A method for preparing a super-elastic ceramic single crystal particle

Abstract

The application provides a preparation method of super-elastic ceramic single crystal particles, comprising the following steps: modified dispersion, drying, sieving, two-step sintering and single crystalization. x Zr 1‑x O2, wherein N is at least one of Ce, Y, Mg and Ca; 0.02<=x<=0.18; wherein the particle size of the super-elastic ceramic single crystal particles is 0.2-5 microns. The super-elastic ceramic single crystal particles prepared by the method have uniform composition, concentrated particle size distribution, near complete austenitization, high yield, low precursor price and are suitable for batch production.

Description

Technical Field

[0001] This invention relates to the field of smart materials technology, specifically to a method for preparing zirconium dioxide-based superelastic ceramic single crystal particles, and more particularly to a superelastic ceramic single crystal particle prepared by a process of modification dispersion, drying and sieving, two-step sintering, and grinding single crystallization. The particle has uniform composition, concentrated particle size distribution, high yield / yield, and inexpensive precursor, making it suitable for mass production. Background Technology

[0002] Superelastic ceramics, as a typical type of smart material, can undergo a reversible martensitic phase transformation from tetragonal to monoclinic under the action of temperature or stress fields, thereby causing significant superelasticity. They have wide applications in microelectromechanical systems, damping energy consumption, sensing and actuation, elastothermal refrigeration and other fields.

[0003] To mitigate the intrinsic brittleness of polycrystalline ceramics, Christopher A. Schuh, Chee Lip Gan, Zehui Du, and other researchers prepared a class of highly reversible, cyclically-dependent, superelastic ceramic single-crystal particles using the sol-gel method (J. Am. Ceram. Soc. 100, 4199-4208, 2017). However, this method suffers from low yield (less than 10g per batch), low efficiency (less than 50%), and expensive precursor salts. In the same year, the research team employed a spray-drying method, using slurry premixing, pressure spraying, and annealing sintering to prepare a class of highly reversible, cyclically-dependent, superelastic ceramic particles (Acta Mater. 123, 255-263, 2017; US2019 / 0039959A1). While this method somewhat overcomes the low yield and high cost, the prepared particles have a wide size distribution (6±5μm) and contain a large number of polycrystalline particles.

[0004] In view of the shortcomings of the above preparation methods, the present invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a superelastic ceramic single crystal particle, which has advantages such as uniform composition, concentrated particle size distribution, and near-complete austenitization.

[0006] The second objective of this invention is to provide a method for preparing the aforementioned superelastic ceramic single crystal particles, which has the advantages of high yield, low cost of precursors, and suitability for mass production.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention also provides a method for preparing superelastic ceramic single crystal particles, comprising the following steps:

[0009] A1. Modification and Dispersion: Weigh out the oxide powder and zirconium oxide powder containing doped element N according to the proportion, add solvent, and mechanically ball mill at 200-300 rpm to obtain a uniformly mixed slurry; then add modifier, and continue ball milling at 300-400 rpm for a period of time to obtain a well dispersed gel-like slurry;

[0010] A2. Drying and sieving: Place the gel-like slurry obtained in step A1 in a ventilated environment at 50-100℃ and dry for 6-12 hours. Then, sieve it through a 50-200 mesh screen to obtain the composite modified powder.

[0011] A3. Two-step sintering: The composite modified powder obtained in step A2 is heated to 700-800℃ in air at 3-5℃ / min, held for 1-3 hours to remove the binder, and then heated to 1350-1750℃ at 5-10℃ / min and held for 15-30 minutes. After cooling to room temperature, superelastic ceramic polycrystalline particles are obtained.

[0012] A4. Grinding and Single Crystallization: After ball milling or grinding the polycrystalline particles of superelastic ceramics, pass them through a 200-500 mesh sieve and anneal them at 600-800℃ for 4-6 hours to obtain single crystal particles of superelastic ceramics.

