Highly dispersed aluminum-doped zinc oxide varistor material and method for preparing the same
By modifying the surface of zinc oxide and optimizing the sintering process, the problem of nano-sized zinc oxide agglomeration in zinc oxide varistor materials was solved, achieving improved high dispersibility and performance stability, and enhancing the overall performance and consistency of the varistor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU TAIJIE LIGHTNING PROTECTION TECH CO LTD
- Filing Date
- 2025-08-11
- Publication Date
- 2026-07-24
AI Technical Summary
In zinc oxide varistor materials, nano-sized zinc oxide tends to agglomerate, affecting the uniformity of the mixture and the performance of the varistor.
By pretreating the zinc oxide surface, a combination of silane coupling agent KH-560, graphene, waterborne polyurethane and polyvinylpyrrolidone was used for modification. Polyacrylate, carboxymethyl cellulose and tributyl phosphate were used as additives to ensure uniform dispersion of each component. The sintering conditions were optimized by calcination in a nitrogen atmosphere.
This improves the dispersibility of zinc oxide powder, ensures uniform grain size, forms a uniform grain-grain boundary structure, enhances the performance stability, nonlinear coefficient, and mechanical properties of the varistor, reduces leakage current, and extends service life.
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Abstract
Description
Technical Field
[0001] This application relates to the technical field of electronic materials, and in particular to a highly dispersed aluminum-doped zinc oxide varistor material and its preparation method. Background Technology
[0002] Zinc oxide varistors are nonlinear resistive devices made primarily of zinc oxide and doped with various metal oxides (such as Bi2O3, Co2O3, MnO2, Al2O3, etc.). Their core characteristic is the nonlinearity of their current-voltage characteristics—they exhibit high resistance at low voltages, but the resistance drops sharply when the voltage exceeds a specific threshold (varistor voltage), allowing them to quickly absorb overvoltage energy. They are widely used for overvoltage protection in electronic equipment and power systems.
[0003] Zinc oxide varistors, as the core component of surge arresters, attract lightning strikes to the ground when they hit power transmission and distribution lines, preventing damage to power equipment. They possess 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 then typically undergo processes such as ball milling or sand milling to ensure sufficient dispersion of the components. The blank is then sintered at high temperature to form a varistor ceramic sheet with specific electrical properties, exhibiting excellent nonlinear volt-ampere characteristics, fast response speed, and large current capacity.
[0004] The raw materials for zinc oxide varistors typically include nano-sized zinc oxide and other dopants. Nanomaterials have a large specific surface area and high surface energy, making them prone to agglomeration, which can affect the uniformity of the mixture and thus the corresponding performance of the varistor. Summary of the Invention
[0005] To address the issue of agglomeration of raw materials in zinc oxide varistors, this application provides a highly dispersed aluminum-doped zinc oxide varistor material and its preparation method.
[0006] This application provides a highly dispersed aluminum-doped zinc oxide varistor material, employing the following technical solution: A highly dispersed aluminum-doped zinc oxide varistor material, comprising the following raw materials 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 employing the above technical solutions, zinc oxide is pretreated as the matrix material for the varistor. Treating the zinc oxide surface reduces agglomeration and improves the dispersibility of the zinc oxide powder, ensuring uniform grain size and consistent distribution during subsequent sintering, thereby enhancing the performance stability of the varistor. Bismuth trioxide forms a low-melting-point glassy phase between zinc oxide grains during sintering, promoting grain boundary stability and sintering densification. It also participates in the formation of a high-resistivity grain boundary barrier, reducing the nonlinear coefficient and resistivity. Cobalt oxide suppresses the electron concentration of zinc oxide grains, reducing leakage current and improving the varistor's anti-aging performance. Manganese oxide refines zinc oxide grains, optimizes the grain boundary microstructure, improves the nonlinear coefficient, and reduces leakage current. Nickel trioxide further stabilizes the grain boundary barrier, reduces leakage current at high temperatures, and enhances the device's stability over a wide temperature range.
