A nano-reinforced high-toughness zirconia ceramic microsphere and its preparation method

Abstract

This invention discloses a nano-reinforced high-toughness zirconia ceramic microsphere and its preparation method, belonging to the field of microsphere preparation technology. It addresses the technical problems in existing zirconia ceramic microspheres where the nanoparticles easily agglomerate, resulting in poor sphericity, low density, and insufficient fracture toughness. The specific steps include: placing dimethyl silicone oil in a reaction vessel and stirring; heating the reaction vessel to 85-95℃; adding a dispersant and a nanocomposite slurry; maintaining the temperature and stirring for 30-60 minutes; and then post-processing to obtain microsphere green bodies. This invention utilizes cerium-yttrium co-doped nanocrystalline powder, leveraging the steric hindrance effect of a self-made comb-shaped polycarboxylic acid ether to achieve high solids content dispersion, combined with reverse-phase suspension polymerization to construct a three-dimensional network to lock in high-sphericity green bodies, and finally densifying through stepwise sintering to obtain highly dense and high-toughness zirconia ceramic microspheres.

Description

Technical Field

[0001] This invention relates to the field of microbead preparation technology, specifically to a nano-reinforced high-toughness zirconia ceramic microbead and its preparation method. Background Technology

[0002] Zirconia ceramic microspheres, as a high-performance grinding media, have been widely used in the ultrafine grinding and dispersion of electronic ceramics, magnetic materials, fine chemicals, and new energy battery materials due to their high hardness, high wear resistance, and chemical stability. As downstream industries demand powder fineness down to the nanoscale and the energy density of sand mills continues to increase, grinding media are facing more demanding working conditions. Modern ultrafine grinding processes require zirconia microspheres to not only have extremely small particle sizes, but also to have a density close to the theoretical density, extremely high sphericity, and excellent impact and breakage resistance to ensure that they maintain their morphological integrity during high-speed shearing and collision and reduce wear on grinding equipment.

[0003] Currently, common industrial methods for preparing zirconia microspheres include rolling molding, spray granulation, and titration. In terms of material systems, yttrium oxide is often used as a single stabilizer to prepare tetragonal polycrystalline zirconia. However, the above molding processes have significant limitations in preparing microspheres with small particle sizes. Rolling molding is difficult to guarantee the uniformity and sphericity of microsphere size, and elliptical or conjoined particles are prone to appear. Powders prepared by spray granulation often have hollow structures, resulting in insufficient density after sintering. Traditional titration mainly relies on physical gelation, resulting in low green strength and large drying shrinkage. In addition, in the slurry preparation stage, conventional polyelectrolyte dispersants rely solely on electrostatic repulsion, which is difficult to effectively overcome the huge specific surface energy of nanoparticles at high solid content, leading to a sharp increase in slurry viscosity and severe powder agglomeration, which in turn limits the improvement of green density.

[0004] In existing technologies, if the soft agglomerates of nano-zirconia powder in an aqueous system are not fully deagglomerated, pores and coarse grain regions will form inside the sintered body. This not only reduces the overall density of the material but also becomes a source of stress concentration. Furthermore, the molding method that relies on solvent evaporation and drying will generate capillary pressure and density gradient inside the green body, leading to microcracks or shape collapse during sintering and making it impossible to obtain excellent sphericity. At the same time, the zirconia lattice, which is stable under single yttrium oxide, is prone to low-temperature aging under the heat accumulation and shear force generated by long-term high-speed grinding. Under extreme impact, its fracture toughness is insufficient, causing the microspheres to easily break or peel off, affecting grinding efficiency and product purity.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-reinforced high-toughness zirconia ceramic microsphere and its preparation method, which solves the technical problems in the prior art where the nanoparticles are prone to agglomeration, resulting in poor sphericity, low density, and the need for further improvement in fracture toughness of the finished product.

[0007] The objective of this invention can be achieved through the following technical solution: a method for preparing nano-reinforced high-toughness zirconia ceramic microspheres, comprising the following steps:

[0008] S1. Place the premixed liquid and comb-shaped polycarboxylic acid ether in a reaction vessel and stir. Add ammonia water to adjust the pH to 9-10. Add nanocrystalline powder and stir at room temperature for 25-35 minutes. Add initiator and stir at room temperature for 10-15 minutes. Pass through a 300-mesh sieve to obtain nanocomposite slurry.

[0009] S2. Place dimethyl silicone oil in a reaction vessel and stir. Heat the reaction vessel to 85-95℃, add dispersant and nanocomposite slurry, keep warm and stir for 30-60 minutes, and then process to obtain microbead embryos.

