Method for preparing high-strength and high-toughness zta ceramic by using multi-grade powder

Abstract

This application discloses a method for preparing high-strength and high-toughness ZTA ceramics from multi-graded powder, relating to the field of structural ceramic preparation technology. The method includes: preparing raw materials by mixing four-particle-graded ZTA-based powder, yttrium oxide-cerium dioxide composite sintering aid, DMAA gel system, dispersant, initiator, and deionized water in parts by mass; followed by powder pretreatment, gel slurry preparation, casting and curing, degreasing treatment, and three-stage pressureless sintering to obtain the finished ZTA ceramic product. This application achieves close particle packing through a four-particle-graded structure based on the Dingle model, achieves uniform molding using a low-toxicity DMAA gel system, and controls grain growth through a three-stage sintering process, ultimately obtaining high-strength and high-toughness ZTA ceramics suitable for waste incineration power generation, biomedicine, semiconductor packaging, and other fields.

Description

Technical Field

[0001] This invention relates to the field of structural ceramics preparation technology, and in particular to a method for preparing high-strength and high-toughness ZTA ceramics from multi-graded powder. Background Technology

[0002] ZTA (zirconia-toughened alumina) ceramics combine the high hardness and wear resistance of alumina with the high toughness of zirconia. Through synergistic mechanisms such as phase transformation toughening and microcrack toughening, they have broad application prospects in fields such as biomedicine, semiconductors, and high-end machinery. Currently, the demand for green and environmentally friendly products in the field of special refractory materials is increasingly urgent. Green special refractory ceramics have become an important development direction for the industry, requiring excellent performance while achieving environmentally friendly production processes, resource and energy conservation, and harmless use.

[0003] However, traditional ZTA ceramic preparation faces the following technical bottlenecks: First, insufficient bulk density of raw material powder leads to low green body density and porosity defects after sintering, affecting the final mechanical properties. Existing particle size distributions mostly employ bimodal or trimodal systems, and optimization based on Furnas, Horsfield, and other models offers limited improvement in bulk density (typically ≤4.1%), making it difficult to achieve high-density sintering. Second, the molding system suffers from high toxicity or poor green body uniformity. While traditional acrylamide (AM) gel systems can achieve near-net-shape molding, AM is neurotoxic, and the curing process is easily inhibited by oxygen, leading to surface crusting and a surface defect rate as high as 15%-20%. This not only increases protection costs but also affects the final mechanical properties.

[0004] To address the aforementioned issues, existing technologies struggle to simultaneously achieve high density, excellent mechanical properties, and environmental friendliness. Therefore, how to prepare ZTA ceramics that meet both high performance and environmental requirements has become a pressing technical challenge in this field. Summary of the Invention

[0005] This application provides a method for preparing high-strength and high-toughness ZTA ceramics using multi-graded powder, solving the technical problems in the prior art where insufficient bulk density of raw material powder leads to low green body density, high toxicity of the molding system, or poor green body uniformity. It achieves a bulk density ≥ 4.5 g / cm³. 3 Flexural strength ≥1000MPa, fracture toughness ≥8.5MPa·m 1 / 2 While achieving high-performance ZTA ceramics, it also meets the environmental protection requirements of green special refractory ceramics.

[0006] This application provides a method for preparing high-strength and high-toughness ZTA ceramics from multi-grade powder, including the following steps:

[0007] S1. Raw material preparation: The raw materials include four-particle-grade ZTA-based powder, sintering aid, DMAA gel system, dispersant, initiator and deionized water; The sintering aid is a composite system of yttrium oxide and cerium dioxide; the DMAA gel system includes the gel monomer N,N-dimethylacrylamide and the crosslinking agent N,N'-methylenebisacrylamide. S2. Pretreatment of four-particle-graded powder: The four-particle-graded ZTA-based powder is mixed with sintering aid, ball milling media are added for ball milling, dried and sieved to obtain graded mixed powder; S3. DMAA gel slurry preparation: DMAA monomer, MBAM crosslinking agent and dispersant are dissolved in deionized water to obtain a premix. The pH of the premix is ​​adjusted to 9-10, and then graded mixed powder is added. The mixture is ball-milled to obtain a ceramic slurry. After adding an initiator, the mixture is stirred evenly to obtain a stable slurry. S4. Injection molding and gel curing: The stable slurry is injected into the mold, cured at a constant temperature, and ZTA ceramic green body is obtained after demolding; S5. Degreasing treatment: The green blank is heated to 550-650℃ in air atmosphere and kept at this temperature to remove organic components; S6. Three-stage pressureless sintering: The degreased green body is sintered in three stages under a protective atmosphere. First, the temperature is increased to 1200℃ at 10℃ / min and held for 1 hour. Then, the temperature is increased to 1500℃ at 5℃ / min and held for 2 hours. Finally, the temperature is increased to 1600-1650℃ at 3℃ / min and held for 3 hours. After cooling, ZTA ceramic finished products are obtained.

