Preparation process of self-cleaning high-strength ceramic insulator

Abstract

This invention discloses a preparation process for a self-cleaning high-strength ceramic insulator, relating to the fields of ceramic product manufacturing and electrical insulation materials technology, including the following steps: Step 1: Mixing α-alumina, calcined kaolin, plastic kaolin, feldspar, quartz, zircon, and mullite seed crystals, adding an inorganic composite binding liquid containing boehmite and silica sol, and performing wet ball milling, so that boehmite and silica sol form an aluminum-silica-rich coating layer on the surface of α-alumina and mullite seed crystals, obtaining a high-strength ceramic slurry; Step 2: Spray granulating the high-strength ceramic slurry, aging it, and then molding it to obtain a ceramic insulator blank, and performing drying and low-temperature glue removal treatment on the ceramic insulator blank; by sequentially constructing a high-strength ceramic blank, a phase-separated microcrystalline transition glaze, a weakly acid activated glaze, a phosphorus-zirconium-aluminum inorganic anchoring layer, and a gradient self-cleaning layer, the strength of the ceramic matrix, the glaze bonding, the self-cleaning function, and the durability are integrated and synergistic.

Description

Technical Field

[0001] This invention relates to the fields of ceramic product manufacturing and electrical insulation materials technology, specifically to a preparation process for a self-cleaning high-strength ceramic insulator. Background Technology

[0002] Ceramic insulators are widely used in power transmission lines, substations, and electrical equipment, where they must withstand long-term exposure to complex environments including mechanical tension, electric fields, rainwater erosion, ultraviolet radiation, thermal cycling, and industrial pollution buildup. Traditional porcelain insulators typically rely on a dense glaze to reduce pollution adhesion; however, in coastal salt spray, industrial dust, sandstorms, and humid environments, dirt can still gradually accumulate on the glaze. When the pollution layer encounters moist conditions such as fog, dew, or drizzle, the surface leakage current increases, easily inducing partial discharge or even pollution flashover.

[0003] In existing technologies, silicone rubber coatings, fluorocarbon coatings, conventional TiO2 photocatalytic coatings, or hydrophobic coatings are commonly used to improve the anti-fouling ability of insulator surfaces. However, these solutions still have the following problems: organic coatings are prone to aging and powdering under ultraviolet, ozone, and corona environments, resulting in insufficient long-term weather resistance; conventional TiO2 self-cleaning layers are mostly physically attached to the ceramic glaze, making them prone to detachment after rain, sand and dust abrasion, or thermal cycling; increasing surface roughness or coating thickness may improve self-cleaning performance in the short term, but it may cause stress concentration on the glaze surface, coating cracking, and even affect the mechanical strength and electrical insulation reliability of the insulator; and there is a lack of overall design from the perspectives of material composition, thermal expansion matching, micro-anchoring, and chemical bonding between the ceramic substrate, glaze layer, and self-cleaning layer.

[0004] Therefore, a new ceramic insulator manufacturing process is needed to further improve the bonding strength between the self-cleaning layer and the glaze while maintaining the high mechanical strength and low water absorption of the ceramic body, and to maintain good self-cleaning performance and pollution flashover resistance under long-term pollution and hot and cold cycling environments. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for self-cleaning high-strength ceramic insulators, in order to solve the technical problems of poor bonding between the self-cleaning coating and the glaze surface of existing ceramic insulators, insufficient resistance to erosion and thermal cycling, and the tendency of surface functionalization treatment to weaken the mechanical reliability of ceramic insulators.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing a self-cleaning high-strength ceramic insulator, comprising the following steps: Step 1: Mix α-alumina, calcined kaolin, plastic kaolin, feldspar, quartz, zircon and mullite seed crystals, add an inorganic composite binding liquid containing boehmite and silica sol and perform wet ball milling, so that boehmite and silica sol form an aluminum-silica-rich coating layer on the surface of α-alumina and mullite seed crystals, to obtain high-strength ceramic slurry.

[0007] Step 2: Spray granulation and aging of high-strength ceramic blank slurry to obtain ceramic insulator blanks, followed by drying and low-temperature debinding treatment of the ceramic insulator blanks.

[0008] Step 3: Apply a phase-separated microcrystalline transition glaze to the surface of the ceramic insulator blank. The phase-separated microcrystalline transition glaze contains zircon, titanium dioxide, and cerium oxide as composite crystal nucleus regulating components.

[0009] Step 4: The ceramic insulator blank after applying the phase-separated microcrystalline transition glaze is fired in an oxidizing atmosphere, and segmented heat preservation is carried out during the cooling stage to form a mullite needle crystal-corundum phase reinforcing skeleton inside the ceramic blank, while forming a continuous aluminosilicate phase and a zirconium-titanium microcrystalline dispersed phase on the surface of the transition glaze layer.

[0010] Step 5: The surface of the fired transition glaze layer is subjected to weak acid activation treatment, which causes the low-polymerization degree borosilicate microregions rich in B2O3, alkali metal oxides and alkaline earth metal oxides in the transition glaze layer surface to preferentially undergo ion exchange and limited hydrolysis dissolution, while the continuous phase of aluminosilicate and the dispersed phase of zirconium-titanium microcrystals remain basically stable, thereby forming an activated glaze surface with nano-anchoring pits and surface hydroxyl sites on the glaze layer surface.

[0011] Step 6: Coat the activated glaze surface with an inorganic anchoring primer containing zirconium phosphate sol and aluminum sol, and pre-cur it to form a phosphorus-zirconium-aluminum inorganic anchoring layer.

[0012] Step 7: Combine cerium-modified anatase titanium dioxide sol, silica sol and zirconium sol to obtain titanium dioxide-silica-zirconia composite self-cleaning sol. Spray the composite self-cleaning sol onto the surface of the phosphorus-zirconia-alumina inorganic anchoring layer in multiple layers. After curing and heat treatment, a gradient self-cleaning layer is formed with an outer surface rich in anatase titanium dioxide and an inner side rich in silica-zirconia network, resulting in a self-cleaning high-strength ceramic insulator.

[0013] Furthermore, in step one, the solid raw materials of the high-strength ceramic slurry include, by weight, 30-42 parts of α-alumina, 16-24 parts of calcined kaolin, 8-16 parts of plastic kaolin, 14-22 parts of feldspar, 5-10 parts of quartz, 2-7 parts of zircon, and 0.6-2.5 parts of mullite seed crystals.

[0014] Furthermore, the mullite seed crystal is needle-shaped mullite powder with an aspect ratio of 5-15, the D50 particle size of the α-alumina is 0.8-2.2μm, and the D50 particle size of the zircon is 1.0-3.5μm.