[0010] S3. Add the microsphere green body to a muffle furnace and heat it to 300-400℃ at a rate of 1℃ / min, then to 550-650℃ at a rate of 0.5℃ / min, and then to 1400-1500℃ at a rate of 3℃ / min. Hold the temperature for 1-2 hours and then process to obtain high-toughness zirconia ceramic microspheres.

[0011] Furthermore, in step S1, the ratio of the premixed solution, comb-shaped polycarboxylic acid ether, nanocrystalline powder, and initiator is 90-110 mL: 1-2 g: 150-180 g: 0.3-0.5 g. The premixed solution is composed of acrylamide, N,N'-methylenebisacrylamide, and deionized water in a ratio of 18-22 g: 0.8-1.2 g: 80-100 mL. The initiator is one or more of ammonium persulfate, potassium persulfate, and azobisisobutylamidine hydrochloride. The ammonia concentration is 25-28 wt%.

[0012] Further, in step S2, the weight ratio of the dimethyl silicone oil, dispersant, and nanocomposite slurry is 350-450:3-5:80-100, and the dispersant is one or both of Span-80 and Span-60. The post-processing steps include: after the reaction is completed, the mixture is filtered while hot, the filter cake is washed 2-4 times with petroleum ether, transferred to an oven at a temperature of 60-80℃, and dried for 2-4 hours to obtain microbead embryos.

[0013] Furthermore, in step S3, the post-processing steps include: after sintering, after the product cools to room temperature, vibrating sieve is performed using a standard sieve of 0.1-0.2 mm. The sieved product is transferred to a ball mill jar, deionized water is added to make the ball-to-material ratio 1:1-1.5, and the product is self-polished for 1-2 hours. It is then washed 2-4 times with deionized water and transferred to an oven at a temperature of 50-60℃ to dry, thereby obtaining high-toughness zirconia ceramic microspheres.

[0014] Furthermore, the nanocrystalline powder is prepared by the following steps:

[0015] A1. Place zirconium oxychloride octahydrate, cerium nitrate hexahydrate, yttrium nitrate and deionized water in a reaction vessel under nitrogen atmosphere protection, and stir at room temperature for 20-30 min to obtain a mixed salt solution;

[0016] A2. Place ammonia water in a reaction vessel and stir. Add a mixed salt solution and stir at room temperature for 25-35 minutes. Then, perform post-treatment to obtain the nanocrystalline powder precursor.

[0017] A3. Add the nanocrystalline powder precursor to a muffle furnace, heat it to 200-300℃ at a rate of 2℃ / min, then heat it to 600-700℃ at a rate of 5℃ / min, hold the reaction at this temperature for 0.5-1h, and then process it to obtain nanocrystalline powder.

[0018] Furthermore, in step A1, the ratio of zirconium oxychloride octahydrate, cerium nitrate hexahydrate, yttrium nitrate, and deionized water is 40-60g:6-8g:1-2g:80-100mL.

[0019] Further, in step A2, the volume ratio of ammonia water to mixed salt solution is 60-80:120-140, the concentration of ammonia water is 25-28 wt%, and the post-processing steps include: after the reaction is completed, filtration is performed, the filter cake is washed with deionized water until no white precipitate is produced when silver nitrate solution is added dropwise to the filtrate, then washed with ethanol 1-3 times, transferred to an oven at a temperature of 50-60℃, and dried to constant weight to obtain the nanocrystalline powder precursor.

[0020] Furthermore, in step A3, the post-processing step includes: after the reaction is completed, wait for the reaction system to cool to room temperature, take out the product, grind it, and pass it through a 300-mesh sieve to obtain nanocrystalline powder.

[0021] Furthermore, the preparation method of the comb-shaped polycarboxylic acid ether is as follows: acrylic acid, methoxy polyethylene glycol methacrylate and deionized water are placed in a reaction vessel under nitrogen atmosphere and stirred. The reaction vessel is heated to 70-80℃, ammonium persulfate is added, and the mixture is kept at this temperature and stirred for 4-5 hours. The comb-shaped polycarboxylic acid ether is then obtained through post-treatment.

[0022] Furthermore, the ratio of acrylic acid, methoxy polyethylene glycol methacrylate, deionized water, and ammonium persulfate is 2-4g:6-8g:40-60mL:0.1-0.15g. The post-treatment steps include: after the reaction is completed, the reaction system is cooled to room temperature, the pH of the reaction solution is adjusted to 6.5-7.5 using 25-28wt% ammonia water, the reaction solution is slowly added dropwise to excess anhydrous ethanol for precipitation, the mixture is allowed to stand and separate into layers, then filtered, the filter cake is washed 2-3 times with anhydrous ethanol, transferred to a vacuum drying oven at 40-50℃ and dried to constant weight, and then ground through a 200-mesh sieve to obtain comb-shaped polycarboxylic acid ether.

