Method for manufacturing gradient prestressed high-pressure porcelain bushing

Abstract

The application belongs to the technical field of high-voltage porcelain sleeve pipe preparation, and particularly relates to a preparation method of gradient prestress reinforced high-voltage porcelain sleeve pipe. The preparation method comprises the following steps: (1) preparing a porcelain sleeve pipe green body; (2) preparing a porcelain sleeve pipe green body containing a first prestress transition layer; (3) preparing a porcelain sleeve pipe green body containing a second prestress transition layer; (4) preparing a porcelain sleeve pipe green body containing a third prestress transition layer; and (5) obtaining the gradient prestress reinforced high-voltage porcelain sleeve pipe. The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve pipe is designed with a gradient structure of multiple-order prestress reinforced layers, the material ratio and process parameters of each prestress transition layer are optimized, a synergistic reinforcement effect is formed between different layers, and the toughness of the high-voltage porcelain sleeve pipe is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of high-pressure porcelain bushing manufacturing technology, specifically relating to a method for manufacturing a gradient prestressed high-pressure porcelain bushing. Background Technology

[0002] High-voltage porcelain bushings are critical insulating components in power equipment, widely used in high-voltage electrical equipment such as transformers, circuit breakers, and instrument transformers, primarily serving as insulation, mechanical support, and sealing. Their performance directly affects the safe and stable operation of power equipment. High-voltage porcelain bushings are electrical porcelain products sintered at high temperatures. Improper formulations, insufficient raw material purity, or lax process control (such as uneven raw material mixing or improper sintering temperature control) during manufacturing can all lead to defects such as porosity and cracks within the porcelain component. Due to the inherent brittleness of electrical porcelain materials and their lack of plastic deformation capacity, they are subjected to mechanical stress, sudden temperature changes, and harsh environments (such as extreme low temperatures, icing, and UV aging) during long-term operation. These factors accelerate the propagation of internal defects, making high-voltage porcelain bushings highly susceptible to brittle fracture failure.

[0003] In recent years, porcelain bushing rupture accidents have occurred frequently in power grids, seriously threatening the normal operation of power equipment and the personal safety of maintenance personnel. Studies have shown that the main failure mode of porcelain bushings is brittle fracture. Their inherent high brittleness, low fracture toughness, and high sensitivity to cracks make them extremely prone to sudden failure during operation. Therefore, improving the fracture toughness of porcelain bushings is key to improving their mechanical properties.

[0004] Currently, the industry mainly employs three technical solutions to improve the mechanical properties of ceramic sleeves: particle-toughened ceramics, layered structure design, and functionally graded materials. Particle toughening, by adding toughening particles such as ZrO2, SiC, Al2O3, TiC, and Si3N4 to the matrix, hinders crack propagation. However, due to the high hardness and inherent brittleness of ceramic materials, the interfacial bonding strength between the particles and the matrix is ​​insufficient, easily leading to interfacial debonding and microcrack initiation. Furthermore, the agglomeration and uneven distribution of toughening particles introduce new stress concentration points, thus reducing the material's uniformity and reliability. Layered structure design uses alternating hard and soft structures to deflect crack paths, but the difference in thermal expansion coefficients leads to the risk of interfacial delamination. While functionally graded materials can optimize thermal stress distribution, their protection against mechanical impact is limited and the manufacturing process is complex.

[0005] Therefore, it is necessary to explore a gradient prestressed reinforced high-pressure porcelain bushing with good fracture toughness. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a gradient prestressed reinforced high-pressure porcelain bushing. The high-pressure porcelain bushing prepared by this method exhibits excellent fracture toughness.

[0007] The method for preparing gradient prestressed reinforced high-pressure porcelain bushings according to the present invention comprises the following steps:

[0008] (1) Using nano-boehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid as raw materials, a mixture is prepared. The mixture is then ball-milled for 8-8.2 hours, passed through a 200-mesh sieve, spray-granulated, and then isostatically pressed to obtain a ceramic sleeve green body.

[0009] (2) Mix the Molexite fine powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water evenly, and disperse them evenly by high-speed shearing and stirring. Then, use an automatic spraying equipment to form a uniform film on the inner and outer walls of the ceramic sleeve green body to form the first prestressed transition layer. Finally, dry the mixture to obtain the ceramic sleeve green body containing the first prestressed transition layer.

[0010] (3) Mix halloysite, fused silica powder, defoamer, zirconium hydrogen phosphate, silica-alumina sol and deionized water evenly, and ball mill in a planetary ball mill to obtain a mixed slurry. Transfer the mixed slurry into a spraying system and spray it evenly on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer. After drying, a ceramic sleeve green blank containing the second prestressed transition layer is prepared.

[0011] (4) Mix fused silica powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water evenly, and ball mill the mixture in a planetary ball mill to obtain a mixed slurry. Apply the mixture evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form the third prestressed transition layer. After drying, a ceramic sleeve green body containing the third prestressed transition layer is prepared.

[0012] (5) Nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, and polyvinyl butyral are mixed in proportion, and deionized water is added to adjust the glaze slurry viscosity to 1.1-1.3 Pa·s. After planetary ball milling, a slurry is obtained. Strontium borosilicate glass powder is added to adjust the glaze slurry specific gravity to 1.35-1.45 g / cm³. 3 After being filtered through a 325-mesh sieve and aged, the material undergoes ultrasonic oscillation to prepare a glaze. The glaze is then uniformly sprayed onto both the inner and outer sides of the third prestressed transition layer using an electrostatic spraying process to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer is prepared. Finally, after sintering, a gradient prestressed reinforced high-pressure porcelain sleeve is prepared.

[0013] in:

[0014] The ceramic sleeve green body, by mass percentage, consists of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid.

[0015] In the ceramic sleeve green body, the nano-boehmite has a particle size of 80 nm and is used to provide a highly active Al2O3 precursor. The kaolin has a particle size of 2 μm and acts as a plasticity modifier to improve molding performance. The zirconium silicate sol (30% solid content) acts as an inorganic binder, providing bonding strength in the room temperature to medium temperature range and transforming into a reinforcing phase at high temperatures. The overall effect of the Y2O3-La2O3-CeO2 composite sintering aid is to synergistically reduce the sintering temperature, optimize the microstructure, and improve the mechanical properties. Among them, Y2O3 inhibits abnormal grain growth, La2O3 promotes grain boundary diffusion, and CeO2 improves fracture toughness.

[0016] The preparation method of zirconium silicate sol in step (1) is as follows: zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as raw material. The zirconium silicate powder and deionized water are mixed at a mass ratio of 3:7. Nitric acid, accounting for 1-2% of the mass of zirconium silicate powder, is added as a dispersant to adjust the pH value of the system to 3-4. Then, the mixture is magnetically stirred for 30 minutes for preliminary mixing. The mixture is then transferred to a ball mill jar with zirconium oxide balls as the grinding medium. The ball-to-material ratio is 5:1. The mixture is ball-milled for 5-6 hours. Finally, the large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

[0017] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid mentioned in step (1) is as follows: weigh high-purity Y2O3, La2O3 and CeO2 powders (purity ≥99.9%) in a molar ratio of 4:3:3 and mix them evenly. Press the mixed powder into a green body, and then place it in a flash furnace. Under an air atmosphere, rapidly heat it to 1550-1600℃ at a heating rate of 600℃ / min and hold it for 3-5 minutes. Then rapidly cool it to obtain a dense block. Coarsely crush the dense block, and then use a zirconia ball mill jar with ethanol as the medium for high-energy ball milling for 4-6 hours with a ball-to-material ratio of 10:1. Finally, sieve to obtain D 50 =400-600nm composite sintering aid powder.

