Preparation method and application of micron-sized Y-Ca co-doped zirconia ceramic microspheres

Abstract

The application relates to the field of ceramic materials, and discloses a preparation method and application of micron Y-Ca co-doped zirconia ceramic microspheres. The preparation method comprises the following steps: S1: dissolving a zirconium-containing compound and a yttrium-containing compound in water to obtain an aqueous phase A; dissolving a calcium-containing compound in water to obtain an aqueous phase B; S2: preparing an oil phase; S3: adding the aqueous phase A into the oil phase and stirring to obtain an emulsion; S4: adding urea and hexamethylenetetramine into the emulsion and stirring to obtain gel microspheres; S5: washing, centrifuging and drying the gel microspheres, immersing the gel microspheres in the aqueous phase B, and evaporating water under reduced pressure to obtain gel microspheres loaded with the calcium-containing compound; and S6: low-temperature pre-burning and high-temperature sintering to obtain micron Y-Ca co-doped zirconia ceramic microspheres. The micron Y-Ca co-doped zirconia ceramic microspheres prepared by the application are excellent in compactness, mechanical properties and thermal stability, and controllable in morphology and uniform in size distribution.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and more particularly to a method for preparing and applying micron-sized Y-Ca co-doped zirconia ceramic microspheres. Background Technology

[0002] Powder preparation is divided into physical and chemical methods. Chemical methods are limited in application due to high cost and difficulty in removing introduced impurities. Physical methods, on the other hand, utilize the interaction of mechanical forces and grinding media to obtain powders with high purity and controllable fineness. Therefore, grinding media balls play a crucial role in the grinding field. Among them, zirconia ceramic microspheres, due to their high specific gravity, low wear, and non-polluting properties, surpass traditional alumina ceramics to become the most widely used product in high-efficiency grinding.

[0003] Zirconia is stable in its monoclinic phase under normal pressure and temperature. The transformation from monoclinic to tetragonal phases leads to volume changes, resulting in cracks and even initiation of fissures. Currently, stabilization is often achieved by dissolving a second-phase oxide into ZrO2. This process allows the tetragonal phase of zirconium oxide, which provides phase transformation toughening, to be maintained at room temperature. Stabilization treatment often involves... 4+ Cation-substituted Zr with ionic radii less than 12% 4+ Ions form substitutional solid solutions, thereby preventing crystal transformation. Common cations include: Y. 2+ Ca 2+ Mg 2+ Ce 4+ Among these, Y-doped zirconia ceramics exhibit excellent mechanical properties, high strength, and good fracture toughness, with fine and uniform grain size and a low firing temperature. However, long-term use at 100-400℃ can lead to a phase transformation, resulting in a decrease in mechanical properties. Ca-doped zirconia is less expensive and offers excellent high-temperature chemical stability and thermal shock resistance, but its overall performance, including density and mechanical properties, is inferior to that of Y-doped stable zirconia. Furthermore, due to limitations in traditional rolling and die-forming processes, the currently produced spheres have a large size distribution, primarily in the millimeter range. Summary of the Invention

[0004] To overcome the problems of poor thermal stability of existing yttrium oxide (Y₂O₃)-doped zirconia ceramic microspheres and poor density and mechanical properties of calcium oxide (CaO)-doped zirconia ceramic microspheres, this invention provides a method for preparing and applying micron-sized Y-Ca co-doped zirconia ceramic microspheres. The zirconia ceramic microspheres prepared by this invention have micron-sized particles and exhibit excellent mechanical properties, density, and thermal stability.

[0005] The specific technical solution of this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing micron-sized Y-Ca co-doped zirconium oxide ceramic microspheres, comprising: S1: dissolving a zirconium-containing compound and a yttrium-containing compound in water to obtain an aqueous phase A; dissolving a calcium-containing compound in water to obtain an aqueous phase B;

[0007] S2: Add the emulsifier to cyclohexane and stir until homogeneous to obtain the oil phase;

[0008] S3: Add aqueous phase A to the oil phase and stir to obtain an emulsion;

[0009] S4: Add urea and hexamethylenetetramine to the emulsion and stir to obtain gel microspheres;

[0010] S5: After washing, centrifuging and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium-containing compounds.

