Preparation method of gradient pre-stress reinforced high-voltage porcelain bushing

Abstract

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

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-voltage porcelain sleeve preparation, and particularly relates to a preparation method of a gradient pre-stress reinforced high-voltage porcelain sleeve. BACKGROUND

[0002] The high-voltage porcelain sleeve is a key insulating component in power equipment, and is widely used in high-voltage electrical equipment such as transformers, circuit breakers and mutual inductors, and mainly plays the roles of insulation, mechanical support and sealing. The performance of the high-voltage porcelain sleeve directly affects the safe and stable operation of the power equipment. The high-voltage porcelain sleeve is an electric porcelain product sintered at high temperature, and improper formula, insufficient purity of raw materials or unstrict process flow control (such as uneven mixing of raw materials, improper sintering temperature control, etc.) in the manufacturing process may cause pores, cracks and other defects in the porcelain piece. Due to the inherent brittleness of the electric porcelain material and the lack of plastic deformation ability, the high-voltage porcelain sleeve is subjected to mechanical stress, sudden temperature change and harsh environment (such as extreme low temperature, icing, ultraviolet aging, etc.) in long-term operation, and these factors will accelerate the expansion of internal defects, and the high-voltage porcelain sleeve is prone to brittle fracture failure.

[0003] In recent years, porcelain sleeve burst accidents frequently occur in power grids, which seriously threatens the normal operation of power equipment and the personal safety of operation and maintenance personnel. Research shows that the main failure mode of the porcelain sleeve is brittle fracture, and its inherent high brittleness, low fracture toughness and high sensitivity to cracks cause it to be prone to sudden damage during operation. Therefore, improving the fracture toughness of the porcelain sleeve becomes the key to improving its mechanical properties.

[0004] Currently, three technical solutions are mainly used in the industry to improve the mechanical properties of the porcelain sleeve: particle toughening ceramic, layered structure design and gradient functional material. Particle toughening hinders crack propagation by adding toughening particles such as ZrO2, SiC, Al2O3, TiC and Si3N4 in the matrix, but due to the high hardness and inherent brittleness of the ceramic material, the interface bonding strength between the particles and the matrix is insufficient, which easily leads to interface debonding and micro-crack initiation; in addition, the agglomeration and uneven distribution of the toughening particles will introduce new stress concentration points, which will reduce the uniformity and reliability of the material. The layered structure design uses a hard-soft alternating structure to deflect the crack path, but the interface delamination risk is caused by the difference in thermal expansion coefficient; the gradient functional material can optimize the thermal stress distribution, but the protection effect on mechanical impact is limited and the process is complex.

[0005] Therefore, it is necessary to explore a new type of gradient pre-stress reinforced high-voltage porcelain sleeve with good fracture toughness. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a gradient pre-stress reinforced high-voltage porcelain sleeve. The high-voltage porcelain sleeve prepared by the method has excellent fracture toughness.

[0007] The method for preparing the gradient prestressed reinforced high-voltage porcelain bushing of the present invention comprises the following steps: (1) Nanoboehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid are used as raw materials to obtain a mixture, the mixture is subjected to planetary ball milling 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) Molecule powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water are uniformly mixed and uniformly dispersed by high-speed shear stirring. Then, an automatic spraying device is used to uniformly form a film on the inner and outer walls of the porcelain sleeve green body to form a first prestressed transition layer. Finally, the green body of the porcelain sleeve containing the first prestressed transition layer is prepared by drying. (3) halloysite, fused quartz powder, defoaming agent, zirconium hydrogen phosphate, silica-alumina sol and deionized water are uniformly mixed, ball-milled in a planetary ball mill to obtain a mixed slurry, the mixed slurry is transferred to a spraying system, and uniformly sprayed on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer, and dried to prepare a porcelain sleeve green body containing the second prestressed transition layer; (4) Evenly mixing fused quartz powder, aluminum phosphate sol, scandium-stabilized cerium-zirconium composite powder, sodium polycarboxylate and deionized water, ball milling the mixture in a planetary ball mill to obtain a mixed slurry, and applying the mixed slurry evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form a third prestressed transition layer. After drying, a porcelain sleeve green body containing the third prestressed transition layer is prepared; (5) Nano-alumina, yttria-stabilized zirconia, silica sol, sodium polyacrylate, and polyvinyl butyral were mixed in proportion, and deionized water was added to adjust the glaze slurry viscosity to 1.1-1.3 Pa·s. The slurry was obtained after planetary ball milling, and strontium borosilicate glass powder was added to adjust the glaze slurry specific gravity to 1.35-1.45 g / cm 3 , filtered through a 325-mesh sieve and then aged, during which ultrasonic oscillation was performed to prepare a glaze, and an electrostatic spraying process was used to evenly spray the glaze on the inner and outer sides of the third prestressed transition layer to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer was prepared, and finally, after sintering, a gradient prestressed reinforced high-voltage porcelain sleeve was prepared.

[0008] in: The porcelain sleeve green body is composed of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid, calculated by mass percentage.

[0009] The particle size of the nano-boehmite in the ceramic sleeve green body is 80 nm, which is used to provide a high-activity Al2O3 precursor; the particle size of the kaolin is 2 μm, which is used as a plasticity regulator to improve the forming property; the zirconium silicate sol (solid content 30%) is used as an inorganic binder to provide a bonding strength at room temperature to medium temperature and to be converted into a reinforcing phase at high temperature; and the Y2O3-La2O3-CeO2 composite sintering aid has the overall effect of synergistically reducing the sintering temperature, optimizing the microstructure, and improving the mechanical properties, in which Y2O3 inhibits abnormal grain growth, La2O3 promotes grain boundary diffusion, and CeO2 improves the fracture toughness.

[0010] The preparation method of the zirconium silicate sol in step (1) is as follows: zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as a raw material, mixed according to a mass ratio of zirconium silicate powder to deionized water of 3:7, and 1-2% of nitric acid is added as a dispersant to adjust the pH value of the system to 3-4, then subjected to preliminary mixing by magnetic stirring for 30 min, then transferred into a ball mill tank, zirconia balls are used as grinding media, the ball-to-material ratio is 5:1, ball milling is performed for 5-6 hours, and finally large particles are removed by filtration to obtain a uniform and stable zirconium silicate sol.

[0011] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid in step (1) is as follows: high-purity Y2O3, La2O3, and CeO2 powders (purity ≥ 99.9%) are weighed according to a molar ratio of 4:3:3 and uniformly mixed, the mixed powders are pressed into a compact, then placed in a flash firing furnace, rapidly heated to 1550-1600°C at an air atmosphere and a heating rate of 600°C / min, and kept for 3-5 min, then rapidly cooled to obtain a densified block; the densified block is roughly broken, then subjected to high-energy ball milling in a zirconia ball mill tank with ethanol as a medium, the ball-to-material ratio is 10:1, and finally sieved to obtain a composite sintering aid powder with D 50 = 400-600 nm.

[0012] The forming pressure in step (1) is 150 MPa, and the pressure holding time is 4 min.

[0013] The manufacturer of the nano-boehmite in step (1) is Shandong Guocai Functional Materials Co., Ltd.

[0014] In step (2), the mass ratio of the mullite fine powder, the lanthanum-zirconium composite sol, and the deionized water is 100%, in which the mullite fine powder accounts for 53%-57%, the lanthanum-zirconium composite sol accounts for 28%-32%, and the deionized water accounts for 11%-19%.

[0015] In step (2), the mass of the boron nitride nanosheet accounts for 3% of the total mass of the mullite fine powder, the lanthanum-zirconium composite sol, and the deionized water.

[0016] The particle size of the mullite fine powder in step (2) is 120 μm, and the particle size of the boron nitride nanosheet is 2 μm.

[0017] The manufacturer of the mullite fine powder in step (2) is Inge Ceramics (Tianjin) New Material Technology Co., Ltd., the content of the mullite phase is 55%, the content of the glass phase is 45%, and the manufacturer of the boron nitride nanosheet is Suzhou Napo Material Technology Co., Ltd.

