YBCO superconductor and 3D printing preparation method thereof

Abstract

The invention discloses a YBCO (Yttrium Barium Copper Oxide) superconductor and a 3D printing preparation method thereof. The preparation method of the YBCO superconductor comprises the following steps: firstly, dissolving a polymer binder in tert-butyl alcohol, then adding camphene, and mixing to obtain a mixed solution; then YBCO powder is mixed with the mixed solution, and printing slurry is obtained; an ink direct-writing 3D printing method is adopted, the printing slurry is used for printing, and a sintering precursor is obtained through freeze drying; and finally, sintering the sintering precursor under flowing oxygen to obtain the composite material. According to the YBCO superconductor 3D printing method, 3D printing of the YBCO superconductor is carried out by adopting the specific composite solvent tert-butyl alcohol and camphene and cooperating with the high-molecular binder, various samples in complex shapes can be stably printed, and the shape of a line can be maintained without collapse; and the required freeze-drying condition is low, the used time is short, the mechanical stress in the structure is effectively reduced, and cracks are avoided, so that the mechanical strength of the YBCO superconductor is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconducting materials, and in particular relates to a YBCO superconductor and a 3D printing preparation method thereof. Background Art

[0002] Superconducting materials, also known as superconductors, refer to conductors with zero resistance at a certain temperature. Its zero resistance characteristics at a specific temperature and anti-magnetism make it widely used. Among them: the zero resistance characteristic allows superconductors below the critical temperature to transmit electrical energy from one place to another under basically lossless conditions. This characteristic can be used to achieve large-capacity, low-voltage, low-loss, miniaturized and low-cost power transmission. The anti-magnetism makes it difficult for the external magnetic field applied to the superconductor to penetrate, and its interior shows repulsion to the external magnetic field. Among them, the superconductor that can completely shield the external magnetic field is called the first type of superconductor, and the other type of superconductor is called the second type of superconductor. For the second type of superconductor, when the external magnetic field is low, it can completely shield it from the outside, and when the external magnetic field is high, it can only partially shield it. Its anti-magnetism is not complete, but in a complex mixed state. The anti-magnetism of superconductors can be used to develop applications in superconducting magnetic suspension bearings, energy storage flywheels, magnetic suspension transportation systems, superconducting motors or generators, permanent magnets, etc. Superconductors can be divided into low-temperature superconductors and high-temperature superconductors. Low-temperature superconductors are difficult to apply in practice. Current research mainly focuses on high-temperature superconductors. The YBCO (yttrium barium copper oxide) series superconductors are one of the most studied and widely used superconductors among high-temperature superconducting materials.

[0003] YBa2Cu3O 7-δ The superconducting properties of (YBCO) are closely related to the δ value (oxygen content). Only materials that satisfy 0≤δ≤0.5 have superconductivity at Tc temperature. When δ is close to 0, its transition temperature is the highest, so it is necessary to supplement oxygen during the preparation process to improve its superconductivity.

[0004] The traditional YBCO (yttrium barium copper oxide) bulk preparation method takes a long time to prepare, and can only produce limited geometric shapes. In addition, mechanical stress is easily generated during the preparation process, resulting in the formation of many randomly distributed cracks in the overall structure, which seriously hinders its widespread application. Compared with the traditional YBCO high-temperature superconducting bulk material preparation method, 3D printing technology has the advantages of rapid manufacturing, low cost, and the ability to prepare complex shapes. Most of the existing 3D printing technologies for preparing YBCO bulk materials are based on ink direct writing (direct writing) printing, which has very high requirements on the rheological properties of the printing slurry. The slurry needs to have a lower viscosity under the action of shear force (i.e., shear thinning), but after extrusion, it needs to have sufficient self-support to maintain the shape without collapse. Therefore, it is necessary to resolve the contradiction between the viscosity of the printing slurry and the strength of the product. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a YBCO superconductor and a 3D printing preparation method thereof. The 3D printing preparation method described in the present invention can effectively reduce the mechanical stress inside the structure, avoid the generation of cracks, and improve the mechanical strength of the YBCO superconductor; and the freezing conditions of the printed green body are mild and the freezing time is short, which is conducive to saving preparation costs.

