Carbon ceramic composite conductive microsphere, ceramic resistor and preparation method

Abstract

The invention discloses a carbon ceramic composite conductive microsphere, a ceramic resistor and a preparation method, and belongs to the technical field of production of special materials of electrical equipment, and the method comprises the following steps: sequentially dipping porous mullite in a precursor solution of carbon and slurry containing carbon black, and carrying out drying treatment and carbon burying sintering to obtain the carbon ceramic composite conductive microsphere; the preparation method comprises the following steps: preparing a ceramic raw material, performing vacuum-assisted centrifugal impregnation on the ceramic raw material and slurry consisting of a binder in pug consisting of the ceramic raw material and a surfactant, sequentially performing drying and glue discharging treatment, primary isostatic pressing forming and air pressure sintering, cooling to room temperature, and performing mechanical treatment and electrode spraying to obtain the ceramic resistor. Impregnation improves the dispersibility and uniformity of the carbon material in the porous mullite to form a continuous conductive path, the carbon black-containing slurry improves the conductivity of the ceramic resistor, carbon-buried sintering generates in-situ carbon with abundant types, the combination of carbon and a ceramic interface is promoted, and the oxidation resistance, mechanical properties and electrical properties of the ceramic resistor are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of special material production for electrical equipment, and in particular relates to a carbon-ceramic composite conductive microsphere and a ceramic resistor and a preparation method thereof. Background Art

[0002] With the widespread development of electric energy utilization, ultra-high voltage transmission lines, as a vital component of the power grid system, have demonstrated significant social and economic benefits due to their advantages such as large transmission capacity and long transmission distances. Ultra-high voltage circuit breakers, as key equipment in power transmission and distribution systems, primarily serve the purpose of interrupting current in the power system. When a system fault occurs, the circuit breaker and relay protection work together to quickly cut off the fault current to prevent the accident from expanding. Therefore, the stability and reliability of the circuit breaker's operation directly impact the safe operation of the power system. Closing resistors, as a crucial component of ultra-high voltage circuit breakers, limit the closing inrush current during the circuit breaker opening and closing process, protecting the normal operation of the transmission system.

[0003] Closing resistors are complex and technically challenging to manufacture, and currently rely on imports, making them an increasingly significant constraint on the localization of ultra-high voltage transmission systems. Carbon / ceramic composite conductive materials, made with carbon materials as conductive fillers, offer numerous advantages, including low cost, simple processing, industrial production, controllable resistivity, corrosion resistance, and high-temperature resistance. They have shown great potential for application in ultra-high voltage circuit breaker closing resistors and have been widely researched. However, carbon materials tend to aggregate and disperse unevenly within the ceramic matrix, which can affect the formation of conductive pathways within the material, reduce its electrical performance, and degrade its mechanical properties.

[0004] Therefore, it is necessary to find a new preparation method to improve the dispersion of carbon materials in the ceramic matrix and reduce the agglomeration of carbon materials, so that the carbon / ceramic composite conductive material can synergistically improve the electrical and mechanical properties and better serve as a closing resistor for circuit breakers. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a carbon-ceramic composite conductive microsphere and ceramic resistor and a preparation method to solve the technical problem of how to improve the dispersion of carbon materials in the ceramic matrix and reduce agglomeration, thereby improving the electrical and mechanical properties of the ceramic resistor and meeting the closing resistance requirements of ultra-high voltage circuit breakers.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing carbon-ceramic composite conductive microspheres, comprising: The ceramic phase matrix is firstly immersed in a carbon precursor solution, then immersed in a carbon black slurry for a second time, and then dried and carbon-embedded and sintered in sequence to obtain carbon-ceramic composite conductive microspheres; The carbon precursor solution is prepared by adding ammonium cobalt acetate to tartaric acid solution and mixing them for reaction; The carbon black slurry is prepared by adding octylphenol polyoxyethylene ether to a carbon black solution and stirring the mixture for reaction; The ceramic phase matrix is porous mullite.

[0007] The preferred mass percentages of ammonium cobalt acetate, tartaric acid solution, octylphenol polyoxyethylene ether, carbon black solution, and porous mullite are (1%-2%): (50%-60%): (1%-2%): (15%-20%): (20%-35%), ensuring optimal distribution and interaction of the components within the composite. Ammonium cobalt acetate, as a catalyst, effectively catalyzes the thermal decomposition and carbonization of the tartaric acid solution, generating a catalytically active carbon material. Tartaric acid solution, as the primary carbon source, is present in a suitable proportion to ensure sufficient carbon material production. Octylphenol polyoxyethylene ether, as a surfactant, facilitates uniform dispersion of the carbon black. The addition of the carbon black solution enhances electrical conductivity. The porous mullite has an apparent porosity of 30%-60%. The high apparent porosity of the porous mullite provides ample pore space, facilitating the penetration and adhesion of the carbon material. Its inherent electrical conductivity also enhances the conductive network of the composite.

[0008] The preparation method of ammonium cobalt acetate comprises dissolving cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heating and stirring at 60-80°C for 1-4 hours, concentrating, cooling naturally, filtering, and drying at 80-100°C for 24-72 hours to crystallize, thereby obtaining ammonium cobalt acetate. Mixing cobalt acetate and ammonium acetate in an equal mass ratio ensures full contact between the two reactants, maximizes reaction conversion, reduces residual raw materials, and improves product purity and yield. A mild temperature range promotes the dissolution and ion exchange reaction of cobalt acetate and ammonium acetate while preventing reagent decomposition caused by high temperatures, ensuring reaction stability and safety. This ensures full reaction progress while avoiding energy waste caused by prolonged heating. The concentration process increases the solute concentration in the solution, creating a supersaturated environment, promoting crystallization of ammonium cobalt acetate, and improving yield. Natural cooling, rather than sudden cooling, promotes the formation of a regular crystal structure, reduces internal stress and impurity inclusions in the crystals, and produces a crystalline product with uniform particles and higher purity. The 80-100°C temperature range, above ambient temperature but below the decomposition temperature of crystalline hydrates, thoroughly removes residual moisture without destroying the crystal structure of ammonium cobalt acetate, ensuring product dryness and storage stability. The extended drying time of 24-72 hours ensures full evaporation of moisture, preventing moisture absorption or deterioration of the product due to incomplete drying.

[0009] Preferably, the temperature of the first impregnation is 40-60°C, and the time of the first impregnation is 1-4 h; the temperature of the second impregnation is 40-60°C, and the time of the second impregnation is 1-4 h; both the first impregnation and the second impregnation are carried out in a vacuum environment, maintaining the pressure at -0.098 MPa; the appropriate impregnation temperature and time ensure that the carbon precursor solution and carbon black slurry can fully penetrate into the pores of the porous mullite, and at the same time, the vacuum environment helps to remove the air in the pores, improve the impregnation effect, and make the carbon material more evenly dispersed in the ceramic phase matrix.

