Preparation method of submillimeter zirconia microspheres

Abstract

The invention relates to the technical field of ceramic materials, in particular to a preparation method of submillimeter zirconia microspheres. The preparation method comprises the following steps: adding an isobutylene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate into water, then adjusting the pH value of the solution to be alkaline by using an alkaline solution, and adding a defoaming agent and yttria-stabilized zirconia powder to obtain a premixed solution; carrying out ball milling on the premixed liquid, and then carrying out vacuum bubble removal to obtain zirconium oxide slurry; injecting the zirconium oxide slurry into an oily medium to obtain a zirconium oxide ceramic microbead green body; cleaning the zirconia ceramic microbead green body, drying, carrying out gradient heating calcination, and carrying out autogenous grinding to obtain the submillimeter zirconia microbead; the gel microspheres can be formed only by adding three organic matters, and the gel microspheres are low in organic matter content and free of toxicity. The method disclosed by the invention is high in yield, simple to operate and low in cost, and the prepared zirconium oxide microbeads are uniform in particle size and have relatively high density and mechanical properties.

Description

Technical Field

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

[0002] Zirconia beads are made from micron-sized and sub-nanometer-sized zirconia and yttrium oxide, and are a kind of grinding beads used for ultra-fine grinding and dispersion of materials that require "zero pollution" and have high viscosity and high hardness. Zirconia ceramic microspheres not only have excellent properties of ceramic materials, but also have many advantages of microsphere particles due to their spherical shape, making them widely used in many fields such as the nuclear industry, biology, medicine, chemical industry, military, and environmental protection. People's research on ceramic microspheres is becoming more and more in-depth, and there are more and more preparation methods. However, these preparation methods all have one or two disadvantages, and it is very difficult to prepare ceramic microspheres with high strength, good sphericity, uniform particle size distribution, and controllable size. Therefore, domestic and foreign scholars have developed different methods to prepare ceramic microspheres with different compositions and structures for different application fields and different materials. According to the principle of forming spheres, they are mainly divided into: methods of forming spheres using crystallography principles (such as the sol-gel method), methods of forming spheres through mechanical forces such as extrusion, friction, and collision (such as the rolling method, etc.), and methods of forming spheres using the principle of surface tension.

[0003] At present, the preparation process of ceramic microspheres uses the sol-gel forming method and the rolling forming method, and the two processes cannot simultaneously have the characteristics of large volume density, high strength and hardness, and excellent stability. The traditional gel-casting forming process uses an acrylamide system. This system has a large number of organic substances (including monomers, cross-linking agents, dispersants, initiators, catalysts), which easily leads to the formation of gas during the sintering process, leaving porosity and affecting the ceramic density. Acrylamide itself as a monomer is toxic and will cause the problem of oxygen inhibition polymerization (a layer will peel off on the surface of the prepared ceramic microspheres). In addition, due to too many organic substances, more heat preservation time is required during the debinding process to discharge the organic substances in the form of gas.

[0004] How to reduce the usage amount of organic substances in the preparation process of zirconia beads and improve the structural denseness of zirconia beads is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing sub-millimeter zirconia microspheres.

[0006] To achieve the above object, the present invention provides the following scheme:

[0007] The present invention provides a method for preparing sub-millimeter zirconia microspheres, comprising the following steps:

[0008] Add isobutylene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate into water, then adjust the pH of the solution to alkaline with an alkali solution, add an antifoaming agent and yttria-stabilized zirconia powder to obtain a premixed solution;

[0009] Ball-mill the premixed solution, and then remove air bubbles under vacuum to obtain a zirconia slurry;

[0010] Inject the zirconia slurry into an oily medium to form a green body of zirconia ceramic microspheres;

[0011] After cleaning the green body of zirconia ceramic microspheres, perform drying, gradient temperature calcination, and then self-grinding to obtain sub-millimeter-sized zirconia microspheres;

[0012] The addition amount of the isobutylene-maleic anhydride copolymer is 0.3 wt% - 0.6 wt% of the mass of the yttria-stabilized zirconia powder;

[0013] The addition amount of the butyl glycidyl ether is 0.2 wt% - 0.6 wt% of the mass of the yttria-stabilized zirconia powder;

[0014] The addition amount of the ammonium citrate is 0.1 wt% - 0.4 wt% of the mass of the yttria-stabilized zirconia powder;

[0015] The mass ratio of the yttria-stabilized zirconia powder to deionized water is 5:(1.5 - 2.5);

[0016] The volume concentration of the antifoaming agent in the premixed solution is 0.5% - 1%.