[0008] Furthermore, the four-particle-grade ZTA-based powder includes particles A, B, C, and D. Particle A is α-alumina powder with a purity ≥99.9%, irregular morphology, D50 of 5-8 μm, and a mass percentage of 35%-45%; Particle B is α-alumina powder with a purity ≥99.9%, irregular flake shape, D50 of 1-3 μm, and a mass percentage of 25%-30%. The particles C are α-α-alumina powder with a purity ≥99.8%, irregular angular shape, D50 of 0.5-1μm, and a mass percentage of 15%-20%. The particles D are nano-yttrium oxide stabilized zirconium oxide powders with a purity ≥99.9%, irregular flocculent structure, D50 of 50-200nm, and a mass percentage of 10%-15%.

[0009] Furthermore, the characteristic feature is that, in step S1, the mass ratio of yttrium oxide to cerium dioxide in the sintering aid is 1:1 to 3:1.

[0010] Furthermore, in step S1, the dispersant is ammonium polycarboxylate salt, and the addition amount is 0.4%-0.8% of the ZTA-based powder mass; the gel monomer accounts for 5%-8% of the total mass of the slurry; the crosslinking agent is 3%-5% of the mass of DMAA; the initiator is ammonium persulfate, accounting for 0.2%-0.5% of the total mass of the slurry; and the amount of deionized water is used to adjust the solid phase volume fraction of the slurry to 55%-65%.

[0011] Furthermore, in step S2, the milling media is zirconia grinding balls, the solid-liquid mass ratio is 1:1, the milling time is 6-8 hours, the milling speed is 300-400 r / min, the drying temperature is 50-65℃, and the drying time is 2-3 hours.

[0012] Furthermore, in step S3, the slurry viscosity is ≤500 mPa·s.

[0013] Furthermore, in step S4, the curing temperature is 60-75℃, the curing time is 2-4 hours, the relative density of the green blank is ≥62%, and the bending strength of the green blank is ≥28MPa.

[0014] Furthermore, in step S5, the heating rate is 0.5-1.5℃ / min, and the holding time is 2 hours.

[0015] Furthermore, in step S6, the protective atmosphere is argon gas with a flow rate of 0.5-1 L / min.

[0016] Furthermore, the ZTA ceramic has a bulk density ≥ 4.5 g / cm³. 3 Flexural strength ≥1000MPa, fracture toughness ≥8.5MPa·m 1 / 2 Vickers hardness ≥17GPa.

[0017] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: By adopting a four-particle gradation system based on the Dingle model, and utilizing the complementary size and interlocking effect of irregular morphologies of particles A, B, C, and D, the bulk density of the green body is increased by 8%-12%, laying the foundation for the high density of the final ceramic and effectively solving the problem of insufficient bulk density in traditional bimodal or trimodal gradation systems.

[0018] By using a low-toxicity N,N-dimethylacrylamide gel system to replace the traditional acrylamide system, the neurotoxicity of acrylamide is avoided. The green body has a uniform microstructure with no obvious pore defects, and the biosafety is significantly improved. At the same time, the green body has a bending strength of ≥28MPa, providing a high-quality green body foundation for subsequent sintering.

[0019] By employing a three-stage pressureless sintering process, uniform diffusion of sintering aids is promoted at a low temperature of 1200℃, abnormal grain growth is suppressed at a medium temperature of 1500℃, and densification is achieved at a high temperature of 1600-1650℃. This synergistic effect of gradation and forming advantages results in a ceramic bulk density ≥4.5 g / cm³. 3 Flexural strength ≥1000MPa, fracture toughness ≥8.5MPa·m 1 / 2 Compared to traditional ZTA ceramics, its strength is increased by more than 30% and its toughness by more than 25%.

