Preparation method of sub-millimeter zirconia microbeads

Abstract

The application relates to the technical field of ceramic materials, in particular to a preparation method of sub-millimeter zirconia microbeads. The preparation method comprises the following steps: adding isobutene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate into water, then adjusting the pH of the solution to be alkaline by using an alkali solution, adding a defoaming agent and yttrium oxide stabilized zirconia powder to obtain a premix solution; ball milling the premix solution, then removing bubbles in a vacuum to obtain a zirconia slurry; injecting the zirconia slurry into an oily medium to obtain zirconia ceramic microbead green bodies; cleaning the zirconia ceramic microbead green bodies, then drying, gradient temperature calcining and self-grinding to obtain sub-millimeter zirconia microbeads; the application only needs to add three kinds of organic matters to form gel microspheres, and the content of the organic matters is small and the organic matters are non-toxic. The application has high finished product yield, simple operation, low cost, uniform particle size of the prepared zirconia microbeads, and high compactness and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a method for preparing submillimeter-sized zirconia microspheres. Background Technology

[0002] Zirconia beads, made from micron- and sub-nanometer-sized zirconia and yttrium oxide, are grinding beads used for ultrafine grinding and dispersion of materials requiring "zero pollution" and high viscosity and hardness. Zirconia ceramic microspheres not only possess the excellent properties of ceramic materials, but also, due to their spherical shape, have many advantages of microsphere particles, making them widely used in nuclear industry, biology, medicine, chemical industry, military industry, environmental protection, and many other fields. Research on ceramic microspheres is becoming increasingly in-depth, and preparation methods are proliferating. However, these methods all have one or two drawbacks, making it 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 materials. Based on the principle of spheroidization, they are mainly divided into: methods using crystallography principles (such as the sol-gel method), methods using mechanical forces such as extrusion, friction, and collision (such as the rolling method), and methods using surface tension principles.

[0003] Currently, ceramic microspheres are prepared using sol-gel molding and roll forming methods. Neither method can simultaneously achieve high bulk density, high strength and hardness, and excellent stability. Traditional gel casting uses an acrylamide system, which contains a large amount of organic matter (including monomers, crosslinking agents, dispersants, initiators, and catalysts). This can easily lead to gas formation during sintering, leaving porosity and affecting the ceramic's density. Acrylamide, as a monomer, is inherently toxic and can cause oxygen inhibition (a layer will peel off from the surface of the prepared ceramic microspheres). Furthermore, the excessive organic matter requires a longer holding time during the debinding process to expel the organic matter as gas.

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

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

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a method for preparing submillimeter-sized zirconia microspheres, comprising the following steps:

[0008] Isobutylene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate were added to water, and then the pH of the solution was adjusted to alkaline using an alkaline solution. Defoamer and yttrium oxide were added to stabilize the zirconium oxide powder to obtain a premixed solution.

[0009] The premixed liquid was ball-milled and then degassed under vacuum to obtain a zirconium oxide slurry.

[0010] The zirconia slurry is injected into an oily medium to form zirconia ceramic microspheres;

[0011] After cleaning the zirconia ceramic microsphere green body, it is dried, calcined by gradient heating, and then auto-ground to obtain sub-millimeter-sized zirconia microspheres.

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

[0013] The amount of butyl glycidyl ether added is 0.2wt%-0.6wt% of the mass of yttrium oxide stabilized zirconium oxide powder;

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

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

[0016] The volume concentration of the defoamer in the premixed liquid is 0.5%-1%.

[0017] In this invention, adding too much isobutylene-maleic anhydride copolymer will result in excessively high viscosity and poor flowability, while adding too little will result in excessively slow gelation rate. Therefore, this invention preferably limits the amount of isobutylene-maleic anhydride copolymer added to 0.3wt%-0.6wt% of the mass of yttrium oxide-stabilized zirconia powder.

[0018] During the settling process of zirconia slurry in an oily medium, the molecules at the interface layer (aqueous and oily phases) are subjected to asymmetric forces, causing the interface layer to form spherical surfaces and thus creating a spherical slurry. Introducing an isobutylene-maleic anhydride copolymer gel system into the ceramic slurry can trigger a polymerization reaction of the gel system during the spherical settling of the zirconia slurry, resulting in in-situ solidification of the spherical slurry and the production of zirconia microsphere green bodies.

