YBCO-based superconducting flywheel and preparation method and application thereof

Abstract

The application provides a YBCO-based superconducting flywheel and a preparation method and application thereof, and belongs to the technical field of intelligent manufacturing of high-temperature superconducting materials. The application realizes accurate construction of a complex-shaped YBCO superconductor by using additive manufacturing technology, and realizes quality improvement and efficiency increase of the complex superconductor by combining crystal growth regulation technology, so that the critical current density and the magnetic performance are improved. The YBCO superconducting flywheel with excellent superconducting electromagnetic performance can be prepared, the blank that the existing technology cannot realize preparation of a superconducting complex three-dimensional structure with excellent electromagnetic performance is filled, and the application of the YBCO superconducting bulk material in key fields such as energy, transportation, medical treatment and aerospace is promoted.

Description

TECHNICAL FIELD

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

[0002] YBa2Cu3O 7-x Yttrium barium copper oxide (YBCO) is one of the high-temperature superconducting materials that are widely studied and applied at present, and has a critical transition temperature (Tc) of about 93 K, and can realize superconductivity in the liquid nitrogen temperature range. Therefore, the YBCO superconducting material has great application value in the fields of magnetic suspension, MRI (magnetic resonance imaging), high-field magnet, energy storage and power transmission equipment, etc. These application scenarios put forward two key requirements for the YBCO material: first, a relatively high superconducting property, including a high critical current density (Jc) and stable magnetic flux pinning ability, is required to meet the demand for efficient operation of the equipment; second, the material is required to realize customized design of complex geometric structures to meet the demand for precise engineering and high-performance equipment.

[0003] However, due to the lattice mismatch, defects and inhomogeneity of the grain boundaries of the YBCO material. These microstructures and physical properties will interfere with the formation and transport of superconducting electron pairs (i.e., Cooper pairs). In turn, it will significantly reduce the critical current density (Jc) thereof. Therefore, the single-domain of the YBCO superconducting material becomes a key research direction to improve its Jc performance. The single-domain YBCO superconducting bulk material prepared by the traditional method is often used to manufacture large-size magnets and magnetic suspension devices due to its high Jc and good magnetic flux trapping 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 material prepared by this method is extremely easy to crack in the process of cutting and carving, and cannot meet the structural customization demand of complex devices.

[0004] In recent years, additive manufacturing technology provides new possibilities for the preparation of complex geometry of YBCO material. For the preparation technology of complex structure YBCO superconductor, 3D printing YBCO superconducting bulk material preparation technology is an effective method for preparing YBCO high temperature superconducting bulk material with complex shape and various structures, especially suitable for super light and porous superconducting structure. The technology combines direct writing 3D printing, freeze drying and hierarchical sintering, and can efficiently prepare superconductors with complex shape and multi-scale structure. Compared with traditional methods, YBCO structures prepared by additive manufacturing technology can realize complex design and meet the complex structure requirements of superconducting magnetic suspension bearings, energy storage flywheels, navigation gyroscopes and the like. However, the existing 3D printed YBCO superconductor is configured into a slurry by precursor powder, and after drying and sintering, the YBCO superconductor is obtained. Its essence belongs to powder sintering method, and the sample presents a granular agglomeration in microstructure. The YBCO superconductor prepared is a polycrystalline structure, and the grain boundaries in the structure will significantly inhibit the transmission capacity of superconducting current, so that the critical current density of the material is 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 superconductor prepared by the existing technology is affected by the grain boundaries, and there are problems such as poor superconducting performance, difficulty in realizing the preparation of YBCO superconducting flywheel with complex geometry and high superconducting performance, and inability to meet the actual application. SUMMARY

[0005] The purpose of the present application is to provide a YBCO-based superconducting flywheel and its preparation method and application, which has high superconducting electromagnetic properties and can realize the preparation of complex shape superconducting test pieces.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of YBCO-based superconducting flywheel, comprising the following steps:

[0008] 1) Mix Y2BaCuO5 printing powder, cerium oxide powder, polylactic acid-hydroxyacetic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether, and obtain a precursor slurry by extrusion grinding; according to the required three-dimensional structure of the superconducting flywheel, the precursor slurry is 3D printed, and after freeze drying, a support crystal structure is obtained;

[0009] 2) Mix YBa2Cu3O 7-x Mix the obtained mixed powder, polylactic acid-hydroxyacetic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether, and obtain a sacrificial body slurry by extrusion grinding; according to the size and requirement design of the superconducting flywheel in step 1), the sacrificial body slurry is 3D printed, and after freeze drying, a sacrificial embryo block is obtained;