[0018] In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

[0019] The manufacturer of the nano-boehmite mentioned in step (1) is Shandong Guoci Functional Materials Co., Ltd.

[0020] The total mass of the Molekite fine powder, lanthanum-zirconium composite sol and deionized water in step (2) is 100%, wherein the Molekite fine powder is 53%-57%, the lanthanum-zirconium composite sol is 28%-32%, and the deionized water is 11%-19%.

[0021] In step (2), the mass of boron nitride nanosheets accounts for 3% of the total mass of the three components: Molekite fine powder, lanthanum-zirconium composite sol, and deionized water.

[0022] In step (2), the particle size of the Molexite fine powder is 120 μm, and the particle size of the boron nitride nanosheets is 2 μm.

[0023] In step (2), the manufacturer of the mullite fine powder is Engel Porcelain (Tianjin) New Material Technology Co., Ltd., the content of mullite phase is 55%, the content of glass phase is 45%, and the manufacturer of boron nitride nanosheets is Suzhou Napu Materials Technology Co., Ltd.

[0024] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: Lanthanum nitrate and zirconium oxychloride are weighed according to the molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and citric acid is added as a stabilizer at a molar amount of 1.5 times the total molar amount of metal ions. Then, the solution is added dropwise to ammonia water with pH=10 at a rate of 1 mL / min for co-precipitation reaction. After stirring for 2 hours, it is allowed to stand for 12 hours. The precipitate is centrifuged and washed until neutral, and then redispersed in deionized water. The pH of the system is adjusted to 3-4 with nitric acid. After hydrothermal reaction at 100℃ for 6 hours, it is ultrasonically treated to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0025] The high-speed shearing and stirring described in step (2) is to first stir at a speed of 4000 r / min for 5 min, and then stir at a speed of 2000 r / min for 20 min.

[0026] In step (2), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0027] In step (2), the thickness of the first prestressed transition layer on one side is precisely controlled to be 0.3-0.5 mm.

[0028] The drying process described in step (2) involves first keeping the product at 80°C for 4 hours, and then keeping it at 120°C for 4 hours.

[0029] In step (2), the first prestressed transition layer uses mullite fine powder as the matrix material. Its mullite phase provides high-temperature stability and mechanical strength, while the glass phase promotes sintering densification. Boron nitride nanosheets enhance the thermal conductivity of the material due to their two-dimensional structure and introduce beneficial compressive prestress into the matrix through their low thermal expansion characteristics. Lanthanum-zirconium composite sol, as the key binding phase, forms a three-dimensional network structure during the drying stage to provide initial strength. At high temperatures, it transforms into the La2Zr2O7 pyrochlore phase to achieve a gradient transition in the coefficient of thermal expansion. At the same time, La... 3+ The grain boundary segregation effect effectively inhibits abnormal grain growth.

[0030] In step (3), the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate is 100%, wherein halloysite accounts for 43%-47%, fused silica powder accounts for 18%-22%, deionized water accounts for 18%-22%, silica-alumina sol accounts for 7%-13%, and zirconium hydrogen phosphate accounts for 4%-6%.

[0031] In step (3), the mass of the defoamer accounts for 1.5% of the total mass of halloysite, fused silica powder, deionized water, silica alumina sol, and zirconium hydrogen phosphate.

[0032] The halloysite in step (3) has a particle size of 10 μm, and the fused silica powder has a particle size of 30 μm.

[0033] In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0034] In step (3), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0035] In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.6-0.9 mm.

[0036] The drying process described in step (3) involves first drying at 80°C for 4 hours, and then keeping warm at 120°C for 4 hours.

[0037] The defoamer mentioned in step (3) is a high-temperature resistant defoamer. The manufacturer of the high-temperature resistant defoamer is Anhui Aiyota Silicon Oil Co., Ltd., and the model is IOTA 3038-15. The manufacturer of zirconium hydrogen phosphate is Shanghai McLean Biochemical Technology Co., Ltd., and the manufacturer of silica-alumina sol is Suzhou Nadi Microelectronics Co., Ltd.

[0038] In step (3), in the second prestressed transition layer, halloysite provides structural support, enhances mechanical strength and thermal stability, fused silica powder adjusts the coefficient of thermal expansion, zirconium hydrogen phosphate acts as a high-temperature binder to promote the formation of stable phosphate bonds during sintering and improve interlayer bonding strength, aluminosilicate sol provides nano-sized aluminosilicate oxide particles to improve slurry dispersibility and enhance interfacial bonding after high-temperature sintering, and high-temperature defoamer eliminates slurry bubbles, prevents pores or cracks from appearing after coating drying, and improves density.

[0039] In step (4), the total mass of fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate, and scandium-stabilized cerium-zirconium composite powder is 100%, of which fused silica powder accounts for 63-67%, aluminum phosphate sol accounts for 13-18%, deionized water accounts for 13-22%, sodium polycarboxylate accounts for 1.2-1.8%, and scandium-stabilized cerium-zirconium composite powder accounts for 0.2-0.8%.

[0040] The particle size of the fused silica powder in step (4) is 25 μm.

[0041] In step (4), the aluminum phosphate sol is manufactured by Wuhan Jiyesheng Chemical Co., Ltd., with a solid content of 40%. The scandium stabilized cerium zirconium composite powder is manufactured by Hunan Rare Earth Metal Materials Research Institute Co., Ltd., and the sodium polycarboxylate dispersant is manufactured by Kedeli Chemical Technology Co., Ltd., with the model name SAMASO DP5045.

[0042] In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0043] In step (4), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm.

[0044] In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.4-0.6 mm.

[0045] The drying conditions described in step (4) are: first, dry at 80°C for 4 hours, and then keep warm at 120°C for 4 hours.

[0046] In the third prestressed transition layer described in step (4), fused silica powder serves as a filler to reduce the coefficient of thermal expansion and enhance high-temperature stability. Aluminum phosphate sol serves as a binder to achieve high-temperature bonding and promote sintering. Sodium polycarboxylate dispersant improves slurry dispersibility and prevents particle agglomeration. Scandium-stabilized cerium-zirconium composite powder enhances material density and fracture toughness.

[0047] In step (5), the total mass of nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water is 100%, of which nano-alumina accounts for 28%-32%, yttrium-stabilized zirconium oxide accounts for 23%-27%, silica sol accounts for 13%-17%, sodium polyacrylate dispersant accounts for 0.8%-1.2%, polyvinyl butyral accounts for 3.5%-4.5%, and deionized water accounts for 22.3%-27.7%.

[0048] In step (5), the strontium borosilicate glass powder is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the six components: nano alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0049] In step (5), the strontium borosilicate glass powder is manufactured by Suzhou Qiuyi New Materials Co., Ltd.

[0050] In step (5), the particle size of nano alumina is 3 μm, the particle size of yttrium-stabilized zirconium oxide is 0.8 μm, the solid content of silica sol is 30%, sodium polyacrylate is liquid with a molecular weight of 8000, the particle size of polyvinyl butyral powder is 50 μm, and the particle size of strontium borosilicate glass powder is 10 μm.

[0051] In step (5), when preparing the glaze, the role of nano-alumina is to improve the hardness and wear resistance of the glaze layer, the role of yttrium-stabilized zirconia powder is to enhance the toughness and thermal shock resistance of the glaze layer, polyvinyl butyral is used as an organic binder to improve the molding performance of the glaze, strontium borosilicate glass powder plays the role of lowering the melting temperature of the glaze and promoting the densification of the glaze layer, and the role of silica sol is to improve the dispersion stability of the glaze and form a silicon-oxygen network during sintering to enhance adhesion.