[0013] As a preferred embodiment, in step A1, the particle size of the N-doped oxide powder and zirconium oxide powder is both less than 100 nm. Small-particle-size precursor powders are beneficial for gel formation and make it easier to achieve uniform composition.

[0014] As a preferred embodiment, the solvent is one or a mixture of several of the following: water, ethanol, propanol, isopropanol, acetone, and butanone.

[0015] As a preferred embodiment, in step A1, the doping element N is at least one of Ce, Y, Mg, and Ca, and the doping amount of doping element N in the superelastic ceramic single crystal particles is 2-18 mol%.

[0016] As a preferred embodiment, in step A1, the total weight ratio of the oxide powder containing doped element N and the zirconium oxide powder to the solvent is 2-1:1.

[0017] As a preferred embodiment, in step A1, the modifier is one or a mixture of several of the following: isobutylene-maleic anhydride copolymer, acrylamide, sodium dodecyl sulfate, fatty amine, polyvinyl alcohol, diethanolamine, triethanolamine, N-alkyldiethyltriamine, and formamide.

[0018] As a preferred embodiment, the weight ratio of the modifier to the solvent is 0.2-2%:1.

[0019] As a more preferred embodiment, in step A1, the modifier is an isobutylene-maleic anhydride copolymer. Compared to other modifiers, the isobutylene-maleic anhydride copolymer contains no metal ions, leaves no ash residue after sintering, has low toxicity, and possesses the characteristics of both a dispersant and a gelling agent.

[0020] As a preferred embodiment, in step A1, mechanical ball milling is performed at 200-300 rpm for 10-17 hours to obtain a uniformly mixed slurry; ball milling is then continued at 300-400 rpm for 1 hour to obtain a well-dispersed gel-like slurry.

[0021] As a preferred option, in step A3, the temperature is increased to 1350-1750℃ at a rate of 5-10℃ / min, held for 15-30min, and then cooled to room temperature to obtain superelastic ceramic polycrystalline particles.

[0022] As a preferred option, in step A4, the superelastic ceramic polycrystalline particles are ground and then passed through a 200-500 mesh sieve.

[0023] This invention also provides a superelastic ceramic single crystal particle prepared according to the aforementioned method, wherein the compositional expression of the superelastic ceramic single crystal particle is: N x Zr 1-x O2;

[0024] Wherein, N is at least one of Ce, Y, Mg, and Ca, and x is the atomic molar ratio, 0.02≤x≤0.18;

[0025] The particle size of the superelastic ceramic single crystal particles is 0.2-5 μm.

[0026] As a preferred embodiment, in the superelastic ceramic particles, N is at least one of Ce and Y.

[0027] As a preferred option, when N is Ce, 0.14 ≤ x ≤ 0.18;

[0028] When N is Y, 0.02≤x≤0.04.

[0029] As a preferred embodiment, the actual atomic molar ratio error of the doping elements in the superelastic ceramic single crystal particles is within ±0.005.

[0030] As a preferred embodiment, the mass percentage of austenite in the prepared state of the superelastic ceramic single crystal particles is higher than 80%; more preferably higher than 85%, further preferably higher than 95%, and most preferably higher than 99%.

[0031] In the superelastic ceramic single crystal particles of the present invention, the main role of nitrogen element is to increase the content of austenite. Depending on the choice of nitrogen element, the appropriate content is controlled to avoid the formation of martensite due to too low content and the formation of cubic phase that cannot be transformed due to too high content, thereby exerting a good superelastic effect.

[0032] In the preparation method of the superelastic ceramic single crystal particles, a suitable modifier is used. On the one hand, it can be adsorbed on the surface of the precursor nanoparticles, increasing the negative charge density on the particle surface and improving the absolute value of the particle zeta potential, thereby increasing the repulsive force between particles, improving the dispersibility of the slurry, and helping to prepare a slurry with low viscosity and high solid content, thus increasing the yield. On the other hand, through the amphiphilic (hydrophilic and oleophilic) effect of the modifier, the surface tension of the nanoparticles can be reduced, and a gel network can be quickly formed through hydrogen bonding, improving the binding and compositional uniformity of the two precursor nanoparticles and avoiding component separation or sedimentation during the preparation process.

