform extrusion and grinding to obtain a sacrificial body slurry; design the geometric shape according to the size and requirements of the superconducting flywheel described in step 1), perform 3D printing on the sacrificial body slurry, and after freeze-drying, obtain a sacrificial embryo block; 3) Place a Y 2 O 3 isolation embryo block, a sacrificial embryo block, a support crystal network structure, and a growth guiding layer on a zirconia ceramic substrate from bottom to top to obtain an assembled assembly; the size of the sacrificial embryo block > the size of the support crystal network structure; the sacrificial embryo block and the support crystal network structure are provided with a fitting interface; the growth guiding layer includes an MgO single crystal plated with an NdBCO thin film, a SmBCO single-domain superconducting bulk material, or a GdBCO single-domain superconducting bulk material; 4) After pre-sintering the assembled assembly, raise the temperature to the melting temperature, lower the temperature to the temperature at which crystal growth starts, and then lower the temperature to the temperature at which crystal growth stops, and after cooling, obtain a YBCO superconducting bulk material; The temperature at which crystal growth starts is 1010 - 1015 °C; the temperature at which crystal growth stops is 970 - 980 °C; 5) Remove the Y 2 O 3 isolation embryo block layer, sacrificial embryo block layer, and growth guiding layer from the YBCO superconducting bulk material, and perform sintering under an oxygen atmosphere condition to obtain a YBCO-based superconducting flywheel.

[0022] In the present invention, the Y 2 BaCuO 5The method for preparing the printing powder preferably comprises: weighing yttrium oxide (Y) and yttrium oxide (Y) in a ratio of Y:Ba:Cu = 2:1:1 respectively; 2 O 3 )、barium carbonate(BaCO 3 ) and copper oxide (CuO) powder are mixed, and anhydrous ethanol accounting for 20-100% (more preferably 80%) of the weight of the mixed powder is added to the obtained mixed powder, mixed by ethanol ball milling, and after drying, sintered at a temperature of 900-920°C in an air atmosphere, and the ball milling and sintering are repeated in sequence, and the time of each sintering is preferably 24-48h, more preferably 30-36h. After two ball millings and two sinterings, submicron Y 2 BaCuO 5 Printing powder.

[0023] In the present invention, the Y 2 BaCuO 5 The mass ratio of printing powder, polylactic acid-glycolic acid copolymer and dichloromethane is 1:0.09~0.12:2.4~2.7; more preferably 1:0.1:2.6; the mass of the cerium oxide powder accounts for Y 2 BaCuO 5 The mass of the printing powder is 0.1-3%, more preferably 0.5-1%; the mass of the dimethyl phthalate accounts for 2-10%, more preferably 4.5-8% of the total mass of the precursor slurry; the mass of the ethylene glycol butyl ether accounts for 1-5%, more preferably 2.25-4% of the total mass of the precursor slurry.

[0024] The present invention preferably uses Y 2 BaCuO 5 The printing powder is added to a polylactic acid-glycolic acid copolymer and dichloromethane solution, cerium oxide powder is added, and then dimethyl phthalate and ethylene glycol butyl ether are added. The mixture is evenly mixed by extrusion and grinding, and the gas in the slurry is discharged by rotary centrifugation to obtain a stable precursor slurry.

[0025] The present invention is preferably based on the three-dimensional structure required by the superconducting flywheel, and the printing path is calculated by the slicing software of the printer. The direct writing 3D printing method is adopted, and the complex supporting lattice precursor is constructed layer by layer on the bottom plate by setting the printing rate, extrusion pressure, printing spacing, and filling method. The printed wet sample is placed in an environment of -40°C to -80°C, and freeze-dried (to remove moisture from the wet sample and form a directional arranged void structure inside the material) to obtain a supporting lattice structure (such as Figure 2 as shown).

