Preparation method of ceramic insulator with high insulation performance

Abstract

The application relates to the technical field of functional ceramic preparation, in particular to a preparation method of a high-insulation-performance ceramic insulator; the method takes modified alumina-based powder as a base material, combines barium carbonate, Suzhou soil and calcined talcum powder, carries out wet ball milling, spray granulation, dry pressing forming, glue removal and high-temperature sintering to obtain an insulator porcelain body, grinds the surface of the porcelain body, carries out pressure impregnation by using methyl silicone oil and carries out drying and solidification, and finally the high-insulation-performance ceramic insulator is prepared; wherein the modified alumina-based powder is prepared by the following steps: mixing alpha-alumina powder, pseudo-boehmite and a lanthanum nitrate solution, pre-sintering to prepare alumina-based pre-reaction powder, carrying out sol-gel coating by using a precursor solution containing barium acetate and a titanate coupling agent, and carrying out drying and calcination; the two-stage modification of the alumina powder effectively controls the ceramic grain boundary structure, and the prepared ceramic insulator has excellent insulation performance and high compactness.

Description

Technical Field

[0001] This invention relates to the field of functional ceramics preparation technology, specifically to a method for preparing a ceramic insulator with high insulation performance. Background Technology

[0002] Alumina ceramic insulators are widely used in power transmission, rail transportation, and high-frequency insulation applications due to their excellent mechanical strength, high-temperature resistance, and chemical stability. These insulators typically use α-alumina as the main crystalline phase, and introduce alkaline earth metal oxides and silicon dioxide to form a liquid phase, promoting sintering densification and resulting in a high-insulation ceramic body with high volume resistivity and low dielectric loss. With the development of ultra-high voltage power transmission and the miniaturization of electrical equipment, higher requirements are placed on the insulation reliability of alumina ceramic insulators under harsh operating conditions.

[0003] In existing alumina ceramic insulator manufacturing, to improve sintering performance while maintaining insulation properties, the common approach is to add sintering aids in conjunction with rare earth oxide doping. This method achieves densification through the intergranular liquid phase formed by the aids, while simultaneously utilizing the segregation effect of rare earth ions at grain boundaries to regulate the structure. However, conventional doping methods alone are insufficient to construct a uniform high-resistivity barrier at grain boundaries. Grain boundary regions are prone to becoming weak paths for charge transport due to impurity enrichment or continuous distribution of the glassy phase, limiting further improvements in insulation performance. Furthermore, achieving a balance between sintering densification and grain boundary insulation control is challenging; insufficient density or uneven distribution of the grain boundary phase both reduce the overall insulation level of the ceramic body.

[0004] Therefore, while ensuring the high density of alumina ceramic insulators, how to effectively regulate the composition and structure of grain boundaries to enhance their insulation capacity remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention effectively regulates the ceramic grain boundary structure by modifying alumina powder, thereby enhancing the grain boundary insulation capacity while ensuring high density, resulting in ceramic insulators with excellent insulation performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-insulation-performance ceramic insulator includes the following steps: S1. By weight, mix 3-6 parts of barium carbonate powder with 4.5-12 parts of deionized water to prepare barium carbonate slurry, add 90-110 parts of modified alumina-based powder, and wet ball mill until the particle size D50 is 0.8-1.2 μm to obtain the first slurry; S2. Mix 1-3 parts of Suzhou clay and 1-2 parts of calcined talc powder to obtain a mixed solid. Add deionized water and mix the mixed solid and deionized water at a mass ratio of 1:(1-1.5). Wet ball mill until the particle size D50 is 0.6-1.0 μm to obtain the second slurry. S3. Combine the first slurry and the second slurry, stir and disperse to form a composite slurry, and spray granulate to obtain granulated powder; S4. The granulated powder is dry-pressed under a molding pressure of 100-150 MPa to obtain an insulator blank; S5. The insulator blank is debonded, heated, sintered, and cooled to obtain the insulator ceramic body; S6. Grind the insulator porcelain body, then place the insulator porcelain body in methyl silicone oil at 120-180℃, the amount of methyl silicone oil being 1-2 times the mass of the insulator porcelain body, and impregnate under pressure for 0.5-2 hours; S7. Remove the impregnated ceramic insulator body and dry and cure it at 200-300℃ for 2-4 hours to obtain a ceramic insulator with high insulation performance.

