Method for preparing submillimeter zirconia microspheres

Abstract

The invention provides a method for preparing submillimeter zirconia microspheres, and belongs to the technical field of ceramic materials. According to the method, in the settling process of the ceramic slurry in an oily medium, molecules of a two-phase interface layer (a water phase and an oil phase) are subjected to two-phase asymmetric acting force, so that the interface layer presents a spherical surface, and spherical slurry is formed. The preparation method comprises the following steps: introducing an acrylamide gel system into ceramic slurry, and initiating a polymerization reaction of the gel system when the ceramic slurry is spherically settled, so that in-situ solidification occurs while the slurry is spherical, thereby obtaining a zirconium oxide microbead green body. The low-activity initiator VA-044 is added, and the slurry is controlled to be cured in an oily medium through the temperature in the silicone oil, so that the addition of more organic matters (such as a catalyst and a photoinitiator) is avoided, and the compactness and hardness of the microbeads are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and particularly relates to a method for preparing sub-millimeter zirconia microspheres. Background Art

[0002] With the development of synthetic chemical raw materials and special preparation processes, the ceramic materials have made great leaps and formed many new functional ceramic industries. Among them, the ore grinding operation is one of the important stages in the ceramic industry, and ceramic grinding media are used in the grinding operation of the ceramic industry. Zirconia microspheres are grinding beads used to grind "zero pollution" and ultra-fine powders with high viscosity and high hardness. Compared with other grinding media such as alumina beads, zirconium silicate beads, agate beads, and glass beads, zirconia grinding beads have obvious advantages in terms of grinding efficiency and grinding accuracy. Zirconia microspheres have excellent grinding performance and are widely used in aviation, chemical industry, medical treatment, paints, coatings, and pesticides. Especially in the grinding of battery materials.

[0003] At present, the preparation processes of ceramic microspheres use the sol-gel forming method and the rolling forming method, and the two processes cannot simultaneously have the characteristics of large bulk density, high strength and hardness, and excellent stability. The traditional gel-casting forming process uses highly active ammonium persulfate initiators. If the addition amount is too much, the slurry will solidify in advance; if the addition amount is too little, the solidification speed of the slurry is too slow to form microspheres in silicone oil, and then additional catalysts need to be added, resulting in too much organic matter added and it is difficult to ensure the densification of ceramics, which limits the use of zirconia microspheres. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing sub-millimeter zirconia microspheres. The method of the present invention avoids the problem of excessive addition of catalysts by adding low-activity initiators, and improves the structural densification of zirconia ceramic microspheres.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention, a method for preparing sub-millimeter zirconia microspheres, includes the following steps:

[0007] Step 1. Dissolve acrylamide, N-N'-methylenebisacrylamide, a dispersant, and a defoamer in water to obtain Solution 1;

[0008] Step 2. Adjust the pH of Solution 1 to be alkaline, and then add zirconia powder to obtain a premixed solution;

[0009] Step 3. Ball-mill the premixed solution, and then add an initiator and ball-mill again to obtain a zirconia slurry;

[0010] Step 4. Defoam the zirconia slurry and then add it to methyl silicone oil. Automatically form spheres under stirring conditions and carry out a polymerization reaction to obtain a green body of zirconia ceramic microspheres.

[0011] Step 5. Wash and dry the green body of the zirconia ceramic microspheres, then carry out debinding and sintering, and then carry out self-grinding to obtain sub-millimeter-sized zirconia microspheres.

[0012] The initiator is an azoamidine initiator VA-044.

[0013] In a preferred embodiment of the present invention, the mass ratio of the zirconia powder to acrylamide is 1:(0.02 - 0.06); the mass ratio of acrylamide to N,N'-methylenebisacrylamide is (16 - 24):1, the mass ratio of the zirconia powder to ammonium citrate is 1:(0.001 - 0.006); the mass ratio of the zirconia powder to water is 100:(30 - 40); the dispersant is ammonium citrate; the defoaming agent is isopropanol. In the present invention, adding ammonium citrate as a dispersant can improve the fluidity of the slurry, and adding isopropanol as a defoaming agent to remove air bubbles.

