Metal oxide resistor disc and preparation process thereof

Abstract

The invention relates to the field of resistor discs, and particularly discloses a metal oxide resistor disc and a preparation process thereof, and the preparation process comprises the following steps: S1, mixing zinc oxide, antimony trioxide, chromium sesquioxide, manganese dioxide, aluminum nitrate and silver nitrate to prepare a slurry, adding a surface modifier, and mixing to prepare a mixed slurry; s2, drying the mixed slurry to obtain prefabricated powder, pre-sintering the prefabricated powder to obtain a pre-sintered mixture, grinding the pre-sintered mixture, and drying the ground pre-sintered mixture to obtain additive composite powder; s3, manganese carbonate, bismuth trioxide, nickel oxide and cobaltosic oxide are mixed to serve as an additive mixture, a tin dichloride solution is added, and a mixed solution to be deposited is prepared after stirring; s4, mixing the to-be-deposited mixed solution with an adhesive, absolute ethyl alcohol and additive composite powder, then drying, carrying out compression molding, and then carrying out calcination treatment; and S5, performing post-treatment to obtain the metal oxide resistor disc. The resistor disc has the advantages that the porosity of the resistor disc is reduced, the through-flow capacity is improved, and the electrical performance is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of resistance disc, more particularly, it relates to a metal oxide resistance disc and a preparation process thereof. BACKGROUND

[0002] As a key component in power systems, metal oxide resistance disc plays an irreplaceable role in the field of overvoltage protection. During the operation of power grids, abnormal situations such as lightning strikes and operating overvoltages are inevitable, which may cause serious damage to power equipment and affect the stable operation of power systems. Metal oxide resistance disc, with its excellent nonlinear voltage-current characteristics, can present a high resistance state under normal operating voltage to limit the current flow, and quickly change to a low resistance state to release the overvoltage energy when overvoltage occurs, thereby protecting power equipment from damage. It is widely used in lightning arresters, surge protectors and other devices, and is an important defense line to ensure the safe and stable operation of power systems.

[0003] The traditional preparation process of metal oxide resistance disc mainly includes basic steps such as raw material mixing, molding and sintering. In the raw material mixing stage, various metal oxide powders are simply mixed in a certain proportion; in the molding process, the mixed powders are formed into a certain shape by pressing or other methods; finally, after high-temperature sintering, the green body is densified to form a resistance disc with specific performance.

[0004] However, the metal oxide resistance disc prepared by the traditional process generally has a high porosity problem. The existence of pores will significantly affect the performance of the resistance disc. From the electrical performance point of view, pores will destroy the uniformity of the microstructure of the resistance disc, resulting in poor nonlinear voltage-current characteristics, reduced limiting voltage and current-carrying capacity, and inability to effectively play the role of overvoltage protection. In terms of mechanical performance, pores will become stress concentration points, reducing the mechanical strength of the resistance disc, making it more prone to breakage under external force or thermal stress, and shortening the service life. In addition, high porosity will also affect the thermal stability of the resistance disc. When a large amount of heat is generated by overvoltage, pores will hinder the conduction of heat, causing the local temperature to be too high, further damaging the performance of the resistance disc.

[0005] Therefore, how to reduce the porosity of the resistance disc and thus improve its current-carrying capacity is crucial to improving the performance of the resistance disc. SUMMARY

[0006] In order to reduce the porosity of the resistance disc and thus improve its current-carrying capacity and electrical performance, the present application provides a metal oxide resistance disc and a preparation process thereof.

[0007] In the first aspect, the present application provides a preparation process of a metal oxide resistance disc, which adopts the following technical scheme: A fabrication process for a metal oxide resistor includes the following steps: S1. Material preparation: Prepare materials containing at least zinc oxide, antimony trioxide, bismuth trioxide, cobalt tetroxide, chromium trioxide, manganese dioxide, nickel oxide, manganese carbonate, aluminum nitrate, and silver nitrate as raw materials for metal oxide resistors. A slurry was prepared by mixing zinc oxide, antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate, and silver nitrate. A surface modifier was added to the slurry, and the mixture was then prepared to obtain a mixed slurry. S2. After drying the mixed slurry obtained in step S1, a pre-formed powder is obtained. Then, the pre-formed powder is pre-calcined at 600-800℃ for 2-3 hours to obtain a pre-calcined mixture. After grinding and drying, an additive composite powder is obtained. S3. Manganese carbonate, bismuth trioxide, nickel oxide and cobalt tetroxide are mixed together as an additive mixture. Tin dichloride solution is added to the additive mixture and stirred to obtain the mixture to be deposited. S4. The mixture to be deposited is mixed with binder, anhydrous ethanol and additive composite powder, dried, pressed into shape and then calcined. S5. Post-processing to obtain metal oxide resistor sheets.