[0010] 3) placing Y2O3 isolation embryo, sacrificial embryo, support crystal structure and growth guide layer on the zirconia ceramic substrate from bottom to top to obtain a combined assembly; the size of the sacrificial embryo > the size of the support crystal structure; the sacrificial embryo and the support crystal structure are provided with a fitting interface; the growth guide layer comprises MgO single crystal plated with NdBCO thin film, SmBCO single domain superconducting bulk material or GdBCO single domain superconducting bulk material;

[0011] 4) after pre-sintering the combined assembly, heating to a melting temperature, cooling to a crystal growth starting temperature, and then cooling to a crystal growth stopping temperature, and cooling, to obtain a YBCO superconducting bulk material;

[0012] The crystal growth starting temperature is 1010-1015℃, and the crystal growth stopping temperature is 970-980℃.

[0013] 5) removing the Y2O3 isolation embryo layer, the sacrificial embryo layer and the growth guide layer from the YBCO superconducting bulk material, and sintering in an oxygen atmosphere to obtain a YBCO-based superconducting flywheel.

[0014] Preferably, in step 1), the mass ratio of Y2BaCuO5 printing powder, polylactic acid-glycolic acid copolymer and dichloromethane is 1:0.09-0.12:2.4-2.7; the mass of cerium oxide powder accounts for 0.1-3% of the total mass of Y2BaCuO5 printing powder; the mass of dimethyl phthalate accounts for 2-10% of the total mass of the precursor slurry; and the mass of ethylene glycol butyl ether accounts for 1-5% of the total mass of the precursor slurry.

[0015] Preferably, in step 2), the YBa2Cu3O 7-x The molar ratio of the parent phase powder and 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 dimethyl phthalate accounts for 2-10% of the total mass of the sacrificial body slurry; and the mass of ethylene glycol butyl ether accounts for 1-5% of the total mass of the sacrificial body slurry.

[0016] Preferably, the type of the fitting interface includes a W-type interface or a concave-convex point array interface.

[0017] Preferably, the pre-sintering temperature is 920-950℃, and the holding time is 2-10h.

[0018] Preferably, the heating rate to the melting temperature is 60-180℃ / h, and the melting temperature is 1040-1060℃.

[0019] Preferably, the temperature is decreased to the temperature at which the crystal starts to grow at a rate of 30-120 DEG C / h, and the temperature is decreased to the temperature at which the crystal stops growing at a rate of 0.1-0.5 DEG C / h.

[0020] Preferably, the sintering temperature is 400-500 DEG C, and the time is 200-300 h.

[0021] The application provides a YBCO-based superconducting flywheel prepared by the preparation method.

[0022] The application provides application of the YBCO-based superconducting flywheel in grid frequency modulation and energy storage, energy recovery and stable energy supply of rail transit, navigation and energy management of aerospace, medical treatment or national defense.

[0023] In view of the bottleneck in production and preparation of high-quality superconductors with complex structures, the application designs the structure of a sacrifice embryo block and a support crystal network based on the required structure of the superconducting flywheel, controls the size relationship between the sacrifice embryo block and the crystal network structure and the embedded interface of the sacrifice embryo block and the support crystal network structure, so that the stable growth of the crystal in the complex structure is ensured, in the process of heat treatment, the complex crystal network, the sacrifice embryo block and the growth guide layer jointly act to realize the regulation of crystal growth, so that the crystal with a complex shape and only three domains is obtained, and the preparation of the superconducting flywheel with complex customized structure and high superconducting performance can be effectively realized, and the problem that the YBCO superconductor with complex structure and high superconducting performance is difficult to prepare by using the prior art method is solved.

[0024] The application realizes the precise construction (optimized structure) of the YBCO superconductor with a complex shape by using the additive manufacturing technology, and realizes the quality improvement and efficiency improvement of the complex superconductor by combining the crystal growth regulation technology, so that the critical current density and the magnetic performance are improved, and the YBCO superconducting flywheel with excellent superconducting electromagnetic performance can be prepared. The application introduces the structure design of the 3D printed superconducting flywheel, breaks through the limitation that the preparation method of the traditional single-domain YBCO block material cannot realize the customized design of the complex flywheel structure, fills the gap that the prior art cannot realize the preparation of the superconducting complex three-dimensional structure with excellent electromagnetic performance, and further promotes the application of the YBCO superconducting block material in key fields such as energy, transportation, medical treatment and aerospace. Therefore, the application successfully solves the problems of weak connection of the polycrystal boundary and poor superconducting performance in the prior art by combining the additive manufacturing technology and the crystal growth regulation technology, and has the following remarkable effects:

[0025] 1) The technical performance is significantly improved. The application realizes the consistent grain orientation on the macro scale by regulating the crystal growth, and effectively reduces the problem of weak connection of the crystal boundary (such as Figure 4), which significantly enhances the superconducting performance of YBCO navigation flywheels. In high magnetic field environments, the material exhibits excellent stability, meeting the performance requirements of high-field magnets and magnetic levitation equipment. In addition, through additive manufacturing technology, the geometric limitations are broken, and high-precision manufacturing of complex structures is achieved, with a printing accuracy of 100 μm, which can be used for the production of superconducting toroids and navigation gyroscopes and other complex devices.