[0006] The inventive concept of the present invention is: based on the ink direct writing 3D printing technology, a specific composite solvent of tert-butyl alcohol and camphene is used, and a polymer binder is used to prepare a printing slurry, wherein: the melting point of the solvent camphene is high (48-52° C.), and the camphene can become solid in a short time after the slurry is extruded through a nozzle, and a complex shape sample can be stably printed, and the shape of the line can be maintained without collapse, and there is no need to add other additives to adjust the rheological properties of the printing slurry; tert-butyl alcohol has a low boiling point (83-85° C.), a fast sublimation rate, low required freeze-drying conditions, and a short time, which can effectively reduce the mechanical stress inside the structure and avoid the generation of cracks; the polymer binder (such as polyvinyl butyral and / or polyvinyl alcohol) is used as the "skeleton" of the 3D printed green body. After freeze drying, the solvent tert-butyl alcohol and camphene have both sublimated, and the polymer binder will bond and fix the YBCO solid powder to continue to maintain the intact shape of the printed green body. The study found that by using a mixed solvent of tert-butyl alcohol and camphene and a polymer binder as the main raw materials for 3D printing of YBCO superconductors, YBCO ceramic structures with near-net shapes and complex forms can be quickly prepared in a short period of time, and the mechanical strength of YBCO superconductors can be significantly improved.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a YBCO superconductor, comprising the following steps:

[0008] (1) the polymer binder is dissolved in the tributyl alcohol, and then amphene is added, and mixed to obtain a mixed solution;

[0009] (2) mixing YBCO powder with the mixed solution to obtain a printing slurry;

[0010] (3) using the ink direct writing 3D printing method to print with the printing slurry, followed by freeze drying to obtain a sintered precursor;

[0011] (4) Sintering the sintered precursor under flowing oxygen to obtain the YBCO superconductor.

[0012] Preferably, in step (1), the volume ratio of tert-butyl alcohol to camphene is 1:(1-2).

[0013] Preferably, in step (1), the high powder binder comprises polyvinyl butyral and / or polyvinyl alcohol.

[0014] Preferably, in step (1), the mass volume ratio of the high powder binder to the tert-butyl alcohol is 1 g: (25-100) mL.

[0015] Preferably, in step (2), the preparation step of the YBCO powder is: Y2O3, BaCO3 and CuO are weighed according to the stoichiometric ratio of YBa2Cu3O7, mixed, ball-milled, dried and sieved to obtain the powder.

[0016] Preferably, the purity of BaCO3 and CuO is 99wt%.

[0017] Preferably, the purity of Y2O3 is 99.99wt%.

[0018] Preferably, in the preparation process of YBCO powder, the process conditions of ball milling are: using ethanol as the ball milling medium, and ball milling at a speed of 180-250 r / min for 1-3 hours.

[0019] Preferably, the sieve has a mesh size of 5000-8000.

[0020] Preferably, in step (2), the mass volume ratio of the YBCO powder to the mixed solution is 100 g: (60-80) mL.

[0021] Preferably, in step (2), the mixing method is ball milling.

[0022] Preferably, in the process of preparing the printing slurry, the process conditions of ball milling are: using agate as grinding balls, and ball milling at a speed of 250-350 r / min for 6-10 hours.

[0023] Preferably, in step (3), the freeze-drying process is: first freezing with liquid nitrogen for 3-5 minutes, and then placing in a freeze dryer for freeze drying for 12-24 hours.

[0024] Preferably, in step (4), the flow rate of the flowing oxygen is 150-325 mL / min.

[0025] Preferably, in step (4), the maximum sintering temperature is 900-950°C.

[0026] Further preferably, the sintering temperature regime is: firstly heating to 450-500°C at a rate of 1-3°C / min, and keeping warm for 8-12 hours; then heating to 900-950°C at a rate of 1-3°C / min, and keeping warm for 15-25 hours; and finally cooling naturally with the furnace.

[0027] The second aspect of the present invention provides a YBCO superconductor, wherein the YBCO superconductor is prepared by the above preparation method, and the volume density of the YBCO superconductor is 3.6-4.5 g / cm 3 The compressive strength is 18.3-29.5MPa.

[0028] The third aspect of the present invention provides the use of the above-mentioned YBCO superconductor in superconducting magnetic suspension bearings, energy storage flywheels, magnetic suspension transport systems, superconducting motors, generators or permanent magnets.