[0033] In the preparation method of the superelastic ceramic single crystal particles, the drying and sieving process is conducive to separating the composite cross-linked particles at the micron scale, which not only protects the uniformity of the composition, but also facilitates the subsequent grinding and single crystallization; the two-step sintering process is conducive to the full removal of binders, and it is easy to obtain superelastic single crystal particles with the target size and uniform distribution by controlling the maximum sintering temperature; the use of grinding process instead of ball milling process for single crystallization, as well as the subsequent long-term annealing, can eliminate the influence of mechanical stress on single crystal particles to the greatest extent.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The superelastic ceramic single crystal particles prepared by this invention have a concentrated particle size distribution, uniform composition, and high degree of austenitization. According to the test, the austenite content of the superelastic single crystal particles in the preparation state is more than 80%, and the austenite content is more than 70% after 20 cycles of liquid nitrogen temperature-room temperature.

[0036] 2. The preparation method adopted in this invention uses inexpensive and readily available precursors, and the doping amount and single crystal particle size can be controlled according to the precursor ratio and sintering temperature, which is easy to promote; it can also take into account the dispersibility and composition uniformity of the slurry, and has high yield and output (the yield of single crystal particles is over 60%), which is conducive to large-scale production.

[0037] 3. The preparation method used in this invention does not use toxic organic solvents, and the preparation process is safe, clean, and pollution-free; it has a wide range of applications, saves energy and time, and is reliable and efficient. Attached Figure Description

[0038] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 This is a scanning electron microscope image of the superelastic ceramic single crystal particles prepared according to Example 1 of the present invention. The nominal composition of the superelastic ceramic single crystal particles is Ce. 0.14 Zr 0.86 O2;

[0040] Figure 2 This is an X-ray diffraction pattern of the superelastic ceramic single crystal particles prepared according to Example 1 of the present invention. The horizontal axis represents the 2θ angle, and the vertical axis represents the normalized diffraction intensity. The nominal composition of the superelastic ceramic single crystal particles is Ce. 0.14 Zr 0.86 O2;

[0041] Figure 3 This is a scanning electron microscope image of the superelastic ceramic single crystal particles prepared according to Example 2 of the present invention. The nominal composition of the superelastic ceramic single crystal particles is Y. 0.03 Zr 0.97 O2;

[0042] Figure 4 This is an X-ray diffraction pattern of the superelastic ceramic single crystal particles prepared according to Example 2 of the present invention. The horizontal axis represents the 2θ angle, and the vertical axis represents the normalized diffraction intensity. The nominal composition of the superelastic ceramic single crystal particles is Y. 0.03 Zr 0.97 O2. Detailed Implementation

[0043] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0044] The methods used to test the performance of the superelastic ceramic single crystal particles prepared in the following examples are all conventional methods, such as using GB T 15445.2-2006 standard and scanning electron microscopy to measure the size distribution; and using X-ray diffraction method as described in the literature (J.Am.Ceram.Soc.55,303–305,1972) to measure the austenite content.

[0045] Example 1

[0046] This embodiment provides a superelastic ceramic single crystal particle (Ce). 0.14 Zr 0.86The preparation method of O2 includes the following steps:

[0047] 1) Modified dispersion: Weigh 12.97 g of CeO2 powder (particle size 50 nm) and 57.03 g of ZrO2 powder (particle size 50 nm) and dissolve them in 35 g of ultrapure water. Then, mechanically ball mill at 300 rpm for 12 h to obtain a uniformly mixed slurry. Then add 0.35 g of isobutylene-maleic anhydride copolymer (purchased from KURARAY, product model ISOBAM 104) and ball mill at 350 rpm for 1 h to obtain a well dispersed gel-like slurry.

[0048] 2) Drying and sieving: The above gel-like slurry was placed in a ventilated environment at 80°C and dried for 12 hours. It was then sieved through a 100-mesh sieve to obtain ~68 grams of composite modified powder, which was placed in an alumina boat.

