A ceramic slurry with high-dispersed conductive carbon black, a ceramic resistor and a preparation method thereof

Abstract

This invention belongs to the field of electronic materials technology and discloses a ceramic slurry for efficiently dispersing conductive carbon black, a ceramic resistor, and its preparation method. The ceramic slurry comprises ceramic powder, conductive carbon, a mixed solvent, dispersant A, dispersant B, binder, plasticizer, and defoamer. It is prepared using the following steps: S1 premixing and primary stabilization, S2 high-energy dispersion, S3 interface compatibility treatment, and S4 final blending. The ceramic slurry is then spray-granulated, dry-pressed, debinded, and sintered to obtain the ceramic resistor. This invention achieves efficient physical deagglomeration of carbon black through high-pressure microjets and chemical stabilization and interface strengthening with the ceramic matrix through stepwise addition of functionalized dispersants. Ultimately, it significantly improves and optimizes the electrical properties of the ceramic resistor on a macroscopic scale, resulting in advantages such as good resistance consistency, significantly reduced temperature coefficient of resistance, excellent energy absorption capacity, and superior reliability.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, specifically relating to a ceramic slurry for efficiently dispersing conductive carbon black, a ceramic resistor, and a method for preparing the same. Background Technology

[0002] Conductive carbon black is widely used in the preparation of various conductive composite materials due to its excellent conductivity, chemical stability, and relatively low cost, especially as a key conductive phase material in ceramic resistors. The dispersion effect of conductive carbon black directly determines its uniformity of distribution in the ceramic matrix, the quality of the conductive network formation, and ultimately affects the resistivity, temperature coefficient of resistance (TCR), energy absorption performance, and long-term stability of the ceramic resistor.

[0003] Currently, the dispersion of conductive carbon black mainly relies on physical grinding (such as ball milling and sand milling) and the addition of dispersants. Traditional ball milling is inefficient and energy-intensive, and prolonged grinding may damage the carbon black structure or introduce impurities. Conventional dispersants may decompose during subsequent high-temperature sintering, generating gases or leaving residual impurities, affecting the density and electrical properties of ceramic resistors. Especially in ceramic slurry systems with high solid content and high viscosity, achieving uniform and stable dispersion of conductive carbon black while ensuring good compatibility with ceramic powders, glass powders, and other components remains a key technical challenge in the industry. Summary of the Invention

[0004] This invention aims to overcome the technical problems in the prior art, such as uneven dispersion, easy agglomeration, and poor interfacial compatibility of conductive carbon black in ceramic matrix, and the resulting unstable ceramic resistance performance, poor consistency, and high temperature coefficient of resistance (TCR). It provides a ceramic slurry for efficiently dispersing conductive carbon black, a ceramic resistor, and a method for preparing the same. The invention prepares a ceramic slurry through an efficient, stable, and scalable conductive carbon black dispersion method, and further prepares a high-performance ceramic resistor.

[0005] This invention provides the following technical solution: In a first aspect, the present invention provides a ceramic slurry for efficiently dispersing conductive carbon black, which is prepared by the following components and steps: The amounts of each component are based on 100 parts by weight of ceramic powder: conductive carbon black 2.0-5.0 parts by weight, mixed solvent 80-200 parts by weight, dispersant A 0.1-0.5 parts by weight, dispersant B 0.5-2.0 parts by weight, binder 3-8 parts by weight, plasticizer 1-3 parts by weight, and defoamer 0.2-0.8 parts by weight; S1. Premixing and Primary Stabilization: Conductive carbon black, mixed solvent, and dispersant A are added to a high-speed stirring device and stirred at 1000-3000 rpm for 5-15 minutes to form a primary slurry; the mixed solvent is deionized water, ethanol, isopropanol, or a mixture thereof; the dispersant A is a polymer containing carboxyl, phosphate, or amino functional groups, and its amount is 0.5%-5.0% of the mass of the conductive carbon black; S2. High-energy dispersion: The primary slurry obtained in step S1 is transferred to a high-pressure micro-jet homogenizer and circulated 2-5 times under a pressure of 80-150MPa to obtain a homogenized slurry; S3. Interface compatibility treatment: Add ceramic powder and dispersant B to the homogeneous slurry treated in step S2, and disperse for 10-30 minutes under ultrasonic assistance; the ceramic powder is one or more of alumina, kaolin, silica, zirconium oxide or barium titanate, with an average particle size of 0.5-5.0 μm; the dispersant B is a silane coupling agent or a titanate coupling agent, and its amount is 0.5%-2.0% of the mass of the ceramic powder, to obtain a dispersion slurry; S4. Final preparation: Add binder and plasticizer to the dispersion slurry treated in step S3 in proportion, and mix in a planetary mixer at a speed of 500-1000 rpm for 1-2 hours to obtain conductive ceramic slurry.