[0018] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: lanthanum nitrate and zirconium oxychloride are weighed according to a molar ratio of La:Zr=1:9, dissolved in deionized water to prepare a mixed solution with a concentration of 0.5 mol / L, and 1.5 times the molar amount of citric acid relative to the total molar amount of metal ions is added as a stabilizer, then the solution is added dropwise into ammonia water with a pH of 10 at a speed of 1 mL / min for a co-precipitation reaction, stirring is continued for 2 hours, and then the obtained precipitate is centrifuged and washed to neutral, and then dispersed in deionized water, and the pH of the system is adjusted to 3-4 with nitric acid, and then the system is subjected to hydrothermal reaction at 100°C for 6 hours and ultrasonic treatment, to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0019] The high-speed shearing stirring in step (2) is first stirred at a speed of 4000 r / min for 5 min, and then stirred at a speed of 2000 r / min for 20 min.

[0020] The atomization pressure during spraying in step (2) is 0.4 MPa, and the spraying distance is 12 cm.

[0021] The thickness of the single-sided first pre-stress transition layer in step (2) is accurately controlled to be 0.3-0.5 mm.

[0022] The drying in step (2) is first carried out at 80°C for 4 h, and then carried out at 120°C for 4 h.

[0023] In the first pre-stress transition layer in step (2), the mullite fine powder is used as the matrix material, the mullite phase provides high-temperature stability and mechanical strength, and the glass phase promotes sintering densification; the boron nitride nanosheet improves the thermal conductivity of the material by virtue of its two-dimensional sheet, and also introduces beneficial compressive pre-stress in the matrix through its low thermal expansion characteristic; the lanthanum-zirconium composite sol serves as a key bonding phase, forms a three-dimensional network structure to provide initial strength during the drying stage, and is converted into La2Zr2O7 pyrochlore phase at high temperature to realize the gradient transition of the thermal expansion coefficient, and the grain boundary segregation effect of La 3+ effectively inhibits abnormal grain growth.

[0024] The mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate in step (3) is 100%, wherein the halloysite accounts for 43-47%, the fused quartz powder accounts for 18-22%, the deionized water accounts for 18-22%, the silicon-aluminum sol accounts for 7-13%, and the zirconium hydrogen phosphate accounts for 4-6%.

[0025] The mass of the defoaming agent in step (3) accounts for 1.5% of the total mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate.

[0026] The particle size of the halloysite in step (3) is 10 μm, and the particle size of the fused quartz powder is 30 μm.

[0027] The ball milling speed in step (3) is 400 r / min, and the ball milling time is 4 h.

[0028] The atomization pressure during spraying in step (3) is 0.4 MPa, and the spraying distance is 12 cm.

[0029] The thickness of the single-sided second pre-stress transition layer in step (3) is accurately controlled to be 0.6-0.9 mm.

[0030] The drying in step (3) is first dried at 80℃ for 4 h, and then incubated at 120℃ for 4 h.

[0031] The defoaming agent in step (3) is a high-temperature-resistant defoaming agent, the production manufacturer of the high-temperature-resistant defoaming agent is Anhui Aiyouta Silicone Co., Ltd., and the model is IOTA 3038-15; the production manufacturer of the zirconium hydrogen phosphate is Shanghai Maikelin Biochemical Technology Co., Ltd., and the production manufacturer of the silicon-aluminum sol is Suzhou Nadi Microelectronics Co., Ltd.

[0032] In the second pre-stress transition layer in step (3), the halloysite provides structural support, enhances mechanical strength and thermal stability, the fused quartz powder adjusts the thermal expansion coefficient, the zirconium hydrogen phosphate acts as a high-temperature binder to promote the formation of stable phosphate bonds during the sintering process and improve the interlayer bonding strength, the silicon-aluminum sol provides nano-sized silicon-aluminum oxide particles to improve the slurry dispersibility and enhance the interface bonding after high-temperature sintering, and the high-temperature-resistant defoaming agent eliminates the bubbles in the slurry, prevents pores or cracks from appearing after the coating is dried, and improves the compactness.

[0033] The mass of the fused quartz powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder in step (4) is 100%, wherein the fused quartz powder accounts for 63-67%, the aluminum phosphate sol accounts for 13-18%, the deionized water accounts for 13-22%, the sodium polycarboxylate accounts for 1.2-1.8%, and the scandium-stabilized cerium-zirconium composite powder accounts for 0.2-0.8%.

[0034] The particle size of the fused quartz powder in step (4) is 25 μm.

[0035] The manufacturer of the aluminum phosphate sol in step (4) is Wuhan Jiyue Shenghua Chemical Co., Ltd., the solid content of the aluminum phosphate sol is 40%, the manufacturer of the scandium-stabilized cerium-zirconium composite powder is Hunan Rare Metal Material Research Institute Co., Ltd., and the manufacturer of the sodium polycarboxylate dispersant is Kedeli Chemical Technology Co., Ltd., and the model is SAMASO DP5045.

[0036] The ball milling speed in step (4) is 400 r / min, and the ball milling time is 4 h.

[0037] The atomization pressure during spraying in step (4) is 0.4 MPa, and the spraying distance is 12 cm.

[0038] The thickness of the single-sided third pre-stressed transition layer in step (4) is accurately controlled to be 0.4-0.6 mm.

[0039] The drying conditions in step (4) are first drying at 80℃ for 4 h, and then incubating at 120℃ for 4 h.

[0040] In the third pre-stressed transition layer in step (4), the fused quartz powder serves as a filler, which plays a role in reducing the thermal expansion coefficient and enhancing the high-temperature stability, the aluminum phosphate sol serves as a binder, which plays a role in high-temperature bonding and promoting sintering, the sodium polycarboxylate dispersant plays a role in improving the dispersibility of the slurry and preventing particle agglomeration, and the scandium-stabilized cerium-zirconium composite powder plays a role in improving the material density and enhancing the fracture toughness.

[0041] The mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water in step (5) is 100%, wherein the nano-alumina accounts for 28%-32%, the yttrium-stabilized zirconia accounts for 23%-27%, the silica sol accounts for 13%-17%, the sodium polyacrylate dispersant accounts for 0.8%-1.2%, the polyvinyl butyral accounts for 3.5%-4.5%, and the deionized water accounts for 22.3%-27.7%.

[0042] The strontium borosilicate glass powder in step (5) serves as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0043] The manufacturer of the strontium borosilicate glass powder in step (5) is Suzhou Qiuyi New Material Co., Ltd.

[0044] The particle size of the nano-alumina in step (5) is 3 microns, the particle size of the yttria-stabilized zirconia is 0.8 microns, the solid content of the silica sol is 30%, the polyacrylic acid sodium is in liquid form, the molecular weight is 8000, the particle size of the polyvinyl butyral powder is 50 microns, and the particle size of the strontium borosilicate glass powder is 10 microns.

[0045] In step (5), when the glaze is prepared, the nano-alumina serves to improve the hardness and wear resistance of the glaze layer, the yttria-stabilized zirconia powder serves to enhance the toughness and thermal shock resistance of the glaze layer, the polyvinyl butyral serves as an organic binder to improve the forming performance of the glaze, the strontium borosilicate glass powder serves to reduce the melting temperature of the glaze and promote the densification of the glaze layer, and the silica sol serves to improve the dispersion stability of the glaze and form a silicon-oxygen network to enhance the adhesion during sintering.

[0046] In step (5), the ball milling speed is 400 r / min, and the ball milling time is 6 hours.

[0047] In step (5), the aging time is 24 hours, and the aging temperature is room temperature.

[0048] In step (5), the ultrasonic wave condition is 10 minutes of ultrasonic vibration every 2 hours.

[0049] In step (5), the electrostatic spraying process has a spraying voltage of 50-60 kV.

[0050] In step (5), the thickness of the single-sided glaze layer is controlled to be 0.2-0.3 mm.

[0051] In step (5), the drying treatment is drying in an oven at 80-100℃ for 1-2 hours to preliminarily solidify the glaze layer.

[0052] In step (5), the sintering is performed at a heating rate of 5℃ / min from 100℃ to 700℃, then at a rate of 4℃ / min from 700℃ to 1000℃, at a rate of 3℃ / min from 1000℃ to 1210℃, at a rate of 2℃ / min from 1210℃ to 1290℃, at a rate of 1℃ / min from 1290℃ to 1300℃, and the temperature is maintained for 2 hours, then the furnace is cooled to room temperature, and the product is taken out of the furnace.

