High-dispersion aluminum-doped zinc oxide varistor material and preparation method thereof

Abstract

The invention belongs to the technical field of electronic materials, and particularly discloses a high-dispersion aluminum-doped zinc oxide varistor material and a preparation method thereof. The high-dispersion aluminum-doped zinc oxide varistor material is prepared from the following raw materials in parts by weight: 90 to 92 parts of pretreated zinc oxide, 2 to 3 parts of bismuth trioxide, 0.7 to 0.9 part of cobalt oxide, 1.5 to 1.8 parts of aluminum oxide, 1.2 to 1.5 parts of silicon dioxide, 0.6 to 0.8 part of manganese oxide, 0.07 to 0.09 part of tin oxide and 0.2 to 0.5 part of nickel sesquioxide. The zinc oxide is pretreated, agglomeration of the zinc oxide is reduced, the zinc oxide is subsequently matched with other components, the performance stability of the piezoresistor is improved, the leakage current is reduced, and the service life is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of electronic materials, and in particular to a highly dispersed aluminum-doped zinc oxide varistor material and a preparation method thereof. Background Art

[0002] Zinc oxide varistor is a nonlinear resistor device made of zinc oxide as the main component and prepared by doping with various metal oxides (such as Bi2O3, Co2O3, MnO2, Al2O3, etc.). Its core characteristic is the nonlinearity of its volt-ampere characteristics - it exhibits a high resistance state at low voltage. When the voltage exceeds a specific threshold (varistor voltage), the resistance drops sharply, and it can quickly absorb overvoltage energy. It is widely used in overvoltage protection of electronic equipment and power systems.

[0003] As the core component of lightning arresters, zinc oxide varistors divert lightning into the ground when it strikes power transmission and distribution lines, preventing damage to electrical equipment. They exhibit excellent nonlinear characteristics and high energy absorption capacity, ensuring the safe and stable operation of power lines. The raw materials for zinc oxide varistors are mixed uniformly in a specific ratio and typically undergo processes such as ball milling or sand milling to ensure full dispersion of the components. The green body is then sintered at high temperatures to form a varistor ceramic sheet with specific electrical properties. These ceramic sheets exhibit excellent nonlinear volt-ampere characteristics, fast response speed, and high current capacity.

[0004] The raw materials of zinc oxide varistors usually include nano-scale zinc oxide and other dopants. Nanomaterials have a large specific surface area, high surface energy, and are prone to agglomeration, which will affect the uniformity of the mixture and thus the corresponding performance of the varistor. Summary of the Invention

[0005] In order to improve the problem that raw materials of zinc oxide varistor are prone to agglomeration, the present application provides a highly dispersed aluminum-doped zinc oxide varistor material and a preparation method thereof.

[0006] This application provides a highly dispersed aluminum-doped zinc oxide varistor material, which adopts the following technical solution: A highly dispersed aluminum-doped zinc oxide varistor material comprises the following raw materials, measured in parts by weight: 90-92 parts of pretreated zinc oxide, 2-3 parts of bismuth trioxide, 0.7-0.9 parts of cobalt oxide, 1.5-1.8 parts of aluminum trioxide, 1.2-1.5 parts of silicon dioxide, 0.6-0.8 parts of manganese oxide, 0.07-0.09 parts of tin oxide, and 0.2-0.5 parts of nickel trioxide.

[0007] By adopting the above technical solution, zinc oxide is pretreated to form the matrix material of the varistor. By treating the surface of zinc oxide, the agglomeration of zinc oxide is reduced and the dispersion of zinc oxide powder is improved, ensuring that the grain size is uniform and the distribution is consistent during subsequent sintering, thereby improving the performance stability of the varistor. During the sintering process, bismuth trioxide forms a low-melting-point glass phase between the zinc oxide grains, promoting the stability of the grain boundary structure and sintering densification, while participating in the formation of high-resistance grain boundary barriers, reducing the nonlinear coefficient and resistivity. Cobalt oxide suppresses the electron concentration of zinc oxide grains, reducing leakage current, and improving the aging resistance of the varistor; manganese oxide refines the zinc oxide grains, optimizes the grain boundary microstructure, improves the nonlinear coefficient and reduces leakage current. Nickel trioxide further stabilizes the grain boundary barriers, reduces leakage current at high temperatures, and enhances the stability of the device over a wide temperature range.

