Zirconium cerium aluminum composite ceramic beads and a preparation process thereof

Abstract

The application relates to the technical field of ceramic materials, in particular to a zirconium-cerium-aluminum composite ceramic bead and a preparation process thereof. The preparation process comprises the following steps: taking zirconium oxychloride octahydrate as a zirconium source, precipitating zirconium oxide hydrate slurry without cerium under the condition of pH 8-9, and dispersing after washing; after pretreatment by citric acid monohydrate and trisodium citrate dihydrate, adding cerium nitrate hexahydrate aqueous solution under the condition of pH 6-7, adding oxalic acid dihydrate aqueous solution in the middle period of cerium salt addition, then adjusting pH to 8.3-8.7 for aging, and obtaining zirconium oxide hydrate composite precursor slurry with cerium-rich outer edge; after filtration, washing, drying and pre-calcination, adding aluminum oxide wet grinding, and then performing spray drying, rolling into balls, glue removal, sintering and self-grinding shaping, the zirconium-cerium-aluminum composite ceramic bead is prepared. The process makes the ceramic bead have the characteristics of high fracture toughness, low abrasion rate and low element pollution, and is suitable for high linear speed wet grinding scenes.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a zirconium-cerium-aluminum composite ceramic bead and its preparation process. Background Technology

[0002] Zirconium-cerium-aluminum composite ceramic beads, as high-efficiency grinding media, are widely used in wet grinding processes in fields such as new energy battery materials and electronic ceramics. Their performance directly affects grinding efficiency and the purity of the ground materials. Currently, the mainstream process in the industry involves directly mixing oxide powders such as zirconium oxide, cerium oxide, and alumina, wet grinding, spray granulation, rolling into balls, and high-temperature sintering. The technical focus is on overall formula optimization, improving mixing uniformity, and controlling sintering density. Typical products, such as commercially available cerium-stabilized zirconium oxide beads, are mostly composed of 82wt% ZrO2, 16wt% CeO2, and approximately 2wt% other components.

[0003] This type of process assumes that the stabilizer should be evenly distributed to achieve the best stabilization effect. However, in actual applications, because the surface of the ceramic bead is subjected to high-frequency impact and shear stress during the grinding process, the evenly distributed cerium cannot specifically enhance the surface's resistance to damage. As a result, the tetragonal zirconium oxide on the surface is prone to transform into the monoclinic phase under hydrothermal conditions, causing microcracks to initiate and propagate, resulting in a persistently high wear rate.

[0004] Meanwhile, in traditional processes, free or poorly bound cerium / aluminum particles are easily detached during grinding and introduced into the slurry, causing contamination of the ground slurry with metallic elements and affecting the performance of downstream products. To reduce wear, some solutions attempt to increase the total amount of cerium oxide added, but this leads to increased material costs and brittleness. Other solutions introduce surface coatings or gradient sintering technology, but these are difficult to scale up due to their complexity and cannot achieve a synergistic optimization of surface cerium concentration and matrix toughness, thus failing to overcome the technical bottleneck of "high wear-high contamination". Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a zirconium-cerium-aluminum composite ceramic bead and its preparation process, so as to solve the problems of insufficient surface phase stability, easy propagation of microcracks, high wear weight loss, and easy introduction of zirconium, cerium and aluminum contamination into the grinding slurry in the existing zirconium-cerium-aluminum composite ceramic beads during high linear speed wet grinding.

[0006] To achieve the above objectives, the present invention provides a process for preparing zirconium-cerium-aluminum composite ceramic beads, comprising the following steps: S1. Using zirconium oxychloride octahydrate as the zirconium source and ammonia water with a mass fraction of 25% as the precipitant, a cerium-free zirconium oxide hydrate precipitate slurry is obtained by precipitation under the condition of pH 8-9. After washing, water is added according to the zirconium oxide equivalent to disperse, and a zirconium oxide hydrate particle dispersion slurry containing 810-830 parts by weight of zirconium oxide is obtained. S2. Pretreatment is carried out by sequentially adding 10-15 parts by weight of citric acid monohydrate and 24-32 parts by weight of trisodium citrate dihydrate to the zirconium oxide hydrate particle dispersion slurry to obtain a pretreated slurry. S3. Add an aqueous solution of cerium nitrate hexahydrate containing 378-429 parts by weight to the pretreated slurry, and maintain the pH of the system at 6-7 with 25% by weight ammonia water during the addition of the aqueous solution of cerium nitrate hexahydrate; when the cumulative amount of the aqueous solution of cerium nitrate hexahydrate added reaches 50%-70% of its total amount, start adding an aqueous solution of oxalate dihydrate containing 5-9 parts by weight within 15-25 minutes, and maintain the pH of the system at 6-7 with 25% by weight ammonia water during the addition of the aqueous solution of oxalate dihydrate; after the addition of the aqueous solution of cerium nitrate hexahydrate is completed, add an aqueous solution of ammonium bicarbonate and 25% by weight ammonia water to raise the pH of the system to 8.3-8.7, and age at 40-42℃ for 100-150 minutes to obtain a cerium-zirconia hydrated composite precursor slurry; S4. The cerium-containing zirconium oxide hydrated composite precursor slurry is filtered, washed, dried, crushed, and pre-calcined at 420-500℃ for 2-4 hours to obtain cerium-containing zirconium oxide pre-calcined powder. S5. After obtaining the cerium-containing zirconium oxide pre-calcined powder, alumina is mixed with the cerium-containing zirconium oxide pre-calcined powder and wet-milled to obtain zirconium-cerium-aluminum wet milling slurry; wherein, based on a total weight of 1000 parts by weight of the cerium-containing zirconium oxide pre-calcined powder and alumina, the alumina is 15-25 parts by weight. S6. Spray dry the zirconium-cerium-aluminum wet grinding slurry to obtain granulated powder, roll the granulated powder into balls, dry, remove the binder, sinter and self-grind to obtain zirconium-cerium-aluminum composite ceramic beads.