[0023] The present invention also proposes a nano-reinforced high-toughness zirconia ceramic microsphere, which is prepared by the above-mentioned preparation method of a nano-reinforced high-toughness zirconia ceramic microsphere.

[0024] The present invention has the following beneficial effects:

[0025] 1. This invention constructs a homogeneous cation system of zirconium, cerium, and yttrium and combines it with a simultaneous co-precipitation process induced by ammonia water. This ensures uniform mixing of dopants at the atomic scale and effectively avoids lattice defects caused by component segregation. Driven by step-by-step heating and calcination, cerium and yttrium ions are fully dissolved in the zirconium oxide lattice to form a highly stable tetragonal phase structure. This endows zirconium oxide ceramic microspheres with excellent phase transformation toughening properties. That is, when subjected to external impact or grinding, the metastable tetragonal phase rapidly transforms into a monoclinic phase. Accompanied by volume expansion, a compressive stress field is generated, which can effectively inhibit the initiation and propagation of microcracks and significantly improve the wear resistance and fracture resistance of the grinding media under high-speed impact environment.

[0026] 2. This invention uses comb-shaped polycarboxylic acid ether as a dispersant. This dispersant utilizes the strong anchoring effect of the main chain carboxyl groups on the surface of nanocrystalline powder, as well as the strong steric hindrance effect constructed by the extension of polyethylene glycol side chains into the aqueous phase, in conjunction with the electrostatic repulsion mechanism, to significantly reduce the van der Waals attraction potential energy between particles. This interface regulation mechanism not only greatly improves the dispersion uniformity of nanoparticles in the aqueous system, but also effectively inhibits agglomeration, enabling the slurry to achieve extremely high solid content loading while maintaining low viscosity. The high-solid-content homogeneous slurry provides a dense packing foundation for subsequent molding processes, minimizing porosity defects and density gradients inside the green body, and improving the density and excellent volume stability of zirconia ceramic microspheres.

[0027] 3. In addition, under the action of interfacial tension and shear force of the continuous phase of hot silicone oil, the highly dispersed slurry is divided into micron-sized spherical droplets, which then trigger monomer polymerization to construct a three-dimensional cross-linked polymer network, thereby encapsulating and solidifying the nanoparticles in situ. This imparts extremely high sphericity and mechanical strength to the green embryo, avoiding deformation and collapse during the drying process. Furthermore, the stepped heating sintering process gently removes the organic framework while utilizing the high sintering activity of the nanocrystal powder to drive grain boundary migration and material diffusion, eliminating debinding cracks and promoting pore closure. This significantly reduces the self-wear rate of the grinding media and extends its service life. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The dimethyl silicone oil used in this invention was purchased from Anpu (Langfang) Environmental Protection Technology Co., Ltd., and its density is 0.965-0.975 g / cm³. 3 The product name is AP-6170 methyl silicone oil;

[0030] The polyvinyl alcohol used in this invention was purchased from Xiamen Minghuiyang Chemical Co., Ltd., with an effective ingredient content of 97%, brand name Minghuiyang Chemical, and molecular weight of 44.05.

[0031] Example 1

[0032] This embodiment provides a method for preparing comb-shaped polycarboxylic acid ethers, including the following steps:

[0033] Weigh 20g of acrylic acid, 60g of methoxy polyethylene glycol methacrylate, and 400mL of deionized water and place them in a nitrogen-protected reactor. Stir the reactor and heat it to 70℃. Add 1g of ammonium persulfate and keep it at this temperature for 4 hours. After the reaction is complete, let the reaction system cool to room temperature. Adjust the pH of the reaction solution to 6.5 using 25wt% ammonia. Slowly add excess anhydrous ethanol to the reaction solution to precipitate the product. After standing and separating the layers, filter the product. Wash the filter cake twice with anhydrous ethanol and transfer it to a vacuum drying oven at 40℃ to dry to constant weight. Grind the product through a 200-mesh sieve to obtain comb-shaped polycarboxylic acid ether.

[0034] Under nitrogen protection and heating conditions, ammonium persulfate decomposes to generate free radicals, which initiate addition polymerization and chain growth reactions of the vinyl double bonds in acrylic acid and methoxy polyethylene glycol methacrylate molecules, constructing a comb-shaped amphiphilic copolymer with a carbon-carbon chain rich in carboxyl groups as the main chain and polyethylene glycol segments as side chains. Subsequently, through an acid-base neutralization reaction, the carboxyl groups of the main chain are converted into sodium carboxylate salts using ammonia water to obtain comb-shaped polycarboxylate sodium salt.