[0010] The mixing reaction conditions are: mixing reaction at a speed of 1100-1350 r / min and a temperature of 30-60°C for 40-100 minutes; the stirring reaction conditions are: stirring reaction at a speed of 1100-1350 r / min and a temperature of 30-60°C for 40-100 minutes. The specific mixing reaction and stirring reaction conditions ensure the full mixing and uniform dispersion of the components, avoid the agglomeration of carbon black particles, improve the dispersion and uniformity of the carbon material in the ceramic phase matrix, and are conducive to the formation of a continuous conductive path.

[0011] The drying temperature is 60-100 °C and the drying time is 18-36 h. Appropriate drying temperature and time can completely remove excess water and solvent in the composite material, avoid the generation of pores or cracks in the subsequent sintering process, and improve the density and mechanical properties of the composite material.

[0012] The carbon-embedded sintering process is preferably performed at a temperature of 800-1000°C and a holding time of 3-5 hours. This high-temperature process converts the carbon precursor solution and carbon black slurry into a rich variety of in-situ carbon materials, enhancing the composite's oxidation resistance and mechanical properties. The appropriate sintering temperature and holding time ensure a good bond between the carbon material and the ceramic matrix, forming a stable conductive path.

[0013] The present invention discloses a carbon-ceramic composite conductive microsphere, which is prepared by the above-mentioned carbon-ceramic composite conductive microsphere preparation method. The carbon-ceramic composite conductive microsphere comprises a ceramic phase porous mullite and a conductive phase carbon contained in the ceramic phase porous mullite. The diameter of the carbon-ceramic composite conductive microsphere is 80-90 μm.

[0014] The present invention discloses a method for preparing a ceramic resistor, comprising the following steps: The slurry consisting of conductive filler and binder is impregnated into the mud consisting of ceramic raw material and surfactant by vacuum-assisted centrifugal impregnation, followed by drying and binder removal, isostatic pressing and gas pressure sintering. After cooling to room temperature, mechanical treatment is performed and electrodes are sprayed to obtain a ceramic resistor. The conductive filler is a carbon ceramic composite conductive microsphere prepared by the above-mentioned preparation method of the carbon ceramic composite conductive microsphere.

[0015] Preferably, the mass percentages of the conductive filler, binder, ceramic raw material and surfactant are (5%-9%): (0.5%-1.5%): 1: (0.5%-1.5%); the conductive filler plays a key role in transmitting current, and its mass percentage is controlled at 5%-9%, which can not only ensure that the material has good electrical conductivity, but also avoid excessive filler content causing material processing difficulties or decreased mechanical properties. The binder is used to tightly combine the components to form a stable composite material structure. Its mass percentage is 0.5%-1.5%, which can not only ensure good bonding between the components, but also avoid excessive binder causing material performance degradation. The surfactant is used to improve the compatibility and dispersibility between the components, improve the processing performance of the material and the uniformity of the final product, and its mass percentage is also controlled at 0.5%-1.5% to ensure the best dispersion and compatibility effects without affecting the material properties too much.

[0016] By weight, the ceramic raw materials comprise 63%-67% bauxite, 6%-8% silica fume, 17%-19% kaolin, and 8%-12% raw clay. Bauxite, as the primary component, offers high refractory properties and excellent mechanical properties. Its weight percentage is controlled at 63%-67%, providing a stable foundation for the composite material. The addition of silica fume enhances the material's hardness and wear resistance, while also improving its sintering properties. A weight percentage of 6%-8% ensures improved performance while avoiding processing difficulties caused by excessive silica fume. Kaolin, with its excellent plasticity and bonding properties, enhances its moldability and sintered density. A weight percentage of 17%-19% provides excellent processing properties for composite material preparation. The addition of raw clay further improves its plasticity and bonding properties, while also facilitating adjustments to the sintering rate and temperature. A weight percentage of 8%-12% provides greater flexibility and controllability in composite material preparation.

[0017] The binder is polyvinyl alcohol; it has good bonding and film-forming properties, and can effectively bind the components tightly together to form a stable composite material structure.

[0018] The surfactant is lecithin, which has excellent biocompatibility and dispersibility. It can effectively improve the compatibility and dispersibility between the components, enhance the processing performance of the material and the uniformity of the final product. The addition of lecithin also helps to increase the wettability and fluidity of the material, further improving the processing performance of the material.

[0019] Preferably, the vacuum level in the vacuum-assisted centrifugal impregnation method is maintained at 0.3 atm, the rotation speed is 300-600 rpm, and the impregnation time is 2-6 hours. Controlling the vacuum level is crucial to the impregnation process. A vacuum level of 0.3 atm provides a moderate negative pressure environment, which helps the impregnation liquid penetrate more evenly into the impregnated material while avoiding excessive vacuum levels that may damage the material structure or cause excessive volatilization of the impregnation liquid. The choice of centrifugal speed directly affects the penetration speed and effectiveness of the impregnation liquid. A speed of 300-600 rpm ensures that the impregnation liquid has sufficient power to overcome the internal resistance of the material and penetrate deeply into the material, while also avoiding material damage or impregnation liquid splashing caused by excessive speeds. The setting of the impregnation time requires comprehensive consideration of factors such as the viscosity of the impregnation liquid, the pore structure of the material, and the penetration depth. An impregnation time of 2-6 hours ensures that the impregnation liquid fully penetrates the material while avoiding excessive impregnation times that may cause changes in material properties or waste of impregnation liquid.

[0020] The drying temperature is 60-100°C, and the drying time is 18-36 hours. The selection of the drying temperature needs to take into account factors such as the thermal stability of the material, the volatility of the impregnation liquid, and the drying efficiency. Within this temperature range, the impregnation liquid can evaporate quickly and completely while avoiding thermal damage or performance changes to the material caused by excessive temperatures. The drying time must be set to ensure complete evaporation of the moisture or impregnation liquid within the material while avoiding material aging or performance degradation caused by excessive drying times. A drying time of 18-36 hours can both meet this requirement and improve production efficiency.

[0021] Preferably, the pressure of the primary isostatic pressing is 200-300 MPa; within this pressure range, the material can be fully compacted to achieve the required density and strength, while avoiding material rupture or performance degradation caused by excessive pressure.

