A surface defect-free forming process for ceramic insulators

Abstract

This invention discloses a defect-free surface forming process for ceramic insulators, relating to the field of ceramic insulator production technology. The process includes the following steps: Preparation stage: preparing ceramic blanks; preparing gradient functional microcapsules. Forming and drying stage: mixing each microcapsule with water, binder, and dispersant to prepare various coating liquids; sequentially covering the inner wall of a mold used for making ceramic insulators with each coating liquid; placing the ceramic blank into the coated mold, sealing the mold, and applying pressure to form the ceramic blank; sending the ceramic green blank with multiple solid film layers on its surface into a microwave drying kiln for drying to obtain a dried ceramic blank. Firing stage: glazing the dried ceramic blank; sending the glazed dried blank into a kiln for firing. This defect-free surface forming process for ceramic insulators effectively combines the advantages of low scrap rate, short production cycle, and low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of ceramic insulator manufacturing technology, specifically to a defect-free forming process for ceramic insulator surfaces. Background Technology

[0002] Porcelain insulators are insulating components for electrical equipment made of electrical ceramics, primarily composed of high-purity alumina and zirconium oxide. Their structure includes an iron cap, porcelain body, and steel feet, assembled using cement bonding. They possess high-temperature resistance, pressure resistance, and corrosion resistance, and are used for external insulation of high-voltage transmission lines and power station equipment. Based on their application, they are classified into three categories: those for transmission lines, those for power station equipment, and those for other live conductors.

[0003] In existing ceramic insulator manufacturing processes, isostatic pressing or slip casting is commonly used to form ceramic blanks into wet blanks. These wet blanks contain a large amount of moisture and must be dried before subsequent glazing and firing; otherwise, they are prone to cracking during the firing process.

[0004] Traditional drying methods typically use hot air, but this outside-to-inside heating causes the surface moisture of the wet billet to evaporate much faster than the interior, easily forming a dense, hard shell. This shell blocks the release of moisture from the billet's interior. Over time, the internal moisture continues to vaporize due to heat but cannot escape properly, leading to significant steam pressure inside the billet. When this pressure exceeds the billet's tolerance limit, cracks and bubbles form, resulting in product failure. To address this problem and prevent the formation of this hard shell, most factories employ a very slow, low-temperature, high-humidity drying process lasting 24 to 72 hours. While this method reduces the scrap rate to some extent, it results in a long production cycle and high energy consumption.

[0005] Therefore, there is a need for a new ceramic insulator molding process that can take into account the advantages of low scrap rate, short production cycle and low energy consumption. Summary of the Invention

[0006] The main objective of this invention is to provide a defect-free forming process for ceramic insulator surfaces, which can effectively combine the advantages of low scrap rate, short production cycle and low energy consumption.

[0007] The above-mentioned technical objective of this invention is achieved through the following technical solution: a defect-free forming process for ceramic insulator surfaces, comprising:

[0008] A. Preparation stage:

[0009] a) Prepare ceramic blanks;

[0010] b) Prepare gradient functional microcapsules, specifically: prepare at least two types of microcapsules, wherein the rupture temperature of each microcapsule after heating varies in a gradient.

[0011] B. Molding and Drying Stage:

[0012] a) Each microcapsule was mixed with water, binder and dispersant to prepare various coating liquids;

[0013] b) Each coating liquid is sequentially applied to the inner wall of the mold used to make ceramic insulators. Each layer is dried after application to evaporate the moisture and form a solid film. In the end, the inner wall of the mold is uniformly covered with a multi-layer structure. The heat-induced rupture temperature of the microcapsules in the multi-layer structure gradually decreases from the layer that is attached to the inner wall of the mold to the layer that is away from the inner wall of the mold.

[0014] c) Place the ceramic blank into a mold that has been coated, close the mold, apply pressure to form the ceramic blank, release the forming pressure, open the mold, and obtain the formed ceramic green blank. During this process, the solid film layers on the inner wall of the mold are transferred and attached to the outer surface of the ceramic green blank.

[0015] d) The ceramic green body with multiple solid film layers on its surface is fed into a microwave drying kiln for drying treatment to obtain a dried ceramic green body;

[0016] C. Firing stage:

[0017] a) Glazing the dry ceramic blank;

[0018] b) The glazed dry blanks are sent into the kiln for firing. After firing is completed and the kiln is completely cooled, the final ceramic insulator is obtained.