[0014] In a preferred embodiment of the present invention, the zirconia powder is yttria-stabilized zirconia powder. Further preferably, it is 3mol% yttria-stabilized zirconia, which can be obtained by commercial purchase.

[0015] In the present invention, if the addition amounts of acrylamide and N,N'-methylenebisacrylamide are too small, no gel will be produced and microspheres cannot be formed. If the addition amounts are too large, the compactness will be affected. Whether the addition amount of ammonium citrate is too much or too little will affect the fluidity of the slurry.

[0016] The present invention does not make special requirements for the dosage of the defoaming agent, and the dosage of the defoaming agent is sufficient to achieve the defoaming purpose.

[0017] In a preferred embodiment of the present invention, the pH value is 10 - 12.

[0018] In a preferred embodiment of the present invention, the alkali solution used to adjust the pH to 10 - 12 is sodium hydroxide solution.

[0019] In a preferred embodiment of the present invention, when ball-milling the premixed liquid, the rotation speed of ball-milling is 400 - 500 r / min and the time is 4 - 6 h; when ball-milling again after adding the initiator, the rotation speed of ball-milling is 200 r / min and the time is 40 min.

[0020] In a preferred embodiment of the present invention, the mass ratio of acrylamide to the initiator is 1:(0.02 - 0.06).

[0021] In a preferred embodiment of the present invention, the specific operation of defoaming the zirconia slurry is as follows: the zirconia slurry is placed in a vacuum drying oven to evacuate air bubbles, and after vacuum defoaming, a zirconia slurry with a high solid content and low viscosity is obtained.

[0022] In a preferred embodiment of the present invention, the temperature of the methyl silicone oil is 80 - 120 °C.

[0023] In a preferred embodiment of the present invention, when the defoamed zirconia slurry is added to the methyl silicone oil, the flow rate is 0.1 - 0.5 ml / min; during the process of automatic ball formation under stirring conditions, the stirring speed is 600 - 800 r / min.

[0024] In a preferred embodiment of the present invention, the parameters for debinding are set as follows: heating to 240 °C at a rate of 2 - 5 °C / min, then holding for 1 - 2 h, then heating to 600 °C at a rate of 2 - 5 °C / min, and holding for 1 - 2 h; the parameters for sintering are set as follows: after debinding, heating to 1200 °C at a rate of 5 °C / min, holding for 1 h, and finally heating to 1500 - 1550 °C at a rate of 5 °C / min, and holding for 1 - 4 h.

[0025] In the present invention, if the sintering temperature and heating program are not within the above ranges, the densification of the zirconia microspheres will be reduced.

[0026] In a preferred embodiment of the present invention, the parameters for debinding are set as follows: heating to 240 °C at a rate of 5 °C / min, then holding for 1 h, then heating to 600 °C at a rate of 5 °C / min, and holding for 1 h; the parameters for sintering are set as follows: after debinding, heating to 1200 °C at a rate of 5 °C / min, holding for 1 h, and finally heating to 1500 - 1525 °C at a rate of 5 °C / min, and holding for 3 h.

[0027] The second technical solution of the present invention is a sub - millimeter - sized zirconia microsphere prepared by the above - mentioned preparation method.

[0028] The present invention discloses the following technical effects:

[0029] By adding a low - activity initiator and controlling the temperature in the silicone oil to cure the slurry in an oily medium, the present invention avoids the addition of more organic substances (such as catalysts and photo - initiators), thereby improving the densification and hardness of the microspheres.

[0030] By adjusting the rotation speed and flow rate, the present invention can make the particle size of the zirconia ceramic microspheres reach the sub - millimeter level. Description of the Drawings

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0032] Figure 1 It is a green body diagram of zirconia microspheres obtained in Example 1 in a microscope;

[0033] Figure 2 It is a green body diagram of zirconia microspheres obtained in Example 2 in a microscope;

[0034] Figure 3 It is a green body diagram of zirconia microspheres obtained in Example 3 in a microscope;

[0035] Figure 4 It is a green body diagram of zirconia microspheres obtained in Comparative Example 1 in a microscope;

[0036] Figure 5 It is an SEM image (1.0 mm) of zirconia microspheres obtained in Example 1;

[0037] Figure 6 It is an SEM image (200 μm) of zirconia microspheres obtained in Example 1. Detailed Embodiments

[0038] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0039] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0042] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, that is, they are intended to include but not limited to.