[0011] S6: After sequentially pre-firing and sintering the gel microspheres loaded with calcium compounds at low temperature, micron-sized Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0012] First, to overcome the shortcomings of single Y-doped or Ca-doped zirconia ceramics, this invention employs Y-Ca co-doping to compensate for the deficiencies of a single stabilizer, resulting in zirconia ceramic microspheres with excellent density, mechanical properties, and thermal stability. This invention further discovers that not all co-doping methods yield ideal results. Simultaneous Y and Ca doping using traditional methods yields poor results because the two ions compete for space and cannot completely dissolve into the ZrO2 lattice, making it difficult to achieve the desired doping effect. Therefore, this invention finds that doping Y first and then Ca achieves better co-doping results. This is because the ionic radius of ZrO2 is... 4+ <Y 3+ <Ca 2+ Adding Y (a small ionic radius) first, followed by Ca, ensures that both are fully dissolved and incorporated into the ZrO2 lattice. To achieve sequential Y and Ca doping, this invention first prepares zirconium- and yttrium-containing gel microspheres using a sol-gel + microemulsion method, adding urea and hexamethylenetetramine. These microspheres are then immersed in a calcium-containing compound solution, and during vacuum evaporation, the calcium-containing compound is enriched within the gel microspheres. At this point, the yttrium-containing compound is uniformly distributed within the gel microspheres, while the calcium-containing compound is mainly concentrated on the surface. During subsequent sintering and solution treatment, because Ca needs to slowly diffuse into the interior of the microspheres after the calcium compound pyrolyzes before entering the zirconium oxide lattice for solid solution doping, the yttrium compound will first enter the zirconium oxide lattice after pyrolysis to achieve solid solution doping. Therefore, in the final zirconium oxide microspheres, except for the surface region, most of the microspheres achieve the effect of Y doping followed by Ca doping.

[0013] Secondly, compared with traditional microsphere preparation methods such as melting and rolling, this invention discovers that the "sol-gel method" combined with the "microemulsion method" for preparing zirconia ceramic microspheres can overcome the shortcomings of the melting method in terms of its lack of universality for ceramic material systems, and can overcome the defects of insufficient surface sphericity and easy hollowing and delamination of ceramic microspheres prepared by the rolling method. Furthermore, the ceramic microspheres prepared by the method of this invention have micron-level dimensions and uniform size distribution.

[0014] Furthermore, this invention discovers that the sintering process has a significant impact on the performance of Y-Ca co-doped zirconia ceramic microspheres. To further improve performance, this invention employs a two-step sintering method of "low-temperature pre-firing - high-temperature sintering," which has the following effects: Firstly, it allows organic matter to fully volatilize during the low-temperature pre-firing stage, preventing cracking of the ceramic spheres due to volatilization at high temperatures; secondly, the two-step sintering method facilitates the solidification and densification of the ceramic microspheres, endowing them with high wear resistance and thermal shock resistance. This is because pre-firing at a lower temperature allows for preliminary sintering, removing organic matter, eliminating some residual gases, and reducing the porosity of the zirconia ceramic; then, high-temperature sintering allows the crystal particles in the ceramic raw material to be more densely combined, forming a fully sintered blocky or dense structure, increasing the density and hardness of the zirconia ceramic, and giving it excellent performance.

[0015] Preferably, in S1, the molar ratio of yttrium to calcium in the yttrium-containing compound and the calcium-containing compound is (2.6:1.6)-(3.2:1), and the total doping amount is 3.8-4.2 mol%.

[0016] This invention reveals that controlling the yttrium to calcium ratio within the aforementioned range yields Y-Ca co-doped zirconia ceramic microspheres with superior performance. If the total yttrium and calcium doping amount is too low, some tetragonal zirconia will transform into monoclinic zirconia, a process accompanied by a 7% volume expansion, which can easily lead to product cracking. Conversely, if the total yttrium and calcium doping amount is too high, it not only increases costs but also negatively impacts the mechanical and thermal properties of the product. Furthermore, an imbalanced yttrium to calcium ratio also negatively affects product performance. Excessive yttrium content reduces the product's lifespan, while excessive calcium content reduces its density and mechanical properties.