[0015] Furthermore, in the inorganic composite binder containing boehmite and silica sol, the mass ratio of boehmite (calculated as Al2O3) to silica sol (calculated as SiO2) is 1:1.2-3.0; the amount of the inorganic composite binder added (calculated as oxides) is 1.0-3.0% of the total mass of the solid raw materials; and the pH of the slurry is controlled to be 8.5-10.0 during the wet ball milling process.

[0016] Furthermore, in step three, the phase-separated microcrystalline transition glaze slurry includes, by weight percentage of oxides: SiO2 46-56%, Al2O3 12-19%, K2O and Na2O combined 4-8%, CaO and MgO combined 3-7%, B2O3 2-5%, ZrSiO4 8-16%, TiO2 1.5-4.5%, CeO2 0.2-1.2%, and suspended components introduced by clay 4-9%; the content of each oxide is selected under the premise that the total amount is 100%.

[0017] Furthermore, the coefficient of linear expansion of the phase-separated microcrystalline transition glaze slurry after firing is 4.9 × 10⁻ 6 / K-5.9×10⁻ 6 / K, and the difference between the coefficient of linear expansion and the coefficient of linear expansion of the fired porcelain blank is not greater than 0.7×10⁻ 6 / K.

[0018] Furthermore, in step four, the oxidizing atmosphere firing includes the following heating and cooling regime: heating at 40-90℃ / h to 650-750℃ and holding for 1-2h; continuing to heat at 60-110℃ / h to 1240-1290℃ and holding for 2-4h; then cooling to 980-1050℃ and holding for 30-90min; and then cooling to 720-820℃ and holding for 20-60min.

[0019] Furthermore, in step five, the weak acid activation treatment uses a 0.05-0.30 mol / L aqueous solution of citric acid, acetic acid, or oxalic acid, and is treated at 40-70℃ for 5-25 min; after the weak acid activation treatment, it is washed with deionized water until the pH of the washing solution is 6.0-7.5, and then dried at 80-120℃ for 20-60 min.

[0020] Furthermore, the activated glaze after weak acid activation treatment has nano-anchoring pits with a depth of 30-120nm, and the surface hydroxyl content is higher than that of the unactivated glaze.

[0021] Further, in step six, the inorganic anchoring substrate is composed of zirconium phosphate sol, aluminum sol, and silica sol modified with silane coupling agent; wherein the molar ratio of zirconium phosphate sol (calculated as ZrO2), aluminum sol (calculated as Al2O3), and silica sol (calculated as SiO2) is 1:0.3-1.2:1.5-4.0; the inorganic anchoring substrate has a pH of 2.5-4.5 and a solid content of 1.0-5.0 wt%, and after coating, it is pre-cured at 120-180℃ for 10-40 min to form a phosphorus-zirconium-aluminum inorganic anchoring layer with a thickness of 10-50 nm.

[0022] Furthermore, in step seven, the cerium-modified anatase titanium dioxide sol is prepared by hydrolyzing tetrabutyl titanate or isopropyl titanate in an acidic alcohol-water system and adding cerium nitrate or cerium acetate; based on TiO2 and CeO2, CeO2 accounts for 0.3-2.0% of the mass of TiO2.

[0023] Furthermore, in the titanium dioxide-silica-zirconia composite self-cleaning sol, the molar ratio of TiO2, SiO2 and ZrO2 is 1:1.8-4.5:0.08-0.35; the composite self-cleaning sol is used after aging for 6-24 hours, and its solid content is 1.5-6.0 wt%.

[0024] Further, in step seven, the composite self-cleaning sol is coated onto the surface of the ceramic insulator using a rotary spraying method. During spraying, the rotation speed of the ceramic insulator is 30-120 r / min, and the substrate surface temperature is 60-95℃. The composite self-cleaning sol is sprayed at least three times. In the first spray, the total molar amount of SiO2 and ZrO2 in the sol is higher than that of TiO2, forming a densely bonded sublayer. In the last spray, the molar amount of TiO2 in the sol is higher than that of SiO2 and ZrO2, forming a photocatalytic self-cleaning surface layer. After spraying, the sol is heat-treated at 420-500℃ for 30-90 min to make the total thickness of the gradient self-cleaning layer 80-220 nm.

[0025] The present invention also provides a self-cleaning high-strength ceramic insulator prepared by the above-described preparation process. The self-cleaning high-strength ceramic insulator comprises, from the inside out, a high-strength ceramic matrix, a phase-separated microcrystalline transition glaze layer, a phosphorus-zirconia-alumina inorganic anchoring layer, and a titanium dioxide-silica-zirconia gradient self-cleaning layer. The high-strength ceramic matrix contains a mullite needle-corundum phase reinforcing framework, the surface of the phase-separated microcrystalline transition glaze layer has nano-anchoring pits, the phosphorus-zirconia-alumina inorganic anchoring layer is embedded in the nano-anchoring pits, and the gradient self-cleaning layer is bonded to the phosphorus-zirconia-alumina inorganic anchoring layer through at least one of Si-O-Zr bonds, PO-Zr bonds, Al-OP bonds, and Ti-O-Si bonds.

[0026] The "soluble borosilicate phase" described in this invention does not refer to a single crystalline phase, but rather to low-polymerization-degree borosilicate glass microregions rich in B2O3, Na2O, K2O, CaO, and MgO formed on the surface of the phase-separated microcrystalline transition glaze after firing. These microregions contain numerous BOB and BO-Si bonds, as well as non-bridging oxygen structures compensated by alkali metals or alkaline earth metals, and their network connectivity is lower than that of the continuous aluminosilicate phase.

[0027] Under the treatment conditions of 0.05-0.30 mol / L weak organic acid, 40-70℃, and 5-25 min as described in this invention, H⁺ in the weak acid preferentially undergoes ion exchange with the aforementioned low-polymerization-degree borosilicate phase rich in alkali metals or alkaline earth metals, causing network-modified ions such as Na⁺, K⁺, Ca²⁺, and Mg²⁺ to migrate out from the surface layer. At the same time, the BOB and BO-Si bonds in the low-polymerization-degree borate and borosilicate structures are more easily hydrolyzed, thereby causing limited dissolution of the borosilicate-rich microregion.

[0028] In contrast, the continuous aluminosilicate phase in the phase-separated microcrystalline transition glaze is mainly composed of Si-O-Si and Si-O-Al networks with a high degree of network cross-linking. Simultaneously, the precipitated zirconium-titanium microcrystalline phase and the residual zircon phase in the transition glaze exhibit good chemical stability under the aforementioned weak acid, low temperature, and short-time conditions. Therefore, within the weak acid concentration, processing temperature, and processing time specified in this invention, the weak acid primarily acts on the surface boron-rich silicon microregions without significantly damaging the continuous aluminosilicate phase and the dispersed zirconium-titanium microcrystalline phase.