[0052] In step (5), the ball milling speed is 400 r / min and the ball milling time is 6 h.

[0053] In step (5), the aging time is 24 hours and the aging temperature is room temperature.

[0054] In step (5), the ultrasonic conditions are 10 minutes of ultrasonic oscillation every 2 hours.

[0055] In step (5), the electrostatic spraying voltage is 50-60kV.

[0056] In step (5), the thickness of the glaze layer on one side is controlled at 0.2-0.3 mm.

[0057] The drying process described in step (5) involves drying in an oven at 80-100℃ for 1-2 hours to allow the glaze to initially solidify.

[0058] The sintering process in step (5) involves heating from 100°C to 700°C at a rate of 5°C / min, then heating from 700°C to 1000°C at a rate of 4°C / min, heating from 1000°C to 1210°C at a rate of 3°C / min, heating from 1210°C to 1290°C at a rate of 2°C / min, heating from 1290°C to 1300°C at a rate of 1°C / min and holding at that temperature for 2 hours. The furnace is then cooled to room temperature before the furnace is removed from the furnace.

[0059] The gradient prestressed reinforced high-pressure porcelain bushing described in step (5) consists of, from the outside to the inside, a glaze layer, a third prestressed transition layer, a second prestressed transition layer, a first prestressed transition layer, a porcelain bushing, a first prestressed transition layer, a second prestressed transition layer, a third prestressed transition layer, and a glaze layer.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] (1) The method for preparing the gradient prestressed reinforced high-pressure porcelain bushing of the present invention designs a multi-stage prestressed reinforcement layer with a gradient structure. By optimizing the material ratio and process parameters of each prestressed transition layer, a synergistic reinforcement effect is formed between different layers, thereby enhancing the toughness of the high-pressure porcelain bushing.

[0062] (2) The method for preparing the gradient prestressed reinforced high-pressure porcelain bushing described in this invention forms a progressive stress transition between the porcelain bushing green and the external reinforcing layer through the optimized design of the gradient prestress layer, which effectively inhibits crack propagation and significantly improves the fracture toughness and impact resistance of the high-pressure porcelain bushing, so that it can still maintain excellent mechanical stability under complex working conditions.

[0063] (3) The method for preparing the gradient prestressed reinforced high-pressure porcelain bushing of the present invention introduces a multi-stage prestressed layer composed of a Molexite prestressed layer (first prestressed transition layer), an halloysite and fused silica powder prestressed layer (second prestressed transition layer), and a fused silica powder prestressed layer (third prestressed transition layer) to form a gradient structure prestressed layer reinforced porcelain bushing. A good bonding interface is formed between the toughening layer and the porcelain bushing blank. The crack propagation process is conducive to the consumption of strain energy, thereby improving toughness. The multi-stage toughening layer formed can effectively protect the porcelain bushing blank in the process of sudden fracture of the high-pressure porcelain bushing.

[0064] (4) The method for preparing the gradient prestressed reinforced high pressure porcelain sleeve described in this invention uses a gradient control method of thermal expansion coefficient, namely, the thermal expansion coefficient of the green layer of the porcelain sleeve > the thermal expansion coefficient of the first prestressed transition layer > the thermal expansion coefficient of the second prestressed transition layer > the thermal expansion coefficient of the third prestressed transition layer, symmetrical structural design and gradient distribution characteristics of residual compressive stress field to ensure uniform stress transition and avoid delamination or stress concentration. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the structure of a gradient prestressed reinforced high-pressure porcelain bushing; in the diagram, 1 is the porcelain bushing blank; 2 is the first prestressed transition layer; 3 is the second prestressed transition layer; 4 is the third prestressed transition layer; and 5 is the glaze layer. Detailed Implementation

[0066] Example 1

[0067] The preparation method of the gradient prestressed reinforced high-pressure ceramic bushing described in Example 1 consists of the following steps:

[0068] (1) Using nano-boehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid as raw materials, a mixture is prepared. The mixture is then ball-milled for 8.1 hours, passed through a 200-mesh sieve, spray-granulated, and then isostatically pressed to obtain a ceramic sleeve green body.

[0069] (2) Mix the Molexite fine powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water evenly, and disperse them evenly by high-speed shearing and stirring. Then, use an automatic spraying equipment to form a uniform film on the inner and outer walls of the ceramic sleeve green body to form the first prestressed transition layer. Finally, dry the mixture to obtain the ceramic sleeve green body containing the first prestressed transition layer.

[0070] (3) Mix halloysite, fused silica powder, defoamer, zirconium hydrogen phosphate, silica-alumina sol and deionized water evenly, and ball mill in a planetary ball mill to obtain a mixed slurry. Transfer the mixed slurry into a spraying system and spray it evenly on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer. After drying, a ceramic sleeve green blank containing the second prestressed transition layer is prepared.

[0071] (4) Mix fused silica powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water evenly, and ball mill the mixture in a planetary ball mill to obtain a mixed slurry. Apply the mixture evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form the third prestressed transition layer. After drying, a ceramic sleeve green body containing the third prestressed transition layer is prepared.

[0072] (5) Nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, and polyvinyl butyral are mixed in proportion, and deionized water is added to adjust the glaze slurry viscosity to 1.2 Pa·s. After planetary ball milling, a slurry is obtained, and strontium borosilicate glass powder is added to adjust the glaze slurry specific gravity to 1.40 g / cm³. 3 After being filtered through a 325-mesh sieve and aged, the material undergoes ultrasonic oscillation to prepare a glaze. The glaze is then uniformly sprayed onto both the inner and outer sides of the third prestressed transition layer using an electrostatic spraying process to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer is prepared. Finally, after sintering, a gradient prestressed reinforced high-pressure porcelain sleeve is prepared.

[0073] in:

[0074] The ceramic sleeve green body, by mass percentage, consists of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid.

[0075] In the ceramic sleeve green body, the particle size of nanoboehmite is 80 nm and the particle size of kaolinite is 2 μm.

[0076] The method for preparing zirconium silicate sol in step (1) is as follows: zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as raw material. The zirconium silicate powder and deionized water are mixed at a mass ratio of 3:7. Nitric acid at a mass of 1.5% of the zirconium silicate powder is added as a dispersant to adjust the pH value of the system to 3.5. Then, the mixture is magnetically stirred for 30 minutes for preliminary mixing. The mixture is then transferred to a ball mill jar with zirconium oxide balls as the grinding medium at a ball-to-material ratio of 5:1. The mixture is ball-milled for 5.5 hours. Finally, the large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

[0077] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid mentioned in step (1) is as follows: high-purity Y2O3, La2O3 and CeO2 powders (purity ≥99.9%) are weighed in a molar ratio of 4:3:3 and mixed evenly. The mixed powder is pressed into a green body and then placed in a flash furnace. Under an air atmosphere, the temperature is rapidly increased to 1575℃ at a heating rate of 600℃ / min and held for 4 minutes. Then, it is rapidly cooled to obtain a dense block. The dense block is coarsely crushed and then high-energy ball milled for 5 hours in a zirconia ball mill jar with ethanol as the medium. The ball-to-material ratio is 10:1. Finally, it is sieved to obtain D. 50 =500nm composite sintering aid powder.

[0078] In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

[0079] The manufacturer of the nano-boehmite mentioned in step (1) is Shandong Guoci Functional Materials Co., Ltd.

[0080] The total mass of the Molekt fine powder, lanthanum-zirconium composite sol and deionized water in step (2) is 100%, of which the Molekt fine powder is 55%, the lanthanum-zirconium composite sol is 30%, and the deionized water is 15%.

[0081] In step (2), the mass of boron nitride nanosheets accounts for 3% of the total mass of the three components: Molekite fine powder, lanthanum-zirconium composite sol, and deionized water.