[0053] In step (5), the gradient pre-stress reinforced high-pressure porcelain sleeve is composed of, from the outside to the inside, a glaze layer, a third pre-stress transition layer, a second pre-stress transition layer, a first pre-stress transition layer, a porcelain sleeve green body, a first pre-stress transition layer, a second pre-stress transition layer, a third pre-stress transition layer, and a glaze layer.

[0054] Compared with the prior art, the present application has the following beneficial effects: (1) The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the application designs a gradient structure multi-stage prestress reinforced layer, optimizes the material ratio and process parameters of each prestress transition layer, forms a synergistic strengthening effect between different layers, and enhances the toughness of the high-voltage porcelain sleeve.

[0055] (2) The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the application forms a gradual stress transition between the green porcelain sleeve and the external reinforced layer through the optimization design of the gradient prestress layer, effectively inhibits crack propagation, significantly improves the fracture toughness and impact resistance of the high-voltage porcelain sleeve, and enables the high-voltage porcelain sleeve to maintain excellent mechanical stability under complex working conditions.

[0056] (3) The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the application simultaneously introduces a multi-stage prestress layer composed of a mullite prestress layer (a first prestress transition layer), an EPI and fused quartz powder prestress layer (a second prestress transition layer), and a fused quartz powder prestress layer (a third prestress transition layer), forms a gradient structure prestress layer reinforced porcelain sleeve, forms a good bonding interface between the strong and tough layer and the green porcelain sleeve, and the crack propagation process is beneficial to the consumption of strain energy, thereby improving the toughness. The multi-stage strong and tough layer formed can effectively protect the green porcelain sleeve during the sudden fracture of the high-voltage porcelain sleeve.

[0057] (4) The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the application is a thermal expansion coefficient gradient control method, that is, the thermal expansion coefficient of the green porcelain sleeve layer > the thermal expansion coefficient of the first prestress transition layer > the thermal expansion coefficient of the second prestress transition layer > the thermal expansion coefficient of the third prestress transition layer, the symmetric structure design and the gradient distribution characteristics of the residual compressive stress field ensure the uniformity of stress transition and avoid delamination or stress concentration. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The figure is a structural schematic diagram of the gradient prestress reinforced high-voltage porcelain sleeve. In the figure, 1 is a green porcelain sleeve; 2 is a first prestress transition layer; 3 is a second prestress transition layer; 4 is a third prestress transition layer; and 5 is a glaze layer. DETAILED DESCRIPTION

[0059] Example 1 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the application comprises the following steps: (1) Nanometer boehmite, lithium silicate, kaolin, zirconium silicate sol, and Y2O3-La2O3-CeO2 composite sintering agent are used as raw materials to obtain a mixture. The mixture is mixed and sprayed after being milled on a planetary ball mill for 8.1 hours and passing through a 200-mesh screen, and then is formed by isostatic pressing to obtain a green porcelain sleeve. (2) Molecule powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water are uniformly mixed and uniformly dispersed by high-speed shear stirring. Then, an automatic spraying device is used to uniformly form a film on the inner and outer walls of the porcelain sleeve green body to form a first prestressed transition layer. Finally, the green body of the porcelain sleeve containing the first prestressed transition layer is prepared by drying. (3) halloysite, fused quartz powder, defoaming agent, zirconium hydrogen phosphate, silica-alumina sol and deionized water are uniformly mixed, ball-milled in a planetary ball mill to obtain a mixed slurry, the mixed slurry is transferred to a spraying system, and uniformly sprayed on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer, and dried to prepare a porcelain sleeve green body containing the second prestressed transition layer; (4) Evenly mixing fused quartz powder, aluminum phosphate sol, scandium-stabilized cerium-zirconium composite powder, sodium polycarboxylate and deionized water, ball milling the mixture in a planetary ball mill to obtain a mixed slurry, and applying the mixed slurry evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form a third prestressed transition layer. After drying, a porcelain sleeve green body containing the third prestressed transition layer is prepared; (5) Nano-alumina, yttria-stabilized zirconia, silica sol, sodium polyacrylate, and polyvinyl butyral were mixed in proportion, and deionized water was added to adjust the glaze slurry viscosity to 1.2 Pa·s. The slurry was obtained after planetary ball milling, and strontium borosilicate glass powder was added to prepare the glaze slurry with a specific gravity of 1.40 g / cm 3 , filtered through a 325-mesh sieve and then aged, during which ultrasonic oscillation was performed to prepare a glaze, and an electrostatic spraying process was used to evenly spray the glaze on the inner and outer sides of the third prestressed transition layer to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer was prepared, and finally, after sintering, a gradient prestressed reinforced high-voltage porcelain sleeve was prepared.

[0060] in: The porcelain sleeve green body is composed of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid, calculated by mass percentage.

[0061] In the porcelain sleeve green body, the particle size of nano-boehmite is 80 nm, and the particle size of kaolin is 2 μm.

[0062] The preparation method of the zirconium silicate sol described in step (1) is as follows: using zirconium silicate powder produced by Bengbu Zhongheng New Materials Technology Co., Ltd. as raw material, mixing zirconium silicate powder and deionized water in a mass ratio of 3:7, adding nitric acid accounting for 1.5% of the mass of the zirconium silicate powder as a dispersant to adjust the pH value of the system to 3.5, then magnetically stirring for 30 minutes for preliminary mixing, and then transferring the mixture into a ball mill using zirconium oxide balls as grinding media with a ball-to-material ratio of 5:1, ball milling for 5.5 hours, and finally filtering to remove large particles to obtain a uniform and stable zirconium silicate sol.

[0063] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid in step (1) is as follows: high-purity Y2O3, La2O3 and CeO2 powders (purity ≥ 99.9%) are weighed according to a molar ratio of 4:3:3 and uniformly mixed, the mixed powders are pressed into a green body, and then the green body is placed in a flash firing furnace, rapidly heated to 1575℃ at a heating rate of 600℃ / min under an air atmosphere, and then rapidly cooled to obtain a densified block; the densified block is coarsely broken, then a zirconia ball mill jar is used with ethanol as a medium, high-energy ball milling is performed for 5 hours, the ball-to-material ratio is 10:1, and finally sieving is performed to obtain a composite sintering aid powder with a particle size of D50=500nm. 50

[0064] The forming pressure in step (1) is 150MPa, and the pressure holding time is 4min.

[0065] The manufacturer of the nanometer boehmite in step (1) is Shandong Guocai Functional Materials Co., Ltd.

[0066] In step (2), the mass ratio of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water is 100%, wherein the mass ratio of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water is 55%, 30% and 15%, respectively.

[0067] In step (2), the mass of the boron nitride nanosheet accounts for 3% of the total mass of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water.

[0068] In step (2), the particle size of the mullite fine powder is 120μm, and the particle size of the boron nitride nanosheet is 2μm.

[0069] In step (2), the manufacturer of the mullite fine powder is Inge Ceramics (Tianjin) New Material Technology Co., Ltd., the content of the mullite phase is 55%, the content of the glass phase is 45%, and the manufacturer of the boron nitride nanosheet is Suzhou Napo Material Technology Co., Ltd.

[0070] In step (2), the preparation method of the lanthanum-zirconium composite sol is as follows: lanthanum nitrate and zirconium oxychloride are weighed according to a molar ratio of La:Zr=1:9, dissolved in deionized water to prepare a mixed solution with a concentration of 0.5mol / L, and 1.5 times the molar amount of citric acid relative to the total molar amount of metal ions is added as a stabilizer, then the solution is added dropwise to ammonia water with a pH of 10 at a rate of 1mL / min for a co-precipitation reaction, stirring is continued for 2 hours, then the obtained precipitate is centrifuged and washed to neutral, then it is re-dispersed in deionized water, the pH of the system is adjusted to 3.5 with nitric acid, and then the system is subjected to hydrothermal reaction at 100℃ for 6 hours and ultrasonic treatment, finally a lanthanum-zirconium composite sol with a solid content of 25% is obtained.

