High-whiteness high-voltage-resistant insulator ceramic material and preparation process thereof

Abstract

This invention belongs to the technical field of electrical inorganic materials, specifically relating to a high-whiteness, high-voltage resistant insulator ceramic material and its preparation process. The ceramic material, by mass, consists of a basic component, a structure-regulating component, and an auxiliary phase component. Zirconia and niobium pentoxide are introduced to construct a composite regulation system, and various components such as talc, barium oxide, and magnesium oxide are combined to form a multiphase compatibility structure. The auxiliary phase uses rare earth oxides and borate fluxes to adjust the phase composition and stability. The preparation method includes steps such as raw material mixing, pressure filtration and mud refining, molding, drying and bisque firing, glazing, and high-temperature firing. A composite oxide glaze system is used for glaze construction. This invention features strong formulation synergy and precise structure regulation in its material composition and sintering process, making it suitable for the preparation of high-performance insulator ceramic products.

Description

Technical Field

[0001] This invention belongs to the technical field of electrical inorganic materials, specifically relating to a high-whiteness, high-voltage resistant ceramic insulator and its preparation process. Background Technology

[0002] Ceramic insulators, as key components in high-voltage power transmission and transformation systems, are widely used in transmission lines, substations, and power distribution equipment. Their basic function is to isolate conductors under high voltage conditions, prevent current leakage, and ensure the safety of equipment and personnel. Among various insulating materials, ceramics are widely used due to their excellent insulation properties, good thermal stability, and mechanical strength. With the increasing voltage levels of power grids and the growing demands for equipment appearance quality, ceramic insulating materials with high whiteness, high voltage resistance, low water absorption, and good anti-pollution capabilities have become a key focus of research and industrialization.

[0003] Currently, common ceramic insulator materials mainly use porcelain clay, quartz, and feldspar as basic raw materials, forming a dense multiphase structure system through high-temperature sintering. To improve product performance, different technical routes employ various optimization methods, such as adding alumina to improve mechanical strength and insulation performance, introducing kaolin or low-iron content raw materials to enhance whiteness, or controlling sintering temperature and atmosphere to improve microstructure uniformity. However, these process routes generally have the following problems: On the one hand, some raw materials in traditional formulas have a high iron content, which easily leads to a dull color and insufficient whiteness in ceramic products, making it difficult to meet the aesthetic and identifiable requirements of modern power transmission equipment; on the other hand, the process window for ensuring high whiteness while simultaneously achieving high density, high breakdown voltage, and long-term weather resistance is narrow, and improper sintering control can easily lead to a decrease in insulation strength or an increase in product cracking rate. In addition, some whiteness modification methods rely on expensive raw materials or complex processes, resulting in increased costs and greater difficulty in promotion.

[0004] Therefore, developing a ceramic insulator material with a reasonable formula and controllable process that possesses both high whiteness and the ability to withstand high-voltage environments is of significant engineering value and practical necessity for improving insulator performance and optimizing the appearance and reliability of power transmission systems. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide: 1. A high-whiteness, high-voltage resistant ceramic insulator material, which, by weight of total raw materials, is composed of the following three types of components: Basic components: 55-65 parts kaolin, 10-20 parts feldspar, 5-12 parts quartz; Structure-regulating components: 1-6 parts zirconium oxide, 1-6 parts aluminum oxide, 0.2-1.0 parts magnesium oxide, 0.1-0.8 parts calcium oxide, 0.1-0.6 parts barium oxide, 0.2-1.0 parts talc, and 0.1-1.0 parts niobium pentoxide; Auxiliary coordinating phase components: 0.3-1.5 parts of titanium oxide, 0.2-1.2 parts of zinc oxide, 0.1-0.8 parts of borate flux, and 0.05-0.5 parts of rare earth oxides, wherein the rare earth oxides include cerium oxide, lanthanum oxide, neodymium oxide, or mixtures thereof.

[0006] As a preferred technical solution, the mass ratio of zirconium oxide to niobium pentoxide in the structure regulating component is 5:1 to 10:1; the zirconium oxide is nano-zirconia powder with an average particle size of 30 to 80 nm, which is pre-dispersed with sodium polyacrylate dispersant after being coated with silane coupling agent before use. The coating is made of γ-aminopropyltriethoxysilane (added at 0.2-1.0 wt% of the zirconium oxide mass), which forms a coating layer after constant temperature stirring and drying reaction. The pre-dispersion process is carried out by high shear stirring for 20-30 minutes, and the pH of the slurry is controlled between 9.5 and 10.5.

[0007] As a preferred technical solution, the basic components include: Kaolin is a low-iron kaolin with an Fe2O3 mass fraction not exceeding 0.5%. The feldspar is a mixture of potassium feldspar and sodium feldspar, with the potassium-sodium molar ratio controlled between 0.8 and 1.2. The quartz is high-purity quartz powder, with a SiO2 mass fraction of not less than 98%; Each component was pretreated by 200-mesh sieving and drying before mixing.

[0008] As a preferred technical solution, the structure-regulating component comprises: Talc powder is water-washed refined talc, containing Mg3Si4O 10 The (OH)2 content is not less than 90%, and the particle size D50 is controlled between 1 and 4 μm; Magnesium oxide is lightly calcined magnesium oxide powder with a particle size of 2–5 μm; The calcium oxide is high-purity calcium oxide obtained by calcining pure limestone; Barium oxide is obtained by calcining barium carbonate and has a purity of over 98%.