[0029] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0030] The present invention is based on the ink direct writing 3D printing technology, adopts specific composite solvents of tert-butyl alcohol and camphene, and cooperates with a polymer binder to prepare a printing slurry, and performs 3D printing of a YBCO superconductor. By utilizing the high melting point of camphene, the low boiling point of tert-butyl alcohol, and the skeleton effect of the polymer binder, the printing slurry is made solid in a short time after being extruded through a nozzle by controlling the appropriate dosage relationship between the raw materials, and various complex shape samples can be stably printed, and the shape of the line can be maintained without collapse; and the required freeze-drying conditions are low and the time is short, which effectively reduces the mechanical stress inside the structure and avoids the generation of cracks, thereby significantly improving the mechanical strength of the YBCO superconductor.

[0031] The YBCO superconductor prepared by the present invention has a light porous structure, good superconducting performance and mechanical strength. When the volume density is 3.6-4.5g / cm 3 The compressive strength is 18.3-29.5MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The process flow chart of preparing YBCO superconductor of Example 1-3 of the present invention;

[0033] Figure 2 The sintering temperature curve of the YBCO superconductor prepared in Examples 1-3 of the present invention;

[0034] Figure 3 A physical picture of the YBCO superconductor prepared in Example 1 of the present invention;

[0035] Figure 4 The XRD pattern of the YBCO superconductor prepared in Example 1 of the present invention;

[0036] Figure 5 This is a diagram of the magnetic levitation experiment of the YBCO superconductor prepared in Example 1 of the present invention;

[0037] Figure 6This is a SEM image of the YBCO superconductor prepared in Example 1 of the present invention;

[0038] Figure 7 This is a SEM image of the YBCO superconductor prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0040] Example 1

[0041] A method for preparing a YBCO superconductor by direct ink 3D printing, the preparation process is as follows: Figure 1 As shown, the specific steps include:

[0042] (1) Y2O3, BaCO3 and CuO were weighed according to the stoichiometric ratio of YBa2Cu3O7, placed in a ball mill, and wet-milled at 250 r / min for 3 h using a planetary ball mill (QM-3SP2) with anhydrous ethanol as the ball milling medium and agate as the grinding balls. The YBCO powder was dried and passed through a 5000 mesh sieve;

[0043] (2) measuring 25mL tert-butyl alcohol and placing in beaker, put into magnetic stirring bar, beaker is placed on magnetic stirring apparatus, weighing 1g PVB and adding beaker, after stirring for 10min, measuring 50mL amphene and adding beaker, continue stirring for 5min, obtain mixed solutions; stirring process covers beaker mouth with sealing glue to prevent solvent volatilization;

[0044] (3) Weighing 100 g of the YBCO powder obtained in step (1) and the mixed solution obtained in step (2) into a ball mill, using a planetary ball mill (QM-3SP2) with agate as grinding balls, and wet ball milling at a speed of 280 r / min for 10 hours to obtain a printing slurry;

[0045] (4) transferring the printing slurry obtained in step (3) to the barrel of an ink direct writing 3D printer, printing according to the program, and then freezing the obtained printed green body above liquid nitrogen for 10 minutes; then transferring it to a freeze dryer for freeze drying for 24 hours to sublime the solvent to obtain a sintering precursor;

[0046] (5) The sintered precursor obtained in step (4) was placed in a tube furnace and sintered under flowing oxygen (235 mL / min) according to Figure 2 The YBCO superconductor of this embodiment is obtained by sintering at the sintering temperature system shown in FIG. Figure 3 shown.

[0047] Example 2

[0048] A method for preparing a YBCO superconductor by direct ink 3D printing, the preparation process is as follows: Figure 1 As shown, the specific steps include:

[0049] (1) Y2O3, BaCO3 and CuO were weighed according to the stoichiometric ratio of YBa2Cu3O7, placed in a ball mill, and wet-milled at 200 r / min for 2 h using a planetary ball mill (QM-3SP2) with anhydrous ethanol as the ball milling medium and agate as the grinding balls. The YBCO powder was dried and passed through a 5000 mesh sieve;

[0050] (2) measuring 25mL tert-butyl alcohol and placing in beaker, put into magnetic stirring bar, beaker is placed on magnetic stirring apparatus, takes 0.5gPVB and adds beaker, after stirring 10min, measures 25mL camphene and adds beaker, continues to stir 8min, obtains mixed solutions; Stirring process covers beaker mouth with sealing glue to prevent solvent volatilization;