[0071] ​The high-speed shearing stirring in step (2) is first stirred at a rotating speed of 4000 r / min for 5 min, and then stirred at a rotating speed of 2000 r / min for 20 min.

[0072] The atomization pressure is 0.4 MPa and the spraying distance is 12 cm in the spraying in step (2).

[0073] The thickness of the single-sided first pre-stress transition layer is accurately controlled to be 0.4 mm in step (2).

[0074] The drying in step (2) is first dried at 80 ℃ for 4 h, and then dried at 120 ℃ for 4 h.

[0075] The mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate is 100% in step (3), wherein the halloysite accounts for 45%, the fused quartz powder accounts for 20%, the deionized water accounts for 21%, the silicon-aluminum sol accounts for 9%, and the zirconium hydrogen phosphate accounts for 5%.

[0076] The mass of the defoaming agent accounts for 1.5% of the total mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate in step (3).

[0077] The particle size of the halloysite is 10 μm and the particle size of the fused quartz powder is 30 μm in step (3).

[0078] The ball milling rotating speed is 400 r / min and the ball milling time is 4 h in step (3).

[0079] The atomization pressure is 0.4 MPa and the spraying distance is 12 cm in the spraying in step (3).

[0080] The thickness of the single-sided second pre-stress transition layer is accurately controlled to be 0.8 mm in step (3).

[0081] The drying in step (3) is first dried at 80 ℃ for 4 h, and then dried at 120 ℃ for 4 h.

[0082] The defoaming agent in step (3) is a high-temperature-resistant defoaming agent, the production manufacturer of the high-temperature-resistant defoaming agent is Anhui Aiyouta Silicone Co., Ltd., and the model is IOTA 3038-15; the production manufacturer of the zirconium hydrogen phosphate is Shanghai Maikelin Biochemical Technology Co., Ltd., and the production manufacturer of the silicon-aluminum sol is Suzhou Nadi Microelectronics Co., Ltd.

[0083] The mass of the fused quartz powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100% in step (4), wherein the fused quartz powder accounts for 65%, the aluminum phosphate sol accounts for 15%, the deionized water accounts for 18%, the sodium polycarboxylate accounts for 1.6%, and the scandium-stabilized cerium-zirconium composite powder accounts for 0.4%.

[0084] The particle size of the fused quartz powder in step (4) is 25 μm.

[0085] The manufacturer of the aluminum phosphate sol in step (4) is Wuhan Jiyue Shenghua Chemical Co., Ltd., the solid content of the aluminum phosphate sol is 40%, the manufacturer of the scandium-stabilized cerium-zirconium composite powder is Hunan Rare Metal Material Research Institute Co., Ltd., and the manufacturer of the sodium salt type polycarboxylic acid dispersant is Kedeli Chemical Technology Co., Ltd., and the model is SAMASO DP5045.

[0086] The ball milling speed in step (4) is 400 r / min, and the ball milling time is 4 h.

[0087] The atomization pressure during spraying in step (4) is 0.4 MPa, and the spraying distance is 12 cm.

[0088] The thickness of the single-sided third pre-stress transition layer in step (4) is accurately controlled to be 0.5 mm.

[0089] The drying condition in step (4) is first drying at 80℃ for 4 h, and then incubating at 120℃ for 4 h.

[0090] The mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water in step (5) is 100%, wherein the nano-alumina accounts for 30%, the yttrium-stabilized zirconia accounts for 25%, the silica sol accounts for 15%, the sodium polyacrylate dispersant accounts for 1.0%, the polyvinyl butyral accounts for 4.0%, and the deionized water accounts for 25%.

[0091] The strontium borosilicate glass powder in step (5) is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral, and deionized water.

[0092] The manufacturer of the strontium borosilicate glass powder in step (5) is Suzhou Qiuyi New Material Co., Ltd.

[0093] The particle size of the nano-alumina in step (5) is 3 μm, the particle size of the yttrium-stabilized zirconia is 0.8 μm, the solid content of the silica sol is 30%, the sodium polyacrylate is a liquid type with a molecular weight of 8000, the particle size of the polyvinyl butyral powder is 50 μm, and the particle size of the strontium borosilicate glass powder is 10 μm.

[0094] The ball milling speed in step (5) is 400 r / min, and the ball milling time is 6 h.

[0095] The aging time in step (5) is 24 h, and the aging temperature is room temperature.

[0096] The ultrasonic condition in step (5) is 10 min of ultrasonic vibration every 2 h.

[0097] The electrostatic spraying process in step (5) has a spraying voltage of 55 kV.

[0098] The single-side glaze layer thickness in step (5) is controlled at 0.25 mm.

[0099] The drying treatment in step (5) is drying in an oven at 90℃ for 1.5 h to preliminarily solidify the glaze layer.

[0100] The sintering in step (5) is heating from 100℃ to 700℃ at a heating rate of 5℃ / min, then heating from 700℃ to 1000℃ at a rate of 4℃ / min, heating from 1000℃ to 1210℃ at a rate of 3℃ / min, heating from 1210℃ to 1290℃ at a rate of 2℃ / min, heating from 1290℃ to 1300℃ at a rate of 1℃ / min and keeping the temperature for 2 h, and then furnace cooling to room temperature and discharging.

[0101] The gradient pre-stress reinforced high-voltage porcelain sleeve in step (5) has, from outside to inside, a glaze layer, a third pre-stress transition layer, a second pre-stress transition layer, a first pre-stress transition layer, a porcelain sleeve green body, a first pre-stress transition layer, a second pre-stress transition layer, a third pre-stress transition layer, and a glaze layer. The high-voltage porcelain sleeve prepared in this embodiment 1 has a fracture toughness of 10.2 MPa·m 1 / 2 .

[0102] Embodiment 2 The preparation method of the gradient pre-stress reinforced high-voltage porcelain sleeve in this embodiment 2 is composed of the following steps: (1) Nanometer boehmite, lithium silicate, kaolin, zirconium silicate sol, and Y2O3-La2O3-CeO2 composite sintering agent are mixed to obtain a mixed material. The mixed material is ball milled in a planetary ball mill for 8 hours, sieved through a 200-mesh screen, and then spray granulated. Then, the mixed material is isostatically pressed to prepare a porcelain sleeve green body; (2) Molybdate fine powder, boron nitride nanosheet, lanthanum-zirconium composite sol, and deionized water are mixed uniformly and uniformly dispersed by high-speed shearing stirring. Then, an automatic spraying equipment is used to uniformly form a film on the inner and outer walls of the porcelain sleeve green body to form a first pre-stress transition layer. Finally, the porcelain sleeve green body containing the first pre-stress transition layer is prepared by drying; (3) Halloysite, fused quartz powder, defoaming agent, zirconium hydrogen phosphate, silicon-aluminum sol, and deionized water are mixed uniformly and ball milled in a planetary ball mill to obtain a mixed slurry. The mixed slurry is transferred to a spraying system and uniformly sprayed on the inner and outer surfaces of the first pre-stress transition layer to form a second pre-stress transition layer. The porcelain sleeve green body containing the second pre-stress transition layer is prepared by drying treatment; (4) The fused quartz powder, aluminum phosphate sol, scandium stabilized cerium zirconium composite powder, sodium polycarboxylate and deionized water are mixed uniformly, the mixed material is ball milled in a planetary ball mill to obtain a mixed slurry, the mixed slurry is uniformly applied to the inner and outer surfaces of the second prestressed transition layer by using a spraying system, a third prestressed transition layer is formed, and a porcelain bushing green body containing the third prestressed transition layer is prepared after drying treatment. (5) The nano-alumina, yttria-stabilized zirconia, silica sol, sodium polyacrylate and polyvinyl butyral are mixed in proportion, deionized water is added to adjust the glaze slurry viscosity to 1.1 Pa·s, the slurry is obtained after planetary ball milling, strontium borosilicate glass powder is added to adjust the glaze slurry specific gravity to 1.35 g / cm 3 , after filtering through a 325 mesh screen, aging, and ultrasonic oscillation during the period, a glaze is prepared, the glaze is uniformly sprayed on the inner and outer sides of the third prestressed transition layer by using an electrostatic spraying process, a glaze layer is formed, and a porcelain bushing with a sprayed glaze layer is prepared after drying treatment, and finally a gradient prestressed reinforced high-pressure porcelain bushing is prepared after sintering.