[0008] Al in alumina 3+ Substitute Zn in the ZnO lattice 2+ , forming n-type semiconductors, improving the conductivity of zinc oxide grains, while adjusting the grain size and optimizing the uniformity of grain boundary barriers. Moreover, the uniform doping of aluminum depends on the pre-treatment dispersion of zinc oxide, avoiding abnormal grain growth caused by excessive local aluminum concentration, and ensuring the consistency of varistor characteristics. Silicon dioxide reduces the sintering temperature, promotes the densification of the green body, and inhibits the excessive flow of bismuth trioxide glass phase, avoiding uneven grain boundary phase, and improving the mechanical strength of the varistor; Sn in tin oxide 4+ Doping can cooperate with Al 3+ Adjust the electrical conductivity of zinc oxide grains, enhance the nonlinear coefficient, and at the same time improve the thermal conductivity of the material and enhance the heat dissipation efficiency.

[0009] By pre-treating the surface of zinc oxide and combining various additives to avoid powder agglomeration, it is ensured that the components are evenly dispersed in the zinc oxide matrix before sintering, and finally a uniform grain-grain boundary structure is formed, thereby improving the overall performance and consistency of the varistor. 3 + doping regulation combination can increase the α value and enhance the voltage sensitivity characteristics; the composite addition of cobalt oxide, manganese oxide and nickel oxide inhibits grain boundary aging, reduces leakage current and prolongs service life; silicon dioxide promotes densification, and manganese oxide refines the grains, thereby improving the material's ability to resist large current shocks.

[0010] Preferably, the preparation method of the pretreated zinc oxide comprises the following steps: (1) Dispersing zinc oxide in deionized water, adding silane coupling agent KH-560, stirring at a temperature of 55-60° C. for 30-35 minutes, adjusting the pH to 4-5 with glacial acetic acid, filtering, and washing with anhydrous ethanol to obtain treated zinc oxide; (2) dispersing graphene and polyethyleneimine in an ethanol aqueous solution, adding polyvinyl pyrrolidone and aqueous polyurethane, and stirring at a temperature of 65-70° C. for 30-40 minutes to obtain a mixed solution; (3) Dispersing the treated zinc oxide in step (1) in the mixed solution in step (2), ultrasonically dispersing, and spray drying to obtain pretreated zinc oxide.

[0011] By adopting the above technical solution, the silane coupling agent KH-560 undergoes a hydrolysis reaction at pH = 4-5 to generate silanol, which forms a Si-O-Zn covalent bond with the hydroxyl groups on the surface of zinc oxide through dehydration condensation, and grafts organic epoxy groups on the surface of zinc oxide to enhance the interfacial bonding strength, avoid agglomeration, and provide active sites for subsequent reactions with polymers.

[0012] Graphene has excellent conductivity and mechanical properties. Polyethyleneimine adsorbs onto the graphene surface through electrostatic interactions, forming a charge repulsion layer that prevents graphene aggregation. Polyvinylpyrrolidone exhibits good dispersibility and stability, further stabilizing the graphene dispersion through steric hindrance. Its polar groups interact with the KH-560 epoxy groups on the zinc oxide surface, enhancing the compatibility of zinc oxide with the dispersion. Waterborne polyurethane exhibits excellent film-forming and adhesion properties. Its carbamate groups form a hydrogen bond network with polyvinylpyrrolidone, providing flexibility and inhibiting brittle cracking during spray drying. After subsequent spray drying, it forms a thin film coating the zinc oxide surface, enhancing the mechanical strength of the particles while improving their formability within the varistor blank.