[0020] By using yttrium oxide-cerium dioxide chromium-free composite sintering aid to replace traditional chromium-containing aids, the risk of heavy metal pollution is completely eliminated while maintaining excellent mechanical properties. After the product is discarded, it can be treated as general industrial solid waste, which fully meets the standard requirements of green special refractory ceramics.

[0021] Furthermore, this application employs a pressureless sintering process, eliminating the need for high-pressure equipment and reducing production costs by 20%-30%. Additionally, gel casting can produce complex-shaped products, demonstrating strong process adaptability and making it suitable for high-end fields such as biomedicine, semiconductor packaging, and waste incineration power generation. Detailed Implementation

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] Example 1: This example provides a method for preparing high-strength and high-toughness ZTA ceramics using multi-graded powder. The specific steps are as follows: S1. Raw material preparation: The raw materials, by weight, are as follows: Four-particle-gradation ZTA-based powder: Particle A: α-alumina powder, purity ≥99.9%, irregular morphology, D50=6μm, dosage 40 parts; Particle B: α-alumina powder, purity ≥99.9%, irregular flakes, D50=2μm, dosage 28 parts; Particle C: α-alumina powder, purity ≥99.8%, irregular angular shape, D50=0.8μm, dosage is 18 parts; Particle D: Nano-yttrium oxide stabilized zirconia powder, purity ≥99.9%, irregular flocculent, D50=100nm, dosage 14 parts; Sintering aids: Y2O3: 0.8 parts, CeO2: 0.4 parts; DMAA gel system: Gel monomer: N,N-dimethylacrylamide (DMAA), accounting for 6% of the total mass of the slurry; Crosslinking agent: N,N'-methylenebisacrylamide (MBAM), accounting for 5% of the mass of DMAA; Dispersant: Ammonium polycarboxylate, used at 0.6% of the ZTA-based powder mass; Initiator: Ammonium persulfate (APS), accounting for 0.3% of the total slurry mass; Solvent: Deionized water, the amount used should be adjusted to adjust the volume fraction of the solid phase of the slurry to 60%.

[0024] S2. Pretreatment of four-particle-gradation powders: Weighed particles A, B, C, and D were mixed with Y₂O₃ and CeO₂ sintering aids, and zirconia grinding balls at a mass ratio of 1:1 to the powder were added as the ball milling medium. The mixture was ball-milled for 7 hours in a planetary ball mill using zirconia balls (ball-to-powder mass ratio of 3:1) at a speed of 350 r / min. The milled slurry was then rotary evaporated at 55℃ for 2.5 hours and finally passed through an 80-mesh sieve to obtain a uniformly dispersed graded mixed powder.

[0025] Preparation of S3.DMAA gel slurry: DMAA monomer, MBAM crosslinking agent, and polycarboxylate ammonium salt dispersant were dissolved in deionized water and dispersed in a high-speed disperser at 2000 r / min for 30 minutes to obtain a premix. The pH of the premix was adjusted to 9.5, and then the graded mixed powder obtained in step S2 was added. The mixture was ball-milled to obtain a ceramic slurry. The obtained slurry was placed in a vacuum degassing machine for 25 minutes with a vacuum degree ≤ -0.09 MPa. After adding APS initiator, the mixture was stirred evenly to obtain a stable ZTA ceramic slurry. The viscosity of the slurry was tested to be 420 mPa·s.

[0026] S4. Injection molding and gel curing: The slurry obtained in step S3 was injected into a mold pre-coated with a release agent and allowed to cure at a constant temperature of 70°C for 3 hours to form a three-dimensional network gel structure. After demolding, a ZTA ceramic green body was obtained. Testing showed that the green body had a relative density of 63.5% and a flexural strength of 29.5 MPa.

[0027] S5. Degreasing treatment: The green blank is placed in a muffle furnace and heated to 600°C at a heating rate of 1°C / min in an air atmosphere (oxygen volume fraction ≥21%), and held for 2 hours to completely remove the organic components in the green blank.

[0028] S6. Three-stage pressureless sintering: The degreased green body is placed in a sintering furnace, and argon gas is introduced throughout the process at a flow rate of 0.8 L / min. The sintering process is carried out in three stages: First stage (low temperature stage): Heat to 1200℃ at a rate of 10℃ / min and hold for 1 hour.