[0029] The above process is a limited dissolution process controlled by surface kinetics. If the weak acid activation time is too short, insufficient dissolution of the boron-rich silicon microregions will occur, making it difficult to form effective nano-anchoring pits. If the weak acid activation time is too long or the acid concentration is too high, excessive corrosion may occur on the glaze surface, leading to excessive glaze roughness or microcracks. Therefore, this invention limits the weak acid concentration to 0.05-0.30 mol / L, the processing temperature to 40-70℃, and the processing time to 5-25 min, in order to achieve a balance between forming nano-anchoring pits and maintaining the integrity of the glaze layer.

[0030] Through this weak acid activation treatment, nano-anchoring pits with a depth of 30-120 nm are formed on the surface of the transition glaze layer, exposing numerous surface hydroxyl sites such as Si-OH, Al-OH, and Zr-OH. These nano-anchoring pits provide mechanical intercalation sites for the subsequent inorganic anchoring layer of zirconium-aluminum phosphate. The surface hydroxyl sites can undergo condensation reactions with zirconium phosphate sol, aluminum sol, and silica sol, thereby forming inorganic bonded structures such as PO-Zr, Al-OP, Si-O-Zr, and Si-O-Si.

[0031] Compared with the prior art, the present invention provides a preparation process for a self-cleaning high-strength ceramic insulator, which has the following beneficial effects: by sequentially constructing a high-strength ceramic blank, a phase-separated microcrystalline transition glaze, a weak acid activated glaze, a phosphorus-zirconium-aluminum inorganic anchoring layer, and a gradient self-cleaning layer, the strength of the ceramic matrix, the bonding of the glaze layer, the self-cleaning function, and the durability are integrated and synergistic.

[0032] Introducing α-alumina, zircon, and mullite seed crystals into the ceramic blank, along with a pseudo-boehmite-silica sol composite binder, allows for the formation of a mullite needle-corundum phase reinforcing framework during firing. This structure improves the mechanical failure load of ceramic insulators and reduces strength fluctuations caused by the introduction of multilayer surface structures.

[0033] The Ming dynasty employed a phase-separated microcrystalline transition glaze containing zircon, titanium dioxide, and cerium oxide, and used segmented heat preservation during the cooling stage to form a continuous aluminosilicate phase and a dispersed zircon-titanium microcrystalline phase on the surface of the transition glaze. This transition glaze not only matches the thermal expansion of the ceramic body but also provides a controllable phase-separated structure for subsequent weak acid activation, avoiding a decrease in glaze strength caused by direct strong acid corrosion.

[0034] The soluble borosilicate phase on the surface of the transition glaze is selectively dissolved by weak acid activation, forming nano-anchoring pits and hydroxyl active sites on the glaze surface; then, an inorganic anchoring layer of phosphorus zirconium aluminum is introduced, so that the anchoring layer is embedded in the nano-pits to form mechanical locking, and the interlayer bonding force is improved by inorganic bonding such as PO-Zr, Al-OP, and Si-O-Zr.

[0035] In the gradient self-cleaning layer of this invention, the inner side is rich in a silica-zirconia network, which enhances the inorganic bonding and wear resistance with the anchoring layer; the outer side is rich in cerium-modified anatase titanium dioxide, which improves the photocatalytic self-cleaning ability. This gradient structure balances bonding strength, wear resistance, and surface self-cleaning activity, and is superior to a single uniform TiO2 coating. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope image of the cross-section of the high-strength ceramic matrix in Embodiment 2 of the present invention.

[0037] Figure 2 This is an atomic force microscope image of the three-dimensional morphology of the phase-separated microcrystalline transition glaze after weak acid activation in Example 2 of the present invention.

[0038] Figure 3 This is a cross-sectional transmission electron microscope image of the phase-separated microcrystalline transition glaze layer, the phosphorus-zirconium-aluminum inorganic anchoring layer, and the gradient self-cleaning layer in Embodiment 2 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Conventional adjustments made by those skilled in the art to the raw material particle size, glazing method, spraying equipment and drying method without departing from the concept of the present invention should all fall within the protection scope of the present invention.

[0040] Please see Figures 1-3 This invention provides a technical solution for the preparation process of self-cleaning high-strength ceramic insulators: Figure 1 As can be seen, the cross-section of the high-strength ceramic matrix in Example 2 is relatively dense with few pores. Needle-shaped mullite crystals are interspersed among the corundum phase particles, forming a continuous framework structure together with the bonding phase. Some mullite crystals are bridged between adjacent particles, which helps to suppress crack propagation and improve the mechanical strength of the ceramic matrix. The corundum phase particles, as the main load-bearing phase, are dispersed in the matrix, while the glassy phase or bonding phase is distributed in the intergranular spaces, which helps to promote sintering densification and the connection between the reinforcing phases.

[0041] Figure 2 The raised areas in the figure represent glaze microcrystals, continuous aluminosilicate phases, or surface protrusions that have not been dissolved; the low-lying areas in the figure represent nano-pits or local micro-depressions formed after weak acid activation; the height color scale on the side of the figure represents the surface height range corresponding to different colors or gray levels; the mark "D" indicates the selection of a typical nano-pit for depth measurement; the mark "L" indicates the height profile line passing through the typical nano-pit; if the profile curve is displayed in the figure, the horizontal axis of the profile curve represents the horizontal distance along the L line, and the vertical axis represents the surface height at the corresponding position.

[0042] Depend on Figure 2 As can be seen, the phase-separated microcrystalline transition glaze after weak acid activation in Example 2 formed relatively uniformly distributed nanoscale pits. The pits were separated by a continuous glaze framework and microcrystalline regions, and no large-area through cracks or obvious flaking were observed. Through height profile analysis of typical pits, it can be determined that their depth is within the range of 30-120 nm described in this invention. The weak acid activation conditions used in Example 2 can selectively dissolve the relatively soluble borosilicate phase in the transition glaze surface while retaining the main aluminosilicate continuous phase and microcrystalline framework, thereby forming a nano-anchoring structure for subsequent inorganic anchoring layer embedding without excessively damaging the integrity of the glaze layer.

[0043] Figure 3The meanings of the markings are as follows: "PG" represents the phase-separated microcrystalline transition glaze layer; "NA" represents the nano-anchoring pits on the transition glaze surface after weak acid activation; "PZA" represents the phosphorus zirconium aluminum inorganic anchoring layer; "GSC" represents the titanium dioxide-silica-zirconia gradient self-cleaning layer; "ER" represents the epoxy resin area used to protect the surface layer during sample preparation; arrow "I1" represents the interface between the phase-separated microcrystalline transition glaze layer and the phosphorus zirconium aluminum inorganic anchoring layer; arrow "I2" represents the interface between the phosphorus zirconium aluminum inorganic anchoring layer and the gradient self-cleaning layer; bidirectional dimension arrow "T1" represents the local thickness of the phosphorus zirconium aluminum inorganic anchoring layer; bidirectional dimension arrow "T2" represents the local thickness of the gradient self-cleaning layer.