[0019] In some embodiments, a single microcapsule consists of a core and a capsule wall surrounding the core.

[0020] In some embodiments, the core is made of polyethylene glycol and / or paraffin.

[0021] In some embodiments, the capsule wall is made of gelatin and / or polyvinyl alcohol.

[0022] In some embodiments, microcapsules achieve different thermal rupture temperatures by adjusting the cross-linking density of their capsule walls.

[0023] In some embodiments, sodium carboxymethyl cellulose is selected as the binder.

[0024] In some embodiments, in step c) of the forming and drying stage, the ceramic blank is formed by applying pressure in the manner of isostatic pressing.

[0025] In some embodiments, in step b) of the firing stage, the firing process includes:

[0026] Stage 1 for completely decomposing the multilayer solid film on the surface of ceramic green bodies: low-temperature preheating stage from 300°C to 500°C;

[0027] Stage Two for Fully Melted Glaze: High Temperature Stage Above 800°C.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention uses microwaves to heat the formed billet. During heating, microwave energy can penetrate the billet, allowing the inside and outside of the billet to be heated simultaneously. Compared with traditional hot air drying, this simultaneous heating method can greatly delay the formation of a hard shell on the surface of the billet. However, although microwave heating is simultaneous heating, the outer layer of the billet is directly exposed to the external environment, while the inner layer is wrapped inside. This results in the outermost layer of the billet exchanging heat and moisture with the relatively cold and dry air in the drying kiln, leading to a relatively fast rate of water loss. Meanwhile, the internal moisture needs to migrate to the surface before evaporating, and the migration rate is much slower than the surface evaporation rate. As a result, a hard shell will still form on the surface of the billet, and the billet is still easily broken by the continuously rising internal steam pressure, thus forming destructive defects such as microcracks, bubbles, or even surface bursting. To address this, the present invention covers the outer surface of the billet with multiple layers of solid film during the billet forming stage. These layers contain numerous microcapsules. During the heating stage, these microcapsules rupture early, forming a porous coating layer on the outer surface of the billet. Within this porous coating layer, a thin layer of almost stagnant air is retained in the numerous tiny pores near the surface of the billet. When the moisture on the surface of the billet begins to evaporate, this stagnant air layer quickly reaches saturation or near-saturation humidity. This effectively isolates the wet surface of the billet from direct and intense contact with the dry, flowing air outside, greatly slowing down the natural water loss rate of the outermost layer of the billet. This prevents the formation of a hard shell on the outer surface of the billet during microwave heating, thus avoiding product damage and scrap due to the inability to release internal pressure.

[0030] The multi-layered solid film covering the outer surface of the billet is composed of countless microcapsules. The rupture temperature of these microcapsules after heating exhibits a gradient: specifically, the rupture temperature of the microcapsules from the outermost to the innermost layer of the billet surface gradually decreases. In other words, during microwave heating, as the temperature rises, microcapsules closer to the billet surface rupture first, while those farther away rupture later. This results in the initial steam pressure generated inside the billet being released gradually through the innermost coating layer, preventing instantaneous pressure buildup. As the internal temperature continues to rise and steam generation increases, the outer coating layer eventually ruptures. This provides a larger exhaust channel to accommodate greater exhaust demand, thus breaking down a potentially damaging instantaneous release into several gradual releases. Furthermore, because the cracking process occurs from the inside out and on demand, it effectively creates a smooth, continuously widening pathway for the water vapor surging outwards in real time and synchronously, achieving orderly guidance of the water vapor. Throughout the process, because the internal steam pressure is consistently controlled at a low, safe level and can be uniformly guided out, it prevents stress concentration at any weak point in the billet that could lead to cracking. The stress state of the entire billet during the drying process is very uniform and gentle. In addition, during microwave heating, the rate of water vapor generation inside the billet is synchronized with the rate of generation through the external release channel, achieving a dynamic balance between the two.