[0035] The graft copolymerization of acrylic acid and methoxy polyethylene glycol methacrylate macromonomers creates a unique comb-like molecular structure. By utilizing the strong anchoring effect of the main chain carboxyl groups on the surface of zirconia powder and the steric hindrance effect of the side chains, the viscosity of high solids slurry is effectively reduced and nanoparticle agglomeration is prevented. In particular, the use of ammonia water for neutralization and adjustment enables the complete ionization of functional groups to enhance dispersion ability, thereby improving the density and final toughness of zirconia microspheres.

[0036] Example 2

[0037] This embodiment provides a method for preparing comb-shaped polycarboxylic acid ethers, including the following steps:

[0038] Weigh out 30g of acrylic acid, 70g of methoxy polyethylene glycol methacrylate, and 500mL of deionized water and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and heat it to 75°C. Add 1.2g of ammonium persulfate and keep it at this temperature for 4.5h. After the reaction is complete, let the reaction system cool to room temperature. Adjust the pH of the reaction solution to 7 using 26.5wt% ammonia water. Slowly add excess anhydrous ethanol to the reaction solution to precipitate the product. After standing and separating the layers, filter the product. Wash the filter cake three times with anhydrous ethanol and transfer it to a vacuum drying oven at 45°C to dry to constant weight. Grind the product through a 200-mesh sieve to obtain comb-shaped polycarboxylic acid ether.

[0039] Example 3

[0040] This embodiment provides a method for preparing comb-shaped polycarboxylic acid ethers, including the following steps:

[0041] Weigh 40g of acrylic acid, 80g of methoxy polyethylene glycol methacrylate, and 600mL of deionized water and place them in a nitrogen-protected reactor. Stir the reactor and heat it to 80℃. Add 1.5g of ammonium persulfate and keep it heated and stirred for 5 hours. After the reaction is complete, let the reaction system cool to room temperature. Adjust the pH of the reaction solution to 7.5 using 28wt% ammonia water. Slowly add excess anhydrous ethanol to the reaction solution to precipitate the product. After standing and separating the layers, filter the product. Wash the filter cake three times with anhydrous ethanol and transfer it to a vacuum drying oven at 50℃ to dry to constant weight. Grind the product through a 200-mesh sieve to obtain comb-shaped polycarboxylic acid ether.

[0042] Example 4

[0043] This embodiment provides a method for preparing nanocrystalline powder, including the following steps:

[0044] Step ①: Prepare a mixed salt solution

[0045] Weigh out 400g of zirconium oxychloride octahydrate, 60g of cerium nitrate hexahydrate, 10g of yttrium nitrate and 800mL of deionized water and place them in a reaction vessel under nitrogen atmosphere protection. Stir at room temperature for 20min to obtain a mixed salt solution.

[0046] Step 2: Preparation of nanocrystalline powder precursor

[0047] Weigh 600 mL of 25 wt% ammonia water and place it in a reaction vessel and stir. Add 1200 mL of mixed salt solution and stir at room temperature for 25 min. After the reaction is complete, filter the mixture and wash the filter cake with deionized water until no white precipitate is produced when silver nitrate solution is added to the filtrate. Then wash the mixture once with ethanol and transfer it to an oven at 50 ℃ to dry to constant weight to obtain the nanocrystalline powder precursor.

[0048] Step ③: Preparation of nanocrystalline powder

[0049] The nanocrystalline powder precursor was added to a muffle furnace and heated to 200°C at a rate of 2°C / min, and then heated to 600°C at a rate of 5°C / min. The temperature was maintained for 0.5 h. After the reaction was completed, the reaction system was allowed to cool to room temperature. The product was then taken out, ground, and passed through a 300-mesh sieve to obtain nanocrystalline powder.

[0050] A homogeneous metal cation system was constructed by utilizing the solubility characteristics of zirconium oxychloride, cerium nitrate, and yttrium nitrate in water. Subsequently, hydroxide ions were provided by ammonia water to induce simultaneous hydrolysis and co-precipitation reactions of Zr4+, Ce3+, and Y3+ ions, generating a mixed metal hydroxide precursor. Chloride and nitrate impurities were removed by washing. The dried precursor underwent dehydration condensation and thermal decomposition reactions during stepped heating calcination, transforming the amorphous hydroxide into oxide. At the same time, cerium and yttrium ions diffused in situ at high temperature and dissolved in the zirconium oxide lattice, completing the structural transformation from the amorphous precursor to stable crystalline nanoparticles.