[0082] In step (2), the particle size of the Molexite fine powder is 120 μm, and the particle size of the boron nitride nanosheets is 2 μm.

[0083] In step (2), the manufacturer of the mullite fine powder is Engel Porcelain (Tianjin) New Material Technology Co., Ltd., the content of mullite phase is 55%, the content of glass phase is 45%, and the manufacturer of boron nitride nanosheets is Suzhou Napu Materials Technology Co., Ltd.

[0084] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: Lanthanum nitrate and zirconium oxychloride are weighed according to the molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and citric acid is added as a stabilizer at a molar amount of 1.5 times the total molar amount of metal ions. Then, the solution is added dropwise to ammonia water with pH=10 at a rate of 1 mL / min for co-precipitation reaction. After stirring for 2 hours, it is allowed to stand for 12 hours. The precipitate is centrifuged and washed until neutral, and then redispersed in deionized water. The pH of the system is adjusted to 3.5 with nitric acid. After hydrothermal reaction at 100℃ for 6 hours, it is ultrasonically treated to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0085] The high-speed shearing and stirring described in step (2) is to first stir at a speed of 4000 r / min for 5 min, and then stir at a speed of 2000 r / min for 20 min.

[0086] In step (2), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0087] In step (2), the thickness of the first prestressed transition layer on one side is precisely controlled to be 0.4 mm.

[0088] The drying process described in step (2) involves first keeping the product at 80°C for 4 hours, and then keeping it at 120°C for 4 hours.

[0089] In step (3), the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate is 100%, of which halloysite accounts for 45%, fused silica powder accounts for 20%, deionized water accounts for 21%, silica-alumina sol accounts for 9%, and zirconium hydrogen phosphate accounts for 5%.

[0090] In step (3), the mass of the defoamer accounts for 1.5% of the total mass of halloysite, fused silica powder, deionized water, silica alumina sol, and zirconium hydrogen phosphate.

[0091] The halloysite in step (3) has a particle size of 10 μm, and the fused silica powder has a particle size of 30 μm.

[0092] In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0093] In step (3), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0094] In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.8 mm.

[0095] The drying process described in step (3) involves first drying at 80°C for 4 hours, and then keeping warm at 120°C for 4 hours.

[0096] The defoamer mentioned in step (3) is a high-temperature resistant defoamer. The manufacturer of the high-temperature resistant defoamer is Anhui Aiyota Silicon Oil Co., Ltd., and the model is IOTA 3038-15. The manufacturer of zirconium hydrogen phosphate is Shanghai McLean Biochemical Technology Co., Ltd., and the manufacturer of silica-alumina sol is Suzhou Nadi Microelectronics Co., Ltd.

[0097] In step (4), the total mass of fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100%, of which fused silica powder accounts for 65%, aluminum phosphate sol accounts for 15%, deionized water accounts for 18%, sodium polycarboxylate accounts for 1.6%, and scandium-stabilized cerium-zirconium composite powder accounts for 0.4%.

[0098] The particle size of the fused silica powder in step (4) is 25 μm.

[0099] In step (4), the aluminum phosphate sol is manufactured by Wuhan Jiyesheng Chemical Co., Ltd., with a solid content of 40%. The scandium stabilized cerium zirconium composite powder is manufactured by Hunan Rare Earth Metal Materials Research Institute Co., Ltd., and the sodium polycarboxylate dispersant is manufactured by Kedeli Chemical Technology Co., Ltd., with the model name SAMASO DP5045.

[0100] In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0101] In step (4), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm.

[0102] In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.5 mm.

[0103] The drying conditions described in step (4) are: first, dry at 80°C for 4 hours, and then keep warm at 120°C for 4 hours.

[0104] In step (5), the total mass of nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water is 100%, of which nano-alumina accounts for 30%, yttrium-stabilized zirconium oxide accounts for 25%, silica sol accounts for 15%, sodium polyacrylate dispersant accounts for 1.0%, polyvinyl butyral accounts for 4.0%, and deionized water accounts for 25%.

[0105] In step (5), the strontium borosilicate glass powder is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the six components: nano alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0106] In step (5), the strontium borosilicate glass powder is manufactured by Suzhou Qiuyi New Materials Co., Ltd.

[0107] In step (5), the particle size of nano alumina is 3 μm, the particle size of yttrium-stabilized zirconium oxide is 0.8 μm, the solid content of silica sol is 30%, sodium polyacrylate is liquid with a molecular weight of 8000, the particle size of polyvinyl butyral powder is 50 μm, and the particle size of strontium borosilicate glass powder is 10 μm.

[0108] In step (5), the ball milling speed is 400 r / min and the ball milling time is 6 h.

[0109] In step (5), the aging time is 24 hours and the aging temperature is room temperature.

[0110] In step (5), the ultrasonic conditions are 10 minutes of ultrasonic oscillation every 2 hours.

[0111] In step (5), the electrostatic spraying voltage is 55kV.

[0112] In step (5), the thickness of the glaze layer on one side is controlled at 0.25 mm.

[0113] The drying process described in step (5) involves drying in an oven at 90°C for 1.5 hours to allow the glaze layer to initially solidify.

[0114] The sintering process in step (5) involves heating from 100°C to 700°C at a rate of 5°C / min, then heating from 700°C to 1000°C at a rate of 4°C / min, heating from 1000°C to 1210°C at a rate of 3°C / min, heating from 1210°C to 1290°C at a rate of 2°C / min, heating from 1290°C to 1300°C at a rate of 1°C / min and holding at that temperature for 2 hours. The furnace is then cooled to room temperature before the furnace is removed from the furnace.

[0115] The gradient prestressed reinforced high-pressure porcelain bushing described in step (5) consists of, from the outside to the inside, a glaze layer, a third prestressed transition layer, a second prestressed transition layer, a first prestressed transition layer, a porcelain bushing, a first prestressed transition layer, a second prestressed transition layer, a third prestressed transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Example 1, measured by the single-sided notched beam method, has a fracture toughness of 10.2 MPa·m. 1 / 2 .

[0116] Example 2

[0117] The preparation method of the gradient prestressed reinforced high-pressure ceramic bushing described in Example 2 consists of the following steps:

[0118] (1) Using nano-boehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid as raw materials, a mixture is prepared. The mixture is then ball-milled for 8 hours, passed through a 200-mesh sieve, spray-granulated, and then isostatically pressed to obtain a ceramic sleeve green body.

[0119] (2) Mix the Molexite fine powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water evenly, and disperse them evenly by high-speed shearing and stirring. Then, use an automatic spraying equipment to form a uniform film on the inner and outer walls of the ceramic sleeve green body to form the first prestressed transition layer. Finally, dry the mixture to obtain the ceramic sleeve green body containing the first prestressed transition layer.

[0120] (3) Mix halloysite, fused silica powder, defoamer, zirconium hydrogen phosphate, silica-alumina sol and deionized water evenly, and ball mill in a planetary ball mill to obtain a mixed slurry. Transfer the mixed slurry into a spraying system and spray it evenly on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer. After drying, a ceramic sleeve green blank containing the second prestressed transition layer is prepared.

[0121] (4) Mix fused silica powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water evenly, and ball mill the mixture in a planetary ball mill to obtain a mixed slurry. Apply the mixture evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form the third prestressed transition layer. After drying, a ceramic sleeve green body containing the third prestressed transition layer is prepared.