[0031] Therefore, the process of this invention avoids the formation of a hard shell on the billet and allows for a more gradual release of internal steam pressure, significantly reducing the formation of cracks and bubbles in the billet, thereby effectively reducing the scrap rate. Furthermore, because this invention does not employ hot air drying from the outside in, but rather uses simultaneous microwave heating from the inside and outside, the entire process eliminates the need for a very slow, long-lasting 24 to 72-hour low-temperature, high-humidity drying process, significantly shortening the production cycle. A shorter production cycle results in lower energy consumption. Therefore, the process of this invention effectively balances the advantages of low scrap rate, short production cycle, and low energy consumption. Attached Figure Description

[0032] Figure 1 This is a flowchart of the process of the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, a preferred embodiment will be described in detail below. It should be noted that this embodiment is merely illustrative and should not be construed as limiting the scope of protection of the present invention in any way.

[0034] This embodiment aims to produce a defect-free surface forming process for ceramic insulators, with the goal of solving the technical problems caused by traditional long-cycle hot air drying processes, such as surface cracking, low yield, long production cycle, and high energy consumption.

[0035] like Figure 1 As shown in the figure, this embodiment discloses a defect-free forming process for ceramic insulator surfaces, which includes the following steps:

[0036] A. Preparation stage:

[0037] a) Prepare ceramic blanks;

[0038] The main components of ceramic blanks include: high-purity kaolin, quartz powder (or alumina powder used for higher strength), and feldspar powder. High-purity kaolin acts as a plastic skeleton, ensuring the plasticity of the blank during molding and its strength after molding. Quartz powder (or alumina powder used for higher strength) acts as a non-plastic skeleton, forming a stable structure during firing and giving the ceramic body rigidity. Feldspar powder acts as a flux, melting at high temperatures to form a glassy phase, binding, filling, and vitrifying all loose particles into a dense whole.

[0039] The weighed raw materials are fed into a large ball mill, and a measured amount of water is added for prolonged wet ball milling and mixing. The ball mill is equipped with hard grinding balls (such as alumina balls). Through the rotation of the drum, the grinding balls continuously impact and grind the raw materials. This process grinds all the raw materials to the micron-level fineness required to ensure the full progress of the subsequent calcination reaction. It also allows the tiny particles of different components to be uniformly mixed in the water, forming a stable and fine suspension, i.e., a slurry state.

[0040] The raw material in mud form needs to be sieved through a screen to remove any large particles that may not have been sufficiently ground. After sieving, the mud also needs to undergo iron removal treatment. This step is to adsorb and remove trace amounts of iron impurities that may inevitably be introduced into the raw material to ensure the electrical insulation performance of the insulator.

[0041] Afterwards, the slurry undergoes pressure filtration and dehydration, followed by vacuum kneading to obtain high-quality ceramic blanks. Pressure filtration reduces the water content of the slurry, while the organic matter in the raw materials undergoes slow hydrolysis and fermentation, further improving the plasticity and bonding properties of the blanks. Vacuum kneading, on the other hand, subjectes the clay to strong shearing, compression, and kneading, maximizing its uniformity and forming a uniform, high-density clay section that is completely free of air bubbles—that is, the ceramic blank.

[0042] b) Prepare gradient functional microcapsules, specifically: prepare at least two types of microcapsules, the rupture temperature of each microcapsule after heating varies in a gradient; further, each individual microcapsule consists of a core and a capsule wall surrounding the core.

[0043] Preferably, the core is made of polyethylene glycol and / or paraffin.

[0044] Preferably, the capsule wall is made of gelatin and / or polyvinyl alcohol.

[0045] Preferably, the microcapsules achieve different thermal rupture temperatures by adjusting the cross-linking density of their capsule walls.

[0046] For example, the following is a specific process for preparing two microcapsules with different rupture temperatures (e.g., microcapsule A ruptures at 110°C and microcapsule B ruptures at 140°C), preferably using a double emulsion method and a complex coagulation method. The principle is to achieve different mechanical strengths and thermal stability by controlling the crosslinking density of the capsule wall, thereby setting their respective rupture temperatures:

[0047] S1. Preparation of primary oil-in-water emulsion: The purpose is to transform the water-soluble core into an oil droplet state. The specific operation is as follows: under high-speed shearing, polyethylene glycol (PEG-200) is dispersed into an oil phase that is insoluble in water (e.g., cyclohexane containing emulsifier Span 80) to form an emulsion in which PEG-200 microdroplets are uniformly suspended in cyclohexane.