[0051] A homogeneous cation system was constructed to achieve atomic-level mixing of zirconium, cerium, and yttrium, avoiding microscopic component segregation from the source to ensure the consistency of material properties. The ammonia-induced simultaneous co-precipitation and deep washing process completely removed impurity ions while locking in a precise stoichiometric ratio, eliminating the hidden danger of porosity formation during sintering and ensuring the density of zirconia ceramic microspheres. Stepwise heating and calcination, based on precise control of grain growth and maintenance of high sintering activity at the nanoscale of powder, drove the full solid solution of cerium and yttrium ions to form a stable tetragonal phase lattice, endowing zirconia ceramic microspheres with excellent phase transformation toughening mechanism and impact and wear resistance.

[0052] Example 5

[0053] This embodiment provides a method for preparing nanocrystalline powder, including the following steps:

[0054] Step ①: Prepare a mixed salt solution

[0055] Weigh out 500g of zirconium oxychloride octahydrate, 70g of cerium nitrate hexahydrate, 15g of yttrium nitrate and 900mL of deionized water and place them in a reaction vessel under nitrogen atmosphere protection. Stir at room temperature for 25min to obtain a mixed salt solution.

[0056] Step 2: Preparation of nanocrystalline powder precursor

[0057] Weigh 700 mL of 26 wt% ammonia water and place it in a reaction vessel and stir. Add 1300 mL of mixed salt solution and stir at room temperature for 30 min. After the reaction is complete, filter the mixture and wash the filter cake with deionized water until no white precipitate is produced when silver nitrate solution is added to the filtrate. Then wash the mixture twice with ethanol and transfer it to an oven at 55 ℃ to dry to constant weight to obtain the nanocrystalline powder precursor.

[0058] Step ③: Preparation of nanocrystalline powder

[0059] The nanocrystalline powder precursor was added to a muffle furnace and heated to 250°C at a rate of 2°C / min, and then to 650°C at a rate of 5°C / min. The temperature was maintained for 1 hour. After the reaction was completed, the reaction system was allowed to cool to room temperature. The product was then removed, ground, and passed through a 300-mesh sieve to obtain nanocrystalline powder.

[0060] Example 6

[0061] This embodiment provides a method for preparing nanocrystalline powder, including the following steps:

[0062] Step ①: Prepare a mixed salt solution

[0063] Weigh out 600g of zirconium oxychloride octahydrate, 80g of cerium nitrate hexahydrate, 20g of yttrium nitrate and 1000mL of deionized water and place them in a reaction vessel under nitrogen atmosphere protection. Stir at room temperature for 30min to obtain a mixed salt solution.

[0064] Step 2: Preparation of nanocrystalline powder precursor

[0065] Weigh 800 mL of 28 wt% ammonia water and place it in a reaction vessel and stir. Add 1400 mL of mixed salt solution and stir at room temperature for 35 min. After the reaction is complete, filter the mixture and wash the filter cake with deionized water until no white precipitate is produced when silver nitrate solution is added to the filtrate. Then wash the mixture three times with ethanol and transfer it to an oven at 60 ℃ to dry to constant weight to obtain the nanocrystalline powder precursor.

[0066] Step ③: Preparation of nanocrystalline powder

[0067] The nanocrystalline powder precursor was added to a muffle furnace and heated to 300°C at a rate of 2°C / min, and then to 700°C at a rate of 5°C / min. The temperature was maintained for 1 hour. After the reaction was completed, the reaction system was allowed to cool to room temperature. The product was then taken out, ground, and passed through a 300-mesh sieve to obtain nanocrystalline powder.

[0068] Example 7

[0069] This embodiment provides a method for preparing nano-reinforced high-toughness zirconia ceramic microspheres, including the following steps:

[0070] Step (1) Preparation of nanocomposite slurry

[0071] Acrylamide, N,N'-methylenebisacrylamide and deionized water were mixed evenly at a ratio of 180g:8g:800mL to obtain a premixed solution for later use.

[0072] Weigh 900 mL of the premixed solution and 10 g of the comb-shaped polycarboxylic acid ether prepared in Example 1 and place them in a reaction vessel and stir. Add 25 wt% ammonia water to adjust the pH to 9, add 1500 g of the nanocrystalline powder prepared in Example 4, stir at room temperature for 25 min, add 3 g of potassium persulfate, stir at room temperature for 10 min, and pass through a 300-mesh sieve to obtain the nanocomposite slurry.

[0073] Step 2: Preparation of microbead embryos

[0074] Weigh 3500g of dimethyl silicone oil and place it in a reaction vessel and stir. Heat the reaction vessel to 85℃, add 30g of Span-80 and 800g of nanocomposite slurry, keep warm and stir for 30min. After the reaction is complete, filter while hot, wash the filter cake twice with ethanol, transfer it to an oven at 60℃ and dry for 2h to obtain microbead embryos.

