Preparation method of high-performance zinc oxide resistor disc

Abstract

The invention relates to the technical field of lightning arresters, and discloses a preparation method of a high-performance zinc oxide resistor disc, which comprises the following steps: firstly preparing an Al-ZnO composite material and a BiSbO4 composite material, further dispersing Al-ZnO into water, further adding the BiSbO4 composite material, NiO, Co3O4, Mn3O4, Cr2O3 and anhydrous silicic acid, uniformly stirring, and finally, preparing the high-performance zinc oxide resistor disc. Further adding a dispersing agent, a defoaming agent and a dissolved adhesive, uniformly stirring to obtain a suspension liquid, then preparing the suspension liquid into particles with relatively uniform particle sizes through a spray granulator, and finally, sequentially carrying out tabletting, degumming and pre-sintering, sintering, grinding, heat treatment, aluminum electrode spraying and glazing to obtain the resistor disc. Through the ZnO material doped with Al, Al can enter ZnO crystal grains more easily, the crystal grain resistance of the ZnO crystal grains is reduced, the residual voltage ratio of the resistor disc is reduced, the protection level of the resistor disc is remarkably improved, BiSbO4 prepared through the coprecipitation method replaces traditional bismuth oxide and antimony oxide, the uniformity of the microstructure of the resistor disc can be remarkably improved, and the through-current capacity of the resistor disc is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning arresters, and particularly to a preparation method of high-performance zinc oxide resistor chips. Background Art

[0002] With the development of the economy and the continuous progress of society, more and more electrical equipment and electronic products have entered human life. "Electricity" has become an inseparable part of human life. At the same time, people's requirements for the safety of the power consumption system are also getting higher and higher. When the power system is operating, lightning arresters are usually installed to protect electrical equipment from system overvoltage and lightning strikes, thereby improving the stability and reliability of the power system operation.

[0003] As the core component of the lightning arrester, zinc oxide (ZnO) varistor ceramics are mainly formed by solid-state sintering of a mixture of ZnO powder and various metal oxide additives. Its various electrical properties will directly determine the electrical properties of the lightning arrester. The residual voltage ratio of the ZnO resistor chip determines the protection level of the lightning arrester. The lower the residual voltage ratio, the higher the protection level of the lightning arrester. A larger residual voltage ratio means that the lightning arrester cannot limit the overvoltage to a sufficiently low level after the overvoltage occurs, resulting in damage to the electrical equipment. The current-carrying capacity of the ZnO resistor chip will determine the number of lightning strikes that the lightning arrester can withstand, directly determining the service life of the lightning arrester during operation. If the lightning arrester is damaged, it will cause it to fail to play its protection role normally, making the electrical equipment lose protection and easily suffer damage from overvoltages such as lightning strikes, and is very likely to cause large-scale power outages, bringing great inconvenience to production and life. Therefore, improving the protection level and service life of the lightning arrester is of great significance to the power system. For this reason, a preparation method of high-performance zinc oxide resistor chips is proposed to make the residual voltage ratio of the zinc oxide resistor chips lower and the current-carrying capacity stronger. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the deficiencies of the prior art, the present invention provides a preparation method of high-performance zinc oxide resistor chips, which has the advantages of being able to make the residual voltage ratio of the zinc oxide resistor chips lower and the current-carrying capacity stronger.

[0006] (II) Technical Solutions

[0007] To achieve the above object of making the residual voltage ratio of the zinc oxide resistor chips lower and the current-carrying capacity stronger, the present invention provides the following technical solutions: A preparation method of high-performance zinc oxide resistor chips, comprising the following steps:

[0008] Step 1: Prepare an Al-ZnO composite material, where Al-ZnO is ZnO doped with Al;

[0009] Step 2: Prepare a BiSbO4 composite material;

[0010] Step 3: Disperse Al-ZnO in water, first add BiSbO4 composite material, NiO, Co3O4, Mn3O4, Cr2O3 and anhydrous silicic acid and stir evenly, then add dispersant, defoamer and dissolved binder and stir evenly to obtain a suspension;

[0011] Step 4: Make the suspension into particles with relatively uniform particle size through a spray granulator, and then successively go through tabletting, debinding pre-sintering, sintering, grinding, heat treatment, spraying aluminum electrodes and glazing to obtain a resistor chip.