[0026] In the present invention, the YBa 2 Cu 3 O 7-xThe preparation method of the parent-phase powder preferably includes the following steps: Mix yttrium oxide (Y 2 O 3 ), barium carbonate (BaCO 3 ), and copper oxide (CuO) powders by ball milling in a molar ratio of Y:Ba:Cu = 1:2:3, sinter at a temperature of 900 - 920 °C in an air atmosphere, and repeat ball milling and sintering in sequence. The sintering time for each time is independently preferably 24 - 48 h, more preferably 30 - 36 h. After two sinterings and two grindings, YBa 2 Cu 3 O 7-x parent-phase powder is obtained.

[0027] In the present invention, the preparation method of the Ba 3 Cu 5 O 5 reaction powder preferably includes: Mix barium carbonate (BaCO 3 ), and copper oxide (CuO) powders by ball milling in a molar ratio of Ba:Cu = 3:5, sinter at a temperature of 880 - 900 °C in an air atmosphere, and repeat ball milling and sintering in sequence. The sintering time for each time is independently preferably 24 - 48 h, more preferably 30 - 36 h. After two sinterings and two grindings, Ba 3 Cu 5 O 5 reaction powder (liquid-phase powder) is obtained.

[0028] In step 2), the molar ratio of the YBa 2 Cu 3 O 7-x parent-phase powder and Ba 3 Cu 5 O 5 reaction powder is preferably 1:1; the mass ratio of the mixed powder, poly(lactic-co-glycolic acid) copolymer, and dichloromethane is 1:0.09 - 0.12:2.4 - 2.7, more preferably 1:0.1:2.6; the mass of dimethyl phthalate accounts for 2 - 10% of the total mass of the precursor slurry, more preferably 4.5 - 8%; the mass of ethylene glycol monobutyl ether accounts for 1 - 5% of the total mass of the precursor slurry, more preferably 2.25 - 4%.

[0029] The present invention preferably uses the YBa 2 Cu 3 O 7-x parent-phase powder and Ba 3 Cu 5 O 5The reaction powders are uniformly mixed in proportion, and the mixed powders are added to a polylactic acid-glycolic acid copolymer and dichloromethane solution, followed by adding dimethyl phthalate and ethylene glycol butyl ether, and mixed uniformly by extrusion and grinding, and the gas in the slurry is discharged by rotary centrifugation to obtain a sacrificial body slurry; according to the designed geometric shape, the printing path is calculated by the slicing software provided by the printer, and the direct writing additive manufacturing method is used to set the printing rate, extrusion pressure, printing spacing and filling method to print layer by layer on the base plate to construct a sacrificial embryo block structure; the printed wet sample is placed in an environment of -40°C to -80°C for freeze drying (to remove moisture in the wet sample) to obtain a sacrificial embryo block (such as Figure 2 as shown).

[0030] During the high temperature sintering process, YBa 2 Cu 3 O 7-x Melt into Y 2 BaCuO 5 Compared with other liquid phases (BaCuO 2 , CuO), the melted liquid penetrates into the support crystal network structure of additive manufacturing under the action of capillary force, and under the induction of the existing crystals, it interacts with the Y 2 BaCuO 5 Powder reaction generates YBa 2 Cu 3 O 7-x The superconductor plays an auxiliary role in the entire reaction process. The superconducting flywheel finally prepared is a superconducting block material based on the additive manufacturing supporting crystal network structure.

[0031] The present invention has no special limitation on the zirconia ceramic substrate, and any corresponding substrate known in the art may be used.

[0032] In the present invention, the isolated embryo block is preferably Y 2 O 3 Pressed into a cylindrical block, as an isolation layer, where Y 2 O 3 The diameter of the isolation embryo block is preferably ≥ the diameter of the sacrificial embryo block to ensure that the sacrificial embryo block will not be lost during the high-temperature melting process.

[0033] In the present invention, the growth guide layer preferably comprises MgO single crystal coated with NdBCO thin film, SmBCO single domain superconducting bulk material or GdBCO single domain superconducting bulk material. The present invention has no special limitation on the sources of the materials of the growth guide layer, and commercially available products known in the art can be used.