[0075] Step 3: Preparation of high-toughness zirconia ceramic microspheres

[0076] The microsphere green was added to a muffle furnace and heated to 300℃ at a rate of 1℃ / min, then to 550℃ at a rate of 0.5℃ / min, and finally to 1400℃ at a rate of 3℃ / min. The temperature was maintained for 1 hour. After sintering, the product was allowed to cool to room temperature and then vibrated and sieved using a 0.1mm standard sieve. The sieved product was transferred to a ball mill jar, and deionized water was added to make the ball-to-material ratio 1:1. The product was self-polished for 1 hour, washed twice with deionized water, and then dried in an oven at 50℃ to obtain high-toughness zirconia ceramic microspheres.

[0077] By utilizing the electrostatic repulsion and steric hindrance effect of comb-shaped polycarboxylic acid ethers, zirconia nanoparticles are uniformly dispersed in an aqueous system containing acrylamide monomers and N,N'-methylenebisacrylamide. Subsequently, in a continuous phase of hot silicone oil, the aqueous slurry is dispersed into spherical microdroplets by interfacial tension and stirring shear force. Under heating conditions, potassium persulfate is used to initiate free radical polymerization and cross-linking reactions of the monomers, constructing a three-dimensional polymer network structure to in-situ encapsulate and solidify the nanoparticles, forming spherical microbeads with a certain strength. Finally, through stepped heating sintering, the organic polymer skeleton is first removed by low-temperature oxidation decomposition, and then the ceramic grains are driven to undergo solid-phase diffusion, mass transfer, and shrinkage densification at high temperature, completing the transformation from an organic-inorganic composite to dense ceramic microbeads.

[0078] The homogeneous dispersion achieved by comb-shaped polycarboxylic acid ether effectively inhibits the agglomeration of nanoparticles, ensuring the structural uniformity of the ceramic green body and the stability of the high-solids slurry at the microscopic level. The reverse suspension and in-situ polymerization and curing process utilizes interfacial tension and three-dimensional network structure to precisely lock the high sphericity and uniform particle size of the microspheres, and endow the green body with the mechanical strength required to maintain its geometric shape. The step-by-step sintering process gently removes organic components and avoids debinding cracks, while driving dense grain packing and microstructure optimization, thereby improving the density, compressive strength and toughening properties of zirconia ceramic microspheres.

[0079] Example 8

[0080] This embodiment provides a method for preparing nano-reinforced high-toughness zirconia ceramic microspheres, including the following steps:

[0081] Step (1) Preparation of nanocomposite slurry

[0082] Acrylamide, N,N'-methylenebisacrylamide and deionized water were mixed evenly at a ratio of 200g:10g:900mL to obtain a premixed solution for later use.

[0083] Weigh 1000 mL of the premixed solution and 15 g of the comb-shaped polycarboxylic acid ether prepared in Example 2 and place them in a reaction vessel and stir. Add 26.5 wt% ammonia water to adjust the pH to 9.5, add 1650 g of the nanocrystalline powder prepared in Example 5, stir at room temperature for 30 min, add 4 g of potassium persulfate, stir at room temperature for 13 min, and pass through a 300-mesh sieve to obtain a nanocomposite slurry.

[0084] Step 2: Preparation of microbead embryos

[0085] Weigh 4000g of dimethyl silicone oil and place it in a reaction vessel and stir. Heat the reaction vessel to 90℃, add 40g of Span-80 and 900g of nanocomposite slurry, keep warm and stir for 45min. After the reaction is complete, filter while hot, wash the filter cake three times with ethanol, transfer it to an oven at 70℃ and dry for 3h to obtain microbead embryos.

[0086] Step 3: Preparation of high-toughness zirconia ceramic microspheres

[0087] The microsphere green was added to a muffle furnace and heated to 400℃ at a rate of 1℃ / min, then to 650℃ at a rate of 0.5℃ / min, and finally to 1500℃ at a rate of 3℃ / min. The temperature was maintained for 2 hours. After sintering, the product was allowed to cool to room temperature and then vibrated and sieved using a 0.15mm standard sieve. The sieved product was transferred to a ball mill jar, and deionized water was added to make the ball-to-material ratio 1:1.2. The product was self-polished for 1.5 hours, washed three times with deionized water, and then dried in an oven at 55℃ to obtain high-toughness zirconia ceramic microspheres.