[0017] Preferably, in S1, the zirconium-containing compound is zirconium oxychloride octahydrate (ZrOCl2·8H2O); the yttrium-containing compound is yttrium chloride hexahydrate; and the calcium-containing compound is calcium chloride.

[0018] Preferably, in S2, the emulsifier is Span-80 or Tween-85.

[0019] Preferably, in S2, the volume ratio of cyclohexane, Span 80, and Tween 85 in the oil phase is 100:(2-4):(0.5-1.5). Preferably, in S3, the mass ratio of the oil phase to the aqueous phase A is (0.8-1.2):1.

[0020] Preferably, in S3, the stirring speed is 1500-2000 rpm and the stirring time is 20-40 min.

[0021] Preferably, in S4, the molar ratio of urea to zirconium is 1.3-1.5:1; and the molar ratio of hexamethylenetetramine to zirconium is 1.1-1.2:1.

[0022] Preferably, in S6, the heating rate of the low-temperature pre-firing is 3-7℃ / min, the calcination temperature is 800-1000℃, and the holding time is 1-2h; the heating rate of the high-temperature sintering is 2-3℃ / min, the sintering temperature is 1300-1500℃, and the holding time is 2-6h.

[0023] This invention limits the parameters for low-temperature pre-firing and high-temperature sintering to the aforementioned ranges: If the pre-firing temperature is too low (<800℃), organic matter will not burn off completely, remaining in the material. These residues may volatilize during high-temperature sintering, causing porosity or other defects. If the pre-firing temperature is too high (>1000℃), some raw materials will sinter prematurely, resulting in uneven crystal growth. This may lead to uneven bonding between crystals during subsequent high-temperature sintering, affecting the overall density and mechanical properties of the material. Similarly, if the temperature in the high-temperature stage is too low (<1300℃), the crystal growth rate will be slow, resulting in incomplete or uneven sintering, thus affecting the density and mechanical properties of the material. If the temperature in the high-temperature stage is too high (>1500℃), the crystal growth rate will be too fast, causing excessively large and rapid grain growth, thus affecting the density and mechanical properties of zirconia ceramics. This may lead to an increase in defects at grain boundaries, reducing the material's strength and wear resistance.

[0024] Preferably, in S6, the particle size distribution range of the micron-sized Y-Ca co-doped zirconia ceramic microspheres is 100-1000 μm.

[0025] Preferably, the micron-sized Y-Ca co-doped zirconia ceramic microspheres have a Vickers hardness ≥15.4 GPa, a wear rate ≤0.025% / h, and a coefficient of thermal expansion ≤8.2×10⁻⁶. -6 / ℃.

[0026] Secondly, the present invention provides the application of micron-sized Y-Ca co-doped zirconia ceramic microspheres obtained by the above preparation method as grinding media balls.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] (1) The present invention uses a special method of first Y doping and then Ca doping to prepare Y-Ca co-doped zirconia ceramic microspheres, which can effectively overcome the shortcomings of single Y doping or Ca doping of zirconia ceramics, and can obtain zirconia ceramic microspheres with excellent density, mechanical properties and thermal stability.

[0029] (2) The present invention uses a process combining the "sol-gel method" and the "microemulsion method" to prepare Y-Ca co-doped zirconia ceramic microspheres, which can obtain ceramic microspheres with controllable morphology, uniform size distribution, high hardness and good thermal stability.

[0030] (3) The present invention adopts a low-temperature pre-firing-high-temperature sintering process, which can ensure the densification of zirconia spheres, improve the sintering activity of zirconia, and obtain high-hardness solid micron-sized Y-Ca co-doped zirconia ceramic microspheres.

[0031] (4) The preparation process provided by the present invention is simple and easy to implement, and the product has stable performance and is suitable for industrial production. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments.

[0033] The general embodiment describes a method for preparing micron-sized Y-Ca co-doped zirconia ceramic microspheres, comprising:

[0034] S1: Dissolving zirconium-containing compounds and yttrium-containing compounds in water yields aqueous phase A; dissolving calcium-containing compounds in water yields aqueous phase B;

[0035] S2: Add the emulsifier to cyclohexane and stir until homogeneous to obtain the oil phase;

[0036] S3: Add aqueous phase A to the oil phase and stir to obtain an emulsion;

[0037] S4: Add urea and hexamethylenetetramine to the emulsion and stir to obtain gel microspheres;

[0038] S5: After washing, centrifuging and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium-containing compounds.