[0034] The growth guiding layer in the present invention is more preferably a 2×2 mm MgO single crystal (commercial thin film, produced by ceraco company in Germany) plated with a 300 nm NdBCO thin film. The present invention uses a growth guiding layer (similar to the YBCO crystal structure) for growth guiding. The present invention preferably places the single crystal according to the structure of the superconducting flywheel. For example, when designing a three-blade flywheel, in order to improve the preparation efficiency, it is set at the geometric center point of the three blades of the flywheel. For a flywheel with a structural hole at the geometric center point, a 2 mm thick guiding layer is printed above the structural hole as the connection guiding layer for crystal placement and crystal growth according to requirements, and the guiding layer can be polished off after preparation.

[0035] As Figure 2 shown, in the present invention, a Y 2 O 3 isolation embryo block, a sacrificial embryo block, a support crystal network structure and a growth guiding layer are sequentially placed from bottom to top on a zirconia ceramic substrate to obtain an assembled assembly.

[0036] In the present invention, the size of the sacrificial embryo block is preferably > the size of the support crystal network structure; more preferably, the diameter of the sacrificial embryo block > the diameter of the support crystal network structure, and the thickness of the sacrificial embryo block ≥ the thickness of the support crystal network structure. The diameter of the sacrificial embryo block is preferably 5 - 8 cm, more preferably 7 cm, and the diameter of the support crystal network structure is preferably 3 - 5 cm.

[0037] In the present invention, the thickness of the zirconia ceramic substrate is preferably 10 mm, and the thickness of the Y 2 O 3 isolation embryo block is preferably 3 - 10 mm, more preferably 5 mm; the diameter of the Y 2 O 3 isolation embryo block is preferably 7 cm, the thickness of the sacrificial embryo block is preferably 10 - 30 mm, more preferably 15 mm; the thickness of the support crystal network structure is preferably 8 - 20 mm, more preferably 10 mm; the thickness of the growth guiding layer is preferably 1 mm.

[0038] The sacrificial embryo block and the support crystal network structure in the present invention are provided with a fitting interface; the type of the fitting interface preferably includes a W-shaped interface or a concave-convex dot matrix interface. The present invention has no special limitation on the specific formation process of the W-shaped interface or the concave-convex dot matrix interface, and it can be constructed in a manner well-known in the art.

[0039] The present invention preferably designs the geometric shape of the sacrificial embryo block according to the size and functional requirements of the superconducting flywheel, and the designed size of the sacrificial embryo block should be larger than the support crystal network structure of the superconducting flywheel to ensure that the sacrificial embryo block can provide sufficient liquid source to support the subsequent crystal growth process.

[0040] The present invention designs the matching of the sacrificial embryo block and the support crystal network structure, designs the chimeric interface between the sacrificial embryo block and the support crystal network structure, ensures that the two can be tightly combined during assembly, and can effectively avoid liquid loss or structural detachment.

[0041] In the present invention, the process of designing the superconducting flywheel structure is as follows: First, according to the mass and size requirements of the aerospace navigation flywheel, clarify the size parameters of the flywheel, including the outer diameter, inner diameter, blade shape, thickness, and hole distribution, and ensure that the overall has triple rotational symmetry; use CAD software to draw the basic circular contour, define the outer diameter and inner diameter; draw a single blade contour at the edge of the circle, design the arc and tip curve of the blade, and ensure a smooth transition. Achieve triple symmetry through rotational replication. Then, draw a circular hole in the center of the flywheel according to the bearing size, optimize the hole position to balance the weight distribution; convert the design into a three-dimensional model, assign thickness and perform fillet processing. Finally, check the mass distribution and balance of the model, calculate the moment of inertia, optimize the model structure and the layout of the holes, and ensure that the strength and functionality requirements are met. After completion, export the 3D model file for subsequent additive manufacturing.