[0049] 3) Two-step sintering: Under air atmosphere, the above-mentioned composite modified powder is heated to 750°C at 3°C / min in a box furnace, held for 1 hour to remove the binder, and then heated to 1600°C at 10°C / min and held for 15 minutes. After cooling to room temperature, superelastic ceramic polycrystalline particles are obtained.

[0050] 4) Grinding and monocrystallineization: After grinding the polycrystalline particles of superelastic ceramic in a mortar, the particles are passed through a 500-mesh sieve and annealed at 600℃ for 6 hours to obtain ~64 grams of superelastic ceramic monocrystalline particles.

[0051] 5) Material Characterization. Using scanning electron microscopy (SEM), the size of the superelastic ceramic single-crystal particles was characterized as 3.1 ± 0.3 μm. Figure 1 As shown; using X-ray diffraction (XRD), the mass percentage of austenite in the single crystal particles of this superelastic ceramic was determined to be 99.2%. Figure 2 As shown, three random samples were taken from the prepared superelastic ceramic single crystal particles. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the atomic molar ratio of Ce in the superelastic single crystal particles, which was 0.141 ± 0.003. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the mass percentage of austenite in the superelastic ceramic single crystal particles was 97.0%. The preparation yield was 91.4%. The final obtained superelastic ceramic single crystal particles with Ce content... 0.14 Zr 0.86 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0052] Example 2

[0053] This embodiment provides a superelastic ceramic single crystal particle (Y). 0.03 Zr 0.97 The preparation method of O2 includes the following steps:

[0054] 1) Modified dispersion: Weigh 3.80 g of Y2O3 powder (particle size 50 nm) and 136.20 g of ZrO2 powder (particle size 50 nm) and dissolve them in 70 g of ethanol. Mechanically ball mill at 200 rpm for 10 h to obtain a uniformly mixed slurry. Then add 0.35 g of isobutylene-maleic anhydride copolymer and ball mill at 400 rpm for 1 h to obtain a well dispersed gel-like slurry.

[0055] 2) Drying and sieving: The above gel-like slurry was placed in a ventilated environment at 50°C and dried for 6 hours. Then, it was sieved through a 200-mesh sieve to obtain ~132 grams of composite modified powder, which was placed in an alumina boat.

[0056] 3) Two-step sintering: Under air atmosphere, the above-mentioned composite modified powder is heated to 800℃ at 5℃ / min in a box furnace, held for 2 hours to remove the binder, and then heated to 1500℃ at 5℃ / min for 15 minutes. After cooling to room temperature, superelastic ceramic polycrystalline particles are obtained.

[0057] 4) Grinding and monocrystallineization: After grinding the polycrystalline particles of superelastic ceramic in a mortar, the particles are passed through a 250-mesh sieve and annealed at 800℃ for 4 hours to obtain ~125g of superelastic ceramic monocrystalline particles.

[0058] 5) Material Characterization. The size of the superelastic ceramic single crystal particles is 0.6±0.3μm, such as... Figure 3 As shown; the mass percentage of austenite is 100%, such as Figure 4 As shown; the Y content was 0.030±0.001; after 20 cycles of liquid nitrogen temperature-room temperature cycling, the mass percentage of austenite in the superelastic ceramic single crystal particles was 98.2%. The preparation yield was 89.3%. The final obtained superelastic ceramic single crystal particles Y 0.03 Zr 0.97 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0059] Example 3

[0060] This embodiment provides a superelastic ceramic single crystal particle (Ce). 0.16 Zr 0.84 The preparation method of O2 includes the following steps:

[0061] 1) Modified dispersion: Weigh 14.71 g of CeO2 powder (particle size 50 nm) and 55.29 g of ZrO2 powder (particle size 50 nm) and dissolve them in 35 g of ethanol. Mechanically ball mill at 300 rpm for 17 h to obtain a uniformly mixed slurry. Then add 0.7 g of isobutylene-maleic anhydride copolymer and ball mill at 300 rpm for 1 h to obtain a well dispersed gel-like slurry.