[0051] (3) Weigh 70 g of the YBCO powder obtained in step (1) and the mixed solution obtained in step (2) and put them into a ball mill, use a planetary ball mill (QM-3SP2) with agate as grinding balls, and wet-mill for 8 hours at a speed of 300 r / min to obtain a printing slurry;

[0052] (4) transferring the printing slurry obtained in step (3) to the barrel of an ink direct writing 3D printer, printing according to the program, and then freezing the obtained printed green body above liquid nitrogen for 5 minutes; then transferring it to a freeze dryer for freeze drying for 12 hours to sublime the solvent to obtain a sintering precursor;

[0053] (5) The sintered precursor obtained in step (4) was placed in a tube furnace and sintered under flowing oxygen (200 mL / min) according to Figure 2 The YBCO superconductor of this embodiment is obtained by sintering at the sintering temperature regime shown.

[0054] Example 3

[0055] A method for preparing a YBCO superconductor by direct ink 3D printing, the preparation process is as follows: Figure 1 As shown, the specific steps include:

[0056] (1) Y2O3, BaCO3 and CuO were weighed according to the stoichiometric ratio of YBa2Cu3O7, placed in a ball mill, and wet-milled at 180 r / min for 1 hour using a planetary ball mill (QM-3SP2) with anhydrous ethanol as the ball milling medium and agate as the grinding balls. The YBCO powder was obtained after drying and passing through a 5000 mesh sieve;

[0057] (2) measuring 25mL tert-butyl alcohol and placing in beaker, put into magnetic stirring bar, beaker is placed on magnetic stirring apparatus, takes 0.5gPVB and adds beaker, after stirring 10min, measures 25mL amphene and adds beaker, continues to stir 10min, obtains mixed solutions; Stirring process covers beaker mouth with sealing glue to prevent solvent volatilization;

[0058] (3) Weighing 100 g of the YBCO powder obtained in step (1) and the mixed solution obtained in step (2) into a ball mill, using a planetary ball mill (QM-3SP2) with agate as grinding balls, and wet-milling at a speed of 280 r / min for 6 hours to obtain a printing slurry;

[0059] (4) transferring the printing slurry obtained in step (3) to the barrel of an ink direct writing 3D printer, printing according to the program, and then freezing the obtained printed green body above liquid nitrogen for 3 minutes; then transferring it to a freeze dryer for freeze drying for 6 hours to sublime the solvent to obtain a sintering precursor;

[0060] (5) The sintered precursor obtained in step (4) was placed in a tube furnace and sintered under flowing oxygen (150 mL / min) according to Figure 2 The YBCO superconductor of this embodiment is obtained by sintering at the sintering temperature regime shown.

[0061] Comparative Example 1

[0062] The difference between Comparative Example 1 and Example 1 is that no camphene is added in step (2). That is, step (2) of Comparative Example 1 is: take 25mL tert-butyl alcohol and place it in a beaker, put into a magnetic stirring bar, place the beaker on a magnetic stirring apparatus, weigh 1g PVB and add it to the beaker, stir for 10min, and obtain a mixed solution; and cover the beaker mouth with sealing glue to prevent solvent volatilization during the stirring process.

[0063] Comparative Example 2

[0064] The difference between Comparative Example 2 and Example 2 is that an equivalent amount of water is used to replace tert-butyl alcohol in step (2). That is, step (2) of Comparative Example 2 is: measuring 25 mL of water and placing it in a beaker, putting it into a magnetic stirring bar, placing the beaker on a magnetic stirring apparatus, weighing 1 g of PVB and adding it to the beaker, and after stirring for 10 min, measuring 50 mL of camphene and adding it to the beaker, continuing to stir for 5 min to obtain a mixed solution; and covering the beaker mouth with a sealing glue during the stirring process to prevent solvent volatilization.

[0065] Comparative Example 3

[0066] The difference between Comparative Example 3 and Example 3 is that an equivalent amount of ethanol is used to replace tert-butyl alcohol in step (2). That is, step (2) of Comparative Example 3 is: measuring 25 mL of ethanol and placing it in a beaker, putting it into a magnetic stirring bar, placing the beaker on a magnetic stirring apparatus, weighing 1 g of PVB and adding it to the beaker, and after stirring for 10 min, measuring 50 mL of camphene and adding it to the beaker, continuing to stir for 5 min to obtain a mixed solution; and covering the beaker mouth with sealing glue during the stirring process to prevent solvent volatilization.