[0007] Furthermore, the modified alumina-based powder is prepared by the following steps: A1. By weight, 100 parts of α-alumina powder are mixed with 5 to 12 parts of boehmite, and 85 to 170 parts of lanthanum nitrate hexahydrate solution with a mass concentration of 1 to 3% are added. The mixture is stirred and ultrasonically dispersed to obtain a slurry, which is then spray-dried and granulated, and pre-sintered to obtain alumina-based pre-reacted powder. A2. Mix the alumina-based pre-reacted powder with anhydrous ethanol, add deionized water and stir until homogeneous to obtain a suspension; A3. Dissolve 1-3 parts of barium acetate and 2-4 parts of titanate coupling agent in 8-12 parts of acetylacetone to obtain a precursor solution. While stirring continuously, drop the precursor solution into the suspension. After the addition is complete, continue stirring to form a gel-like mixture. A4. After drying the gel-like mixture, calcination was carried out at 350–450°C in air atmosphere to obtain modified alumina-based powder; Furthermore, in step A1, the particle size D50 of the α-alumina powder is 10-20 μm, the specific surface area of ​​the pseudoboehmite is 200-300 m² / g, the ultrasonic dispersion time is 30-60 min, the pre-sintered powder is cooled, crushed, and passed through a 200-mesh sieve, the pre-sintering temperature is 1100-1250℃, and the pre-sintering time is 2-4 h.

[0008] Furthermore, the raw materials in step A2, by weight, include 100 parts of alumina-based pre-reaction powder, 120-230 parts of anhydrous ethanol, and 3-6 parts of deionized water.

[0009] Furthermore, in step A3, the titanate coupling agent is either tetrabutyl titanate or tetraisopropyl titanate, the dropwise rate of the precursor solution is 0.5–1.5 mL / min, and the stirring time is 60–90 min after the dropwise addition is completed.

[0010] Furthermore, in step A4, the drying temperature is 60–80°C, the drying time is 8–12 h, the calcination time is 1–2 h, and the particle size D50 of the obtained modified alumina-based powder is 10–20 μm.

[0011] Furthermore, in steps S1 and S2, the ball-to-material mass ratio during wet ball milling is (2-4):1, the milling medium is zirconia balls, and the milling speed is 200-400 r / min.

[0012] Furthermore, in step S2, the mass content of SiO2 in the Suzhou soil is not less than 45%, and the mass content of Al2O3 is not less than 35%; the loss on ignition of the calcined talc powder is not greater than 0.5%, the mass content of magnesium oxide is not less than 30%, and the particle size D50 is 5-15 μm.

[0013] Furthermore, in step S3, the stirring speed is 200–400 r / min, and the stirring time is 15–30 min; in the spray granulation process, the inlet temperature of the spray granulation is 200–250℃, the outlet temperature is 100–120℃, and the particle size of the granulated powder is 60–120 μm.

[0014] Furthermore, in step S4, the pressure increase rate during dry pressing is 15-25 MPa / s, the holding time is 30-60 s, and a bidirectional pressure application method is adopted.

[0015] Furthermore, in step S5, the adhesive removal temperature is 500-600℃, the adhesive removal time is 1-3h, the sintering temperature is 1550-1620℃, the sintering time is 2-4h, and after sintering, the temperature is cooled to 800℃ at a rate of 3-8℃ / min, and then naturally cooled to room temperature.

[0016] Furthermore, in step S6, the grinding process makes the surface roughness Ra of the insulator ceramic body ≤ 0.5 μm, the pressure of the pressure impregnation is 0.1~0.3MPa, and the viscosity of the methyl silicone oil is 50~200mPa·s.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) In this invention, pseudoboehmite and lanthanum nitrate hexahydrate are introduced into the alumina powder system through pre-reaction treatment. During the pre-firing process, pseudoboehmite undergoes a crystal transformation and releases sintering activity in situ, reducing the sintering driving force required for subsequent densification. After the decomposition of lanthanum nitrate, lanthanum ions are uniformly pre-distributed on the particle surface and agglomerate at the alumina grain boundaries during final sintering, generating a solute dragging effect, which effectively inhibits abnormal grain growth and makes the ceramic structure uniform and refined, laying a structural foundation for improving insulation performance.