[0043] During the sedimentation of the ceramic slurry in the oily medium, the molecules in the two-phase interface layer (aqueous phase and oil phase) are subjected to asymmetric forces from the two phases, causing the interface layer to present a spherical surface and forming a spherical slurry. An acrylamide gel system is introduced into the ceramic slurry, and then the polymerization reaction of the gel system is initiated when the ceramic slurry settles in a spherical shape, so that the slurry solidifies in situ while being spherical, and thus a green body of zirconia microspheres can be obtained.

[0044] The method for preparing sub-millimeter zirconia ceramic microspheres provided by the present invention uses acrylamide as a monomer, adds a cross-linking agent and a dispersant to form a mixed solution with yttrium-stabilized zirconia powder; at the same time, a low-activity azoamidine initiator VA-044 is added to form a slurry; the prepared zirconia slurry is dropped into the oily medium through a micro-injection pump and stirred to form a spherical green body of microspheres, and then the green body of zirconia microspheres is separated from the oily medium, washed, dried, debound, and sintered to make zirconia ceramic microspheres. The zirconia slurry is initiated to gel polymerization by adding a low-activity initiator (azoamidine initiator VA-044), and this initiator can perform a smooth, stable, and controllable decomposition reaction to produce a polymer with high linearity and high molecular weight. It avoids the problems of premature curing of the slurry caused by excessive addition of traditional ammonium persulfate initiators, long curing time of the slurry with too little addition and the need to additionally add a catalyst or use UV light curing, reducing the problems of high operation difficulty and excessive addition of organic substances.

[0045] The present invention controls the size of the microspheres by adjusting the flow rate of the micro-injection pump and the rotation speed of the stirring paddle to form a shear force on the slurry, thereby refining the slurry.

[0046] The size of the zirconia microspheres prepared by the present invention is 0.2 - 0.3 mm.

[0047] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0048] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments only.

[0049] Example 1

[0050] A method for preparing sub-millimeter zirconia microspheres comprises the following steps:

[0051] Step 1: Dissolve 1.5 g of acrylamide, 0.070 g of N,N'-methylenebisacrylamide, and 0.1 g of ammonium citrate in 11.20 g of deionized water, add 0.15 g of isopropanol to form a solution, and adjust the pH value of the solution to 12 by dropping sodium hydroxide solution; at the same time, stir magnetically for 10 min, and add 30 g of 3 mol% yttria-stabilized zirconia powder to the solution to obtain a premixed solution.

[0052] Step 2: Ball-mill the above premixed solution at a rotation speed of 400 r / min for 4 h; after ball-milling, add 0.056 g of initiator VA-044, and continue to ball-mill at a rotation speed of 200 r / min for 40 min to obtain a zirconia slurry.

[0053] Step 3: Place the obtained zirconia slurry in a vacuum drying oven to evacuate and remove air bubbles to obtain a zirconia slurry with a high solid content and low viscosity.

[0054] Step 4: Place 500 ml of methyl silicone oil in a beaker, and place the beaker in an oil bath at 110 °C. Place the zirconia slurry prepared in Step 3 into a micro-injection pump, and at the same time connect a hose with a pinhole to the micro-injection pump. Turn on the switch of the micro-injection pump, adjust the flow rate to 0.3 ml / min. Under the thrust of the injection pump, the zirconia slurry droplets drip from the pinhole into the methyl silicone oil, and at the same time stir magnetically, adjust the rotation speed of the stirring paddle to 500 r / min; the dropped zirconia slurry is refined into smaller droplets under the action of centrifugal force. At the same time, the acrylamide gel system undergoes a polymerization reaction to form a green body of zirconia ceramic microspheres.