[0013] Through three-step treatment, the surface of zinc oxide is silanized, polymerized, and coated with graphene. The final pretreated zinc oxide has good comprehensive performance. The surface organic layer improves the compatibility with other raw materials of the varistor (such as bismuth trioxide, cobalt oxide, etc.); the graphene is evenly dispersed in the coating layer, laying the foundation for the conductive path after subsequent sintering; the spray-dried particles have uniform particle size and good fluidity, which facilitates the molding of the varistor blank, and ultimately improves the nonlinear coefficient, leakage current and other key performance of the varistor.

[0014] Preferably, the mass ratio of the zinc oxide, the silane coupling agent KH-560 and the graphene is 1:0.01-0.02:0.05-0.06.

[0015] By employing this technical solution and further limiting the mass ratio of zinc oxide, silane coupling agent KH-560, and graphene to a specific range, the resulting pretreated zinc oxide exhibits excellent overall performance. The hydrolysis of the silane coupling agent KH-560 generates silanols, which introduce amino functional groups and improve the compatibility of zinc oxide with organic materials. Graphene's primary role in varistors is to enhance conductivity and optimize nonlinear properties. Graphene adheres to the zinc oxide surface through π-π stacking or electrostatic interactions, filling grain boundary defects that occur during the sintering process, increasing the nonlinear coefficient of the varistor and improving the stability of the varistor voltage.

[0016] The surface of zinc oxide modified with silane coupling agent KH-560 has organic groups that can be combined with subsequent polymers, while graphene and zinc oxide are evenly compounded, inhibiting the abnormal growth of zinc oxide grains and improving the stability of the varistor voltage.

[0017] Preferably, the mass ratio of the waterborne polyurethane, polyvinyl pyrrolidone and graphene is 1:0.3-0.4:0.05-0.06.

[0018] By adopting the above technical solution and further limiting the mass ratio of waterborne polyurethane, polyvinyl pyrrolidone, and graphene to a certain range, the resulting pretreated zinc oxide exhibits excellent comprehensive performance. After spray drying, the waterborne polyurethane forms an elastic film that coats the zinc oxide particles, providing the bonding force required for forming the varistor blank and ensuring close bonding between the particles. Polyvinyl pyrrolidone forms a hydrogen bond network with the urethane groups of the waterborne polyurethane, providing flexibility and inhibiting brittle cracking during spray drying. Graphene forms "quantum tunneling" channels at the zinc oxide grain boundaries, improving the nonlinear response speed of the varistor. Graphene is evenly dispersed at the grain boundaries through the waterborne polyurethane-polyvinyl pyrrolidone bond, improving the balance between the nonlinear coefficient and stability of the varistor.

[0019] Preferably, during the spray drying, the air inlet temperature is 120-125°C, and the air outlet temperature is 80-82°C.

[0020] By adopting the above technical solution, the inlet air temperature is set so that the surface and internal moisture of the atomized droplets quickly evaporates when they come into contact with the high-temperature inlet air, ensuring drying efficiency and avoiding particle agglomeration caused by untimely drying. The outlet air temperature is also set to prevent particle agglomeration and performance fluctuations caused by residual moisture during subsequent storage or use.

[0021] The matching of inlet air temperature and outlet air temperature can not only quickly start the drying process through high-temperature inlet air, but also monitor the final drying quality through outlet air temperature. At the same time, they jointly ensure that the material does not suffer component destruction during the drying process, and can form pre-treated zinc oxide particles with uniform particle size and good dispersion, providing stable raw material performance for subsequent applications.

[0022] In the second aspect, the present application also provides a method for preparing a highly dispersed aluminum-doped zinc oxide varistor material, comprising the following steps: uniformly mixing pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum trioxide, silicon dioxide, manganese oxide, tin oxide, and nickel trioxide, adding polyacrylate, carboxymethyl cellulose, and tributyl phosphate, grinding for 10-15 minutes, calcining in a nitrogen atmosphere for 4-5 hours, and sieving to obtain a highly dispersed aluminum-doped zinc oxide varistor material.