[0007] Further, in step S1, the washed wet filter cake sample is taken, dried at 110°C for 2 hours, placed in an air atmosphere furnace, kept at 900°C for 1 hour, cooled and weighed, and the zirconium oxide equivalent in the wet filter cake is calculated based on the mass of the ignition residue.

[0008] Furthermore, in step S2, the citric acid monohydrate is added in the form of an aqueous solution of citric acid monohydrate, which is prepared by 10-15 parts by weight of citric acid monohydrate and 300-320 parts by weight of deionized water; the trisodium citrate dihydrate is added in the form of an aqueous solution of trisodium citrate dihydrate, which is prepared by 24-32 parts by weight of trisodium citrate dihydrate and 500-520 parts by weight of deionized water.

[0009] Furthermore, in step S2, after adding the aqueous solution of citric acid monohydrate, the mixture is stirred at 30°C for 20 minutes; then the aqueous solution of trisodium citrate dihydrate is added, and the mixture is stirred at 30°C for another 40 minutes.

[0010] Furthermore, in step S3, the cerium nitrate hexahydrate aqueous solution is prepared from 378-429 parts by weight of cerium nitrate hexahydrate and 1600 parts by weight of deionized water; the oxalic acid dihydrate aqueous solution is prepared from 5-9 parts by weight of oxalic acid dihydrate and 600-800 parts by weight of deionized water; and the ammonium bicarbonate aqueous solution is prepared from 110-130 parts by weight of ammonium bicarbonate and 1100-1300 parts by weight of deionized water.

[0011] Furthermore, in step S4, the washed filter cake is dried at 110°C for 12 hours, crushed, and passed through an 18-mesh sieve to make the particle size of the crushed powder less than 1 mm.

[0012] Furthermore, in step S5, the slurry is wet-milled at 300-320 r / min for 7-8 hours; after wet milling, the powder D50 of the slurry detected by the laser particle size analyzer is no greater than 500 nm, then filtered through a 200-mesh sieve, and vacuum degassed at 80℃ for 30 minutes.

[0013] Further, in step S6, 8 parts by weight of polyvinyl alcohol and 142 parts by weight of deionized water are weighed, stirred at 90°C for 60 min, and cooled to 30°C to obtain a polyvinyl alcohol aqueous solution; 1000 parts by weight of the granulation powder are weighed, and the polyvinyl alcohol aqueous solution is sprayed at 10 parts by weight / min during the granulation process, with a granulation speed of 35-38 r / min and a granulation time of 40-45 min; green pellets with a particle size of 700-900 μm are sieved and dried at 80°C for 6 h.

[0014] Further, in step S6, the dried green pellets are placed in an air atmosphere furnace, heated to 600℃ at 1℃ / min and held for 2 hours to complete the debinding, then heated to 1240-1260℃ at 3℃ / min and held for 1 hour, then heated to 1360-1400℃ at 2℃ / min and held for 2 hours, and finally cooled to 600℃ at 3℃ / min and cooled with the furnace to obtain sintered ceramic beads; the sintered ceramic beads are added to deionized water and rolled and shaped at 60r / min for 60 minutes, ceramic beads with a particle size of 600-800μm are sieved, washed with deionized water and dried at 120℃ for 4 hours to obtain the zirconium-cerium-aluminum composite ceramic beads.

[0015] Furthermore, the present invention also provides a zirconium-cerium-aluminum composite ceramic bead, obtained by the same preparation process as the zirconium-cerium-aluminum composite ceramic bead.

[0016] Furthermore, the zirconium-cerium-aluminum composite ceramic beads have a particle size of 600-800 μm.

[0017] Furthermore, the Ce / Zr ratio of the cerium outer edge / center of the cerium-containing zirconium oxide pre-calcined powder obtained in step S4 is 1.75-2.13, and the gradient layer thickness is 49-68 nm. The Ce / Zr ratio of the cerium outer edge / center is determined as follows: an energy dispersive spectroscopy line scan is used to test from one outer edge of a single particle through the center of the particle to the other outer edge. The region 0-80 nm from the outer edge of the particle is defined as the outer edge region, and the region 30% of the particle diameter in the center is defined as the center region. The Ce / Zr atomic ratios of the outer edge region and the center region are calculated respectively, and the Ce / Zr atomic ratio of the outer edge region is determined by the ratio of the Ce / Zr atomic ratio of the outer edge region to that of the center region. The gradient layer thickness is the thickness of the continuous outer edge region where the Ce / Zr atomic ratio is more than 10% higher than the average value of the center region.

[0018] The beneficial effects of this invention are: This invention addresses the challenges of surface stability and wear contamination in zirconium-cerium-aluminum composite ceramic beads at the microstructural level through a multi-stage synergistic regulation process involving "peripheral deposition, oxalic acid locking, pre-calcination fixation, and subsequent alumina addition." First, zirconia hydrate particles are pretreated with citrate monohydrate and trisodium citrate dihydrate. Combined with a cerium salt dropwise addition environment at pH 6-7 and the subsequent addition of oxalic acid dihydrate, cerium ions are induced to adsorb directionally onto the outer edge of the zirconium oxide particles, forming a stable complex structure and preventing the precipitation of free cerium in the liquid phase. Subsequently, low-temperature pre-calcination at 420-500℃ irreversibly fixes the cerium distribution structure at the outer edge, preventing diffusion and homogenization of cerium elements during subsequent wet milling and sintering. This ultimately achieves a non-uniform distribution characteristic with a cerium periphery / center Ce / Zr ratio of 1.75-2.13 and a gradient layer thickness of 49-68 nm, significantly improving the surface's resistance to phase transformation (the monoclinic phase increment after aging is only 0.3%-1.0%).