[0044] Depend on Figure 3 As can be seen, the gradient self-cleaning layer in Example 2 is continuously distributed along the transition glaze surface, with a relatively uniform overall thickness, and no obvious through cracks, large-area peeling, or continuous interface pores are observed. The phosphorus-zirconium-aluminum inorganic anchoring layer is located between the phase-separated microcrystalline transition glaze layer and the gradient self-cleaning layer, and locally enters the nano-pits formed by weak acid activation, giving the interface a certain degree of uneven interlocking structure. This morphology indicates that the phosphorus-zirconium-aluminum inorganic anchoring layer not only covers the activated glaze surface, but also fills or embeds some of the nano-anchoring pits, thereby forming a mechanically locked interface between the transition glaze layer and the gradient self-cleaning layer.

[0045] Figure 3 Furthermore, it can be shown that the interface between the phosphorus-zirconium-aluminum inorganic anchoring layer and the gradient self-cleaning layer is continuous and tightly bonded, with no obvious straight debonding gaps. This indicates that the nano-pits formed by weak acid activation and the phosphorus-zirconium-aluminum inorganic anchoring layer are beneficial to improving the interlayer bonding stability.

[0046] In the following embodiments, all "parts" refer to parts by weight; unless otherwise specified, the water used is deionized water, and all raw materials used are commercially available industrial or ceramic grade raw materials.

[0047] Example 1: A process for preparing a self-cleaning high-strength ceramic insulator, comprising the following steps: S1: Mix 30 parts α-alumina, 16 parts calcined kaolin, 8 parts plastic kaolin, 14 parts feldspar, 5 parts quartz, 2 parts zircon, and 0.6 parts mullite seed crystals. The α-alumina D50 particle size is 0.8 μm, the zircon D50 particle size is 1.0 μm, and the mullite seed crystal aspect ratio is 5. Add an inorganic composite binder containing boehmite and silica sol. The mass ratio of boehmite (Al2O3) to silica sol (SiO2) is 1:1.2, and the amount of inorganic composite binder (oxides) added is 1.0% of the total mass of solid raw materials. Adjust the pH of the slurry to 8.5, and wet ball mill to obtain a high-strength ceramic blank slurry.

[0048] S2: High-strength ceramic blank slurry is spray-granulated, and the granules are aged for 12 hours before being isostatically pressed at a pressure of 120 MPa for 60 seconds to obtain ceramic insulator blanks. The blanks are dried until the moisture content is less than 0.8 wt%, and then debinded at 300℃ for 1 hour.

[0049] S3: Apply a phase-separated microcrystalline transition glaze to the surface of the ceramic insulator blank. The phase-separated microcrystalline transition glaze, by weight percentage of oxides, is as follows: SiO2 56.0%, Al2O3 12.0%, K2O and Na2O combined 4.0%, CaO and MgO combined 3.0%, B2O3 2.0%, ZrSiO4 16.0%, TiO2 1.5%, CeO2 0.2%, and suspended components introduced from clay 5.3%. The dry glaze layer thickness after glazing is 80μm.

[0050] S4: Firing the glazed blank in an oxidizing atmosphere: heating to 650℃ at 40℃ / h and holding for 1h, then heating to 1240℃ at 60℃ / h and holding for 2h, then cooling to 980℃ and holding for 30min, then cooling to 720℃ and holding for 20min, followed by natural cooling to obtain a high-strength glazed ceramic insulator substrate.

[0051] S5: Use 0.05mol / L citric acid aqueous solution to treat the surface of the transition glaze layer after firing at 40℃ for 5min, wash with deionized water until the pH of the cleaning solution is 6.0, and then dry at 80℃ for 20min to form an activated glaze surface.

[0052] S6: Apply an inorganic anchoring primer to the activated glaze surface. The inorganic anchoring primer consists of zirconium phosphate sol, aluminum sol, and silica sol modified with a silane coupling agent. The molar ratio of zirconium phosphate sol (calculated as ZrO2), aluminum sol (calculated as Al2O3), and silica sol (calculated as SiO2) is 1:0.3:1.5, the pH is 2.5, and the solid content is 1.0 wt%. After coating, pre-cur at 120℃ for 10 min to form a zirconium phosphate aluminum inorganic anchoring layer.

[0053] S7: Using tetrabutyl titanate as the titanium source, hydrolysis was performed in an acidic alcohol-water system, and cerium nitrate was added to obtain cerium-modified anatase titanium dioxide sol; based on TiO2 and CeO2, CeO2 accounted for 0.3% of the mass of TiO2. The cerium-modified anatase titanium dioxide sol, silica sol, and zirconium sol were compounded to achieve a molar ratio of TiO2, SiO2, and ZrO2 of 1:1.8:0.08 and a solid content of 1.5wt%. After aging for 6 hours, it was used. Spin coating was applied using a rotary spraying method at a ceramic insulator rotation speed of 30 r / min and a substrate surface temperature of 60℃. The coating was applied in three stages, followed by heat treatment at 420℃ for 30 min to form a gradient self-cleaning layer with a thickness of 80 nm, resulting in a self-cleaning high-strength ceramic insulator.

[0054] Example 2: A process for preparing a self-cleaning high-strength ceramic insulator, comprising the following steps:

[0055] S1: Mix 36 parts α-alumina, 20 parts calcined kaolin, 12 parts plastic kaolin, 18 parts feldspar, 7.5 parts quartz, 4.5 parts zircon, and 1.5 parts mullite seed crystals, wherein the α-alumina D50 particle size is 1.5 μm, the zircon D50 particle size is 2.2 μm, and the mullite seed crystal aspect ratio is 10. Add an inorganic composite binder containing boehmite and silica sol, wherein the mass ratio of boehmite (based on Al2O3) to silica sol (based on SiO2) is 1:2.1, and the amount of inorganic composite binder added (based on oxides) is 2.0% of the total mass of solid raw materials. Adjust the pH of the slurry to 9.2, and wet ball mill to obtain a high-strength ceramic blank slurry.

[0056] S2: High-strength ceramic blank slurry is spray-granulated, and the granules are aged for 24 hours before being isostatically pressed at a pressure of 160 MPa for 120 seconds to obtain ceramic insulator blanks. The blanks are dried until the moisture content is less than 0.8 wt%, and then debinded at 380℃ for 2 hours.