[0122] (5) Nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, and polyvinyl butyral are mixed in proportion, and deionized water is added to adjust the glaze slurry viscosity to 1.1 Pa·s. After planetary ball milling, a slurry is obtained, and strontium borosilicate glass powder is added to adjust the glaze slurry specific gravity to 1.35 g / cm³. 3 After being filtered through a 325-mesh sieve and aged, the material undergoes ultrasonic oscillation to prepare a glaze. The glaze is then uniformly sprayed onto both the inner and outer sides of the third prestressed transition layer using an electrostatic spraying process to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer is prepared. Finally, after sintering, a gradient prestressed reinforced high-pressure porcelain sleeve is prepared.

[0123] in:

[0124] The ceramic sleeve green body, by mass percentage, consists of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid.

[0125] In the ceramic sleeve green body, the particle size of nanoboehmite is 80 nm and the particle size of kaolinite is 2 μm.

[0126] The preparation method of zirconium silicate sol in step (1) is as follows: zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as raw material. The zirconium silicate powder and deionized water are mixed at a mass ratio of 3:7. Nitric acid at a mass of 2% of zirconium silicate powder is added as a dispersant to adjust the pH value of the system to 3. Then, the mixture is magnetically stirred for 30 minutes for preliminary mixing. The mixture is then transferred to a ball mill jar with zirconium oxide balls as the grinding medium at a ball-to-material ratio of 5:1. The mixture is ball-milled for 5 hours. Finally, large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

[0127] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid mentioned in step (1) is as follows: weigh high-purity Y2O3, La2O3 and CeO2 powders (purity ≥99.9%) in a molar ratio of 4:3:3 and mix them evenly. Press the mixed powder into a green body, and then place it in a flash furnace. Under an air atmosphere, rapidly heat it to 1550℃ at a heating rate of 600℃ / min and hold it at that temperature for 5 minutes. Then rapidly cool it to obtain a dense block. The dense block is coarsely crushed, and then high-energy ball milled for 4 hours in a zirconia ball mill jar with ethanol as the medium. The ball-to-material ratio is 10:1. Finally, it is sieved to obtain D. 50 =600nm composite sintering aid powder.

[0128] In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

[0129] The manufacturer of the nano-boehmite mentioned in step (1) is Shandong Guoci Functional Materials Co., Ltd.

[0130] The total mass of the Molekt fine powder, lanthanum-zirconium composite sol and deionized water in step (2) is 100%, of which the Molekt fine powder is 53%, the lanthanum-zirconium composite sol is 28%, and the deionized water is 19%.

[0131] In step (2), the mass of boron nitride nanosheets accounts for 3% of the total mass of the three components: Molekite fine powder, lanthanum-zirconium composite sol, and deionized water.

[0132] In step (2), the particle size of the Molexite fine powder is 120 μm, and the particle size of the boron nitride nanosheets is 2 μm.

[0133] In step (2), the manufacturer of the mullite fine powder is Engel Porcelain (Tianjin) New Material Technology Co., Ltd., the content of mullite phase is 55%, the content of glass phase is 45%, and the manufacturer of boron nitride nanosheets is Suzhou Napu Materials Technology Co., Ltd.

[0134] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: Lanthanum nitrate and zirconium oxychloride are weighed according to the molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and citric acid is added as a stabilizer at a molar amount of 1.5 times the total molar amount of metal ions. Then, the solution is added dropwise to ammonia water with pH=10 at a rate of 1 mL / min for co-precipitation reaction. After stirring for 2 hours, it is allowed to stand for 12 hours. The precipitate is centrifuged and washed until neutral, and then redispersed in deionized water. The pH of the system is adjusted to 4 with nitric acid. After hydrothermal reaction at 100℃ for 6 hours, it is ultrasonically treated to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0135] The high-speed shearing and stirring described in step (2) is to first stir at a speed of 4000 r / min for 5 min, and then stir at a speed of 2000 r / min for 20 min.

[0136] In step (2), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0137] In step (2), the thickness of the first prestressed transition layer on one side is precisely controlled to be 0.5 mm.

[0138] The drying process described in step (2) involves first keeping the product at 80°C for 4 hours, and then keeping it at 120°C for 4 hours.

[0139] In step (3), the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate is 100%, of which halloysite accounts for 43%, fused silica powder accounts for 22%, deionized water accounts for 18%, silica-alumina sol accounts for 13%, and zirconium hydrogen phosphate accounts for 4%.

[0140] In step (3), the mass of the defoamer accounts for 1.5% of the total mass of halloysite, fused silica powder, deionized water, silica alumina sol, and zirconium hydrogen phosphate.

[0141] The halloysite in step (3) has a particle size of 10 μm, and the fused silica powder has a particle size of 30 μm.

[0142] In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0143] In step (3), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0144] In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.9 mm.

[0145] The drying process described in step (3) involves first drying at 80°C for 4 hours, and then keeping warm at 120°C for 4 hours.

[0146] The defoamer mentioned in step (3) is a high-temperature resistant defoamer. The manufacturer of the high-temperature resistant defoamer is Anhui Aiyota Silicon Oil Co., Ltd., and the model is IOTA 3038-15. The manufacturer of zirconium hydrogen phosphate is Shanghai McLean Biochemical Technology Co., Ltd., and the manufacturer of silica-alumina sol is Suzhou Nadi Microelectronics Co., Ltd.

[0147] In step (4), the total mass of fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100%, of which fused silica powder accounts for 63%, aluminum phosphate sol accounts for 13%, deionized water accounts for 22%, sodium polycarboxylate accounts for 1.2% and scandium-stabilized cerium-zirconium composite powder accounts for 0.8%.

[0148] The particle size of the fused silica powder in step (4) is 25 μm.

[0149] In step (4), the aluminum phosphate sol is manufactured by Wuhan Jiyesheng Chemical Co., Ltd., with a solid content of 40%. The scandium stabilized cerium zirconium composite powder is manufactured by Hunan Rare Earth Metal Materials Research Institute Co., Ltd., and the sodium polycarboxylate dispersant is manufactured by Kedeli Chemical Technology Co., Ltd., with the model name SAMASO DP5045.

[0150] In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0151] In step (4), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm.

[0152] In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.6 mm.

[0153] The drying conditions described in step (4) are: first, dry at 80°C for 4 hours, and then keep warm at 120°C for 4 hours.

[0154] In step (5), the total mass of nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water is 100%, of which nano-alumina accounts for 28%, yttrium-stabilized zirconium oxide accounts for 27%, silica sol accounts for 13%, sodium polyacrylate dispersant accounts for 0.8%, polyvinyl butyral accounts for 3.5%, and deionized water accounts for 27.7%.

[0155] In step (5), the strontium borosilicate glass powder is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the six components: nano alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0156] In step (5), the strontium borosilicate glass powder is manufactured by Suzhou Qiuyi New Materials Co., Ltd.

[0157] In step (5), the particle size of nano alumina is 3 μm, the particle size of yttrium-stabilized zirconium oxide is 0.8 μm, the solid content of silica sol is 30%, sodium polyacrylate is liquid with a molecular weight of 8000, the particle size of polyvinyl butyral powder is 50 μm, and the particle size of strontium borosilicate glass powder is 10 μm.

[0158] In step (5), the ball milling speed is 400 r / min and the ball milling time is 6 h.

[0159] In step (5), the aging time is 24 hours and the aging temperature is room temperature.

[0160] In step (5), the ultrasonic conditions are 10 minutes of ultrasonic oscillation every 2 hours.

[0161] In step (5), the electrostatic spraying voltage is 50kV.

[0162] In step (5), the thickness of the glaze layer on one side is controlled at 0.3 mm.

[0163] The drying process described in step (5) involves drying in an oven at 80°C for 2 hours to allow the glaze to initially solidify.