[0022] The sintering temperature of gas pressure sintering is 1300-1400 ℃, and the holding time is 2-4 h. Within this temperature range, the material can undergo sufficient solid-phase reaction to form a dense sintered body, while avoiding overheating of the material or deterioration of performance due to excessively high temperature. The setting of the holding time needs to ensure that the material has sufficient reaction time during the sintering process to achieve the required phase composition and microstructure. A holding time of 2-4 h can not only meet this requirement, but also improve production efficiency. Gas pressure sintering can achieve rapid densification of materials at higher temperatures and pressures, significantly improve the mechanical properties, thermal stability and corrosion resistance of the materials, and provide a broad space for the application of materials.

[0023] The present invention discloses a ceramic resistor, which is prepared by the above-mentioned preparation method of the ceramic resistor, and the volume density of the ceramic resistor is ≥2.25 g / cm 3 .

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing carbon ceramic composite conductive microspheres. First, a carbon precursor solution and a carbon black slurry are successively impregnated into porous mullite by an impregnation method, thereby promoting the carbon precursor solution to better penetrate into the carrier pore structure of the porous mullite and ensuring that the porous mullite is wrapped by the carbon black slurry, which helps to improve the dispersion and uniformity of the carbon material in the ceramic phase matrix, thereby facilitating the formation of a continuous conductive path. The direct introduction of carbon black also improves the conductive performance of the conductive filler. After drying treatment and carbon embedding sintering process treatment, carbon ceramic composite conductive microspheres are prepared. The drying treatment removes excess water and solvent, and the carbon embedding sintering process promotes the conversion of the carbon precursor solution and the carbon black slurry into a rich variety of in-situ carbon materials, improves the antioxidant properties of the composite material, and promotes the bonding between the carbon and ceramic interface, thereby improving the mechanical properties and electrical properties of the ceramic resistor. The process uses a tartaric acid solution as the precursor solution, a carbon black solution as the added carbon source, ammonium cobalt acetate as the catalyst, octylphenol polyoxyethylene ether as the surfactant, and porous mullite as the ceramic matrix. The ammonium cobalt acetate catalyst catalyzes the thermal decomposition and carbonization of the tartaric acid solution, producing a catalytically active carbon material. This carbon material is then better bonded to the ceramic matrix during the subsequent sintering process, forming a stable conductive pathway. The octylphenol polyoxyethylene ether, as the surfactant, effectively disperses the carbon black particles in the carbon black solution and prevents agglomeration. This facilitates uniform distribution of the carbon black within the ceramic matrix, thereby improving the conductive filler's performance. Porous mullite, with its excellent pore structure and thermal stability, can accommodate a large amount of carbon material and provide attachment points. Furthermore, porous mullite itself possesses a certain degree of conductivity, and when combined with the carbon material, it forms a more complete conductive network, thereby enhancing the conductive properties of the ceramic resistor made from the carbon-ceramic composite conductive microspheres. The disclosed method for preparing carbon-ceramic composite conductive microspheres not only simplifies the experimental process but also improves the dispersion and uniformity of the carbon material within the ceramic matrix, reducing carbon agglomeration and facilitating the formation of a continuous conductive pathway. Furthermore, the application of a carbon-embedded sintering process enhances the composite's oxidation resistance and mechanical properties, enabling the resulting ceramic resistor to achieve synergistically controlled mechanical and electrical properties.

[0025] The present invention also discloses a carbon-ceramic composite conductive microsphere, which is prepared by the above-mentioned preparation method. The carbon material in the carbon-ceramic composite conductive microsphere is evenly distributed in the ceramic phase matrix, forming a continuous conductive path. The carbon material includes carbon converted from a carbon precursor solution and directly introduced carbon black, which enriches the types of carbon materials. The diverse carbon materials form a more complex conductive network in the ceramic phase matrix, further improving the conductivity and stability of the ceramic resistor. This structure makes the transmission of electrons in the ceramic resistor smoother, thereby significantly improving the conductivity of the ceramic resistor. The carbon material forms a stable structure in the ceramic matrix, which helps to resist the corrosion of the ceramic resistor by oxidation and can maintain stable conductivity and mechanical properties under high temperature or harsh environment. When the carbon-ceramic composite conductive microsphere is used in the preparation of closing resistors for ultra-high voltage transmission lines, the ultra-high voltage transmission lines require the closing resistors to have extremely high conductivity and voltage resistance. The carbon material in carbon-ceramic composite conductive microspheres provides an excellent conductive path, while the ceramic matrix has high voltage resistance. The resulting closing resistors for ultra-high voltage transmission lines can operate stably in ultra-high voltage environments, ensuring efficient current transmission while resisting potential damage from high voltage. In ultra-high voltage transmission lines, closing resistors can generate significant heat due to excessive current. Carbon-ceramic composite conductive microspheres, combining the high thermal stability of ceramics with the thermal conductivity of carbon materials, can effectively disperse and withstand this heat, preventing damage to the resistors due to overheating, thereby improving system safety and reliability. Ultra-high voltage transmission lines are often exposed to harsh natural environments such as high temperature, humidity, and salt spray. Carbon-ceramic composite conductive microspheres have excellent oxidation and corrosion resistance, which can resist the erosion of these environmental factors and extend the service life of the closing resistors.

[0026] The present invention also discloses a method for preparing a ceramic resistor, which uses the carbon ceramic composite conductive microspheres obtained by the above preparation method as a conductive filler, which can synergistically control the mechanical properties and electrical properties. The conventional method for preparing ceramic resistors is to directly mix the carbon material with the ceramic raw material, and then shape it through mechanical forming technology and sinter it. However, this method has a big problem. Since the conductive filler is difficult to disperse evenly and not agglomerate in the ceramic phase matrix, it results in a large and unstable ceramic resistivity. The carbon ceramic composite conductive microspheres obtained by the above preparation method of the present invention are used as conductive fillers and can form a continuous conductive path in the ceramic phase matrix, synergistically improving the mechanical properties and electrical properties of the ceramic resistor.

[0027] The present invention also discloses a ceramic resistor, which is prepared using the above-mentioned preparation method. The carbon material forms a continuous conductive path inside the ceramic phase matrix, and the carbon material itself has good conductivity. Therefore, the ceramic resistor prepared has excellent conductive properties. This high-performance conductivity enables the ceramic resistor to transmit current more efficiently in electrical equipment, reducing energy consumption. A strong interfacial bond is formed between the carbon material and the ceramic matrix in the carbon-ceramic composite conductive microspheres, and this bond enhances the overall structural stability of the ceramic resistor. Therefore, the prepared ceramic resistor has higher mechanical strength and impact resistance, and can maintain its integrity and performance in harsh environments. DETAILED DESCRIPTION

[0028] To help those skilled in the art better understand the present invention, the following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms “include” and “have” and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatuses.