[0057] S3: Apply a phase-separated microcrystalline transition glaze to the surface of the ceramic insulator blank. The phase-separated microcrystalline transition glaze, by weight percentage of oxides, is as follows: SiO2 48.0%, Al2O3 16.0%, K2O and Na2O combined 6.0%, CaO and MgO combined 5.0%, B2O3 3.0%, ZrSiO4 12.0%, TiO2 3.0%, CeO2 0.8%, and 6.2% suspended components introduced from clay. The dry glaze layer thickness after glazing is 120μm.

[0058] S4: Firing the glazed blank in an oxidizing atmosphere: heating to 700℃ at 65℃ / h and holding for 1.5h, then heating to 1265℃ at 85℃ / h and holding for 3h, then cooling to 1015℃ and holding for 60min, then cooling to 770℃ and holding for 40min, followed by natural cooling to obtain a high-strength glazed ceramic insulator substrate.

[0059] S5: Use 0.15mol / L citric acid aqueous solution to treat the surface of the fired transition glaze layer for 15min at 55℃, wash with deionized water until the pH of the cleaning solution is 6.8, and then dry at 100℃ for 40min to form an activated glaze surface.

[0060] S6: Apply an inorganic anchoring primer to the activated glaze surface. The inorganic anchoring primer consists of zirconium phosphate sol, aluminum sol, and silica sol modified with a silane coupling agent. The molar ratio of zirconium phosphate sol (calculated as ZrO2), aluminum sol (calculated as Al2O3), and silica sol (calculated as SiO2) is 1:0.8:2.8, the pH is 3.5, and the solid content is 3.0 wt%. After coating, pre-cur at 150℃ for 25 min to form a zirconium phosphate aluminum inorganic anchoring layer.

[0061] S7: Using tetrabutyl titanate as the titanium source, hydrolysis was performed in an acidic alcohol-water system, and cerium nitrate was added to obtain cerium-modified anatase titanium dioxide sol; based on TiO2 and CeO2, CeO2 accounted for 1.1% of the mass of TiO2. The cerium-modified anatase titanium dioxide sol, silica sol, and zirconium sol were compounded to achieve a molar ratio of TiO2, SiO2, and ZrO2 of 1:3.0:0.20, with a solid content of 3.5 wt%. After aging for 15 hours, it was used. Spin coating was applied using a rotary spraying method at a ceramic insulator rotation speed of 75 r / min and a substrate surface temperature of 78℃. The coating was applied in three stages. In the first spray, the total molar amount of SiO2 and ZrO2 in the sol was higher than the molar amount of TiO2, and in the last spray, the molar amount of TiO2 in the sol was higher than the total molar amount of SiO2 and ZrO2. After spraying, the coating is heat-treated at 460℃ for 60 minutes to form a gradient self-cleaning layer with a thickness of 150nm, resulting in a self-cleaning high-strength ceramic insulator.

[0062] Example 3: A process for preparing a self-cleaning high-strength ceramic insulator, comprising the following steps: S1: A mixture of 42 parts α-alumina, 24 parts calcined kaolin, 16 parts plastic kaolin, 22 parts feldspar, 10 parts quartz, 7 parts zircon, and 2.5 parts mullite seed crystals was prepared. The α-alumina D50 particle size was 2.2 μm, the zircon D50 particle size was 3.5 μm, and the mullite seed crystal aspect ratio was 15. An inorganic composite binder containing boehmite and silica sol was added. The mass ratio of boehmite (Al2O3) to silica sol (SiO2) was 1:3.0, and the amount of the inorganic composite binder (oxides) added was 3.0% of the total mass of the solid raw materials. The pH of the slurry was adjusted to 10.0, and the mixture was wet-milled to obtain a high-strength ceramic blank slurry.

[0063] S2: High-strength ceramic blank slurry is spray-granulated, and the granules are aged for 36 hours before being isostatically pressed at a pressure of 200 MPa for 180 seconds to obtain ceramic insulator blanks. The blanks are dried until the moisture content is less than 0.8 wt%, and then debinded at 450℃ for 3 hours.

[0064] S3: Apply a phase-separated microcrystalline transition glaze to the surface of the ceramic insulator blank. The phase-separated microcrystalline transition glaze, by weight percentage of oxides, is as follows: SiO2 46.0%, Al2O3 19.0%, K2O and Na2O combined 8.0%, CaO and MgO combined 4.0%, B2O3 3.0%, ZrSiO4 8.0%, TiO2 4.0%, CeO2 1.0%, and suspended components introduced from clay 7.0%. The dry glaze layer thickness after glazing is 160μm.

[0065] S4: Firing the glazed blank in an oxidizing atmosphere: heating to 750℃ at 90℃ / h and holding for 2h, then heating to 1290℃ at 110℃ / h and holding for 4h, then cooling to 1050℃ and holding for 90min, then cooling to 820℃ and holding for 60min, followed by natural cooling to obtain a high-strength glazed ceramic insulator substrate.

[0066] S5: Use 0.30mol / L citric acid aqueous solution to treat the surface of the fired transition glaze layer for 25min at 70℃, wash with deionized water until the pH of the cleaning solution is 7.5, and then dry at 120℃ for 60min to form an activated glaze surface.

[0067] S6: Apply an inorganic anchoring primer to the activated glaze surface. The inorganic anchoring primer consists of zirconium phosphate sol, aluminum sol, and silica sol modified with a silane coupling agent. The molar ratio of zirconium phosphate sol (calculated as ZrO2), aluminum sol (calculated as Al2O3), and silica sol (calculated as SiO2) is 1:1.2:4.0, the pH is 4.5, and the solid content is 5.0 wt%. After coating, pre-cur at 180℃ for 40 min to form a zirconium phosphate aluminum inorganic anchoring layer.

[0068] S7: Using isopropyl titanate as the titanium source, hydrolysis was performed in an acidic alcohol-water system, and cerium acetate was added to obtain cerium-modified anatase titanium dioxide sol; based on TiO2 and CeO2, CeO2 accounted for 2.0% of the TiO2 mass. The cerium-modified anatase titanium dioxide sol, silica sol, and zirconium sol were compounded to achieve a molar ratio of TiO2, SiO2, and ZrO2 of 1:4.5:0.35, with a solid content of 6.0 wt%. After aging for 24 hours, it was used. Spin coating was applied using a rotary spraying method at a ceramic insulator rotation speed of 120 r / min and a substrate surface temperature of 95℃, with five spraying passes. After spraying, heat treatment was performed at 500℃ for 90 min to form a gradient self-cleaning layer with a thickness of 220 nm, resulting in a self-cleaning high-strength ceramic insulator.