[0009] As a preferred technical solution, the auxiliary coordination phase component comprises: Titanium oxide is an anatase crystalline phase, while zinc oxide is an amorphous phase; The mass ratio of cerium oxide to lanthanum oxide in the rare earth oxide is 1.5:1 to 2.5:1, and the total doping amount is 0.1 to 0.3 parts. The borate flux is a compound system of anhydrous borax and boric acid with a compounding ratio of 3:1 and a particle size of less than 75 μm.

[0010] The present invention also provides a method for preparing the high-whiteness, high-voltage resistant ceramic insulator, comprising the following steps: S1. Raw material mixing: Weigh the basic components, structure regulating components and auxiliary phase components according to the proportion, place all powders in a ball mill jar, add sodium polyacrylate dispersant at a mass of 0.3-0.5% of the total raw material mass, add deionized water at a solid-liquid ratio of 1:1.2-1:1.4, wet ball mill for 12-16 hours, the ball milling media is zirconia balls, the ball-to-material ratio is controlled at 3:1, and the slurry particle size D50 is controlled at 0.5-1.5 μm; S2. Filtration and mud refining: The slurry is pressed into mud cakes with a moisture content of 20±2%. The mud is then continuously refined using a vacuum mud cylinder with the rotation speed controlled at 25-30 rpm and the refining time not less than 40 minutes. S3. Molding: The refined mud is extruded into billets using a vacuum screw extruder, or isostatic pressing is used for molding. The isostatic pressing pressure is controlled at 80-120 MPa, and the holding time is 3-5 minutes. The size fluctuation of the resulting billet does not exceed ±1%. S4. Drying and Firing: The formed blank is placed in an environment of 35-45℃ and 45-55% relative humidity for 24-48 hours to dry. After drying, it is placed in an electric furnace and heated to 850-950℃ at a heating rate of 1-3℃ / min for bisque firing. The temperature is held for 1.5-2 hours. After cooling, the bisque blank is obtained. S5. Glazing and High-Temperature Firing: Apply glaze to the surface of the bisque-fired body by spraying or dipping. The spraying pressure is 0.15–0.25 MPa, and the nozzle orifice diameter is 0.6–1.0 mm. After glazing, dry at 80°C for 6 hours, and then place it in a high-temperature electric furnace for firing. The firing temperature is 1280–1320°C, the heating rate is 2–4°C / min, the holding time is 4–6 hours, the firing atmosphere is an oxidizing atmosphere, and the cooling rate is controlled at 1–2°C / min.

[0011] As a preferred technical solution, in step S1, the ball milling media are zirconia balls with a diameter of 3 to 5 mm. The slurry is continuously circulated and filtered, and the pH value of the slurry is controlled between 9.5 and 10.5. After ball milling, the slurry is allowed to settle for no less than 2 hours to remove large air bubbles.

[0012] As a preferred technical solution, the mold used for equistatic pressing in step S3 is a polyurethane-stainless steel composite mold with a pre-set exhaust channel in the mold cavity. The formed blank is placed in a humidity control chamber for slow drying for no less than 12 hours, and the relative humidity change rate of the drying chamber is controlled to be no more than 5% / h.

[0013] As a preferred technical solution, the glaze used in step S5 adopts a composite oxide glaze system, which includes the following components by mass: 45-60 parts silicon dioxide, 8-15 parts boron trioxide, 5-10 parts aluminum oxide, 3-8 parts zirconium oxide, 2-6 parts zinc oxide, 2-6 parts sodium oxide and / or potassium oxide, 2-5 parts calcium oxide, 1-3 parts magnesium oxide, 0.5-2 parts cerium oxide and / or lanthanum oxide, and 0.5-1.5 parts titanium oxide. Before glazing, the glaze undergoes two-stage filtration with sieve mesh sizes of 150 mesh and 300 mesh, respectively, and is degassed for 30 minutes under reduced pressure. The firing kiln is a box-type programmable temperature-controlled kiln with a temperature fluctuation of less than ±3℃.

[0014] As a preferred technical solution, in step S5, the temperature of the high-temperature holding zone during the firing stage is 1300±10℃, the oxygen volume fraction in the furnace atmosphere is maintained at 20~23%, the cooling process is divided into 3 stages of temperature control, the first stage cooling rate is 3℃ / min to 800℃, the second stage cooling rate is 1℃ / min to 500℃, and the third stage is natural cooling to room temperature. The final product is then manually sorted, surface inspected, and dimensionally measured before being stored in the warehouse.

[0015] Beneficial effects This invention constructs a composite structure control system by introducing a specific mass ratio of zirconium oxide and niobium pentoxide, thus avoiding the phase boundary discontinuity problem that may be caused by a single additive. Zirconia, as a polycrystalline grain-refining phase, forms a highly matched crystal structure distribution in the ceramic sintering system coexisting with Nb₂O₅, thereby improving the stability of the multiphase composition within the ceramic matrix.