[0008] By employing the above technical solution, the reasons for the high porosity of the resistor sheet were investigated. One reason is that the traditional process involves simple raw material mixing, making it difficult to achieve molecular-level uniform mixing of metal oxide powders. In particular, different components of the additives and metal oxide powders tend to aggregate in localized areas, leading to inconsistent shrinkage during sintering and thus generating porosity. Therefore, in this application, when preparing the mixed slurry, multiple metal oxides are first mixed with aluminum nitrate, and a surface modifier is added. Through thorough stirring, the basic components are initially uniformly mixed.

[0009] Then, additives such as manganese carbonate, bismuth oxide, nickel oxide, and cobalt oxide are mixed and added to a tin dichloride solution for stirring to achieve initial uniform distribution. The tin dichloride solution acts as a lubricant, reducing adhesion and breakage of the resistor sheet during molding and sintering. More importantly, the solubility and reactivity of tin dichloride further mixes with the above-mentioned additive raw materials at the molecular level, which helps the additives to be uniformly dispersed in the solution, forming a more uniform mixture to be deposited. This uniform dispersion is maintained during subsequent drying and sintering processes, thus ensuring the uniform distribution of additives in the resistor sheet and facilitating the uniform precipitation of additive substances during subsequent sintering. Moreover, after the additives such as manganese carbonate, bismuth oxide, nickel oxide, and cobalt oxide are mixed and added to the tin dichloride solution, the tin dioxide solution forms a tin oxide coating layer on the surface of manganese carbonate, bismuth trioxide, and other particles through chemical deposition. This can suppress the segregation of metal ions during sintering, form a low-viscosity liquid phase during calcination to drive particle rearrangement, fill pores, and promote densification, ultimately significantly reducing porosity.

[0010] Optionally, the calcination process in step S4 is specifically performed as follows: Decomposition and synthesis: Starting from room temperature, first raise the temperature to 150±10℃ at a rate of 15-20℃ / h, hold for 30-40 min, then raise the temperature to 330-360℃ at a rate of 22-30℃ / h, hold for 2-4 h, and then raise the temperature to 650-850℃ at a rate of 32-40℃ / h, hold for 20-22 h. Preheating: Then raise the temperature to 850-950℃ at a rate of 15-25℃ / h and hold for 3-10 hours; Calcination: Finally, calcine at 1000-1200℃ for 2-4 hours, and then cool to room temperature at a rate of 10-20℃ / h.

[0011] By adopting the above technical solution, another factor affecting the porosity of the resistance sheet is sintering. During the sintering process, an excessively rapid heating rate will cause the moisture and organic additives in the powder to evaporate and decompose rapidly. The gas cannot escape in time, forming pores inside the green body. At the same time, rapid temperature changes can also cause thermal stress inside the green body, inducing microcracks, which may also become the origin of pores.

[0012] Therefore, the calcination process in this application adopts a segmented process. First, in the decomposition and synthesis section, the moisture in the powder is slowly evaporated at 150±10℃. Then, some organic additives begin to decompose at 850-950℃. Finally, the organic additives are fully oxidized, decomposed, and eliminated at 650-850℃. By slowly raising the temperature, the physicochemical reaction at the decomposition and synthesis temperature proceeds steadily, which is conducive to the full discharge of organic additives and moisture and avoids the formation of pores and cracks caused by rapid expansion of gas inside the powder due to excessive heating.

[0013] The temperature is then raised to the pre-sintering temperature, during which the resistance sheet powder undergoes further physicochemical changes, preparing it for subsequent high-temperature sintering. Finally, high-temperature sintering is performed to achieve the final densification and performance stabilization of the resistance sheet. Controlling the heating rate during the transition from the decomposition and synthesis stage to the pre-sintering stage prevents the powder from developing hidden defects due to rapid temperature changes, ensuring the integrity of the powder structure and reducing microcracks and porosity caused by thermal stress. Finally, slow cooling reduces internal stress caused by rapid temperature changes in the calcined body, preventing microcracks caused by internal stress, ensuring the quality of the resistance sheet, and further reducing porosity.

