Zirconia microspheres and a method for preparing the same

Abstract

The application provides a zirconia microsphere and a preparation method thereof, which comprises the following steps: mixing N,N'-methylenebisacrylamide, acrylamide, a dispersing agent and water, stirring, and obtaining slurry A; mixing 2.5Y-ZrO2 calcined powder and the slurry A, ball milling, adding a defoaming agent and an initiator, uniformly mixing, and obtaining slurry B; taking the slurry B as a dispersed phase, taking liquid paraffin as a mobile phase, performing mobile phase shearing, obtaining a microsphere precursor, adding a catalyst solution at the middle end of a microchannel, and obtaining a solidified zirconia microsphere blank; washing and drying the zirconia microsphere blank, performing low-temperature pre-sintering and high-temperature sintering, and obtaining the zirconia microsphere. The low-temperature pre-sintering and the high-temperature sintering are combined, the density of the zirconia microsphere is improved, the low-abrasion zirconia microsphere is obtained, and the application space of the zirconia microsphere in the fields of grinding and dispersion of high-value-added ceramics with high product purity requirements, biochemistry, and pharmaceutical industry is greatly increased.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of zirconia preparation, in particular to a zirconia microsphere and a preparation method thereof. BACKGROUND

[0002] Y2O3 stabilized zirconia ceramic microspheres have good development prospects due to their good chemical stability and mechanical strength. Meanwhile, as the requirement for the particle size of zirconia is further improved in various industries, the demand for zirconia microspheres with a diameter of less than 0.05 mm and good wear resistance is increasingly urgent. The existing preparation methods of zirconia microspheres with a diameter of more than 0.05 mm mainly include rolling method, spraying method, titration method and extrusion molding method. At present, the preparation of microsphere blanks with a diameter of less than 0.05 mm by using the titration molding method is also proposed, but the preparation process still has various defects, such as blockage of the discharge port. At present, the zirconia microspheres prepared by using the existing technology have poor particle size uniformity and poor size controllability, and it is still a difficulty to prepare zirconia microspheres with uniform particle size and good size controllability.

[0003] CN106830927A discloses a method for preparing zirconia ceramic microbeads by titration molding. The method mixes ceramic powder and mixed glue after hot melting, and forms ceramic microbead green bodies by air cooling and shaping during the dropping process by using a titration device. Since the cooling and solidification of the microbeads are carried out in the air, the droplets are pulled in the vertical direction by gravity, are elongated to a certain extent, and the sphericity is difficult to guarantee and the discharge port is easily blocked. SUMMARY

[0004] In order to overcome the defects in the prior art, the application provides a zirconia microsphere and a preparation method thereof.

[0005] The application provides a zirconia microsphere and a preparation method thereof. The method comprises the following steps:

[0006] N,N'-methylenebisacrylamide, acrylamide, a dispersing agent and deionized water are mixed and stirred to obtain slurry A; the mass ratio of N,N'-methylenebisacrylamide, acrylamide, the dispersing agent and deionized water is (1-3):(20-25):(0.1-0.3):(70-90);

[0007] The 2.5Y-ZrO2 calcined powder and the slurry A are mixed and ball milled, then a defoaming agent and an initiator are added and uniformly mixed to obtain slurry B; the mass ratio of the 2.5Y-ZrO2 calcined powder to the slurry A is (65-75):(25-35), and the volume ratio of the defoaming agent to the initiator to the slurry B is (0.05-0.1):(0.5-3):(95-100);

[0008] The slurry B is sheared by a flow phase through a micro-channel device by a peristaltic pump to obtain a microsphere precursor, a catalyst solution is added to the middle end of the micro-channel to obtain a solidified zirconia microsphere green body;

[0009] The zirconia microsphere green body is cleaned, dried, low-temperature pre-sintered and high-temperature sintered to obtain a zirconia microsphere.

[0010] The catalyst solution contains cuprous chloride and 2,2-bipyridine.

[0011] Preferably, the low-temperature pre-sintering temperature is 600-920 DEG C, and the holding time is 1-2.5 h.

