A method for preparing high roundness zirconia microbeads based on controllable emulsion template method

Abstract

This invention discloses a method for preparing highly spherical zirconia microspheres based on a controllable emulsion template method. Using a water-in-oil emulsion as a template, a composite emulsifier of Span-80 and Tween-80 is employed at a mass ratio of 2:1-4:1, a total concentration of 2-3%, and an oil-to-water volume ratio of 3:1-5:1. Uniform and stable emulsion droplets are formed under a stirring intensity of 800-1500 rpm. The emulsion is then cured at a constant temperature of 50-65℃ for 1-3 hours to allow the gel network to form slowly, preventing microsphere shrinkage and cracking. Finally, a three-stage stepped sintering process is used: increasing the temperature at 1-3℃ / min to 300-400℃ and holding for 1-2 hours; increasing the temperature at 2-5℃ / min to 700-800℃ and holding for 1-2 hours; and increasing the temperature at 3-8℃ / min to 1350-1400℃ and holding for 15-30 minutes to inhibit abnormal grain growth and achieve sufficient densification. Through the coordinated control of emulsification, curing and sintering, the prepared zirconia microspheres have excellent sphericity, particle size uniformity, density and mechanical properties, and the process parameters can be adjusted over a wide range, showing good prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of inorganic ceramic material preparation technology, and particularly relates to a method for preparing highly round zirconia microspheres based on a controllable emulsion template method. Background Technology

[0002] Zirconia microspheres are widely used in high-end grinding, catalyst carriers, biomedicine, and precision polishing. Traditional preparation methods, such as spray drying and solid-state sintering, suffer from poor sphericity, wide particle size range, and susceptibility to hollowness or cracking. Several published papers in the field of zirconia microsphere preparation technology have addressed related methods. For example, Tsinghua University disclosed a method for preparing zirconia ceramic microspheres using a microfluidic device. This method uses a zirconia precursor sol as the internal phase fluid and a microfluidic channel system to create dual-emulsion droplets, resulting in microspheres with high sphericity and uniform size. While this method significantly improves the particle size uniformity problem of traditional stirring emulsification methods, the microfluidic device has low yield and requires strict control over slurry flowability, hindering industrial-scale production. Furthermore, the sintering process still uses traditional heating methods, leaving room for further improvement in microsphere densification. Another method for preparing zirconia microspheres uses a spray process to inject slurry into high-temperature silicone oil for gelation. This process is simple, uses low amounts of organic matter, and offers high controllability. However, during spray molding, the droplet fall is easily disturbed by airflow, making it difficult to maintain a stable sphericity of over 96% for the microspheres. Furthermore, the sintering process does not finely control grain growth, leaving room for improvement in the hardness and wear resistance of the resulting microspheres. A titration method for producing zirconia ceramic microspheres and its preparation process uses pectin as a binder and potassium aluminum sulfate as a curing agent. A gel encapsulating zirconia particles is generated through a cross-linking reaction, suitable for mass production of microspheres of different particle sizes, exhibiting good internal structural uniformity. The drawbacks of this method are that titration molding relies on gravity dripping, making the microspheres prone to tailing or deformation during curing, resulting in a sphericity typically below 95%. Additionally, the gel system contains organic components, and improper control during the glue removal process can easily lead to microcracks, affecting the final product's density and mechanical properties. While existing methods have achieved breakthroughs in certain properties, they still struggle to simultaneously achieve sphericity, particle size distribution, and density. Summary of the Invention

[0003] Based on the above, this invention provides a method for preparing high-roundness zirconia microspheres based on a controllable emulsion template method. Through the synergistic design of the emulsion template method and three-stage sintering, this invention achieves for the first time a comprehensive performance improvement with roundness ≥97%, density ≥6.05 g / cm³, and Vickers hardness (HV3) ≥1250.