[0017] In the present invention, if the addition amount of the isobutylene-maleic anhydride copolymer is too much, it will lead to too high viscosity and poor fluidity, and if the addition amount is too little, it will lead to too slow gelation rate. Therefore, the present invention preferably limits the addition amount of the isobutylene-maleic anhydride copolymer to 0.3 wt% - 0.6 wt% of the mass of the yttria-stabilized zirconia powder.

[0018] During the sedimentation of the zirconia 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, so that the interface layer presents a spherical surface, forming a spherical slurry. Introducing an isobutylene-maleic anhydride copolymer gel system into the ceramic slurry can cause the polymerization reaction of the gel system when the zirconia 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.

[0019] By adding a low amount of organic matter, the structural compactness of the zirconia microspheres is improved; by adjusting the flow rate of the micro-injection pump and the rotation speed of the stirring paddle, the size of the zirconia ceramic microspheres can be controlled, and the preparation efficiency of the microspheres is greatly improved.

[0020] In a preferred embodiment of the present invention, the pH is 10 - 12.

[0021] In a preferred embodiment of the present invention, the ball milling time is 4 - 6 h, and the rotation speed is 400 - 500 r / min.

[0022] In a preferred embodiment of the present invention, the oily medium is methyl silicone oil.

[0023] In a preferred embodiment of the present invention, the temperature of the oily medium is 100 - 140 °C.

[0024] In the present invention, if the temperature of the oily medium is too high, the green body of zirconia microspheres will crack, and if the temperature is too low, the gelation rate will be too slow, affecting the sphericity. Therefore, the present invention preferably limits the temperature of the oily medium to the above parameter range.

[0025] In a preferred embodiment of the present invention, the injection flow rate is 0.3 mL / min.

[0026] In a preferred embodiment of the present invention, the oily medium is stirred during injection; the rotation speed of the stirring is 400 - 500 r / min.

[0027] By adjusting the flow rate when injecting zirconia slurry into the oily medium and the rotation speed of the oily medium in the present invention, the spheroid diameter of zirconia microspheres can reach the sub - millimeter level.

[0028] In a preferred embodiment of the present invention, the drying temperature is 50 - 70 °C, and the time is 15 h.

[0029] In a preferred embodiment of the present invention, the gradient temperature - rising calcination is specifically as follows: first, it is heated to 200 °C at a rate of 2 - 5 °C / min and kept warm for 1 - 2 h (the first stage), then heated to 600 °C at a rate of 2 - 5 °C / min and kept warm for 1 - 2 h (the second stage), then heated to 1200 °C at a rate of 5 °C / min and kept warm for 1 h (the third stage), and then heated to 1500 - 1550 °C at a rate of 5 °C / min and kept warm for 1 - 4 h (the fourth stage). In the present invention, the purpose of the gradient temperature - rising is to discharge water in the first stage, then discharge organic substances in the second stage, stabilize the crystal phase in the third stage, and sinter in the fourth stage.

[0030] The present invention discloses the following technical effects:

[0031] Compared with the prior art, the present invention only adds three organic substances, isobutene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate. By adding only 0.6-1.6 wt% of organic substances, green bodies of zirconia microspheres with high sphericity can be prepared. Compared with the existing methods for preparing zirconia microspheres, such as the acrylamide gel system (the addition amount of organic substances in the acrylamide system is generally 5.5-7 wt%), the addition amount of organic substances is reduced by 4-5 wt%. Moreover, the isobutene-maleic anhydride copolymer system is non-toxic and there is no problem of oxygen inhibition of polymerization. Due to the small addition amount of organic substances, the operation steps are simpler, the cost is lower, and it is more suitable for industrial production.

[0032] In the present invention, by introducing the isobutene-maleic anhydride copolymer system and adding ammonium citrate as a dispersant, the solid content of the zirconia slurry is increased by 5%-8%, and a zirconia slurry with a high solid content and low viscosity can be prepared. Adding butyl glycidyl ether can improve the green body strength of the zirconia microspheres.

[0033] The bulk density of the zirconia microspheres will gradually increase with the increase of the solid content of the zirconia slurry. The method of the present invention greatly improves the density and mechanical properties of the zirconia microspheres.

[0034] In the present invention, by controlling the temperature of the oily medium (methyl silicone oil), the solidification of the zirconia slurry in the oily medium is controlled, and no additional organic substances such as initiators and catalysts are added, thereby improving the density and mechanical properties of the microspheres. Brief Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the 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 drawings can also be obtained based on these drawings.

[0036] Figure 1 It is an optical microscope image of the green body of the zirconia ceramic microspheres prepared in Example 1 of the present invention.

[0037] Figure 2 It is the strength of the zirconia microspheres prepared in Example 1 of the present invention.

[0038] Figure 3 It is an optical microscope image of the green body of the zirconia ceramic microspheres prepared in Comparative Example 1 of the present invention.