[0069] Comparative Example 1 differs from Example 2 only in that the weak acid activation treatment in step S5 is omitted, and the surface of the transition glaze layer after firing is not treated with citric acid, but directly coated with the inorganic anchoring base liquid in step S6. All other raw materials, proportions, firing regime, self-cleaning layer composition, and heat treatment conditions are the same as in Example 2.

[0070] Comparative Example 2 differs from Example 2 only in that the phosphorus-zirconium-aluminum inorganic anchoring layer in step S6 is omitted, and the titanium dioxide-silica-zirconia composite self-cleaning sol is directly sprayed onto the glaze surface after weak acid activation. All other conditions are the same as in Example 2.

[0071] Comparative Example 3 differs from Example 2 only in that gradient spraying is not used in step S7. Instead, TiO2, SiO2, and ZrO2 are mixed in the same total molar ratio as in Example 2 to form a uniform composite self-cleaning sol in one step, and then sprayed in one step to form a uniform self-cleaning layer. All other conditions are the same as in Example 2.

[0072] Comparative Example 4 differs from Example 2 only in that the firing and cooling stage in step S4 does not involve segmented holding at 1015°C and 770°C, but instead involves direct cooling with the furnace after holding at 1265°C. All other raw materials, glaze composition, weak acid activation, inorganic anchoring layer, and self-cleaning layer are the same as in Example 2.

[0073] Comparative Example 5 differs from Example 2 only in that: in step S1, the inorganic composite binder containing boehmite and silica sol is not added, and only deionized water and conventional dispersants are used for wet ball milling. All other conditions are the same as in Example 2.

[0074] Performance testing methods 1. Mechanical destructive load test: Conducted in accordance with GB / T 1001.1-2021, which defines, tests, and judges porcelain or glass insulators for AC systems with nominal voltages above 1000V, and is currently in effect. Five 70kN-class ceramic insulators of the same specification were used for testing, and the average value was taken from each group.

[0075] 2. Water absorption test: The water absorption rate of fired porcelain was determined according to GB / T 3299-2011, which remains valid after review in 2025. Three pieces of fired porcelain from the same batch were taken for each group, and the average value was measured.

[0076] 3. Coating pull-off adhesion test: The pull-off adhesion test shall be conducted in accordance with GB / T 5210-2006, which is currently valid and was approved for continued validity in the 2023 review. The test shall assess initial adhesion and adhesion after thermal cycling.

[0077] 4. Thermal cycling treatment: Temperature change test was conducted in accordance with GB / T 2423.22-2012, which is currently in effect. In this test, a cycle was defined as holding at -40℃ for 30 minutes and then at 85℃ for 30 minutes, for a total of 100 cycles.

[0078] 5. Abrasion Resistance Treatment: Abrasion resistance was tested using the rotating rubber grinding wheel method according to GB / T 1768-2006. This standard is currently valid, and the 2023 review concluded that it remains valid. This test is used to evaluate the mass loss and adhesion retention ability of the self-cleaning layer after abrasion by sand and dust.

[0079] 6. Photocatalytic self-cleaning performance test: The test was conducted in accordance with GB / T 23764-2009, which is a test method for the performance of photocatalytic self-cleaning materials and is currently valid. Oleic acid contaminants were attached to the sample surface, and the change in water contact angle was measured after ultraviolet irradiation. The lower the water contact angle, the stronger the hydrophilicity recovery ability of the surface after photocatalytic cleaning.

[0080] 7. Artificial Pollution Flashover Performance Test: The test shall be conducted in accordance with GB / T 4585-2024, which is the standard for artificial pollution testing of high-voltage porcelain and glass insulators for AC systems. It was implemented on January 1, 2025, and supersedes GB / T 4585-2004. Artificial pollution treatment shall be performed under the same salt density and ash density conditions, and the pollution flashover voltage under humid conditions shall be tested.

[0081] 8. Determination of linear expansion coefficient: The linear expansion coefficient of the ceramic matrix and the fired transition glaze was determined using a push-rod thermal dilatometer. Ceramic matrix samples were cut from the fired ceramic body, while transition glaze samples were prepared by separately melting and firing the same transition glaze slurry into strip-shaped samples. The test was conducted according to GB / T 16535-2008 "Test Method for Linear Thermal Expansion Coefficient of Fine Ceramics - Push-rod Method," which is currently a valid standard applicable to the determination of the linear thermal expansion rate and coefficient of linear thermal expansion of bulk fine ceramics.

[0082] Before testing, the sample surface was ground smooth, cleaned, and dried. The test temperature range was from room temperature to 500℃, with a heating rate of 5℃ / min. Three parallel samples were tested in each group, and the average value was taken. The difference between the linear expansion coefficient of the phase-separated microcrystalline transition glaze slurry after firing and the linear expansion coefficient of the fired ceramic blank was measured using the above method.

[0083] 9. Determination of Nano-Anchoring Pits Depth: The depth of nano-anchoring pits was determined using atomic force microscopy. During testing, the glaze sample activated with weak acid was cut into small pieces approximately 10 mm × 10 mm, washed sequentially with deionized water and anhydrous ethanol, dried, and then fixed onto the sample stage. Testing was conducted using either a tapping mode or a non-contact mode, with a scanning range of 2 μm × 2 μm or 5 μm × 5 μm. At least five regions were randomly selected from each sample.

[0084] Before testing, the probe status and scanning system should be calibrated; when nanostructure measurements are involved, refer to GB / T45770-2025 for probe profile characterization requirements for atomic force microscopy used for nanostructure measurements.

[0085] The depth of the nano-anchoring pit is calculated based on the difference between the average height of the pit edge platform and the average height of the pit bottom in the AFM height map. At least 20 pits are selected for each field of view for statistical analysis, and the average value is taken as the depth of the nano-anchoring pit of the sample.

[0086] 10. Determination of surface hydroxyl content: When determining the surface hydroxyl content using X-ray photoelectron spectroscopy, the test method can refer to GB / T 19500-2025 "General Rules for X-ray Photoelectron Spectroscopy Analysis Methods for Surface Chemical Analysis", which is a general rule for XPS analysis methods.

[0087] During testing, high-resolution O 1s spectra were acquired, and peak fitting was performed on the O 1s peak. The ratio of the peak area corresponding to the surface hydroxyl oxygen to the total peak area of ​​O 1s was recorded as the relative content of surface hydroxyl groups. When using Fourier transform infrared spectroscopy, the absorption peaks of hydroxyl stretching vibrations in the range of 3200-3700 cm⁻¹ were recorded and normalized to the Si-O-Si or Si-O-Al framework vibration peaks to calculate the relative area of ​​the hydroxyl peaks. The surface hydroxyl content of the activated glaze was compared with that of the unactivated glaze under the same testing conditions.