[0014] Finally, this application effectively solves the problem of high porosity in traditional processes by comprehensively addressing multiple aspects, including optimizing the heating rate of the decomposition and synthesis stage, precisely controlling the heating rate from the decomposition and synthesis stage to the pre-calcination stage, rationally setting the parameters of the pre-calcination stage, special treatment of additives, and fine powder pretreatment. This significantly improves the density and performance of metal oxide resistor sheets, reduces product defect rates, and increases production efficiency. Furthermore, through the control of powder processing and calcination processes described in this application, the generation of internal pores and microcracks in the resistor sheets is reduced, increasing the density of the resistor sheets and thus improving their electrical performance and reliability. Optimizing the decomposition and synthesis and pre-calcination processes increases the yield of resistor sheets and reduces production costs. Improving the microstructure of the resistor sheets reduces porosity and enhances their current-carrying capacity, meeting the requirements of higher-demand electrical applications. Controlling the distribution of additives at grain boundaries improves the stability and consistency of resistance performance.

[0015] Optionally, in step S2, the drying temperature is 60-150℃, the drying time is 3-5h, and the heating rate to 600-800℃ is 5-10℃ / h.

[0016] By adopting the above technical solutions and through the above fine processing, the purity and uniformity of the powder are further improved, laying the foundation for the preparation of high-quality, low-porosity resistor sheets.

[0017] Optionally, the metal oxide resistive sheet in step S1 comprises the following parts by weight of raw materials: 30-40 parts bismuth trioxide, 15-23 parts antimony trioxide, 30-35 parts cobalt tetroxide, 38-45 parts manganese dioxide, 10-15 parts chromium trioxide, 18-25 parts nickel oxide, 2-4 parts aluminum nitrate, 0.03-0.05 parts silver nitrate, 22-26 parts manganese carbonate, and 800-850 parts zinc oxide.

[0018] Optionally, the metal oxide resistive sheet in step S1 comprises the following parts by weight of raw materials: 35 parts bismuth trioxide, 18 parts antimony trioxide, 33 parts cobalt tetroxide, 42 parts manganese dioxide, 12.8 parts chromium trioxide, 21.5 parts nickel oxide, 3 parts aluminum nitrate, 0.04 parts silver nitrate, 24 parts manganese carbonate, and 820 parts zinc oxide.

[0019] Optionally, the specific operation of obtaining the slurry in step S1 is as follows: zinc oxide is dispersed in water, and then antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate and silver nitrate are added. After mixing, a slurry with a solid content of 60-65 wt% is obtained. Then, a surface modifier is added, and the amount of surface modifier added is 2-2.5 wt% of the solid particles in the slurry.

[0020] The surface modifier comprises the following raw materials in parts by weight: 3-5 parts polyacrylic acid dispersant, 1.8-2.5 parts silane coupling agent, and 2-4 parts polyvinylpyrrolidone.

[0021] By adopting the above technical solutions, the polyacrylic acid dispersant in the surface modifier, through electrostatic stabilization and steric hindrance effects, ensures that oxide particles such as zinc oxide are uniformly dispersed in the slurry, reducing particle agglomeration. The uniform particle dispersion and close contact between particles during sintering contribute to the formation of a dense structure and reduce the porosity of the resistor sheet. The addition of the silane coupling agent, through hydrolysis and condensation in the slurry, forms Si-O-Zn / Bi / Sb covalent bridges with the metal oxide particles, constructing a three-dimensional network framework. This three-dimensional framework restricts particle migration during pre-firing and subsequent sintering through physical confinement and chemical bonding, preventing excessive particle coarsening. The formation of uniform particles during the pre-firing stage facilitates particle contact during sintering, reducing pore formation. Furthermore, the silane coupling agent helps improve the interfacial bonding between inorganic particles and the surface modifier, further reducing pore formation and porosity during sintering.

[0022] In polyvinylpyrrolidone (PVP), the pyrrolidone ring adsorbs onto the surface of metal oxide particles to form a protective layer, reducing particle collisions and agglomeration. At the same time, the long chain structure of PVP extends into the aqueous phase, forming a three-dimensional barrier to prevent particle agglomeration and achieve nanoscale uniform dispersion, which helps to achieve uniform distribution during subsequent sintering.

[0023] Optionally, the surface modifier may further include 0.5-1 parts of nano-zirconia sol.