[0042] The present invention places the combined assembly into a vertical high-temperature furnace, heats it to the pre-sintering temperature and holds it for insulation. Through pre-sintering, the unreacted raw materials in each powder in the combined assembly are further reacted. In addition, the present invention plays a role in plastic removal through pre-sintering, so that the rheology-adjusting auxiliary components such as poly(lactic-co-glycolic acid), dichloromethane, dimethyl phthalate, and ethylene glycol monobutyl ether in the printed embryo block and the support crystal network structure are fully removed.

[0043] In the present invention, the temperature of the pre-sintering is preferably 920 - 950 °C, more preferably 930 - 940 °C, the insulation time is preferably 2 - 10 h, more preferably 4 - 6 h; the heating rate to the pre-sintering temperature is preferably 60 - 180 °C / h, more preferably 120 °C / h.

[0044] In the present invention, the heating rate to the melting temperature is 60 - 180 °C / h, more preferably 60 - 120 °C / h, the melting temperature is 1040 - 1060 °C, more preferably 1050 °C; after heating to the melting temperature, at this time, YBa 2 Cu 3 O 7-x decomposes into Y 2 BaCuO 5 and other liquid phases, and the melted liquid infiltrates into the additive manufacturing support crystal network structure under the action of capillary force (as Figure 1 shown).

[0045] The present invention preferably cools down to the temperature at which crystal growth starts (1010 - 1015 °C, more preferably 1010 °C) at a rate of 30 - 120 °C / h (more preferably 60 °C / h), and then cools down to the temperature at which crystal growth stops (970 - 980 °C, more preferably 980 °C) at a rate of 0.1 - 0.5 °C / h (more preferably 0.3 °C / h). The process of crystal growth starting is a process of continuous cooling, during which the temperature continuously changes and no heat preservation is carried out. As Figure 1 shown, during the cooling process, the melted liquid reacts with Y 2 BaCuO 5 to generate the YBa 2 Cu 3 O 7-x phase, and grows from the center outwards in a two-dimensional nucleation growth mode on the basis of the NdBCO thin film, and at the same time grows layer by layer downwards under the guidance of the grown layer into a single-domain textured YBCO superconducting bulk material, and finally cools to room temperature at a relatively fast cooling rate (60 - 180 °C / h).

[0046] After obtaining the YBCO superconducting bulk material, the present invention preferably removes the residual Y 2 O 3 isolation embryo block layer, sacrificial embryo block layer and growth guiding layer by cutting and grinding, and sintering is carried out under the condition of a flowing oxygen atmosphere to obtain a YBCO-based superconducting flywheel.

[0047] In the present invention, the temperature of the sintering is preferably 400 - 500 °C, more preferably 400 - 450 °C, and the time is preferably 200 - 300 h, more preferably 200 - 250 h.

[0048] The present invention provides a YBCO-based superconducting flywheel prepared by the preparation method described in the above technical solution.

[0049] The present invention provides the application of the YBCO-based superconducting flywheel described in the above technical solution in power grid frequency modulation and energy storage, energy recovery and stable power supply in rail transit, navigation and energy management in aerospace, medical or national defense fields.

[0050] The following combines examples to elaborate on the technical solutions provided by the present invention in detail, but they cannot be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] Step 1: Preparation of additive powder 1.1. Preparation of crystal network powder: Weigh yttrium oxide (Y 2 O 3 ), barium carbonate (BaCO 3)(Y) and copper oxide (CuO) powders, initially mixed, and the mixed powders are added with absolute ethanol accounting for 80% of the mass of the mixed powders. The mixture is uniformly mixed by ethanol ball milling, dried, and sintered at a temperature of 920 °C in an air atmosphere for 30 h each time. After two sinterings and two ball millings, Y with an average particle size < 1 μm is obtained. 2 BaCuO 5 Printing powder.