[0016] This invention adds talc, barium oxide, and magnesium oxide to the structure-regulating components to control their particle size and purity, enabling the system to form a eutectic region with layered structure memory during high-temperature sintering. This promotes the rearrangement and stable transition of the layered silicate phase, avoiding the brittle cracking problem caused by crystal phase distortion in conventional systems.

[0017] This invention utilizes borate-based composite fluxes and rare earth oxides, and sets a mass ratio control range to achieve precise regulation between multivalent ions. By designing the mass ratio of cerium oxide to lanthanum oxide, the crystal phase formed during sintering exhibits more continuous and clearly transitioned grain boundary enrichment zones, avoiding the abnormal crystal growth caused by uneven aggregation at grain boundaries in traditional rare earth doped systems. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of the volume density comparison experiment results of the present invention; Figure 3 This is a schematic diagram of the experimental results comparing the open porosity of the present invention; Figure 4 This is a schematic diagram of the comparative experimental results of the linear expansion coefficient of the present invention; Figure 5 This is a SEM image of Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the insulation breakdown voltage comparison experiment results of the present invention; Figure 7 This is a schematic diagram of the whiteness comparison experiment results of the present invention. Detailed Implementation

[0019] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0020] Experimental group 1 (T1) This embodiment provides an experimental formulation and preparation method for a high-whiteness, high-voltage resistant insulator ceramic material. The steps of the preparation method are as follows: Figure 1 As shown, its formula and parameter settings are based on the aforementioned technical solution, and the proportions of each raw material and process parameters all adopt the lower limit values ​​within the aforementioned range.

[0021] Raw material formula (by total mass, unit: parts): Basic components: 55 parts kaolin, 10 parts feldspar, and 5 parts quartz; Structure-regulating components: 1 part zirconium oxide, 1 part aluminum oxide, 0.2 parts magnesium oxide, 0.1 parts calcium oxide, 0.1 parts barium oxide, 0.2 parts talc, and 0.1 parts niobium pentoxide; Auxiliary phase components: 0.3 parts titanium oxide, 0.2 parts zinc oxide, 0.1 parts borate flux, and 0.05 parts rare earth oxides (the mass ratio of cerium oxide to lanthanum oxide is 1.5:1).

[0022] Preparation method steps: Nano-zirconia (particle size approximately 30 nm) was coated with 0.2% (by mass) of γ-aminopropyltriethoxysilane, and reacted with stirring at 60°C for 1 hour, then dried for later use. Subsequently, it was co-dispersed with niobium pentoxide using sodium polyacrylate as a dispersant, accounting for 0.3% (by mass) of the total solid raw materials, before ball milling, and the pH of the slurry was adjusted to 9.5.

[0023] After mixing all components, deionized water was added, with a solid-liquid ratio of 1:1.2. The mixture was then wet-milled for 12 hours using 3 mm diameter zirconia balls as the milling media, at a ball-to-material ratio of 3:1. After milling, the mixture was allowed to stand for 2 hours to eliminate air bubbles.

[0024] The ball mill slurry was filtered to obtain a mud cake with a moisture content of about 20%. The mud cake was then processed in a vacuum ply mill at 25 rpm for 40 minutes to obtain a uniform plastic mud material.

[0025] The isostatic pressing process was adopted, with the pressure set at 80 MPa and held for 3 minutes. The resulting blank was pre-dried in a humidity-controlled chamber for 12 hours and then allowed to stand and dry for another 24 hours in an environment of 35°C and 45% relative humidity.

[0026] The dried blank is placed in an electric furnace and heated to 850°C at a heating rate of 1°C / min. After holding at that temperature for 1.5 hours, it is allowed to cool naturally.

[0027] The glaze uses a composite oxide glaze system, comprising: 45 parts silica, 8 parts boron trioxide, 5 parts alumina, 3 parts zirconium oxide, 2 parts zinc oxide, 2 parts sodium oxide, 2 parts calcium oxide, 1 part magnesium oxide, 0.5 parts cerium oxide, and 0.5 parts titanium oxide. The glaze is filtered through a double screen (150 mesh and 300 mesh) and degassed under reduced pressure for 30 minutes before being applied through a glazing sprayer with a nozzle orifice diameter of 0.6 mm and a spray pressure controlled at 0.15 MPa. After glazing, it is dried at 80℃ for 6 hours.

[0028] The firing temperature was set at 1280℃, with a heating rate of 2℃ / min and a holding time of 4 hours. The kiln atmosphere was an oxidizing atmosphere, with the oxygen volume fraction controlled at 20%. The cooling stages were performed sequentially: cooling at 3℃ / min to 800℃, cooling at 1℃ / min to 500℃, and then natural cooling to room temperature.

[0029] Experimental group 2 (T2) This embodiment provides a preferred formulation and preparation process for a high-whiteness, high-voltage resistant insulator ceramic material. Based on the technical solution, all components and parameters adopt preferred values ​​within the formulation range, emphasizing the compatibility between component coordination and firing process stability.

[0030] Raw material formula (by total mass, unit: parts): Basic components: 60 parts kaolin, 15 parts feldspar, and 9 parts quartz; Structure-regulating components: 4 parts zirconium oxide, 4 parts aluminum oxide, 0.6 parts magnesium oxide, 0.5 parts calcium oxide, 0.4 parts barium oxide, 0.6 parts talc, and 0.5 parts niobium pentoxide; Auxiliary coordinating phase components: 1.0 part titanium oxide, 0.8 part zinc oxide, 0.5 part borate flux, and 0.2 part rare earth oxides, wherein the mass ratio of cerium oxide to lanthanum oxide is 2:1.