[0012] Preferably, the high-temperature sintering temperature is 1250-1350 DEG C, and the holding time is 2-2.5 h.

[0013] Preferably, the inner diameter of the dispersed phase pipe of the micro-channel is 15 mu m, the inner diameter of the flow phase pipe is 100 mu m, and the flow rate ratio of the dispersed phase to the flow phase is 1:(3-5).

[0014] Preferably, the volume ratio of the catalyst solution to the flow phase is (1-3):100.

[0015] Preferably, the catalyst solution is a solution of 0.01-0.04 mg / L double solutes prepared by diluting cuprous chloride solution and 2,2-bipyridine solution with water, the volume ratio of the cuprous chloride solution to the 2,2-bipyridine solution is 1:(1-3), the dispersant is ammonium citrate, the initiator is ammonium persulfate, the defoaming agent is tributyl phosphate, and the flow phase is liquid paraffin (20 DEG C dynamic viscosity: 110-230 mPa s, surface tension: 25.83 mN / m).

[0016] Preferably, the ball milling time is 4-8 h, and the median particle size D50 of the slurry after ball milling is lower than 0.15 mu m.

[0017] Preferably, the concentration of the cuprous chloride solution is 0.05 g / L, and the concentration of the 2,2-bipyridine solution is 0.1 g / L.

[0018] The present application has the following beneficial effects:

[0019] 1. The present application combines gel solidification forming technology and microfluidic control technology, uses water-based slurry B as a dispersed phase, liquid paraffin as a flow phase, and applies the dispersed phase and the flow phase to a micro-channel device through two peristaltic pumps at different flow rate ratios to form stable water-in-oil (W / O), and then adds a catalyst solution to obtain a solidified microsphere green body, thereby solving the problem that, in traditional gel solidification forming, high active centers are generated under the action of a catalyst to initiate the exothermic reaction of monomers, resulting in the blockage of the outlet of the equipment during the preparation of microspheres.

[0020] 2. During the gelation of the slurry, the zirconia particles will agglomerate and even settle. If the gelation time is too long, the uniformity of the green body of the zirconia microspheres will be greatly affected, and the side reactions during the reaction will be intensified.

[0021] 3. The combination of low-temperature pre-sintering and high-temperature sintering not only removes the flow phase that is not cleaned in the micropores of the green body of the microspheres, but also promotes the solid solution of yttria and alumina and the grain boundary crystallization, so as to improve the strength of the grain boundary phase and the density of the zirconia microspheres, and obtain zirconia microspheres with low wear.

[0022] 4. The method is simple to operate, easy to implement, and has good results. The zirconia microspheres have great application space in the fields of high-value ceramic grinding and dispersion, biochemistry, and pharmaceutical industry, and broaden the application range of the zirconia microspheres. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a flow chart for the preparation of zirconia microspheres;

[0024] Figure 2 It is a micrograph of the green body of zirconia microspheres of Example 1, and the diameters of the microspheres are 12.1 μm and 14.6 μm, respectively;

[0025] Figure 3 It is a micrograph of zirconia microspheres of Example 1 (left, the diameter of the microspheres is 9.9 μm) and Reference Example 1 (right, the diameter of the microspheres is 43.8 μm);

[0026] Figure 4 It is a temperature rising curve diagram of low-temperature pre-sintering of 0.02 mm zirconia microspheres;

[0027] Figure 5 It is a temperature rising curve diagram of high-temperature sintering of 0.02 mm zirconia microspheres. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples.

[0029] The following provides a specific embodiment of a zirconia microsphere and a preparation method thereof according to the present application, and four examples are provided, but the present application is not limited to the provided examples, and the examples do not constitute any limitation on the protection scope of the present application.

[0030] The concentration of the catalyst solution in the application is 0.01-0.04 mg / L, the concentration of the cuprous chloride solution is 0.05 g / L, the concentration of the 2,2-bipyridine solution is 0.1 g / L, and the catalyst solution is prepared by dilution with water, the volume ratio of the cuprous chloride solution to the 2,2-bipyridine solution is 1:(1-3), the catalyst solution dispersant is ammonium citrate, the initiator is ammonium persulfate, the defoaming agent is tributyl phosphate, and the mobile phase is liquid paraffin (20 DEG C dynamic viscosity: 110-230 mPa s, surface tension: 25.83 mN / m).