[0008] Al in aluminum oxide 3+ Zn replacing zinc oxide lattice 2+ This process forms an n-type semiconductor, improving the conductivity of zinc oxide grains while adjusting grain size and optimizing the uniformity of grain boundary barriers. Furthermore, the uniform doping of aluminum depends on the pretreatment dispersion of zinc oxide, preventing abnormal grain growth caused by excessively high local aluminum concentrations and ensuring consistent varistor characteristics. Silicon dioxide lowers the sintering temperature, promotes compaction of the green body, and suppresses excessive flow of the bismuth trioxide glass phase, avoiding grain boundary phase inhomogeneity and improving the mechanical strength of the varistor; tin oxide contains Sn... 4+ Doping can synergistically enhance Al 3+ Adjusting the electrical conductivity of zinc oxide grains enhances the nonlinear coefficient and improves the thermal conductivity of the material, thereby increasing heat dissipation efficiency.
[0009] By pretreating and modifying the surface of zinc oxide, and combining various additives, powder agglomeration is avoided, ensuring that all components are uniformly dispersed in the zinc oxide matrix before sintering. This ultimately forms a uniform grain-grain boundary structure, improving the overall performance and consistency of the varistor. The grain boundary barrier formed by bismuth trioxide interacts with Al... 3 The combination of doping and regulation can improve the α value and enhance voltage sensitivity; the composite addition of cobalt oxide, manganese oxide and nickel trioxide inhibits grain boundary aging, reduces leakage current and extends service life; silicon dioxide promotes densification and manganese oxide refines grains, improving the material's ability to withstand high current impacts.
[0010] Preferably, the method for preparing the pretreated zinc oxide includes the following steps: (1) Disperse zinc oxide in deionized water, add silane coupling agent KH-560, stir at 55-60℃ for 30-35 min, adjust pH to 4-5 with glacial acetic acid, filter, wash with anhydrous ethanol to obtain treated zinc oxide. (2) Graphene and polyethyleneimine are dispersed in an aqueous ethanol solution, polyvinylpyrrolidone and waterborne polyurethane are added, and the mixture is stirred at 65-70℃ for 30-40 minutes to obtain a mixture. (3) Disperse the treated zinc oxide from step (1) in the mixture from step (2), ultrasonically disperse, and spray dry 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 zinc oxide surface through dehydration condensation. Organic epoxy groups are grafted onto the zinc oxide surface to enhance the interfacial bonding force, prevent agglomeration, and provide active sites for subsequent reactions with polymers.
[0012] Graphene possesses excellent electrical conductivity and mechanical properties. Polyethyleneimine is adsorbed onto the graphene surface via electrostatic interactions, forming a charge-repellent layer that prevents graphene aggregation. Polyvinylpyrrolidone (PVP) exhibits good dispersibility and stability, further stabilizing the graphene dispersion through steric hindrance. Simultaneously, its polar groups interact with the KH-560 epoxy groups on the zinc oxide surface, enhancing the compatibility between zinc oxide and the dispersion. Waterborne polyurethane demonstrates good film-forming and adhesive properties. Its urethane groups form a hydrogen-bonded network with PPVP, providing flexibility and inhibiting spray-drying brittleness. After subsequent spray drying, it forms a thin film coating the zinc oxide surface, enhancing the mechanical strength of the particles and improving their formability within the varistor preform.
[0013] Through a three-step process, zinc oxide surface undergoes silanization modification, polymerization, and graphene coating. The resulting pretreated zinc oxide exhibits good overall performance. The surface organic layer improves compatibility with other raw materials for varistors (such as bismuth trioxide and cobalt oxide). Graphene is uniformly 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 flowability, facilitating the forming of the varistor blank and ultimately improving key performance characteristics such as the nonlinear coefficient and leakage current of the varistor.
[0014] Preferably, the mass ratio of zinc oxide, silane coupling agent KH-560 and graphene is 1:0.01-0.02:0.05-0.06.