[0018] (2) Based on the pre-reacted powder, the present invention forms a uniform gel coating layer on the particle surface by barium acetate and titanate coupling agent through sol-gel method. After calcination, it is transformed into a high-insulation precursor layer containing barium titanium oxide. During the final high-temperature sintering, the coating layer is enriched in the grain boundary region and works synergistically with the pre-doped lanthanum element to build a double barrier at the grain boundary that hinders the transport of charge carriers, which significantly improves the volume resistivity and power frequency breakdown strength of the ceramic.

[0019] (3) In the insulator forming and sintering process, this invention uses barium carbonate, Suzhou clay and calcined talc as composite sintering aids to form an appropriate amount of silicate liquid phase at high temperature. Combined with the sintering activity carried by the modified powder itself, the ceramic body is fully densified and has a low water absorption rate. At the same time, the staged heating and debinding process and sintering process enable the organic matter to be fully decomposed and the liquid phase to flow uniformly, effectively avoiding cracking of the green body and thermal stress concentration, thus taking into account both the density and mechanical reliability of the ceramic body.

[0020] (4) After sintering, the ceramic body of the present invention is subjected to precision grinding to remove the defect layer, and then impregnated with methyl silicone oil under pressure and dried and cured. The methyl silicone oil penetrates and fills the openings and microcracks on the surface of the ceramic body. After curing, a continuous sealing layer is formed, which further improves the surface insulation reliability of the insulator under humid or polluted conditions. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0022] A method for preparing a high-insulation-performance ceramic insulator includes the following steps: S1. By weight, mix 3 parts of barium carbonate powder with 4.5 parts of deionized water to prepare barium carbonate slurry, add 90 parts of modified alumina-based powder, and wet ball mill until the particle size D50 is 1.2 μm to obtain the first slurry; In the wet ball milling process, the ball-to-material mass ratio is 2:1, the ball milling media is zirconia balls, and the ball milling speed is 200 r / min. S2. Mix 1 part Suzhou soil and 1 part calcined talc powder to obtain a mixed solid. Add deionized water and mix the mixed solid and deionized water at a mass ratio of 1:1. Wet ball mill until the particle size D50 is 1.0 μm to obtain the second slurry. The Suzhou soil contains 45% SiO2, 38% Al2O3, 0.3% loss on ignition of calcined talc, 30% magnesium oxide, and a particle size D50 of 5 μm. The ball-to-material mass ratio during wet ball milling is 2:1, the milling media is zirconia balls, and the milling speed is 200 r / min. S3. Combine the first slurry and the second slurry, stir and disperse to form a composite slurry, and spray granulate to obtain granulated powder; The stirring and dispersing speed is 200 r / min, the stirring time is 30 min, the inlet temperature of spray granulation is 200℃, the outlet temperature is 100℃, and the particle size of the granulated powder is 120 μm. S4. The granulated powder is dry-pressed under a molding pressure of 100MPa to obtain an insulator blank; The pressure increase rate during dry pressing is 15 MPa / s, the holding time is 60 s, and a bidirectional pressure application method is used. S5. The insulator blank is debonded, heated, sintered in air atmosphere, and cooled to obtain the insulator porcelain body; The debinding treatment temperature is 500℃, the debinding treatment time is 3h, the sintering temperature is 1550℃, the sintering time is 4h, and after sintering, it is cooled to 800℃ at a rate of 3℃ / min, and then naturally cooled to room temperature. S6. Grind the insulator porcelain body, then place the insulator porcelain body in methyl silicone oil at 120℃, the amount of methyl silicone oil is 1 times the mass of the insulator porcelain body, and impregnate under pressure for 2 hours; Among them, the grinding process makes the surface roughness Ra of the insulator ceramic body 0.5μm, the pressure of the pressure impregnation is 0.1MPa, and the viscosity of the methyl silicone oil is 200mPa·s; S7. Remove the impregnated ceramic insulator body and dry and cure it at 200℃ for 4 hours to obtain a high-insulation-performance ceramic insulator.