[0053] 1.2. Preparation of auxiliary powder: Weigh yttrium oxide (Y 2 O 3 ), barium carbonate (BaCO 3 ), and copper oxide (CuO) powders according to the molar ratio of Y:Ba:Cu = 1:2:3, ball mill and mix them, and sinter them at a temperature of 920 °C in an air atmosphere for 30 h each time. After two sinterings and two grindings, YBa 2 Cu 3 O 7-x Matrix powder is obtained.

[0054] 1.3. Preparation of liquid-phase powder: Weigh barium carbonate (BaCO 3 ) and copper oxide (CuO) powders according to the molar ratio of Ba:Cu = 3:5, ball mill and mix them, and sinter them at a temperature of 880 °C in an air atmosphere for 30 h each time. After two sinterings and two grindings, Ba 3 Cu 5 O 5 Reaction powder is obtained.

[0055] Step 2: Structural design of superconducting flywheel and sacrificial embryo block 2.1. Structural design of superconducting flywheel (design of complex support crystal network structure): First, design the structural parameters of the flywheel. In this embodiment, the outer diameter of the flywheel is 50 mm, the bearing hole size is 10 mm, and the flywheel as a whole has triple rotational symmetry. Therefore, the structural design of this embodiment is as follows: Use CAD software to draw a basic circular contour with a diameter of 50 mm, and draw a circle with a diameter of 10 mm at the same center. Draw circles with a diameter of 25 cm with the three equally divided points on the outer edge of the large circle as the centers, trim the redundant drawing lines to retain the sketch of the flywheel main body, and draw a three-dimensional main body by vertical sweeping. The thickness of the flywheel is 15 mm. After completion, export the 3D model file for subsequent additive manufacturing.

[0056] 2.2. Geometric design of sacrificial embryo block According to the flywheel size and structure in this embodiment, the sacrificial embryo block is designed as a cylindrical shape, where the cylinder diameter is 7 cm and the height is 2 cm to ensure that the sacrificial embryo block can provide sufficient liquid-phase support for the flywheel.

[0057] 2.3. Design of matching between sacrificial embryo block and supporting crystal network structure A W-shaped corrugated interlocking interface between the sacrificial embryo block and the supporting crystal structure is designed, with a corrugation height of 4 mm and a spacing of 4 mm.

[0058] Step 3: Additive Manufacturing of Complex Support Network Structures Y 2 BaCuO 5 Printing powder was mixed with polylactic acid-glycolic acid copolymer and dichloromethane in a mass ratio of 1:0.1:2.6, and Y 2 BaCuO 5 0.5wt% cerium oxide powder was printed, followed by adding 4.5% dimethyl phthalate and 2.25% ethylene glycol butyl ether, respectively. The mixture was extruded, ground and mixed evenly, and the gas in the slurry was discharged by rotary centrifugation to obtain a stable precursor slurry. Based on the flywheel three-dimensional structure designed in step 2, the printing path is calculated by the slicing software that comes with the printer. The direct writing 3D printing method is used to print layer by layer on the base plate to construct a complex supporting lattice precursor. The printed wet sample is placed in an environment of -50°C, and then freeze-dried to remove moisture from the wet sample, and a directional arranged void structure is formed inside the material to obtain a supporting crystalline structure.

[0059] Step 4: Preparation of sacrificial embryos YBa 2 Cu 3 O 7-x Parent phase powder and Ba 3 Cu 5 O 5 The reaction powders are uniformly mixed in a molar ratio of 1:1, and the mixed powders are mixed with polylactic acid-glycolic acid copolymer and dichloromethane in a mass ratio of 1:0.1:2.6, and then dimethyl phthalate accounting for 4.5% of the total mass of the sacrificial body slurry and ethylene glycol butyl ether accounting for 2.25% of the total mass of the sacrificial body slurry are added, and the mixture is extruded, ground and mixed uniformly, and the gas in the slurry is discharged by rotary centrifugation to obtain a stable sacrificial body slurry.