[0029] Second stage (medium temperature stage): Increase the temperature to 1500℃ at a rate of 5℃ / min and hold for 2 hours.

[0030] The third stage (high temperature stage): the temperature is increased to 1620℃ at a rate of 3℃ / min and held for 3 hours.

[0031] After the heat preservation is completed, the ceramic product is cooled to room temperature along with the furnace to obtain the ZTA ceramic product.

[0032] Example 2: The difference between this example and Example 1 is the raw material ratio and some process parameters. The remaining preparation steps and detection methods are the same as in Example 1.

[0033] 1. Adjustment of raw material ratio: The raw materials, by weight, are as follows: Four-particle-gradation ZTA-based powder: Particle A: α-alumina powder, D50=7μm, dosage adjusted to 38 parts; Particle B: α-alumina powder, D50=1.5μm, dosage adjusted to 30 parts; Particle C: α-alumina powder, D50=0.6μm, dosage adjusted to 19 parts; Particle D: Nano-yttrium oxide stabilized zirconia powder, D50=150nm, dosage adjusted to 13 parts; Sintering aids: The amount of Y2O3 is adjusted to 1.0 part and the amount of CeO2 is adjusted to 0.5 parts; DMAA gel system: DMAA, the gel monomer, accounts for 7% of the total mass of the slurry, and the crosslinking agent MBAM accounts for 5% of the mass of DMAA; The amount of dispersant (ammonium polycarboxylate) was adjusted to 0.7% of the ZTA-based powder mass; The initiator APS accounts for 0.4% of the total mass of the slurry; Slurry parameters: The volume fraction of the solid phase in the slurry was adjusted to 62% by the amount of deionized water used. The viscosity of the slurry was tested to be 480 mPa·s.

[0034] 2. Sintering process adjustment: The sintering temperature for the third stage (high temperature stage) is adjusted to 1630℃, and the holding time remains 3 hours.

[0035] Comparative Example 1: The difference between this example and Example 1 is that it uses a traditional bimodal particle size distribution system instead of a four-particle size distribution based on the Dingle model. Among them, the bimodal ZTA-based powders include: Particle A (coarse particles): α-Al2O3 powder, purity ≥99.9%, D50=6μm, dosage adjusted to 68 parts; Particle D (fine particles): Nano-yttrium oxide stabilized zirconia powder, purity ≥99.9%, D50=100nm, dosage adjusted to 32 parts.

[0036] Comparative Example 2: The difference between this example and Example 1 is that a traditional acrylamide (AM) gel system is used instead of a low-toxicity DMAA gel system. The gel monomer is acrylamide (AM), accounting for 6% of the total mass of the slurry.

[0037] Comparative Example 3: The difference between this example and Example 1 is that the traditional single-stage pressureless sintering process is used instead of the three-stage sintering process; the degreased green body is directly heated to 1620°C at a rate of 5°C / min, held for 3 hours, and then cooled with the furnace. Argon gas is introduced throughout the process for protection, with a flow rate of 0.8L / min.

[0038] Performance testing was conducted on the ZTA ceramics prepared in each embodiment, and the tests are as follows: Bulk density: Tested using Archimedes' displacement method according to GB / T 25995-2010 standard; Bending strength: Tested using a universal testing machine and the three-point bending method according to GB / T 6569-2006 standard. The specimen size was 3mm × 4mm × 36mm, the span was 30mm, and the loading rate was 0.5mm / min. Fracture toughness: The single-sided notched beam method (SENB) was used for testing according to GB / T 23806-2009 standard. The specimen size was 2.5mm × 5mm × 25mm, the notch depth was 2.5mm, and the span was 20mm. Vickers hardness: Tested using a Vickers hardness tester according to GB / T 16534-2009 standard. The load was 9.8 N, and the holding time was 15 s.

[0039] The test results are shown in Table 1 below: Table 1. Test Results of ZTA Ceramic Properties

[0040] Comparative Example 1 uses a traditional bimodal gradation and consists only of coarse-grained α-Al₂O₃ and nano-yttrium oxide-stabilized zirconium oxide powder, with a bulk density of only 4.27 g / cm³. 3The flexural strength is 760 MPa, and the fracture toughness is 6.1 MPa·m. 1 / 2 In contrast, Example 1 uses a four-particle gradation system containing particles A, B, C, and D, with a bulk density of 4.58 g / cm³. 3 The flexural strength was increased to 1050 MPa, and the fracture toughness was increased to 8.8 MPa·m. 1 / 2 .