[0088] Table 1 Test Results Example 1 92.8 0.11 6.3 8.6 7.8 75.4 Example 2 97.5 0.08 6.9 7.5 5.1 78.6 Example 3 94.1 0.10 6.5 8.1 6.0 76.9 Comparative Example 1 97.0 0.08 4.1 11.8 5.9 70.8 Comparative Example 2 96.8 0.09 2.6 15.6 5.4 68.2 Comparative Example 3 97.2 0.08 5.0 12.4 14.9 65.5 Comparative Example 4 96.9 0.09 4.6 13.1 6.3 71.2 Comparative Example 5 80.6 0.18 6.7 8.0 5.3 77.4 As shown in Table 1, Comparative Example 1, which did not undergo weak acid activation treatment, had ceramic body strength and initial self-cleaning ability similar to Example 2. However, its adhesion after thermal cycling decreased from 6.9 MPa in Example 2 to 4.1 MPa, its wear-resistant mass loss increased from 7.5 mg to 11.8 mg, and its artificial contamination flashover voltage decreased from 78.6 kV to 70.8 kV. These results indicate that the nano-anchoring pits and surface hydroxyl groups formed by weak acid activation are not optional surface treatments, but rather key technical means to improve the bonding strength and long-term durability of subsequent anchoring layers.

[0089] In Comparative Example 2, omitting the phosphorus-zirconium-aluminum inorganic anchoring layer, the adhesion after thermal cycling was only 2.6 MPa, the wear-resistant mass loss increased to 15.6 mg, and the artificial contamination flashover voltage decreased to 68.2 kV. These results indicate that directly coating the activated glaze surface with self-cleaning sol cannot adequately resist thermal cycling and abrasion. The phosphorus-zirconium-aluminum inorganic anchoring layer can form a mechanical interlocking effect within the nano-pits and enhance interfacial stability through inorganic bonding.

[0090] Comparative Example 3, which did not employ a gradient self-cleaning layer but instead used a uniform self-cleaning layer, exhibited lower adhesion and wear resistance after thermal cycling compared to Example 2. Furthermore, its water contact angle after light exposure was 14.9°, significantly higher than Example 2's 5.1°. This demonstrates that simply and uniformly mixing TiO2, SiO2, and ZrO2 cannot simultaneously achieve both surface photocatalytic activity and underlying bonding strength. The gradient self-cleaning layer of this invention, through its structural design of an inner layer rich in SiO2-ZrO2 network and an outer layer rich in cerium-modified TiO2, achieves a balance between bonding strength and self-cleaning activity.

[0091] In Comparative Example 4, after eliminating the segmented heat preservation during the cooling stage, although the mechanical damage load on the ceramic body did not decrease significantly, the adhesion decreased to 4.6 MPa after thermal cycling, and the wear-resistant mass loss increased to 13.1 mg. These results indicate that segmented heat preservation during the cooling stage can promote the precipitation of microcrystals and the differentiation of microphases on the surface of the transition glaze layer, providing a foundation for the subsequent weak acid activation to form a stable nano-anchored structure.

[0092] Comparative Example 5, without the addition of the pseudo-boehmite-silica sol composite binder, still exhibited good adhesion and self-cleaning properties after thermal cycling, but its mechanical breaking load decreased from 97.5 kN in Example 2 to 80.6 kN, and its water absorption rate increased to 0.18%. These results indicate that the composite binder promotes the transformation of the aluminum-rich silica coating layer into a mullite bridging structure during the ceramic blank firing process, which is beneficial for forming a mullite needle-corundum phase reinforcing skeleton, thereby improving the bulk strength of the ceramic insulator.

[0093] Table 2 Example 2 68 31.6 0.042 0.031 Comparative Example 1 9 14.8 0.086 0.074 As shown in Table 2, compared with the unactivated glaze of Comparative Example 1, the average depth of the nano-pits in the weakly acid-activated glaze of Example 2 increased from 9 nm to 68 nm, and the relative content of surface hydroxyl groups increased from 14.8% to 31.6%. Simultaneously, the surface B / Si atomic ratio and Na+K / Si atomic ratio decreased significantly. These results indicate that weakly acid activation treatment can preferentially remove low-polymerization borosilicate microregions rich in boron and alkali metals from the surface of the transition glaze layer, and form nano-anchoring pits and hydroxyl active sites on the glaze surface.

[0094] Figure 1 Small samples were taken from the ceramic body of the ceramic insulator after firing in Example 2, using a diamond cutting blade. After ultrasonic cleaning with anhydrous ethanol and drying, fresh cross-sections were obtained by mechanical crushing, and the cross-sections were then sputtered with gold for conductivity. Observation was performed using a scanning electron microscope under room temperature vacuum conditions. The accelerating voltage was 10-15 kV, the working distance was 8-12 mm, and images were acquired using secondary electron imaging at a magnification of 5000x. The scale bar in the figure is 2 μm. In the figure, M represents mullite needle crystals, A represents corundum phase particles, G represents glassy phase or aluminosilicate-bound phase, and P represents a small number of closed pores. Figure 1 As can be seen, the cross-section of the ceramic matrix in Example 2 is relatively dense overall, with needle-like mullite crystals interspersed between the corundum phase particles and the glass phase, forming a continuous bridging reinforcement structure. This indicates that the high-strength ceramic blank of Example 2 formed a mullite needle-corundum phase reinforcement framework after firing. This structure is beneficial for improving the mechanical strength of the ceramic matrix and reducing the water absorption rate of the ceramic body.

[0095] In summary, the inventiveness of this invention does not stem from the sole use of TiO2 self-cleaning material, nor from simply increasing the roughness of the glaze surface, but rather from the following synergistic structure: the high-strength ceramic blank provides the mechanical foundation, the phase-separated microcrystalline transition glaze provides a controllable activation interface, weak acid activation provides nano-anchoring pits and surface hydroxyl groups, the phosphorus-zirconium-aluminum anchoring layer provides inorganic bonding and mechanical interlocking, and the gradient self-cleaning layer provides a wear-resistant bonding sublayer and a highly active self-cleaning surface layer. These structures are interconnected and functionally supportive, simultaneously improving mechanical strength, coating adhesion, wear resistance, thermal cycling resistance, self-cleaning performance, and dirt flashover tolerance.