[0067] Performance Testing

[0068] 1.XRD analysis

[0069] The YBCO superconductor sample prepared in Example 1 was subjected to XRD pattern analysis, and the results were as follows: Figure 4 As shown, Figure 4 The horizontal axis 2-Theta represents the test angle, and the vertical axis Intensity represents the diffraction peak intensity. Figure 4 It can be seen that Example 1 successfully prepared the YBa2Cu3O7 superconductor.

[0070] 2. Magnetic levitation

[0071] The YBCO superconductor sample prepared in Example 1 was placed in liquid nitrogen to cool down, and then a neodymium magnet was moved above the sample with tweezers. After the tweezers were removed, it was found that the neodymium magnet could be suspended above the sample. Figure 5 As shown, the magnetic levitation performance of the sample is demonstrated.

[0072] 3. Microstructure

[0073] The cross sections of the YBCO superconductor samples prepared in Example 1 and Comparative Example 1 were tested using a scanning electron microscope. The results are as follows: Figure 6 and Figure 7 As shown, where: Figure 6 Figures A and B in the figure are cross-sectional structures of the sample at different magnifications. Figure 6 It can be seen that the sample is built up by stacking printed lines layer by layer, and the gap between the printed lines is about 0.5mm; the grains are tightly bonded and no obvious cracks are seen; Figure 7 It can be seen that there are obvious microcracks distributed inside the sample, which will have an adverse effect on the mechanical strength.

[0074] 4. Bulk density and mechanical strength

[0075] The volume density and compressive strength of the YBCO superconductor samples prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0076] Table 1:

[0077]

[0078]

[0079] As shown in Table 1, the printing pastes of Examples 1-3, due to the use of specific composite solvents of tert-butyl alcohol and camphene, and the use of a polymer binder, the prepared YBCO superconductor samples all have a higher extrusion strength. Comparative Examples 1-3, due to the use of a single tert-butyl alcohol or other similar solvents to replace tert-butyl alcohol, have a significantly lower extrusion strength than Examples 1-3 at the same bulk density.

[0080] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, without having to go through creative labor. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the protection scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should belong to the protection scope of the present invention.

Claims

1. A method for preparing a YBCO superconductor, characterized in that: The following steps are involved: (1) the polymer binder is dissolved in the tributyl alcohol, and then amphene is added, and mixed to obtain a mixed solution; (2) mixing YBCO powder with the mixed solution to obtain a printing slurry; (3) using the ink direct writing 3D printing method to print with the printing slurry, followed by freeze drying to obtain a sintered precursor; (4) Sintering the sintered precursor under flowing oxygen to obtain the YBCO superconductor.

2. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (1), the volume ratio of the tert-butyl alcohol to the camphene is 1:(1-2).

3. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (1), the high-powder binder includes polyvinyl butyral and / or polyvinyl alcohol; and / or the mass volume ratio of the high-powder binder to the tert-butyl alcohol is 1g: (25-100)mL.

4. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (2), the preparation steps of the YBCO powder are as follows: Y2O3, BaCO3 and CuO are weighed according to the stoichiometric ratio of YBa2Cu3O7, mixed, ball-milled, dried and sieved to obtain the powder.

5. The method for preparing a YBCO superconductor according to claim 4, characterized in that: The medium of the ball milling is ethanol; and / or the rotation speed of the ball milling is 180-250 r / min; and / or the time of the ball milling is 1-3 hours.

6. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (2), the mass volume ratio of the YBCO powder to the mixed solution is 100 g: (60-80) mL.

7. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (4), the flow rate of the flowing oxygen is 150-325 mL / min.

8. The method for preparing a YBCO superconductor according to claim 1, characterized in that: In step (4), the maximum sintering temperature is 900-950°C.

9. A YBCO superconductor, characterized in that: The YBCO superconductor is prepared by the preparation method according to any one of claims 1 to 8, and the volume density of the YBCO superconductor is 3.6-4.5 g / cm 3 The compressive strength is 18.3-29.5MPa.

10. Use of the YBCO superconductor according to claim 9 in superconducting magnetic suspension bearings, energy storage flywheels, magnetic suspension transport systems, superconducting motors, generators or permanent magnets.

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