[0030] The present invention is described in further detail below: The present invention discloses a method for preparing carbon ceramic composite conductive microspheres, comprising the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 60-80°C for 1-4 hours, concentrate, naturally cool, filter, and dry at 80-100°C for 24-72 hours to crystallize to obtain ammonium cobalt acetate. Weigh 1%-2% by mass of the catalyst ammonium cobalt acetate into a 50%-60% tartaric acid solution and stir in a water bath on a magnetic stirrer at 1100-1350 rpm at 30-60°C for 40-100 minutes until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0031] S2. 1%-2% of the surfactant octylphenol polyoxyethylene ether is weighed in percentage by mass and placed in a 15%-20% carbon black solution. The mixture is stirred on a magnetic stirrer at a speed of 1100-1350 r / min and at 30-60°C for 40-100 min to obtain a carbon black slurry. The carbon black solution is prepared by uniformly mixing carbon black powder and deionized water in a mass ratio of 1:1.

[0032] S3. Place 20%-35% porous mullite by mass in a vacuum chamber. Start the vacuum pump to remove the gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 40-60°C for 1-4 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 40-60°C for another 1-4 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0033] S4. Place the impregnated porous mullite in an electric blast dryer at 60-100°C for 18-36 hours until it is completely dry.

[0034] S5. The porous mullite powder after impregnation and drying is formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample is then buried in a corundum-mullite crucible. Coke is filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible is placed in a high-temperature furnace and kept at 800-1000°C for 3-5 hours for carbon sintering to ensure that the tartaric acid is completely pyrolyzed and carbonized into carbon material. After the insulation is completed, the sample is taken out after cooling to room temperature with the furnace to obtain carbon-ceramic composite conductive microspheres.

[0035] The present invention discloses a method for preparing a ceramic resistor, comprising the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0036] S6. In terms of mass percentage, 1 part of ceramic raw material, 5%-9% of conductive filler carbon ceramic composite conductive microspheres, 0.5%-1.5% of binder polyvinyl alcohol, and 0.5%-1.5% of surfactant lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 63%-67% of bauxite, 6%-8% of silicon micropowder, 17%-19% of kaolin and 8%-12% of raw clay; the slurry consisting of the conductive filler and the binder is impregnated into the mud consisting of the ceramic raw material and the surfactant in a robot single-cylinder dipping and spinning coating machine through vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is maintained at 0.3 atm, the rotation speed is 300-600 rpm, the impregnation time is 2-6 h, and the ceramic slurry is obtained by mixing.

[0037] S7. Place the ceramic slurry in a 60-100°C oven and dry it for 18-36 hours to completely dry and remove binder. Then, perform isostatic pressing at 200-300 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0038] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1300-1400 °C for 2-4 h. After the insulation is completed, cool it to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0039] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0040] The ceramic resistor disclosed in the present invention uses carbon ceramic composite conductive microspheres as conductive fillers, and the volume density of the prepared ceramic resistor is ≥2.25 g / cm 3 .

[0041] The present invention discloses carbon-ceramic composite conductive microspheres comprising, by mass percentage, 50%-60% tartaric acid solution as a carbon precursor, 15%-20% carbon black solution as nanocarbon, 20%-35% porous mullite as a ceramic matrix, 1%-2% ammonium cobalt acetate as a catalyst, and 1%-2% octylphenol polyoxyethylene ether as a catalyst. The carbon-ceramic composite conductive microspheres are obtained through impregnation, drying, and sintering. The porous mullite has an apparent porosity of 30%-60%. The impregnation method utilizes vacuum-assisted impregnation: the porous mullite is placed in a vacuum vat, and the tartaric acid precursor solution and carbon black slurry are sequentially injected into the vat at 40-60°C for 1-4 hours. The resulting carbon-ceramic composite conductive microspheres are composed of a conductive carbon phase and a ceramic porous mullite phase, and have a diameter of 80-90 μm.

[0042] The present invention discloses a ceramic resistor. The raw materials include, by mass percentage, 1 part of a conductive filler, 63%-67% of bauxite, 6%-8% of silicon powder, 17%-19% of kaolin, 8%-12% of raw clay, 0.5%-1.5% of a binder polyvinyl alcohol (PVA), and 0.5%-1.5% of a surfactant lecithin. The ceramic resistor is obtained by vacuum-assisted centrifugal impregnation, drying, single-stage isostatic pressing, gas pressure sintering, mechanical treatment, and spraying with silver electrodes.

[0043] The present invention uses an impregnation method to successively impregnate porous mullite with a carbon precursor solution and a carbon black slurry, thereby promoting better penetration of the carbon precursor solution into the carrier pore structure of the porous mullite and ensuring that the porous mullite is wrapped by the carbon black slurry containing nano-carbon black. After drying and carbon-burying sintering processes, the carbon precursor solution and the carbon black slurry are converted into a rich variety of in-situ carbon materials to obtain carbon ceramic composite conductive microspheres. The carbon ceramic composite conductive microspheres are then used as conductive fillers and are mixed with ceramic raw materials, a binder of polyvinyl alcohol, and a surfactant of lecithin through vacuum-assisted centrifugal impregnation, a single isostatic pressing, and a gas pressure sintering process to finally obtain a ceramic resistor. The volume density of the prepared ceramic resistor is ≥2.25 g / cm 3 .

[0044] The present invention utilizes carbon-ceramic composite conductive microspheres prepared by an impregnation method as conductive fillers, which not only simplifies the experimental process but, more importantly, improves the dispersion and uniformity of the carbon material within the ceramic matrix, reduces carbon agglomeration, and facilitates the formation of a continuous conductive pathway within the ceramic matrix, thereby enhancing the electrical properties of the ceramic resistor. Furthermore, the introduction of nanocarbon black into the carbon black slurry also enriches the variety of carbon materials. The application of a carbon-embedded sintering process improves the ceramic resistor's oxidation resistance, promotes bonding between the carbon and ceramic interfaces, ensures the overall structural stability of the ceramic resistor, and enhances its mechanical properties, thereby enabling it to better serve as a closing resistor for circuit breakers.