[0062] 2) Drying and sieving: The above gel-like slurry was placed in a ventilated environment at 50°C and dried for 6 hours. Then, it was sieved through a 200-mesh sieve to obtain ~68 grams of composite modified powder, which was placed in an alumina boat.

[0063] 3) Two-step sintering: Under air atmosphere, the above-mentioned composite modified powder is heated to 700℃ at 5℃ / min in a box furnace, held for 3h to remove the binder, and then heated to 1650℃ at 5℃ / min for 15min. After cooling to room temperature, superelastic ceramic polycrystalline particles are obtained.

[0064] 4) Grinding and monocrystallineization: After grinding the polycrystalline particles of superelastic ceramic in a mortar, the particles are passed through a 250-mesh sieve and annealed at 600℃ for 6 hours to obtain ~65 grams of superelastic ceramic monocrystalline particles.

[0065] 5) Material Characterization. The size of the superelastic ceramic single crystal particles was 2.5 ± 0.1 μm, with an austenite mass percentage of 100% and a Ce content of 0.159 ± 0.003. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass percentage in the superelastic ceramic single crystal particles was 99.5%. The preparation yield was 92.8%. The final obtained superelastic ceramic single crystal particles contained Ce. 0.16 Zr 0.84 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0066] Example 4

[0067] This embodiment is basically the same as the method in Embodiment 1, except that in step 1), polyethylene glycol is used instead of isobutylene-maleic anhydride copolymer. The final obtained superelastic ceramic single crystal particles have a size of 2.8±1.2 μm, an austenite mass ratio of 85.2%, and a Ce content of 0.137±0.005. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass ratio in the superelastic ceramic single crystal particles is 80.4%. The preparation yield is 82.1%. The final obtained superelastic ceramic single crystal particles contain Ce... 0.14 Zr 0.86 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0068] Example 5

[0069] This embodiment provides a superelastic ceramic single crystal particle (Ce). 0.12 Zr 0.88The preparation method of CeO2 is basically the same as that in Example 1, except that in step 1), 11.20 g of CeO2 powder (50 nm particle size) and 58.80 g of ZrO2 powder (50 nm particle size) are weighed and dissolved in 35 g of ultrapure water. The resulting superelastic ceramic single crystal particles have a size of 3.7 ± 0.3 μm, an austenite mass ratio of 47.2%, and a Ce content of 0.121 ± 0.001. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass ratio in the superelastic ceramic single crystal particles is 42.0%. The preparation yield is 44.1%. The final obtained superelastic ceramic single crystal particles contain Ce... 0.12 Zr 0.88 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0070] Example 6

[0071] This embodiment is basically the same as Embodiment 3, except that step 4) in this embodiment uses ball milling at 200 rpm for 10 hours instead of grinding to disperse the single crystal particles. The size of the superelastic ceramic single crystal particles is 1.5±0.8μm, the mass ratio of austenite is 72%, and the Ce content is 0.157±0.005. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the mass ratio of austenite in the superelastic ceramic single crystal particles is 73.8%. The preparation yield is 63.2%. The final obtained superelastic ceramic single crystal particles contain Ce. 0.16 Zr 0.84 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0072] Example 7

[0073] This embodiment is basically the same as the method in Embodiment 1, except that in step 3), the temperature is increased to 750℃ at 3℃ / min, held for 1 hour to remove the binder, and then increased to 1750℃ at 10℃ / min and held for 15 minutes. The resulting superelastic ceramic single crystal particles have a size of 4.2±0.9μm, an austenite mass ratio of 84.2%, and a Ce content of 0.137±0.007. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass ratio in the superelastic ceramic single crystal particles is 78.0%. The yield is 79.2%. The final obtained superelastic ceramic single crystal particles contain Ce... 0.14 Zr 0.86 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0074] Comparative Example 1