[0024] By adopting the above technical solution, the nano-zirconia sol acts as a heterogeneous nucleation site during the pre-sintering stage, adsorbing onto the surface of zinc oxide particles, inducing local lattice distortion, reducing the activation energy of zinc oxide grain growth, and reducing porosity caused by particle migration in the early stage of sintering. Moreover, in the subsequent sintering stage, the nano-zirconia forms a cubic fluorite phase with bismuth trioxide, filling the grain boundary pores between zinc oxide grains, reducing porosity. Finally, the addition of nano-zirconia sol reduces the porosity of the resistor sheet, reduces the leakage current path in the resistor sheet, and improves the nonlinear coefficient and varistor voltage while enhancing its mechanical strength.

[0025] Furthermore, in this application, the main materials such as zinc oxide are mixed with surface modifiers and then pre-calcined before being mixed and stirred with substances such as bismuth oxide and sintered. The pre-calcination treatment can decompose the organic components in the surfactant, reducing the probability of increased porosity due to the volatilization of organic matter during subsequent calcination. At the same time, the residual effect of nano-zirconia in the surface modifier can inhibit grain boundary migration. Moreover, antimony dioxide and bismuth trioxide react with zinc oxide in the solid phase during the pre-calcination stage to generate spinel phase, providing reactive sites for subsequent calcination. Ultimately, the synergistic effect of pre-calcination treatment and surface modifier in this application can optimize powder dispersibility and reduce subsequent sintering defects through pre-reaction and grain control.

[0026] Optionally, in step S3, the mass concentration of the tin dichloride solution is 5-10%, and the amount of tin dichloride added is 1.5-3 wt% of the additive mixture; In step S4, the mass ratio of the mixture to be deposited to the binder and anhydrous ethanol is (4-6):(1-1.2):1.

[0027] Secondly, this application provides a metal oxide resistor chip, which adopts the following technical solution: A metal oxide resistor is prepared by the aforementioned process.

[0028] By adopting the above technical solutions, the preparation process provided in this application finally produces a resistor sheet, which reduces the generation of pores and microcracks inside the resistor sheet, improves the density of the resistor sheet, and thus enhances its electrical performance and reliability; optimizes the decomposition synthesis and pre-firing process, improves the yield of the resistor sheet, and reduces production costs; improves the microstructure of the resistor sheet, reduces porosity, enhances its current carrying capacity, meets higher requirements for electrical application scenarios, and improves the stability and consistency of resistance performance by controlling the distribution of additives at grain boundaries.

[0029] In summary, this application has the following beneficial effects: 1. This application effectively solves the problem of high porosity in traditional processes by comprehensively addressing multiple aspects, including optimizing the heating rate of the decomposition and synthesis section, precisely controlling the heating rate from the decomposition and synthesis section to the pre-calcination section, rationally setting the parameters of the pre-calcination section, special treatment of additives, and fine powder pretreatment. Ultimately, this significantly improves the density and performance of metal oxide resistor sheets, reduces product defect rates, and increases production efficiency. 2. The powder processing and calcination process control in this application reduce the generation of pores and microcracks inside the resistor sheet, improve the density of the resistor sheet, thereby improving its electrical performance and reliability; optimize the decomposition synthesis and pre-calcination process to improve the yield of the resistor sheet and reduce production costs; improve the microstructure of the resistor sheet, reduce porosity, enhance its current carrying capacity, meet the higher requirements of electrical application scenarios; and improve the stability and consistency of resistance performance by controlling the distribution of additives at grain boundaries. 3. In this application, zinc oxide and other main materials are mixed with surface modifiers and then pre-calcined before being mixed and stirred with bismuth oxide and other substances for sintering. The pre-calcination treatment can decompose the organic components in the surfactant, reducing the probability of increased porosity due to the volatilization of organic matter during subsequent calcination. At the same time, the residual effect of nano-zirconia in the surface modifier can inhibit grain boundary migration. Moreover, antimony dioxide and bismuth trioxide react with zinc oxide in the solid phase during the pre-calcination stage to generate spinel phase, providing reactive sites for subsequent calcination. Finally, the synergistic effect of pre-calcination treatment and surface modifier in this application can optimize powder dispersibility and reduce subsequent sintering defects through pre-reaction and grain control. Detailed Implementation

[0030] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0031] In the following examples, the surface modifier polyacrylic acid dispersant used is an anionic polyacrylic acid dispersant, specifically Dispex® AA 4040 ammonium polyacrylic acid dispersant; The nano-zirconia sol was selected from Huzhou Mister New Materials Co., Ltd., and the model is MST-GRJ20 with an effective ingredient content of 20%.