[0031] Preparation method steps: Nano-zirconia powder (50 nm particle size) was coated with γ-aminopropyltriethoxysilane at 0.5% by mass. The reaction conditions were: stirring at 60℃ for 1 hour, followed by drying. It was then co-dispersed with niobium pentoxide using sodium polyacrylate at 0.4% by mass, and the pH of the slurry was adjusted to 10.0. High-shear stirring was used for 25 minutes during the dispersion process.

[0032] After weighing and mixing all raw materials according to the proportion, deionized water was added, the solid-liquid ratio was 1:1.3, and wet ball milling was carried out for 14 hours. The ball milling media were zirconia balls with a diameter of 4 mm, the ball-to-material ratio was 3:1, and the slurry particle size D50 was controlled at about 1.0 μm.

[0033] After filtration, the slurry yields a mud cake with a moisture content of 20%. The mud cake is then processed in a vacuum ply mill at 28 rpm for 45 minutes to ensure uniform mixing and suitable plasticity.

[0034] The molding method is isostatic pressing, with a pressure of 100 MPa and a holding time of 4 minutes. The molded blank is first dried in a humidity-controlled chamber for 14 hours, and then left to dry statically for 36 hours at 40℃ and 50% relative humidity until the moisture content is stable.

[0035] The dried green body was heated to 900℃ at a heating rate of 2℃ / min and bisque fired. After holding at the temperature for 2 hours, it was naturally cooled. The resulting bisque fired green body had a complete structure and no significant cracks.

[0036] The glaze uses a composite oxide glaze system, composed of: 55 parts silicon dioxide, 12 parts boron trioxide, 8 parts aluminum oxide, 5 parts zirconium oxide, 4 parts zinc oxide, 4 parts sodium oxide / potassium oxide, 3 parts calcium oxide, 2 parts magnesium oxide, 1.0 part cerium oxide, and 1.0 part titanium oxide. The glaze is filtered through a double screen of 150 mesh and 300 mesh, and degassed under reduced pressure for 30 minutes.

[0037] The glazing method is spray glazing with a nozzle orifice diameter of 0.8 mm and a spray pressure controlled at 0.2 MPa. After glazing, it is dried at 80℃ for 8 hours, and the glaze surface is uniform and continuous.

[0038] The high-temperature firing temperature was set at 1300℃, with a heating rate of 3℃ / min and a holding time of 5 hours. The firing atmosphere was oxidizing with an oxygen volume fraction of 21%. The cooling stages were as follows: the first stage was a cooling rate of 3℃ / min to 800℃; the second stage was a cooling rate of 1℃ / min to 500℃; and the third stage was natural cooling to room temperature.

[0039] Experimental group 3 (T3) This embodiment provides an upper limit formulation experimental group for a high whiteness high voltage resistant insulator ceramic material. The raw material components and process parameters used are all taken from the highest values ​​of the defined range, aiming to evaluate the structural stability and glaze uniformity of the material system under extreme firing and concentrated component conditions.

[0040] Raw material formula (unit: parts by mass): Basic components: 65 parts kaolin, 20 parts feldspar, 12 parts quartz; Structure-regulating components: 6 parts zirconium oxide, 6 parts aluminum oxide, 1.0 part magnesium oxide, 0.8 parts calcium oxide, 0.6 parts barium oxide, 1.0 part talc, and 1.0 part niobium pentoxide; Auxiliary phase components: 1.5 parts titanium oxide, 1.2 parts zinc oxide, 0.8 parts borate flux, and 0.5 parts rare earth oxides (of which the mass ratio of cerium oxide to lanthanum oxide is 2.5:1).

[0041] Preparation method steps: Zirconia particles with a particle size controlled at 80 nm were coated with 1.0% γ-aminopropyltriethoxysilane by mass, and stirred at 65 °C for 1.5 hours, then dried for later use. Subsequently, it was co-dispersed with niobium pentoxide using 0.5% sodium polyacrylate by mass, the slurry pH was controlled at 10.5, and the high-shear dispersion time was 30 minutes.

[0042] The solid-liquid ratio was set to 1:1.4, and wet ball milling was performed for 16 hours. The ball milling media were zirconia balls with a diameter of 5 mm, the ball-to-material ratio was 3:1, and the slurry particle size D50 was controlled at 1.5 μm.

[0043] The slurry was pressed and filtered into mud cakes with a moisture content of 18%, and then processed in a vacuum mud refining equipment at a speed of 30 rpm for 50 minutes. The resulting mud had good plasticity.

[0044] The isostatic pressing process was adopted, with a pressure of 120 MPa and a holding time of 5 minutes. The formed blank was dried in a humidity-controlled chamber for 16 hours and then left to dry in an environment of 45℃ and 55% relative humidity for 48 hours.

[0045] The green body was heated to 950°C at a heating rate of 3°C / min, held at that temperature for 2 hours, and then naturally cooled. The resulting bisque-fired green body had stable volume and no surface cracks.