[0019] The density of the zirconia microsphere structure was improved by adding a low amount of organic matter; the size of the zirconia ceramic microspheres was controlled by adjusting the flow rate of the micro-injection pump and the rotation speed of the stirring paddle, which greatly improved the preparation efficiency of the microspheres.

[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 hours 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 this invention, excessively high temperatures in the oily medium can cause the zirconia microspheres to crack, while excessively low temperatures can slow the gelation rate and affect sphericity. Therefore, this invention preferably limits the temperature of the oily medium to the range of the parameters mentioned above.

[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 stirring speed is 400-500 r / min.

[0027] This invention enables the zirconia microspheres to achieve sub-millimeter particle sizes by adjusting the flow rate of the zirconia slurry injected into the oily medium and the rotation speed of the oily medium.

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

[0029] In a preferred embodiment of the present invention, the gradient heating calcination specifically comprises: first, heating at 2-5°C / min to 200°C and holding for 1-2 hours (first stage); then heating at 2-5°C / min to 600°C and holding for 1-2 hours (second stage); then heating at 5°C / min to 1200°C and holding for 1 hour (third stage); and finally heating at 5°C / min to 1500-1550°C and holding for 1-4 hours (fourth stage). In this invention, the purpose of the gradient heating is to first remove moisture in the first stage, then remove organic matter in the second stage, stabilize the crystalline phase in the third stage, and finally sinter in the fourth stage.

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

[0031] Compared to existing technologies, this invention uses only three organic compounds: isobutylene-maleic anhydride copolymer, butyl glycidyl ether, and ammonium citrate. Adding only 0.6-1.6 wt% of these organic compounds is sufficient to prepare zirconia microsphere green bodies with high sphericity. Compared to existing methods for preparing zirconia microspheres, such as acrylamide gel systems (where the organic compound content is typically 5.5-7 wt%), this reduces the amount of organic compound added by 4-5 wt%. Furthermore, the isobutylene-maleic anhydride copolymer system is non-toxic and does not present oxygen inhibition problems. Due to the low amount of organic compound added, the operation is simpler, the cost is lower, and it is more suitable for industrial production.

[0032] This invention increases the solid content of zirconia slurry by 5%-8% by introducing an isobutylene-maleic anhydride copolymer system and adding ammonium citrate as a dispersant, thus preparing a zirconia slurry with high solid content and low viscosity. The addition of butyl glycidyl ether can improve the green strength of zirconia microspheres.

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

[0034] This invention improves the density and mechanical properties of microspheres by controlling the temperature of the oily medium (methyl silicone oil) to cure the zirconia slurry without the need for additional initiators and catalysts. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0037] Figure 2 The strength of the zirconia microspheres prepared in Example 1 of this invention.

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

[0039] Figure 4 This is an optical microscope image of the zirconia ceramic microsphere green body prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now 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, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] This invention uses isobutylene-maleic anhydride copolymer, ammonium citrate, and butyl glycidyl ether to form a mixed solution with yttrium-stabilized zirconia powder. The prepared zirconia slurry is dripped into an oily medium and stirred to form microsphere green bodies. After separating the zirconia microsphere green bodies from the oily medium, they are washed, dried, debinded (i.e., removed organic matter), and sintered to produce zirconia microspheres. Compared with previous methods for preparing zirconia microspheres, this invention only requires the addition of three organic substances to form gel microspheres, and the organic matter content is low and non-toxic. The zirconia microspheres prepared by this method have a high yield, are simple to operate, and have low cost. The prepared zirconia microspheres have uniform particle size and high density and mechanical properties.

[0046] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0047] The isobutylene-maleic anhydride copolymer used in the embodiments of the present invention was purchased from Kuraray, with a molecular weight of 55,000-65,000.

[0048] In this embodiment of the invention, the particle size D50 of the yttrium oxide-stabilized zirconium oxide powder is 0.19 micrometers, and the doping amount of yttrium oxide (Y2O3) is 5%.

[0049] The defoamer used in the embodiments of the present invention is isopropanol.

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

[0051] Example 1

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

[0053] Step 2: The premixed liquid is ball-milled for a certain time to obtain zirconia slurry; the ball milling parameters are set as follows: ball milling time is 5h, and ball milling speed is 500r / min.