[0023] The modified alumina-based powder in this embodiment is prepared by the following steps: A1. By weight, 100 parts of α-alumina powder and 5 parts of pseudoboehmite are mixed, 85 parts of 1% lanthanum nitrate hexahydrate solution are added, stirred and ultrasonically dispersed to obtain a slurry, spray-dried and granulated, and pre-sintered in an air atmosphere to obtain alumina-based pre-reacted powder. The particle size D50 of α-alumina powder is 10μm, the specific surface area of ​​boehmite is 200m² / g, the ultrasonic dispersion time is 60min, the pre-calcined powder is cooled, crushed and passed through a 200-mesh sieve, the pre-sintering temperature is 1100℃, and the pre-sintering time is 4h. A2. By weight, 100 parts of alumina-based pre-reaction powder and 120 parts of anhydrous ethanol are mixed, 3 parts of deionized water are added and stirred evenly to obtain a suspension; A3. Dissolve 1 part barium acetate and 2 parts tetrabutyl titanate in 8 parts acetylacetone to obtain a precursor solution. While stirring continuously, add the precursor solution dropwise into the suspension. After the addition is complete, continue stirring to form a gel-like mixture. The precursor solution was added at a rate of 0.5 mL / min, and stirring was continued for 90 min after the addition was completed. A4. After drying the gel-like mixture, calcination was carried out at 350°C in air atmosphere to obtain modified alumina-based powder; The drying temperature was 60℃, the drying time was 12h, the calcination time was 2h, and the particle size D50 of the obtained modified alumina-based powder was 10μm. Example 2:

[0024] A method for preparing a high-insulation-performance ceramic insulator includes the following steps: S1. By weight, 4.5 parts of barium carbonate powder and 8 parts of deionized water are mixed to prepare barium carbonate slurry. 100 parts of modified alumina-based powder are added and wet ball milled until the particle size D50 is 1.0 μm to obtain the first slurry. In the wet ball milling process, the ball-to-material mass ratio is 3:1, the ball milling media is zirconia balls, and the ball milling speed is 300 r / min. S2. Mix 2 parts Suzhou soil and 1.5 parts calcined talc powder to obtain a mixed solid. Add deionized water and mix the mixed solid and deionized water at a mass ratio of 1:1.2. Wet ball mill until the particle size D50 is 0.8μm to obtain the second slurry. The Suzhou soil contained 48% SiO2, 36% Al2O3, 0.4% loss on ignition of calcined talc, 33% magnesium oxide, and a particle size D50 of 10 μm. The ball-to-material mass ratio during wet ball milling was 3:1, the milling media was zirconia balls, and the milling speed was 300 r / min. S3. Combine the first slurry and the second slurry, stir and disperse to form a composite slurry, and spray granulate to obtain granulated powder; The stirring and dispersing speed is 300 r / min, the stirring time is 20 min, the inlet temperature of spray granulation is 220℃, the outlet temperature is 110℃, and the particle size of the granulated powder is 90 μm. S4. The granulated powder is dry-pressed under a molding pressure of 120MPa to obtain an insulator blank; The pressure increase rate during dry pressing is 20 MPa / s, the holding time is 45 s, and a bidirectional pressure application method is used. S5. The insulator blank is debonded, heated, sintered in air atmosphere, and cooled to obtain the insulator porcelain body; The debinding treatment temperature is 550℃, the debinding treatment time is 2h, the sintering temperature is 1585℃, the sintering time is 3h, and after sintering, it is cooled to 800℃ at a rate of 5℃ / min, and then naturally cooled to room temperature. S6. Grind the insulator porcelain body, then place the insulator porcelain body in methyl silicone oil at 150℃, the amount of methyl silicone oil being 1.5 times the mass of the insulator porcelain body, and impregnate it under pressure for 1 hour; Among them, the grinding process makes the surface roughness Ra of the insulator ceramic body 0.3μm, the pressure of the pressure impregnation is 0.2MPa, and the viscosity of the methyl silicone oil is 100mPa·s; S7. Remove the impregnated ceramic insulator body and dry and cure it at 250℃ for 3 hours to obtain a high-insulation-performance ceramic insulator.