[0045] The conventional method for preparing ceramic resistors is to directly mix carbon materials with ceramic raw materials, then shape them into a shape through mechanical forming technology and then sinter them. However, this method has a major problem. Since the conductive filler is difficult to disperse evenly in the ceramic matrix and easily agglomerates, the ceramic resistivity is large and unstable. The present invention obtains carbon-ceramic composite conductive microspheres by impregnating a carbon precursor solution and a carbon black slurry into a ceramic phase matrix, and then performing carbon embedding sintering. The carbon-ceramic composite conductive microspheres act as conductive fillers to form a continuous conductive path in the ceramic phase matrix, thereby synergistically improving the mechanical and electrical properties of the ceramic resistor. Tartaric acid solution, ammonium cobalt acetate, carbon black solution, octylphenol polyoxyethylene ether, porous mullite, bauxite, silicon powder, kaolin, raw clay, polyvinyl alcohol and lecithin are used as raw materials, tartaric acid solution is used as a precursor solution, carbon black solution is used as a carbon source, ammonium cobalt acetate is used as a catalyst, octylphenol polyoxyethylene ether is used as a surfactant, porous mullite is used as a ceramic phase matrix, carbon ceramic composite conductive microspheres prepared by an impregnation method and a carbon-buried sintering process are used as a conductive filler, and vacuum-assisted centrifugal impregnation, drying, single isostatic pressing, gas pressure sintering treatment, mechanical treatment, and spraying silver electrodes are finally obtained. A ceramic resistor with carbon ceramic composite conductive microspheres as a conductive filler is obtained. The ceramic resistor prepared by the present invention has carbon material fully and evenly dispersed in the ceramic phase matrix, so that the prepared ceramic resistor can synergistically control mechanical properties and electrical properties.

[0046] Under the raw material ratio given in the present invention, and combined with the impregnation process and the carbon-embedded sintering process, a ceramic resistor with carbon-ceramic composite conductive microspheres as conductive filler is prepared. The prepared ceramic resistor has excellent performance when used as a closing resistor for ultra-high voltage transmission line circuit breakers.

[0047] The experimental methods in the following examples are conventional experimental methods unless otherwise specified; the materials used in the examples are purchased from conventional chemical reagent companies unless otherwise specified.

[0048] The carbon-ceramic composite conductive microspheres disclosed in the present invention serve as a conductive filler. Tartaric acid solution serves as a precursor solution, carbon black solution serves as an external carbon source, ammonium cobalt acetate serves as a catalyst, octylphenol polyoxyethylene ether serves as a surfactant, and porous mullite serves as a ceramic matrix. First, the porous mullite is impregnated with the carbon precursor solution and then with a carbon black slurry, thereby promoting better penetration of the carbon precursor solution into the pore structure of the porous mullite support and ensuring that the porous mullite is encapsulated by the carbon black slurry. The carbon-ceramic composite conductive microspheres are then dried and carbon-embedded and sintered to produce the carbon-ceramic composite conductive microspheres. The prepared carbon-ceramic composite conductive microspheres are then mixed with ceramic raw materials (bauxite, silica powder, kaolin, and raw clay), a binder (polyvinyl alcohol), and a surfactant (lecithin) through vacuum-assisted centrifugal impregnation, single-stage isostatic pressing, and gas pressure sintering to produce a ceramic resistor containing the carbon-ceramic composite conductive microspheres as a conductive filler. The impregnation process helps the carbon precursor solution and the carbon black slurry to contact each other in the porous mullite ceramic phase matrix, which is beneficial to the further dispersion of a rich variety of carbon materials in the ceramic raw materials and the formation of conductive pathways, thereby improving the conductivity of the ceramic resistor; at the same time, the use of the carbon-buried sintering process can improve the oxidation resistance of the ceramic resistor, promote the bonding between the carbon and ceramic interfaces, and improve the mechanical properties of the ceramic resistor, so that the ceramic resistor with the prepared carbon-ceramic composite conductive microspheres as conductive fillers can synergistically control the mechanical properties and electrical properties.

[0049] Ammonium cobalt acetate is a catalyst synthesized in the laboratory. It is a mixture of cobalt acetate and ammonium acetate. The CAS registration number of cobalt acetate is 71-48-7, and the CAS registration number of ammonium acetate is 631-61-8.

[0050] In the following examples, a tartaric acid solution prepared from tartaric acid (purity ≥99.0%) was used as a carbon source precursor, a carbon black solution prepared from nano-carbon black (300-700 nm) was used as a direct carbon source, ammonium cobalt acetate was used as a catalyst, octylphenol polyoxyethylene ether (purity ≥99.0%) and lecithin (purity ≥99.0%) were used as surfactants, porous mullite (200 mesh) was used as a ceramic phase matrix, bauxite (100 mesh), kaolin (100 mesh), raw clay (100 mesh) and silica powder (200 mesh) were used as ceramic raw materials, and polyvinyl alcohol (purity ≥99.0%) was used as a binder; all purities mentioned above are expressed in mass percentages.

[0051] Example 1 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 80°C for 4 h, concentrate, naturally cool, filter, and dry at 80°C for 72 h to crystallize to obtain ammonium cobalt acetate. Weigh 2% by mass of ammonium cobalt acetate into a 60% tartaric acid solution and stir at 60°C on a magnetic stirrer in a water bath at 1350 rpm for 100 min until the ammonium cobalt acetate and tartaric acid solution are uniformly mixed, thereby obtaining a carbon precursor solution.

[0052] S2. Weigh 2% of octylphenol polyoxyethylene ether by mass percentage and place it in a 20% carbon black solution. Stir the mixture on a water bath heating magnetic stirrer at a speed of 1350 r / min and 60°C for 100 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0053] S3. Place 35% porous mullite (by mass percentage) in a vacuum chamber with an apparent porosity of 60%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 60°C for 4 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 60°C for another 4 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0054] S4. Place the impregnated porous mullite in an electric blast dryer at 60°C for 36 hours until it is completely dry.

[0055] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 83 μm.

[0056] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0057] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1.5% of polyvinyl alcohol and 1.5% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 64% of bauxite, 8% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0058] S7. Place the ceramic slurry in an oven at 80°C for 30 hours for complete drying and binder removal, and then perform isostatic pressing at 300 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0059] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1400°C and a holding time of 4 hours. After the holding time is completed, cool the green body to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0060] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0061] The ceramic resistor prepared in Example 1 was sampled and inspected, and the performance indicators were as follows: the volume density was 2.35 g / cm 3 , compressive strength of 242 MPa, resistance of 4.78 Ω, temperature resistance coefficient of -0.043% / ℃, voltage coefficient of -1.66%cm / kV. It meets the performance requirements of the industry standard for new carbon ceramic closing resistors, that is, volume density ≥ 2.25 g / cm 3 , compressive strength ≥120 MPa, resistance value 5±0.25 Ω, temperature resistivity of -0.05~0.1% / ℃, voltage coefficient of -7.5~-0.5% cm / kV.

[0062] It should be noted that the bulk density is tested by the weighing method in accordance with GB / T 25995~2010, and the compressive strength is tested by the pressure test in accordance with GB / T 8489~2006.