[0023] By adopting the above technical solution, polyacrylate is used as an organic binder, and its molecular chain can interact with the organic coating layer (such as water-based polyurethane, polyvinyl pyrrolidone) on the surface of pretreated zinc oxide, thereby enhancing the bonding force between particles and preventing the green body from breaking before grinding or calcination. Carboxymethyl cellulose and polyacrylate form a three-dimensional network to enhance the strength of the green body. At the same time, its hydrophilicity can improve the wettability of the material during grinding, making the solid particles easier to disperse (reducing grinding dead angles). Tributyl phosphate is used as a defoaming agent and dispersing aid. During the grinding process, it can eliminate bubbles introduced when the raw materials are mixed (bubbles will cause cavities to form after calcination, destroying the continuity of grain boundaries). At the same time, by reducing interfacial tension, it promotes the uniform dispersion of metal oxides in the zinc oxide matrix and improves grinding efficiency.

[0024] Calcination in a nitrogen atmosphere prevents oxidation at high temperatures. Sintering causes chemical reactions among the components in the mixture, forming a dense ceramic structure that imparts the desired electrical properties to the varistor. The high temperature burns off organic additives such as polyacrylate and carboxymethyl cellulose, leaving behind a pure ceramic phase. Screening helps improve product reliability and consistency. The resulting highly dispersed aluminum-doped zinc oxide varistor material exhibits high nonlinearity, low leakage current, excellent mechanical properties, and a uniform microstructure, further enhancing performance.

[0025] Preferably, the calcination conditions are: first heating at a temperature of 1000-1050° C. for 2-3 hours, and then keeping warm at 550-600° C. for 1-2 hours.

[0026] By adopting the above technical solution, zinc oxide and other dopants (such as bismuth trioxide and cobalt oxide) undergo a sintering reaction at high temperatures of 1000-1050°C, reducing the distance between the particles and forming a dense ceramic structure, improving the material's mechanical strength and electrical properties. High temperatures promote grain growth, making the material's microstructure more stable. The appropriate increase in grain size can improve the varistor's nonlinear coefficient and breakdown voltage. Organic additives such as polyacrylate and carboxymethyl cellulose completely decompose and volatilize at this temperature, leaving behind a pure ceramic phase.

[0027] Holding at 550-600°C for 1-2 hours further stabilizes the grain boundaries, reduces grain boundary defects, and improves the varistor's electrical properties (such as nonlinear coefficient and leakage current). After high-temperature sintering, thermal stress may exist within the material. Holding at low temperatures can effectively release this stress, reducing the material's internal stress and improving its mechanical properties and stability. The low temperature range may also promote the occurrence of some secondary reactions, further optimizing the material's microstructure and performance.

[0028] By optimizing the calcination conditions during the high- and low-temperature stages, the performance of highly dispersed aluminum-doped zinc oxide varistors can be significantly improved. The high-temperature stage ensures the formation of the microstructure, while the medium-temperature stage optimizes structural stability and stress state. The combination of these two ensures that the varistor has a high nonlinear coefficient, low leakage current, and strong aging resistance.

[0029] Preferably, the calcination conditions are: heating at a rate of 6-8°C / min and cooling at a rate of 10-12°C / min.

[0030] By adopting this technical solution, a slow heating rate (6-8°C / min) ensures uniform heating of the material's interior and exterior, avoiding thermal stress caused by large temperature differences. The slow heating rate also prevents thermal shock in the high-temperature range, reducing cracks and defects. This slow heating ensures that the various raw materials (such as zinc oxide and dopants) gradually react chemically during the heating process, forming a stable intermediate phase.

[0031] A faster cooling rate (10-12°C / min) can effectively release thermal stress within the material and reduce internal stress caused by large temperature differences. Rapid cooling helps quickly stabilize the material's microstructure, reduce defects at grain boundaries, and improve the varistor's electrical properties, such as nonlinear coefficient and leakage current. By optimizing the heating rate (6-8°C / min) and cooling rate (10-12°C / min), the performance of highly dispersed aluminum-doped zinc oxide varistors can be significantly improved.

[0032] Preferably, the mass ratio of the polyacrylate, carboxymethyl cellulose and tributyl phosphate is 1:0.2-0.3:0.07-0.09.