[0032] Example 1

[0033] A fabrication process for a metal oxide resistor includes the following steps: S1. Prepare materials: 30g bismuth trioxide, 15g antimony trioxide, 30g cobalt tetroxide, 38g manganese dioxide, 10g chromium trioxide, 18g nickel oxide, 2g aluminum nitrate, 0.03g silver nitrate, 22g manganese carbonate, and 800g zinc oxide as raw materials for metal oxide resistors. Zinc oxide was dispersed in water, and then antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate and silver nitrate were added and mixed to obtain a slurry with a solid content of 60 wt%. Then, a surface modifier was added and mixed to obtain a mixed slurry. The surface modifier is prepared by mixing the following raw materials: 3g polyacrylic acid dispersant, 1.8g silane coupling agent KH-550, 2g polyvinylpyrrolidone and 0.5g nano-zirconia sol; S2. The mixed slurry obtained in step S1 is dried at 60°C for 5 hours to obtain a pre-made powder. Then, the pre-made powder is placed in a calcining furnace and heated to 600°C at a heating rate of 5°C / h. It is then held at 600°C for 3 hours for pre-calcination treatment to obtain a pre-calcined mixture. The pre-calcined mixture is then ground and dried at 60°C for 2 hours to obtain an additive composite powder. S3. Manganese carbonate, bismuth trioxide, nickel oxide, and cobalt tetroxide are mixed to form an additive mixture. A 5% (w / w) tin dichloride solution is added to the additive mixture, and the mixture is stirred to obtain the deposition solution. The amount of tin dichloride added is 1.5 wt% of the additive mixture. S4. Mix the mixture to be deposited in step S3 with the binder polyvinyl alcohol and anhydrous ethanol in a mass ratio of 4:1:1, then add the additive composite powder obtained in step S2, mix, stir at 60°C for 3 hours to allow it to mix and react, then dry at 60°C for 3 hours and press to form a resistor sheet blank. The resistor blank is calcined. The calcination process is carried out in stages using a pusher-plate calcination furnace. The specific operation includes the following steps: Decomposition and synthesis: Starting from room temperature, the temperature is first increased to 140℃ at a rate of 15℃ / h and held for 40 min. Then, the temperature is increased to 330℃ at a rate of 22℃ / h and held for 4 h. Finally, the temperature is increased to 650℃ at a rate of 32℃ / h and held for 22 h. Preheating: Then raise the temperature to 850℃ at a rate of 15℃ / h and hold for 10h; Calcination: Finally, the temperature is increased to 1000℃ at a heating rate of 5℃ / h and calcined at this temperature for 4h, and then cooled to room temperature at a rate of 10℃ / h. S5. Post-processing: The specific operation is as follows: After grinding the calcined blank, aluminum electrodes are coated on the upper and lower end faces. Glass glaze is sprayed on the side and then heat-treated at 520℃ for 2 hours to achieve glass glaze sintering, thus obtaining metal oxide resistor sheet.

[0034] Example 2

[0035] A fabrication process for a metal oxide resistor includes the following steps: S1. Prepare materials: 35g bismuth trioxide, 18g antimony trioxide, 33g cobalt tetroxide, 42g manganese dioxide, 12.8g chromium trioxide, 21.5g nickel oxide, 3g aluminum nitrate, 0.04g silver nitrate, 24g manganese carbonate, and 820g zinc oxide as raw materials for metal oxide resistor sheets. Zinc oxide was dispersed in water, and then antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate and silver nitrate were added and mixed to obtain a slurry with a solid content of 62 wt%. Then, a surface modifier was added and mixed to obtain a mixed slurry. The surface modifier is prepared by mixing the following raw materials: 4g polyacrylic acid dispersant, 2g silane coupling agent KH-550, 3g polyvinylpyrrolidone and 0.8g nano-zirconia sol; S2. The mixed slurry obtained in step S1 is dried at 80°C for 4 hours to obtain a pre-made powder. Then, the pre-made powder is placed in a calcining furnace and heated to 700°C at a heating rate of 6°C / h. It is then held at 700°C for 2.5 hours for pre-calcination treatment to obtain a pre-calcined mixture. The pre-calcined mixture is then ground and dried at 80°C for 2 hours to obtain an additive composite powder. S3. Manganese carbonate, bismuth trioxide, nickel oxide, and cobalt tetroxide are mixed to form an additive mixture. An 8% (w / w) tin dichloride solution is added to the additive mixture, and the mixture is stirred to obtain the deposition solution. The amount of tin dichloride added is 2.2 wt% of the additive mixture. S4. Mix the mixture to be deposited in step S3 with the binder and anhydrous ethanol in a mass ratio of 5:1.1:1, then add the additive composite powder prepared in step S2, mix, stir at 60°C for 3 hours to allow it to mix and react, then dry at 60°C for 3 hours and press to form a resistor sheet blank. The resistor blank is calcined. The calcination process is carried out in stages using a pusher-plate calcination furnace. The specific operation includes the following steps: Decomposition and synthesis: Starting from room temperature, the temperature is first increased to 150℃ at a rate of 15℃ / h and held for 35 min. Then, the temperature is increased to 350℃ at a rate of 25℃ / h and held for 3 h. Finally, the temperature is increased to 700℃ at a rate of 35℃ / h and held for 21 h. Preheating: Then raise the temperature to 900℃ at a rate of 20℃ / h and hold for 6 hours; Calcination: Finally, the temperature is increased to 1100℃ at a heating rate of 8℃ / h and calcined at this temperature for 3h, and then cooled to room temperature at a rate of 15℃ / h. S5. Post-processing: The specific operation is as follows: After grinding the calcined blank, aluminum electrodes are coated on the upper and lower end faces. Glass glaze is sprayed on the side and then heat-treated at 520℃ for 2 hours to achieve glass glaze sintering, thus obtaining metal oxide resistor sheet.