[0006] In a second aspect, the present invention provides a ceramic resistor prepared using the aforementioned conductive ceramic paste.

[0007] A third aspect of the present invention provides a method for preparing the ceramic resistor, comprising the following steps performed sequentially: (1) Spray granulation: The conductive ceramic slurry is spray-dried to obtain granulated powder; the preferred granulation parameters are: inlet air temperature 160-200°C, outlet air temperature 70-85°C, and atomizing disc rotation speed 12000-18000 rpm. (2) Dry pressing: The granulated powder is filled into a mold and pressed under a pressure of 10-30 MPa to obtain a green body with a predetermined shape and size; (3) Debinding and sintering: The green body is slowly heated to 350-500°C in air at a rate of 0.5-2°C / min and held at that temperature to completely remove organic matter. Then, under an inert or protective atmosphere (such as nitrogen), the temperature is raised to 1100-1350°C at a rate of 2-8°C / min and held for 60-120 minutes to form a dense ceramic resistive body; (4) Electrode preparation: Electrodes are prepared at both ends of the sintered ceramic resistive body, such as forming ohmic contacts by magnetron sputtering of metallic aluminum.

[0008] The beneficial effects of the present invention include at least the following: 1. High dispersion efficiency and good quality: The conductive ceramic slurry prepared by this invention adopts a combination dispersion technology of high-speed premixing and high-pressure micro-jet, which can quickly and thoroughly break the hard aggregates of conductive carbon black, and the high-pressure shear force is gentle, avoiding structural damage caused by long-term ball milling; the high-speed collision and cavitation effect generated by the micro-jet allows the dispersant to more fully coat the carbon black particles.

[0009] 2. Excellent stability: This conductive ceramic slurry adopts a stepwise, functionalized dispersant addition strategy. Dispersant A (polymer type) is mainly anchored on the carbon black surface to provide steric stabilization; dispersant B (coupling agent type) acts as a bridge between carbon black and ceramic powder, improving the interfacial compatibility between different components and effectively preventing re-agglomeration and phase separation during storage and processing.

[0010] 3. Improved Product Performance: Ceramic resistors prepared using conductive ceramic paste exhibit highly uniform distribution of conductive carbon black within the ceramic matrix, forming a complete and stable conductive network. This results in more precise and controllable resistance values, a lower temperature coefficient of resistance (TCR), improved energy absorption capacity, and superior consistency.

[0011] 4. Strong process adaptability: In the preparation method of this invention, the conductive carbon black in the slurry is highly dispersed at the nanoscale, and a stable interfacial bond is achieved between it and the ceramic powder through a coupling agent. It is easy to combine with the existing carbon ceramic resistor preparation process and is suitable for large-scale production. Attached Figure Description

[0012] Figure 1 This is a cross-sectional scanning electron microscope image of the carbon ceramic resistor of Embodiment 1 of the present invention.

[0013] Figure 2 This is a carbon element distribution diagram corresponding to the cross-section of the carbon ceramic resistor in Embodiment 1 of the present invention.

[0014] Figure 3 This is a cross-sectional scanning electron microscope image of the carbon ceramic resistor of Comparative Example 1 of this invention.