[0015] By employing the above technical solution and further limiting the mass ratio of zinc oxide, silane coupling agent KH-560, and graphene within a certain range, the pretreated zinc oxide obtained exhibits excellent comprehensive performance. After hydrolysis, the silane coupling agent KH-560 generates silanol, introducing amino functional groups and improving the compatibility of zinc oxide with organic materials. The main role of graphene in the varistor is to enhance conductivity and optimize nonlinear characteristics. Graphene is adsorbed onto the zinc oxide surface through π-π stacking or electrostatic interactions, filling grain boundary defects that occur during sintering, improving the nonlinear coefficient of the varistor, and enhancing the stability of the varistor voltage.
[0016] The zinc oxide surface modified by silane coupling agent KH-560 has organic groups that can combine with subsequent polymers. The uniform composite of graphene and zinc oxide inhibits the abnormal growth of zinc oxide grains and improves the stability of the varistor voltage.
[0017] Preferably, the mass ratio of the waterborne polyurethane, polyvinylpyrrolidone, 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, polyvinylpyrrolidone, and graphene within a certain range, the pretreated zinc oxide obtained exhibits excellent comprehensive performance. After spray drying, the waterborne polyurethane forms an elastic film coating the zinc oxide particles, providing the necessary bonding force for the varistor preform and ensuring tight interparticle bonding. Polyvinylpyrrolidone forms a hydrogen bond network with the urethane groups of the waterborne polyurethane, providing flexibility and inhibiting spray-drying brittleness. Graphene forms "quantum tunneling" channels at the zinc oxide grain boundaries, improving the nonlinear response speed of the varistor. The graphene is uniformly dispersed at the grain boundaries through the waterborne polyurethane-polyvinylpyrrolidone mixture, enhancing the balance between the nonlinear coefficient and stability of the varistor.
[0019] Preferably, in the spray drying process, the inlet air temperature is 120-125℃ and the outlet air temperature is 80-82℃.
[0020] By adopting the above technical solution and setting the inlet air temperature, the atomized droplets rapidly evaporate surface and internal moisture upon contact with the high-temperature inlet air, ensuring drying efficiency and preventing particle agglomeration due to untimely drying. Setting the outlet air temperature prevents particle clumping and performance fluctuations caused by residual moisture during subsequent storage or use.
[0021] Matching the inlet and outlet air temperatures allows for rapid initiation of the drying process via high-temperature inlet air, while also enabling monitoring of the final drying quality via outlet air temperature. This ensures that the material does not suffer component damage during the drying process and forms pretreated zinc oxide particles with uniform particle size and good dispersibility, providing stable raw material performance for subsequent applications.
[0022] Secondly, this application also provides a method for preparing a highly dispersed aluminum-doped zinc oxide varistor material, comprising the following steps: mixing pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum oxide, silicon dioxide, manganese oxide, tin oxide, and nickel oxide evenly, adding polyacrylate, carboxymethyl cellulose, and tributyl phosphate, grinding for 10-15 min, calcining in a nitrogen atmosphere for 4-5 h, and sieving to obtain a highly dispersed aluminum-doped zinc oxide varistor material.
[0023] By employing the above technical solutions, polyacrylate, as an organic binder, allows its molecular chains to interact with the organic coating layer (such as waterborne polyurethane or polyvinylpyrrolidone) on the surface of pretreated zinc oxide, enhancing the adhesion between particles and preventing the green body from crumbling before grinding or calcination. Carboxymethyl cellulose forms a three-dimensional network with polyacrylate, improving the strength of the green body. Simultaneously, its hydrophilicity improves the wettability of the material during grinding, making solid particles easier to disperse (reducing grinding dead zones). Tributyl phosphate, as an defoamer and dispersant, eliminates air bubbles introduced during raw material mixing during grinding (air bubbles can lead to voids after calcination, disrupting grain boundary continuity). Simultaneously, by reducing interfacial tension, it promotes the uniform dispersion of metal oxides in the zinc oxide matrix, improving grinding efficiency.
[0024] Calcination in a nitrogen atmosphere prevents oxidation of the mixture at high temperatures. Sintering allows the components in the mixture to react chemically, forming a dense ceramic structure that imparts the required electrical properties to the varistor. High temperatures burn off organic additives such as polyacrylate and carboxymethyl cellulose, leaving a pure ceramic phase. Sieving further improves product reliability and consistency. The resulting highly dispersed aluminum-doped zinc oxide varistor material exhibits a high nonlinear coefficient, low leakage current, good mechanical properties, and a uniform microstructure, further enhancing its performance.