[0039] S6: After sequentially pre-firing and sintering the gel microspheres loaded with calcium compounds at low temperature, micron-sized Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0040] In some specific implementations, the molar ratio of yttrium to calcium in the yttrium-containing and calcium-containing compounds in S1 is (2.6:1.6)-(3.2:1), and the total doping amount is 3.8-4.2 mol%.

[0041] In some specific implementation examples, the zirconium-containing compound in S1 is zirconium oxychloride octahydrate (ZrOCl2·8H2O); the yttrium-containing compound is yttrium chloride hexahydrate (YCl3·6H2O); and the calcium-containing compound is calcium chloride (CaCl2).

[0042] In some specific implementations, the emulsifiers in S2 are Span-80 and Tween-85.

[0043] In some specific implementations, the volume ratio of cyclohexane, Span 80, and Tween 85 in the oil phase of S2 is 100:(2-4):(0.5-1.5). In some specific implementations, the mass ratio of the oil phase to the aqueous phase A in S3 is (0.8-1.2):1.

[0044] In some specific implementation cases, the stirring speed in S3 is 1500-2000 rpm, and the stirring time is 20-40 min.

[0045] In some specific implementation examples, the molar ratio of urea to zirconium in S4 is 1.3-1.5:1; the molar ratio of hexamethylenetetramine to zirconium is 1.1-1.2:1.

[0046] In some specific implementation cases, the heating rate of the low-temperature pre-firing in S6 is 3-7℃ / min, the calcination temperature is 800-1000℃, and the holding time is 1-2h; the heating rate of the high-temperature sintering is 2-3℃ / min, the sintering temperature is 1300-1500℃, and the holding time is 2-6h.

[0047] In some specific implementation examples, the micron-sized Y-Ca co-doped zirconia ceramic microspheres in S6 have a particle size distribution range of 100-1000 μm, a Vickers hardness ≥15.4 GPa, a wear rate ≤0.025% / h, and a coefficient of thermal expansion ≤8.2×10⁻⁶. -6 / ℃.

[0048] Specific embodiments and comparative examples

[0049] (I) Comparison of different Y and Ca doping levels

[0050] Comparative Example 1:

[0051] The raw material ratio of Y-doped ZrO2 powder in this comparative example is as follows: the molar ratio of Y to ZrO2 is 4.2 mol%.

[0052] The specific steps are as follows:

[0053] (1) According to the molar ratio of Y to ZrO2 of 4.2 mol%, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and yttrium chloride hexahydrate were dissolved in water to obtain an aqueous phase;

[0054] (2) Add 3ml Span-80 and 1ml Tween 85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0055] (3) Add the aqueous phase to the oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain an emulsion.

[0056] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0057] (5) After washing, centrifugation, drying, low-temperature pre-calcination, high-temperature sintering, and flotation, micron-sized Y-doped ZrO2 ceramic microspheres of suitable particle size can be obtained. The low-temperature pre-calcination process is as follows: heating rate 5℃ / min, calcination temperature 1000℃, and holding time 1h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1400℃, and holding time 4h; Y-doped zirconia ceramic microspheres are obtained.

[0058] Comparative Example 2:

[0059] The raw material ratio of Y-Ca co-doped ZrO2 powder in this comparative example is as follows: the molar percentages of Y and Ca in ZrO2 are 3.4 mol% and 0.8 mol%, respectively.

[0060] The specific steps are as follows:

[0061] (1) According to the molar ratio of Y and Ca to ZrO2 of 3.4 mol% and 0.8 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and yttrium chloride hexahydrate were dissolved in water to obtain aqueous phase A, and calcium chloride was dissolved in water to obtain aqueous phase B;

[0062] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0063] (3) Add aqueous phase A to oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain emulsion;

[0064] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0065] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0066] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 850℃, and holding time 2h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1350℃, and holding time 3h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0067] Example 1

[0068] The Y-Ca co-doped ZrO2 powder raw material ratio in this embodiment is as follows: the molar percentages of Y and Ca in ZrO2 are 3.2 mol% and 1.0 mol%, respectively.