[0046] The glaze is a composite oxide glaze system with the following composition: 60 parts silicon dioxide, 15 parts boron trioxide, 10 parts aluminum oxide, 8 parts zirconium oxide, 6 parts zinc oxide, 6 parts sodium oxide and / or potassium oxide, 5 parts calcium oxide, 3 parts magnesium oxide, 2 parts cerium oxide and / or lanthanum oxide, and 1.5 parts titanium oxide.

[0047] The glaze is filtered through a double screen of 150 mesh and 300 mesh, and degassed for 30 minutes under reduced pressure. It is then applied evenly by spraying with a nozzle orifice diameter of 1.0 mm and a glazing pressure of 0.25 MPa. After glazing, it is dried at 80°C for 6 hours.

[0048] The firing temperature was 1320℃, the heating rate was 4℃ / min, and the holding time was 6 hours. The firing atmosphere was oxidizing, and the oxygen volume fraction was maintained at 23%. The cooling stage was divided into three parts: the first step was to reduce the temperature to 800℃ at a rate of 3℃ / min; the second step was to reduce the temperature to 500℃ at a rate of 1℃ / min; and the third step was to allow the temperature to cool naturally to room temperature.

[0049] Control group 1 (C1) This control group was used to verify whether the synergistic effect of niobium pentoxide (Nb2O5) in the structure-regulating components significantly affects the stability of crystal phase boundaries, the integrity of the microstructure, and the microstructure after sintering. Therefore, niobium pentoxide was completely removed from this experimental group, and only zirconium oxide was retained as the core component for structure regulation; the remaining proportions were the same as in experimental group two (T2).

[0050] Raw material formula (unit: parts by mass): Basic components: 60 parts kaolin, 15 parts feldspar, and 9 parts quartz; Structure-regulating components: 4 parts zirconium oxide, 4 parts aluminum oxide, 0.6 parts magnesium oxide, 0.5 parts calcium oxide, 0.4 parts barium oxide, and 0.6 parts talc. Auxiliary phase components: 1.0 part titanium oxide, 0.8 part zinc oxide, 0.5 part borate flux, and 0.2 part rare earth oxide (the mass ratio of cerium oxide to lanthanum oxide is 2:1).

[0051] Preparation method steps: Nano-zirconia (50 nm particle size) was surface-coated with 0.5% γ-aminopropyltriethoxysilane by its mass, and dispersed synergistically with sodium polyacrylate (0.4%), with the pH controlled at 10.0 and high-shear dispersion for 25 minutes. Niobium pentoxide was not added at all, and its corresponding mass fraction was not replaced.

[0052] Subsequent operations, including slurry preparation, ball milling (14 hours), clay refining (28 rpm, 45 minutes), isostatic pressing (100 MPa, holding pressure for 4 minutes), drying (14 hours in a humidity-controlled chamber + 36 hours at 40℃), bisque firing (900℃, holding for 2 hours), glaze application and firing (1300℃, holding for 5 hours), were all consistent with those of the T2 experimental group.

[0053] Control group 2 (C2) This control group was used to verify whether the crystal phase development, sintering density, and structural boundary integrity of the material system would significantly decrease when zirconium oxide was completely removed and only niobium pentoxide was retained in the structural control system, thereby verifying the structural contribution of the synergistic effect of ZrO2–Nb2O5.

[0054] Raw material formula (unit: parts by mass): Basic components: 60 parts kaolin, 15 parts feldspar, and 9 parts quartz; Structure-regulating components: 0.5 parts niobium pentoxide, 4 parts aluminum oxide, 0.6 parts magnesium oxide, 0.5 parts calcium oxide, 0.4 parts barium oxide, and 0.6 parts talc. Auxiliary phase components: 1.0 part titanium oxide, 0.8 part zinc oxide, 0.5 part borate flux, and 0.2 part rare earth oxide (the mass ratio of cerium oxide to lanthanum oxide is 2:1).

[0055] In this experimental group, no zirconium oxide (ZrO2) was added at all, and its corresponding proportions did not replace the addition of other structural components in order to maintain the uniqueness of the variables.

[0056] Preparation method steps: Since no zirconium oxide was added, the surface coating and dispersant treatment were cancelled in this experimental group. Only niobium pentoxide was subjected to high-shear mixing (25 minutes), and the pH value of the slurry was adjusted to 10.0. The remaining treatment process was the same as that of experimental group T2.

[0057] Subsequent processes, including ball milling (14 hours), pressure filtration (20% moisture content), clay refining (28 rpm, 45 minutes), isostatic pressing (100 MPa), drying (14 hours in a humidity control chamber + 36 hours of standing), bisque firing (900℃, 2 hours of holding), glaze composition and glazing method, and high-temperature firing temperature (1300℃, 5 hours of holding), were all consistent with those of experimental group T2.

[0058] Control group 3 (C3) This control group was used to verify the dispersion behavior of nano-zirconia without surface coating treatment and its effect on the sintering structure of ceramic materials, so as to clarify the specific role of zirconia surface modification in inhibiting agglomeration, improving crystal phase distribution and interface structure.