[0015] Figure 4 This is a carbon element distribution diagram corresponding to the cross-section of the carbon ceramic resistor in Comparative Example 1 of this invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Basic Implementation The ceramic slurry for efficiently dispersing conductive carbon black provided by this invention is prepared by the following components and steps: The amounts of each component are based on 100 parts by weight of ceramic powder: conductive carbon black 2.0-5.0 parts by weight, mixed solvent 80-200 parts by weight, dispersant A 0.1-0.5 parts by weight, dispersant B 0.5-2.0 parts by weight, binder 3-8 parts by weight, plasticizer 1-3 parts by weight, and defoamer 0.2-0.8 parts by weight; S1. Premixing and Primary Stabilization: Conductive carbon black, mixed solvent, and dispersant A are added to a high-speed stirring device and stirred at 1000-3000 rpm for 5-15 minutes to form a primary slurry; the mixed solvent is deionized water, ethanol, isopropanol, or a mixture thereof; the dispersant A is a polymer containing carboxyl, phosphate, or amino functional groups, and its amount is 0.5%-5.0% of the mass of the conductive carbon black; S2. High-energy dispersion: The primary slurry obtained in step S1 is transferred to a high-pressure micro-jet homogenizer and circulated 2-5 times under a pressure of 80-150MPa to obtain a homogenized slurry; S3. Interface compatibility treatment: Add ceramic powder and dispersant B to the homogeneous slurry treated in step S2, and disperse for 10-30 minutes under ultrasonic assistance; the ceramic powder is one or more of alumina, kaolin, silica, zirconium oxide or barium titanate, with an average particle size of 0.5-5.0 μm; the dispersant B is a silane coupling agent or a titanate coupling agent, and its amount is 0.5%-2.0% of the mass of the ceramic powder, to obtain a dispersion slurry; S4. Final preparation: Add binder and plasticizer to the dispersion slurry treated in step S3 in proportion, and mix in a planetary mixer at a speed of 500-1000 rpm for 1-2 hours to obtain conductive ceramic slurry.

[0018] A ceramic resistor prepared using the aforementioned conductive ceramic paste.

[0019] The method for preparing the ceramic resistor includes the following steps performed sequentially: (1) Spray granulation: The conductive ceramic slurry is spray-dried to obtain granulated powder; the preferred granulation parameters are: inlet air temperature 160-200°C, outlet air temperature 70-85°C, and atomizing disc rotation speed 12000-18000 rpm. (2) Dry pressing: The granulated powder is filled into a mold and pressed under a pressure of 10-30 MPa to obtain a green body with a predetermined shape and size; (3) Debinding and sintering: The green body is slowly heated to 350-500°C in air at a rate of 0.5-2°C / min and held at that temperature to completely remove organic matter. Then, under an inert or protective atmosphere (such as nitrogen), the temperature is raised to 1100-1350°C at a rate of 2-8°C / min and held for 60-120 minutes to form a dense ceramic resistive body; (4) Electrode preparation: Electrodes are prepared at both ends of the sintered ceramic resistive body, such as forming ohmic contacts by magnetron sputtering of metallic aluminum.

[0020] Example 1 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: (I) Preparation of ceramic slurry for efficient dispersion of conductive carbon black S1. Premixing and Primary Stabilization: Take 5.0 g of conductive carbon black with an average particle size of 30 nm and add it to a mixed solvent consisting of 150 g of deionized water and 30 g of anhydrous ethanol. Add 0.25 g of dispersant A (5.0% of the mass of conductive carbon black), wherein dispersant A is sodium polyacrylate (molecular weight approximately 5000, containing carboxyl functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at a speed of 2000 rpm for 10 minutes to obtain a uniform black primary slurry.