[0060] According to the three-dimensional structure of the sacrificial embryo block designed in step two, the printing path is calculated by the slicing software provided by the printer, and the sacrificial embryo block structure is constructed layer by layer on the base plate by using the direct writing additive manufacturing method; the printed wet sample is placed in an environment of -50°C, and then the moisture in the wet sample is removed by freeze drying to obtain the sacrificial embryo block.

[0061] Step 5: Assemble the assembly Y 2O 3 Press it into a cylindrical isolation embryo block as the isolation layer; Place the isolation embryo block, sacrificial embryo block, and support crystal network structure on the zirconia ceramic substrate from bottom to top in sequence, and place a 2×2 mm MgO single crystal (commercial thin film, produced by German ceraco company) plated with a 300 nm NdBCO thin film to obtain an assembled assembly; among them, the thickness of the zirconia ceramic substrate is 10 mm, Y 2 O 3 The thickness of the isolation embryo block is 5 mm, and the diameter of the isolation embryo block is 7 cm; the thickness of the sacrificial embryo block is 15 mm, and the diameter is 7 cm; the thickness of the support crystal network structure is 10 mm, and the diameter is 5 cm, and the thickness of the MgO single crystal plated with the NdBCO thin film is 1 mm.

[0062] Step Six: Crystal Controlled Growth Put the assembled assembly into a vertical high-temperature furnace, heat it up to the pre-sintering temperature (940 °C) at a relatively fast heating rate (120 °C / h) and keep it warm for 6 h, then heat it up to the highest melting temperature (1050 °C) at a relatively fast rate (60 °C / h), then cool it down to the crystal starting growth temperature (1010 °C) at a cooling rate of 60 °C / h, and then cool it down to the crystal stopping growth temperature (980 °C) at a rate of 0.3 °C / h, and cool it to room temperature at a relatively fast cooling rate (60 °C / h) to obtain a YBCO superconducting bulk.

[0063] Step Seven: Post-treatment Process Take out the sintered assembled assembly, remove the residual isolation layer, sacrificial layer, and MgO single crystal plated with the NdBCO thin film by cutting and grinding, and sinter it at 400 °C for 200 h under the condition of a flowing oxygen atmosphere to obtain a YBCO superconducting flywheel, as shown in the physical object Figure 3 shown.

[0064] Comparative Example 1 Prepare YBCO superconductor by 3D printing technology: Mix yttrium oxide (Y 2 O 3 ), barium carbonate (BaCO 3 ), and copper oxide (CuO) powders evenly according to the molar ratio of 1:4:6, add the obtained mixed powder (the mass proportion relative to the printing slurry is 50%) to the sodium alginate aqueous solution (the concentration of the sodium alginate aqueous solution is 6.5 wt.%, and the mass proportion relative to the printing slurry is 40%) and the dispersant epoxy soybean oil (the mass proportion relative to the printing slurry is 10%), and make the slurry disperse evenly by extrusion grinding to obtain a printing slurry; The printing slurry was 3D printed in the flywheel structure established in Example 1 by direct writing 3D printing. After freeze-drying, the green body was sintered at 920 °C in an oxygen atmosphere for 30 h to obtain a YBCO superconductor.

[0065] Characterization and performance testing Figure 4 It is a comparative diagram of the microstructures of the YBCO superconducting materials prepared in Comparative Example 1 and Example 1. Among them, (a) is Comparative Example 1; (b) is Example 1. As Figure 4 can be seen, the microstructure in Comparative Example 1 shows a porous structure, the particles are agglomerated, and there are obvious weak grain boundary connections, which is the main reason for the poor superconducting performance of the material; while the microstructure in Example 1 is dense and the surface is relatively smooth, which indicates that the problem of weak grain boundary connections has been effectively improved. The improvement of the weak grain boundary connection problem and the densification of the microstructure can effectively improve the superconducting characteristics of the material.