[0059] Raw material formula (unit: parts by mass): Consistent with experimental group 2 (T2): Basic components: 60 parts kaolin, 15 parts feldspar, and 9 parts quartz; Structure-regulating components: 4 parts zirconium oxide, 0.5 parts niobium pentoxide, 4 parts aluminum oxide, 0.6 parts magnesium oxide, 0.5 parts calcium oxide, 0.4 parts barium oxide, and 0.6 parts talc. Auxiliary phase components: 1.0 part titanium oxide, 0.8 part zinc oxide, 0.5 part borate flux, and 0.2 part rare earth oxide (of which the mass ratio of cerium oxide to lanthanum oxide is 2:1).

[0060] Preparation method steps: The zirconium oxide used in this control group was nanoparticles with an average particle size of approximately 50 nm. It was not coated with a silane coupling agent (γ-aminopropyltriethoxysilane) and was directly mixed with the other components. Sodium polyacrylate was still used as a dispersant in the slurry (addition amount 0.4%, pH=10.0). The remaining mixing, ball milling, and slurry treatment processes were the same as in T2. ​​The difference was that no surface coating was applied to the zirconium oxide.

[0061] Ball milling time: 14 hours, ball-to-material ratio: 3:1; slurry D50 particle size: approximately 1.0 μm. After pressure filtration, the slurry was refining at 28 rpm for 45 minutes; it was then isostatically pressed (100 MPa pressure, holding for 4 minutes), dried in a humidity-controlled chamber for 14 hours, followed by drying at 40℃ for 36 hours. The bisque firing temperature was 900℃, held for 2 hours; the high-temperature firing temperature was 1300℃, with a heating rate of 3℃ / min, held for 5 hours, in an oxidizing atmosphere.

[0062] Control group 4 (C4) This control group constructed a reference system using a conventional industrial-grade ceramic insulator material formulation. The raw material system did not contain composite structure-regulating components (such as zirconium oxide, niobium pentoxide, barium oxide, etc.) nor did it introduce auxiliary ligands (such as rare earth oxides, titanium oxide, zinc oxide, etc.). This set of experiments was used to verify the advantages of the ceramic material scheme of this invention compared to traditional ceramic insulator materials in terms of microstructure and ligand stability.

[0063] Raw material formula (unit: parts by mass): Kaolin: 65 parts (contains approximately 0.8% Fe2O3); Feldspar: 20 parts (potassium-sodium ratio not controlled); Quartz powder: 15 parts (industrial grade SiO2 ≥ 96%); Alumina: 3 parts (as a conventional strength-reinforcing phase); There are no other additives, rare earth dopants, or structural fluxing components.

[0064] Preparation method steps: The raw materials were sieved through a 200-mesh sieve, dry-mixed evenly, and then deionized water was added at a solid-liquid ratio of 1:1.2. No dispersants or pH adjusters were added, and the mixture was stirred at room temperature for 12 hours to obtain the slurry. The slurry particle size D50 was approximately 2.5 μm.

[0065] The molding process uses screw extrusion, followed by drying at room temperature for 36 hours. Set the bisque firing temperature to 900℃ and keep it warm for 2 hours; The high-temperature firing temperature is 1300℃, the heating rate is 3℃ / min, the holding time is 5 hours, and the cooling is natural with no atmosphere control equipment.

[0066] Comparative experimental design: To systematically evaluate the differences between the experimental group and the comparative group in terms of structural stability, sintering density, and microstructure, the following comparative experiments were conducted. All samples were formed to the same specifications and sintered using the same procedure. After being processed according to the standard sample preparation process, the physical parameters, microstructure, surface morphology, and interface state were compared and analyzed.

[0067] Experimental steps: Sample preparation and numbering: According to the design schemes of experimental groups T1, T2, T3 and comparative groups C1, C2, C3, C4, ceramic samples were prepared respectively. No less than 6 sintered samples with the same specifications were prepared for each group, and they were marked, numbered and packaged for storage.

[0068] Sampling and polishing: A representative cross-section of the sintered green body was selected, and test pieces were cut out using a metallographic cutting machine. Standard polishing was performed, and the surface roughness was controlled at Ra < 0.1 μm. These samples were used for microscopic analysis and structural testing.

[0069] Sample drying and dehumidification treatment: All samples to be tested were placed in a 60℃ vacuum drying oven for 8 hours to dehumidify. After being taken out and cooled to room temperature, they were put into use to prevent moisture absorption from interfering with electrical properties or physical parameters.

[0070] Main measurement parameters and methods: 1. Bulk density and open porosity: Archimedes method was used to compare the densification degree and pore structure control effect of different systems after sintering.

[0071] 2. Linear thermal expansion coefficient (25~500℃): Thermomechanical analyzer (TMA) was used to measure the temperature range of 25℃~500℃ to evaluate the thermal stability and structural thermal matching ability of different material systems.

[0072] 3. Cross-sectional microstructure observation: Scanning electron microscope (SEM) with accelerating voltage of 10-15 kV to compare the ability of each group to control the microstructure.

[0073] 4. Dielectric breakdown strength test: A ball-plate high-voltage breakdown tester was used; conditions: room temperature, relative humidity <50%, voltage rise rate 1 kV / s; the insulation withstand voltage and density of each group of samples were tested.