[0036] Example 3

[0037] A fabrication process for a metal oxide resistor includes the following steps: S1. Prepare materials: 40g bismuth trioxide, 23g antimony trioxide, 35g cobalt tetroxide, 45g manganese dioxide, 15g chromium trioxide, 25g nickel oxide, 4g aluminum nitrate, 0.05g silver nitrate, 26g manganese carbonate, and 850g zinc oxide as raw materials for metal oxide resistors. Zinc oxide was dispersed in water, and then antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate and silver nitrate were added and mixed to obtain a slurry with a solid content of 65 wt%. Then, a surface modifier was added and mixed to obtain a mixed slurry. The surface modifier is prepared by mixing the following raw materials: 5g polyacrylic acid dispersant, 2.5g silane coupling agent KH-550, 4g polyvinylpyrrolidone and 1g nano zirconia sol; S2. The mixed slurry obtained in step S1 is dried at 150°C for 3 hours to obtain a pre-made powder. Then, the pre-made powder is placed in a calcining furnace and heated to 800°C at a heating rate of 10°C / h. It is then held at 800°C for 2 hours for pre-calcination treatment to obtain a pre-calcined mixture. The pre-calcined mixture is then ground and dried at 150°C for 2 hours to obtain an additive composite powder. S3. Manganese carbonate, bismuth trioxide, nickel oxide, and cobalt tetroxide are mixed to form an additive mixture. A 10% tin dichloride solution is added to the additive mixture, and the mixture is stirred to obtain the deposition solution. The amount of tin dichloride added is 3 wt% of the additive mixture. S4. Mix the mixture to be deposited in step S3 with the binder and anhydrous ethanol in a mass ratio of 6:1.2:1, then add the additive composite powder obtained in step S2, mix, stir at 60°C for 3 hours to allow it to mix and react, then dry at 60°C for 3 hours and press to form a resistor sheet blank. The resistor blank is calcined. The calcination process is carried out in stages using a pusher-plate calcination furnace. The specific operation includes the following steps: Decomposition and synthesis: Starting from room temperature, first raise the temperature to 160℃ at a rate of 20℃ / h, hold for 30 min, then raise the temperature to 360℃ at a rate of 30℃ / h, hold for 2 h, and then raise the temperature to 850℃ at a rate of 40℃ / h, hold for 20 h. Preheating: Then raise the temperature to 950℃ at a rate of 25℃ / h and hold for 3 hours; Calcination: Finally, the temperature is increased to 1200℃ at a heating rate of 10℃ / h and calcined at this temperature for 2h, and then cooled to room temperature at a rate of 20℃ / h. S5. Post-processing: The specific operation is as follows: After grinding the calcined blank, aluminum electrodes are coated on the upper and lower end faces. Glass glaze is sprayed on the side and then heat-treated at 520℃ for 2 hours to achieve glass glaze sintering, thus obtaining metal oxide resistor sheet.