[0103] Among them: The porcelain bushing green body is composed of 75% nanometer boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol and 4% Y2O3-La2O3-CeO2 composite sintering agent, by mass percent.

[0104] In the porcelain bushing green body, the particle size of nanometer boehmite is 80 nm, and the particle size of kaolin is 2 μm.

[0105] The preparation method of the zirconium silicate sol in step (1) is as follows: the zirconium silicate powder produced by Bengbu Zhongheng New Material Technology Co., Ltd. is used as raw material, the mass ratio of zirconium silicate powder to deionized water is 3:7, 2% nitric acid is added as dispersant to adjust the pH value of the system to 3, then magnetic stirring is carried out for 30 min for preliminary mixing, then it is transferred into a ball mill tank, zirconia balls are used as grinding medium, the ball-to-material ratio is 5:1, ball milling is carried out for 5 hours, and finally large particles are removed by filtration to obtain uniform and stable zirconium silicate sol.

[0106] The preparation method of the Y2O3-La2O3-CeO2 composite sintering agent in step (1) is as follows: high-purity Y2O3, La2O3 and CeO2 powders (purity ≥ 99.9%) are weighed according to a molar ratio of 4:3:3 and mixed uniformly, the mixed powder is pressed into a green body, then the green body is placed in a flash firing furnace, rapidly heated to 1550℃ at a heating rate of 600℃ / min in air atmosphere and kept for 5 min, then rapidly cooled to obtain a densified block; the densified block is roughly broken, then high-energy ball milling is carried out in a zirconia ball mill tank with ethanol as medium for 4 hours, the ball-to-material ratio is 10:1, and finally the composite sintering agent powder with D 50 =600 nm is obtained by sieving.

[0107] The forming pressure in step (1) is 150 MPa, and the pressure maintaining time is 4 min.

[0108] The manufacturer of the nanometer boehmite in step (1) is Shandong Guocui Functional Material Co., Ltd.

[0109] In step (2), the mass ratio of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water is 100%, wherein the mullite fine powder is 53%, the lanthanum-zirconium composite sol is 28%, and the deionized water is 19%.

[0110] In step (2), the mass of the boron nitride nanosheet accounts for 3% of the total mass of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water.

[0111] In step (2), the particle size of the mullite fine powder is 120 μm, and the particle size of the boron nitride nanosheet is 2 μm.

[0112] In step (2), the manufacturer of the mullite fine powder is Inge Ceramics (Tianjin) New Material Technology Co., Ltd., the content of the mullite phase is 55%, the content of the glass phase is 45%, and the manufacturer of the boron nitride nanosheet is Suzhou Napo Material Technology Co., Ltd.

[0113] In step (2), the preparation method of the lanthanum-zirconium composite sol is as follows: lanthanum nitrate and zirconium oxychloride are weighed according to a molar ratio of La:Zr=1:9, dissolved in deionized water to prepare a mixed solution with a concentration of 0.5 mol / L, and 1.5 times the molar amount of citric acid relative to the total molar amount of metal ions is added as a stabilizer, then the solution is added dropwise into ammonia water with a pH of 10 at a speed of 1 mL / min for a co-precipitation reaction, and after continuous stirring for 2 hours, the obtained precipitate is centrifuged and washed to neutral, and then dispersed in deionized water again, and the pH of the system is adjusted to 4 with nitric acid, and then the system is subjected to hydrothermal reaction at 100°C for 6 hours and ultrasonic treatment, to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

[0114] In step (2), the high-speed shearing stirring is first stirred at a speed of 4000 r / min for 5 min, and then stirred at a speed of 2000 r / min for 20 min.

[0115] In step (2), the atomization pressure during spraying is 0.4 MPa, and the spraying distance is 12 cm.

[0116] In step (2), the thickness of the single-sided first pre-stress transition layer is accurately controlled to be 0.5 mm.

[0117] In step (2), the drying is first carried out at 80°C for 4 h, and then carried out at 120°C for 4 h.

[0118] The mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate in step (3) is 100%, wherein the halloysite accounts for 43%, the fused quartz powder accounts for 22%, the deionized water accounts for 18%, the silicon-aluminum sol accounts for 13%, and the zirconium hydrogen phosphate accounts for 4%.

[0119] The mass of the defoaming agent in step (3) accounts for 1.5% of the total mass of the halloysite, fused quartz powder, deionized water, silicon-aluminum sol and zirconium hydrogen phosphate.

[0120] The particle size of the halloysite in step (3) is 10 μm, and the particle size of the fused quartz powder is 30 μm.

[0121] The ball milling speed in step (3) is 400 r / min, and the ball milling time is 4 h.

[0122] The atomization pressure during spraying in step (3) is 0.4 MPa, and the spraying distance is 12 cm.

[0123] The thickness of the single-sided second pre-stress transition layer in step (3) is accurately controlled to be 0.9 mm.

[0124] The drying in step (3) is first dried at 80℃ for 4 h, and then incubated at 120℃ for 4 h.

[0125] The defoaming agent in step (3) is a high-temperature-resistant defoaming agent, the production manufacturer of the high-temperature-resistant defoaming agent is Anhui Aiyouta Silicone Co., Ltd., the model is IOTA 3038-15, the production manufacturer of the zirconium hydrogen phosphate is Shanghai Maikelin Biochemical Technology Co., Ltd., and the production manufacturer of the silicon-aluminum sol is Suzhou Nadi Microelectronics Co., Ltd.

[0126] The mass of the fused quartz powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder in step (4) is 100%, wherein the fused quartz powder accounts for 63%, the aluminum phosphate sol accounts for 13%, the deionized water accounts for 22%, the sodium polycarboxylate accounts for 1.2%, and the scandium-stabilized cerium-zirconium composite powder accounts for 0.8%.

[0127] The particle size of the fused quartz powder in step (4) is 25 μm.

[0128] The production manufacturer of the aluminum phosphate sol in step (4) is Wuhan Jiyue Sheng Chemical Co., Ltd., the solid content of the aluminum phosphate sol is 40%, the production manufacturer of the scandium-stabilized cerium-zirconium composite powder is Hunan Rare Metal Material Research Institute Co., Ltd., and the production manufacturer of the sodium polycarboxylate type dispersant is Kedeli Chemical Technology Co., Ltd., the model is SAMASO DP5045.

[0129] The ball milling speed in step (4) is 400 r / min, and the ball milling time is 4 h.

[0130] The atomizing pressure in the spraying in step (4) is 0.4 MPa, and the spraying distance is 12 cm.

[0131] The thickness of the single-sided third pre-stress transition layer is precisely controlled to be 0.6 mm in step (4).

[0132] The drying condition in step (4) is first drying at 80℃ for 4 h, and then keeping at 120℃ for 4 h.

[0133] The mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral and deionized water in step (5) is 100%, wherein the nano-alumina accounts for 28%, the yttrium-stabilized zirconia accounts for 27%, the silica sol accounts for 13%, the sodium polyacrylate dispersant accounts for 0.8%, the polyvinyl butyral accounts for 3.5%, and the deionized water accounts for 27.7%.

[0134] The strontium borosilicate glass powder in step (5) is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral and deionized water.

[0135] The manufacturer of the strontium borosilicate glass powder in step (5) is Suzhou Qiuyi New Material Co., Ltd.

[0136] The particle size of the nano-alumina in step (5) is 3 μm, the particle size of the yttrium-stabilized zirconia is 0.8 μm, the solid content of the silica sol is 30%, the sodium polyacrylate is a liquid type with a molecular weight of 8000, the particle size of the polyvinyl butyral powder is 50 μm, and the particle size of the strontium borosilicate glass powder is 10 μm.

[0137] The ball milling speed in step (5) is 400 r / min, and the ball milling time is 6 h.

[0138] The aging time in step (5) is 24 h, and the aging temperature is room temperature.

[0139] The ultrasonic condition in step (5) is 10 min of ultrasonic vibration every 2 h.

[0140] The spraying voltage of the electrostatic spraying process in step (5) is 50 kV.