[0048] S2. Preparation of a double water-in-oil-in-water emulsion: Gelatin and gum arabic, which serve as the capsule wall materials, are dissolved in deionized water to form an outer aqueous phase. Then, under gentle stirring, the emulsion prepared in step S1 is dispersed as a whole into this outer aqueous phase. At this time, the microdroplet structure formed in the system is as follows: the innermost layer is a PEG-200 capsule core, the middle layer is a temporary cyclohexane oil layer, and the outermost layer is suspended in an aqueous solution containing the capsule wall materials.

[0049] S3. Coagulation and Wall Formation: The pH value of the external aqueous phase in step S2 is adjusted by adding an acidic solution, causing the dissolved gelatin and gum arabic to coagulate and automatically deposit and coat the outer surface of the oil droplets in the emulsion, thereby forming a preliminary capsule wall. Then, a curing agent (e.g., 0.5% glutaraldehyde solution) is added to the system. After the reaction is complete, the capsule wall will be cured. The concentration of the curing agent determines the crosslinking density of the capsule wall. Therefore, for microcapsules A that rupture at 110°C, a lower concentration of curing agent (e.g., 0.5% glutaraldehyde solution) is sufficient.

[0050] S4. Post-processing: After filtering, washing and drying the microcapsule suspension obtained in the above steps, the cyclohexane oil phase, which serves as a temporary carrier, will be completely removed, thereby obtaining the final powdered microcapsule A.

[0051] Microcapsules B, which rupture at 140°C, can also be produced using the same steps as described above, with different concentrations of curing agent used; these details will not be elaborated upon here.

[0052] When heated, the core of a microcapsule changes from a liquid or solid state to a gaseous state, causing it to expand rapidly and generate enormous internal pressure. Meanwhile, the capsule wall softens when heated, significantly reducing its mechanical strength. This combination of expansion and softening causes the microcapsule to rupture when heated to a specific temperature.

[0053] B. Molding and Drying Stage:

[0054] a) Mix each microcapsule with water, binder and dispersant to prepare a variety of coating liquids. The purpose of this step is to uniformly disperse these different types of microcapsules in the liquid medium to form an easy-to-spray state. For each type of microcapsule with a different rupture temperature, the coating liquid is prepared separately. Preferably, sodium carboxymethyl cellulose can be used as the binder.

[0055] The specific process is as follows:

[0056] S1. Add deionized water to a container and, under slow stirring, add sodium carboxymethyl cellulose (CMC), preferably as a binder. CMC can significantly increase the viscosity of water, forming a transparent solution similar to diluted glue. By increasing the viscosity of the system, it can provide sufficient buoyancy for the microcapsules added later, preventing them from settling rapidly due to gravity. Moreover, after the coating dries, CMC will form a continuous network skeleton, bonding all the individual microcapsules into a solid film with overall strength.

[0057] S2. Add a small amount of dispersant to the system treated in step S1. The dispersant is a surfactant that adsorbs onto the surface of each microcapsule. Through electrostatic repulsion or steric hindrance, it effectively overcomes the tendency of microparticles to attract each other and agglomerate in the liquid due to van der Waals forces, thereby achieving uniform distribution of microcapsules and avoiding clumping.

[0058] S3. Add microcapsule powder to the system treated in step S2, and stir continuously during the addition process. The final product is a suspension with uniform appearance and suitable viscosity and flowability, namely the coating liquid.

[0059] b) Each coating liquid is sequentially applied to the inner wall of the mold used to make ceramic insulators. Each layer is dried after application to evaporate the moisture and form a solid film. In the end, the inner wall of the mold is uniformly covered with a multi-layer structure. The heat-induced rupture temperature of the microcapsules in the multi-layer structure gradually decreases from the layer that is attached to the inner wall of the mold to the layer that is away from the inner wall of the mold.

[0060] This step involves a programmed, layered process to create a gradient functional coating structure on the inner wall of the mold. This step can be achieved using commercially available spraying systems, as long as the uniformity of each coating layer, controllable thickness, and clear distinction between layers are ensured. The specific steps are as follows (taking two-layer spraying as an example):

[0061] S1. Spray the first layer: Use a spray gun to evenly spray the prepared coating liquid B containing microcapsules B (rupture temperature about 140°C) onto the preheated and cleaned inner wall of the mold.