[0033] By adopting the above technical solution and further limiting the mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate within a certain range, the resulting highly dispersed aluminum-doped zinc oxide varistor material exhibits excellent overall performance. The polyacrylate provides the primary viscosity, while the carboxymethyl cellulose acts as a secondary binder. The two work together to improve the moldability of the mixture, ensuring good fluidity during the grinding and molding processes while avoiding excessive viscosity. Tributyl phosphate improves the fluidity of the mixture, making it easier to form a dense structure during sintering, thereby enhancing the mechanical and electrical properties of the varistor.

[0034] The synergistic effect of polyacrylate and carboxymethyl cellulose can improve the flexibility and crack resistance of the varistor. At the same time, the plasticizing effect of tributyl phosphate can further improve its mechanical properties, improve the uniformity of the mixture, and reduce grain boundary defects, thereby increasing the nonlinear coefficient of the varistor, reducing impurities and defects in the sintered material, further reducing leakage current, and significantly improving the formability, sintering performance and final electrical properties of the varistor.

[0035] Preferably, the grinding condition is: the sand mill rotation speed is 3000-3200 r / min.

[0036] By adopting the above technical solution, high-speed (3000-3200r / min) sand milling can provide sufficient mechanical energy to effectively prevent particle agglomeration, evenly disperse the various components, and further refine the particles of zinc oxide and other dopants. Finer particles can increase the specific surface area of ​​the material and improve the density after sintering, thereby improving the electrical properties of the varistor, such as the nonlinear coefficient and leakage current. It ensures that the pre-treated zinc oxide, graphene and metal oxides are evenly mixed at the molecular level in the additive system, laying the foundation for the subsequent calcination to form an excellent microstructure, and ultimately improving the performance consistency and reliability of the varistor.

[0037] In summary, this application has the following beneficial effects: 1. In this application, pretreated zinc oxide is used as the base material of the varistor. By treating the surface of zinc oxide, the agglomeration of zinc oxide is reduced and the dispersion of zinc oxide powder is improved, ensuring that the grain size is uniform and the distribution is consistent during subsequent sintering, thereby improving the performance stability of the varistor.

[0038] 2. In this application, the surface modification of zinc oxide is pretreated and combined with various additives to avoid powder agglomeration and ensure that the components are evenly dispersed in the zinc oxide matrix before sintering, ultimately forming a uniform grain-grain boundary structure and improving the overall performance and consistency of the varistor.

[0039] 3. The composite addition of cobalt oxide, manganese oxide and nickel oxide in this application inhibits grain boundary aging, reduces leakage current and prolongs service life. Silicon dioxide promotes densification, and manganese oxide refines grains and improves the material's ability to resist large current shocks. DETAILED DESCRIPTION

[0040] The present application is further described in detail below with reference to the embodiments.

[0041] The raw materials used in the examples and comparative examples can all be obtained commercially. Example

[0042] Example 1 A highly dispersed aluminum-doped zinc oxide varistor material, comprising the following raw materials by weight: 90g of pretreated zinc oxide, 3g of bismuth trioxide, 0.9g of cobalt oxide, 1.5g of aluminum trioxide, 1.2g of silicon dioxide, 0.6g of manganese oxide, 0.07g of tin oxide, and 0.2g of nickel trioxide; The preparation method of pretreated zinc oxide comprises the following steps: (1) Disperse 100 g of zinc oxide in 150 mL of deionized water, add silane coupling agent KH-560, stir at 58° C. for 32 min, adjust the pH to 5 with glacial acetic acid, filter, and wash with anhydrous ethanol to obtain treated zinc oxide; (2) Graphene and 3 g of polyethyleneimine were dispersed in 360 mL of ethanol-water solution (ethanol to water weight ratio 9:1), polyvinyl pyrrolidone and aqueous polyurethane were added, and the mixture was stirred at 68 °C for 35 min to obtain a mixed solution; (3) Dispersing the treated zinc oxide in step (1) in the mixed solution in step (2), ultrasonically dispersing for 1 hour, and spray drying to obtain pretreated zinc oxide.