[0055] Step 5: Take out the green body of the microspheres, wash it 3 times with absolute ethanol first, and then wash it with clear water; after washing, place it in a drying oven and dry it at 70 °C for 15 h to obtain a green body of ceramic microspheres.

[0056] Step 6: Place the green body of the ceramic microspheres in a muffle furnace and raise the temperature to 240 °C at a rate of 5 °C / min, then hold for 1 h, then raise the temperature to 600 °C at a rate of 5 °C / min, hold for 1 h, then raise the temperature to 1200 °C at a rate of 5 °C / min, hold for 1 h, and raise the temperature to 1500 °C at a rate of 5 °C / min, hold for 3 h to obtain zirconia ceramic microspheres.

[0057] Step 7: Place the obtained zirconia ceramic microspheres in a planetary ball mill and grind them self at 400 r / min for 6 h to obtain zirconia microspheres with good sphericity and smooth surface.

[0058] Example 2

[0059] A method for preparing sub-millimeter zirconia microspheres comprises the following steps:

[0060] Step 1: Dissolve 1.6 g of acrylamide, 0.08 g of N,N'-methylenebisacrylamide, and 0.12 g of ammonium citrate in 14.54 g of deionized water, add 0.16 g of isopropanol to form a solution, and adjust the pH value of the solution to 12 by dropping sodium hydroxide solution; simultaneously, stir magnetically for 10 min, and add 40 g of 3 mol% yttria-stabilized zirconia powder to the solution to obtain a premixed solution.

[0061] Step 2: Ball-mill the above premixed solution at a rotation speed of 400 r / min for 4 h; after the ball-milling is completed, add 0.078 g of initiator VA-044, and continue to ball-mill at a rotation speed of 200 r / min for 40 min to obtain a zirconia slurry.

[0062] Step 3: Place the obtained zirconia slurry in a vacuum drying oven to evacuate and remove air bubbles to obtain a zirconia slurry with a high solid content and low viscosity.

[0063] Step 4: Place 500 ml of methyl silicone oil in a beaker, and place the beaker in an oil bath at 105 °C. Place the zirconia slurry prepared in Step 3 in a micro-injection pump, and at the same time connect a hose with a pinhole to the micro-injection pump. Turn on the switch of the micro-injection pump, adjust the flow rate to 0.3 ml / min. Under the thrust of the injection pump, the zirconia slurry droplets are dropped from the pinhole into the methyl silicone oil, and at the same time stir magnetically, and adjust the rotation speed of the stirring paddle to 550 r / min; the dropped zirconia slurry is refined into smaller droplets under the action of centrifugal force. At the same time, the acrylamide gel system undergoes a polymerization reaction to form a green body of zirconia ceramic microspheres.

[0064] Step 5: Take out the green body of the microspheres, wash it 3 times with anhydrous ethanol first, and then wash it with clear water; after washing, place it in a drying oven and dry it at 70 °C for 15 h to obtain a green body of ceramic microspheres.

[0065] Step 6: Place the green body of the ceramic microspheres in a muffle furnace, raise the temperature to 240 °C at a rate of 5 °C / min, then hold for 1 h, then raise the temperature to 600 °C at a rate of 5 °C / min, hold for 1 h, then raise the temperature to 1200 °C at a rate of 5 °C / min, hold for 1 h, and raise the temperature to 1520 °C at a rate of 5 °C / min, hold for 3 h to obtain zirconia ceramic microspheres.

[0066] Step 7: Place the obtained zirconia ceramic microspheres in a planetary ball mill and grind them self at 400 r / min for 6 h to obtain zirconia microspheres with good sphericity and smooth surface.

[0067] Example 3

[0068] A method for preparing sub-millimeter zirconia microspheres comprises the following steps:

[0069] Step 1: Dissolve 2.25 g of acrylamide, 0.11 g of N,N'-methylenebisacrylamide, and 0.15 g of ammonium citrate in 16.93 g of deionized water, add 0.2 g of isopropanol to form a solution, and adjust the pH value of the solution to 11 by dropping sodium hydroxide solution; at the same time, magnetically stir for 10 min, and add 50 g of 3 mol% yttria-stabilized zirconia powder to the solution to obtain a premixed solution.