[0062] S2. After the first layer of coating liquid B is sprayed, a drying process is performed immediately. Clean hot air (e.g., 60-80°C) generated by existing equipment can be used to briefly blow on the inner wall of the mold until a solid, dry solid film is formed on the inner wall of the mold.

[0063] S3. Repeat the above steps to uniformly spray the coating liquid A containing microcapsules A (rupture temperature of about 110°C) onto the surface of the first layer of coating B that has been dried and cured, and then perform a drying process again.

[0064] c) Place the ceramic blank into a mold that has been coated, close the mold, apply pressure to form the ceramic blank, release the forming pressure, open the mold, and obtain the formed ceramic green blank. During this process, the solid film layers on the inner wall of the mold are transferred and attached to the outer surface of the ceramic green blank. Preferably, the method of applying pressure to form the ceramic blank can be isostatic pressing.

[0065] The purpose of this step is to transfer the pre-prepared gradient functional coating from the inner wall of the mold to the surface of the ceramic blank while shaping the ceramic raw material into the predetermined insulator shape. The specific steps are as follows:

[0066] S1. Fill the irregularly shaped ceramic blank into the molding mold with a dry solid coating on the inner wall. After filling, seal the mold completely.

[0067] S2. The sealed mold is placed in the working chamber of the isostatic press. Under the huge pressure of the isostatic press, the loose ceramic powder particles are forcibly rearranged and squeezed, the gaps between the particles are eliminated, and the powder is compacted into a solid with considerable density and strength that is completely consistent with the shape of the inner cavity of the mold, i.e., the formed ceramic green body. During the above pressing process, the moisture carried by the ceramic powder particles will be partially squeezed out under high pressure and will come into contact with the innermost layer of the dry gradient coating in close contact. The hydrophilic binder (CMC) contained in the coating will be activated after contact with this moisture, thereby forming a strong adhesion interface between the coating and the surface of the ceramic green body. This ensures that after subsequent demolding, the multi-layer solid film sprayed on the inner wall of the mold can firmly adhere to the outer surface of the ceramic green body. This process is the automatic transfer of the coating.

[0068] S3. When the molding pressure is released after a preset time, the working chamber of the isostatic press is emptied, and the mold is removed and opened to obtain the molded ceramic green body.

[0069] d) The ceramic green body with multiple solid film layers on its surface is fed into a microwave drying kiln for drying treatment to obtain a dried ceramic green body;

[0070] This step aims to quickly, safely, and without defects dry the ceramic blank obtained in the previous process, which contains a large amount of moisture inside:

[0071] This step uses microwaves to heat the formed billet. During heating, microwave energy can penetrate the billet, allowing the inside and outside of the billet to be heated simultaneously. Compared to traditional hot air drying, this simultaneous heating method can greatly delay the formation of a hard shell on the surface of the billet. However, although microwave heating is simultaneous, the outer layer of the billet is directly exposed to the external environment, while the inner layer is wrapped inside. This results in the outermost layer of the billet exchanging heat and moisture with the relatively cold and dry air inside the drying kiln, leading to a relatively fast rate of water loss. Meanwhile, the internal moisture needs to migrate to the surface before evaporating, and the migration rate is much slower than the surface evaporation rate. As a result, a hard shell will still form on the surface of the billet, and the billet is still easily broken by the continuously rising internal steam pressure, thus forming destructive defects such as microcracks, bubbles, or even surface bursts. To address this, the present invention covers the outer surface of the billet with multiple layers of solid film during the billet forming stage. These layers contain numerous microcapsules. During the heating stage, these microcapsules rupture early, forming a porous coating layer on the outer surface of the billet. Within this porous coating layer, a thin layer of almost stagnant air is retained in the numerous tiny pores near the surface of the billet. When the moisture on the surface of the billet begins to evaporate, this stagnant air layer quickly reaches saturation or near-saturation humidity. This effectively isolates the wet surface of the billet from direct and intense contact with the dry, flowing air outside, greatly slowing down the natural water loss rate of the outermost layer of the billet. This prevents the formation of a hard shell on the outer surface of the billet during microwave heating, thus avoiding product damage and scrap due to the inability to release internal pressure.