[0066] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a YBCO-based superconducting flywheel, characterized in that: The following steps are involved: 1) Y2BaCuO5 printing powder, cerium oxide powder, polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether are mixed and extruded and ground to obtain a precursor slurry; the precursor slurry is 3D printed according to the three-dimensional structure required for the superconducting flywheel, and a supporting crystal network structure is obtained after freeze drying; 2) YBa2Cu3O 7-x The parent phase powder and the Ba3Cu5O5 reaction powder are mixed, and the obtained mixed powder, polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether are mixed, and extruded and ground to obtain a sacrificial body slurry; according to the size and requirements of the superconducting flywheel in step 1), the geometric shape is designed, and the sacrificial body slurry is 3D printed, and after freeze-drying, a sacrificial embryo block is obtained; 3) placing a Y2O3 isolation embryo block, a sacrificial embryo block, a supporting crystal network structure and a growth guide layer on a zirconia ceramic substrate from bottom to top in order to obtain a combined assembly; the size of the sacrificial embryo block is greater than the size of the supporting crystal network structure; the sacrificial embryo block and the supporting crystal network structure are provided with a mosaic interface; the growth guide layer comprises a MgO single crystal coated with a NdBCO thin film, a SmBCO single domain superconducting bulk material or a GdBCO single domain superconducting bulk material; 4) After pre-sintering the combined assembly, the temperature is raised to the melting temperature, the temperature is lowered to the temperature at which the crystal starts to grow, and the temperature is lowered to the temperature at which the crystal stops growing, and after cooling, a YBCO superconducting bulk material is obtained; The temperature at which the crystal starts to grow is 1010-1015°C; the temperature at which the crystal stops growing is 970-980°C; 5) removing the Y2O3 isolation block layer, the sacrificial block layer and the growth guide layer from the YBCO superconducting block material, and sintering the YBCO superconducting flywheel in an oxygen atmosphere.

2. The preparation method according to claim 1, characterized in that: In step 1), the mass ratio of the Y2BaCuO5 printing powder, polylactic acid-glycolic acid copolymer and dichloromethane is 1:0.09~0.12:2.4~2.7; the mass of the cerium oxide powder accounts for 0.1~3% of the total mass of the Y2BaCuO5 printing powder; the mass of the dimethyl phthalate accounts for 2~10% of the total mass of the precursor slurry; the mass of the ethylene glycol butyl ether accounts for 1~5% of the total mass of the precursor slurry.

3. The preparation method according to claim 1, characterized in that: In step 2), the YBa2Cu3O 7-x The molar ratio of the parent phase powder to the Ba3Cu5O5 reaction powder is 1:1; the mass ratio of the mixed powder, polylactic acid-glycolic acid copolymer and dichloromethane is 1:0.09~0.12:2.4~2.7; the mass of the dimethyl phthalate accounts for 2~10% of the total mass of the sacrificial body slurry; the mass of the ethylene glycol butyl ether accounts for 1~5% of the total mass of the sacrificial body slurry.

4. The preparation method according to claim 1, characterized in that: The types of the mosaic interface include a W-type interface or a concave-convex lattice interface.

5. The preparation method according to claim 1, characterized in that: The pre-sintering temperature is 920-950° C., and the heat preservation time is 2-10 hours.

6. The preparation method according to claim 1, characterized in that: The heating rate to the melting temperature is 60-180°C / h, and the melting temperature is 1040-1060°C.

7. The preparation method according to claim 1 or 6, characterized in that: The temperature is lowered at a rate of 30-120°C / h to the temperature at which the crystal starts to grow, and then lowered at a rate of 0.1-0.5°C / h to the temperature at which the crystal stops growing.

8. The preparation method according to claim 1, characterized in that: The sintering temperature is 400-500° C. and the sintering time is 200-300 hours.

9. A YBCO-based superconducting flywheel prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the YBCO-based superconducting flywheel described in claim 9 in power grid frequency modulation and energy storage, energy recovery and stable energy supply for rail transportation, navigation and energy management in aerospace, medical or defense fields.

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