[0070] Step 2: Ball-mill the above premixed solution at a rotation speed of 400 r / min for 4 h; after the ball-milling is completed, add 0.087 g of initiator VA-044, and continue to ball-mill at a rotation speed of 200 r / min for 40 min to obtain a zirconia slurry.

[0071] Step 3: Place the obtained zirconia slurry in a vacuum drying oven to evacuate and remove air bubbles to obtain a zirconia slurry with a high solid content and low viscosity.

[0072] Step 4: Place 500 ml of methyl silicone oil in a beaker and place the beaker in an oil bath at 110 °C. Place the zirconia slurry prepared in Step 3 into a micro-injection pump, and at the same time connect a hose with a pinhole to the micro-injection pump. Turn on the switch of the micro-injection pump, adjust the flow rate to 0.3 ml / min. Under the thrust of the injection pump, the zirconia slurry droplets drip from the pinhole into the methyl silicone oil, and at the same time, magnetically stir, and adjust the rotation speed of the stirring paddle to 500 r / min; the dropped zirconia slurry is refined into smaller droplets under the action of centrifugal force. At the same time, the acrylamide gel system undergoes a polymerization reaction to form a green body of zirconia ceramic microspheres.

[0073] Step 5: Take out the green body of the microspheres, first wash it 3 times with anhydrous ethanol, and then wash it with clean water; after washing, place it in a drying oven and dry it at 70 °C for 15 h to obtain a green body of ceramic microspheres.

[0074] Step 6: Place the green body of the ceramic microspheres in a muffle furnace and heat it to 240 °C at a rate of 5 °C / min, then hold for 1 h, then heat it to 600 °C at a rate of 5 °C / min, hold for 1 h, then heat it to 1200 °C at a rate of 5 °C / min, hold for 1 h, and heat it to 1525 °C at a rate of 5 °C / min and hold for 3 h to obtain zirconia ceramic microspheres.

[0075] Step 7: Place the obtained zirconia ceramic microspheres in a planetary ball mill and self-mill them at 400 r / min for 6 h to obtain zirconia microspheres with good sphericity and smooth surface.

[0076] Comparative Example 1

[0077] Step 1: Dissolve 3.5 g of acrylamide, 0.11 g of N-N'-methylenebisacrylamide, and 0.35 g of ammonium citrate in 16.50 g of deionized water. Add 0.2 g of isopropanol to form a solution, and adjust the pH value of the solution to 11 by dropping sodium hydroxide solution. At the same time, magnetically stir for 10 min, and add 50 g of 3 mol% yttria-stabilized zirconia powder to the solution to obtain a premixed solution.

[0078] Step 2: Ball-mill the above premixed solution at a rotation speed of 400 r / min for 4 h. After ball-milling, add 0.087 g of initiator VA-044, and continue to ball-mill at a rotation speed of 200 r / min for 40 min to obtain a zirconia slurry.

[0079] Step 3: Place the obtained zirconia slurry in a vacuum drying oven to evacuate and remove air bubbles, obtaining a zirconia slurry with a high solid content and low viscosity.

[0080] Step 4: Place 500 ml of methyl silicone oil in a beaker, and place the beaker in an oil bath at 110 °C. Place the zirconia slurry prepared in Step 3 into a micro-injection pump, and at the same time connect a hose with a pinhole to the micro-injection pump. Turn on the switch of the micro-injection pump, adjust the flow rate to 0.3 ml / min. Under the thrust of the injection pump, the zirconia slurry droplets drip from the pinhole into the methyl silicone oil, and at the same time magnetically stir, adjusting the rotation speed of the stirring paddle to 500 r / min; the dropped zirconia slurry is refined into smaller droplets under the action of centrifugal force. At the same time, the acrylamide gel system undergoes a polymerization reaction to form a green body of zirconia ceramic microspheres.