[0063] Example 2 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 60°C for 1 hour, concentrate, naturally cool, filter, and dry at 100°C for 24 hours to crystallize to obtain ammonium cobalt acetate. Weigh 1% by mass of ammonium cobalt acetate into a 50% tartaric acid solution and stir at 30°C on a magnetic stirrer in a water bath at 1100 rpm for 40 minutes until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0064] S2. Weigh 1% of octylphenol polyoxyethylene ether by mass and place it in a 15% carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1100 r / min and 30°C for 40 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0065] S3. Place 20% porous mullite (by mass percentage) in a vacuum chamber with an apparent porosity of 30%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion at 40°C for 1 hour. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion at 40°C for another 1 hour. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0066] S4. Place the impregnated porous mullite in an electric blower dryer at 100°C for 18 hours until it is completely dry.

[0067] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 83 μm.

[0068] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0069] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1.5% of polyvinyl alcohol and 1.5% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 64% of bauxite, 8% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0070] S7. Place the ceramic slurry in an oven at 80°C for 30 hours for complete drying and binder removal, and then perform isostatic pressing at 200 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0071] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1400°C and a holding time of 4 hours. After the holding time is completed, cool the green body to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0072] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0073] The ceramic resistor prepared in Example 2 was sampled and inspected, and the performance indicators were as follows: the volume density was 2.30 g / cm 3 The product has a compressive strength of 201 MPa, a resistance of 4.85 Ω, a temperature resistivity of -0.042% / °C, and a voltage coefficient of -1.39% cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0074] Example 3 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 70°C for 2 h, concentrate, naturally cool, filter, and dry at 90°C for 36 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir in a water bath with a magnetic stirrer at 1250 rpm at 40°C for 80 min until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0075] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% of carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1250 r / min and 40°C for 80 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0076] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0077] S4. Place the impregnated porous mullite in an electric blast dryer at 80°C for 20 hours until it is completely dry.

[0078] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 83 μm.

[0079] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0080] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1.5% of polyvinyl alcohol and 1.5% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 64% of bauxite, 8% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0081] S7. Place the ceramic slurry in an oven at 80°C for 30 hours for complete drying and binder removal, and then perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0082] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1400°C and a holding time of 4 hours. After the holding time is completed, cool the green body to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0083] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0084] The ceramic resistor prepared in Example 3 was sampled and inspected, and the performance indicators were as follows: the volume density was 2.31 g / cm 3 The product has a compressive strength of 193 MPa, a resistance of 4.87 Ω, a temperature resistivity of -0.045% / °C, and a voltage coefficient of -1.76% cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0085] Example 4 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 65°C for 3 h, concentrate, naturally cool, filter, and dry at 85°C for 60 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir at 60°C in a water bath on a magnetic stirrer at 1350 rpm for 100 min until the ammonium cobalt acetate and tartaric acid solution are uniformly mixed, thereby obtaining a carbon precursor solution.

[0086] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1350 r / min and 60°C for 100 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0087] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0088] S4. Place the impregnated porous mullite in an electric blast dryer at 80°C for 20 hours until it is completely dry.

[0089] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 83 μm.

[0090] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0091] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1.5% of polyvinyl alcohol and 1.5% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 64% of bauxite, 8% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0092] S7. Place the ceramic slurry in an oven at 80°C for 30 hours for complete drying and binder removal, and then perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0093] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1400°C and a holding time of 4 hours. After the holding time is completed, cool the green body to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0094] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0095] The ceramic resistor prepared in Example 4 was sampled and inspected, and the performance indicators were as follows: volume density was 2.32 g / cm 3The product has a compressive strength of 218 MPa, a resistance of 4.89 Ω, a temperature resistivity of -0.037% / °C, and a voltage coefficient of -1.43%cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0096] Example 5 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 75°C for 2 h, concentrate, naturally cool, filter, and dry at 95°C for 30 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir in a water bath with a magnetic stirrer at 1250 rpm at 40°C for 80 min until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0097] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% of carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1250 r / min and 40°C for 80 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0098] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0099] S4. Place the impregnated porous mullite in an electric blast dryer at 60°C for 36 hours until it is completely dry.

[0100] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 1000°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 80 μm.

[0101] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0102] S6. In terms of mass percentage, 1 part of ceramic raw material, 8% of carbon-ceramic composite conductive microspheres, 1% of polyvinyl alcohol and 1% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 63% of bauxite, 8% of silicon powder, 17% of kaolin and 12% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 600 rpm, the impregnation time is 6 h, and the ceramic slurry is obtained by mixing.

[0103] S7. Place the ceramic slurry in a 60°C oven and dry it for 36 hours to completely dry and remove binder. Then, perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0104] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1300°C for 2 hours. After the insulation is completed, cool it to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0105] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0106] The ceramic resistor prepared in Example 5 was sampled and inspected, and the performance indicators were as follows: the volume density was 2.26 g / cm 3 The product has a compressive strength of 166 MPa, a resistance of 5.08 Ω, a temperature resistivity of -0.066% / °C, and a voltage coefficient of -1.34% cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0107] Example 6 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 70°C for 2 h, concentrate, naturally cool, filter, and dry at 90°C for 48 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir in a water bath with a magnetic stirrer at 1250 rpm at 40°C for 80 min until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0108] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% of carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1250 r / min and 40°C for 80 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0109] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0110] S4. Place the impregnated porous mullite in an electric blast dryer at 60°C for 36 hours until it is completely dry.

[0111] S5. The porous mullite powder after impregnation and drying treatment was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 3 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 90 μm.

[0112] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0113] S6. In terms of mass percentage, 1 part of ceramic raw material, 5% of carbon-ceramic composite conductive microspheres, 0.5% of polyvinyl alcohol and 0.5% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 67% of bauxite, 6% of silicon powder, 19% of kaolin and 8% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 300 rpm, the impregnation time is 2 h, and the ceramic slurry is obtained by mixing.

[0114] S7. Place the ceramic slurry in a 100°C oven and dry it for 18 h to completely dry and remove binder. Then, perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0115] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1300°C for 3 hours. After the insulation is completed, cool it to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0116] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0117] The ceramic resistor prepared in Example 6 was sampled and inspected, and the performance indicators were as follows: volume density was 2.28 g / cm 3 The product has a compressive strength of 174 MPa, a resistance of 4.92 Ω, a temperature resistivity of -0.034% / °C, and a voltage coefficient of -0.82%cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0118] Example 7 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 70°C for 2 h, concentrate, naturally cool, filter, and dry at 90°C for 36 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir in a water bath with a magnetic stirrer at 1250 rpm at 40°C for 80 min until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0119] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% of carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1250 r / min and 40°C for 80 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0120] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0121] S4. Place the impregnated porous mullite in an electric blast dryer at 60°C for 36 hours until it is completely dry.