[0019] Secondly, alumina is added after pre-calcination, allowing it to primarily distribute at grain boundaries during sintering, playing a pinning and refining role. This, combined with the cerium edge-reinforcing effect, synergistically improves fracture toughness to 9.65-10.84 MPa·m. 1 / 2 At the same time, it avoids premature participation of alumina in the cerium deposition process, which could interfere with the formation of the gradient structure.

[0020] Furthermore, this structure effectively suppresses surface peeling and element dissolution during the grinding process, reducing the wear rate of the stirred mill to 4.68-6.74 mg / (kg·h) and the total increase in zirconium, cerium, and aluminum elements to 16.8-24.7 mg / kg, while maintaining high hardness (Vickers hardness 11.97-12.74 GPa) and high density (6.12-6.19 g / cm³). 3 At the same time, it achieves low-pollution protection for the slurry being ground, and its overall performance is significantly better than that of products produced by traditional homogenization mixing processes. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1:

[0023] Step 1: Weigh 2145g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand for aging for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0024] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 820g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0025] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 12g of citric acid monohydrate and 300g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 28g of trisodium citrate dihydrate and 500g of deionized water, and continue stirring at 30℃ for 40min.

[0026] Step 4: Weigh 404g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 7g of oxalic acid dihydrate and 700g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 120g of ammonium bicarbonate and 1200g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 120 minutes, and 25% ammonia water was added simultaneously to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 1202g, oxalic acid dihydrate aqueous solution was added over 20 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia water was used to maintain the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia water were added over 40 minutes to raise the pH of the system to 8.5. The slurry was then aged at 40°C for 120 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0027] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 450℃ at 2℃ / min, hold it at that temperature for 3h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0028] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 980g of cerium-stabilized zirconia gradient powder obtained in step 5, 20g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 300r / min for 8h; after wet milling, the powder D50 of the slurry detected by a laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0029] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature to 180℃ and the outlet temperature to 90℃, to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, and spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, with a rolling pelletizing speed of 35r / min and a rolling time of 40min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0030] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, raise the temperature to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then raise the temperature to 1250℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 1380℃ at 2℃ / min and hold for 2 hours, and finally lower the temperature to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0031] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0032] Example 2:

[0033] Step 1: Weigh 2171g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand for aging for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0034] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 830g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0035] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 10g of citric acid monohydrate and 300g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 24g of trisodium citrate dihydrate and 500g of deionized water, and continue stirring at 30℃ for 40min.

[0036] Step 4: Weigh 378g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 5g of oxalic acid dihydrate and 600g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 110g of ammonium bicarbonate and 1100g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 100 minutes, and at the same time, 25% ammonia water was added to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 989g, oxalic acid dihydrate aqueous solution was added over 15 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia water was used to control the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia water were added over 40 minutes to raise the pH of the system to 8.3. The slurry was then aged at 40°C for 100 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0037] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 420℃ at 2℃ / min, hold it at that temperature for 4h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0038] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 980g of cerium-stabilized zirconia gradient powder obtained in step 5, 20g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 300r / min for 8h; after wet milling, the powder D50 of the slurry detected by a laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0039] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature at 175℃ and the outlet temperature at 88℃, to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, and spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, with a rolling pelletizing speed of 35r / min and a rolling time of 40min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0040] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, raise the temperature to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then raise the temperature to 1240℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 1360℃ at 2℃ / min and hold for 2 hours, and finally lower the temperature to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0041] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0042] Example 3:

[0043] Step 1: Weigh 2118g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand for aging for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0044] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 810g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0045] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 15g of citric acid monohydrate and 300g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 32g of trisodium citrate dihydrate and 500g of deionized water, and continue stirring at 30℃ for 40min.

[0046] Step 4: Weigh 429g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 9g of oxalic acid dihydrate and 800g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 130g of ammonium bicarbonate and 1300g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 140 minutes, while 25% ammonia was added to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 1420g, oxalic acid dihydrate aqueous solution was added over 25 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia was used to maintain the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia were added over 40 minutes to raise the pH of the system to 8.7. The slurry was then aged at 40°C for 150 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0047] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 500℃ at 2℃ / min, hold it at that temperature for 2h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0048] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 980g of cerium-stabilized zirconia gradient powder obtained in step 5, 20g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 300r / min for 8h; after wet milling, the powder D50 of the slurry detected by a laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0049] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature at 185℃ and the outlet temperature at 92℃ to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, the rolling pelletizing speed is 35r / min, and the rolling time is 40min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0050] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, raise the temperature to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then raise the temperature to 1260℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 1400℃ at 2℃ / min and hold for 2 hours, and finally lower the temperature to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0051] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0052] Example 4:

[0053] Step 1: Weigh 2132g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand for aging for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0054] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 815g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0055] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 12g of citric acid monohydrate and 300g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 28g of trisodium citrate dihydrate and 500g of deionized water, and continue stirring at 30℃ for 40min.