[0031] The mechanical properties of the prepared zirconia microspheres, such as sphericity, density and wear resistance, are tested. The sphericity is measured by a laser diffraction method, the density is measured by an Archimedes drainage method, and the wear resistance is tested by loading 1 kg of the to-be-tested grinding medium balls into a 1 L zirconia ceramic tank, adding 150 g of water, 300 g of zirconium silicate (zircon sand), and 2 g of sodium tripolyphosphate, covering, fixing on a turntable in a rapid grinder, continuously grinding for 5 h, taking out the grinding medium balls, washing, drying, weighing, and requiring that the qualified grinding medium balls have a wear (Rm) of less than 1.5 ug / g / 5 h.

[0032] Example 1

[0033] 1.0 g of N,N'-methylenebisacrylamide, 20.0 g of acrylamide, 0.1 g of a dispersant and 78.90 g of deionized water are weighed, mixed and stirred to obtain slurry A1; 2.5Y-ZrO2 calcined powder: slurry A1 mass ratio = 65:35, mixed and ball milled for 4 h, the median particle size D50 of the ball milled slurry is 0.125 um, a defoaming agent and an initiator (volume ratio of the defoaming agent: the initiator: slurry B1 = 0.05:0.5:99.45) are added, mixed uniformly to obtain slurry B1; the slurry B1 is sheared by a flow phase liquid paraffin according to a flow rate ratio of 1:5 through a microchannel device by the action of a peristaltic pump to obtain a microsphere precursor, a catalyst solution is added at the middle end of the microchannel, the volume ratio of the catalyst solution (volume ratio of the cuprous chloride solution to the 2,2-bipyridine solution is 1:1; the concentration is 0.01 mg / L) to the flow phase is 1:100 to obtain a solidified zirconia microsphere blank; the microsphere blank is washed and dried, pre-sintered at a low temperature of 900 DEG C for 1.5 h, and finally sintered at a high temperature of 1300 DEG C for 2.5 h to obtain 0.01 mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.985, the density is 6.033 g / cm 3 , and the wear is 1.10 ug / g / 5 h.

[0034] Example 2

[0035] Take 1.0 g of N, N'-methylene bisacrylamide, 20.0 g of acrylamide, 0.12 g of dispersant and 78.88 g of deionized water, after mixing and stirring, get slurry A2; 2.5Y-ZrO2 calcined powder: slurry A2 mass ratio = 70:30, mix and ball mill for 4h, the median particle size D50 of the ball milled slurry is 0.133μm, add defoaming agent and initiator (the volume ratio of defoaming agent: initiator: slurry B2 is 0.05:0.7:99.25), mix uniformly to get slurry B2; the slurry B2 is passed through the microchannel device by peristaltic pump, and is sheared by the flow phase liquid paraffin according to the flow rate ratio of 1:3 to obtain microsphere precursor, a catalyst solution is added to the middle end of the microchannel, the volume ratio of the catalyst solution (the volume ratio of cuprous chloride solution to 2,2-bipyridine solution is 1:1; the concentration is 0.02mg / L) to the flow phase is 1:100; the microsphere precursor is washed and dried, then pre-sintered at a low temperature of 920℃ for 1h, and finally sintered at a high temperature of 1340℃ for 2.5h to obtain 0.02mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.990, the density is 6.033g / cm 3 , and the wear is 1.12ug / g / 5h.