[0021] S2. High-energy physical crushing and deagglomeration: The above primary slurry is transferred to a high-pressure micro-jet homogenizer, the homogenization pressure is set to 120 MPa, and the slurry is circulated 3 times. S3. Interface Compatibility Treatment: 200.0 g of ceramic powder (70% alumina, 30% kaolin) with an average particle size of 2.0 μm was added to the slurry treated in step S2. 1.5 g of dispersant B (1.5% of the ceramic powder mass) was added; dispersant B is a silane coupling agent KH-550 (γ-aminopropyltriethoxysilane). The mixture was placed in an ultrasonic cell disruptor (power: 600W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 20 minutes. During this process, the siloxane groups of dispersant B undergo hydrolytic condensation with the hydroxyl groups on the surface of the alumina powder, while the amino functional groups at its other end interact with the carbon black particles coated by dispersant A, thus forming a "bridge" between them and significantly improving the interfacial compatibility between the carbon black and the ceramic matrix.

[0022] S4. Final preparation of slurry: Add the following to the slurry obtained in step S3 in sequence: 10.0 g ethyl cellulose (binder), 2.0 g dibutyl phthalate (plasticizer) and 0.5 g defoamer. Transfer the entire system to a planetary mixer and mix at 800 rpm for 1.5 hours to ensure that all components are mixed evenly, so as to obtain the final conductive ceramic slurry A with moderate solid content, good fluidity and excellent storage stability.

[0023] (II) Preparation of Ceramic Resistors (1) Slurry spray granulation The prepared conductive ceramic slurry A was transferred to a centrifugal spray drying tower for granulation. The process parameters were as follows: inlet air temperature was set to 180°C, outlet air temperature was controlled at 80°C, and atomizing disc speed was 15000 rpm. After atomization, the solvent in the slurry evaporated rapidly in the hot air, forming spherical or near-spherical granulated powder with good flowability.

[0024] (2) Powder compaction The spray-granulated powder was loaded into a special mold (40mm inner diameter) and pressed using a hydraulic press. The pressing pressure was set to 15MPa, and the holding time was 10 seconds. After demolding, a green body with a certain mechanical strength was obtained. The green body was dense, crack-free, 40mm in diameter, and approximately 12mm thick.

[0025] (3) Blank debinding and sintering Debinding stage: Under air atmosphere, heat to 380°C at a slow rate (1°C / min) and hold at this temperature for 120 minutes. The purpose of this stage is to thoroughly and gradually decompose and remove organic components from the green body, including binders, plasticizers, dispersants, and residual solvents, to avoid cracking or blistering of the green body due to concentrated and rapid decomposition of organic matter.

[0026] Sintering stage: After the binder is removed, switch the sintering furnace atmosphere to a nitrogen (N2) protective atmosphere. Increase the temperature to the preset sintering temperature of 1200°C at a rate of 2.5°C / min, and hold at this temperature for 90 minutes.

[0027] (4) Post-treatment and electrode preparation: After sintering, the ceramic resistive body is cooled to room temperature in the furnace. The sintered ceramic resistive body is sputtered with aluminum to form a good ohmic contact between the metal electrode and the ceramic body.

[0028] The cross-sectional scanning electron microscope image of the carbon ceramic resistor prepared in Example 1 and the corresponding carbon element distribution are shown below. Figure 1-2 .

[0029] Example 2 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: a. Dispersion and slurry preparation of conductive carbon black a1. Take 5.0 g of conductive carbon black with an average particle size of 50 nm and add it to a mixed solvent consisting of 140 g of deionized water and 30 g of anhydrous ethanol. Add 0.2 g of dispersant A (4.0% of the mass of conductive carbon black), wherein dispersant A is sodium polyacrylate (molecular weight approximately 8000, containing carboxyl functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at 2500 rpm for 15 minutes to obtain a uniform black primary slurry.

[0030] a2. Transfer the above primary slurry to a high-pressure micro-jet homogenizer. Set the homogenization pressure to 140 MPa and circulate the slurry 5 times.

[0031] a3. Add 180.0 g of ceramic powder (80% alumina, 20% kaolin) with an average particle size of 1.8 μm to the slurry treated in step a2. Add 2.0 g of dispersant B (1.1% of the ceramic powder mass), wherein dispersant B is a titanate coupling agent NDZ-201 (isopropyltris(dioctylpyrophosphoyloxy)titanate). Place the mixture in an ultrasonic cell disruptor (power: 600W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 30 minutes. During this process, the phosphate ester groups of dispersant B bind to the surface of the ceramic powder, and the other end undergoes ester exchange or complexation with the oxygen-containing functional groups on the carbon black surface, forming a tight chemical bond bridge.