[0026] 2) Significant economic and social benefits. The method of the present application can significantly reduce manual intervention and mold processing requirements, and greatly reduce production costs through efficient additive manufacturing technology and crystal growth control technology. The innovation breakthrough promotes the in-depth application of high-performance complex structure YBCO superconducting devices in the fields of aerospace, clean energy and medical technology, and provides important technical support for industrial development. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The schematic diagram of the assembly structure of the present application and the crystal growth control principle diagram;

[0028] Figure 2 The schematic diagram of additive manufacturing and assembly structure of the present application; wherein, 1 is a 2mm x 2mm MgO single crystal wafer plated with a 300nm NdBCO thin film, 2 is a support crystal structure, 3 is a sacrificial embryo block, 4 is a Y2O3 isolation embryo block, and 5 is a zirconia ceramic bottom plate;

[0029] Figure 3 The schematic diagram of the YBCO superconducting material structure prepared in Example 1 of the present application;

[0030] Figure 4 The microstructure comparison diagram of the YBCO superconducting materials prepared in Comparative Example 1 and Example 1, wherein (a) is Comparative Example 1; (b) is Example 1. DETAILED DESCRIPTION

[0031] In the present application, if not specially stated, the required raw materials or reagents are all commercially available goods well known to those skilled in the art.

[0032] The present application provides a preparation method of YBCO-based superconducting flywheel, comprising the following steps:

[0033] 1) Y2BaCuO5 printing powder, cerium oxide powder, polylactic acid-hydroxyacetic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether are mixed, and a precursor slurry is obtained by extrusion grinding; according to the required three-dimensional structure of the superconducting flywheel, the precursor slurry is 3D printed, and after freeze-drying, a support crystal structure is obtained;

[0034] 2) YBa2Cu3O 7-xThe mother phase powder and the Ba3Cu5O5 reaction powder are mixed, the obtained mixed powder, polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and glycol butyl ether are mixed, extrusion grinding is carried out, and a sacrifice body slurry is obtained; according to the size and requirement of the superconducting flywheel in step 1), a geometric shape is designed, and the sacrifice body slurry is subjected to 3D printing, and after freeze-drying, a sacrifice embryo block is obtained;

[0035] 3) placing Y2O3 isolation embryo blocks, sacrifice embryo blocks, support crystal structure and growth guide layers on a zirconia ceramic substrate from bottom to top in sequence to obtain a combined assembly; the size of the sacrifice embryo block > the size of the support crystal structure; the sacrifice embryo block and the support crystal structure are provided with a fitting interface; the growth guide layer comprises MgO single crystal plated with NdBCO thin film, SmBCO single domain superconducting block material or GdBCO single domain superconducting block material;

[0036] 4) after pre-sintering the combined assembly, heating to a melting temperature, cooling to a crystal growth starting temperature, and then cooling to a crystal growth stopping temperature, cooling, YBCO superconducting block material is obtained;

[0037] The crystal growth starting temperature is 1010-1015℃; and the crystal growth stopping temperature is 970-980℃;

[0038] 5) removing the Y2O3 isolation embryo block layer, the sacrifice embryo block layer and the growth guide layer from the YBCO superconducting block material, and sintering in an oxygen atmosphere to obtain a YBCO-based superconducting flywheel.

[0039] In the application, the preparation method of the Y2BaCuO5 printing powder preferably comprises: respectively taking yttrium oxide (Y2O3), barium carbonate (BaCO3) and copper oxide (CuO) powder in a proportion of atomic mole ratio Y:Ba:Cu=2:1:1, adding 20-100% (more preferably 80%) of anhydrous ethanol to the obtained mixed powder, mixing by means of ethanol ball milling, drying, and then sintering at a temperature of 900-920℃ in an air atmosphere, and repeatedly performing ball milling and sintering in sequence, and the sintering time of each time is independently preferably 24-48h, and more preferably 30-36h, and after two times of ball milling and two times of sintering, submicron Y2BaCuO5 printing powder is obtained.