[0036] Example 3

[0037] Take 1.2 g of N, N'-methylene bisacrylamide, 24 g of acrylamide, 0.12 g of dispersant and 74.68 g of deionized water, after mixing and stirring, get slurry A3; 2.5Y-ZrO2 calcined powder: slurry A3 mass ratio = 70:30, mix and ball mill for 6h, the median particle size D50 of the ball milled slurry is 0.116μm, add defoaming agent and initiator (the volume ratio of defoaming agent: initiator: slurry B3 is 0.05:0.5:99.45), mix uniformly to get slurry B3; the slurry B3 is passed through the microchannel device by peristaltic pump, and is sheared by the flow phase liquid paraffin according to the flow rate ratio of 1:5 to obtain microsphere precursor, a catalyst solution is added to the middle end of the microchannel, the volume ratio of the catalyst solution (the volume ratio of cuprous chloride solution to 2,2-bipyridine solution is 1:2; the concentration is 0.02mg / L) to the flow phase is 2:100; the microsphere precursor is washed and dried, then pre-sintered at a low temperature of 900℃ for 1.5h, and finally sintered at a high temperature of 1300℃ for 2.5h to obtain 0.01mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.986, the density is 6.037g / cm 3 , and the wear is 1.26ug / g / 5h.

[0038] Example 4

[0039] Take 1.2 g of N, N'-methylene bisacrylamide, 24 g of acrylamide, 0.2 g of dispersant and 74.60 g of deionized water, after mixing and stirring, the slurry A4 is obtained; according to 2.5Y-ZrO2 calcined powder: slurry A4 mass ratio = 75:25, mix and ball mill for 6h, the medium particle size D50 of the ball milled slurry is 0.139μm, add defoaming agent and initiator (the volume ratio of defoaming agent: initiator: slurry B4 is 0.05:0.6:99.43), mix uniformly to obtain slurry B4; the slurry B4 is passed through the microchannel device by peristaltic pump, and is sheared according to a flow rate ratio of 1:3 by a flow phase liquid paraffin to obtain a microsphere precursor, a catalyst solution is added at the middle end of the microchannel, the catalyst solution (the volume ratio of cuprous chloride solution to 2,2-bipyridine solution is 1:2; the concentration is 0.02mg / L): the volume ratio of flow phase is 2:100; the microsphere precursor is washed and dried, then pre-sintered at a low temperature of 920℃ for 1h, and finally sintered at a high temperature of 1340℃ for 2.5h to obtain 0.02mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.992, the density is 6.040g / cm 3 , and the abrasion is 1.10ug / g / 5h.

[0040] Reference Example 1

[0041] Take 1.0 g of N, N'-methylene bisacrylamide, 20 g of acrylamide, 0.1 g of dispersant and 78.90 g of deionized water, after mixing and stirring, the slurry A1' is obtained; according to 2.5Y-ZrO2 calcined powder: slurry A1' mass ratio = 55:45, mix and ball mill for 4h, the medium particle size D50 of the ball milled slurry is 0.212μm, then add defoaming agent, initiator and catalyst solution (the volume ratio of cuprous chloride solution to 2,2-bipyridine solution is 1:1; the concentration is 0.01mg / L), the volume ratio of defoaming agent: initiator: catalyst solution: slurry A1' is 0.05:0.5:0.01:99.44, mix uniformly to obtain slurry B1', the slurry B1' is passed through the microchannel device by peristaltic pump, and is sheared according to a flow rate ratio of 1:3 by a flow phase liquid paraffin to obtain zirconia microsphere precursor; the microsphere precursor is washed and dried, then pre-sintered at a low temperature of 920℃ for 1h, and finally sintered at a high temperature of 1340℃ for 2.5h to obtain 0.05mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.973, the density is 5.950g / cm 3 , and the abrasion is 3.60ug / g / 5h.