[0164] The sintering process in step (5) involves heating from 100°C to 700°C at a rate of 5°C / min, then heating from 700°C to 1000°C at a rate of 4°C / min, heating from 1000°C to 1210°C at a rate of 3°C / min, heating from 1210°C to 1290°C at a rate of 2°C / min, heating from 1290°C to 1300°C at a rate of 1°C / min and holding at that temperature for 2 hours. The furnace is then cooled to room temperature before the furnace is removed from the furnace.

[0165] The gradient prestressed reinforced high-pressure porcelain bushing described in step (5) consists of, from the outside to the inside, a glaze layer, a third prestressed transition layer, a second prestressed transition layer, a first prestressed transition layer, a porcelain bushing, a first prestressed transition layer, a second prestressed transition layer, a third prestressed transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Example 2, measured by the single-sided notched beam method, has a fracture toughness of 9.8 MPa·m. 1 / 2 .

[0166] Example 3

[0167] The preparation method of the gradient prestressed reinforced high-pressure ceramic bushing described in Example 3 consists of the following steps:

[0168] (1) Using nano-boehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid as raw materials, a mixture is prepared. The mixture is then ball-milled for 8.2 hours, passed through a 200-mesh sieve, spray-granulated, and then isostatically pressed to obtain a ceramic sleeve green body.

[0169] (2) Mix the Molexite fine powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water evenly, and disperse them evenly by high-speed shearing and stirring. Then, use an automatic spraying equipment to form a uniform film on the inner and outer walls of the ceramic sleeve green body to form the first prestressed transition layer. Finally, dry the mixture to obtain the ceramic sleeve green body containing the first prestressed transition layer.

[0170] (3) Mix halloysite, fused silica powder, defoamer, zirconium hydrogen phosphate, silica-alumina sol and deionized water evenly, and ball mill in a planetary ball mill to obtain a mixed slurry. Transfer the mixed slurry into a spraying system and spray it evenly on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer. After drying, a ceramic sleeve green blank containing the second prestressed transition layer is prepared.

[0171] (4) Mix fused silica powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water evenly, and ball mill the mixture in a planetary ball mill to obtain a mixed slurry. Apply the mixture evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form the third prestressed transition layer. After drying, a ceramic sleeve green body containing the third prestressed transition layer is prepared.

[0172] (5) Nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, and polyvinyl butyral were mixed in proportion, and deionized water was added to adjust the glaze slurry viscosity to 1.3 Pa·s. After planetary ball milling, a slurry was obtained, and strontium borosilicate glass powder was added to adjust the glaze slurry specific gravity to 1.45 g / cm³. 3 After being filtered through a 325-mesh sieve and aged, the material undergoes ultrasonic oscillation to prepare a glaze. The glaze is then uniformly sprayed onto both the inner and outer sides of the third prestressed transition layer using an electrostatic spraying process to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer is prepared. Finally, after sintering, a gradient prestressed reinforced high-pressure porcelain sleeve is prepared.

[0173] in:

[0174] The ceramic sleeve green body, by mass percentage, consists of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid.

[0175] In the ceramic sleeve green body, the particle size of nanoboehmite is 80 nm and the particle size of kaolinite is 2 μm.

[0176] The preparation method of zirconium silicate sol in step (1) is as follows: zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as raw material. The zirconium silicate powder and deionized water are mixed at a mass ratio of 3:7. Nitric acid at a mass of 1% of zirconium silicate powder is added as a dispersant to adjust the pH value of the system to 4. Then, the mixture is magnetically stirred for 30 minutes for preliminary mixing. The mixture is then transferred to a ball mill jar with zirconium oxide balls as the grinding medium at a ball-to-material ratio of 5:1. The mixture is ball-milled for 6 hours. Finally, large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

[0177] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid mentioned in step (1) is as follows: high-purity Y2O3, La2O3 and CeO2 powders (purity ≥99.9%) are weighed in a molar ratio of 4:3:3 and mixed evenly. The mixed powder is pressed into a green body and then placed in a flash furnace. Under an air atmosphere, the temperature is rapidly increased to 1600℃ at a heating rate of 600℃ / min and held for 3 minutes. Then, it is rapidly cooled to obtain a dense block. The dense block is coarsely crushed and then high-energy ball milled for 6 hours in a zirconia ball mill jar with ethanol as the medium. The ball-to-material ratio is 10:1. Finally, it is sieved to obtain D. 50 =400nm composite sintering aid powder.

[0178] In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

[0179] The manufacturer of the nano-boehmite mentioned in step (1) is Shandong Guoci Functional Materials Co., Ltd.

[0180] The total mass of the Molekt fine powder, lanthanum-zirconium composite sol and deionized water in step (2) is 100%, of which the Molekt fine powder is 57%, the lanthanum-zirconium composite sol is 32%, and the deionized water is 11%.

[0181] In step (2), the mass of boron nitride nanosheets accounts for 3% of the total mass of the three components: Molekite fine powder, lanthanum-zirconium composite sol, and deionized water.

[0182] In step (2), the particle size of the Molexite fine powder is 120 μm, and the particle size of the boron nitride nanosheets is 2 μm.

[0183] In step (2), the manufacturer of the mullite fine powder is Engel Porcelain (Tianjin) New Material Technology Co., Ltd., the content of mullite phase is 55%, the content of glass phase is 45%, and the manufacturer of boron nitride nanosheets is Suzhou Napu Materials Technology Co., Ltd.

[0184] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: Lanthanum nitrate and zirconium oxychloride are weighed according to the molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and citric acid is added as a stabilizer at a molar amount of 1.5 times the total molar amount of metal ions. Then, the solution is added dropwise to ammonia water with pH=10 at a rate of 1 mL / min for co-precipitation reaction. After stirring for 2 hours, it is allowed to stand for 12 hours. The precipitate is centrifuged and washed until neutral, and then redispersed in deionized water. The pH of the system is adjusted to 3 with nitric acid. After hydrothermal reaction at 100℃ for 6 hours, it is ultrasonically treated to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0185] The high-speed shearing and stirring described in step (2) is to first stir at a speed of 4000 r / min for 5 min, and then stir at a speed of 2000 r / min for 20 min.

[0186] In step (2), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0187] In step (2), the thickness of the first prestressed transition layer on one side is precisely controlled to be 0.3 mm.

[0188] The drying process described in step (2) involves first keeping the product at 80°C for 4 hours, and then keeping it at 120°C for 4 hours.

[0189] In step (3), the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate is 100%, of which halloysite accounts for 47%, fused silica powder accounts for 18%, deionized water accounts for 22%, silica-alumina sol accounts for 7%, and zirconium hydrogen phosphate accounts for 6%.

[0190] In step (3), the mass of the defoamer accounts for 1.5% of the total mass of halloysite, fused silica powder, deionized water, silica alumina sol, and zirconium hydrogen phosphate.

[0191] The halloysite in step (3) has a particle size of 10 μm, and the fused silica powder has a particle size of 30 μm.

[0192] In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0193] In step (3), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0194] In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.6 mm.

[0195] The drying process described in step (3) involves first drying at 80°C for 4 hours, and then keeping warm at 120°C for 4 hours.

[0196] The defoamer mentioned in step (3) is a high-temperature resistant defoamer. The manufacturer of the high-temperature resistant defoamer is Anhui Aiyota Silicon Oil Co., Ltd., and the model is IOTA 3038-15. The manufacturer of zirconium hydrogen phosphate is Shanghai McLean Biochemical Technology Co., Ltd., and the manufacturer of silica-alumina sol is Suzhou Nadi Microelectronics Co., Ltd.