[0069] The specific steps are as follows:

[0070] (1) According to the molar ratio of Y and Ca to ZrO2 of 3.2 mol% and 1.0 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and yttrium chloride hexahydrate are dissolved in water to obtain aqueous phase A, and calcium chloride is dissolved in water to obtain aqueous phase B;

[0071] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0072] (3) Add aqueous phase A to oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain emulsion;

[0073] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0074] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0075] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 850℃, and holding time 2h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1350℃, and holding time 3h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0076] Example 2:

[0077] The Y-Ca co-doped ZrO2 powder raw material ratio in this embodiment is as follows: the molar percentages of Y and Ca in ZrO2 are 2.8 mol% and 1.4 mol%, respectively.

[0078] The specific steps are as follows:

[0079] (1) According to the molar ratio of Y and Ca to ZrO2 of 2.8 mol% and 1.4 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and yttrium chloride hexahydrate are dissolved in water to obtain aqueous phase A, and calcium chloride is dissolved in water to obtain aqueous phase B;

[0080] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0081] (3) Add aqueous phase A to oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain emulsion;

[0082] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0083] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0084] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 850℃, and holding time 2h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1350℃, and holding time 3h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0085] Example 3:

[0086] The Y-Ca co-doped ZrO2 powder raw material ratio in this embodiment is as follows: the molar percentages of Y and Ca in ZrO2 are 2.6 mol% and 1.6 mol%, respectively.

[0087] The specific steps are as follows:

[0088] (1) According to the molar ratio of Y and Ca to ZrO2 being 2.6 mol% and 1.6 mol% respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O), yttrium chloride hexahydrate (YCl3·6H2O), and calcium chloride (CaCl2) were dissolved in water to obtain an aqueous phase;

[0089] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0090] (3) Add the aqueous phase to the oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain an emulsion.

[0091] (4) According to the relationship between urea and hexamethylenetetramine and ZrO 2 After adding the ingredients at a molar ratio of 1.40:1 and 1.18:1 and continuing to stir, gel microspheres were obtained.

[0092] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0093] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 900℃, and holding time 1h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1400℃, and holding time 3h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0094] Comparative Example 3:

[0095] The raw material ratio of Y-Ca co-doped ZrO2 powder in this comparative example is as follows: the molar percentages of Y and Ca in ZrO2 are 2.4 mol% and 1.8 mol%, respectively.

[0096] The specific steps are as follows:

[0097] (1) According to the molar ratio of Y and Ca to ZrO2 being 2.4 mol% and 1.8 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O), yttrium chloride hexahydrate (YCl3·6H2O), and calcium chloride (CaCl2) were dissolved in water to obtain an aqueous phase;

[0098] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0099] (3) Add the aqueous phase to the oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain an emulsion.

[0100] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0101] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0102] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 900℃, and holding time 1h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1450℃, and holding time 3.5h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0103] Comparative Example 4:

[0104] The raw material ratio of Ca-doped ZrO2 powder in this comparative example is as follows: the molar ratio of Ca to ZrO2 is 4.2 mol%.

[0105] The specific steps are as follows:

[0106] (1) According to the molar ratio of Ca to ZrO2 of 4.2 mol%, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and calcium chloride were dissolved in water to obtain an aqueous phase;

[0107] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0108] (3) Add the aqueous phase to the oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain an emulsion.

[0109] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0110] (5) After washing, centrifugation, drying, low-temperature pre-calcination, high-temperature sintering, and flotation, micron-sized Ca co-doped ZrO2 ceramic microspheres of suitable particle size can be obtained. The low-temperature pre-calcination process is as follows: heating rate 5℃ / min, calcination temperature 900℃, and holding time 1h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1450℃, and holding time 3.5h; Ca-doped zirconia ceramic microspheres are obtained.

[0111] (II) Comparison of different Y and Ca doping orders

[0112] Comparative Example 5

[0113] This comparative example uses simultaneous doping with Y and Ca. The raw material ratio of Ca-Y co-doped ZrO2 powder is as follows: the molar percentages of Y and Ca in ZrO2 are 3.2 mol% and 1.0 mol%, respectively.