[0081] Step 5: Take out the green body of the microspheres, first wash it 3 times with anhydrous ethanol, and then wash it with clear water; after washing, place it in a drying oven and dry it at 70 °C for 15 h to obtain a green body of ceramic microspheres.

[0082] Step 6: Place the green body of the ceramic microspheres in a muffle furnace, heat it to 240 °C at a rate of 5 °C / min, then hold for 1 h, then heat it to 600 °C at a rate of 5 °C / min, hold for 1 h, then heat it to 1200 °C at a rate of 5 °C / min, hold for 1 h, and heat it to 1475 °C at a rate of 5 °C / min, hold for 3 h to obtain zirconia ceramic microspheres.

[0083] Step 7: Place the obtained zirconia ceramic microspheres in a planetary ball mill and self-mill them at 400 r / min for 6 h to obtain zirconia microspheres with good sphericity and smooth surface. (That is, different from Example 3 in that the proportion of raw materials in Step 1 is different)

[0084] Table 1 shows the sphericity, density, and relative density of zirconia microspheres in different examples and comparative examples.

[0085] Table 1

[0086] Particle size <![CDATA[Density (g / cm 3 )]]> Sphericity Density (%) Hardness (Hv) Example 1 0.2 - 0.3 mm 6.017 0.99 98.96 1350 Example 2 0.2 - 0.3 mm 6.024 0.98 99.07 1350 Example 3 0.1 - 0.3 mm 6.028 0.98 99.14 1350 Comparative Example 1 0.3 - 0.4 mm 5.818 0.90 95.69 1150

[0087] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing submillimeter zirconia microbeads, characterized in that: The following steps are involved: Step 1. dissolving acrylamide, N-N'-methylenebisacrylamide, a dispersant and a defoaming agent in water to obtain a solution 1; Step 2. adjusting the pH of the solution 1 to be alkaline, and then adding zirconium oxide powder to obtain a premixed solution; Step 3. ball milling the premixed solution, then adding an initiator and further ball milling to obtain a zirconium oxide slurry; Step 4. After degassing, the zirconium oxide slurry is added to methyl silicone oil, and the slurry is automatically balled under stirring conditions, and a polymerization reaction is performed to obtain a green body of zirconium oxide ceramic microbeads; Step 5. After cleaning and drying the zirconia ceramic microbead green body, debinding and sintering are performed, and then autogenously grinding is performed to obtain sub-millimeter zirconia microbeads; The initiator is azo amidine initiator VA-044.

2. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: The mass ratio of the zirconium oxide powder to acrylamide is 1:(0.02-0.06); the mass ratio of acrylamide to N-N'-methylenebisacrylamide is (16-24):1; the mass ratio of the zirconium oxide powder to the dispersant is 1:(0.001-0.006); the mass ratio of the zirconium oxide powder to water is 100:(30-40); the dispersant is ammonium citrate; and the defoaming agent is isopropyl alcohol.

3. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: The pH value is 10-12.

4. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: When the premixed liquid is ball-milled, the speed of the ball mill is 400-500 r / min, and the time is 4-6 h; when the initiator is added and then ball-milled, the speed of the ball mill is 200 r / min, and the time is 40 min.

5. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: The mass ratio of the acrylamide to the initiator is 1:(0.02-0.06).

6. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: The temperature of the methyl silicone oil is 80-120°C.

7. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: When the zirconium oxide slurry is defoamed and added to the methyl silicone oil, the flow rate is 0.1-0.5 ml / min; during the automatic balling process under stirring conditions, the stirring speed is 600-800 r / min.

8. The method for preparing submillimeter zirconia microbeads according to claim 1, characterized in that: The debinding parameters are set as follows: raising the temperature to 240°C at 2-5°C / min, then keeping warm for 1-2h, then raising the temperature to 600°C at 2-5°C / min, and keeping warm for 1-2h; the sintering parameters are set as follows: after debinding, raising the temperature to 1200°C at 5°C / min, keeping warm for 1h, and finally raising the temperature to 1500-1550°C at 5°C / min, and keeping warm for 1-4h.

9. Sub-millimeter zirconia microbeads prepared by the preparation method according to any one of claims 1 to 8.

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