[0197] In step (4), the total mass of fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100%, of which fused silica powder accounts for 67%, aluminum phosphate sol accounts for 18%, deionized water accounts for 13%, sodium polycarboxylate accounts for 1.8% and scandium-stabilized cerium-zirconium composite powder accounts for 0.2%.

[0198] The particle size of the fused silica powder in step (4) is 25 μm.

[0199] In step (4), the aluminum phosphate sol is manufactured by Wuhan Jiyesheng Chemical Co., Ltd., with a solid content of 40%. The scandium stabilized cerium zirconium composite powder is manufactured by Hunan Rare Earth Metal Materials Research Institute Co., Ltd., and the sodium polycarboxylate dispersant is manufactured by Kedeli Chemical Technology Co., Ltd., with the model name SAMASO DP5045.

[0200] In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0201] In step (4), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm.

[0202] In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.4 mm.

[0203] The drying conditions described in step (4) are: first, dry at 80°C for 4 hours, and then keep warm at 120°C for 4 hours.

[0204] In step (5), the total mass of nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water is 100%, of which nano-alumina accounts for 32%, yttrium-stabilized zirconium oxide accounts for 23%, silica sol accounts for 17%, sodium polyacrylate dispersant accounts for 1.2%, polyvinyl butyral accounts for 4.5%, and deionized water accounts for 22.3%.

[0205] In step (5), the strontium borosilicate glass powder is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the six components: nano alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0206] In step (5), the strontium borosilicate glass powder is manufactured by Suzhou Qiuyi New Materials Co., Ltd.

[0207] In step (5), the particle size of nano alumina is 3 μm, the particle size of yttrium-stabilized zirconium oxide is 0.8 μm, the solid content of silica sol is 30%, sodium polyacrylate is liquid with a molecular weight of 8000, the particle size of polyvinyl butyral powder is 50 μm, and the particle size of strontium borosilicate glass powder is 10 μm.

[0208] In step (5), the ball milling speed is 400 r / min and the ball milling time is 6 h.

[0209] In step (5), the aging time is 24 hours and the aging temperature is room temperature.

[0210] In step (5), the ultrasonic conditions are 10 minutes of ultrasonic oscillation every 2 hours.

[0211] In step (5), the electrostatic spraying voltage is 60kV.

[0212] In step (5), the thickness of the glaze layer on one side is controlled at 0.2 mm.

[0213] The drying process described in step (5) involves drying the glaze layer in an oven at 100°C for 1 hour to allow it to initially solidify.

[0214] The sintering process in step (5) involves heating from 100°C to 700°C at a rate of 5°C / min, then heating from 700°C to 1000°C at a rate of 4°C / min, heating from 1000°C to 1210°C at a rate of 3°C / min, heating from 1210°C to 1290°C at a rate of 2°C / min, heating from 1290°C to 1300°C at a rate of 1°C / min and holding at that temperature for 2 hours. The furnace is then cooled to room temperature before the furnace is removed from the furnace.

[0215] The gradient prestressed reinforced high-pressure porcelain bushing described in step (5) consists of, from the outside to the inside, a glaze layer, a third prestressed transition layer, a second prestressed transition layer, a first prestressed transition layer, a porcelain bushing, a first prestressed transition layer, a second prestressed transition layer, a third prestressed transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Example 3, measured using the single-sided notched beam method, has a fracture toughness of 9.5 MPa·m. 1 / 2 .

[0216] Comparative Example 1

[0217] The preparation method of the gradient prestressed reinforced high-pressure porcelain bushing described in Comparative Example 1 is the same as that in Example 1, except that the first, second, and third prestressed transition layers are not set. That is, the structure of the gradient prestressed reinforced high-pressure porcelain bushing prepared in Comparative Example 1 is a glaze layer, a porcelain bushing, and a glaze layer. The high-pressure porcelain bushing prepared in Comparative Example 1 has a fracture toughness of 7.3 MPa·m measured by the single-sided notched beam method. 1 / 2 .

[0218] Comparative Example 2

[0219] The preparation method of the gradient prestressed reinforced high-pressure porcelain bushing described in Comparative Example 2 is the same as that in Example 1, except that the first prestressing transition layer is not set. That is, the gradient prestressed reinforced high-pressure porcelain bushing prepared in Comparative Example 2 consists of, from the outside to the inside, a glaze layer, a third prestressing transition layer, a second prestressing transition layer, a porcelain bushing green, a second prestressing transition layer, a third prestressing transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Comparative Example 2 has a fracture toughness of 8.1 MPa·m measured by the single-sided notched beam method. 1 / 2 .

[0220] Comparative Example 3

[0221] The preparation method of the gradient prestressed reinforced high-pressure porcelain bushing described in Comparative Example 3 is the same as that in Example 1, except that a second prestressing transition layer is not provided. That is, the gradient prestressed reinforced high-pressure porcelain bushing prepared in Comparative Example 3 consists of, from the outside to the inside, a glaze layer, a third prestressing transition layer, a first prestressing transition layer, a porcelain bushing green, a first prestressing transition layer, a third prestressing transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Comparative Example 3 has a fracture toughness of 8.3 MPa·m measured using the single-sided notched beam method. 1 / 2 .

[0222] Comparative Example 4

[0223] The preparation method of the gradient prestressed reinforced high-pressure porcelain bushing described in Comparative Example 4 is the same as that in Example 1, except that a third prestressing transition layer is not provided. That is, the gradient prestressed reinforced high-pressure porcelain bushing prepared in Comparative Example 4 consists of, from the outside to the inside, a glaze layer, a second prestressing transition layer, a first prestressing transition layer, a porcelain bushing green, a first prestressing transition layer, a second prestressing transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Comparative Example 4 has a fracture toughness of 8.0 MPa·m measured using the single-sided notched beam method. 1 / 2 .

[0224] Comparative Example 5

[0225] The preparation method of the gradient prestressed reinforced high-pressure porcelain bushing described in Comparative Example 5 is the same as that in Example 1, except that the raw materials for preparing the first and third prestressed transition layers remain the same, but the positions of the first and third prestressed transition layers are interchanged. That is, the gradient prestressed reinforced high-pressure porcelain bushing prepared in Comparative Example 5 consists of, from the outside to the inside, a glaze layer, a first prestressed transition layer, a second prestressed transition layer, a third prestressed transition layer, a porcelain bushing blank, a third prestressed transition layer, a second prestressed transition layer, a first prestressed transition layer, and a glaze layer. The high-pressure porcelain bushing prepared in Comparative Example 5 has a fracture toughness of 8.6 MPa·m measured using the single-sided notched beam method.1 / 2 .

[0226] By comparing Comparative Examples 1-5 with Examples 1-3, it can be seen that the fracture toughness of the high-pressure porcelain bushing prepared in Examples 1-3 is significantly better than that in Comparative Examples 1-5. In Comparative Examples 1-5, the fracture toughness of the high-pressure porcelain bushing prepared is significantly reduced due to the absence or change in the position of a certain prestressed transition layer.