[0040] In the present application, 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; more preferably 1:0.1:2.6; the mass of the cerium oxide powder accounts for 0.1~3% of the total mass of the Y2BaCuO5 printing powder, more preferably 0.5~1%; the mass of the dimethyl phthalate accounts for 2~10% of the total mass of the precursor slurry, more preferably 4.5~8%; the mass of the ethylene glycol butyl ether accounts for 1~5% of the total mass of the precursor slurry, more preferably 2.25~4%.

[0041] The present application preferably adds Y2BaCuO5 printing powder to a polylactic acid-glycolic acid copolymer and dichloromethane solution, adds cerium oxide powder, and then adds dimethyl phthalate and ethylene glycol butyl ether, uniformly mixes by means of extrusion grinding, discharges the gas in the slurry by means of rotary centrifugation, and obtains a stable precursor slurry.

[0042] The present application preferably calculates the printing path by means of the slicing software of the printer based on the three-dimensional structure required by the superconducting flywheel, adopts the method of direct writing type 3D printing, sets the printing rate, extrusion air pressure, printing interval and filling mode, and prints and constructs the complex support lattice precursor on the base plate layer by layer, places the printed wet sample in an environment of-40℃~-80℃, freeze-dries (removes the moisture in the wet sample to form a directional arrangement of void structures in the material), and obtains the support lattice structure (as shown in Figure 2 ).

[0043] In the present application, the YBa2Cu3O 7-x The preparation method of the parent phase powder preferably comprises the following steps: ball-milling yttrium oxide (Y2O3), barium carbonate (BaCO3) and copper oxide (CuO) powder in a molar ratio of Y:Ba:Cu=1:2:3, sintering at a temperature of 900~920℃ in an air atmosphere, and repeatedly performing ball-milling and sintering in sequence, and the sintering time of each time is independently preferably 24~48h, more preferably 30~36h, and after two times of sintering and two times of grinding, YBa2Cu3O 7-x parent phase powder is obtained.

[0044] In the present application, the preparation method of the Ba3Cu5O5 reaction powder preferably comprises: ball-milling barium carbonate (BaCO3) and copper oxide (CuO) powder in a molar ratio of Ba:Cu=3:5, sintering at a temperature of 880~900℃ in an air atmosphere, and repeatedly performing ball-milling and sintering in sequence, and the sintering time of each time is independently preferably 24~48h, more preferably 30~36h, and after two times of sintering and two times of grinding, Ba3Cu5O5 reaction powder (liquid phase powder) is obtained.

[0045] In step 2), the YBa2Cu3O 7-x The molar ratio of the mother phase powder and the Ba3Cu5O5 reaction powder is preferably 1:1; the mass ratio of the mixed powder, the 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 dimethyl phthalate accounts for 2~10% of the total mass of the precursor slurry, more preferably 4.5~8%; the mass of the ethylene glycol butyl ether accounts for 1~5% of the total mass of the precursor slurry, more preferably 2.25~4%.

[0046] Preferably, the YBa2Cu3O 7-x The mother phase powder and the Ba3Cu5O5 reaction powder are uniformly mixed in proportion, the mixed powder is added to the polylactic acid-glycolic acid copolymer and dichloromethane solution, then the dimethyl phthalate and the ethylene glycol butyl ether are added, and the mixture is uniformly mixed by extrusion grinding, the gas in the slurry is discharged by rotary centrifugation, and the sacrificial body slurry is obtained; according to the designed geometric shape, the printing path is calculated by the slicing software of the printer, and the sacrificial embryo block structure is printed on the base plate layer by layer by setting the printing speed, extrusion air pressure, printing spacing and filling mode by using the direct writing type additive manufacturing method; the printed wet sample is placed in an environment of-40℃~-80℃, and freeze-drying (removing the moisture in the wet sample) is carried out to obtain the sacrificial embryo block (as shown in Figure 2

[0047] In the high-temperature sintering process, the YBa2Cu3O 7-x The melted liquid penetrates into the additive manufacturing support crystal network structure under the action of capillary force, reacts with the Y2BaCuO5 powder in the crystal network structure under the induction of the existing crystal to generate YBa2Cu3O 7-x superconductor, and finally the prepared superconducting flywheel is a superconducting bulk material with the additive manufacturing support crystal network structure as the matrix.

[0048] The zirconia ceramic substrate in the present application is not specially limited, and the corresponding substrate known in the art can be used.

[0049] In the present application, the isolation embryo block is preferably a Y2O3 cylinder embryo block, which is used as an isolation layer, and the diameter of the Y2O3 isolation embryo block is preferably greater than or equal to the diameter of the sacrificial embryo block to ensure that the sacrificial embryo block does not flow away during the high-temperature melting process.