[0042] Reference Example 2

[0043] Take 1.2 g of N, N'-methylene bisacrylamide, 24 g of acrylamide, 0.12 g of dispersant and 74.68 g of deionized water, after mixing and stirring, get slurry A2'; according to 2.5Y-ZrO2 calcined powder: slurry A2' mass ratio = 70:30, mix and ball mill for 6h, the medium particle size D50 of ball milling slurry is 0.220μm, add defoaming agent and initiator (the volume ratio of defoaming agent: initiator: slurry B2' is 0.05:0.5:99.45), mix uniformly to get slurry B2'; the slurry B2' is sheared by the flow phase liquid paraffin according to the flow rate ratio of 1:5 through the microchannel device by the action of peristaltic pump, the microsphere precursor is obtained, the catalyst solution is added at the middle end of the microchannel, the volume ratio of catalyst solution (volume ratio of cuprous chloride solution to 2,2-bipyridine solution is 1:3; concentration is 0.01mg / L) to flow phase is 2:100; the microsphere blank is washed and dried, and then sintered at high temperature of 1340℃ for 2.5h to obtain 0.07mm zirconia microspheres. The sphericity of the zirconia microspheres is 0.980, the density is 6.008g / cm 3 , and the abrasion is 2.10ug / g / 5h.

[0044] Characterization example

[0045] The particle size of the ball milling slurry, the density of the microspheres, the sphericity and the abrasion (0.02mm zirconia microspheres are used as experiments) of the ball milling slurry of examples 1-4 and reference examples 1-2 are analyzed by particle size analyzer, density tester and laser diffraction instrument respectively, and the results are shown in table 1 and table 2. The pre-sintering and sintering process parameters of 0.02mm zirconia microspheres are shown in table 3 and table 4; the preparation flow chart of zirconia microspheres is attached as Figure 1 ; the micrograph of zirconia microsphere green body of example 1 is as Figure 2 ; the micrograph of zirconia microspheres of example 1 and reference example 1 is as Figure 3 ; the pre-sintering and sintering temperature rising curve of 0.02mm zirconia microspheres is as Figure 4 and 5 .

[0046] Table 1 particle size of slurry B of different examples and reference examples

[0047] Item D100 / μm D980 / μm D90 / μm D50 / μm D10 / μm Example 1 0.501 0.348 0.340 0.125 0.0788 Example 2 0.456 0.285 0.336 0.133 0.0912 Example 3 0.503 0.388 0.302 0.116 0.0754 Example 4 0.566 0.327 0.341 0.139 0.0930 Reference Example 1 0.802 0.421 0.345 0.212 0.124 Reference Example 2 0.836 0.387 0.305 0.220 0.135

[0048] Table 2 sphericity, density and abrasion of zirconia microspheres of different examples and reference examples

[0049] Item Example 1 Example 2 Example 3 Example 4 Reference Example 1 Reference Example 2 Sphericity 0.985 0.990 0.986 0.992 0.973 0.980 Density / (g / cm 3 ) 6.033 6.033 6.037 6.040 5.950 6.008 Abrasion / (ug / g / 5h) 1.10 1.12 1.26 1.10 3.60 2.10

[0050] From table 1 and table 2 can see: after ball milling slurry B, the slurry B of the example obtained median particle size is slightly smaller than the median particle size of the slurry obtained in the reference example; the density and sphericity of the microspheres obtained by the method of the embodiment 1-4 are high, while the density and sphericity obtained in the reference example are low, which shows that the mechanical properties of the embodiment and the reference example have obvious differences; at the same time, the abrasion of the zirconia microspheres obtained by the embodiment is significantly lower than that of the reference example.

[0051] Table 3 pre-sintering process parameters for obtaining 0.02mm zirconia microspheres

[0052]

[0053] Table 4 sintering process parameters for obtaining 0.02mm zirconia microspheres

[0054]

[0055]

[0056] The present application relates to a kind of zirconia microspheres and preparation method thereof, specific steps are as follows in turn: step one, N,N'- methylenebisacrylamide, acrylamide, dispersing agent and deionized water are weighed according to proportion, after mixing and stirring, obtain slurry A;Step two, 2.5Y-ZrO 2 Calcined powder and slurry A are mixed according to proportion again ball milling for a certain time, after the median particle size D50 of ball milling slurry is qualified, a certain amount of defoaming agent and initiator are added, and after mixing, slurry B is obtained;Step three, slurry B is passed through microchannel device by peristaltic pump, according to certain flow rate ratio is sheared by flow phase, and microsphere precursor is obtained, catalyst solution is added in the middle end of microchannel, and solidified zirconia microsphere blank is obtained;Step four, microsphere blank is cleaned, dried, low-temperature pre-sintered and high-temperature sintered, and 0.01-0.03mm zirconia microspheres are obtained.The sphericity, density and wear resistance of zirconia microspheres are tested.