[0012] Preferably, the Al-ZnO in Step 1 is prepared by the following method: Prepare an Al(NO3)3·9H2O solution with a molar concentration of 0.01%, then disperse ZnO in the Al(NO3)3·9H2O solution and soak it, perform ball milling for 100 - 120 min to obtain a mixture, then precipitate and bake the mixture. First, calcine it at 200 - 250°C for 20 - 30 min, then raise the temperature to 600 - 1000°C and calcine it at this temperature for 1 - 3 h, and then naturally cool it to room temperature to enable Al atoms to fully diffuse into the ZnO lattice, complete the doping process, and obtain the Al-ZnO composite material.

[0013] Preferably, the BiSbO4 composite material in Step 2 is prepared by the following method: Add Bi(NO3)3 and Sb(NO3)3 to the urea solution, further place the solution on a magnetic stirrer and stir, while performing water bath heating. Heat the water bath to 90 - 95°C and keep it warm for 100 - 120 min to obtain a mixed precipitate precursor. Further perform centrifugation on the obtained mixed precipitate precursor to separate the solid part. After centrifugation, take out the solid and perform drying treatment to remove the water in it. Transfer the dried precursor to a muffle furnace. First, heat it at a heating rate of 2.55°C / min to 550°C, keep it at this temperature for 80 minutes, then continue to heat it at a heating rate of 1°C / min to 650 - 750°C, and calcine it in the temperature range of 650 - 750°C for 40 - 60 minutes. After the reaction, obtain a solid product. Further perform wet ball milling on the calcined solid to further refine the solid particles. After the ball milling is completed, dry the material at a temperature of 90 - 100°C to finally obtain the BiSbO4 composite material.

[0014] Preferably, the operation steps of Step 3 are as follows: First, prepare an appropriate amount of Al-ZnO material and slowly pour it into pure water. During the pouring process, gently stir to initially disperse Al-ZnO in the water. Due to the characteristics of Al-ZnO itself, agglomeration may occur in water, so a dispersant is added subsequently to improve the dispersion effect. Then, add the BiSbO4 composite material. BiSbO4 has a unique structure and properties and is expected to play a synergistic role after being mixed and dispersed with Al-ZnO. When adding it, also add it slowly and continuously stir to ensure that it can be evenly distributed in the water containing Al-ZnO. Subsequently, add NiO, Co3O4, Mn3O4, and Cr2O3 in sequence. These transition metal oxides each have different catalytic activities and physical and chemical properties, which can further enrich the performance of the system. Each time an oxide is added, stir well for a period of time to allow it to fully contact and mix with other components in the system. Then, add anhydrous silicic acid. Anhydrous silicic acid has a large specific surface area and can adsorb on the surface of other materials, playing a certain auxiliary role in the stability and dispersion of the system. After adding it, through strong stirring, make it evenly dispersed in the entire mixed solution.

[0015] At this time, a large number of bubbles may be generated in the mixed solution, which will affect the uniformity of the system and subsequent operations. Therefore, add an appropriate amount of defoamer. The defoamer can quickly reduce the surface tension of the bubbles, causing the bubbles to burst and disappear, ensuring good fluidity of the mixed solution. Then, add the dissolved binder. The binder can firmly bind various particulate matters in the system, enhancing the integrity and stability of the material. During the addition of the binder, continuously stir to allow the binder to evenly coat the surface of each material particle. Finally, add the dispersant again. The dispersant can prevent the agglomeration of material particles through electrostatic repulsion or steric hindrance, etc., enabling the Al-ZnO, BiSbO4 composite material, and other metal oxides to be evenly and stably dispersed in water, forming a dispersion system with excellent performance.