[0050] ​In this invention, the growth guiding layer preferably comprises a MgO single crystal coated with an NdBCO thin film, an SmBCO single-domain superconducting bulk material, or a GdBCO single-domain superconducting bulk material. This invention does not impose any particular limitation on the source of the materials used in the growth guiding layer; commercially available products well-known in the art are acceptable.

[0051] The growth guiding layer of this invention is more preferably a 2×2mm MgO single crystal (commercial thin film, produced by Ceraco, Germany) coated with a 300 nm NdBCO film. This invention uses a growth guiding layer (similar to the YBCO crystal structure) for growth guidance. Preferably, the single crystal is placed according to the structure of the superconducting flywheel, for example, a three-bladed flywheel is designed. To improve fabrication efficiency, a guide layer is set at the geometric center of the three blades. For flywheels where the geometric center is a structural hole, a 2mm thick guiding layer is printed above the structural hole as a connection guiding layer between the crystal placement point and crystal growth, as required. After fabrication, the guiding layer is polished off.

[0052] like Figure 2 As shown, the present invention involves placing a Y2O3 isolation preform, a sacrificial preform, a supporting crystal structure, and a growth guiding layer sequentially from bottom to top on a zirconia ceramic substrate to obtain a combined assembly.

[0053] In this invention, the size of the sacrificial preform is preferably greater than the size of the supporting crystalline structure; more preferably, the diameter of the sacrificial preform is greater than the diameter of the supporting crystalline structure, and the thickness of the sacrificial preform is greater than or equal to the thickness of the supporting crystalline structure. The diameter of the sacrificial preform is preferably 5-8 cm, more preferably 7 cm, and the diameter of the supporting crystalline structure is preferably 3-5 cm.

[0054] In this invention, the thickness of the zirconia ceramic substrate is preferably 10 mm, the thickness of the Y2O3 isolation preform is preferably 3-10 mm, more preferably 5 mm; the diameter of the Y2O3 isolation preform is preferably 7 cm, the thickness of the sacrificial preform is preferably 10-30 mm, more preferably 15 mm; the thickness of the supporting crystal structure is preferably 8-20 mm, more preferably 10 mm; and the thickness of the growth guiding layer is preferably 1 mm.

[0055] The sacrificial embryo and the supporting crystal structure of the present invention are provided with an interlocking interface; the type of the interlocking interface preferably includes a W-shaped interface or a concave-convex lattice interface. The present invention does not have a special limitation on the specific formation process of the W-shaped interface or the concave-convex lattice interface, and it can be constructed in a manner known in the art.

[0056] The present invention preferably designs the geometry of the sacrificial preform according to the size and functional requirements of the superconducting flywheel. The size of the designed sacrificial preform should be larger than the supporting crystal structure of the superconducting flywheel to ensure that the sacrificial preform can provide a sufficient liquid source to support the subsequent crystal growth process.

[0057] The present application matches the sacrificial embryo block with the support crystal structure, designs the fitting interface of the sacrificial embryo block and the support crystal structure, ensures that the two can be closely combined during assembly, and can effectively avoid liquid loss or structure separation.

[0058] In the present application, the process of superconducting flywheel structure design is as follows: firstly, according to the mass and size requirements of the aerospace navigation flywheel, the size parameters of the flywheel are determined, including the outer diameter, the inner diameter, the blade shape, the thickness and the hole distribution, and the overall three-fold rotational symmetry is ensured; the basic circular contour is drawn using CAD software, and the outer diameter and the inner diameter are defined; the single blade contour is drawn on the edge of the circle, the arc and the tip curve of the blade are designed to ensure smooth transition. Three-fold symmetry is achieved by rotating and copying. Then, a circular hole is drawn in the center of the flywheel according to the bearing size, and the hole position is optimized to balance the weight distribution; the design is converted into a three-dimensional model, the thickness is given and the fillet processing is carried out. Finally, the quality distribution and balance of the model are checked, the rotational inertia is calculated, the model structure and the hole layout are optimized to ensure that the strength and functional requirements are met. After completion, the 3D model file is exported for subsequent additive manufacturing.

[0059] In the present application, the combined assembly is placed in a vertical high-temperature furnace, heated to a pre-sintering temperature and kept for a certain time, and the unreacted raw materials in the powders in the combined assembly are further reacted by pre-sintering. In addition, the pre-sintering plays a role in plastic removal, and the rheological blending aid components such as polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether in the printed embryo block and support crystal structure are fully removed.