[0227] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a gradient prestressed reinforced high-pressure porcelain bushing, characterized in that: It consists of the following steps: (1) Using nano-boehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid as raw materials, a mixture is prepared. The mixture is then ball-milled for 8-8.2 hours, passed through a 200-mesh sieve, spray-granulated, and then isostatically pressed to obtain a ceramic sleeve green body. (2) Mix the Molexite fine powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water evenly, and disperse them evenly by high-speed shearing and stirring. Then, use an automatic spraying equipment to form a uniform film on the inner and outer walls of the ceramic sleeve green body to form the first prestressed transition layer. Finally, dry the mixture to obtain the ceramic sleeve green body containing the first prestressed transition layer. (3) Mix halloysite, fused silica powder, defoamer, zirconium hydrogen phosphate, silica-alumina sol and deionized water evenly, and ball mill in a planetary ball mill to obtain a mixed slurry. Transfer the mixed slurry into a spraying system and spray it evenly on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer. After drying, a ceramic sleeve green blank containing the second prestressed transition layer is prepared. (4) Mix fused silica powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water evenly, and ball mill the mixture in a planetary ball mill to obtain a mixed slurry. Apply the mixture evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form the third prestressed transition layer. After drying, a ceramic sleeve green body containing the third prestressed transition layer is prepared. (5) Nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, and polyvinyl butyral are mixed in proportion, and deionized water is added to adjust the glaze slurry viscosity to 1.1-1.3 Pa·s. After planetary ball milling, a slurry is obtained. Strontium borosilicate glass powder is added to adjust the glaze slurry specific gravity to 1.35-1.45 g / cm³. 3 After being filtered through a 325-mesh sieve and aged, the material undergoes ultrasonic oscillation to prepare a glaze. The glaze is then uniformly sprayed onto both the inner and outer sides of the third prestressed transition layer using an electrostatic spraying process to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer is prepared. Finally, after sintering, a gradient prestressed reinforced high-pressure porcelain sleeve is prepared.

2. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: The ceramic sleeve green body, by mass percentage, consists of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid. In the ceramic sleeve green body, the particle size of nanoboehmite is 80nm and the particle size of kaolinite is 2μm. In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

3. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: The preparation method of zirconium silicate sol in step (1) is as follows: zirconium silicate powder is used as raw material, and zirconium silicate powder and deionized water are mixed at a mass ratio of 3:

7. Nitric acid accounting for 1-2% of the mass of zirconium silicate powder is added as a dispersant to adjust the pH value of the system to 3-4. Then, the mixture is magnetically stirred for 30 minutes for preliminary mixing, and then transferred to a ball mill jar with zirconium oxide balls as the grinding medium. The ball-to-material ratio is 5:1, and the mixture is ball-milled for 5-6 hours. Finally, the large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

4. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid mentioned in step (1) is as follows: weigh high-purity Y2O3, La2O3 and CeO2 powders in a molar ratio of 4:3:3 and mix them evenly. Press the mixed powder into a green body, and then place it in a flash furnace. Under an air atmosphere, rapidly heat it to 1550-1600℃ at a heating rate of 600℃ / min and hold it for 3-5 minutes. Then rapidly cool it to obtain a dense block. The dense block is coarsely crushed, and then high-energy ball milled for 4-6 hours in a zirconia ball mill jar with ethanol as the medium, with a ball-to-material ratio of 10:

1. Finally, it is sieved to obtain D. 50 =400-600nm composite sintering aid powder.

5. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: The total mass of the moleckite fine powder, lanthanum-zirconium composite sol, and deionized water in step (2) is 100%, wherein the moleckite fine powder is 53%-57%, the lanthanum-zirconium composite sol is 28%-32%, and the deionized water is 11%-19%. In step (2), the mass of boron nitride nanosheets accounts for 3% of the total mass of the Molexite fine powder, lanthanum-zirconium composite sol, and deionized water; In step (2), the particle size of the Molexite fine powder is 120 μm, and the particle size of the boron nitride nanosheets is 2 μm. The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: Lanthanum nitrate and zirconium oxychloride are weighed according to the molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and citric acid is added as a stabilizer at a molar amount of 1.5 times the total molar amount of metal ions. Then, the solution is added dropwise to ammonia water with pH=10 at a rate of 1 mL / min for co-precipitation reaction. After stirring for 2 hours, it is allowed to stand for 12 hours. The precipitate is centrifuged and washed until neutral, and then redispersed in deionized water. The pH of the system is adjusted to 3-4 with nitric acid. After hydrothermal reaction at 100℃ for 6 hours, it is ultrasonically treated to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

6. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: The high-speed shearing and stirring described in step (2) is to first stir at a speed of 4000 r / min for 5 min, and then stir at a speed of 2000 r / min for 20 min; In step (2), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm; In step (2), the thickness of the first prestressed transition layer on one side is precisely controlled to be 0.3-0.5 mm; The drying process described in step (2) involves first keeping the product at 80°C for 4 hours, and then keeping it at 120°C for 4 hours.

7. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: In step (3), the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol, and zirconium hydrogen phosphate is 100%, wherein halloysite accounts for 43%-47%, fused silica powder accounts for 18%-22%, deionized water accounts for 18%-22%, silica-alumina sol accounts for 7%-13%, and zirconium hydrogen phosphate accounts for 4%-6%. In step (3), the defoamer accounts for 1.5% of the total mass of halloysite, fused silica powder, deionized water, silica-alumina sol, and zirconium hydrogen phosphate. The halloysite in step (3) has a particle size of 10 μm, and the fused silica powder has a particle size of 30 μm; In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h; In step (3), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm; In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.6-0.9 mm; The drying process described in step (3) involves first drying at 80°C for 4 hours, and then keeping warm at 120°C for 4 hours.

8. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: In step (4), the total mass of fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate, and scandium-stabilized cerium-zirconium composite powder is 100%, wherein fused silica powder accounts for 63-67%, aluminum phosphate sol accounts for 13-18%, deionized water accounts for 13-22%, sodium polycarboxylate accounts for 1.2-1.8%, and scandium-stabilized cerium-zirconium composite powder accounts for 0.2-0.8%. The particle size of the fused silica powder mentioned in step (4) is 25 μm; In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h; In step (4), the atomization pressure during spraying is 0.4 MPa and the spraying distance is 12 cm. In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.4-0.6 mm; The drying conditions described in step (4) are: first, dry at 80°C for 4 hours, and then keep warm at 120°C for 4 hours.

9. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: In step (5), the total mass of nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water is 100%, of which nano-alumina accounts for 28%-32%, yttrium-stabilized zirconium oxide accounts for 23%-27%, silica sol accounts for 13%-17%, sodium polyacrylate dispersant accounts for 0.8%-1.2%, polyvinyl butyral accounts for 3.5%-4.5%, and deionized water accounts for 22.3%-27.7%. In step (5), the strontium borosilicate glass powder is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the six components: nano-alumina, yttrium-stabilized zirconium oxide, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water. In step (5), the particle size of nano alumina is 3 μm, the particle size of yttrium-stabilized zirconium oxide is 0.8 μm, the solid content of silica sol is 30%, sodium polyacrylate is liquid with a molecular weight of 8000, the particle size of polyvinyl butyral powder is 50 μm, and the particle size of strontium borosilicate glass powder is 10 μm.

10. The method for preparing a gradient prestressed reinforced high-pressure porcelain bushing according to claim 1, characterized in that: In step (5), the ball milling speed is 400 r / min and the ball milling time is 6 h; In step (5), the aging time is 24 hours and the aging temperature is room temperature; In step (5), the ultrasonic conditions are 10 minutes of ultrasonic oscillation every 2 hours; In step (5), the electrostatic spraying voltage is 50-60kV; In step (5), the thickness of the glaze layer on one side is controlled at 0.2-0.3 mm; The drying process described in step (5) involves drying in an oven at 80-100℃ for 1-2 hours to allow the glaze layer to initially solidify. The sintering process in step (5) involves heating from 100°C to 700°C at a rate of 5°C / min, then heating from 700°C to 1000°C at a rate of 4°C / min, heating from 1000°C to 1210°C at a rate of 3°C / min, heating from 1210°C to 1290°C at a rate of 2°C / min, heating from 1290°C to 1300°C at a rate of 1°C / min and holding at that temperature for 2 hours. The furnace is then cooled to room temperature before the furnace is removed from the furnace.

Images