[0043] The mass ratio of zinc oxide, silane coupling agent KH-560 and graphene is 1:0.02:0.06.

[0044] The mass ratio of waterborne polyurethane, polyvinyl pyrrolidone and graphene is 1:0.4:0.06.

[0045] During spray drying, the inlet air temperature is 125°C, the outlet air temperature is 82°C, and the atomization pressure is 0.5 MPa.

[0046] The preparation method of the above-mentioned highly dispersed aluminum-doped zinc oxide varistor material includes the following steps: uniformly mixing pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum trioxide, silicon dioxide, manganese oxide, tin oxide, and nickel trioxide, adding polyacrylate, carboxymethyl cellulose, and tributyl phosphate, grinding for 12 minutes, calcining in a nitrogen atmosphere for 4.5 hours, and passing through a 360-mesh sieve to obtain a highly dispersed aluminum-doped zinc oxide varistor material.

[0047] Calcination conditions: first heat at 1050℃ for 3h, then keep at 550℃ for 1h.

[0048] Calcination conditions: heating at a rate of 6°C / min and cooling at a rate of 10°C / min.

[0049] The mass ratio of polyacrylate, carboxymethyl cellulose and tributyl phosphate is 1:0.2:0.09, wherein the polyacrylate is 3 g.

[0050] Grinding conditions: The sand mill speed is 3000r / min.

[0051] Example 2 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that, by weight, it comprises the following raw materials: 92 g of pretreated zinc oxide, 2 g of bismuth trioxide, 0.7 g of cobalt oxide, 1.8 g of aluminum trioxide, 1.5 g of silicon dioxide, 0.8 g of manganese oxide, 0.09 g of tin oxide, and 0.5 g of nickel trioxide.

[0052] The mass ratio of zinc oxide, silane coupling agent KH-560 and graphene is 1:0.01:0.05.

[0053] The mass ratio of waterborne polyurethane, polyvinyl pyrrolidone and graphene is 1:0.3:0.05.

[0054] During spray drying, the inlet air temperature is 120°C and the outlet air temperature is 80°C.

[0055] Calcination conditions: first heat at 1000℃ for 2h, then keep at 600℃ for 2h.

[0056] Calcination conditions: heating at a rate of 8°C / min and cooling at a rate of 12°C / min.

[0057] The mass ratio of polyacrylate, carboxymethyl cellulose and tributyl phosphate is 1:0.3:0.07.

[0058] Grinding conditions: The sand mill speed is 3200 r / min.

[0059] Example 3 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that the silane coupling agent KH-560 is not added in the preparation method of the pretreated zinc oxide.

[0060] Example 4 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that graphene is not added in the preparation method of pre-treating zinc oxide.

[0061] Example 5 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that the mass ratio of zinc oxide, silane coupling agent KH-560 and graphene is 1:0.06:0.01.

[0062] Example 6 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that no water-based polyurethane is added in the preparation method of the pretreated zinc oxide.

[0063] Example 7 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that polyvinyl pyrrolidone is not added in the preparation method of pre-treating zinc oxide.

[0064] Example 8 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that the mass ratio of waterborne polyurethane, polyvinyl pyrrolidone, and graphene is 1:0.05:0.23.

[0065] Example 9 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that polyacrylate is not added in the preparation method of the highly dispersed aluminum-doped zinc oxide varistor material.

[0066] Example 10 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that carboxymethyl cellulose is not added in the preparation method of the highly dispersed aluminum-doped zinc oxide varistor material.

[0067] Example 11 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that tributyl phosphate is not added in the preparation method of the highly dispersed aluminum-doped zinc oxide varistor material.

[0068] Example 12 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that the mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate is 1:0.09:0.16.

[0069] Comparative Example Comparative Example 1 A highly dispersed aluminum-doped zinc oxide varistor material is different from Example 1 in that the pretreated zinc oxide is replaced by an equal amount of zinc oxide.