[0025] The modified alumina-based powder in this embodiment is prepared by the following steps: A1. By mass, 100 parts of α-alumina powder and 8 parts of boehmite are mixed, and 130 parts of 2% lanthanum nitrate hexahydrate solution are added. The mixture is stirred and ultrasonically dispersed to obtain a slurry. The slurry is spray-dried and granulated, and then pre-sintered in an air atmosphere to obtain alumina-based pre-reacted powder. The particle size D50 of α-alumina powder is 15μm, the specific surface area of ​​boehmite is 250m² / g, the ultrasonic dispersion time is 45min, the pre-calcined powder is cooled, crushed and passed through a 200-mesh sieve, the pre-sintering temperature is 1200℃, and the pre-sintering time is 3h. A2. By weight, mix 100 parts of alumina-based pre-reaction powder with 180 parts of anhydrous ethanol, add 4.5 parts of deionized water and stir evenly to obtain a suspension; A3. Dissolve 2 parts of barium acetate and 3 parts of tetraisopropyl titanate in 10 parts of acetylacetone to obtain a precursor solution. While stirring continuously, add the precursor solution dropwise into the suspension. After the addition is complete, continue stirring to form a gel-like mixture. The precursor solution was added at a rate of 1.0 mL / min, and stirring was continued for 75 min after the addition was completed. A4. After drying the gel-like mixture, calcination was carried out at 400°C in air atmosphere to obtain modified alumina-based powder; The drying temperature was 70℃, the drying time was 10h, the calcination time was 1.5h, and the particle size D50 of the obtained modified alumina-based powder was 15μm. Example 3:

[0026] A method for preparing a high-insulation-performance ceramic insulator includes the following steps: S1. By weight, 6 parts of barium carbonate powder and 12 parts of deionized water are mixed to prepare barium carbonate slurry. 110 parts of modified alumina-based powder are added and wet ball milled until the particle size D50 is 0.8 μm to obtain the first slurry. In the wet ball milling process, the ball-to-material mass ratio is 4:1, the ball milling media is zirconia balls, and the ball milling speed is 400 r / min. S2. Mix 3 parts Suzhou soil and 2 parts calcined talc powder to obtain a mixed solid. Add deionized water and mix the mixed solid and deionized water at a mass ratio of 1:1.5. Wet ball mill until the particle size D50 is 0.6μm to obtain the second slurry. The Suzhou soil contains 50% SiO2, 35% Al2O3, 0.5% loss on ignition of calcined talc, 35% magnesium oxide, and a particle size D50 of 15 μm. The ball-to-material mass ratio during wet ball milling is 4:1, the milling media is zirconia balls, and the milling speed is 400 r / min. S3. Combine the first slurry and the second slurry, stir and disperse to form a composite slurry, and spray granulate to obtain granulated powder; The stirring and dispersing speed is 400 r / min, the stirring time is 15 min, the inlet temperature of spray granulation is 250℃, the outlet temperature is 120℃, and the particle size of the granulated powder is 60 μm. S4. The granulated powder is dry-pressed under a molding pressure of 150 MPa to obtain an insulator blank; The pressure increase rate during dry pressing is 25 MPa / s, the holding time is 30 s, and a bidirectional pressure application method is used. S5. The insulator blank is debonded, heated, sintered in air atmosphere, and cooled to obtain the insulator porcelain body; The debinding treatment temperature is 600℃, the debinding treatment time is 1h, the sintering temperature is 1620℃, the sintering time is 2h, and after sintering, it is cooled to 800℃ at a rate of 8℃ / min, and then naturally cooled to room temperature. S6. Grind the insulator porcelain body, then place the insulator porcelain body in methyl silicone oil at 180℃, the amount of methyl silicone oil being twice the mass of the insulator porcelain body, and impregnate under pressure for 0.5h. Among them, the grinding process makes the surface roughness Ra of the insulator ceramic body 0.1μm, the pressure of the pressure impregnation is 0.3MPa, and the viscosity of the methyl silicone oil is 50mPa·s; S7. Remove the impregnated ceramic insulator body and dry and cure it at 300℃ for 2 hours to obtain a high-insulation-performance ceramic insulator.