[0056] Step 4: Weigh 404g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 7g of oxalic acid dihydrate and 700g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 120g of ammonium bicarbonate and 1200g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 120 minutes, and 25% ammonia water was added simultaneously to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 1202g, oxalic acid dihydrate aqueous solution was added over 20 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia water was used to maintain the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia water were added over 40 minutes to raise the pH of the system to 8.5. The slurry was then aged at 40°C for 120 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0057] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 450℃ at 2℃ / min, hold it at that temperature for 3h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0058] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 975g of cerium-stabilized zirconia gradient powder obtained in step 5, 25g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 300r / min for 8h; after wet milling, the powder D50 of the slurry detected by laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0059] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature to 180℃ and the outlet temperature to 90℃, to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, and spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, with a rolling pelletizing speed of 35r / min and a rolling time of 45min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0060] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, raise the temperature to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then raise the temperature to 1250℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 1380℃ at 2℃ / min and hold for 2 hours, and finally lower the temperature to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0061] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0062] Example 5:

[0063] Step 1: Weigh 2158g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand and age for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0064] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 825g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0065] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 12g of citric acid monohydrate and 300g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 28g of trisodium citrate dihydrate and 500g of deionized water, and continue stirring at 30℃ for 40min.

[0066] Step 4: Weigh 404g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 7g of oxalic acid dihydrate and 700g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 120g of ammonium bicarbonate and 1200g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 120 minutes, and 25% ammonia water was added simultaneously to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 1102 g, oxalic acid dihydrate aqueous solution was added over 20 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia water was used to maintain the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia water were added over 40 minutes to raise the pH of the system to 8.5. The slurry was then aged at 40°C for 120 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0067] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 470℃ at 2℃ / min, hold it at that temperature for 3h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0068] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 985g of cerium-stabilized zirconia gradient powder obtained in step 5, 15g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 300r / min for 8h; after wet milling, the powder D50 of the slurry detected by laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0069] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature to 180℃ and the outlet temperature to 90℃, to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, and spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, with a rolling pelletizing speed of 35r / min and a rolling time of 40min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0070] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, heat to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then heat to 1250℃ at 3℃ / min and hold for 1 hour, then heat to 1390℃ at 2℃ / min and hold for 2 hours, and finally cool to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0071] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0072] Example 6:

[0073] Step 1: Weigh 2145g of zirconium oxychloride octahydrate and 5000g of deionized water, and stir at 300r / min at 25℃ until completely dissolved to obtain a zirconium oxychloride aqueous solution; add 2000g of deionized water and 400g of 25% ammonia water to the reactor, and stir at 400r / min at 25℃; continuously add the zirconium oxychloride aqueous solution to the reactor over 70min, and simultaneously continuously add 25% ammonia water over 70min to maintain the pH of the system at 8 to 9; after the addition is completed, continue stirring for 60min, and then let it stand for aging for 120min to obtain a cerium-free zirconium oxide hydrate precipitate slurry.

[0074] Step 2: Filter the zirconia hydrated precipitate slurry obtained in Step 1, wash it four times with 24000g of deionized water, adding 6000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 50μS / cm and the chloride ion content is not higher than 50mg / L. Take 20g of the washed wet filter cake sample, dry it at 110℃ for 2h, place it in an air atmosphere furnace, keep it at 900℃ for 1h, cool and weigh it, and calculate the zirconia equivalent in the wet filter cake based on the mass of the ignition residue; then weigh the wet filter cake containing the equivalent of 820g of zirconia, add 5000g of deionized water, and stir at 600r / min for 30min at 30℃ to obtain the zirconia hydrated particle dispersion slurry.

[0075] Step 3: Add an aqueous solution of citric acid monohydrate prepared by 13g of citric acid monohydrate and 320g of deionized water to the zirconia hydrate particle dispersion slurry obtained in Step 2, and stir at 600r / min for 20min at 30℃; then add an aqueous solution of trisodium citrate dihydrate prepared by 30g of trisodium citrate dihydrate and 520g of deionized water, and continue stirring at 30℃ for 40min.

[0076] Step 4: Weigh 404g of cerium nitrate hexahydrate and 1600g of deionized water to prepare an aqueous solution of cerium nitrate hexahydrate; weigh 8g of oxalic acid dihydrate and 750g of deionized water to prepare an aqueous solution of oxalic acid dihydrate; weigh 125g of ammonium bicarbonate and 1250g of deionized water to prepare an aqueous solution of ammonium bicarbonate. After stirring the slurry obtained in step 3 at 30°C for 40 minutes, cerium nitrate hexahydrate aqueous solution was added dropwise. The cerium nitrate hexahydrate aqueous solution was added dropwise over 130 minutes, and 25% ammonia water was added simultaneously to maintain the pH of the system at 6 to 7. When the cumulative amount of cerium nitrate hexahydrate aqueous solution added reached 1303g, oxalic acid dihydrate aqueous solution was added over 20 minutes. During the addition of oxalic acid dihydrate aqueous solution, 25% ammonia water was used to maintain the pH of the system at 6 to 7. After all the cerium nitrate hexahydrate aqueous solution was added dropwise, stirring was continued for 30 minutes. Then, ammonium bicarbonate aqueous solution and 25% ammonia water were added over 40 minutes to raise the pH of the system to 8.6. The slurry was then aged at 42°C for 130 minutes to obtain a zirconia hydrated composite precursor slurry with cerium outer edge deposition.