Claims

1. A manufacturing process for a self-cleaning high-strength ceramic insulator, characterized in that, The steps include the following: α-alumina, calcined kaolin, plastic kaolin, feldspar, quartz, zircon and mullite seed crystals are mixed and then an inorganic composite binding liquid containing boehmite and silica sol is added for wet ball milling, so that the boehmite and silica sol form an aluminum-silica-rich coating layer on the surface of α-alumina and mullite seed crystals, to obtain a high-strength ceramic slurry. High-strength ceramic blank slurry is spray-granulated, aged, and then molded to obtain ceramic insulator blanks. The ceramic insulator blanks are then dried and subjected to low-temperature debinding treatment. A phase-separated microcrystalline transition glaze is applied to the surface of a ceramic insulator blank. The phase-separated microcrystalline transition glaze contains zircon, titanium dioxide and cerium oxide as composite crystal nuclei regulating components. The ceramic insulator blank after being coated with phase-separated microcrystalline transition glaze is fired in an oxidizing atmosphere and then subjected to segmented heat preservation during the cooling stage. This process forms a mullite needle-corundum phase reinforcing skeleton inside the ceramic blank, while simultaneously forming a continuous aluminosilicate phase and a zirconium-titanium microcrystalline dispersed phase on the surface of the transition glaze layer. The surface of the transition glaze layer after firing is activated by weak acid, so that the soluble borosilicate phase in the surface of the transition glaze layer is selectively dissolved, forming an activated glaze surface with nano-anchoring pits and surface hydroxyl groups. An inorganic anchoring base liquid containing zirconium phosphate sol and aluminum sol is coated on the activated glaze surface, and a phosphorus-zirconium-aluminum inorganic anchoring layer is formed after pre-curing. Cerium-modified anatase titanium dioxide sol, silica sol, and zirconium sol are compounded to obtain a titanium dioxide-silica-zirconia composite self-cleaning sol. The composite self-cleaning sol is sprayed onto the surface of the phosphorus-zirconia-alumina inorganic anchoring layer in multiple stages. After curing and heat treatment, a gradient self-cleaning layer is formed with an anatase titanium dioxide on the outer surface and a silica-zirconia network on the inner side, resulting in a self-cleaning high-strength ceramic insulator.

2. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The solid raw materials of the high-strength ceramic slurry include, by weight: 30-42 parts α-alumina, 16-24 parts calcined kaolin, 8-16 parts plastic kaolin, 14-22 parts feldspar, 5-10 parts quartz, 2-7 parts zircon, and 0.6-2.5 parts mullite seed crystals. The mullite seed crystals are needle-shaped mullite powders with an aspect ratio of 5-15, the α-alumina has a D50 particle size of 0.8-2.2 μm, and the zircon has a D50 particle size of 1.0-3.5 μm.

3. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, In the inorganic composite binder containing boehmite and silica sol, the mass ratio of boehmite (calculated as Al2O3) to silica sol (calculated as SiO2) is 1:1.2-3.

0. The inorganic composite binder is added at an amount of 1.0-3.0% of the total mass of the solid raw materials, calculated as oxides. During the wet ball milling process, the pH of the slurry is controlled at 8.5-10.0, so that boehmite and silica sol are co-deposited on the surface of α-alumina and mullite seed crystals. After firing, a mullite bridging structure is formed between the corundum phase and the glass phase.

4. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The phase-separated microcrystalline transition glaze slurry comprises, by weight percentage of oxides: SiO2 46-56%, Al2O3 12-19%, K2O and Na2O combined 4-8%, CaO and MgO combined 3-7%, B2O3 2-5%, ZrSiO4 8-16%, TiO2 1.5-4.5%, CeO2 0.2-1.2%, and a suspension component introduced by clay 4-9%. The coefficient of linear expansion of the phase-separated microcrystalline transition glaze slurry after firing is 4.9 × 10⁻ 6 / K-5.9×10⁻ 6 / K, and the difference between the coefficient of linear expansion and the coefficient of linear expansion of the fired porcelain blank is not greater than 0.7×10⁻ 6 / K.

5. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The oxidizing atmosphere firing process includes the following heating and cooling procedures: Heat to 650-750℃ at a rate of 40-90℃ / h and hold for 1-2 hours; Continue to raise the temperature to 1240-1290℃ at a rate of 60-110℃ / h and hold for 2-4 hours; Then cool to 980-1050℃ and hold for 30-90 minutes to promote the precipitation of zirconium-titanium microcrystals on the surface of the transition glaze layer; The temperature is then lowered to 720-820℃ and held for 20-60 minutes to promote the formation of micro-phases of borosilicate and aluminosilicate phases on the surface of the transition glaze layer.

6. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The weak acid activation treatment uses a 0.05-0.30 mol / L aqueous solution of citric acid, acetic acid, or oxalic acid, and is treated at 40-70℃ for 5-25 min. After activation treatment with weak acid, wash with deionized water until the pH of the washing solution is 6.0-7.5, and then dry at 80-120℃ for 20-60 minutes. The activated glaze, after being treated with weak acid, has nano-anchoring pits with a depth of 30-120nm.

7. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The inorganic anchoring solution is composed of zirconium phosphate sol, aluminum sol, and silica sol modified with silane coupling agent; The molar ratio of zirconium phosphate sol (calculated as ZrO2), aluminum sol (calculated as Al2O3), and silica sol (calculated as SiO2) is 1:0.3-1.2:1.5-4.

0. The inorganic anchoring solution has a pH of 2.5-4.5 and a solid content of 1.0-5.0 wt%. After coating, it is pre-cured at 120-180℃ for 10-40 min to form a phosphorus-zirconium-aluminum inorganic anchoring layer with a thickness of 10-50 nm.

8. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The cerium-modified anatase titanium dioxide sol is prepared by hydrolyzing tetrabutyl titanate or isopropyl titanate in an acidic alcohol-water system and adding cerium nitrate or cerium acetate. Based on TiO2 and CeO2, CeO2 accounts for 0.3-2.0% of the mass of TiO2; In the titanium dioxide-silica-zirconia composite self-cleaning sol, the molar ratio of TiO2, SiO2 and ZrO2 is 1:1.8-4.5:0.08-0.35; The composite self-cleaning sol is used after aging for 6-24 hours, and its solid content is 1.5-6.0 wt%.

9. The preparation process of a self-cleaning high-strength ceramic insulator according to claim 1, characterized in that, The composite self-cleaning sol is applied to the surface of ceramic insulators by rotary spraying. The rotation speed of the ceramic insulators during spraying is 30-120 r / min, and the surface temperature of the substrate is 60-95℃. The composite self-cleaning sol is sprayed in at least three coats. In the first coat, the total molar amount of SiO2 and ZrO2 in the sol is higher than that of TiO2, forming a densely bonded sublayer. In the last coat, the molar amount of TiO2 in the sol is higher than that of SiO2 and ZrO2, forming a photocatalytic self-cleaning surface layer. After spraying, heat treat at 420-500℃ for 30-90 minutes to make the total thickness of the gradient self-cleaning layer 80-220nm.

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