[0074] 5. Glaze whiteness index determination: The L value was determined using a reflectance spectrophotometer with standard illumination of D65 and an observation angle of 10°; the compatibility of the glaze system with the body and the surface uniformity were evaluated.

[0075] The experimental results are shown in Table 1: Table 1 Comparison of experimental results data Data Analysis As can be seen from Table 1, there are significant differences between the experimental group and the control group in terms of physical parameters and structural performance: like Figure 2 As shown, in terms of bulk density, the T2 group samples had the highest density at 2.56 g / cm³, followed by T1 and T3 at 2.47 g / cm³ and 2.49 g / cm³, respectively. In contrast, the comparative groups C1–C4 generally had lower densities, with C4 having the lowest (2.28 g / cm³), indicating that conventional formulations or systems lacking structure-regulating components have significant deficiencies in sintering densification.

[0076] like Figure 3 As shown, the open porosity index further confirms the above trend. The porosity of group T2 is 0.31%, which is much lower than the level of more than 0.6% in C1–C4, indicating that it has achieved a high degree of compactness control in terms of formulation composition and particle structure. In particular, the porosity of group C4 is as high as 0.82%, which is the highest overall.

[0077] In terms of thermal stability, the coefficient of linear expansion is a key indicator characterizing the ability to undergo thermal deformation. For example... Figure 4 As shown, the coefficient of linear expansion for group T2 is 4.78 × 10⁻⁶. -6 The coefficient of thermal expansion ( / K) is the smallest among all groups, indicating a compact crystal phase arrangement and strong ability to suppress thermal deformation. Conversely, the coefficients of thermal expansion for groups C2 and C4 are 5.28 × 10⁻⁶ and 5.28 × 10⁻⁶, respectively. -6 / K and 5.35×10 -6 / K, at the highest level, indicates that the thermal response of its crystalline system is unstable.

[0078] Regarding crystal phase homogeneity, such as Figure 5As shown, T2 is "highly uniform", T1 and T3 are also "relatively uniform", while C1–C4 generally have problems such as "non-uniformity", "agglomeration" and even "significant coarsening", indicating that the structure regulation mechanism of the present invention (especially the compounding and dispersion treatment of ZrO2–Nb2O5) plays a key role in the stability of the microstructure.

[0079] like Figure 6 As shown, in terms of electrical performance, the breakdown voltage of group T2 is 40.8 kV / mm, which is significantly better than that of T1 (37.2) and T3 (38.1), and higher than all comparative groups, especially C4 which has the lowest breakdown voltage (27.8). This result indicates that group T2 has the best control in terms of insulation capability, micropore suppression, and grain boundary integrity.

[0080] like Figure 7 As shown, in terms of glaze whiteness, the L value of group T2 is 94.3, which is the highest among all samples, indicating that its raw material purity, phase coordination and glaze reflectivity have been significantly optimized; while group C4 has an L value of 86.8, which shows a more obvious problem of glaze dullness.

[0081] In summary, Group T2 demonstrated superior performance across all six key performance parameters, verifying that the present invention has indeed achieved substantial technological advancements in structural compactness, crystal phase stability, and electrical properties through optimizing the composite structure to regulate the composition, implementing surface coating and pre-dispersion treatment, introducing rare earth stabilizing phases, and coordinating the sintering process.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-whiteness, high-voltage resistant ceramic insulator material, characterized in that, Based on the total mass fraction of raw materials, it consists of the following three types of components: Basic components: 55-65 parts kaolin, 10-20 parts feldspar, 5-12 parts quartz; Structure-regulating components: 1-6 parts zirconium oxide, 1-6 parts aluminum oxide, 0.2-1.0 parts magnesium oxide, 0.1-0.8 parts calcium oxide, 0.1-0.6 parts barium oxide, 0.2-1.0 parts talc, and 0.1-1.0 parts niobium pentoxide; Auxiliary coordinating phase components: 0.3-1.5 parts of titanium oxide, 0.2-1.2 parts of zinc oxide, 0.1-0.8 parts of borate flux, and 0.05-0.5 parts of rare earth oxides, wherein the rare earth oxides include cerium oxide, lanthanum oxide, neodymium oxide, or mixtures thereof.

2. The high-whiteness, high-voltage resistant insulator ceramic material according to claim 1, characterized in that, The mass ratio of zirconium oxide to niobium pentoxide in the structure-regulating component is 5:1 to 10:

1. The zirconium oxide used is nano-zirconia powder with an average particle size of 30-80 nm, which is pre-dispersed with sodium polyacrylate dispersant after being coated with silane coupling agent before use. The coating is made of γ-aminopropyltriethoxysilane (added at 0.2-1.0 wt% of the zirconium oxide mass), which forms a coating layer after constant temperature stirring and drying reaction. The pre-dispersion process is carried out by high shear stirring for 20-30 minutes, and the pH of the slurry is controlled between 9.5 and 10.

5.

3. The high-whiteness, high-voltage resistant insulator ceramic material according to claim 1, characterized in that, In the basic components: Kaolin is a low-iron kaolin with an Fe2O3 mass fraction not exceeding 0.5%. The feldspar is a mixture of potassium feldspar and sodium feldspar, with the potassium-sodium molar ratio controlled between 0.8 and 1.