[0072] The multi-layered solid film covering the outer surface of the billet is composed of countless microcapsules. The rupture temperature of these microcapsules after heating exhibits a gradient: specifically, the rupture temperature of the microcapsules from the outermost to the innermost layer of the billet surface gradually decreases. In other words, during microwave heating, as the temperature rises, microcapsules closer to the billet surface rupture first, while those farther away rupture later. This results in the initial steam pressure generated inside the billet being released gradually through the innermost coating layer, preventing instantaneous pressure buildup. As the internal temperature continues to rise and steam generation increases, the outer coating layer eventually ruptures. This provides a larger exhaust channel to accommodate greater exhaust demand, thus breaking down a potentially damaging instantaneous release into several gradual releases. Furthermore, because the cracking process occurs from the inside out and on demand, it effectively creates a smooth, continuously widening pathway for the water vapor surging outwards in real time and synchronously, achieving orderly guidance of the water vapor. Throughout the process, because the internal steam pressure is consistently controlled at a low, safe level and can be uniformly guided out, it prevents stress concentration at any weak point in the billet that could lead to cracking. The stress state of the entire billet during the drying process is very uniform and gentle. In addition, during microwave heating, the rate of water vapor generation inside the billet is synchronized with the rate of generation through the external release channel, achieving a dynamic balance between the two.

[0073] This step transforms an uncontrollable physical process that could lead to stress concentration into a smooth, orderly engineering process in which the pressure is always kept below a safe threshold. The entire process is much shorter than traditional methods (only 1-2 hours).

[0074] C. Firing stage:

[0075] a) Glazing the dry ceramic blank;

[0076] The purpose of this step is to coat the final insulator with a dense vitreous glaze. This glaze not only greatly improves the mechanical strength and electrical insulation performance of the product, but also provides a smooth, water-repellent, and easy-to-clean surface to resist dirt and moisture erosion in the outdoor environment and ensure long-term stable operation. For glazing the ceramic blank, the preferred method is the efficient and uniform glazing or dipping method used in industrial production. All glazing methods are existing technologies and will not be described in detail in this embodiment.

[0077] During glazing, the surface of the ceramic blank is still covered with a porous coating skeleton formed by ruptured microcapsules left after the drying steps. Therefore, when the liquid glaze slurry is applied to it, the glaze slurry will partially penetrate into the open pores of the porous skeleton. This glaze slurry that penetrates into the pores can directly contact the surface of the ceramic blank, forming a riveting effect, which makes the glaze slurry and the blank more mechanically interlocked, laying the foundation for the final firm bonding between the glaze and the porcelain body.

[0078] After glazing, the glaze slurry on the surface of the body will be naturally dried or briefly dried at low temperature, and the moisture in it will be completely evaporated. At this time, the glaze adhering to the surface of the body is a loose and completely breathable solid powder layer. It is this loose and breathable characteristic that provides an escape channel for the decomposition and gasification of the coating skeleton in the low temperature stage of the subsequent firing process.

[0079] b) The glazed dry blank is sent into the kiln for firing. After firing is completed and the kiln has completely cooled, the final ceramic insulator is obtained. Preferably, this stage of the firing process includes:

[0080] 1. Stage 1 for completely decomposing the multi-layered solid film on the surface of ceramic green bodies: low-temperature preheating stage from 300°C to 500°C;

[0081] 2. Stage Two for Completely Melted Glaze: High Temperature Stage Above 800°C.

[0082] The purpose of this step is to eliminate the multiple solid film layers and molten glaze on the surface of the ceramic green body. In stage one, the stability of the core, wall and binder chemical bonds of the microcapsules in the solid film layer on the surface of the ceramic green body cannot withstand a temperature exceeding 300°C. When the firing temperature is higher than 300°C, the long molecular chains in the solid film layer on the surface of the ceramic green body will break and eventually be transformed into small molecule gases such as carbon dioxide and water vapor. These small molecule gases will escape through the powdered glaze that has not yet reached the glassy state, thus leaving a pure ceramic body surface under the glaze powder layer, which is ready to be combined with the glaze.