[0016] Preferably, the operation steps of Step 4 are as follows: First, use a spray granulation device to spray the uniformly mixed material suspension obtained in Step 3 into a hot air stream in the form of droplets, so that the droplets quickly evaporate water to form particles with relatively uniform particle sizes. Further, place the particles obtained by spray granulation into a tablet press mold, apply a certain pressure for tableting to make the particles tightly combine to form a resistor blank with a certain shape and strength. Further, put the pressed resistor blank into a high-temperature furnace for debinding and pre-sintering to fully decompose and discharge the organic components such as adhesives in the blank. Subsequently, perform pre-sintering treatment to initially improve the strength and stability of the blank. The blank that has completed debinding and pre-sintering is further sintered at a high temperature. During the sintering process, a series of physical and chemical reactions occur inside the material, the grains grow and densify, thereby obtaining the required material properties. Further, use a grinding device to grind the sintered sample, remove the uneven parts on the surface of the sample and perform fine grinding to make the surface of the sample reach the required flatness and smoothness to meet the requirements of subsequent processes. Further, put the ground sample into a high-temperature furnace again for heat treatment to optimize the microstructure and properties of the material, eliminate internal stress, and improve the stability of the material. Further, use a vacuum sputtering or spraying device to evenly spray aluminum electrodes on the surface of the heat-treated sample. After spraying, it is necessary to detect the adhesion and conductivity of the electrodes. Finally, adopt a suitable glazing process, such as dip coating, spraying, etc., to evenly apply a layer of glaze on the surface of the sample, and put the sample with the applied glaze into a low-temperature furnace for heating again to cure the glaze and form a dense protective film on the surface of the sample, improving the corrosion resistance and insulation performance of the sample, etc.

[0017] Compared with the prior art, the present invention provides a preparation method of a high-performance zinc oxide resistor, having the following beneficial effects:

[0018] 1. For the preparation method of the high-performance zinc oxide resistor, through the ZnO material doped with Al, it is more conducive for Al to enter the ZnO grains, reducing the grain resistance thereof, thereby reducing the residual voltage ratio of the resistor and significantly improving the protection level of the resistor.

[0019] 2. For the preparation method of the high-performance zinc oxide resistor, BiSbO4 is obtained by the co-precipitation method. Using BiSbO4 to replace traditional bismuth oxide and antimony oxide can effectively avoid problems such as the increase in the porosity of the resistor caused by the volatilization of bismuth and antimony during high-temperature sintering, significantly improving the density and impact stability of the resistor. Changing the original multi-phase doping to two-phase doping can significantly improve the uniformity of the microstructure of the resistor and improve the current-carrying capacity of the resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the XRD pattern of the Al-ZnO material of the present invention;

[0021] Figure 2XRD pattern of the BiSbO4 material of the present invention;

[0022] Figure 3 SEM pattern of the ZnO resistor of the present invention;

[0023] Figure 4 Grain size distribution diagram of the ZnO resistor of the present invention. Detailed implementation manners

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Embodiment 1:

[0026] Preparation of Al-ZnO composite material: Accurately prepare an Al(NO3)3·9H2O solution with a molar concentration of 0.01%. Weigh a certain amount of ZnO powder accurately and disperse it evenly in the above solution for soaking. Subsequently, use a ball mill to mill the mixture for 100 minutes to ensure that all components are fully mixed. Then, precipitate and bake the mixture. First, calcine it at 200°C for 20 minutes, then slowly raise the temperature to 600°C and calcine it at this temperature for 3 hours, and finally cool it to room temperature naturally to obtain the Al-ZnO composite material.

[0027] Preparation of BiSbO4 composite material: Add Bi(NO3)3 and Sb(NO3)3 to the urea solution in proportion. Place the solution on a magnetic stirrer and heat it in a water bath at 90°C while continuously stirring for 120 minutes to obtain a mixed precipitate precursor. Separate the solid part by centrifugation and take it out for drying. Transfer the dried precursor to a muffle furnace and heat it to 550°C at a heating rate of 2.55°C / min, keep it warm for 80 minutes, then raise the temperature to 650°C at a rate of 1°C / min and calcine it at this temperature for 60 minutes. After the reaction, perform wet ball milling on the solid product, and then dry the material at 90°C to obtain the BiSbO4 composite material.