[0025] Preferably, the calcination conditions are: first, heating at 1000-1050℃ for 2-3 hours, and then holding at 550-600℃ for 1-2 hours.
[0026] By employing 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℃, reducing the distance between particles and forming a dense ceramic structure, thereby improving the mechanical strength and electrical properties of the material. High temperatures promote grain growth, making the material's microstructure more stable; appropriately increasing the grain size can improve the nonlinear coefficient and breakdown voltage of the varistor. Organic additives such as polyacrylate and carboxymethyl cellulose completely decompose and volatilize at this temperature, leaving behind a pure ceramic phase.
[0027] Holding the material at 550-600℃ for 1-2 hours further stabilizes the grain boundaries, reduces grain boundary defects, and improves the electrical performance of the varistor (such as nonlinear coefficient and leakage current). After high-temperature sintering, thermal stress may exist inside the material; low-temperature holding can effectively release these stresses, reduce internal stress, and improve its mechanical properties and stability. The low-temperature stage may promote some secondary reactions, further optimizing the microstructure and properties of the material.
[0028] By optimizing the calcination conditions at both high and low temperatures, 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 aspects enables the varistor to simultaneously possess a high nonlinear coefficient, low leakage current, and strong aging resistance.
[0029] Preferably, the calcination conditions are: heating at a rate of 6-8℃ / min and cooling at a rate of 10-12℃ / min.
[0030] By adopting the above technical solution, a slower heating rate (6-8℃ / min) ensures uniform heating both inside and outside the material, avoiding thermal stress caused by excessive temperature differences. The slower heating rate also prevents thermal shock at high temperatures, reducing the formation of cracks and defects. Slow heating ensures that the raw materials (such as zinc oxide and dopants) undergo gradual chemical reactions during the heating process, forming a stable intermediate phase.
[0031] A rapid cooling rate (10⁻¹² °C / min) can effectively release internal thermal stress in the material and reduce internal stress caused by excessive temperature differences. Rapid cooling helps to quickly fix the microstructure of the material, reduce defects at grain boundaries, and improve the electrical performance of the varistor, such as the 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 varistor materials can be significantly improved.
[0032] Preferably, the mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate is 1:0.2-0.3:0.07-0.09.
[0033] By employing 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 comprehensive performance. Polyacrylate provides the primary viscosity, while carboxymethyl cellulose acts as an auxiliary binder; their combined effect improves the formability of the mixture, ensuring good flowability during grinding and molding while avoiding excessive viscosity. Tributyl phosphate improves the flowability 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 varistor. At the same time, the plasticizing effect of tributyl phosphate can further improve its mechanical properties, improve the uniformity of the mixture, reduce grain boundary defects, thereby improving the nonlinear coefficient of varistor, reducing impurities and defects in the sintered material, further reducing leakage current, and significantly improving the formability, sintering performance and final electrical performance of varistor.
[0035] Preferably, the grinding conditions are: the grinding speed is 3000-3200 r / min.
[0036] By adopting the above technical solution, high-speed (3000-3200 r / min) sand milling can provide sufficient mechanical energy to effectively prevent particle agglomeration, ensure uniform dispersion of each component, 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 performance of the varistor, such as the nonlinear coefficient and leakage current. It also ensures that the pretreated zinc oxide, graphene, and metal oxides are uniformly mixed at the molecular level in the additive system, laying the foundation for the formation of an excellent microstructure in subsequent calcination, 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 matrix material of the varistor. By treating the surface of zinc oxide, the agglomeration of zinc oxide is reduced and the dispersibility 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 through pretreatment, combined with various additives, avoids powder agglomeration and ensures that each component is uniformly dispersed in the zinc oxide matrix before sintering, ultimately forming a uniform grain-grain boundary structure, thereby 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 extends service life. Silica promotes densification, and manganese oxide refines grains, thereby improving the material's resistance to high current impact. Detailed Implementation
[0040] The present application will be further described in detail below with reference to the embodiments.