[0004] In a first aspect, the present invention provides a method for preparing highly spherical zirconia microspheres based on a controllable emulsion template method, comprising the following steps:

[0005] S1 emulsion system preparation: The aqueous phase of the zirconium oxide precursor is added to the oil phase containing the compound emulsifier, and a stable water-in-oil emulsion is formed under stirring conditions;

[0006] S2 Emulsion Dispersion and Curing: The emulsion is dispersed evenly under stirring intensity, then cured at low temperature and kept at a warm temperature to solidify the emulsion droplets into gel microbeads;

[0007] S3 Microbead Separation and Cleaning: The cured gel microbeads are separated from the oil phase and cleaned with organic solvents to remove surface oil phase and emulsifier residues;

[0008] S4 Drying and Sintering: The cleaned microspheres are dried and then heat-treated using a three-stage stepped sintering process to obtain high-roundness zirconia microspheres.

[0009] In one possible implementation, the compound emulsifier is Span-80 and Tween-80, with a mass ratio of 2:1 to 4:1, a total concentration of 2-3%, and an oil-water volume ratio of 3:1 to 5:1.

[0010] In one possible implementation, the stirring intensity is 800-1500 rpm; the low-temperature curing temperature is 50-65℃, and the curing holding time is 1-3 h.

[0011] In one possible implementation, the three-stage stepped sintering process includes:

[0012] First stage: Increase the temperature to 300-400℃ at a rate of 1-3℃ / min and hold for 1-2 hours;

[0013] Second stage: Increase the temperature to 700-800℃ at a rate of 2-5℃ / min and hold for 1-2 hours;

[0014] The third stage: raise the temperature to 1350-1400℃ at a rate of 3-8℃ / min, hold for 15-30 min, and then allow it to cool naturally or slowly to room temperature.

[0015] In one possible embodiment, the aqueous phase of the zirconium oxide precursor is a yttrium-stabilized zirconium oxide sol or a mixed solution containing yttrium salt and zirconium salt, wherein the molar fraction of yttrium is 2-5 mol.

[0016] In one possible implementation, the organic solvent is one or more of petroleum ether, ethanol, or acetone, and the number of washing cycles is 2-4.

[0017] In one possible implementation, the drying temperature is 50-65°C and the drying time is 10-14 h.

[0018] Secondly, the present invention provides a high-roundness zirconia microsphere prepared by any of the above methods, wherein the microsphere has a roundness ≥97%, a particle size span ≤1.8, a density ≥6.05 g / cm³, and a Vickers hardness HV3 ≥1250.

[0019] In one possible implementation, the particle size distribution of the microspheres is determined by a laser particle size analyzer, wherein D10, D50, and D90 represent the particle size values ​​when the cumulative distribution is 10%, 50%, and 90%, respectively.

[0020] Thirdly, the present invention provides an application of high-roundness zirconia microspheres prepared according to any of the above methods in high-end grinding media, catalyst supports, biomedical materials or precision polishing materials.

[0021] Compared with the prior art, this application has at least the following beneficial effects:

[0022] This invention uses a blend of Span-80 and Tween-80 as emulsifiers, with their mass ratio controlled between 2:1 and 4:1, to adjust the HLB value of the system, enabling the formation of a dense and stable composite interfacial film at the oil-water interface. This interfacial film exhibits high interfacial viscoelasticity and low interfacial tension, effectively reducing droplet coalescence and improving the kinetic stability of the emulsion. Compared to a single emulsifier, the blended system more readily forms fine droplets with a concentrated size distribution under shear and agitation. The particle size distribution ((D90-D10) / D50) of the resulting microspheres after solidification can be controlled within 1.8, and the sphericity can reach over 97%.

[0023] During the curing process of emulsion droplets, the gelation rate plays a crucial role in the final morphology of the microspheres. This invention employs a constant temperature curing method at 50-65℃ for 1-3 hours to avoid excessive solvent evaporation and uneven gel shrinkage caused by excessively high temperatures or rapid heating. Under these mild conditions, the gel network forms slowly, and internal stress is gradually released, resulting in microspheres with smooth surfaces and intact spherical shapes. This effectively suppresses surface wrinkling, cracking, or tailing phenomena that easily occur during rapid curing. This shape control method is a vital guarantee for achieving a roundness of not less than 97%.