[0060] In the present application, the pre-sintering temperature is preferably 920-950℃, more preferably 930-940℃, and the holding time is preferably 2-10h, more preferably 4-6h; the heating rate to the pre-sintering temperature is preferably 60-180℃ / h, more preferably 120℃ / h.

[0061] In the present application, the heating rate to the melting temperature is 60-180℃ / h, more preferably 60-120℃ / h, and the melting temperature is 1040-1060℃, more preferably 1050℃; after heating to the melting temperature, the YBa2Cu3O 7-x decomposes into Y2BaCuO5 and other liquid phases, and the melted liquid penetrates into the additive manufacturing support crystal structure under the action of capillary force (as shown in Figure 1 ).

[0062] The present application preferably cools down to the temperature at which the crystal starts to grow (1010~1015℃, more preferably 1010℃) at a rate of 30~120℃ / h (more preferably 60℃ / h), and then cools down to the temperature at which the crystal stops growing (970~980℃, more preferably 980℃) at a rate of 0.1~0.5℃ / h (more preferably 0.3℃ / h). The process of the crystal starting to grow is a process of continuous cooling, and the temperature continuously changes in this stage without holding. Figure 1 As shown in the figure, during the cooling process, the melted liquid reacts with Y2BaCuO5 to generate YBa2Cu3O 7-x The NdBCO film grows in a two-dimensional nucleation and growth mode from the center to the outside, and grows layer by layer downward under the guidance of the grown layer to form a single-domain textured YBCO superconducting bulk material, and finally cools down to room temperature at a faster cooling rate (60~180℃ / h).

[0063] After obtaining the YBCO superconducting bulk material, the present application preferably removes the residual Y2O3 isolation embryo layer, the sacrificial embryo layer and the growth guide layer by cutting and polishing, and sintering in a flowing oxygen atmosphere to obtain a YBCO-based superconducting flywheel.

[0064] In the present application, the sintering temperature is preferably 400~500℃, more preferably 400~450℃, and the time is preferably 200~300h, more preferably 200~250h.

[0065] The present application provides a YBCO-based superconducting flywheel prepared by the preparation method of the above technical solution.

[0066] The present application provides applications of the YBCO-based superconducting flywheel of the above technical solution in grid frequency modulation and energy storage, energy recovery and stable energy supply of rail transit, navigation and energy management of aerospace, medical or national defense fields.

[0067] The technical solutions provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0068] Example 1

[0069] Step one: preparation of additive powder

[0070] 1.1, preparation of crystalloid powder:

[0071] Y2O3, BaCO3 and CuO powders were weighed according to the atomic molar ratio Y:Ba:Cu = 2:1:1, and then mixed. The mixed powders were added to 80% of the mass of the mixed powders of anhydrous ethanol, and then mixed uniformly by using ethanol ball milling. After drying, the powders were sintered at a temperature of 920°C in an air atmosphere for 30 hours each time. After two sintering and two ball milling, Y2BaCuO5 printing powders with an average particle size of <1 μm were obtained.

[0072] 1.2, Preparation of auxiliary powders:

[0073] Y2O3, BaCO3 and CuO powders were weighed according to the atomic molar ratio Y:Ba:Cu = 2:1:1, and then mixed. The mixed powders were added to 80% of the mass of the mixed powders of anhydrous ethanol, and then mixed uniformly by using ethanol ball milling. After drying, the powders were sintered at a temperature of 920°C in an air atmosphere for 30 hours each time. After two sintering and two ball milling, Y2BaCuO5 printing powders with an average particle size of <1 μm were obtained. 7-x parent phase powders.

[0074] 1.3, Preparation of liquid phase powders:

[0075] BaCO3 and CuO powders were weighed according to the atomic molar ratio Y:Ba:Cu = 2:1:1, and then mixed. The mixed powders were added to 80% of the mass of the mixed powders of anhydrous ethanol, and then mixed uniformly by using ethanol ball milling. After drying, the powders were sintered at a temperature of 920°C in an air atmosphere for 30 hours each time. After two sintering and two ball milling, Y2BaCuO5 printing powders with an average particle size of <1 μm were obtained.

[0076] Step two: structure design of superconducting flywheel and sacrificial embryo block

[0077] 2.1, Structure design of superconducting flywheel (complex support crystal network structure design):

[0078] First, the structure parameters of the flywheel were designed. In this embodiment, the flywheel has an outer diameter of 50 mm, a bearing hole size of 10 mm, and a three-fold rotational symmetry. Therefore, the structure design of this embodiment is as follows: a basic circular contour with a diameter of 50 mm is drawn using CAD software, and a circle with a diameter of 10 mm is drawn at the same center. Three circles with a diameter of 25 cm are drawn as the centers of the three equal parts of the large circular outer edge. The excess drawing lines are trimmed to retain the flywheel main body sketch. A three-dimensional main body is drawn by vertical scanning. The flywheel thickness is 15 mm. After completion, the 3D model file is exported for subsequent additive manufacturing.