[0039] Figure 4 It is an optical microscope image of the green body of the zirconia ceramic microspheres prepared in Comparative Example 2 of the present invention. Detailed Description of the Embodiments

[0040] The various exemplary embodiments of the present invention will be described in detail below. This detailed description should not be construed 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.

[0041] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended 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 may be independently included or excluded from the range.

[0042] 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 may 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 said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0043] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, 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 examples of the present invention are merely exemplary.

[0044] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0045] The present invention forms a mixed solution with isobutene - maleic anhydride copolymer, ammonium citrate, and butyl glycidyl ether and yttrium-stabilized zirconia powder; the prepared zirconia slurry is dropped into an oily medium and stirred to form a green body of microspheres, and then the green body of zirconia microspheres is separated from the oily medium, washed, dried, debinded (i.e., removing organic substances), and sintered to make zirconia microbeads. Compared with the previous methods for preparing zirconia microbeads, the present invention only needs to add three organic substances to form gel microspheres, and the content of organic substances is small and non-toxic. The finished product rate of the zirconia microspheres prepared by the method of the present invention is high, the operation is simple, the cost is low, the particle size of the prepared zirconia microbeads is uniform, and it has high density and mechanical properties.

[0046] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or have been made public.

[0047] In the embodiments of the present invention, the isobutene-maleic anhydride copolymer used is purchased from Kuraray, with a molecular weight of 55,000 - 65,000.

[0048] In the embodiments of the present invention, the particle size D50 of the yttria-stabilized zirconia powder is 0.19 microns, and the doping amount of yttria (Y2O3) is 5%.

[0049] The defoaming agent used in the embodiments of the present invention is isopropyl alcohol.

[0050] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] Step 1: Add the isobutene-maleic anhydride copolymer, butyl glycidyl ether, and ammonium citrate into deionized water, stir magnetically to obtain a solution, adjust the pH to 11 with a 10% sodium hydroxide solution by mass concentration, add a small amount of defoaming agent, and add the yttria-stabilized zirconia powder to obtain a premixed solution; wherein, the addition amount of the isobutene-maleic anhydride copolymer is 0.3 wt% of the mass of the yttria-stabilized zirconia powder, the addition amount of butyl glycidyl ether is 0.1 wt% of the mass of the yttria-stabilized zirconia powder, the addition amount of ammonium citrate is 0.2 wt% of the mass of the yttria-stabilized zirconia powder, the mass ratio of the yttria-stabilized zirconia powder to deionized water is 5:2, and the volume concentration of the defoaming agent in the premixed solution is 10%.

[0053] Step 2: Ball mill the above premixed solution for a certain time to obtain a zirconia slurry; the parameters of the ball milling are set as follows: the ball milling time is 5 h, and the ball milling speed is 500 r / min.

[0054] Step 3: Put the obtained zirconia slurry into a vacuum drying oven to evacuate and remove bubbles. After vacuum degassing, a zirconia slurry with a high solid content (70%) and a low viscosity (500 mPa·S) is obtained.

[0055] Step 4: Inject the zirconia slurry obtained in Step 3 into methyl silicone oil through a micro-injection pump at a flow rate of 0.3 mL / min, and stir in an oily medium with a stirring paddle. The rotation speed of the stirring paddle is 500 r / min, the temperature of the methyl silicone oil is 120 °C, and the droplets of the injected zirconia slurry automatically form spheres under the shearing force of the stirring, and a polymerization reaction occurs in the methyl silicone oil (the polymerization reaction occurs instantaneously, and the stirring stops after the zirconia slurry is added dropwise), forming a green body of zirconia ceramic microspheres with a strength of 1.39 MPa.

[0056] Step 5: Take out the green microspheres, wash them 4 times with absolute ethanol first, and then wash them with clear water; place the washed green zirconia microspheres in an oven and dry them at 60 °C for 15 h.

[0057] Step 6: Put the dried microspheres into a muffle furnace and raise the temperature to 100 °C at a rate of 5 °C / min, then hold for 2 h; then raise the temperature to 600 °C at a rate of 5 °C / min and hold for 1 h; then raise the temperature to 1200 °C at a rate of 5 °C / min and hold for 1 h; then raise the temperature to 1500 °C at a rate of 5 °C / min and hold for 2 h to obtain zirconia ceramic microspheres.

[0058] Step 7: Put the obtained zirconia ceramic microspheres into a planetary ball mill and grind them for 8 h at 500 r / min to obtain zirconia microspheres with good sphericity and smooth surface.

[0059] After testing, the density of the zirconia microspheres is 6.036 g / cm 3 , the hardness of the zirconia microspheres is 1334 HV, and the strength of the zirconia microspheres is 312 N.