[0114] The specific steps are as follows:

[0115] (1) According to the molar ratio of Y and Ca to ZrO2 of 3.2 mol% and 1.0 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O), calcium chloride and yttrium chloride hexahydrate were dissolved in water to obtain an aqueous phase;

[0116] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0117] (3) Add the aqueous phase to the oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain an emulsion.

[0118] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0119] (5) After washing, centrifugation, drying, low-temperature pre-calcination, high-temperature sintering, and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-calcination process is as follows: heating rate 5℃ / min, calcination temperature 850℃, and holding time 2h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1350℃, and holding time 3h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0120] Comparative Example 6

[0121] This comparative example uses a doping order of Ca first, followed by Y. The Ca-Y co-doped ZrO2 powder raw material ratio is as follows: the molar percentages of Y and Ca in ZrO2 are 3.2 mol% and 1.0 mol%, respectively.

[0122] The specific steps are as follows:

[0123] (1) According to the molar ratio of Y and Ca to ZrO2 of 3.2 mol% and 1.0 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and calcium chloride are dissolved in water to obtain aqueous phase A, and yttrium chloride hexahydrate is dissolved in water to obtain aqueous phase B;

[0124] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0125] (3) Add aqueous phase A to oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain emulsion;

[0126] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0127] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with yttrium compounds.

[0128] (6) After low-temperature pre-sintering, high-temperature sintering, and flotation, micron-sized Ca-Y co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The low-temperature pre-sintering process is as follows: heating rate 5℃ / min, calcination temperature 850℃, and holding time 2h. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1350℃, and holding time 3h; Ca-Y co-doped zirconia ceramic microspheres are obtained.

[0129] (III) Comparison of different sintering processes

[0130] Comparative Example 7

[0131] This comparative example uses a one-step sintering method. The raw material ratio of Y-Ca co-doped ZrO2 powder is as follows: the molar percentages of Y and Ca in ZrO2 are 3.2 mol% and 1.0 mol%, respectively.

[0132] The specific steps are as follows:

[0133] (1) According to the molar ratio of Y and Ca to ZrO2 of 3.2 mol% and 1.0 mol%, respectively, zirconium oxychloride octahydrate (ZrOCl2·8H2O) and yttrium chloride hexahydrate were dissolved in water to obtain aqueous phase A, and calcium chloride was dissolved in water to obtain aqueous phase B;

[0134] (2) Add 3ml Span-80 and 1ml Tween85 to 100ml cyclohexane and stir until homogeneous to obtain the oil phase;

[0135] (3) Add aqueous phase A to oil phase at a mass ratio of 1:1, and stir (stirring speed is 1600 rpm, stirring time is 30 min) to obtain emulsion;

[0136] (4) After adding urea and hexamethylenetetramine to ZrO2 at molar ratios of 1.40:1 and 1.18:1 respectively, and stirring was continued, gel microspheres were obtained.

[0137] (5) After washing, centrifugation and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds.

[0138] (6) After high-temperature sintering and flotation, micron-sized Y-Ca co-doped ZrO2 ceramic microspheres with suitable particle size can be obtained. The high-temperature sintering process is as follows: heating rate 2.5℃ / min, sintering temperature 1450℃, and holding time 3.5h; Y-Ca co-doped zirconia ceramic microspheres are obtained.

[0139] Performance testing

[0140] The performance of the zirconia ceramic microspheres obtained in each embodiment and comparative example was tested, and the results are shown in the table below:

[0141]

[0142]

[0143] The comparison of the data in the table above shows that:

[0144] (1) Regarding the doping ratio of Y and Ca: The main difference between Comparative Examples 1-2, Examples 1-3, and Comparative Examples 3-4 lies in the different doping ratios of Y and Ca (the doping ratio of Ca increases progressively). Specifically, the performance data shows that Comparative Example 1, without Ca doping, and Comparative Example 4, without Y doping, resulted in poor Vickers hardness, wear rate, and coefficient of thermal expansion of the obtained zirconia ceramic microspheres. In Comparative Example 2, the Ca doping ratio was relatively low, and although the various properties of the zirconia ceramic microspheres were improved compared to Comparative Example 1, they were still not ideal. Under the doping ratios of Examples 1-3, it can be seen that the various properties of the zirconia ceramic microspheres were significantly improved. However, when the Ca doping ratio was high in Comparative Example 3, the various properties of the zirconia ceramic microspheres showed a downward trend.