[0024] This invention designs a three-stage sintering process: "low temperature slow rise – medium temperature holding – high temperature short time". In the low temperature stage, the temperature is raised to 300-400℃ at a rate of 1-3℃ / min and held for 1-2 hours to promote the full pyrolysis and discharge of emulsifiers and residual solvents, preventing gas accumulation that could cause cracking or porosity. In the medium temperature stage, the temperature is raised to 700-800℃ at a rate of 2-5℃ / min and held for 1-2 hours to allow grain boundary diffusion to dominate and achieve initial densification, eliminating porosity and inhibiting grain coarsening. In the high temperature stage, the temperature is raised to 1350-1400℃ at a rate of 3-8℃ / min and held for 15-30 minutes to achieve rapid densification. At the same time, the short holding time effectively limits grain boundary migration and prevents abnormal grain growth, thereby ensuring that the Vickers hardness (HV3) is not lower than 1250.

[0025] This invention not only optimizes each stage individually, but also achieves multi-scale structural control through an overall synergistic design of emulsification, curing, and sintering: the emulsification stage determines the initial droplet size and sphericity, the curing stage fixes the microsphere morphology and imparts initial strength, and the sintering stage enhances density and hardness. The coupling of these three stages results in microspheres that outperform existing technologies in four key indicators: sphericity, particle size distribution, density, and hardness. Simultaneously, key process parameters such as oil-water ratio (3:1~5:1), stirring intensity (800~1500 rpm), and heating rate have a wide adjustable range, demonstrating strong adaptability to different raw materials and equipment conditions, and possessing excellent potential for pilot-scale amplification and industrial-scale promotion. Attached Figure Description

[0026] Figure 1 This is a SEM image of Embodiment 1 of this application;

[0027] Figure 2 This is a SEM image of Embodiment 2 of this application;

[0028] Figure 3 This is a SEM image of Embodiment 3 of this application;

[0029] Figure 4 This is a SEM image of Embodiment 4 of this application;

[0030] Figure 5 This is a SEM image of Embodiment 5 of this application;

[0031] Figure 6 This is a SEM image of Comparative Example 1 of this application;

[0032] Figure 7 This is a SEM image of Comparative Example 2 of this application;

[0033] Figure 8 This is an optical microscope image of the emulsion in Example 1 of this application;

[0034] Figure 9 This is an optical microscope image of the emulsion in Example 2 of this application;

[0035] Figure 10 This is an optical microscope image of the emulsion in Example 3 of this application;

[0036] Figure 11 This is an optical microscope image of the emulsion in Example 4 of this application;

[0037] Figure 12 This is an optical microscope image of the emulsion in Example 5 of this application;

[0038] Figure 13 This is an optical microscope image of the emulsion in Comparative Example 1 of this application;

[0039] Figure 14 This is an optical microscope image of the emulsion in Comparative Example 2 of this application;

[0040] Figure 15 This is a Vickers hardness indentation diagram of Example 1 of this application;

[0041] Figure 16 This is a Vickers hardness indentation diagram of Example 2 of this application;

[0042] Figure 17 This is a Vickers hardness indentation diagram of Example 3 of this application;

[0043] Figure 18 This is a Vickers hardness indentation diagram of Example 4 of this application;

[0044] Figure 19 This is a Vickers hardness indentation diagram of Example 5 of this application;

[0045] Figure 20 This is a Vickers hardness indentation diagram of Comparative Example 1 of this application;

[0046] Figure 21 This is a Vickers hardness indentation diagram of Comparative Example 2 of this application. Detailed Implementation