[0028] Suspension preparation: It is made from raw materials with the following molar percentages: 0 - 3% BiSbO4 composite material, 0.1 - 0.5% NiO, 0.1 - 1.0% Co3O4, 0.1 - 0.3% Mn3O4, 0.1 - 0.3% Cr2O3, 0.1 - 1% anhydrous silicic acid, and the rest is Al-ZnO. Here, Al-ZnO is ZnO doped with Al. Take an appropriate amount. First, slowly pour the Al-ZnO material into pure water, and gently stir it during the pouring process to make it preliminarily dispersed. Since Al-ZnO is prone to agglomeration in water, add an appropriate amount of dispersant to improve the dispersion effect. Then, slowly add the BiSbO4 composite material and continuously stir to ensure its uniform distribution. Add NiO, Co3O4, Mn3O4, and Cr2O3 in sequence, and fully stir each time an oxide is added. Then add anhydrous silicic acid and strongly stir to make it uniformly dispersed. If bubbles are generated in the mixed solution at this time, add an appropriate amount of defoamer. Subsequently, add the dissolved binder and continuously stir to make it uniformly coat each material particle. Finally, add the dispersant again to obtain a suspension with excellent performance.

[0029] Resistor chip preparation: Use a spray granulation device to spray the suspension into a hot air stream in the form of droplets to form particles with uniform particle size. Place the particles in a tablet press mold and apply a certain pressure to press and form, obtaining a resistor chip blank. Put the blank into a high-temperature furnace for debinding and pre-sintering to fully decompose and discharge organic components such as the binder. Then perform pre-sintering to improve the strength and stability of the blank. After that, sinter at a high temperature to cause physical and chemical reactions inside the material, and the grains grow and densify. Use a grinding device to grind the sintered sample to make its surface reach the required flatness and smoothness. Put the ground sample into a high-temperature furnace again for heat treatment to optimize the microstructure and performance and eliminate internal stress. Use a vacuum sputtering device to uniformly spray aluminum electrodes on the surface of the sample, detect the adhesion and conductivity of the electrodes, apply glaze on the surface of the sample using the dip-coating process, and put it into a low-temperature furnace for heating to cure the glaze to form a dense protective film, thus obtaining the resistor chip.

[0030] Example 2:

[0031] Preparation of Al-ZnO composite material: Prepare an Al(NO3)3·9H2O solution with a molar concentration of 0.01%. Disperse ZnO in it and soak it, and ball mill for 110 min. After the mixture precipitates and is baked, calcine at 220°C for 25 min, raise the temperature to 800°C and calcine for 2 h, and then naturally cool to room temperature to obtain the Al-ZnO composite material.

[0032] Preparation of BiSbO4 composite material: Bi(NO3)3 and Sb(NO3)3 were added to the urea solution, magnetically stirred and heated in a water bath to 92 °C, and kept warm for 110 min to obtain the precursor. The solid was separated by centrifugation, dried and then transferred to a muffle furnace. It was heated to 550 °C at a rate of 2.55 °C / min, kept warm for 80 minutes, then heated to 700 °C at a rate of 1 °C / min and calcined for 50 minutes. The solid product was wet ball-milled and dried at 95 °C to obtain the BiSbO4 composite material.

[0033] Preparation of suspension and resistor chip: The steps for preparing the suspension and resistor chip were the same as those in Example 1, and were carried out strictly in accordance with the operation process to ensure the accuracy of the parameters in each link.

[0034] Comparative example

[0035] Preparation of traditional resistor chip (using bismuth oxide and antimony oxide): Without preparing the Al-ZnO composite material and BiSbO4 composite material, traditional ZnO powder was directly mixed with bismuth oxide, antimony oxide, and NiO, Co3O4, Mn3O4, Cr2O3 and anhydrous silicic acid, and a dispersant, defoamer and binder were added and stirred evenly to obtain a suspension.

[0036] Subsequent processes: The subsequent process steps such as spray granulation, tabletting, debinding pre-sintering, sintering, grinding, heat treatment, spraying aluminum electrodes and glazing were the same as those in Example 1, but due to the difference in raw materials, the resistor chip prepared by the traditional process was finally obtained.

[0037] Performance test and analysis

[0038] Residual voltage ratio test: The residual voltage ratios of the resistor chips prepared in Example 1, Example 2 and the comparative example were tested. Using professional electrical performance test equipment, the overvoltage situation in actual operation was simulated, the residual voltage value of the resistor chip at a specified current was measured, and the residual voltage ratio was calculated. The test results showed that the residual voltage ratios of the resistor chips prepared in Example 1 and Example 2 were significantly lower than those of the comparative example, indicating that the ZnO material doped with Al effectively reduced the residual voltage ratio of the resistor chip and improved the protection level.