[0077] Step 5: Filter the zirconia hydrated composite precursor slurry obtained in Step 4, wash it three times with 12000g of deionized water, adding 4000g of deionized water each time and stirring for 10min before filtering; wash until the conductivity of the filtrate is not higher than 150μS / cm and the nitrate content is not higher than 100mg / L. Dry the washed filter cake at 110℃ for 12h, crush it and pass it through an 18-mesh sieve to make the particle size of the crushed powder less than 1mm; then place the powder in an air atmosphere furnace, heat it to 480℃ at 2℃ / min, hold it at that temperature for 2.5h, and then cool it to room temperature with the furnace to obtain cerium-stabilized zirconia gradient powder.

[0078] Step 6: Weigh 10g of polyvinyl alcohol 1788 type and 240g of deionized water, stir at 90℃ for 60min to obtain a polyvinyl alcohol aqueous solution, cool to 30℃ and set aside; weigh 980g of cerium-stabilized zirconia gradient powder obtained in Step 5, 20g of alumina, 410g of deionized water and the above polyvinyl alcohol aqueous solution, add to a ball mill jar, then add 3000g of cerium-stabilized zirconia grinding balls with a particle size of 3mm, wet mill at 320r / min for 7h; after wet milling, the powder D50 of the slurry detected by a laser particle size analyzer is not greater than 500nm, then filter through a 200-mesh sieve, and vacuum degas at 80℃ for 30min.

[0079] Step 7: Spray dry the slurry obtained in Step 6, controlling the inlet temperature to 180℃ and the outlet temperature to 90℃, to obtain granulated powder with a moisture content of no more than 1%; weigh 8g of polyvinyl alcohol and 142g of deionized water, stir at 90℃ for 60min, and cool to 30℃ to obtain a polyvinyl alcohol aqueous solution; weigh 1000g of granulated powder, and spray the above polyvinyl alcohol aqueous solution at 10g / min during the rolling pelletizing process, with a rolling pelletizing speed of 38r / min and a rolling time of 40min; sieve green pellets with a particle size of 700μm to 900μm, and dry at 80℃ for 6h.

[0080] Step 8: Place the green pellets obtained in Step 7 into an air atmosphere furnace, raise the temperature to 600℃ at 1℃ / min and hold for 2 hours to complete the debinding, then raise the temperature to 1250℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 1370℃ at 2℃ / min and hold for 2 hours, and finally lower the temperature to 600℃ at 3℃ / min and cool with the furnace to obtain sintered ceramic beads.

[0081] Step 9: Add the sintered ceramic beads obtained in Step 8 to 3000g of deionized water, roll and shape them at 60r / min for 60min, sieve ceramic beads with a particle size of 600μm to 800μm, wash them with 3000g of deionized water and dry them at 120℃ for 4h to obtain zirconium-cerium-aluminum composite ceramic beads.

[0082] Comparative Example 1: The difference from Example 1 lies in the timing of the addition of the cerium nitrate hexahydrate aqueous solution. In Example 1, the entire cerium nitrate hexahydrate aqueous solution prepared from 404g of cerium nitrate hexahydrate and 1600g of deionized water in step 4 is added beforehand to the zirconium oxychloride aqueous solution in step 1 of Example 1, and added to the reactor along with the zirconium oxychloride aqueous solution within 70 minutes. In Example 1, the cerium nitrate hexahydrate aqueous solution is no longer added dropwise in step 4, but the oxalic acid dihydrate aqueous solution is still added between the corresponding 72 and 92 minutes. The ammonium bicarbonate aqueous solution, 25% ammonia solution, and aging conditions remain unchanged. All other conditions are the same as in Example 1.

[0083] Comparative Example 2: The difference from Example 1 is that in step 3 of Example 1, the aqueous solution of citric acid monohydrate prepared by 12g of citric acid monohydrate and 300g of deionized water is not added, and 312g of deionized water is added at the same time point. The other conditions are the same as in Example 1.

[0084] Comparative Example 3: The difference from Example 1 is that in step 3 of Example 1, the aqueous solution of trisodium citrate dihydrate prepared by 28g of trisodium citrate dihydrate and 500g of deionized water is not added, and 528g of deionized water is added at the same time point. The other conditions are the same as in Example 1.

[0085] Comparative Example 4: The difference from Example 1 is that the timing of adding the oxalic acid dihydrate aqueous solution in step 4 of Example 1 is different; the oxalic acid dihydrate aqueous solution is added at the same time as the cerium nitrate hexahydrate aqueous solution begins to be added dropwise, and the oxalic acid dihydrate aqueous solution is still added within 20 minutes. The other conditions are the same as in Example 1.

[0086] Comparative Example 5: The difference from Example 1 is that in step 4 of Example 1, the aqueous solution of oxalic acid dihydrate prepared by 7g of oxalic acid dihydrate and 700g of deionized water is not added, and 707g of deionized water is added at the same time point. The other conditions are the same as in Example 1.

[0087] Comparative Example 6: The difference from Example 1 is that in Step 4 of Example 1, the pH of the system was controlled at 8 to 9 during the addition of the cerium nitrate hexahydrate aqueous solution and the addition of the oxalic acid dihydrate aqueous solution, instead of 6 to 7. All other conditions were the same as in Example 1.

[0088] Comparative Example 7: The difference from Example 1 is that in step 5 of Example 1, the washed filter cake was dried at 110°C for 12 hours, crushed, and passed through an 18-mesh sieve. It was then used directly as the powder in step 6 without pre-calcination at 450°C. The remaining conditions were the same as in Example 1.

[0089] Comparative Example 8: The difference from Example 1 is that the timing of the addition of alumina is different; the 20g of alumina used in step 6 of Example 1 is added immediately after the formation of the zirconia hydrate particle dispersion slurry obtained in step 2 of Example 1, and is processed together with steps 3 and 4; in step 6 of Example 1, alumina is not added again. The other conditions are the same as in Example 1.