[0041] Effect Analysis: Comparative Example 1, lacking intermediate-sized particles B and C, could not achieve close packing between particles, resulting in numerous pores in the green body. These pores could not be completely eliminated after sintering, becoming sources of defects within the material. In contrast, the four-particle gradation system designed in this invention based on the Dingle model achieves stepwise filling from the micrometer to the nanometer scale, increasing the green body's packing density and reducing porosity after sintering. This dense microstructure not only reduces stress concentration points but also increases the resistance to crack propagation, resulting in a significant increase of 38.2% in flexural strength and 44.3% in fracture toughness. This demonstrates that the four-particle gradation based on the Dingle model is the structural foundation for achieving high strength and high toughness in ZTA ceramics.

[0042] Comparative Example 2 used a traditional acrylamide (AM) gel system, and the ZTA ceramic prepared therefrom had a bulk density of 4.40 g / cm³. 3 The flexural strength is 885 MPa, and the fracture toughness is 7.3 MPa·m. 1 / 2 Example 1 uses a DMAA gel system, and its performance is significantly better than that of Comparative Example 2.

[0043] Effect Analysis: Traditional AM system slurries have high viscosity and poor fluidity, making it difficult to completely eliminate air bubbles during injection molding and easily leading to particle agglomeration, resulting in an uneven microstructure of the green body. This unevenness is inherited in the sintered body, forming local density fluctuations and microscopic defects. The DMAA gel system used in this invention has low slurry viscosity and good fluidity. Combined with vacuum degassing technology, it can obtain a green body with uniform particle distribution and no agglomeration. The uniform green body structure ensures synchronous shrinkage during sintering, avoiding internal stress caused by differences in local densification rates. Ultimately, the flexural strength and fracture toughness of Example 1 were improved by 18.6% and 20.5% respectively compared to Comparative Example 2. More importantly, the DMAA system is non-irritating to the skin and has high biocompatibility, achieving a green and environmentally friendly molding process while improving material performance.

[0044] Comparative Example 3 uses traditional single-stage sintering, directly heating the green body to 1620℃ and holding it there, resulting in a bulk density of 4.47 g / cm³. 3The flexural strength is 935 MPa, and the fracture toughness is 7.7 MPa·m. 1 / 2 Example 1 uses a three-stage sintering process, and its performance is superior to that of Comparative Example 3.

[0045] Effect Analysis: In single-stage sintering, the grain boundary migration rate and densification rate are difficult to synchronize during the heating process. Especially after entering the high-temperature zone, some grains grow abnormally, forming a bimodal grain distribution. The presence of large grains deteriorates the mechanical properties of the material. The three-stage sintering process adopted in this invention promotes uniform diffusion of sintering aids and activates grain boundaries at a low temperature stage of 1200℃; a long-term holding temperature of 1500℃ effectively inhibits abnormal grain growth and promotes full diffusion of grain boundaries and elimination of pores; finally, complete densification is achieved at a high temperature stage of 1620℃. This temperature control strategy results in uniform and fine grain size and a more optimized microstructure in Example 1. Compared with Comparative Example 3, the flexural strength and fracture toughness of Example 1 are improved by 12.3% and 14.3%, respectively, fully demonstrating that the three-stage sintering process is an important guarantee for fully utilizing the advantages of four-particle gradation and maximizing performance.

[0046] As shown in Examples 1 and 2, by adjusting the four-particle gradation ratio, the amount of additives, and the slurry and sintering parameters, a bulk density ≥4.5 g / cm³ can be obtained. 3 Flexural strength ≥1000MPa, fracture toughness ≥8.5MPa·m 1 / 2 And high-performance ZTA ceramics with a Vickers hardness ≥17.2 GPa.