[0079] 2.2, Geometric design of sacrificial embryo block

[0080] According to the size and structure of the flywheel in this embodiment, the sacrificial embryo block is designed as a cylindrical shape, with a diameter of 7 cm and a height of 2 cm, to ensure that the sacrificial embryo block can provide sufficient liquid support for the flywheel.

[0081] 2.3. Design of matching between sacrificial embryo block and support crystal lattice structure

[0082] Design the W-shaped corrugated interface between the sacrificial embryo block and the support crystal lattice structure, with a corrugation height of 4 mm and a pitch of 4 mm.

[0083] Step three: Additive manufacturing of complex support crystal lattice structure

[0084] Mix Y2BaCuO5 printing powder with polylactic acid-glycolic acid copolymer and dichloromethane according to the mass ratio of 1:0.1:2.6, add 0.5wt% of cerium oxide powder to the mass of Y2BaCuO5 printing powder, then add 4.5% of dimethyl phthalate to the total mass of the precursor slurry, and add 2.25% of ethylene glycol butyl ether to the total mass of the precursor slurry, extrude and grind to mix uniformly, remove the gas in the slurry by rotary centrifugation, and obtain a stable precursor slurry.

[0085] Based on the three-dimensional structure of the flywheel designed in step two, the printing path is calculated by the slicing software of the printer, and the direct writing 3D printing method is used to print the complex support lattice precursor layer by layer on the base plate. Place the printed wet sample in an environment of-50℃, then remove the water in the wet sample by freeze-drying, and form a directional arrangement of void structures in the material, to obtain the support crystal lattice structure.

[0086] Step four: Sacrificial embryo block preparation

[0087] Mix YBa2Cu3O 7-x Mix the mother phase powder and Ba3Cu5O5 reaction powder according to the molar ratio of 1:1, mix the mixed powder with polylactic acid-glycolic acid copolymer and dichloromethane according to the mass ratio of 1:0.1:2.6, then add 4.5% of dimethyl phthalate to the total mass of the sacrificial body slurry, and add 2.25% of ethylene glycol butyl ether to the total mass of the sacrificial body slurry, extrude and grind to mix uniformly, and remove the gas in the slurry by rotary centrifugation, to obtain a stable sacrificial body slurry.

[0088] According to the three-dimensional structure of the sacrificial embryo block designed in step two, the printing path is calculated by the slicing software of the printer, and the direct writing additive manufacturing method is used to print the complex support lattice structure layer by layer on the base plate. Place the printed wet sample in an environment of-50℃, then remove the water in the wet sample by freeze-drying, and obtain the sacrificial embryo block.

[0089] Step five: Assembly of the assembly

[0090] Press Y2O3 into a cylindrical isolation embryo block as an isolation layer;

[0091] A 2x2mm MgO single crystal (commercial film, produced by ceraco company, Germany) coated with 300nm NdBCO film was placed on the zirconia ceramic substrate in order from bottom to top, to obtain a combined assembly; wherein the thickness of the zirconia ceramic substrate was 10mm, the thickness of the Y2O3 spacer embryo was 5mm, and the diameter of the spacer embryo was 7cm; the thickness of the sacrificial embryo was 15mm, and the diameter was 7cm; the thickness of the support crystal structure was 10mm, and the diameter was 5cm; the thickness of the MgO single crystal coated with NdBCO film was 1mm.

[0092] Step six: crystal regulation growth

[0093] The assembled combined assembly was placed in a vertical high-temperature furnace, and heated to a pre-sintering temperature (940℃) at a faster heating rate (120℃ / h) for 6h, then heated to the highest melting temperature (1050℃) at a faster rate (60℃ / h), then cooled to the temperature at which the crystal began to grow (1010℃) at a rate of 60℃ / h, then cooled to the temperature at which the crystal stopped growing (980℃) at a rate of 0.3℃ / h, and then cooled to room temperature at a faster cooling rate (60℃ / h), to obtain a YBCO superconducting bulk material.

[0094] Step seven: post-processing process

[0095] After sintering, the combined assembly was taken out, and the residual spacer layer, sacrificial layer and MgO single crystal coated with NdBCO film were removed by cutting and polishing, and sintered at a temperature of 400℃ for 200h in a flowing oxygen atmosphere, to obtain a YBCO superconducting flywheel, as shown in Figure 3 .