[0039] Current-carrying capacity test: The current-carrying capacities of the three resistor chips were tested by simulating lightning impulse tests. The changes in the performance of the resistor chips after being subjected to multiple lightning impulses were recorded, including whether there was damage, change in resistance value, etc. The results showed that the current-carrying capacities of the resistor chips prepared in Example 1 and Example 2 were significantly stronger than those of the comparative example, which benefited from the replacement of traditional bismuth oxide and antimony oxide with BiSbO4 composite material, improving the uniformity and density of the microstructure of the resistor chip.

[0040] Microstructure analysis: The microstructures of the three types of resistor chips were observed using a scanning electron microscope (SEM). It can be seen from the SEM images that the grain distributions of the resistor chips prepared in Example 1 and Example 2 are more uniform, and the porosity is significantly reduced. In contrast, the resistor chips of the comparative example have more pores and uneven grain distributions. This further confirms the optimization effect of the preparation method of the present invention on the microstructure of the resistor chips, thereby improving the performance of the resistor chips.

[0041] Through the comparative study of Example 1, Example 2 and the comparative example, for the ZnO material doped with Al, it is more conducive to the entry of Al into the ZnO grains, reducing their grain resistance, thereby reducing the residual voltage ratio of the resistor chip and significantly improving the protection level of the resistor chip. By using the coprecipitation method to obtain BiSbO4 and replacing the traditional bismuth oxide and antimony oxide with BiSbO4, problems such as the increase in the porosity of the resistor chip caused by the volatilization of bismuth and antimony during high-temperature sintering can be effectively avoided, significantly improving the density and impact stability of the resistor chip. Changing the original multi-phase doping to two-phase doping can significantly improve the uniformity of the microstructure of the resistor chip and improve the current-carrying capacity of the resistor chip.

[0042] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance zinc oxide resistor, characterized in that: The following steps are involved: Step 1: Prepare Al-ZnO composite material, where Al-ZnO is ZnO doped with Al; Step 2: Prepare BiSbO4 composite material; Step 3: Disperse Al-ZnO into water, first add BiSbO4 composite material, NiO, Co3O4, Mn3O4, Cr2O3 and anhydrous silicic acid and stir evenly, then add dispersant, defoamer and dissolved binder and stir evenly to obtain a suspension; Step 4: The suspension is made into particles with relatively uniform particle size by a spray granulator, and then the particles are pressed, pre-sintered, sintered, ground, heat treated, sprayed with aluminum electrodes and glazed to obtain a resistor.

2. The method for preparing a high performance zinc oxide resistor according to claim 1, characterized in that: The Al-ZnO in step 1 is prepared by the following method: preparing an Al(NO3)3·9H2O solution with a molar concentration of 0.01%, then dispersing ZnO in the Al(NO3)3·9H2O solution and soaking it, ball milling it for 100-120 minutes to obtain a mixture, then precipitating and baking the mixture, first calcining it at 200-250°C for 20-30 minutes, then heating it to 600-1000°C and calcining it at this temperature for 1-3 hours, and then naturally cooling it to room temperature so that Al atoms can fully diffuse into the ZnO lattice, completing the doping process, and obtaining an Al-ZnO composite material.

3. The method for preparing a high performance zinc oxide resistor according to claim 1, characterized in that: The BiSbO4 composite material of step 2 is prepared by the following method: adding Bi(NO3)3 and Sb(NO3)3 to a urea solution, further placing the solution on a magnetic stirrer for stirring, and heating the solution in a water bath to 90-95°C and keeping the temperature for 100-120 minutes to obtain a mixed precipitate precursor, further centrifuging the obtained mixed precipitate precursor to separate the solid part, taking out the solid after centrifugation for drying to remove the moisture therein, and transferring the dried precursor to a muffle. In the furnace, it is first heated to 550°C at a heating rate of 2.55°C / min, and then kept warm for 80 minutes after reaching this temperature. Then it is further heated to 650-750°C at a heating rate of 1°C / min, and calcined in the temperature range of 650-750°C for 40-60 minutes. After the reaction is completed, a solid product is obtained. The solid obtained after calcination is further wet-milled to further refine the solid particles. After the ball milling is completed, the material is dried at a temperature of 90-100°C to finally obtain a BiSbO4 composite material.