[0083] In stage two, after all organic matter has been completely eliminated, the kiln temperature continues to rise, entering the high-temperature firing stage. When the temperature reaches above 800°C, the glaze begins to melt. The originally loose mineral powder particles begin to soften, shrink, and eventually melt into a layer of liquid glass with good fluidity. This liquid glass layer automatically levels itself due to surface tension, filling all the gaps between the particles to form a continuous, smooth liquid surface. At the same time, it wets and partially penetrates into the surface of the underlying ceramic body, forming a strong, interlocking intermediate transition layer, demonstrating high bonding strength. When the entire firing process is completed, and the kiln cools slowly according to a strict cooling curve, the molten glaze solidifies into a hard, smooth, and dense glassy layer, while the body has transformed into a porcelain body with extremely high mechanical strength and excellent electrical insulation properties, which is the finished product of this invention.

[0084] In summary, the process of this invention involves pre-preparing a multi-layered solid coating composed of microcapsules with different thermal response temperatures on the inner wall of the molding mold. During the green body forming process, this coating is completely transferred to the surface of the ceramic green body, and subsequent drying is performed using microwaves. During the drying process, the coating can respond to temperature changes and form a porous structure from the inside out in stages, allowing internal moisture to escape. This avoids stress concentration caused by uneven drying rates inside and outside the green body, preventing the formation of surface defects. The subsequent glazing and high-temperature firing steps ensure the complete decomposition and removal of all temporary organic matter, including the functional coating, as well as the dense bonding between the glaze and the ceramic green body. This process produces a ceramic insulator with a defect-free surface with low scrap rate, short production cycle, and low energy consumption.

[0085] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A defect-free forming process for ceramic insulator surfaces, characterized in that, include: A. Preparation stage: a) Prepare ceramic blanks; b) Prepare gradient functional microcapsules, specifically: prepare at least two types of microcapsules, wherein the rupture temperature of each microcapsule after heating varies in a gradient. B. Molding and Drying Stage: a) Each microcapsule was mixed with water, binder and dispersant to prepare various coating liquids; b) Each coating liquid is sequentially applied to the inner wall of the mold used to make ceramic insulators. Each layer is dried after application to evaporate the moisture and form a solid film. In the end, the inner wall of the mold is uniformly covered with a multi-layer structure. The heat-induced rupture temperature of the microcapsules in the multi-layer structure gradually decreases from the layer that is attached to the inner wall of the mold to the layer that is away from the inner wall of the mold. c) Place the ceramic blank into a mold that has been coated, close the mold, apply pressure to form the ceramic blank, release the forming pressure, open the mold, and obtain the formed ceramic blank. During this process, the solid film layers on the inner wall of the mold are transferred and attached to the outer surface of the ceramic blank. d) The ceramic green body with multiple solid film layers on its surface is fed into a microwave drying kiln for drying treatment to obtain a dried ceramic green body; C. Firing stage: a) Glazing the dry ceramic blank; b) The glazed dry blanks are sent into the kiln for firing. After firing is completed and the kiln is completely cooled, the final ceramic insulator is obtained.

2. The defect-free forming process for ceramic insulator surfaces according to claim 1, characterized in that: A single microcapsule consists of a core and a capsule wall that surrounds the core.

3. The defect-free forming process for ceramic insulator surfaces according to claim 2, characterized in that: The core is made of polyethylene glycol and / or paraffin.

4. The defect-free forming process for ceramic insulator surfaces according to claim 2, characterized in that: The capsule wall is made of gelatin and / or polyvinyl alcohol.

5. The defect-free forming process for ceramic insulator surfaces according to claim 2, characterized in that: Microcapsules achieve different thermal rupture temperatures by adjusting the cross-linking density of their capsule walls.

6. The defect-free forming process for ceramic insulator surfaces according to claim 1, characterized in that: Sodium carboxymethyl cellulose was selected as the binder.

7. The defect-free forming process for ceramic insulator surfaces according to claim 1, characterized in that: In step c) of the forming and drying stage, the ceramic blank is formed by applying pressure using isostatic pressing.

8. The defect-free forming process for ceramic insulator surfaces according to claim 1, characterized in that: In step b) of the firing stage, the firing process includes: Stage 1 for completely decomposing the multilayer solid film on the surface of ceramic green bodies: low-temperature preheating stage from 300°C to 500°C; Stage Two for Fully Melted Glaze: High Temperature Stage Above 800°C.

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