[0041] The raw materials used in the examples and comparative examples are all commercially available. Example
[0042] Example 1 A highly dispersed aluminum-doped zinc oxide varistor material, by weight, comprises the following raw materials: 90g pretreated zinc oxide, 3g bismuth trioxide, 0.9g cobalt oxide, 1.5g aluminum trioxide, 1.2g silicon dioxide, 0.6g manganese oxide, 0.07g tin oxide, and 0.2g nickel trioxide; The method for preparing pretreated zinc oxide includes the following steps: (1) Disperse 100g of zinc oxide in 150mL of deionized water, add silane coupling agent KH-560, stir at 58℃ for 32min, adjust pH=5 with glacial acetic acid, filter, wash with anhydrous ethanol to obtain treated zinc oxide. (2) Graphene and 3g of polyethyleneimine were dispersed in 360mL of ethanol aqueous solution (ethanol to water weight ratio 9:1), polyvinylpyrrolidone and waterborne polyurethane were added, and the mixture was stirred at 68℃ for 35min to obtain a mixture. (3) Disperse the treated zinc oxide from step (1) in the mixture from step (2), ultrasonically disperse for 1 hour, and spray dry 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, polyvinylpyrrolidone, and graphene is 1:0.4:0.06.
[0045] During spray drying, the inlet air temperature is 125℃, the outlet air temperature is 82℃, and the atomization pressure is 0.5MPa.
[0046] The preparation method of the above-mentioned highly dispersed aluminum-doped zinc oxide varistor material includes the following steps: pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum oxide, silicon dioxide, manganese oxide, tin oxide, and nickel oxide are mixed evenly, polyacrylate, carboxymethyl cellulose, and tributyl phosphate are added, ground for 12 min, calcined in a nitrogen atmosphere for 4.5 h, and passed through a 360-mesh sieve to obtain the highly dispersed aluminum-doped zinc oxide varistor material.
[0047] Calcination conditions: first heat at 1050℃ for 3 hours, then hold at 550℃ for 1 hour.
[0048] Calcination conditions: Heating at a rate of 6℃ / min and cooling at a rate of 10℃ / min.
[0049] The mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate is 1:0.2:0.09, of which 3g is polyacrylate.
[0050] Grinding conditions: The grinding speed of the sand mill is 3000 r / 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: 92g of pretreated zinc oxide, 2g of bismuth trioxide, 0.7g of cobalt oxide, 1.8g of aluminum trioxide, 1.5g of silicon dioxide, 0.8g of manganese oxide, 0.09g of tin oxide, and 0.5g 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, polyvinylpyrrolidone, and graphene is 1:0.3:0.05.
[0054] During spray drying, the inlet air temperature is 120℃ and the outlet air temperature is 80℃.
[0055] Calcination conditions: First heat at 1000℃ for 2 hours, then hold at 600℃ for 2 hours.
[0056] Calcination conditions: Heating at a rate of 8℃ / min and cooling at a rate of 12℃ / min.
[0057] The mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate is 1:0.3:0.07.
[0058] Grinding conditions: The grinding speed of the sand mill is 3200 r / min.
[0059] Example 3 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that the preparation method of the pretreated zinc oxide does not include the silane coupling agent KH-560.
[0060] Example 4 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that graphene is not added in the preparation method of the pretreated zinc oxide.
[0061] Example 5 A highly dispersed aluminum-doped zinc oxide varistor material differs 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 differs from Example 1 in that waterborne polyurethane is not added in the preparation method of the pretreated zinc oxide.
[0063] Example 7 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that polyvinylpyrrolidone is not added in the preparation method of the pretreated 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, polyvinylpyrrolidone, and graphene is 1:0.05:0.23.
[0065] Example 9 A highly dispersed aluminum-doped zinc oxide varistor material differs from Example 1 in that the preparation method of the highly dispersed aluminum-doped zinc oxide varistor material does not include polyacrylate.