[0088] Example 9

[0089] This embodiment provides a method for preparing nano-reinforced high-toughness zirconia ceramic microspheres, including the following steps:

[0090] Step (1) Preparation of nanocomposite slurry

[0091] Acrylamide, N,N'-methylenebisacrylamide and deionized water were mixed evenly at a ratio of 220g:12g:1000mL to obtain a premixed solution for later use.

[0092] Weigh 1100 mL of the premixed solution and 20 g of the comb-shaped polycarboxylic acid ether prepared in Example 3 and place them in a reaction vessel and stir. Add 28 wt% ammonia water to adjust the pH to 10, add 1800 g of the nanocrystalline powder prepared in Example 6, stir at room temperature for 35 min, add 5 g of potassium persulfate, stir at room temperature for 15 min, and pass through a 300-mesh sieve to obtain a nanocomposite slurry.

[0093] Step 2: Preparation of microbead embryos

[0094] Weigh 4500g of dimethyl silicone oil and place it in a reaction vessel and stir. Heat the reaction vessel to 95℃, add 50g of Span-80 and 1000g of nanocomposite slurry, keep warm and stir for 60min. After the reaction is complete, filter while hot, wash the filter cake 4 times with ethanol, transfer it to an oven at 80℃ and dry for 4h to obtain microbead embryos.

[0095] Step 3: Preparation of high-toughness zirconia ceramic microspheres

[0096] The microsphere green was added to a muffle furnace and heated to 400℃ at a rate of 1℃ / min, then to 650℃ at a rate of 0.5℃ / min, and finally to 1500℃ at a rate of 3℃ / min. The temperature was maintained for 2 hours. After sintering, the product was allowed to cool to room temperature and then vibrated and sieved using a 0.2mm standard sieve. The sieved product was transferred to a ball mill jar, and deionized water was added to make the ball-to-material ratio 1:1.5. The product was self-polished for 2 hours, washed 4 times with deionized water, and then dried in an oven at 60℃ to obtain high-toughness zirconia ceramic microspheres.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 9 is that yttrium nitrate was omitted in step ① when preparing the mixed salt solution.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 9 is that, in step (1) when preparing the nanocomposite slurry, an equal amount of 5 wt% polyvinyl alcohol aqueous solution is used to replace the premixed liquid.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 9 is that the comb-shaped polycarboxylic acid ether was omitted when preparing the nanocomposite slurry in step (1).

[0103] Performance testing:

[0104] The sphericity, bulk density, Vickers hardness and self-wear rate of the zirconia ceramic microspheres prepared in Examples 7-9 and Comparative Examples 1-3 were tested in accordance with the standard JC / T 2136-2012 "Microcrystalline Zirconia Abrasive Media Balls".

[0105] The fracture toughness of the zirconia ceramic microspheres prepared in Examples 7-9 and Comparative Examples 1-3 was tested according to the standard GB / T 44537-2024 "Test Method for Fracture Toughness of Fine Ceramics at Room Temperature - Surface Crack Bending Beam (SCF) Method". The specific data are shown in Table 1.

[0106] Table 1 - Performance Test Data for Each Sample

[0107]

[0108] Data Analysis:

[0109] Comparative analysis of the data in the above table revealed that the fracture toughness of the high-toughness zirconia ceramic microspheres prepared in this invention is 9.5 MPa·m. 1 / 2 The sphericity is 97.2%, and the bulk density is 6.04 g·cm³. -3 It has a Vickers hardness of 13.1 GPa and a self-wear rate of 0.02 g·(kg·h).-1 All data points are better than the comparative data;

[0110] Comparative analysis of the data from Example 9 and Comparative Example 1 revealed that the fracture toughness, sphericity, bulk density, and Vickers hardness of Comparative Example 1 decreased significantly, while the self-wear rate increased significantly. This indicates that the omission of yttrium nitrate during the preparation of nanocrystalline powder led to a decrease in the stability of tetragonal zirconium oxide, a weakening of the phase transformation toughening mechanism, a sharp drop in fracture toughness, and an increase in the self-wear rate.

[0111] Comparative analysis of the data from Example 9 and Comparative Example 2 revealed that the fracture toughness, sphericity, bulk density, and Vickers hardness of Comparative Example 2 decreased significantly, while the self-wear rate increased significantly. This indicates that polyvinyl alcohol lacks cross-linking polymerization ability and cannot form a three-dimensional network to lock the spherical shape, resulting in decreased sphericity. At the same time, insufficient adhesion leads to decreased density and a significantly increased self-wear rate.