[0047] This invention provides a method for preparing highly spherical zirconia microspheres based on a controllable emulsion template method. The core design concept is as follows: using a water-in-oil emulsion as a template, the interfacial tension between oil and water is controlled by a compound emulsifier, and a suitable oil-to-water ratio and stirring intensity are combined to form uniform and stable emulsion droplets. The microsphere morphology is then locked by isothermal curing, and finally, a three-stage stepped sintering process is used to achieve sufficient densification and inhibit abnormal grain growth. Specifically, the method includes the following steps: emulsion system preparation, emulsion dispersion and curing, microsphere separation and cleaning, and drying and sintering. The aqueous phase of the zirconia precursor is yttrium-stabilized zirconia sol or a mixed solution containing yttrium salt and zirconium salt, with a yttrium molar fraction of 2-5 mol%; the compound emulsifier is Span-80 and Tween-80 in a mass ratio of 2:1-4:1, a total concentration of 2-3%, and an oil-water volume ratio of 3:1-5:1; the stirring intensity is 800-1500 rpm; the isothermal curing temperature is 50-65℃, and the time is 1-3 h; the three-stage stepped sintering regime is as follows: the first stage is to raise the temperature to 300-400℃ at a rate of 1-3℃ / min and hold for 1-2 h; the second stage is to raise the temperature to 700-800℃ at a rate of 2-5℃ / min and hold for 1-2 h; and the third stage is to raise the temperature to 1350-1400℃ at a rate of 3-8℃ / min and hold for 15-30 min.

[0048] Through the synergistic control of the above three stages of emulsification, curing and sintering, the zirconia microspheres prepared by this invention exhibit excellent performance in several key indicators:

[0049] In the emulsification process, a blend of Span-80 and Tween-80 emulsifiers is used, with their mass ratio controlled between 2:1 and 4:1. This allows for precise control of the system's HLB value, forming a dense and stable composite interfacial film at the oil-water interface. This interfacial film exhibits high interfacial viscoelasticity and low interfacial tension, effectively reducing droplet aggregation and improving the emulsion's kinetic stability. Compared to single emulsifiers, the blended system more readily forms fine droplets with a concentrated size distribution under shear and agitation. The particle size span ((D90-D10) / D50) of the resulting microspheres after solidification can be controlled within 1.8, and the sphericity can reach over 97%.

[0050] In the curing process, this invention employs a constant temperature curing of 50-65℃ for 1-3 hours to avoid excessive solvent evaporation and uneven gel shrinkage caused by excessively high temperatures or rapid heating. Under these mild conditions, the gel network forms slowly, and the internal stress is gradually released, resulting in microspheres with smooth surfaces and intact spherical shapes. This effectively suppresses surface wrinkling, cracking, or tailing phenomena that easily occur during rapid curing, providing a crucial guarantee for achieving a roundness of not less than 97%.

[0051] In the sintering process, the three-stage stepped sintering system designed in this invention achieves multiple technical effects: the low-temperature stage promotes the full pyrolysis and discharge of emulsifiers and residual solvents, preventing gas accumulation that could cause cracking or porosity; the medium-temperature stage allows grain boundary diffusion to dominate initial densification, eliminating porosity and inhibiting grain coarsening; the high-temperature stage achieves rapid densification, and due to the short holding time, effectively limits grain boundary migration and prevents abnormal grain growth. Compared to the comparative example where directly heating to 1400℃ resulted in abnormal grain growth, a decrease in Vickers hardness to 1150, and a density of only 6.00 g / cm³, the microspheres of this invention have a density of no less than 6.05 g / cm³ and a Vickers hardness (HV3) of no less than 1250.

[0052] Through a holistic and synergistic design of emulsification, curing, and sintering, this invention achieves multi-scale structural control: the emulsification stage determines the initial droplet size and sphericity; the curing stage fixes the microsphere morphology and imparts initial strength; and the sintering stage enhances density and hardness. The coupling of these three stages results in microspheres that outperform existing technologies in four dimensions: sphericity (≥97%), particle size distribution (≤1.8), density (≥6.05 g / cm³), and hardness (HV3≥1250). Simultaneously, key process parameters such as oil-water ratio (3:1~5:1), stirring intensity (800~1500 rpm), and heating rate have a wide adjustable range, demonstrating strong adaptability to different raw materials and equipment conditions, and possessing excellent potential for pilot-scale amplification and industrial-scale promotion.