[0075] The method used in this comparative example is basically the same as that in Example 1, except that isobutylene-maleic anhydride copolymer is not added in step 1). The final size of the superelastic ceramic single crystal particles obtained is 2.4 ± 1.3 μm; the mass percentage of austenite in these superelastic ceramic single crystal particles is 73.2%, and they contain CeO2 and Ce2Zr2O. 7 / 8 Impurity phase; the atomic molar ratio of Ce in the superelastic ceramic single crystal particles is 0.132±0.037; after 20 cycles of liquid nitrogen temperature-room temperature cycling, the mass percentage of austenite in the superelastic ceramic single crystal particles is 47.5%. The preparation yield is 42.1%. The finally obtained superelastic ceramic single crystal particles Ce 0.14 Zr 0.86 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0076] Comparative Example 2

[0077] The method in this comparative example is basically the same as that in Example 2, except that step 2) of the drying and sieving process is omitted. Ultimately, the superelastic ceramic cannot be broken down by grinding. Superelastic ceramic single crystal particles Y 0.03 Zr 0.97 The yield of O2 preparation was ~0%. The final obtained superelastic ceramic single-crystal particles Y 0.03 Zr 0.97 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0078] Comparative Example 3

[0079] The method used in this comparative example is basically the same as that in Example 1, except that in step 3), the temperature is increased to 750°C at 3°C / min, held for 1 hour to remove the binder, and then increased to 1300°C at 10°C / min and held for 15 minutes. The resulting superelastic ceramic single crystal particles have a size of 0.3±0.2 μm, an austenite mass percentage of 38.4%, and a Ce content of 0.139±0.002. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass percentage in the superelastic ceramic single crystal particles is 32.1%. The yield is 24.5%. The final obtained superelastic ceramic single crystal particles have a Ce content of [missing information]. 0.14 Zr 0.86 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0080] Comparative Example 4

[0081] This embodiment provides a ceramic single crystal particle (Y) 0.01 Zr 0.99The preparation method of O2) is basically the same as that in Example 2, except that in this example, in step 1), 1.28 g of Y2O3 powder (particle size 50 nm) and 138.72 g of ZrO2 powder (particle size 50 nm) are weighed and dissolved in 70 g of ethanol. The final ceramic single crystal particles have a size of 1.0 ± 0.2 μm, an austenite mass percentage of 0%, and a Y content of 0.010 ± 0.002. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the austenite mass percentage in the ceramic single crystal particles is 0%. These ceramic particles do not possess superelastic properties, therefore the preparation yield is 0%. The final obtained ceramic single crystal particles Y2O3... 0.01 Zr 0.99 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0082] Comparative Example 5

[0083] The method used in this comparative example is basically the same as that in Example 3, except that in this example, after passing the material through a 200-mesh sieve in step 4), annealing is not performed. The size of the superelastic ceramic single crystal particles is 2.5±0.1μm, the mass percentage of austenite is 56.2%, and the Ce content is 0.160±0.005. After 20 cycles of liquid nitrogen temperature-room temperature cycling, the mass percentage of austenite in the superelastic ceramic single crystal particles is 54.3%. The preparation yield is 58.1%. The final obtained superelastic ceramic single crystal particles contain Ce. 0.16 Zr 0.84 The composition, properties, and preparation yield of O2 are listed in Table 1.

[0084] Table 1. Composition and properties of superelastic single-crystal ceramics, and preparation yield.

[0085]

[0086] As can be seen from the comparison of the results of Examples 1 and 4 with Comparative Example 1 in Table 1, the isobutylene-maleic anhydride copolymer modifier is beneficial to improving the size and compositional uniformity of single crystal particles, as well as the austenite content in the prepared state, thereby obtaining better reversible superelasticity.

[0087] As can be seen from the comparison of the results of Example 2 and Comparative Example 2, the drying and sieving process is beneficial for separating composite cross-linked particles at the micron scale, which not only protects the uniformity of the components, but also facilitates subsequent grinding and single crystallization.