[0090] Comparative Example 9: The difference from Example 1 is that in step 6 of Example 1, 20g of alumina is not added, and the amount of cerium-stabilized zirconium oxide gradient powder obtained in step 5 is adjusted from 980g to 1000g, so that the total amount of main solids added in step 6 remains 1000g. The other conditions are the same as in Example 1.

[0091] Performance testing: Zirconium-cerium-aluminum composite ceramic beads with a particle size of 600-800 μm, obtained in Examples 1-6 and Comparative Examples 1-9, were used as ceramic bead test samples. These were ultrasonically cleaned with deionized water for 10 min, followed by ultrasonic cleaning with anhydrous ethanol for 5 min, dried at 120℃ for 2 h, and then cooled to room temperature in a desiccator. Strip samples for fracture toughness testing were prepared from granulated powder obtained by spray drying the slurry from step 6 of the same examples or comparative examples. The granulated powder was dry-pressed into 45 mm × 6 mm × 5 mm blanks under 80 MPa pressure, sintered according to the debinding and sintering regime of step 8 of the corresponding examples or comparative examples, and then processed into 36 mm × 4 mm × 3 mm test strips. Five strips were prepared for each sample. Powder samples for characterizing the cerium outer edge deposition distribution were taken from the powder obtained in step 5 of each example or comparative example. After being dispersed in anhydrous ethanol for 5 min, the powder was dropped onto a carbon film copper grid and dried at 60℃ for 30 min.

[0092] Characterization of Cerium Edge Deposition Distribution and Gradient Layer Thickness: The cerium edge deposition distribution was characterized according to the general rules of transmission electron microscopy analysis (JY / T 0581-2020) and scanning electron microscopy analysis (JY / T 0584-2020). Powder samples obtained in step 5 of each sample were observed using a 200kV transmission electron microscope in bright field. Energy dispersive spectroscopy (EDS) line scanning was performed from one outer edge of a single particle through the center to the other outer edge, with a scanning step size of 2nm. Thirty particles were randomly tested for each sample. The region from 0nm to 80nm from the particle's outer edge was defined as the outer edge region, and the region representing 30% of the particle's diameter was defined as the center region. The Ce / Zr atomic ratios in the outer edge and center regions were calculated, and the Ce / Zr ratio of the cerium edge to the center was also calculated. For sintered ceramic bead samples, the ceramic beads were cold-mounted and then progressively ground to 2000 mesh, followed by polishing with 0.05μm alumina polishing slurry. The continuity of cerium distribution in the cross-section was observed using a 15kV scanning electron microscope and energy dispersive spectroscopy (EDS). The Ce / Zr ratio at the outer edge / center and the gradient layer thickness were used as the results, where the gradient layer thickness was the thickness of the continuous outer edge region where the Ce / Zr atomic ratio was more than 10% higher than the average value of the central region.

[0093] Phase composition and monoclinic phase increment test after hydrothermal aging: Phase composition was tested according to GB / T 30904-2014 X-ray diffraction method for crystal structure analysis of inorganic chemical products, and hydrothermal aging was performed according to JC / T 2015-2010 method for determining the aging performance of tetragonal zirconia ceramics. 5.000g of each sample ceramic bead was ground in an agate mortar and passed through a 200-mesh sieve to obtain X-ray diffraction test powder. A Cu target Kα ray was used with a tube voltage of 40kV, a tube current of 40mA, a scanning range of 2θ from 20° to 80°, a step size of 0.02°, and a scanning speed of 4° / min. 20.000g of the same sample ceramic bead was placed in a hydrothermal aging vessel and treated in saturated steam at 134℃ for 24h. After removal, it was washed with deionized water, dried at 120℃ for 2h, ground again, and passed through a 200-mesh sieve for X-ray diffraction testing. The tetragonal phase content after sintering and the monoclinic phase increment after aging were calculated based on the characteristic diffraction peak areas of tetragonal and monoclinic zirconia.

[0094] Bulk density, apparent porosity, and Vickers hardness testing: Bulk density and apparent porosity were tested according to GB / T 25995-2010, Test Method for Density and Apparent Porosity of Fine Ceramics. For each sample, 20.000 g of dried ceramic beads were weighed, boiled in deionized water for 2 hours, cooled to 25°C, and then the saturated mass, suspended mass, and dried mass were measured. Bulk density and apparent porosity were calculated. Each sample was tested in triplicate, and the average value was taken. Vickers hardness was tested according to GB / T 16534-2009, Test Method for Room Temperature Hardness of Fine Ceramics. For each sample, 20 ceramic beads were randomly selected, cold-mounted with epoxy resin, ground to 2000 mesh, and then polished to a mirror finish with 0.05 μm alumina polishing liquid. A load of 9.807 N was applied to the Vickers hardness tester and held for 15 seconds. Ten effective indentations were taken from each sample, with the distance between indentations not less than three times the diagonal length of the indentation. The Vickers hardness was calculated and converted to GPa.

[0095] Fracture toughness test: Fracture toughness was tested according to the single-sided pre-cracked beam method of GB / T 23806-2025 Test Method for Fracture Toughness of Fine Ceramics. Five sintered strips of 36mm×4mm×3mm were prepared from the same batch of granulated powder for each sample. A single-sided pre-crack was prepared in the middle of the 4mm wide face of the strip, with the crack depth controlled at 1.6mm and the span at 30mm. A three-point bending fixture was used for loading at a loading rate of 0.5mm / min. The fracture load was recorded and the fracture toughness KIC was calculated.