[0122] S5. The porous mullite powder after impregnation and drying treatment was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 900°C for 4 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 82 μm.

[0123] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0124] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1% of polyvinyl alcohol and 1% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 65% of bauxite, 7% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0125] S7. Place the ceramic slurry in an oven at 80°C for 30 hours for complete drying and binder removal, and then perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0126] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1350°C for 3 hours. After the insulation is completed, cool it to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0127] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0128] The ceramic resistor prepared in Example 7 was sampled and inspected, and the performance indicators were as follows: volume density was 2.29 g / cm 3The product has a compressive strength of 181 MPa, a resistance of 4.90 Ω, a temperature resistivity of -0.052% / °C, and a voltage coefficient of -1.81%cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0129] Example 8 A method for preparing carbon ceramic composite conductive microspheres comprises the following steps: S1. Dissolve cobalt acetate and ammonium acetate in a 1:1 mass ratio in deionized water, heat and stir at 70°C for 2 h, concentrate, naturally cool, filter, and dry at 90°C for 36 h to crystallize to obtain ammonium cobalt acetate. Weigh 1.5% by mass of ammonium cobalt acetate into a 55% tartaric acid solution and stir in a water bath with a magnetic stirrer at 1250 rpm at 40°C for 80 min until the ammonium cobalt acetate and tartaric acid solution are evenly mixed, thereby obtaining a carbon precursor solution.

[0130] S2. Weigh 1.5% of octylphenol polyoxyethylene ether by mass percentage and place it in 18% of carbon black solution. Stir the mixture on a water bath heated magnetic stirrer at a speed of 1250 r / min and 40°C for 80 min until the mixture is uniformly stirred to obtain a carbon black slurry.

[0131] S3. Place 30% porous mullite (by mass percentage) in a vacuum chamber, with an apparent porosity of 45%. Start a vacuum pump to remove gas from the chamber. When the pressure reading stabilizes at -0.098 MPa, slowly open the valve connected to the precursor solution. First, completely inject the carbon precursor solution into the vacuum chamber. Close the valve and perform a primary impregnation, maintaining the immersion temperature at 35°C for 2 hours. Then, inject the carbon black slurry and perform a secondary impregnation, maintaining the immersion temperature at 55°C for another 2 hours. Ensure that the porous mullite is fully infiltrated. After the impregnation is complete, turn off the vacuum pump and remove the sample.

[0132] S4. Place the impregnated porous mullite in an electric blast dryer at 60°C for 36 hours until it is completely dry.

[0133] S5. The porous mullite powder after impregnation and drying was formed into a φ35 mm × 30 mm cylindrical sample at 4 MPa and placed in a graphite crucible. The sample was then buried in a corundum-mullite crucible. Coke was filled in the gap between the graphite crucible and the corundum-mullite crucible. Finally, the corundum-mullite crucible was placed in a high-temperature furnace and kept at 800°C for 5 h for carbon sintering to ensure that the tartaric acid was completely pyrolyzed and carbonized into carbon material. After the insulation was completed, the sample was cooled to room temperature with the furnace and then taken out to obtain carbon-ceramic composite conductive microspheres with a diameter of 83 μm.

[0134] A method for preparing a ceramic resistor comprises the following steps: Steps S1 to S5 are the same as the preparation method of carbon-ceramic composite conductive microspheres, with carbon-ceramic composite conductive microspheres being used as conductive fillers.

[0135] S6. In terms of mass percentage, 1 part of ceramic raw material, 9% of carbon-ceramic composite conductive microspheres, 1% of polyvinyl alcohol and 1% of lecithin are added to deionized water. In terms of mass percentage, the ceramic raw material includes 65% of bauxite, 7% of silicon powder, 18% of kaolin and 10% of raw clay. The slurry consisting of carbon-ceramic composite conductive microspheres and polyvinyl alcohol is impregnated into the mud consisting of the ceramic raw material and lecithin in a manipulator single-cylinder dip-spinning coating machine by vacuum-assisted centrifugal impregnation. The vacuum degree of the vacuum-assisted centrifugal impregnation is controlled to be maintained at 0.3 atm, the rotation speed is 400 rpm, the impregnation time is 3 h, and the ceramic slurry is obtained by mixing.

[0136] S7. Place the ceramic slurry in a 60°C oven and dry it for 36 hours to completely dry and remove binder. Then, perform isostatic pressing at 260 MPa in a dry belt cold isostatic press to obtain a ceramic green body.

[0137] S8. Place the ceramic green body in an inert atmosphere for gas pressure sintering at a sintering temperature of 1350°C for 4 hours. After the insulation is completed, cool it to room temperature with the furnace, take out the green body, and obtain a ceramic resistor green body.

[0138] S9. Mechanically process the ceramic resistor body and spray electrodes to obtain a ceramic resistor.

[0139] The ceramic resistor prepared in Example 8 was sampled and inspected, and the performance indicators were as follows: volume density was 2.29 g / cm 3 The product has a compressive strength of 186 MPa, a resistance of 4.98 Ω, a temperature resistivity of -0.055% / °C, and a voltage coefficient of -1.98% cm / kV. This meets the performance requirements of industry standards for new carbon ceramic closing resistors.

[0140] Comparative Example 1 The difference from Example 1 is that in step S3, the time of the first immersion is 10 minutes, the time of the second immersion is 10 minutes, and in step S6, the time of the vacuum-assisted centrifugal immersion is 20 minutes.

[0141] The ceramic resistor prepared in Comparative Example 1 was sampled and inspected, and the performance indicators were as follows: the volume density was 1.72 g / cm 3The ceramic resistor prepared in Comparative Example 1 exhibited compressive strength of 105 MPa, a resistance of 10.82 Ω, and a large resistivity deviation, with a temperature resistivity of -0.018% / °C and a voltage coefficient of -3.2% cm / kV. By comparison, the mechanical and electrical properties of the ceramic resistor prepared in Comparative Example 1 were significantly lower than those of the ceramic resistor prepared in Example 1. The ceramic resistor prepared in the present invention exhibited excellent mechanical properties, a lower and more stable resistivity, and high mechanical strength, effectively ensuring safe product operation.

[0142] Comparative Example 2 The difference from Example 1 is that in step S6, the amount of carbon-ceramic composite conductive microspheres added to the ceramic raw material is 3% by mass.