[0053] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments listed do not limit the scope of protection of the present invention.

[0054] Example 1

[0055] (1) Preparation of emulsion system: Yttrium stabilized zirconia sol (yttrium content 3 mol%) was prepared as the aqueous phase; the oil phase was liquid paraffin, and Span-80 and Tween-80 were used as a compound emulsifier with a mass ratio of 4:1 and a concentration of 2%; the oil-water volume ratio was 4:1.

[0056] (2) Emulsion dispersion and curing: Emulsify at 1000 rpm for 30 min to form a uniform emulsion; then cure at 60℃ for 2 h to solidify the emulsion droplets into gel microbeads;

[0057] (3) Microbead separation and cleaning: The gel microbeads were separated by centrifugation and washed three times with petroleum ether to remove the surface oil phase and emulsifier;

[0058] (4) Drying and sintering: After drying at 60℃ for 12 h, three-stage sintering is adopted: 2℃ / min, heating to 400℃ / 2 h → 3℃ / min, heating to 800℃ / 1 h → 5℃ / min, heating to 1400℃ / 30 min, and then naturally cooling to room temperature.

[0059] Example 2

[0060] (1) Span-80 and Tween-80 were used as a compound emulsifier with a mass ratio of 3:1 and a total concentration of 2.5%; the oil-water volume ratio was 3:1.

[0061] (2) The stirring intensity is 1200 rpm, the emulsification time is 30 min, the curing temperature is 55℃, and the curing time is 2.5 h;

[0062] (3) Same as Example 1;

[0063] (4) The sintering process is 2℃ / min, heating to 350℃ / 2 h → 3℃ / min, heating to 750℃ / 1.5 h → 5℃ / min, heating to 1380℃ / 20 min, and then naturally cooling to room temperature.

[0064] Example 3

[0065] (1) Emulsifier: Span-80 and Tween-80 are compounded emulsifiers with a mass ratio of 4:1 and a concentration of 2%; oil-water ratio: 5:1;

[0066] (2) Stirring intensity: 1000 rpm;

[0067] (3) Curing temperature: 60℃, time: 2 h;

[0068] (4) Sintering process: 2℃ / min, heating to 400℃ / 2 h → 3℃ / min, heating to 800℃ / 1 h → 5℃ / min, heating to 1400℃ / 30 min, and then naturally cooling to room temperature.

[0069] Example 4

[0070] (1) Emulsifier: Span-80 and Tween-80 compound emulsifier were used at a mass ratio of 3:1 and a concentration of 2%; oil-water ratio: 4:1;

[0071] (2) Stirring intensity: 1500 rpm;

[0072] (3) Curing temperature: 60℃, time: 2 h;

[0073] (4) Sintering process: 2℃ / min, heating to 400℃ / 2 h → 3℃ / min, heating to 800℃ / 1 h → 5℃ / min, heating to 1400℃ / 30 min, and then naturally cooling to room temperature.

[0074] Example 5

[0075] (1) Emulsifier: Span-80: Tween-80 = 3:1, total concentration 2.5%; oil-water ratio: 4:1;

[0076] (2) Stirring intensity: 1200 rpm;

[0077] (3) Curing temperature: 55℃, time: 2.5 h;

[0078] (4) Sintering process: 2℃ / min, heating to 300℃ / 2 h → 3℃ / min, heating to 700℃ / 2 h → 5℃ / min, heating to 1350℃ / 15 min, and then naturally cooling to room temperature.

[0079] Comparative Example 1

[0080] (1) Emulsifier: single Span-80, concentration 1%; oil-water ratio: 2:1 (traditional emulsion method);

[0081] (2) Stirring intensity: 1000 rpm;

[0082] (3) Curing temperature: 80℃, time: 1 h;

[0083] (4) Sintering process: 2℃ / min, heating to 300℃ / 2 h → 3℃ / min, heating to 700℃ / 2 h → 2℃ / min, heating to 1350℃ / 15 min, and then naturally cooling to room temperature.