[0066] Example 10 A highly dispersed aluminum-doped zinc oxide varistor material differs 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 differs from Example 1 in that the preparation method of the highly dispersed aluminum-doped zinc oxide varistor material does not include tributyl phosphate.
[0068] Example 12 A highly dispersed aluminum-doped zinc oxide varistor material differs 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 differs from Example 1 in that the pretreated zinc oxide is replaced by an equal amount of zinc oxide.
[0070] Performance testing The highly dispersed aluminum-doped zinc oxide varistor materials prepared in Examples 1-12 and Comparative Example 1 were subjected to performance tests; 1. The zeta potential of the highly dispersed aluminum-doped zinc oxide varistor materials prepared in Examples and Comparative Examples was measured using a zeta potentiometer.
[0071] 2. The highly dispersed aluminum-doped zinc oxide varistor material prepared in the examples and comparative examples was pressed into sheets. A pressure of 120 MPa was applied and held for 20 seconds. The thickness of the pressed sheets was 1.2 mm and the diameter was 10 mm. The density was tested using Archimedes' drainage method (GB / T 25995-2010). Referring to the test procedures and standards of GB / T 11032-2020 "AC Metal Oxide Surge Arresters", 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 "Lightning Protection Devices for Buildings Part 3: Requirements for Surge Protective Devices (SPDs)". The test results are shown in Table 1.
[0072] Table 1 Test data for the examples and comparative examples As shown in Table 1, the highly dispersed aluminum-doped zinc oxide varistor materials prepared in Examples 1-2 of this application exhibit good dispersibility, density, and electrical properties. Specifically, Example 1 shows 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 is evident that the highly dispersed aluminum-doped zinc oxide varistor materials prepared in this application utilize the synergistic effect of multiple components. Through surface modification of pretreated zinc oxide and the combination of various additives, powder agglomeration is avoided, ensuring that each component is uniformly dispersed in the zinc oxide matrix before sintering. This ultimately forms a uniform grain-grain boundary structure, improving the overall performance and nonlinear coefficient of the varistor and reducing leakage current.
[0073] In Examples 3-4, the pretreated zinc oxide preparation methods did not include silane coupling agent KH-560 or graphene, respectively. In Example 5, the mass ratio of zinc oxide, silane coupling agent KH-560, and graphene was changed. Table 1 shows that the test results for Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient in Examples 3-4 were significantly worse than those in Examples 1-2. In contrast, the test results for the corresponding performance in Example 5 were significantly better than those in Examples 3-4, but worse than those in Examples 1-2. This indicates that the zinc oxide surface modified with silane coupling agent KH-560 has organic groups that can combine with subsequent polymers. Furthermore, the uniform composite of graphene and zinc oxide inhibits abnormal growth of zinc oxide grains, improving the conductivity of the varistor voltage, optimizing nonlinear characteristics, and enhancing stability.
[0074] In Examples 6-7, the pretreated zinc oxide preparation methods did not include waterborne polyurethane or polyvinylpyrrolidone, respectively. In Example 8, the mass ratio of waterborne polyurethane, polyvinylpyrrolidone, and graphene was changed. Table 1 shows that the test results for Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient in Examples 6-7 were significantly worse than those in Examples 1-2. In contrast, the test results for the corresponding performance in Example 8 were significantly better than those in Examples 6-7, but worse than those in Examples 1-2. This indicates that graphene forms quantum tunneling channels at the zinc oxide grain boundaries, improving the nonlinear response speed of the varistor. Graphene is uniformly dispersed at the grain boundaries through waterborne polyurethane-polyvinylpyrrolidone, improving the balance between the nonlinear coefficient and stability of the varistor.