[0027] The modified alumina-based powder in this embodiment is prepared by the following steps: A1. By mass, 100 parts of α-alumina powder and 12 parts of pseudoboehmite are mixed, and 170 parts of 3% lanthanum nitrate hexahydrate solution are added. The mixture is stirred and ultrasonically dispersed to obtain a slurry. The slurry is spray-dried and granulated, and then pre-sintered in an air atmosphere to obtain alumina-based pre-reacted powder. The particle size D50 of α-alumina powder is 20μm, the specific surface area of ​​boehmite is 300m² / g, the ultrasonic dispersion time is 30min, the pre-calcined powder is cooled, crushed and passed through a 200-mesh sieve, the pre-sintering temperature is 1250℃, and the pre-sintering time is 2h. A2. By weight, 100 parts of alumina-based pre-reaction powder and 230 parts of anhydrous ethanol are mixed, 6 parts of deionized water are added and stirred evenly to obtain a suspension; A3. Dissolve 3 parts of barium acetate and 4 parts of tetraisopropyl titanate in 12 parts of acetylacetone to obtain a precursor solution. While stirring continuously, add the precursor solution dropwise into the suspension. After the addition is complete, continue stirring to form a gel-like mixture. The precursor solution was added at a rate of 1.5 mL / min, and stirring was continued for 60 min after the addition was completed. A4. After drying the gel-like mixture, calcination was carried out at 450°C in air atmosphere to obtain modified alumina-based powder; The drying temperature was 80℃, the drying time was 8h, the calcination time was 1h, and the particle size D50 of the obtained modified alumina-based powder was 20μm.

[0028] Comparative Example 1 The difference between this comparative example and Example 1 is that an equal amount of unmodified alumina-based powder is used instead of modified alumina-based powder in this comparative example, while the other components and preparation methods are completely consistent with those in Example 1.

[0029] The unmodified alumina-based powder was prepared by the following method: 100 parts by mass of α-alumina powder with a particle size D50 of 10 μm were mixed with 5 parts of boehmite with a specific surface area of ​​200 m² / g, 85 parts of deionized water were added, the mixture was stirred and ultrasonically dispersed for 60 min to obtain a slurry, which was then spray-dried and granulated, pre-calcined at 1100℃ for 4 h, cooled, crushed and passed through a 200-mesh sieve to obtain the unmodified alumina-based powder.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that an equal amount of alumina-based pre-reacted powder is used instead of modified alumina-based powder in this comparative example. The preparation method of the alumina-based pre-reacted powder is the same as that in Example 1. Other components and preparation methods are completely consistent with those in Example 1.

[0031] Performance testing: The ceramic insulators prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to the following relevant performance tests: 1. Volume resistivity: Measured using a three-electrode system, in accordance with GB / T 31838.2-2019 standard; 2. Power frequency breakdown strength: Measured in transformer oil at room temperature using a continuous voltage ramping method, in accordance with GB / T 1408.1-2016 standard; 3. Water absorption rate: determined by boiling method according to GB / T 25995-2010 standard; 4. Bending strength: The bending strength was determined using the three-point bending method, in accordance with GB / T 6569-2006 standard.

[0032] Each group of samples was tested three times, and the average value was taken. The test results are shown in Table 1: Table 1 Example 1 <![CDATA[3.72×10 14 ]]> 25.4 0.11 352 Example 2 <![CDATA[4.68×10 14 ]]> 27.6 0.08 375 Example 3 <![CDATA[4.15×10 14 ]]> 26.3 0.10 358 Comparative Example 1 <![CDATA[8.53×10 13 ]]> 18.7 0.13 316 Comparative Example 2 <![CDATA[1.64×10 14 ]]> 22.1 0.12 345 By comparing and analyzing the relevant data in Table 1, it can be seen that the ceramic insulator prepared by this invention is significantly superior to the comparative example in terms of volume resistivity, power frequency breakdown strength, water absorption, and flexural strength. Comparative Example 1, due to the lack of modification of the alumina-based powder and insufficient effective control of grain boundaries, exhibits the worst insulation performance; Comparative Example 2, having only undergone pre-reaction treatment, shows improved performance but still falls short of the examples. This invention introduces sintering activity and rare earth pre-doping into the alumina-based powder through pre-reaction, followed by sol-gel coating to introduce a highly insulating grain boundary phase. This two-stage modification synergistically enhances the grain boundary's ability to impede charge transport. Therefore, this invention's preparation method can effectively improve the insulation performance of ceramic insulators while simultaneously considering density and mechanical reliability.