[0096] Abrasion rate and slurry contamination increment test of stirred mill: Abrasion tests of small-sized ceramic beads were conducted using the stirred mill method according to JC / T 2906-2025, "Test Method for Abrasion of Small-Sized Spherical Ceramic Grinding Media," and mass loss was calculated according to the weighing and result expression principles of the planetary mill method in JC / T 2519-2019, "Test Method for Abrasion of Ceramic Grinding Media." For each sample, 500.000 g of dried ceramic beads were weighed and added to a 0.6 L ceramic-lined stirred mill, followed by 500.000 g of deionized water and 200.000 g of lithium iron phosphate powder. The stirring disc linear velocity was set to 8 m / s, and the circulating cooling water temperature was set to 25℃. Grinding was performed continuously for 6 hours. After grinding, the ceramic beads were rinsed with 500.000 g of deionized water, sieved, and recovered. The beads were dried at 120℃ for 2 hours, cooled to room temperature, and weighed. The abrasion rate of the stirred mill was calculated based on the mass loss of the ceramic beads. Take 10.000g of the ground slurry, digest it with nitric acid, hydrochloric acid and hydrofluoric acid, and then make up to 100mL. Determine the contents of zirconium, cerium and aluminum by inductively coupled plasma atomic emission spectrometry according to GB / T 30902-2014 Determination of Impurity Elements in Inorganic Chemical Products. Use the slurry obtained without ceramic beads, containing only deionized water and lithium iron phosphate powder, and stirred under the same conditions for 6h as a blank sample, and calculate the total increase of zirconium, cerium and aluminum.

[0097] As shown in Table 1, in Comparative Example 1, the cerium nitrate hexahydrate aqueous solution was pre-incorporated into the zirconium oxychloride aqueous solution for co-precipitation. The Ce / Zr ratio of the outer edge / center of cerium was only 1.08, and the gradient layer thickness was only 10 nm. This indicates that the process is difficult to form a continuous cerium outer edge enrichment structure. After sintering, the tetragonal phase content was 96.3%, and the monoclinic phase increment after aging was 2.4%. The wear rate of the stirred mill and the total increment of zirconium, cerium and aluminum elements reached 10.86 mg / (kg·h) and 39.6 mg / kg, respectively.

[0098] After removing citric acid monohydrate or trisodium citrate dihydrate from Comparative Examples 2 and 3, the Ce / Zr ratio at the outer edge / center of cerium, fracture toughness, and wear resistance were all lower than those in Example 1, indicating that acidic pre-activation and buffer complexation treatment have a positive effect on the directional adsorption of cerium ions at the outer edge of zirconia hydrated particles.

[0099] In Comparative Example 4, oxalic acid dihydrate was added at the beginning of the dropwise addition of cerium nitrate hexahydrate aqueous solution, which easily caused cerium to precipitate prematurely in the liquid phase, resulting in a decrease in the Ce / Zr ratio of the outer edge / center of cerium to 1.28 and an increase in the wear rate of the stirred mill to 12.36 mg / (kg·h). In Comparative Example 5, after the removal of oxalic acid dihydrate, although there was still some cerium adsorption on the outer edge, the locking effect was insufficient, and the wear rate was still 9.42 mg / (kg·h). In Comparative Example 6, after increasing the pH to 8 to 9 during the deposition stage, all performance characteristics further declined, indicating that the short-term addition of oxalic acid dihydrate in the later stage and the deposition environment of pH 6 to 7 play an important role in reducing the precipitation of free cerium and local agglomeration.

[0100] Comparative Example 7 did not undergo low-temperature pre-calcination, and the powder still had a certain cerium outer edge distribution. However, the fixation effect during subsequent wet milling and sintering was insufficient. Its apparent porosity, monoclinic phase increment after aging, wear rate, and elemental contamination increment were all significantly higher than those of Example 1. In Comparative Example 8, after adding alumina to the deposition system in advance, the Ce / Zr ratio of the outer edge to the center of cerium decreased to 1.47, indicating that the premature presence of alumina may interfere with the directional deposition of cerium on the outer edge of zirconia hydrated particles. Although Comparative Example 9 retained a high Ce / Zr ratio of the outer edge to the center of cerium, its Vickers hardness, fracture toughness, and wear performance were still lower than those of Example 1 because no alumina was added.

[0101] Compared with the comparative examples, Examples 1-6 all exhibited higher Ce / Zr ratios at the cerium periphery / center, lower monoclinic phase increments after aging, higher fracture toughness, and lower wear rates during stirring and lower total increments of zirconium, cerium, and aluminum elements. Among them, Example 3 achieved a Ce / Zr ratio of 2.13 at the cerium periphery / center, a gradient layer thickness of 68 nm, a tetragonal phase content of 98.6% after sintering, a monoclinic phase increment of only 0.3% after aging, and a fracture toughness of 10.84 MPa·m. 1 / 2The wear rate of the stirred mill and the total increase in zirconium, cerium and aluminum elements were reduced to 4.68 mg / (kg·h) and 16.8 mg / kg, respectively.