[0070] Performance testing The performance of the highly dispersed aluminum-doped zinc oxide varistors prepared in Examples 1-12 and Comparative Example 1 was tested; 1. The Zeta potential of the highly dispersed aluminum-doped zinc oxide varistors prepared in Examples and Comparative Example was measured using a Zeta potential meter.

[0071] 2. The highly dispersed aluminum-doped zinc oxide varistor material obtained in the embodiment and the comparative example was pressed into a sheet, and a pressure of 120 MPa was used for 20 seconds. The thickness of the sheet was 1.2 mm and the diameter was 10 mm. The density was tested by the Archimedes drainage method (national standard GB / T 25995-2010); with reference to the test process and test standards of the "AC metal oxide arrester" of the GB / T 11032-2020 standard, the potential gradient (E1mA, V / mm) and leakage current μA of the zinc oxide varistor sheet were tested; the nonlinear coefficient was tested according to GB / T 21431-2015 "Building Lightning Protection Device Part 3: Requirements for Surge Protective Devices (SPD)"; the test results are shown in Table 1.

[0072] Table 1 Test data of embodiments and comparative examples As can be seen from Table 1, the highly dispersed aluminum-doped zinc oxide varistor materials prepared in Examples 1-2 of the present application have good dispersion, density, and electrical properties. Specifically, Example 1 has a zeta potential of -37.65 mV, a density of 98.7%, a potential gradient of 530.87 V / mm, a leakage current of 5 μA, and a nonlinear coefficient of 49.6. It can be seen that the highly dispersed aluminum-doped zinc oxide varistor materials prepared in this application have multiple components that work together synergistically. By pre-treating the surface of zinc oxide and combining various additives to avoid powder agglomeration, the components are uniformly dispersed in the zinc oxide matrix before sintering, ultimately forming a uniform grain-grain boundary structure, improving the overall performance and nonlinear coefficient of the varistor, and reducing leakage current.

[0073] In the preparation methods of pretreated zinc oxide in Examples 3-4, silane coupling agent KH-560 and graphene were not added, respectively. In Example 5, the mass ratio of zinc oxide, silane coupling agent KH-560, and graphene was varied. As can be seen in Table 1, the test results of Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient for Examples 3-4 were significantly worse than those for Examples 1-2, while the test results of the corresponding properties for Example 5 were significantly better than those for Examples 3-4, but worse than those for Examples 1-2. This indicates that the surface of zinc oxide modified with the silane coupling agent KH-560 carries organic groups that can be combined with subsequent polymers, while the graphene is uniformly composited with zinc oxide, inhibiting abnormal growth of zinc oxide grains, improving varistor voltage, enhancing conductivity, and optimizing nonlinear characteristics and stability.

[0074] In the preparation methods of pre-treated zinc oxide in Examples 6-7, no water-based polyurethane and polyvinyl pyrrolidone were added, respectively. In Example 8, the mass ratio of water-based polyurethane, polyvinyl pyrrolidone, and graphene was changed. As can be seen from Table 1, the test results of Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient of Examples 6-7 are significantly worse than those of Examples 1-2, while the test results of the corresponding performance of Example 8 are significantly better than those of Examples 6-7, but worse than those of Examples 1-2, indicating that graphene forms quantum tunneling channels at the grain boundaries of zinc oxide, improving the nonlinear response speed of the varistor, and that graphene is uniformly dispersed at the grain boundaries through water-based polyurethane-polyvinyl pyrrolidone, improving the balance between the nonlinear coefficient and stability of the varistor.

[0075] In the preparation methods of highly dispersed aluminum-doped zinc oxide varistors in Examples 9-11, no polyacrylate, carboxymethyl cellulose, or tributyl phosphate was added, respectively. In Example 12, the mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate was changed. As can be seen in Table 1, the test results of Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient of Examples 9-11 were significantly worse than those of Examples 1-2, while the test results of the corresponding properties of Example 12 were significantly better than those of Examples 9-11, but worse than those of Examples 1-2. This indicates that the synergistic effect of polyacrylate and carboxymethyl cellulose improves the flexibility and crack resistance of the varistor, and the plasticizing effect of tributyl phosphate further improves its mechanical properties, improves the uniformity of the mixture, and reduces grain boundary defects, thereby increasing the nonlinear coefficient of the varistor, reducing impurities and defects in the sintered material, further reducing leakage current, and significantly improving the formability, sintering performance, and final electrical properties of the varistor.