[0057] The method of the present application combines gel solidification forming technology and microfluidic control technology, uses water-based slurry B as the dispersed phase and liquid paraffin as the flowing phase, and applies the dispersed phase and the flowing phase to the microchannel device through two peristaltic pumps at different flow rate ratios to form stable water-in-oil (W / O), and then adds cuprous chloride and 2,2-bipyridine double-catalytic solution, which not only plays an antioxidant and coordination complex role, but also can quickly solidify the microsphere precursor in the flowing phase, and very good control the size and uniformity of the green body, solves the problem of traditional gel solidification forming, under the action of the catalyst, generates high active center, initiates the exothermic reaction of monomer, causes the preparation of microspheres to block the equipment outlet. Finally, the combination of low-temperature pre-sintering and high-temperature sintering not only eliminates the influence of the flowing phase which is not cleaned in the micro-pores of the microsphere green body on the sintering process, but also promotes the solid solution of yttria and alumina and the grain boundary precipitation, so as to improve the grain boundary phase strength, further improve the density of zirconia microspheres, and obtain low-abrasion zirconia microspheres.

[0058] The preparation method of the present application is suitable for industrialized production, so as to better promote the application and development of zirconia microspheres, especially in the application space in the fields of high-value ceramic grinding and dispersion, biochemistry, pharmaceutical industry and the like which have very high requirements on product purity.

[0059] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing zirconia microspheres, characterized by: The method comprises the following steps: N,N'-methylenebisacrylamide, acrylamide, dispersant ammonium citrate, and water are mixed and stirred to obtain slurry A; the mass ratio of N,N'-methylenebisacrylamide, acrylamide, dispersant ammonium citrate, and water is (1-3):(20-25):(0.1-0.3):(70-90); The 2.5Y-ZrO2 calcined powder and the slurry A are mixed and ball milled, then a defoaming agent tributyl phosphate and an initiator ammonium persulfate are added, and the mixture is uniformly mixed to obtain slurry B; the mass ratio of the 2.5Y-ZrO2 calcined powder to the slurry A is (65-75):(25-35), the volume ratio of the defoaming agent tributyl phosphate to the initiator ammonium persulfate to the slurry B is (0.05-0.1):(0.5-3):(95-100), and the median particle size D50 of the slurry after ball milling is less than 0.15 μm; The slurry B is used as a dispersed phase, and liquid paraffin is used as a flow phase; the dispersed phase and the flow phase are respectively passed through a micro-channel device by a peristaltic pump; the inner diameter of a dispersed phase pipeline of the micro-channel is 15 μm, the inner diameter of a flow phase pipeline of the micro-channel is 100 μm, and the flow rate ratio of the dispersed phase to the flow phase is 1:(3-5); the microspheres precursor is obtained by flow phase shearing; a catalyst solution is added to the middle end of the micro-channel to obtain solidified zirconia microsphere green bodies; the volume ratio of the catalyst solution to the flow phase is (1-3):100; the catalyst solution is a solution of 0.01-0.04 mg / L double solutes prepared by diluting cuprous chloride solution and 2,2-bipyridine solution with water; The zirconia microsphere green bodies are cleaned, dried, pre-sintered at a low temperature, and sintered at a high temperature; the pre-sintering temperature at the low temperature is 900-920 ℃, and the holding time is 1-2.5 h; the sintering temperature at the high temperature is 1250-1350 ℃, and the holding time is 2-2.5 h; and the zirconia microspheres are obtained.

2. The method of claim 1, wherein: The volume ratio of the cuprous chloride solution to the 2,2-bipyridine solution is 1:(1-3); the concentration of the cuprous chloride solution is 0.05 g / L; and the concentration of the 2,2-bipyridine solution is 0.1 g / L.

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