[0096] Comparative example 1

[0097] Preparation of YBCO superconductor by 3D printing technology: Yttrium oxide (Y2O3), barium carbonate (BaCO3), and copper oxide (CuO) powders were mixed uniformly in a molar ratio of 1:4:6, and the obtained mixed powders (accounting for 50% of the mass of the printing slurry) were added to a sodium alginate aqueous solution (sodium alginate aqueous solution concentration was 6.5wt.%, accounting for 40% of the mass of the printing slurry) and a dispersant epoxy soybean oil (accounting for 10% of the mass of the printing slurry), and the slurry was uniformly dispersed by extrusion grinding to obtain a printing slurry.

[0098] The printing slurry was 3D printed in a direct writing type 3D printing manner according to the flywheel structure established in example 1, and the green body was sintered at 920℃ for 30h in an oxygen atmosphere after freeze-drying, to obtain a YBCO superconductor.

[0099] Characterization and performance test

[0100] Figure 4 Comparative diagrams show the microstructures of YBCO superconducting materials prepared in Comparative Example 1 and Example 1, where (a) is Comparative Example 1 and (b) is Example 1.

[0101] Depend on Figure 4 It can be seen that the microstructure in Comparative Example 1 is porous with aggregated particles and obvious weak grain boundary connections, which is the main reason for the poor superconducting performance of the material. In contrast, the microstructure in Example 1 is dense and has a smooth surface, which indicates that the problem of weak grain boundary connections has been effectively improved. The improvement of weak grain boundary connections and the densification of the microstructure can effectively improve the superconducting properties of the material.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of making a YBCO-based superconducting flywheel, comprising: The method comprises the following steps: 1) mixing Y2BaCuO5 printing powder, cerium oxide powder, polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether, and grinding by extrusion to obtain a precursor slurry; according to the three-dimensional structure required by the superconducting flywheel, the precursor slurry is 3D printed, and after freeze-drying, a support crystal structure is obtained; 2) YBa2Cu3O7-x 7-x The mother phase powder and the Ba3Cu5O5 reaction powder are mixed, the obtained mixed powder, polylactic acid-glycolic acid copolymer, dichloromethane, dimethyl phthalate and ethylene glycol butyl ether are mixed, extrusion grinding is performed, and a sacrificial body slurry is obtained; according to the size and requirements of the superconducting flywheel described in step 1), the geometry is designed, the sacrificial body slurry is subjected to 3D printing, and after freeze-drying, a sacrificial embryo block is obtained; 3) placing Y2O3 isolation embryo blocks, sacrificial embryo blocks, support crystal structures and growth guide layers on a zirconia ceramic substrate from bottom to top to obtain a combined assembly; the size of the sacrificial embryo blocks is greater than that of the support crystal structure; the sacrificial embryo blocks and the support crystal structure are provided with a fitting interface; the growth guide layer comprises MgO single crystal coated with NdBCO thin film, SmBCO single-domain superconducting bulk material or GdBCO single-domain superconducting bulk material; 4) after pre-sintering the combined assembly, heating to a melting temperature, cooling to a crystal growth starting temperature, and then cooling to a crystal growth stopping temperature, and cooling, a YBCO superconducting bulk material is obtained; the crystal growth starting temperature is 1010-1015℃; and the crystal growth stopping temperature is 970-980℃; 5) removing the Y2O3 isolation embryo block layer, the sacrificial embryo block layer and the growth guide layer from the YBCO superconducting bulk material, and sintering in an oxygen atmosphere to obtain a YBCO-based superconducting flywheel.

2. The production method according to claim 1, characterized by, 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; and 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 and the Ba3Cu5O5 reaction powder is 1:1; the mass ratio of the mixed powder, the 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 method of claim 1, wherein, The type of the fitting interface includes a W-type interface or a concave-convex point array interface.

5. The preparation method according to claim 1, characterized in that, The pre-sintering temperature is 920-950℃, and the holding time is 2-10h.

6. The method of claim 1, wherein, The heating rate to the melting temperature is 60-180℃ / h, and the melting temperature is 1040-1060℃.

7. The production method according to claim 1 or 6, characterized by, The cooling rate to the crystal growth starting temperature is 30-120℃ / h, and the cooling rate to the crystal growth stopping temperature is 0.1-0.5℃ / h.

8. The method of claim 1, wherein, The sintering temperature is 400-500℃, and the time is 200-300h.

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

10. The YBCO-based superconducting flywheel of claim 9 for use in grid frequency modulation and energy storage, energy recovery and stable power supply for rail transit, navigation and energy management for aerospace, medical or national defense fields.

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