2. The quartz is high-purity quartz powder, with a SiO2 mass fraction of not less than 98%; Each component was pretreated by 200-mesh sieving and drying before mixing.

4. The high-whiteness, high-voltage resistant insulator ceramic material according to claim 1, characterized in that, In the structure-regulating component: Talc powder is water-washed refined talc, containing Mg3Si4O 10 The (OH)2 content is not less than 90%, and the particle size D50 is controlled between 1 and 4 μm; Magnesium oxide is lightly calcined magnesium oxide powder with a particle size of 2–5 μm; The calcium oxide is high-purity calcium oxide obtained by calcining pure limestone; Barium oxide is obtained by calcining barium carbonate and has a purity of over 98%.

5. The high-whiteness, high-voltage resistant insulator ceramic material according to claim 1, characterized in that, In the auxiliary ligand component: Titanium oxide is an anatase crystalline phase, while zinc oxide is an amorphous phase; The mass ratio of cerium oxide to lanthanum oxide in the rare earth oxide is 1.5:1 to 2.5:1, and the total doping amount is 0.1 to 0.3 parts. The borate flux is a compound system of anhydrous borax and boric acid with a compounding ratio of 3:1 and a particle size of less than 75 μm.

6. A method for preparing the high-whiteness, high-voltage resistant insulator ceramic material according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Raw material mixing: Weigh the basic components, structure regulating components and auxiliary phase components according to the proportion, place all powders in a ball mill jar, add sodium polyacrylate dispersant at a mass of 0.3-0.5% of the total raw material mass, add deionized water at a solid-liquid ratio of 1:1.2-1:1.4, wet ball mill for 12-16 hours, the ball milling media is zirconia balls, the ball-to-material ratio is controlled at 3:1, and the slurry particle size D50 is controlled at 0.5-1.5 μm; S2. Filtration and mud refining: The slurry is pressed into mud cakes with a moisture content of 20±2%. The mud is then continuously refined using a vacuum mud cylinder with the rotation speed controlled at 25-30 rpm and the refining time not less than 40 minutes. S3. Molding: The refined mud is extruded into billets using a vacuum screw extruder, or isostatic pressing is used for molding. The isostatic pressing pressure is controlled at 80-120 MPa, and the holding time is 3-5 minutes. The size fluctuation of the resulting billet does not exceed ±1%. S4. Drying and Firing: The formed blank is placed in an environment of 35-45℃ and 45-55% relative humidity for 24-48 hours to dry. After drying, it is placed in an electric furnace and heated to 850-950℃ at a heating rate of 1-3℃ / min for bisque firing. The temperature is held for 1.5-2 hours. After cooling, the bisque blank is obtained. S5. Glazing and High-Temperature Firing: Apply glaze to the surface of the bisque-fired body by spraying or dipping. The spraying pressure is 0.15–0.25 MPa, and the nozzle orifice diameter is 0.6–1.0 mm. After glazing, dry at 80°C for 6 hours, and then place it in a high-temperature electric furnace for firing. The firing temperature is 1280–1320°C, the heating rate is 2–4°C / min, the holding time is 4–6 hours, the firing atmosphere is an oxidizing atmosphere, and the cooling rate is controlled at 1–2°C / min.

7. The preparation method according to claim 6, characterized in that, In step S1, the milling media are zirconia balls with a diameter of 3 to 5 mm. The slurry is continuously circulated and filtered. The pH value of the slurry is controlled between 9.5 and 10.

5. After milling, the slurry is allowed to settle for no less than 2 hours to remove large air bubbles.

8. The preparation method according to claim 6, characterized in that, In step S3, the mold used for equistatic pressing is a polyurethane-stainless steel composite mold with a pre-set exhaust channel in the mold cavity. The formed blank is placed in a humidity control chamber for slow drying for no less than 12 hours, and the rate of change of relative humidity in the drying chamber is controlled to be no more than 5% / h.

9. The preparation method according to claim 6, characterized in that, The glaze used in step S5 is a composite oxide glaze system, which includes the following components by mass: 45-60 parts silicon dioxide, 8-15 parts boron trioxide, 5-10 parts aluminum oxide, 3-8 parts zirconium oxide, 2-6 parts zinc oxide, 2-6 parts sodium oxide and / or potassium oxide, 2-5 parts calcium oxide, 1-3 parts magnesium oxide, 0.5-2 parts cerium oxide and / or lanthanum oxide, and 0.5-1.5 parts titanium oxide. Before glazing, the product undergoes two-stage sieve filtration, with sieve mesh sizes of 150 mesh and 300 mesh respectively, and is degassed for 30 minutes under reduced pressure. The firing kiln is a box-type programmable temperature control furnace, with internal temperature fluctuations of less than ±3℃.

10. The preparation method according to claim 6, characterized in that, In step S5, the temperature of the high-temperature holding zone during the firing stage is 1300±10℃, and the oxygen volume fraction in the furnace atmosphere is maintained at 20~23%. The cooling process is divided into three temperature control stages: the first stage has a cooling rate of 3℃ / min to 800℃, the second stage has a cooling rate of 1℃ / min to 500℃, and the third stage has a natural cooling to room temperature. The final product is then manually sorted, surface inspected, and dimensionally measured before being stored in the warehouse.

Images