[0102] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A process for the preparation of zirconia-ceria-alumina composite ceramic beads, characterized in that, Includes the following steps: S1. Using zirconium oxychloride octahydrate as the zirconium source and ammonia water with a mass fraction of 25% as the precipitant, a cerium-free zirconium oxide hydrate precipitate slurry is obtained by precipitation under the condition of pH 8-9. After washing, water is added according to the zirconium oxide equivalent to disperse, and a zirconium oxide hydrate particle dispersion slurry containing 810-830 parts by weight of zirconium oxide is obtained. S2. Pretreatment is carried out by sequentially adding 10-15 parts by weight of citric acid monohydrate and 24-32 parts by weight of trisodium citrate dihydrate to the zirconium oxide hydrate particle dispersion slurry to obtain a pretreated slurry. S3. Add an aqueous solution of cerium nitrate hexahydrate containing 378-429 parts by weight to the pretreated slurry, and maintain the pH of the system at 6-7 with 25% by weight ammonia water during the addition of the aqueous solution of cerium nitrate hexahydrate; when the cumulative amount of the aqueous solution of cerium nitrate hexahydrate added reaches 50%-70% of its total amount, start adding an aqueous solution of oxalate dihydrate containing 5-9 parts by weight within 15-25 minutes, and maintain the pH of the system at 6-7 with 25% by weight ammonia water during the addition of the aqueous solution of oxalate dihydrate; after the addition of the aqueous solution of cerium nitrate hexahydrate is completed, add an aqueous solution of ammonium bicarbonate and 25% by weight ammonia water to raise the pH of the system to 8.3-8.7, and age at 40-42℃ for 100-150 minutes to obtain a cerium-zirconia hydrated composite precursor slurry; S4. The cerium-containing zirconium oxide hydrated composite precursor slurry is filtered, washed, dried, crushed, and pre-calcined at 420-500℃ for 2-4 hours to obtain cerium-containing zirconium oxide pre-calcined powder. S5. After obtaining the cerium-containing zirconium oxide pre-calcined powder, alumina is mixed with the cerium-containing zirconium oxide pre-calcined powder and wet-milled to obtain zirconium-cerium-aluminum wet milling slurry; wherein, based on a total weight of 1000 parts by weight of the cerium-containing zirconium oxide pre-calcined powder and alumina, the alumina is 15-25 parts by weight. S6. Spray dry the zirconium-cerium-aluminum wet grinding slurry to obtain granulated powder, roll the granulated powder into balls, dry, remove the binder, sinter and self-grind to obtain zirconium-cerium-aluminum composite ceramic beads.

2. The process for preparing zirconia ceria alumina composite ceramic beads according to claim 1, characterized in that, In step S1, the washed wet filter cake sample is taken, dried at 110℃ for 2 hours, placed in an air atmosphere furnace, kept at 900℃ for 1 hour, cooled and weighed, and the zirconium oxide equivalent in the wet filter cake is calculated based on the mass of the ignition residue.

3. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S2, the citric acid monohydrate is added in the form of an aqueous solution of citric acid monohydrate, which is prepared by 10-15 parts by weight of citric acid monohydrate and 300-320 parts by weight of deionized water; the trisodium citrate dihydrate is added in the form of an aqueous solution of trisodium citrate dihydrate, which is prepared by 24-32 parts by weight of trisodium citrate dihydrate and 500-520 parts by weight of deionized water.

4. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S2, after adding the aqueous solution of citric acid monohydrate, the mixture is stirred at 30°C for 20 min; then the aqueous solution of trisodium citrate dihydrate is added, and the mixture is stirred at 30°C for another 40 min.

5. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S3, the cerium nitrate hexahydrate aqueous solution is prepared by 378-429 parts by weight of cerium nitrate hexahydrate and 1600 parts by weight of deionized water; the oxalic acid dihydrate aqueous solution is prepared by 5-9 parts by weight of oxalic acid dihydrate and 600-800 parts by weight of deionized water; and the ammonium bicarbonate aqueous solution is prepared by 110-130 parts by weight of ammonium bicarbonate and 1100-1300 parts by weight of deionized water.

6. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S4, the washed filter cake is dried at 110℃ for 12 hours, crushed, and passed through an 18-mesh sieve to make the particle size of the crushed powder less than 1 mm.

7. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S5, the slurry is wet-milled at 300-320 r / min for 7-8 hours. After wet milling, the powder D50 of the slurry detected by the laser particle size analyzer is no greater than 500 nm. Then, it is filtered through a 200-mesh sieve and vacuum degassed at 80℃ for 30 minutes.

8. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S6, 8 parts by weight of polyvinyl alcohol and 142 parts by weight of deionized water are weighed and stirred at 90°C for 60 min. After cooling to 30°C, a polyvinyl alcohol aqueous solution is obtained. 1000 parts by weight of the granulation powder are weighed and sprayed with the polyvinyl alcohol aqueous solution at 10 parts by weight / min during the granulation process. The granulation speed is 35-38 r / min and the granulation time is 40-45 min. Green pellets with a particle size of 700-900 μm are sieved and dried at 80°C for 6 h.

9. The preparation process of the zirconium-cerium-aluminum composite ceramic beads according to claim 1, characterized in that, In step S6, the dried green pellets are placed in an air atmosphere furnace, heated to 600°C at 1°C / min and held for 2 hours to remove the binder, then heated to 1240-1260°C at 3°C / min and held for 1 hour, then heated to 1360-1400°C at 2°C / min and held for 2 hours, and finally cooled to 600°C at 3°C / min and cooled with the furnace to obtain sintered ceramic beads; The sintered ceramic beads were added to deionized water and rolled and shaped at 60 r / min for 60 min. Ceramic beads with a particle size of 600-800 μm were sieved, washed with deionized water, and dried at 120℃ for 4 h to obtain the zirconium-cerium-aluminum composite ceramic beads.

10. A zirconium-cerium-aluminum composite ceramic bead, characterized in that, The zirconium-cerium-aluminum composite ceramic beads are obtained by the preparation process described in any one of claims 1-9.

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