[0032] a4. Add the following to the slurry obtained in step a3 in sequence: 10.0 g polyvinyl butyral (binder), 2.5 g polyethylene glycol (plasticizer), and 0.5 g defoamer. Transfer the entire system to a planetary mixer and mix at 800 rpm for 2.0 hours to obtain the final conductive ceramic slurry B, which has moderate solid content, good fluidity, and excellent storage stability.

[0033] b. Preparation of ceramic resistors b1. Slurry spray granulation: inlet air temperature 190°C, outlet air temperature 85°C, atomizing disc speed 15000 rpm.

[0034] b2. Powder compaction: pressing pressure 20 MPa, holding pressure for 15 seconds, green compact diameter 40 mm, thickness 12 mm.

[0035] b3. Blank debinding and sintering: During the debinding stage, the temperature is increased to 380°C at a rate of 1°C / min and held for 150 minutes; during the sintering stage, the temperature is increased to 1250°C at a rate of 2.5°C / min under nitrogen protection and held for 90 minutes.

[0036] b4. Post-processing: Cool with the furnace and then perform aluminum sputtering to form ohmic contacts.

[0037] Example 3 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: a. Dispersion and slurry preparation of conductive carbon black a1. Take 6.0 g of conductive carbon black with an average particle size of 30 nm and add it to a mixed solvent consisting of 150 g of deionized water and 20 g of isopropanol. Add 0.3 g of dispersant A (5.0% of the mass of conductive carbon black), wherein dispersant A is a polycarboxylic acid ammonium salt (molecular weight approximately 10,000, containing carboxyl and amino functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at 3000 rpm for 10 minutes.

[0038] a2. Transfer the above primary slurry to a high-pressure micro-jet homogenizer. Set the homogenization pressure to 120 MPa and circulate the slurry 4 times.

[0039] a3. Add 180.0 g of ceramic powder (60% alumina, 40% kaolin) with an average particle size of 3.5 μm to the slurry treated in step a2. Add 1.8 g of dispersant B (1.0% of the ceramic powder mass), wherein dispersant B is silane coupling agent KH-560 (γ-glycidoxypropyltrimethoxysilane). Place the mixture in an ultrasonic cell disruptor (power: 600W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 25 minutes. The epoxy groups react with the hydroxyl groups on the alumina surface, and the other end of the silane forms a strong interaction with the carbon black.

[0040] a4. Add the following to the slurry obtained in step a3: 10.0 g ethyl cellulose (binder), 2.0 g dibutyl phthalate (plasticizer), and 0.5 g defoamer. Transfer the entire system to a planetary mixer and mix at 1000 rpm for 2 hours to obtain the final conductive ceramic slurry C.

[0041] b. Preparation of ceramic resistors b1. Slurry spray granulation: inlet air temperature 180°C, outlet air temperature 80°C, atomizing disc speed 15000 rpm.

[0042] b2. Powder compaction: pressing pressure 15 MPa, holding pressure for 10 seconds.

[0043] b3. Blank debinding and sintering: During the debinding stage, the temperature is increased to 350°C at a rate of 1°C / min and held for 120 minutes; during the sintering stage, the temperature is increased to 1300°C at a rate of 2.5°C / min and held for 60 minutes under nitrogen protection.

[0044] b4. Post-processing: After cooling in the furnace, perform aluminum sputtering.

[0045] Example 4 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: a. Dispersion and slurry preparation of conductive carbon black a1. Take 4.0 g of conductive carbon black with an average particle size of 20 nm (equivalent to 2.67 parts by mass of 100 parts by mass of ceramic powder) and add it to a mixed solvent (150 g in total) consisting of 100 g of deionized water and 50 g of anhydrous ethanol. Add 0.02 g of dispersant A (0.5% of the mass of conductive carbon black), wherein dispersant A is a polycarboxylic acid ammonium salt (molecular weight approximately 3000, containing carboxyl functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at 1000 rpm for 5 minutes to obtain a black primary slurry.