4. The method for preparing a high performance zinc oxide resistor according to claim 1, characterized in that: The operation steps of step three are as follows: first, prepare an appropriate amount of Al-ZnO material and slowly pour it into pure water. During the pouring process, gently stir to make Al-ZnO initially dispersed in the water. Due to the characteristics of Al-ZnO itself, agglomeration may occur in water, and then a dispersant is added to improve the dispersion effect. Then, the BiSbO4 composite material is added. BiSbO4 has a unique structure and performance. After being mixed and dispersed with Al-ZnO, it is expected to play a synergistic role. When adding, it should also be added slowly and stirred continuously to ensure that it can be evenly distributed in the water containing Al-ZnO. Then, NiO, Co3O4, Mn3O4 and Cr2O3 are added in sequence. These transition metal oxides each have different catalytic activities and physical and chemical properties, which can further enrich the performance of the system. Each time an oxide is added, it must be fully stirred for a period of time to allow it to fully contact and mix with other components in the system. Then, anhydrous silicic acid is added. Anhydrous silicic acid has The larger specific surface area can be adsorbed on the surface of other materials, and plays a certain auxiliary role in the stability and dispersibility of the system. After adding, it is evenly dispersed in the entire mixed liquid through strong stirring. At this time, a large number of bubbles may be generated in the mixed liquid, which will affect the uniformity of the system and subsequent operations. Therefore, an appropriate amount of defoaming agent is added. The defoaming agent can quickly reduce the surface tension of the bubbles, make the bubbles burst and disappear, and ensure the good fluidity of the mixed liquid. Then add the dissolved adhesive. The adhesive can firmly combine the various particulate materials in the system and enhance the integrity and stability of the material. In the process of adding the adhesive, continue to stir so that the adhesive is evenly wrapped on the surface of each material particle. Finally, add the dispersant again. The dispersant can prevent the agglomeration of material particles through electrostatic repulsion or steric hindrance, so that Al-ZnO, BiSbO4 composite materials and other metal oxides are evenly and stably dispersed in water to form a dispersed system with excellent performance.

5. The method for preparing a high performance zinc oxide resistor according to claim 1, characterized in that: The operation steps of step 4 are as follows: first, spray granulation equipment is used to spray the material suspension mixed evenly in step 3 into the hot air flow in the form of droplets, so that the droplets evaporate water quickly to form particles with relatively uniform particle size; the particles obtained by spray granulation are further placed in a tablet press mold, and a certain pressure is applied to perform tableting, so that the particles are tightly combined to form a resistor sheet blank with a certain shape and strength; the pressed resistor sheet blank is further placed in a high-temperature furnace for debinding pre-sintering to fully decompose and discharge organic components such as binders in the blank; then a pre-sintering treatment is performed to preliminarily improve the strength and stability of the blank; the blank after debinding pre-sintering is further sintered at a high temperature; during the sintering process, a series of physical and chemical reactions occur inside the material, and the grains grow and densify, thereby obtaining the required material properties; and further The first step is to grind the sintered sample using a grinding device to remove the uneven parts of the sample surface and perform fine grinding to make the sample surface reach the required flatness and smoothness to meet the subsequent process requirements. The ground sample is further placed in a high-temperature furnace for heat treatment to optimize the microstructure and performance of the material, eliminate internal stress, and improve the stability of the material. Vacuum sputtering or spraying equipment is further used to evenly spray aluminum electrodes on the surface of the heat-treated sample. After the spraying is completed, the adhesion and conductivity of the electrode need to be tested. Finally, a suitable glazing process, such as dip coating, spraying, etc., is used to evenly apply a layer of glaze on the surface of the sample, and the glazed sample is placed in a low-temperature furnace and heated again to solidify the glaze and form a dense protective film on the surface of the sample to improve the corrosion resistance and insulation properties of the sample.

Images