[0141] The thickness of the single-sided glaze layer is controlled to be 0.3 mm in step (5).

[0142] The drying treatment in step (5) is drying in an oven at 80℃ for 2 h to preliminarily solidify the glaze layer.

[0143] The sintering in step (5) is performed at a temperature increasing rate of 5℃ / min from 100℃ to 700℃, then at a rate of 4℃ / min from 700℃ to 1000℃, at a rate of 3℃ / min from 1000℃ to 1210℃, at a rate of 2℃ / min from 1210℃ to 1290℃, at a rate of 1℃ / min from 1290℃ to 1300℃ for 2h, and then the furnace is cooled to room temperature before the furnace is discharged.

[0144] The gradient pre-stress reinforced high-voltage porcelain sleeve in step (5) is composed of, from the outside to the inside, a glaze layer, a third pre-stress transition layer, a second pre-stress transition layer, a first pre-stress transition layer, a porcelain sleeve green body, a first pre-stress transition layer, a second pre-stress transition layer, a third pre-stress transition layer, and a glaze layer. The high-voltage porcelain sleeve prepared in this embodiment 2 has a fracture toughness of 9.8 MPa·m 1 / 2 .

[0145] Embodiment 3 The preparation method of the gradient pre-stress reinforced high-voltage porcelain sleeve in this embodiment 3 is composed of the following steps: (1) Nanometer boehmite, lithium silicate, kaolin, zirconium silicate sol, and Y2O3-La2O3-CeO2 composite sintering aid are mixed to obtain a mixed material. The mixed material is ball milled in a planetary ball mill for 8.2 hours, sieved through a 200-mesh screen, and then spray granulated. Then, the mixed material is isostatically pressed to prepare a porcelain sleeve green body; (2) Molybdate fine powder, boron nitride nanosheet, lanthanum-zirconium composite sol, and deionized water are uniformly mixed and uniformly dispersed by high-speed shearing stirring. Then, an automatic spraying equipment is used to uniformly form a film on the inner and outer walls of the porcelain sleeve green body to form a first pre-stress transition layer. Finally, the porcelain sleeve green body containing the first pre-stress transition layer is prepared by drying; (3) Halloysite, fused quartz powder, defoaming agent, zirconium hydrogen phosphate, silicon-aluminum sol, and deionized water are uniformly mixed and ball milled in a planetary ball mill to obtain a mixed slurry. The mixed slurry is transferred to a spraying system and uniformly sprayed on the inner and outer surfaces of the first pre-stress transition layer to form a second pre-stress transition layer. The porcelain sleeve green body containing the second pre-stress transition layer is prepared by drying treatment; (4) Fused quartz powder, aluminum phosphate sol, scandium-stabilized cerium-zirconium composite powder, sodium polycarboxylate, and deionized water are uniformly mixed. The mixed material is ball milled in a planetary ball mill to obtain a mixed slurry. The mixed slurry is uniformly applied to the inner and outer surfaces of the second pre-stress transition layer by a spraying system to form a third pre-stress transition layer. The porcelain sleeve green body containing the third pre-stress transition layer is prepared by drying treatment; (5) Nano-alumina, yttria-stabilized zirconia, 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. The slurry was obtained after planetary ball milling, and strontium borosilicate glass powder was added to prepare the glaze slurry with a specific gravity of 1.45 g / cm 3 , filtered through a 325-mesh sieve and then aged, during which ultrasonic oscillation was performed to prepare a glaze, and an electrostatic spraying process was used to evenly spray the glaze on the inner and outer sides of the third prestressed transition layer to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer was prepared, and finally, after sintering, a gradient prestressed reinforced high-voltage porcelain sleeve was prepared.

[0146] in: The porcelain sleeve green body is composed of 75% nano-boehmite, 10% lithium silicate, 8% kaolin, 3% zirconium silicate sol, and 4% Y2O3-La2O3-CeO2 composite sintering aid, calculated by mass percentage.

[0147] In the porcelain sleeve green body, the particle size of nano-boehmite is 80 nm, and the particle size of kaolin is 2 μm.

[0148] The preparation method of the zirconium silicate sol described in step (1) is as follows: using zirconium silicate powder produced by Bengbu Zhongheng New Materials Technology Co., Ltd. as raw material, mixing zirconium silicate powder and deionized water in a mass ratio of 3:7, adding nitric acid accounting for 1% of the mass of the zirconium silicate powder as a dispersant to adjust the pH value of the system to 4, then magnetically stirring for 30 minutes for preliminary mixing, and then transferring the mixture into a ball mill using zirconium oxide balls as grinding media with a ball-to-material ratio of 5:1, ball milling for 6 hours, and finally filtering to remove large particles to obtain a uniform and stable zirconium silicate sol.

[0149] The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid described 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, and rapidly heated to 1600°C at a heating rate of 600°C / min in an air atmosphere and kept warm for 3 minutes, and then rapidly cooled to obtain a densified block; the densified block is coarsely crushed, and then high-energy ball milling is carried out for 6 hours in a zirconium oxide ball mill with ethanol as the medium, with a ball-to-material ratio of 10:1, and finally sieved to obtain D 50 =400nm composite sintering aid powder.

[0150] In step (1), the molding pressure is 150 MPa and the holding time is 4 min.

[0151] The manufacturer of the nano-boehmite in step (1) is Shandong Guoci Functional Materials Co., Ltd.

[0152] The mass of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water in step (2) is 100%, wherein the mullite fine powder is 57%, the lanthanum-zirconium composite sol is 32%, and the deionized water is 11%.

[0153] The mass of the boron nitride nanosheet in step (2) accounts for 3% of the total mass of the mullite fine powder, the lanthanum-zirconium composite sol and the deionized water.

[0154] The particle size of the mullite fine powder in step (2) is 120 μm, and the particle size of the boron nitride nanosheet is 2 μm.

[0155] The production manufacturer of the mullite fine powder in step (2) is Inge Ceramics (Tianjin) New Material Technology Co., Ltd., the content of the mullite phase is 55%, the content of the glass phase is 45%, and the production manufacturer of the boron nitride nanosheet is Suzhou Napo Material Technology Co., Ltd.

[0156] The preparation method of the lanthanum-zirconium composite sol in step (2) is as follows: lanthanum nitrate and zirconium oxychloride are weighed according to a molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a mixed solution with a concentration of 0.5 mol / L, and 1.5 times the molar amount of citric acid relative to the total molar amount of metal ions is added as a stabilizer, then the solution is added dropwise into ammonia water with a pH of 10 at a speed of 1 mL / min for a co-precipitation reaction, and after continuous stirring for 2 hours, the obtained precipitate is centrifuged and washed to neutral, and then re-dispersed in deionized water, and the pH of the system is adjusted to 3 with nitric acid, and after hydrothermal reaction at 100℃ for 6 hours, ultrasonic treatment is performed, and finally a lanthanum-zirconium composite sol with a solid content of 25% is prepared.

[0157] The high-speed shearing stirring in step (2) is first stirred at a speed of 4000 r / min for 5 min, and then stirred at a speed of 2000 r / min for 20 min.

[0158] The atomization pressure is 0.4 MPa and the spraying distance is 12 cm during spraying in step (2).

[0159] The thickness of the single-sided first pre-stress transition layer is accurately controlled to be 0.3 mm in step (2).

[0160] The drying in step (2) is first carried out at 80℃ for 4 h, and then carried out at 120℃ for 4 h.

[0161] The mass of the halloysite, the fused quartz powder, the deionized water, the silicon-aluminum sol and the zirconium hydrogen phosphate in step (3) is 100%, wherein the halloysite accounts for 47%, the fused quartz powder accounts for 18%, the deionized water accounts for 22%, the silicon-aluminum sol accounts for 7%, and the zirconium hydrogen phosphate accounts for 6%.

[0162] The mass of the defoaming agent in step (3) accounts for 1.5% of the total mass of the halloysite, fused quartz powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate.

[0163] The particle size of the halloysite in step (3) is 10 μm, and the particle size of the fused quartz powder is 30 μm.

[0164] In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0165] During spraying in step (3), the atomization pressure is 0.4 MPa and the spraying distance is 12 cm.