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

[0055] Step 4: The zirconia slurry obtained in Step 3 is injected into methyl silicone oil at a flow rate of 0.3 mL / min using a micro-injection pump. The mixture is stirred in the oily medium by a stirring paddle at a speed of 500 r / min and a temperature of 120°C for the methyl silicone oil. The droplets of zirconia slurry are automatically spherical under the shear force of the stirring and undergo a polymerization reaction in the methyl silicone oil (the polymerization reaction occurs instantaneously, and stirring is stopped after the zirconia slurry is added), forming zirconia ceramic microsphere green bodies with a strength of 1.39 MPa.

[0056] Step 5: Take out the microsphere preform, wash it 4 times with anhydrous ethanol, and then wash it with water; place the cleaned zirconia microsphere preform in a drying oven and dry it at 60℃ for 15 hours.

[0057] Step 6: Place the dried microspheres into a muffle furnace and heat to 100℃ at 5℃ / min, then hold for 2 hours; then heat to 600℃ at 5℃ / min and hold for 1 hour; then heat to 1200℃ at 5℃ / min and hold for 1 hour; finally heat to 1500℃ at 5℃ / min and hold for 2 hours to obtain zirconia ceramic microspheres.

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

[0059] The density of the zirconia microspheres was tested to be 6.036 g / cm³. 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 only difference from Example 1 is that in step 1, the mass ratio of yttrium-stabilized zirconia powder to deionized water is 5:2.7 (i.e., the solid content is reduced to 65%). All other steps and parameters are the same as in Example 1.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that the amount of butyl glycidyl ether added in step 1 is omitted; all other steps and parameters are the same as in Example 1.

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

[0065] Table 1

[0066]

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

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

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

[0070] Figure 4 This is an optical microscope image of the zirconia ceramic microsphere green body prepared in Comparative Example 2 of this invention. Figure 4 It can be seen that the surface of the microspheres in the zirconia ceramic microsphere green body prepared in Comparative Example 2 is damaged. Figure 1 and Figure 4 It can be seen that, Figure 1 The microspheres have high sphericity and are not easily damaged. Figure 4 The microspheres were damaged after omitting the addition of butyl glycidyl ether. This is because the addition of butyl glycidyl ether in Example 1 enhanced the strength of the preform.

[0071] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing submillimeter-sized zirconia microspheres, characterized in that, Includes the following steps: Isobutylene-maleic anhydride copolymer, butyl glycidyl ether and ammonium citrate were added to water, and then the pH of the solution was adjusted to alkaline using an alkaline solution. Defoamer and yttrium oxide were added to stabilize the zirconium oxide powder to obtain a premixed solution. The premixed liquid was ball-milled and then degassed under vacuum to obtain a zirconium oxide slurry. The zirconia slurry is injected into an oily medium to obtain zirconia ceramic microsphere green bodies; After cleaning the zirconia ceramic microsphere green body, it is dried, calcined by gradient heating, and then auto-ground to obtain sub-millimeter-sized zirconia microspheres. The amount of the isobutylene-maleic anhydride copolymer added is 0.3wt%-0.6wt% of the mass of the yttrium oxide-stabilized zirconia powder; The amount of butyl glycidyl ether added is 0.2wt%-0.6wt% of the mass of yttrium oxide stabilized zirconium oxide powder; The amount of ammonium citrate added is 0.1wt%-0.4wt% of the mass of yttrium oxide stabilized zirconia powder; The mass ratio of the yttrium-stabilized zirconium oxide powder to water is 5:(1.5-2.5); The volume concentration of the defoamer in the premixed liquid is 0.5%-1%.

2. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The pH is 10-12.

3. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The ball milling time is 4-6 hours, and the rotation speed is 400-500 r / min.

4. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The oily medium is methyl silicone oil.

5. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The temperature of the oily medium is 100-140℃.

6. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The injection flow rate is 0.3 mL / min.

7. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The oily medium is stirred during injection; the stirring speed is 400-500 r / min.

8. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The drying temperature is 50-70℃, and the time is 15 hours.

9. The method for preparing submillimeter-sized zirconia microspheres according to claim 1, characterized in that, The gradient heating calcination process is as follows: first, the temperature is increased to 200℃ at a rate of 2-5℃ / min and held for 1-2 hours; then, the temperature is increased to 600℃ at a rate of 2-5℃ / min and held for 1-2 hours; then, the temperature is increased to 1200℃ at a rate of 5℃ / min and held for 1 hour; and then, the temperature is increased to 1500-1550℃ at a rate of 5℃ / min and held for 1-4 hours.

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