[0076] The pretreated zinc oxide in Comparative Example 1 was replaced by an equal amount of zinc oxide, resulting in a zeta potential of -20.35 mV, a density of 82.5%, a potential gradient of 508.64 V / mm, a leakage current of 19 μA, and a nonlinear coefficient of 30.4. As can be seen in Table 1, the test results of the zeta potential, density, potential gradient, leakage current, and nonlinear coefficient of Comparative Example 1 are significantly worse than those of Examples 1-2, indicating that the pretreated zinc oxide in this application reduces zinc oxide agglomeration and improves the dispersibility of zinc oxide powder, ensuring uniform grain size and consistent distribution during subsequent sintering, thereby improving the performance stability and electrical properties of the varistor.

[0077] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A highly dispersed aluminum-doped zinc oxide varistor material, characterized in that: Calculated by weight, it includes the following raw materials: The pretreatment comprises 90-92 parts of zinc oxide, 2-3 parts of bismuth trioxide, 0.7-0.9 parts of cobalt oxide, 1.5-1.8 parts of aluminum trioxide, 1.2-1.5 parts of silicon dioxide, 0.6-0.8 parts of manganese oxide, 0.07-0.09 parts of tin oxide and 0.2-0.5 parts of nickel trioxide.

2. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 1, characterized in that: The preparation method of the pretreated zinc oxide comprises the following steps: (1) Disperse zinc oxide in deionized water, add silane coupling agent KH-560, stir at a temperature of 55-60°C for 30-35 minutes, adjust the pH to 4-5 with glacial acetic acid, filter, and wash with anhydrous ethanol to obtain treated zinc oxide; (2) dispersing graphene and polyethyleneimine in an ethanol aqueous solution, adding polyvinyl pyrrolidone and aqueous polyurethane, and stirring at a temperature of 65-70°C for 30-40 minutes to obtain a mixed solution; (3) Dispersing the treated zinc oxide in step (1) in the mixed solution in step (2), ultrasonically dispersing, and spray drying to obtain pretreated zinc oxide.

3. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 2, characterized in that: The mass ratio of the zinc oxide, the silane coupling agent KH-560 and the graphene is 1:0.01-0.02:0.05-0.

06.

4. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 2, characterized in that: The mass ratio of the waterborne polyurethane, polyvinyl pyrrolidone and graphene is 1:0.3-0.4:0.05-0.

06.

5. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 2, characterized in that: During the spray drying, the air inlet temperature is 120-125°C, and the air outlet temperature is 80-82°C.

6. The method for preparing a highly dispersed aluminum-doped zinc oxide varistor material according to claim 1, characterized in that: The method comprises the following steps: uniformly mixing pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum trioxide, silicon dioxide, manganese oxide, tin oxide and nickel trioxide, adding polyacrylate, carboxymethyl cellulose and tributyl phosphate, grinding for 10-15 minutes, calcining for 4-5 hours in a nitrogen atmosphere, and sieving to obtain a highly dispersed aluminum-doped zinc oxide varistor material.

7. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 6, characterized in that: The calcination conditions are: first heating at a temperature of 1000-1050° C. for 2-3 hours, and then keeping the temperature at 550-600° C. for 1-2 hours.

8. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 6, characterized in that: The calcination conditions are: heating at a rate of 6-8°C / min and cooling at a rate of 10-12°C / min.

9. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 6, characterized in that: The mass ratio of the polyacrylate, carboxymethyl cellulose and tributyl phosphate is 1:0.2-0.3:0.07-0.

09.

10. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 6, characterized in that: The grinding conditions are as follows: the rotation speed of the sand mill is 3000-3200 r / min.

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