[0166] In step (3), the thickness of the second prestressed transition layer on one side is precisely controlled to be 0.6 mm.

[0167] The drying in step (3) is first drying at 80°C for 4 hours and then keeping warm at 120°C for 4 hours.

[0168] The defoaming agent in step (3) is a high-temperature resistant defoaming agent, the manufacturer of which is Anhui IOTA Silicone Oil Co., Ltd., and the model is IOTA 3038-15; the manufacturer of zirconium hydrogen phosphate is Shanghai MacLean Biochemical Technology Co., Ltd., and the manufacturer of silica-alumina sol is Suzhou Nadi Microelectronics Co., Ltd.

[0169] In step (4), the sum of the masses of the fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100%, of which the fused silica powder accounts for 67%, the aluminum phosphate sol accounts for 18%, the deionized water accounts for 13%, the sodium polycarboxylate accounts for 1.8%, and the scandium-stabilized cerium-zirconium composite powder accounts for 0.2%.

[0170] The particle size of the fused quartz powder in step (4) is 25 μm.

[0171] The manufacturer of the aluminum phosphate sol in step (4) is Wuhan Jiyesheng Chemical Co., Ltd., and the solid content of the aluminum phosphate sol is 40%. The manufacturer of the scandium-stabilized cerium-zirconium composite powder is Hunan Rare Earth Metal Materials Research Institute Co., Ltd., and the manufacturer of the polycarboxylate sodium salt dispersant is Kedeli Chemical Technology Co., Ltd., and the model is SAMASO DP5045.

[0172] In step (4), the ball milling speed is 400 r / min and the ball milling time is 4 h.

[0173] The atomization pressure during spraying in step (4) is 0.4 MPa, and the spraying distance is 12 cm.

[0174] In step (4), the thickness of the third prestressed transition layer on one side is precisely controlled to be 0.4 mm.

[0175] The drying condition in step (4) is first drying at 80℃ for 4h, and then keeping at 120℃ for 4h.

[0176] The mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral and deionized water in step (5) is 100%, wherein the nano-alumina accounts for 32%, the yttrium-stabilized zirconia accounts for 23%, the silica sol accounts for 17%, the sodium polyacrylate dispersant accounts for 1.2%, the polyvinyl butyral accounts for 4.5%, and the deionized water accounts for 22.3%.

[0177] The strontium borosilicate glass powder in step (5) is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of the nano-alumina, yttrium-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral and deionized water.

[0178] The manufacturer of the strontium borosilicate glass powder in step (5) is Suzhou Qiuyi New Material Co., Ltd.

[0179] The particle size of the nano-alumina in step (5) is 3μm, the particle size of the yttrium-stabilized zirconia is 0.8μm, the solid content of the silica sol is 30%, the sodium polyacrylate is a liquid type with a molecular weight of 8000, the particle size of the polyvinyl butyral powder is 50μm, and the particle size of the strontium borosilicate glass powder is 10μm.

[0180] The ball milling speed in step (5) is 400r / min, and the ball milling time is 6h.

[0181] The aging time in step (5) is 24h, and the aging temperature is room temperature.

[0182] The ultrasonic condition in step (5) is 10min of ultrasonic vibration every 2h.

[0183] The spraying voltage of the electrostatic spraying process in step (5) is 60kV.

[0184] The thickness of the single-sided glaze layer in step (5) is controlled to be 0.2mm.

[0185] The drying treatment in step (5) is drying in a 100℃ oven for 1h to preliminarily solidify the glaze layer.

[0186] The sintering in step (5) is heating at a rate of 5℃ / min from 100℃ to 700℃, then heating at a rate of 4℃ / min from 700℃ to 1000℃, heating at a rate of 3℃ / min from 1000℃ to 1210℃, heating at a rate of 2℃ / min from 1210℃ to 1290℃, heating at a rate of 1℃ / min from 1290℃ to 1300℃ and keeping for 2h, and then cooling to room temperature in the furnace and taking out.

[0187] The gradient prestress reinforced high-voltage porcelain sleeve prepared in step (5) is composed of, from outside to inside, a glaze layer, a third prestress transition layer, a second prestress transition layer, a first prestress transition layer, a porcelain sleeve green body, the first prestress transition layer, the second prestress transition layer, the third prestress transition layer, and the glaze layer. The high-voltage porcelain sleeve prepared in this embodiment 3 has a fracture toughness of 9.5 MPa·m measured by the single-edge notched beam method 1 / 2 .

[0188] Comparative Example 1 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve in this comparative example 1 is the same as that in embodiment 1, and the only difference is that no first prestress transition layer, second prestress transition layer, and third prestress transition layer are provided, that is, the structure of the gradient prestress reinforced high-voltage porcelain sleeve prepared in this comparative example 1 is a glaze layer, a porcelain sleeve green body, and a glaze layer. The high-voltage porcelain sleeve prepared in this comparative example 1 has a fracture toughness of 7.3 MPa·m measured by the single-edge notched beam method 1 / 2 .

[0189] Comparative Example 2 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve in this comparative example 2 is the same as that in embodiment 1, and the only difference is that no first prestress transition layer is provided, that is, the gradient prestress reinforced high-voltage porcelain sleeve prepared in this comparative example 2 is composed of, from outside to inside, a glaze layer, a third prestress transition layer, a second prestress transition layer, a porcelain sleeve green body, a second prestress transition layer, a third prestress transition layer, and a glaze layer. The high-voltage porcelain sleeve prepared in this comparative example 2 has a fracture toughness of 8.1 MPa·m measured by the single-edge notched beam method 1 / 2 .

[0190] Comparative Example 3 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve in this comparative example 3 is the same as that in embodiment 1, and the only difference is that no second prestress transition layer is provided, that is, the gradient prestress reinforced high-voltage porcelain sleeve prepared in this comparative example 3 is composed of, from outside to inside, a glaze layer, a third prestress transition layer, a first prestress transition layer, a porcelain sleeve green body, a first prestress transition layer, a third prestress transition layer, and a glaze layer. The high-voltage porcelain sleeve prepared in this comparative example 3 has a fracture toughness of 8.3 MPa·m measured by the single-edge notched beam method 1 / 2 .

[0191] Comparative Example 4 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the comparative example 4 is the same as that of the example 1, and the only difference is that the third prestress transition layer is not arranged, that is, the gradient prestress reinforced high-voltage porcelain sleeve prepared by the comparative example 4 is from outside to inside respectively glaze layer, second prestress transition layer, first prestress transition layer, porcelain sleeve green body, first prestress transition layer, second prestress transition layer, glaze layer. The high-voltage porcelain sleeve prepared by the comparative example 4 has a fracture toughness of 8.0 MPa·m after being measured by the single-side notched beam method 1 / 2 .

[0192] Comparative example 5 The preparation method of the gradient prestress reinforced high-voltage porcelain sleeve of the comparative example 5 is the same as that of the example 1, and the only difference is that the raw materials for preparing the first prestress transition layer and the third prestress transition layer are unchanged, but the positions of the first prestress transition layer and the third prestress transition layer are exchanged, that is, the gradient prestress reinforced high-voltage porcelain sleeve prepared by the comparative example 5 is from outside to inside respectively glaze layer, first prestress transition layer, second prestress transition layer, third prestress transition layer, porcelain sleeve green body, third prestress transition layer, second prestress transition layer, first prestress transition layer, glaze layer. The high-voltage porcelain sleeve prepared by the comparative example 5 has a fracture toughness of 8.6 MPa·m after being measured by the single-side notched beam method 1 / 2 .

[0193] It can be known from the comparison of the comparative examples 1-5 and the examples 1-3 that the fracture toughness of the high-voltage porcelain sleeve prepared by the examples 1-3 is obviously better than that of the comparative examples 1-5. In the comparative examples 1-5, the fracture toughness of the high-voltage porcelain sleeve prepared due to the absence of a certain prestress transition layer or the change of the position is greatly reduced.