[0143] The ceramic resistor prepared in Comparative Example 2 was sampled and inspected, and the performance indicators were as follows: the volume density was 2.39 g / cm 3 , compressive strength of 199 MPa, resistance of 10.37 Ω, temperature resistivity of -0.014% / °C, and voltage coefficient of -2.7% cm / kV. By comparison, the mechanical and electrical properties of the ceramic resistor prepared in Comparative Example 2 are far inferior to those of the ceramic resistor prepared in Example 1. The ceramic resistor prepared in the present invention exhibits excellent mechanical properties, low and more stable resistivity, and high mechanical strength, effectively ensuring safe product operation.

[0144] Comparative Example 3 The difference from Example 1 is that in step S8, the sintering temperature is 1200°C.

[0145] The ceramic resistor prepared in Comparative Example 3 was sampled and inspected, and the performance indicators were as follows: volume density was 2.01 g / cm 3 The ceramic resistor prepared in Comparative Example 3 exhibited significantly lower mechanical and electrical properties than the ceramic resistor prepared in Example 1, with a compressive strength of 133 MPa and a resistance of 8.96 Ω. The temperature resistivity was -0.021% / °C, and the voltage coefficient was -0.96% cm / kV. The ceramic resistor prepared in Comparative Example 3 exhibited significantly lower mechanical and electrical properties than the ceramic resistor prepared in Example 1. The ceramic resistor prepared in the present invention exhibited superior mechanical properties, a relatively low and more stable resistivity, and high mechanical strength, effectively ensuring safe product operation.

[0146] Table 1 Comparison of performance indicators of ceramic resistors prepared in Examples 1-8 and Comparative Examples 1-3

[0147] Table 1 shows a comparison of the performance indicators of the ceramic resistors prepared in Examples 1-8 and Comparative Examples 1-3. As can be seen from the table, the ceramic resistors prepared in Examples 1-8 disclosed in the present invention, after sampling inspection, all meet the performance requirements of the industry standard for new carbon ceramic switching resistors, that is, the volume density is ≥2.25 g / cm3 , compressive strength ≥120 MPa, resistance 5±0.25 Ω, temperature resistivity of -0.05~0.1% / °C, and voltage coefficient of -7.5~-0.5% cm / kV. The mechanical and electrical properties of the ceramic resistors prepared in Comparative Examples 1-3 were significantly lower than those of the ceramic resistors prepared in Examples 1-8 of the present invention. The ceramic resistors prepared in the present invention exhibit excellent mechanical properties, low and more stable resistivity, and high mechanical strength, effectively ensuring safe product operation.

[0148] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing carbon ceramic composite conductive microspheres, characterized in that: include: The ceramic phase matrix is firstly immersed in a carbon precursor solution, then immersed in a carbon black slurry for a second time, and then dried and carbon-embedded and sintered in sequence to obtain carbon-ceramic composite conductive microspheres; The carbon precursor solution is prepared by adding ammonium cobalt acetate to a tartaric acid solution and mixing them for reaction; The carbon black slurry is prepared by adding octylphenol polyoxyethylene ether to a carbon black solution and stirring the mixture for reaction; The ceramic phase matrix is porous mullite.

2. The method for preparing carbon ceramic composite conductive microspheres according to claim 1, characterized in that: The mass percentages of the ammonium cobalt acetate, tartaric acid solution, octylphenol polyoxyethylene ether, carbon black solution and porous mullite are (1%-2%): (50%-60%): (1%-2%): (15%-20%): (20%-35%); the apparent porosity of the porous mullite is 30%-60%; The preparation method of ammonium cobalt acetate comprises: dissolving cobalt acetate and ammonium acetate in a mass ratio of 1:1 in deionized water, heating and stirring at 60-80°C for 1-4 hours, concentrating, naturally cooling and filtering, and drying at 80-100°C for 24-72 hours to crystallize, thereby obtaining ammonium cobalt acetate.

3. The method for preparing carbon ceramic composite conductive microspheres according to claim 1, characterized in that: The temperature of the first impregnation is 40-60°C, and the time of the first impregnation is 1-4 hours; the temperature of the second impregnation is 40-60°C, and the time of the second impregnation is 1-4 hours; the first impregnation and the second impregnation are both carried out in a vacuum environment, maintaining the pressure at -0.098 MPa; The mixing reaction conditions are: a rotation speed of 1100-1350 r / min, a mixing reaction at 30-60°C for 40-100 min; The stirring reaction conditions are: stirring the reaction at a speed of 1100-1350 r / min, at 30-60°C for 40-100 min; The drying temperature is 60-100° C., and the drying time is 18-36 h.

4. The method for preparing carbon ceramic composite conductive microspheres according to claim 1, characterized in that: The temperature of the carbon-embedded sintering is 800-1000° C., and the holding time of the carbon-embedded sintering is 3-5 h.

5. A carbon ceramic composite conductive microsphere, characterized in that: The carbon-ceramic composite conductive microspheres are prepared by the preparation method of any one of claims 1 to 4, wherein the carbon-ceramic composite conductive microspheres include ceramic phase porous mullite and conductive phase carbon contained within the ceramic phase porous mullite; the diameter of the carbon-ceramic composite conductive microspheres is 80-90 μm.

6. A method for preparing a ceramic resistor, characterized in that: The following steps are involved: The slurry consisting of conductive filler and binder is impregnated into the mud consisting of ceramic raw material and surfactant by vacuum-assisted centrifugal impregnation, followed by drying and binder removal, isostatic pressing and gas pressure sintering. After cooling to room temperature, mechanical treatment is performed and electrodes are sprayed to obtain a ceramic resistor. The conductive filler is a carbon ceramic composite conductive microsphere prepared by the preparation method of carbon ceramic composite conductive microspheres according to any one of claims 1 to 4.

7. The method for preparing a ceramic resistor according to claim 6, wherein: The mass percentages of the conductive filler, binder, ceramic raw material and surfactant are (5%-9%): (0.5%-1.5%): 1: (0.5%-1.5%); Wherein, the ceramic raw materials include, by mass percentage, 63%-67% bauxite, 6%-8% silica powder, 17%-19% kaolin and 8%-12% raw clay; The binder is polyvinyl alcohol; The surfactant is lecithin.

8. The method for preparing a ceramic resistor according to claim 6, wherein: The vacuum degree of the vacuum-assisted centrifugal impregnation method is maintained at 0.3 atm, the rotation speed is 300-600 rpm, and the impregnation time is 2-6 h; The drying temperature is 60-100° C. and the drying time is 18-36 h.

9. The method for preparing a ceramic resistor according to claim 6, wherein: The pressure of the primary isostatic pressing is 200-300 MPa; The sintering temperature of the gas pressure sintering is 1300-1400° C., and the holding time is 2-4 h.

10. A ceramic resistor, characterized in that: Prepared by the preparation method of any one of claims 6 to 9, the ceramic resistor has a volume density of ≥2.25 g / cm 3 .

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