[0075] In Examples 9-11, the preparation methods of highly dispersed aluminum-doped zinc oxide varistors did not include polyacrylate, carboxymethyl cellulose, or tributyl phosphate, respectively. In Example 12, the mass ratio of polyacrylate, carboxymethyl cellulose, and tributyl phosphate was changed. Table 1 shows that the test results for Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient in Examples 9-11 were significantly worse than those in Examples 1-2. In contrast, the test results for the corresponding performance in Example 12 were significantly better than those in Examples 9-11, but worse than those in Examples 1-2. This indicates that the synergistic effect of polyacrylate and carboxymethyl cellulose improves the flexibility and crack resistance of the varistor, while the plasticizing effect of tributyl phosphate further improves its mechanical properties, enhances the uniformity of the mixture, and reduces grain boundary defects, thereby increasing the nonlinear coefficient of the varistor. This also reduces impurities and defects in the sintered material, further reducing leakage current and significantly improving the formability, sintering performance, and final electrical performance of the varistor.
[0076] In Comparative Example 1, the pretreated zinc oxide 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. Table 1 shows that the test results for Zeta potential, density, potential gradient, leakage current, and nonlinear coefficient in Comparative Example 1 are significantly worse than those in Examples 1-2. This indicates that the pretreated zinc oxide in this application reduces zinc oxide agglomeration and improves the dispersibility of the zinc oxide powder, ensuring uniform grain size and consistent distribution during subsequent sintering, thereby enhancing the performance stability and electrical properties of the varistor.
[0077] This specific embodiment is merely an explanation of this application and is not intended to limit it. 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 fall within the scope of the claims of this application.
Claims
1. A highly dispersed aluminum-doped zinc oxide varistor material, characterized in that, By weight, it includes the following ingredients: Pretreatment: 90-92 parts zinc oxide, 2-3 parts bismuth trioxide, 0.7-0.9 parts cobalt oxide, 1.5-1.8 parts aluminum trioxide, 1.2-1.5 parts silicon dioxide, 0.6-0.8 parts manganese oxide, 0.07-0.09 parts tin oxide, and 0.2-0.5 parts nickel trioxide; The method for preparing the pretreated zinc oxide includes the following steps: (1) Disperse zinc oxide in deionized water, add silane coupling agent KH-560, stir at 55-60℃ for 30-35 min, adjust pH to 4-5 with glacial acetic acid, filter, wash with anhydrous ethanol to obtain treated zinc oxide. (2) Graphene and polyethyleneimine are dispersed in an ethanol aqueous solution, polyvinylpyrrolidone and waterborne polyurethane are added, and the mixture is stirred at 65-70℃ for 30-40 min to obtain a mixture. (3) Disperse the treated zinc oxide from step (1) in the mixture from step (2), ultrasonically disperse, and spray dry to obtain pretreated zinc oxide; The mass ratio of zinc oxide, silane coupling agent KH-560, and graphene is 1:0.01-0.02:0.05-0.06; The mass ratio of the waterborne polyurethane, polyvinylpyrrolidone, and graphene is 1:0.3-0.4:0.05-0.
06.
2. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 1, characterized in that, In the spray drying process, the inlet air temperature is 120-125℃ and the outlet air temperature is 80-82℃.
3. The method for preparing a highly dispersed aluminum-doped zinc oxide varistor material according to claim 1, characterized in that, The process includes the following steps: pretreated zinc oxide, bismuth trioxide, cobalt oxide, aluminum oxide, silicon dioxide, manganese oxide, tin oxide, and nickel oxide are mixed evenly, polyacrylate, carboxymethyl cellulose, and tributyl phosphate are added, the mixture is ground for 10-15 minutes, calcined in a nitrogen atmosphere for 4-5 hours, and then sieved to obtain a highly dispersed aluminum-doped zinc oxide varistor material.
4. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 3, characterized in that, The calcination conditions are as follows: first, heat at 1000-1050℃ for 2-3 hours, then hold at 550-600℃ for 1-2 hours.
5. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 3, characterized in that, The calcination conditions are as follows: heating at a rate of 6-8℃ / min and cooling at a rate of 10-12℃ / min.
6. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 3, characterized in that, The mass ratio of the polyacrylate, carboxymethyl cellulose, and tributyl phosphate is 1:0.2-0.3:0.07-0.
09.
7. The highly dispersed aluminum-doped zinc oxide varistor material according to claim 3, characterized in that, The grinding conditions are as follows: the grinding speed is 3000-3200 r / min.