[0084] Comparative Example 2

[0085] (1) Emulsifier: Span-80: Tween-80 = 3:1, total concentration 2.5%; oil-water ratio: 4:1;

[0086] (2) Stirring intensity: 1000 rpm;

[0087] (3) Curing temperature: 60℃, time: 2 h;

[0088] (4) Sintering process: directly heat to 1400℃ / 1 h at 5℃ / min, and then cool naturally to room temperature (without step).

[0089] Table 1 Comparison of Experimental Data and Results

[0090] Example 1 97.2 1.80 6.06 1250 Example 2 97.5 1.70 6.05 1280 Example 3 97.1 1.80 6.06 1260 Example 4 97.8 1.75 6.07 1260 Example 5 98.1 1.65 6.06 1300 Comparative Example 1 88.5 2.50 6.02 1050 Comparative Example 2 92.0 2.10 6.00 1150

[0091] Figures 1-5 The images shown are SEM images of the zirconia microspheres prepared in Examples 1-5 of this invention, showing that the microspheres have smooth surfaces, intact spherical shapes, and no obvious defects or cracks.

[0092] Figures 6-7The images show SEM images of the zirconia microspheres prepared in Comparative Example 1 and Comparative Example 2, respectively. The microspheres in Comparative Example 1 have poor sphericity and rough surface, while those in Comparative Example 2 have abnormal grain growth and surface pores.

[0093] Figures 8-12 The images shown are optical microscope images of the emulsion stage in Examples 1-5 of the present invention, showing that the emulsion droplets are of uniform size, have clear interfaces, and show no obvious aggregation.

[0094] Figures 13-14 The images are optical microscope images of Comparative Example 1 and Comparative Example 2 during the emulsion stage, respectively. Comparative Example 1 shows a wide droplet size distribution and obvious aggregation, while Comparative Example 2 shows poor droplet stability.

[0095] Figures 15-19 The images shown are Vickers hardness indentation diagrams of the microspheres prepared in Examples 1-5 of this invention. The regularity of the indentation and the small crack propagation indicate that the microspheres have high density and excellent hardness.

[0096] Figures 20-21 The images show Vickers hardness indentation diagrams of the microspheres prepared in Comparative Example 1 and Comparative Example 2, respectively. Obvious cracks or larger indentation sizes are visible around the indentation, indicating that the hardness and density are lower than those of the embodiments of the present invention.

[0097] In this embodiment of the invention, the optical microscope magnification is 25x; Regarding Vickers hardness calculation: Standard requirement: GB / T 4340 stipulates that D1 and D2 must be measured simultaneously and the average value taken. The Vickers hardness formula is as follows: d = (D1 + D2) / 2, HV = 1.8544 × F / d 2 , Wherein, D1: length of the first diagonal of the indentation (horizontal direction), D2: length of the second diagonal perpendicular to D1 (vertical direction), F: test force (kgf), d: arithmetic mean of D1 and D2 (μm).

[0098] Table 2 Test Data .