[0033] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a high-insulation-performance ceramic insulator, characterized in that, Includes the following steps: S1. By weight, mix 3-6 parts of barium carbonate powder with 4.5-12 parts of deionized water to prepare barium carbonate slurry, add 90-110 parts of modified alumina-based powder, and wet ball mill until the particle size D50 is 0.8-1.2 μm to obtain the first slurry; S2. Mix 1-3 parts of Suzhou clay and 1-2 parts of calcined talc powder to obtain a mixed solid. Add deionized water and mix the mixed solid and deionized water at a mass ratio of 1:(1-1.5). Wet ball mill until the particle size D50 is 0.6-1.0 μm to obtain the second slurry. S3. Combine the first slurry and the second slurry, stir and disperse to form a composite slurry, and spray granulate to obtain granulated powder; S4. The granulated powder is dry-pressed under a molding pressure of 100-150 MPa to obtain an insulator blank; S5. The insulator blank is debonded, heated, sintered, and cooled to obtain the insulator ceramic body; S6. Grind the insulator porcelain body, then place the insulator porcelain body in methyl silicone oil at 120-180℃, the amount of methyl silicone oil being 1-2 times the mass of the insulator porcelain body, and impregnate under pressure for 0.5-2 hours; S7. Remove the impregnated ceramic insulator body and dry and cure it at 200-300℃ for 2-4 hours to obtain a ceramic insulator with high insulation performance.

2. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, The modified alumina-based powder is prepared by the following steps: A1. By weight, 100 parts of α-alumina powder are mixed with 5 to 12 parts of boehmite, and 85 to 170 parts of lanthanum nitrate hexahydrate solution with a mass concentration of 1 to 3% are added. The mixture is stirred and ultrasonically dispersed to obtain a slurry, which is then spray-dried and granulated, and pre-sintered to obtain alumina-based pre-reacted powder. A2. Mix the alumina-based pre-reacted powder with anhydrous ethanol, add deionized water and stir until homogeneous to obtain a suspension; A3. Dissolve 1-3 parts of barium acetate and 2-4 parts of titanate coupling agent in 8-12 parts of acetylacetone to obtain a precursor solution. While stirring continuously, drop the precursor solution into the suspension. After the addition is complete, continue stirring to form a gel-like mixture. A4. After drying the gel-like mixture, calcine it at 350–450°C in air to obtain modified alumina-based powder.

3. The method for preparing a high-insulation-performance ceramic insulator according to claim 2, characterized in that, In step A1, the pre-sintering temperature is 1100–1250℃ and the pre-sintering time is 2–4 hours.

4. The method for preparing a high-insulation-performance ceramic insulator according to claim 2, characterized in that, The raw materials in step A2, by weight, include 100 parts of alumina-based pre-reaction powder, 120-230 parts of anhydrous ethanol, and 3-6 parts of deionized water.

5. The method for preparing a high-insulation-performance ceramic insulator according to claim 2, characterized in that, In step A4, the particle size D50 of the modified alumina-based powder is 10–20 μm.

6. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, In step S1, the mass ratio of balls to material during wet ball milling is (2-4):

1.

7. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, In step S3, during the spray granulation process, the inlet temperature of the spray granulation is 200-250℃, and the outlet temperature is 100-120℃.

8. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, In step S4, a bidirectional pressure method is used during dry pressing.

9. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, In step S5, the debinding temperature is 500-600℃, the debinding time is 1-3h, the sintering temperature is 1550-1620℃, the sintering time is 2-4h, and after sintering, the temperature is cooled to 800℃ at a rate of 3-8℃ / min, and then naturally cooled to room temperature.

10. The method for preparing a high-insulation-performance ceramic insulator according to claim 1, characterized in that, The viscosity of the methyl silicone oil in step S6 is 50–200 mPa·s.