[0047] This invention organically integrates key technical features of the four-particle gradation based on the Dingle model, low-toxicity DMAA gel casting, and a three-stage pressureless sintering process, resulting in a significant synergistic effect: the four-particle gradation constructs a high-density green body, laying the foundation for the final high density; the DMAA gel system ensures the microscopic uniformity of the green body, transferring the gradation advantages to subsequent processes without loss; and the three-stage sintering, through precise control of grain growth, transforms the densification advantage into excellent mechanical properties. The final ZTA ceramic has a bulk density ≥ 4.58 g / cm³. 3 Flexural strength ≥1050 MPa, fracture toughness ≥8.8 MPa·m 1 / 2 With a Vickers hardness ≥17.2 GPa, this invention achieves a balance between high strength, high toughness, and environmental friendliness. Compared to comparative studies using traditional bimodal gradation, traditional AM gel systems, or traditional single-stage sintering processes, the technical solution of this invention exhibits significant advantages in all performance aspects.

[0048] Example 3: This example provides a specific application of the ZTA ceramic prepared according to the present invention in the furnace lining of the "high-temperature corrosion zone" of a waste-to-energy incineration plant. The furnace lining of the high-temperature corrosion zone of a rotary kiln incinerator in a municipal solid waste incineration power plant is subjected to the following harsh operating conditions for extended periods: operating temperature 850-1100℃, chemical atmosphere containing HCl concentration of 1200-2500 mg / m³. 3 SO2 concentration 300-600 mg / m³ 3 It must withstand the erosion of alkali metal vapors and molten fly ash, as well as the mechanical impact of continuously fed waste falling from a height of 4 meters and the rotational stress of the rotary kiln itself. It is required to have a continuous operating cycle of ≥12 months and the furnace lining material must meet the requirements of GB / T44333-2024 "Green Product Evaluation Refractory Materials" standard.

[0049] Existing technologies have significant drawbacks in this scenario: while traditional magnesia-chrome bricks have good slag resistance, they contain Cr. 6+ These are toxic and hazardous substances with restricted use. Disposing of them as hazardous solid waste after disposal is costly, and their poor thermal shock resistance makes them prone to peeling during frequent start-ups and shutdowns of incinerators. Ordinary high-alumina bricks are prone to react with HCl and alkali metals at high temperatures to form nepheline, which causes volume expansion and structural cracking, usually requiring local repairs every 3-6 months. Silicon carbide refractory materials are easily oxidized in oxidizing atmospheres, resulting in a loose structure and a sharp decrease in strength.

[0050] Based on Example 1, this invention prepares irregularly shaped furnace lining bricks using a gel casting molding process. After 8000 hours of continuous operation at 850-1100℃ with HCl / alkali vapor, the erosion layer depth is only 0.8-1.2 mm, far lower than the 5-8 mm of ordinary high-alumina bricks. After 15 cycles of rapid cooling and heating at 1100℃ and room temperature, no cracks are generated, and the flexural strength retention rate is 92%. The flexural strength tested by sampling is 968 MPa, with a strength retention rate of 92.2%. After service, the furnace lining bricks were tested according to GB 5085.3-2007, and no heavy metal leaching concentration was detected. They can be treated as general industrial solid waste.

[0051] This embodiment demonstrates that the ZTA ceramic of the present invention, based on the Dingle model four-particle gradation, eliminates micron-level pores, preventing the infiltration of HCl and alkali vapors through capillary channels. It uses nano-yttrium oxide to stabilize zirconia phase transformation, toughening it by absorbing thermal stress and preventing crack propagation. The use of Y2O3-CeO2 chromium-free sintering aids eliminates the risk of heavy metal pollution while maintaining excellent mechanical properties. In the high-temperature corrosion zone furnace lining of waste incineration power plants, it can meet the harsh operating conditions of 850-1100℃, strong HCl / alkali vapor erosion, and frequent thermal shock, demonstrating significant value for widespread application.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength and high-toughness ZTA ceramic from a multi-graded powder, characterized in that, Includes the following steps: S1. Raw material preparation: The raw materials include four-particle-grade ZTA-based powder, sintering aid, DMAA gel system, dispersant, initiator and deionized water; The sintering aid is a composite system of yttrium oxide and cerium dioxide; the DMAA gel system includes the gel monomer N,N-dimethylacrylamide and the crosslinking agent N,N'-methylenebisacrylamide. S2. Pretreatment of four-particle-graded powder: The four-particle-graded ZTA-based powder is mixed with sintering aid, ball milling media are added for ball milling, dried and sieved to obtain graded mixed powder; S3. DMAA gel slurry preparation: DMAA monomer, MBAM crosslinking agent and dispersant are dissolved in deionized water to obtain a premix. The pH of the premix is ​​adjusted to 9-10, and then graded mixed powder is added. The mixture is ball-milled to obtain a ceramic slurry. After adding an initiator, the mixture is stirred evenly to obtain a stable slurry. S4. Injection molding and gel curing: The stable slurry is injected into the mold, cured at a constant temperature, and ZTA ceramic green body is obtained after demolding; S5. Degreasing treatment: The green blank is heated to 550-650℃ in air atmosphere and kept at this temperature to remove organic components; S6. Three-stage pressureless sintering: The degreased green body is sintered in three stages under a protective atmosphere. First, the temperature is increased to 1200℃ at 10℃ / min and held for 1 hour. Then, the temperature is increased to 1500℃ at 5℃ / min and held for 2 hours. Finally, the temperature is increased to 1600-1650℃ at 3℃ / min and held for 3 hours. After cooling, ZTA ceramic finished products are obtained.