[0060] Comparative Example 1

[0061] The difference from Example 1 is only that in Step 1, the mass ratio of yttria-stabilized zirconia powder to deionized water is 5:2.7 (i.e., the solid content is reduced to 65%), and the other steps and parameters are the same as those in Example 1.

[0062] Comparative Example 2

[0063] The difference from Example 1 is only that the addition amount of butyl glycidyl ether in Step 1 is omitted, and the other steps and parameters are the same as those in Example 1.

[0064] The particle size, density, sphericity, relative density, and yield (calculation formula: yield = mass of zirconia microspheres / mass of yttria-stabilized zirconia powder × 100%) of the zirconia microspheres prepared in Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

[0065] Table 1

[0066]

[0067] Figure 1 This is an optical microscope image of the green zirconia ceramic microspheres prepared in Example 1 of the present invention. It can be seen from Figure 1 that the green zirconia ceramic microspheres prepared in Example 1 have high sphericity and no damage on the surface.

[0068] Figure 2 This is the strength of the zirconia microspheres prepared in Example 1 of the present invention. It can be seen from Figure 2 that the strength of the zirconia microspheres prepared in Example 1 is 312 N.

[0069] Figure 3 This is an optical microscope image of the green body of the zirconia ceramic beads prepared in Comparative Example 1 of the present invention. It can be seen from Figure 3 that the sphericity of the green body of the zirconia ceramic beads prepared in Comparative Example 1 is poor.

[0070] Figure 4 This is an optical microscope image of the green body of the zirconia ceramic beads prepared in Comparative Example 2 of the present invention. It can be seen from Figure 4 that there are damages on the surface of the microspheres of the green body of the zirconia ceramic beads prepared in Comparative Example 2. By comparing Figure 1 and Figure 4 it can be seen that Figure 1 the microspheres have high sphericity and are not easily damaged, Figure 4 while there are damages on the surface of the microspheres after omitting the addition of butyl glycidyl ether. This is because butyl glycidyl ether is added in Example 1 to enhance the strength of the green body.

[0071] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing sub-millimeter zirconia microspheres, characterized in that, It includes the following steps: Add isobutylene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate into water, then adjust the pH of the solution to alkaline with an alkali solution, add an antifoaming agent and yttria-stabilized zirconia powder to obtain a premixed solution; Ball-mill the premixed solution, and then remove air bubbles under vacuum to obtain a zirconia slurry; Inject the zirconia slurry into an oily medium to form a green body of zirconia ceramic beads; After cleaning the green body of zirconia ceramic beads, dry it, calcine it with gradient heating, and then self-grind it to obtain sub-millimeter-sized zirconia beads; The addition amount of the isobutylene-maleic anhydride copolymer is 0.3wt%-0.6wt% of the mass of the yttria-stabilized zirconia powder; The addition amount of the butyl glycidyl ether is 0.2wt%-0.6wt% of the mass of the yttria-stabilized zirconia powder; The addition amount of the ammonium citrate is 0.1wt%-0.4wt% of the mass of the yttria-stabilized zirconia powder; The mass ratio of the yttria-stabilized zirconia powder to deionized water is 5:(1.5-2.5); The volume concentration of the antifoaming agent in the premixed solution is 0.5%-1%.

2. The preparation method of the sub-millimeter zirconia microbeads according to claim 1, wherein, The pH is 10-12.

3. The preparation method of the sub-millimeter zirconia microspheres according to claim 1, characterized in that, The time of the ball milling is 4-6h, and the rotation speed is 400-500r / min.

4. The preparation method of the sub-millimeter zirconia microbeads according to claim 1, characterized in that, The oily medium is methyl silicone oil.

5. The preparation method of the sub-millimeter zirconia microbeads according to claim 1, characterized in that, The temperature of the oily medium is 100-140°C.

6. The preparation method of the submillimeter zirconia microbeads according to claim 1, characterized in that, The injection flow rate is 0.3mL / min.

7. The preparation method of submillimeter zirconia microspheres according to claim 1, characterized in that, Stir the oily medium during the injection; the rotation speed of the stirring is 400-500r / min.

8. The preparation method of the sub-millimeter zirconia microbeads according to claim 1, characterized in that, The drying temperature is 50-70°C, and the time is 15h.

9. The preparation method of the sub-millimeter zirconia microbeads according to claim 1, characterized in that, The gradient heating calcination is specifically as follows: first rise to 200°C at a rate of 2-5°C / min and hold for 1-2h, then rise to 600°C at a rate of 2-5°C / min and hold for 1-2h, then rise to 1200°C at a rate of 5°C / min and hold for 1h, and then rise to 1500-1550°C at a rate of 5°C / min and hold for 1-4h.

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