[0145] (2) Regarding the order of Y and Ca doping: The main difference between Comparative Example 5 and Example 1 is that Y and Ca are doped simultaneously, while Comparative Example 6 does Ca first and then Y. The results show that, regardless of whether Comparative Example 5 or Comparative Example 6 is used, the Vickers hardness, wear rate, and coefficient of thermal expansion of the obtained zirconia ceramic microspheres are significantly worse than those of Example 1. The reason is that Y and Ca compete with each other during the doping process (Y has a weaker doping ability than Ca). According to the doping methods of Comparative Examples 5 and 6, the Y element cannot be fully dissolved into the ZrO2 lattice, making it difficult to obtain the ideal doping effect. (3) Regarding the sintering method: The difference between Comparative Example 7 and Example 1 is that a one-step sintering method is used. The results show that the various properties of the zirconia ceramic microspheres obtained in Comparative Example 7 are significantly worse than those of Example 1. It can be seen that the "low-temperature pre-firing-high-temperature sintering" method specific to this invention is beneficial to improving the various properties of zirconia ceramic microspheres.

[0146] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0147] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing micron-sized Y-Ca co-doped zirconia ceramic microspheres, characterized in that... include: S1: Dissolve zirconium-containing compounds and yttrium-containing compounds in water to obtain aqueous phase A; dissolve calcium-containing compounds in water to obtain aqueous phase B; the molar ratio of yttrium to calcium in the yttrium-containing and calcium-containing compounds is (2.6:1.6)-(3.2:1), and the total doping amount is 3.8-4.2 mol%; S2: Add the emulsifier to cyclohexane and stir until homogeneous to obtain the oil phase; S3: Add aqueous phase A to the oil phase and stir to obtain an emulsion; S4: Add urea and hexamethylenetetramine to the emulsion and stir to obtain gel microspheres; S5: After washing, centrifuging and drying, the gel microspheres are immersed in aqueous phase B and the water is evaporated under reduced pressure to obtain gel microspheres loaded with calcium compounds. S6: Pre-fire the gel microspheres loaded with calcium compounds at a low temperature of 800-1000℃ by heating at 3-7℃ / min and holding for 1-2 hours, then sinter at a high temperature of 1300-1500℃ by heating at 2-3℃ / min and holding for 2-6 hours to obtain micron-sized Y-Ca co-doped zirconia ceramic microspheres.

2. The preparation method according to claim 1, characterized in that: In S1, The zirconium-containing compound is zirconium oxychloride octahydrate; The yttrium-containing compound is yttrium chloride hexahydrate; The calcium-containing compound is calcium chloride.

3. The preparation method according to claim 1, characterized in that: In S2, the emulsifiers are Span 80 and Tween 85.

4. The preparation method according to claim 1, characterized in that: In S2, the volume ratio of cyclohexane, Span 80 and Tween 85 in the oil phase is 100:(2-4):(0.5-1.5).

5. The preparation method according to claim 1, characterized in that: In S3, the mass ratio of the oil phase to the water phase A is (0.8-1.2):

1.

6. The preparation method according to claim 1, characterized in that: In S4, the molar ratio of urea to zirconium is 1.3-1.5:

1.

7. The preparation method according to claim 1, characterized in that: In S4, the molar ratio of hexamethylenetetramine to zirconium is 1.1-1.2:

1.

8. The preparation method according to any one of claims 1-7, characterized in that: In S6, the particle size distribution range of the micron-sized Y-Ca co-doped zirconia ceramic microspheres is 100-1000 μm.

9. The preparation method according to any one of claims 1-7, characterized in that: In S6, the micron-sized Y-Ca co-doped zirconia ceramic microspheres have a Vickers hardness ≥15.4 GPa, a wear rate ≤0.025% / h, and a coefficient of thermal expansion ≤8.2×10⁻⁶. -6 / ℃.

10. The application of micron-sized Y-Ca co-doped zirconia ceramic microspheres obtained by the preparation method according to any one of claims 1-9 as grinding media balls.

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