2. The method of claim 1, wherein the multi-sized powder is used to produce a high strength and high toughness ZTA ceramic. The four-particle-grade ZTA-based powder includes particles A, B, C, and D. Particle A is α-alumina powder with a purity ≥99.9%, irregular morphology, D50 of 5-8 μm, and a mass percentage of 35%-45%; Particle B is α-alumina powder with a purity ≥99.9%, irregular flake shape, D50 of 1-3 μm, and a mass percentage of 25%-30%. The particles C are α-alumina powder with a purity ≥99.8%, irregular angular shape, D50 of 0.5-1μm, and a mass percentage of 15%-20%. The particles D are nano-yttrium oxide stabilized zirconium oxide powders with a purity ≥99.9%, irregular flocculent structure, D50 of 50-200nm, and a mass percentage of 10%-15%.

3. The method of claim 1, wherein the multi-sized powder is used to produce a high strength and high toughness ZTA ceramic. In step S1, the mass ratio of yttrium oxide to cerium dioxide in the sintering aid is 1:1 to 3:

1.

4. The method of claim 1, wherein the multi-sized powder is used to produce a high strength and high toughness ZTA ceramic. In step S1, the dispersant is ammonium polycarboxylate, and the amount added is 0.4%-0.8% of the ZTA-based powder mass; the gel monomer accounts for 5%-8% of the total mass of the slurry; the crosslinking agent is 3%-5% of the mass of DMAA; the initiator is ammonium persulfate, accounting for 0.2%-0.5% of the total mass of the slurry; and the amount of deionized water is used to adjust the solid phase volume fraction of the slurry to 55%-65%.

5. The method of claim 1, wherein the high strength and high toughness ZTA ceramic is prepared by using the multi-graded powder. In step S2, the milling media is zirconia grinding balls, the solid-liquid mass ratio is 1:1, the milling time is 6-8 hours, the milling speed is 300-400 r / min, the drying temperature is 50-65℃, and the drying time is 2-3 hours.

6. The method of claim 1, wherein the high strength and high toughness ZTA ceramic is prepared by using the multi-graded powder. In step S3, the slurry viscosity is ≤500 mPa·s.

7. The method of claim 1, wherein the high strength and high toughness ZTA ceramic is prepared by using the multi-graded powder. In step S4, the curing temperature is 60-75℃, the curing time is 2-4 hours, the relative density of the green blank is ≥62%, and the bending strength of the green blank is ≥28MPa.

8. The method of claim 1, wherein the high strength and high toughness ZTA ceramic is prepared by using the multi-graded powder. In step S5, the heating rate is 0.5-1.5℃ / min, and the holding time is 2 hours.

9. The method for preparing high-strength and high-toughness ZTA ceramics from multi-graded powder according to claim 1, characterized in that, In step S6, the protective atmosphere is argon gas with a flow rate of 0.5-1 L / min.

10. The method for preparing high-strength and high-toughness ZTA ceramics from multi-graded powder as described in claim 1, characterized in that, The volume density of the ZTA ceramic is ≥ 4.5 g / cm 3 , the bending strength is ≥ 1000 MPa, the fracture toughness is ≥ 8.5 MPa·m 1 / 2 , and the Vickers hardness is ≥ 17 GPa.

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