[0038] Example 4

[0039] A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that the specific operation of calcination in step S4 is as follows: the temperature is increased to 300°C at a rate of 2°C / min, held for 2 hours, then increased to 850°C at a rate of 1°C / min, held for 6 hours, and finally increased to 1100°C at a rate of 5°C / h and calcined at this temperature for 3 hours, and then cooled to room temperature at a rate of 10°C / h.

[0040] Example 5

[0041] A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that nano-zirconia sol is not added to the surface modifier.

[0042] Example 6

[0043] A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that polyvinylpyrrolidone is not added to the surface modifier.

[0044] Comparative Example 1 A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that in step S1, manganese dioxide is added along with manganese carbonate, bismuth trioxide, nickel oxide and cobalt tetroxide, and then step S2 is performed. In step S3, the corresponding mixture to be deposited is replaced with tin dichloride solution, and in step S4, the corresponding mixture to be deposited is replaced with tin dichloride solution.

[0045] Comparative Example 2 A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that step S2 is not performed, and the additive composite powder in step S4 is directly replaced by the mixed slurry obtained in step S1, which is dried, pressed into shape, and then calcined.

[0046] Comparative Example 3 A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that the tin dichloride solution in step S3 is replaced with tin oxide, and the amount of tin oxide added is 2.2 wt% of the additive mixture. Manganese carbonate, bismuth trioxide, nickel oxide, cobalt tetroxide and tin oxide are mixed to obtain a solid mixture, and then step S4 is carried out. In step S4, the mass ratio of the solid mixture to the binder and anhydrous ethanol is 10:1:1.

[0047] Comparative Example 4 A process for preparing a metal oxide resistor sheet is carried out according to the method in Example 2, except that tin dichloride solution is not added in step S3, and the mass ratio of binder to anhydrous ethanol in step S4 is 1:1, and the amount of binder added is 5 wt% of the amount of additive mixture added.

[0048] Performance testing The porosity of the metal oxide resistors prepared in the above embodiments was measured using the Archimedes method, which involves immersing the resistor in water and measuring the volume of liquid displaced. The porosity was calculated as: (1 - (m1 - m2 / (ρ))) 水 ×V 样品 )))×100%, where m1 is the mass of the sample dried to constant weight in air, m2 is the mass of the sample submerged in water, and ρ 水 V is the density of water. 样品 The apparent volume V of the sample is measured by the water displacement method. The specific method is as follows: the resistor sample is dried to constant weight, and its mass in air (m1) is recorded. The sample is then completely immersed in water, and its mass after immersion (m2) is recorded. The apparent volume V of the sample is then measured using the water displacement method. 样品 Calculate the porosity according to the above formula.

[0049] In addition, the nonlinear coefficient α, 2ms square wave current carrying test (specifically the residual voltage ratio and the residual voltage change rate after 10 impacts, the residual voltage ratio being the ratio of the residual voltage after the 2ms square wave current carrying impact to the initial varistor voltage), leakage current (DC500V), and Kct value of AC accelerated aging at 115℃ were tested for the resistor. The test results are shown in Table 1 below.

[0050] The nonlinear coefficient α is applied in increments of 10V to 1000V DC voltage, and the current value at the corresponding voltage is measured. The calculation is based on the slope change of the volt-ampere characteristic curve. 2ms square wave current capacity The Kct value of AC accelerated aging at 115℃ was calculated by applying a 50Hz sinusoidal voltage at 115℃ for 100 hours, and measuring the rate of change of resistance and the increase in leakage current after aging. Kct value = (resistance value after aging / initial resistance value) / (leakage current after aging / initial leakage current)).

[0051] Table 1:

[0052] Continued from Table 1:

[0053] Based on the test results in Table 1 above, the metal oxide resistor sheets prepared in Examples 1-3 of this application through the combined action of calcination and surface modifier have low porosity, and their electrical properties such as current carrying capacity are also significantly improved. In addition, the yield of resistor sheets prepared by the process provided in Example 1 of this application is 95-98%, while the yield of resistor sheets prepared by the methods in Comparative Examples 1 and 2 is 80-84%.

[0054] Combining the test results of Examples 1 and 4, in Example 4, the porosity increased while the electrical properties decreased after the decomposition and synthesis stage was directly heated to 300°C and then heated to the pre-calcination temperature, compared to Example 1. Combining the test results of Examples 5 and 6, the porosity increased when no nano-zirconia sol or polyvinylpyrrolidone was added to the surface modifier, especially in Example 5 when no nano-zirconia sol was added, the performance decreased. The addition of the surface modifier significantly reduced the porosity compared to the traditional addition of polyacrylic acid dispersant.