[0088] The results of Examples 3 and 6 and Comparative Example 5 show that using a grinding process instead of a ball milling process for single crystallization and subsequent long-term annealing can minimize the impact of mechanical stress on single crystal particles, which is beneficial to further maintain the original size and size uniformity of single crystal particles and obtain good reversible superelasticity.

[0089] A comparison of Examples 1 and 7 and 8 shows that a suitable sintering temperature is beneficial for obtaining particles with uniform composition and size and good superelasticity.

[0090] The results of Examples 1 and 5, and Examples 2 and Comparative Example 3 show that a suitable dopant content is beneficial to obtaining better reversible superelasticity.

[0091] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing superelastic ceramic single crystal particles, characterized in that, Includes the following steps: A1. Modification and Dispersion: Weigh the oxide powder of element N and zirconium oxide powder according to the proportion, add solvent, and mechanically ball mill at 200-300 rpm to obtain a uniformly mixed slurry; then add modifier, and continue ball milling at 300-400 rpm for a period of time to obtain a well dispersed gel-like slurry; A2. Drying and sieving: Place the gel-like slurry obtained in step A1 in a ventilated environment at 50-100°C and dry for 6-12 hours. Then, sieve it through a 50-200 mesh screen to obtain the composite modified powder. A3. Two-step sintering: The composite modified powder obtained in step A2 is heated to 700-800°C in air at 3-5°C / min, held for 1-3 h to remove the binder, and then heated to 1350-1750°C at 5-10°C / min and held for 15-30 min. After cooling to room temperature, superelastic ceramic polycrystalline particles are obtained. A4. Grinding and Single Crystallization: After ball milling or grinding the polycrystalline particles of superelastic ceramics, pass them through a 200-500 mesh sieve and anneal them at 600-800°C for 4-6 hours to obtain single crystal particles of superelastic ceramics. In step A1, the element N is one of Ce, Y, Mg, and Ca; The modifier is one or a mixture of several of the following: isobutylene-maleic anhydride copolymer, acrylamide, sodium dodecyl sulfate, fatty amine, polyvinyl alcohol, diethanolamine, triethanolamine, N-alkyldiethyltriamine, and formamide.

2. The method for preparing superelastic ceramic single crystal particles according to claim 1, characterized in that, In step A1, the particle size of the oxide powder of element N and the zirconium oxide powder is less than 100 nm. The solvent is one or a mixture of several of the following: water, ethanol, propanol, isopropanol, acetone, and butanone.

3. The method for preparing superelastic ceramic single crystal particles according to claim 1 or 2, characterized in that, In step A1, the content of element N in the superelastic ceramic single crystal particles is 2-18 mol.%.

4. The method for preparing superelastic ceramic single crystal particles according to claim 1 or 2, characterized in that, In step A1, the total weight ratio of the oxide powder of element N and the zirconium oxide powder to the solvent is (2-1):

1.

5. The method for preparing superelastic ceramic single crystal particles according to claim 1, characterized in that, In step A1, the weight ratio of the modifier to the solvent is (0.2%-2%):

1.

6. The method for preparing superelastic ceramic single crystal particles according to claim 5, characterized in that, In step A1, the modifier is an isobutylene-maleic anhydride copolymer.

7. A superelastic ceramic single-crystal particle prepared by the method according to any one of claims 1-6, characterized in that, The compositional expression of the superelastic ceramic single crystal particles is: N x Zr 1-x O2; Wherein, N is at least one of Ce, Y, Mg, and Ca, and x is the atomic molar ratio, 0.02≤x≤0.18; The particle size of the superelastic ceramic single crystal particles is 0.2-5 μm.

8. The superelastic ceramic single crystal particles according to claim 7, characterized in that, When N is Ce, 0.14 ≤ x ≤ 0.18; When N is Y, 0.02≤x≤0.

04.

9. The superelastic ceramic single crystal particles according to claim 7, characterized in that, The prepared state austenite content of the superelastic ceramic single crystal particles is higher than 80%.

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