[0112] Comparative analysis of the data from Example 9 and Comparative Example 2 revealed that the fracture toughness, sphericity, bulk density, and Vickers hardness of Comparative Example 2 decreased significantly, while the self-wear rate increased significantly. This indicates that the lack of dispersant during the preparation of the nanocomposite slurry led to the agglomeration of nanoparticles, resulting in a decrease in bulk density and Vickers hardness and an increase in self-wear rate.

[0113] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of making nano-reinforced high toughness zirconia ceramic microbeads, characterized in that, Includes the following steps: S1. Place the premixed liquid and comb-shaped polycarboxylic acid ether in a reaction vessel and stir. Add ammonia water to adjust the pH to 9-10. Add nanocrystalline powder and stir at room temperature for 25-35 minutes. Add initiator and stir at room temperature for 10-15 minutes. Pass through a 300-mesh sieve to obtain nanocomposite slurry. S2. Place dimethyl silicone oil in a reaction vessel and stir. Heat the reaction vessel to 85-95℃, add dispersant and nanocomposite slurry, keep warm and stir for 30-60 minutes, and then process to obtain microbead embryos. S3. Add the microsphere green body to a muffle furnace and heat it to 300-400℃ at a rate of 1℃ / min, then to 550-650℃ at a rate of 0.5℃ / min, and then to 1400-1500℃ at a rate of 3℃ / min. Hold the temperature for 1-2 hours and then process to obtain high-toughness zirconia ceramic microspheres.

2. A method of preparing nano-reinforced high toughness zirconia ceramic microbeads according to claim 1, characterized in that, In step S1, the ratio of the premixed solution, comb-shaped polycarboxylic acid ether, nanocrystalline powder, and initiator is 90-110 mL: 1-2 g: 150-180 g: 0.3-0.5 g. The premixed solution is composed of acrylamide, N,N'-methylenebisacrylamide, and deionized water in a ratio of 18-22 g: 0.8-1.2 g: 80-100 mL. The initiator is one or more of ammonium persulfate, potassium persulfate, and azobisisobutylamidine hydrochloride. The ammonia concentration is 25-28 wt%.

3. A method of preparing nano-reinforced high toughness zirconia ceramic microbeads according to claim 1, characterized in that, In step S2, the weight ratio of the dimethyl silicone oil, dispersant, and nanocomposite slurry is 350-450:3-5:80-100, and the dispersant is one or both of Span-80 and Span-60.

4. A method of preparing nano-reinforced high toughness zirconia ceramic microbeads according to claim 1, characterized in that, The nanocrystalline powder is prepared by the following steps: A1. Place zirconium oxychloride octahydrate, cerium nitrate hexahydrate, yttrium nitrate and deionized water in a reaction vessel under nitrogen atmosphere protection, and stir at room temperature for 20-30 min to obtain a mixed salt solution; A2. Place ammonia water in a reaction vessel and stir. Add a mixed salt solution and stir at room temperature for 25-35 minutes. Then, perform post-treatment to obtain the nanocrystalline powder precursor. A3. Add the nanocrystalline powder precursor to a muffle furnace, heat it to 200-300℃ at a rate of 2℃ / min, then heat it to 600-700℃ at a rate of 5℃ / min, hold the reaction at this temperature for 0.5-1h, and then process it to obtain nanocrystalline powder.

5. A method of preparing nano-reinforced high toughness zirconia ceramic microbeads according to claim 4, characterized in that, In step A1, the ratio of zirconium oxychloride octahydrate, cerium nitrate hexahydrate, yttrium nitrate, and deionized water is 40-60g:6-8g:1-2g:80-100mL; in step A2, the volume ratio of ammonia water and mixed salt solution is 60-80:120-140, and the concentration of ammonia water is 25-28wt%.

6. A method of preparing nano-reinforced high toughness zirconia ceramic microbeads according to claim 1, characterized in that, The method for preparing the comb-shaped polycarboxylate ether is as follows: acrylic acid, methoxy polyethylene glycol methacrylate and deionized water are placed in a reaction vessel under nitrogen atmosphere and stirred. The reaction vessel is heated to 70-80℃, ammonium persulfate is added, and the mixture is kept at this temperature and stirred for 4-5 hours. The comb-shaped polycarboxylate ether is then obtained through post-treatment.

7. A method of making nano-reinforced high toughness zirconia ceramic microbeads according to claim 6, characterized in that, The ratio of acrylic acid, methoxy polyethylene glycol methacrylate, deionized water and ammonium persulfate is 2-4g:6-8g:40-60mL:0.1-0.15g.

8. A nano-reinforced, high-toughness zirconia ceramic-based microsphere, characterized in that, The nano-reinforced high-toughness zirconia ceramic microspheres are prepared using the preparation method of nano-reinforced high-toughness zirconia ceramic microspheres as described in any one of claims 1-7.

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