[0055] Combining the test results of Example 1 with those of Comparative Examples 1 and 2, in Comparative Example 1, manganese carbonate and other oxides such as zinc oxide were directly added, pre-calcined, and then the slurry was prepared and calcined. This significantly increased the porosity while reducing the electrical properties. In Comparative Example 2, the raw materials were added directly without pre-calcination, resulting in increased porosity and reduced electrical properties. In this application, the improved raw material addition method yielded a resistor sheet with even lower porosity and improved electrical properties. Furthermore, combining the test results of Comparative Examples 3 and 4, the porosity increased and the electrical properties decreased when tin dichloride solution was not added or when tin oxide was added directly.

[0056] 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 process for fabricating a metal oxide resistor, characterized in that, Includes the following steps: S1. Material preparation: Prepare materials containing at least zinc oxide, antimony trioxide, bismuth trioxide, cobalt tetroxide, chromium trioxide, manganese dioxide, nickel oxide, manganese carbonate, aluminum nitrate, and silver nitrate as raw materials for metal oxide resistors. A slurry was prepared by mixing zinc oxide, antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate, and silver nitrate. A surface modifier was added to the slurry, and the mixture was then prepared to obtain a mixed slurry. S2. After drying the mixed slurry obtained in step S1, a pre-formed powder is obtained. Then, the pre-formed powder is pre-calcined at 600-800℃ for 2-3 hours to obtain a pre-calcined mixture. After grinding and drying, an additive composite powder is obtained. S3. Manganese carbonate, bismuth trioxide, nickel oxide and cobalt tetroxide are mixed together as an additive mixture. Tin dichloride solution is added to the additive mixture and stirred to obtain the mixture to be deposited. S4. The mixture to be deposited is mixed with binder, anhydrous ethanol and additive composite powder, dried, pressed into shape and then calcined. S5. Post-processing to obtain metal oxide resistor sheets.

2. The fabrication process of a metal oxide resistor sheet according to claim 1, characterized in that: The specific operation of the calcination treatment in step S4 is as follows: Decomposition and synthesis: Starting from room temperature, first raise the temperature to 150±10℃ at a rate of 15-20℃ / h, hold for 30-40 min, then raise the temperature to 330-360℃ at a rate of 22-30℃ / h, hold for 2-4 h, and then raise the temperature to 650-850℃ at a rate of 32-40℃ / h, hold for 20-22 h. Preheating: Then raise the temperature to 850-950℃ at a rate of 15-25℃ / h and hold for 3-10 hours; Calcination: Finally, calcine at 1000-1200℃ for 2-4 hours, and then cool to room temperature at a rate of 10-20℃ / h.

3. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: In step S2, the drying temperature of the mixed slurry is 60-150℃, the drying time is 3-5h, and the heating rate to 600-800℃ is 5-10℃ / h.

4. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: The metal oxide resistor sheet in step S1 comprises the following parts by weight of raw materials: 30-40 parts bismuth trioxide, 15-23 parts antimony trioxide, 30-35 parts cobalt tetroxide, 38-45 parts manganese dioxide, 10-15 parts chromium trioxide, 18-25 parts nickel oxide, 2-4 parts aluminum nitrate, 0.03-0.05 parts silver nitrate, 22-26 parts manganese carbonate, and 800-850 parts zinc oxide.

5. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: The specific operation of preparing the slurry in step S1 is as follows: zinc oxide is dispersed in water, and then antimony trioxide, chromium trioxide, manganese dioxide, aluminum nitrate and silver nitrate are added. After mixing, a slurry with a solid content of 60-65 wt% is prepared. Then, a surface modifier is added, and the amount of surface modifier added is 2-2.5 wt% of the solid particles in the slurry.

6. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: The surface modifier comprises the following raw materials in parts by weight: 3-5 parts polyacrylic acid dispersant, 1.8-2.5 parts silane coupling agent, and 2-4 parts polyvinylpyrrolidone.

7. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: The surface modifier also includes 0.5-1 parts of nano-zirconia sol.

8. The fabrication process of a metal oxide resistor according to claim 1, characterized in that: In step S3, the mass concentration of the tin dichloride solution is 5-10%, and the amount of tin dichloride added is 1.5-3 wt% of the additive mixture. In step S4, the mass ratio of the mixture to be deposited to the binder and anhydrous ethanol is (4-6):(1-1.2):

1.

9. A metal oxide resistor sheet prepared by the preparation process described in any one of claims 1-8.

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