[0099] This invention significantly improves the overall performance of zirconia microspheres through synergistic innovation of emulsion system optimization, constant temperature curing process and three-stage sintering system. In the emulsification stage, a compound emulsifier of Span-80 and Tween-80 (as in Examples 2 and 5) is used. The interfacial tension is controlled by the hydrophilic-lipophilic balance (HLB) value to form a dense interfacial film, which significantly improves the stability and monodispersity of the emulsion. Compared with the problems of large droplets, low roundness (88.5%), and wide particle size range ((D90-D10) / D50=2.5) caused by a single emulsifier in Comparative Example 1, the roundness of the microspheres in this invention reaches up to 98.1%, and ((D90-D10) / D50) is as low as 1.65. In the curing stage, constant temperature curing is used to avoid shrinkage and cracking of the gel due to sudden temperature changes, ensuring the regularity of the microsphere morphology. In contrast, the high temperature and rapid curing (80℃ / 1 h) in Comparative Example 1 caused uneven shrinkage of the microsphere surface and a decrease in roundness. In the sintering stage, a three-stage stepped sintering system of "low temperature slow rise - medium temperature heat preservation - high temperature short time" is pioneered (e.g., 300℃ / 2 h → The process involves heating the microspheres from 700℃ for 2 hours to 1350℃ for 15 minutes, ensuring sufficient glue removal, grain suppression, and densification. Compared to Comparative Example 2, which resulted in abnormal grain growth, a decrease in Vickers hardness (HV3) (1150), and insufficient density (6.00 g / cm³) due to directly heating to 1400℃, the microspheres of this invention have a density higher than 6.05 g / cm³ and a Vickers hardness (HV3) exceeding 1250. The overall performance is superior to the existing technology, and the process has a wide processing window and strong scalability, showing significant prospects for industrial application.

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing highly spherical zirconia microspheres based on a controllable emulsion template method, characterized in that, Includes the following steps: S1 emulsion system preparation: The aqueous phase of the zirconium oxide precursor is added to the oil phase containing the compound emulsifier, and a stable water-in-oil emulsion is formed under stirring conditions; S2 Emulsion Dispersion and Curing: The emulsion is dispersed evenly under stirring intensity, then cured at low temperature and kept at a warm temperature to solidify the emulsion droplets into gel microbeads; S3 Microbead Separation and Cleaning: The cured gel microbeads are separated from the oil phase and cleaned with organic solvents to remove surface oil phase and emulsifier residues; S4 Drying and Sintering: The cleaned microspheres are dried and then heat-treated using a three-stage stepped sintering process to obtain high-roundness zirconia microspheres.

2. The method for preparing highly spherical zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The compound emulsifier is Span-80 and Tween-80, with a mass ratio of 2:1 to 4:1, a total concentration of 2-3%, and an oil-water volume ratio of 3:1 to 5:

1.

3. The method for preparing highly spherical zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The stirring intensity is 800-1500 rpm; the low-temperature curing temperature is 50-65℃, and the curing time is 1-3h.

4. The method for preparing highly spherical zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The three-stage stepped sintering process includes: First stage: Increase the temperature to 300-400℃ at a rate of 1-3℃ / min and hold for 1-2 hours; Second stage: Increase the temperature to 700-800℃ at a rate of 2-5℃ / min and hold for 1-2 hours; The third stage: raise the temperature to 1350-1400℃ at a rate of 3-8℃ / min, hold for 15-30 min, and then allow it to cool naturally or slowly to room temperature.

5. The method for preparing highly spherical zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The aqueous phase of the zirconia precursor is a yttrium-stabilized zirconia sol or a mixed solution containing yttrium salt and zirconium salt, wherein the molar fraction of yttrium is 2-5 mol.

6. The method for preparing highly spherical zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The organic solvent is one or more of petroleum ether, ethanol, or acetone, and the number of cleaning cycles is 2-4.

7. The method for preparing high-sphericity zirconia microspheres based on the controllable emulsion template method according to claim 1, characterized in that, The drying temperature is 50-65℃, and the drying time is 10-14 h.

8. The highly rounded zirconia microspheres prepared by the method according to any one of claims 1-7, characterized in that, The microspheres have a roundness ≥97%, a particle size span ≤1.8, a density ≥6.05 g / cm³, and a Vickers hardness HV3 ≥1250.

9. The high-sphericity zirconia microspheres according to claim 8, characterized in that, The particle size distribution of the microspheres was determined by a laser particle size analyzer, where D10, D50, and D90 represent the particle size values ​​when the cumulative distribution is 10%, 50%, and 90%, respectively.

10. The application of high-roundness zirconia microspheres prepared by the method according to any one of claims 1-7 in high-end grinding media, catalyst supports, biomedical materials or precision polishing materials.

Images