[0194] The above is only a preferred embodiment of the present application, and does not limit other forms of the present application. Any person skilled in the art can modify or change the above disclosed technical content into equivalent embodiments. However, any simple modification, equivalent change and modification of the above examples made without departing from the technical solution content of the present application and according to the technical essence of the present application still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a gradient prestressed reinforced high-voltage porcelain bushing, characterized by: It consists of the following steps: (1) Nanoboehmite, lithium silicate, kaolin, zirconium silicate sol and Y2O3-La2O3-CeO2 composite sintering aid are used as raw materials to obtain a mixture, the mixture is subjected to planetary ball milling 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) Molecule powder, boron nitride nanosheets, lanthanum zirconium composite sol and deionized water are uniformly mixed and uniformly dispersed by high-speed shear stirring. Then, an automatic spraying device is used to uniformly form a film on the inner and outer walls of the porcelain sleeve green body to form a first prestressed transition layer. Finally, the green body of the porcelain sleeve containing the first prestressed transition layer is prepared by drying. (3) halloysite, fused quartz powder, defoaming agent, zirconium hydrogen phosphate, silica-alumina sol and deionized water are uniformly mixed, ball-milled in a planetary ball mill to obtain a mixed slurry, the mixed slurry is transferred to a spraying system, and uniformly sprayed on the inner and outer surfaces of the first prestressed transition layer to form a second prestressed transition layer, and dried to prepare a porcelain sleeve green body containing the second prestressed transition layer; (4) Evenly mixing fused quartz powder, aluminum phosphate sol, scandium-stabilized cerium-zirconium composite powder, sodium polycarboxylate and deionized water, ball milling the mixture in a planetary ball mill to obtain a mixed slurry, and applying the mixed slurry evenly to the inner and outer surfaces of the second prestressed transition layer using a spraying system to form a third prestressed transition layer. After drying, a porcelain sleeve green body containing the third prestressed transition layer is prepared; (5) Nano-alumina, yttria-stabilized zirconia, silica sol, sodium polyacrylate, and polyvinyl butyral were mixed in proportion, and deionized water was added to adjust the glaze slurry viscosity to 1.1-1.3 Pa·s. The slurry was obtained after planetary ball milling, and strontium borosilicate glass powder was added to adjust the glaze slurry specific gravity to 1.35-1.45 g / cm 3 , filtered through a 325-mesh sieve and then aged, during which ultrasonic oscillation was performed to prepare a glaze, and an electrostatic spraying process was used to evenly spray the glaze on the inner and outer sides of the third prestressed transition layer to form a glaze layer. After drying, a porcelain sleeve with a sprayed glaze layer was prepared, and finally, after sintering, a gradient prestressed reinforced high-voltage porcelain sleeve was prepared.

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

3. The method for preparing the gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: The preparation method of the zirconium silicate sol described in step (1) is as follows: using zirconium silicate powder as raw material, mixing zirconium silicate powder and deionized water in a mass ratio of 3:7, adding nitric acid accounting for 1-2% of the mass of the zirconium silicate powder as a dispersant to adjust the pH value of the system to 3-4, then magnetically stirring for 30 minutes for preliminary mixing, and then transferring the mixture into a ball mill using zirconium oxide balls as grinding media with a ball-to-material ratio of 5:1, ball milling for 5-6 hours, and finally filtering to remove large particles to obtain a uniform and stable zirconium silicate sol.

4. The method for preparing the gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: The preparation method of the Y2O3-La2O3-CeO2 composite sintering aid described in step (1) is as follows: high-purity Y2O3, La2O3 and CeO2 powders are weighed and mixed uniformly in a molar ratio of 4:3:3, the mixed powder is pressed into a green body, and then placed in a flash furnace, and the temperature is rapidly increased to 1550-1600°C at a heating rate of 600°C / min in an air atmosphere and kept warm for 3-5 minutes, and then rapidly cooled to obtain a densified block; the densified block is coarsely crushed, and then high-energy ball milling is performed for 4-6 hours in a zirconium oxide ball mill with ethanol as the medium, with a ball-to-material ratio of 10:1, and finally sieved to obtain D 50 =400-600nm composite sintering aid powder.

5. The method for preparing the gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: The mass sum of the molexite fine powder, lanthanum zirconium composite sol and deionized water in step (2) is 100%, wherein the molexite 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 the boron nitride nanosheets accounts for 3% of the total mass of the molybdenum powder, the lanthanum zirconium composite sol and the deionized water; In step (2), the particle size of the molybdenum 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 a molar ratio of La:Zr = 1:9, dissolved in deionized water to prepare a 0.5 mol / L mixed solution, and 1.5 times the molar amount of citric acid relative to the total molar amount of metal ions is added as a stabilizer, and then the solution is added dropwise to ammonia water with a pH = 10 at a rate of 1 mL / min for coprecipitation reaction, and the mixture is stirred for 2 hours and then allowed to stand for 12 hours. The obtained precipitate is centrifuged and washed to neutrality, and then redispersed in deionized water, and the pH of the system is adjusted to 3-4 with nitric acid. After hydrothermal reaction at 100°C for 6 hours, ultrasonic treatment is performed to finally obtain a lanthanum-zirconium composite sol with a solid content of 25%.

6. The method for preparing the gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: The high-speed shear stirring in step (2) is first stirring at a speed of 4000 r / min for 5 minutes, and then stirring at a speed of 2000 r / min for 20 minutes; During spraying in step (2), the atomizing pressure 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 in step (2) is first carried out at 80°C for 4 hours and then at 120°C for 4 hours.

7. The method for preparing a gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: The sum of the mass of the halloysite, fused quartz powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate in step (3) is 100%, wherein the halloysite accounts for 43%-47%, the fused quartz powder accounts for 18%-22%, the deionized water accounts for 18%-22%, the silica-alumina sol accounts for 7%-13%, and the zirconium hydrogen phosphate accounts for 4%-6%; The mass of the defoaming agent in step (3) accounts for 1.5% of the total mass of the halloysite, fused quartz powder, deionized water, silica-alumina sol and zirconium hydrogen phosphate; The particle size of the halloysite in step (3) is 10 μm, and the particle size of the fused quartz powder is 30 μm; In step (3), the ball milling speed is 400 r / min and the ball milling time is 4 h; During spraying in step (3), the atomizing pressure 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 in step (3) is 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-voltage porcelain bushing according to claim 1, characterized in that: In step (4), the sum of the mass of the fused silica powder, aluminum phosphate sol, deionized water, sodium polycarboxylate and scandium-stabilized cerium-zirconium composite powder is 100%, wherein the fused silica powder accounts for 63-67%, the aluminum phosphate sol accounts for 13-18%, the deionized water accounts for 13-22%, the sodium polycarboxylate accounts for 1.2-1.8%, and the scandium-stabilized cerium-zirconium composite powder accounts for 0.2-0.8%; The particle size of the fused silica powder 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; The atomization pressure during spraying in step (4) 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 in step (4) are first drying at 80°C for 4 hours and then keeping warm at 120°C for 4 hours.

9. The method for preparing a gradient prestressed reinforced high-voltage porcelain bushing according to claim 1, characterized in that: In step (5), the sum of the masses of nano-alumina, yttria-stabilized zirconia, silica sol, sodium polyacrylate, polyvinyl butyral and deionized water is 100%, wherein nano-alumina accounts for 28%-32%, yttria-stabilized zirconia 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%; The strontium borosilicate glass powder described in step (5) is used as a binder, and the mass of the strontium borosilicate glass powder accounts for 10% of the total mass of nano-alumina, yttria-stabilized zirconia, 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 yttria-stabilized zirconia 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-voltage 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; The ultrasonic condition in step (5) is to perform ultrasonic oscillation for 10 minutes every 2 hours; In step (5), the electrostatic spraying process has a spraying voltage of 50-60 kV; In step (5), the thickness of the glaze layer on one side is controlled at 0.2-0.3 mm; The drying process in step (5) is to dry the glaze layer in an oven at 80-100°C for 1-2 hours to initially solidify the glaze layer; The sintering in step (5) is carried out by heating from 100°C to 700°C at a heating rate of 5°C / min, then from 700°C to 1000°C at a heating rate of 4°C / min, from 1000°C to 1210°C at a heating rate of 3°C / min, from 1210°C to 1290°C at a heating rate of 2°C / min, and from 1290°C to 1300°C at a heating rate of 1°C / min, and then the sintered product is cooled to room temperature and then taken out of the furnace.

Images