[0046] a2. Transfer the above primary slurry to a high-pressure micro-jet homogenizer. Set the homogenization pressure to 80 MPa and circulate the slurry twice.

[0047] a3. Add 150.0 g (100 parts by weight, silica) of ceramic powder with an average particle size of 0.5 μm to the slurry treated in step a2. Add 0.75 g of dispersant B (0.5% of the ceramic powder mass), wherein dispersant B is silane coupling agent KH-550 (γ-aminopropyltriethoxysilane). Place the mixture in an ultrasonic cell disruptor (power: 600 W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 10 minutes. During this process, the siloxane groups of dispersant B undergo hydrolytic condensation with the hydroxyl groups on the surface of the silica powder, while the amino functional groups at its other end interact with the carbon black particles coated by dispersant A, forming a "bridge".

[0048] a4. Add the following to the slurry obtained in step a3 in sequence: 5.0 g ethyl cellulose (binder, equivalent to 3.33 parts by mass), 2.0 g dibutyl phthalate (plasticizer, equivalent to 1.33 parts by mass), and 0.3 g defoamer (equivalent to 0.20 parts by mass). Transfer the entire system to a planetary mixer and mix at 500 rpm for 1 hour to obtain the final conductive ceramic slurry D.

[0049] b. Preparation of ceramic resistors b1. Slurry spray granulation: inlet air temperature 160°C, outlet air temperature 70°C, atomizing disc speed 12000 rpm.

[0050] b2. Powder compaction: The spray-granulated powder is loaded into a mold (mold inner diameter 30 mm) and pressed into shape using a hydraulic press. The pressing pressure is set to 10 MPa, and the holding time is 8 seconds. After demolding, a green compact is obtained with a diameter of 30 mm and a thickness of approximately 10 mm.

[0051] b3. Blank removal and sintering: During the blank removal stage, the temperature is raised to 350°C at a rate of 0.5°C / min under air atmosphere and held for 60 minutes. During the sintering stage, the temperature is switched to nitrogen protective atmosphere, raised to 1100°C at a rate of 2°C / min and held for 120 minutes.

[0052] b4. Post-processing: After cooling to room temperature in the furnace, perform aluminum sputtering to form ohmic contacts.

[0053] Example 5 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: a. Dispersion and slurry preparation of conductive carbon black a1. Take 10.0 g of conductive carbon black with an average particle size of 50 nm (equivalent to 5.0 parts by mass of 100 parts by mass of ceramic powder) and add it to a mixed solvent (200 g in total) consisting of 180 g of deionized water and 20 g of isopropanol. Add 0.5 g of dispersant A (5.0% of the mass of conductive carbon black), wherein dispersant A is sodium polyacrylate (molecular weight approximately 5000, containing carboxyl functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at 3000 rpm for 15 minutes.

[0054] a2. Transfer the above primary slurry to a high-pressure micro-jet homogenizer. Set the homogenization pressure to 150 MPa and circulate the slurry 5 times.

[0055] a3. Add 200.0 g (100 parts by weight, zirconium oxide) of ceramic powder with an average particle size of 5.0 μm to the slurry treated in step a2. Add 4.0 g of dispersant B (2.0% of the ceramic powder mass), wherein dispersant B is a titanate coupling agent NDZ-201 (isopropyltris(dioctylpyrophosphate)titanate). Place the mixture in an ultrasonic cell disruptor (power: 600 W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 30 minutes. During this process, the phosphate ester groups of dispersant B bind to the surface of the zirconium oxide powder, and the other end undergoes ester exchange or complexation with the oxygen-containing functional groups on the carbon black surface, forming a tight chemical bond bridge.

[0056] a4. Add the following to the slurry obtained in step a3 in sequence: 15.0 g polyvinyl butyral (binder, equivalent to 7.5 parts by mass), 5.0 g polyethylene glycol (plasticizer, equivalent to 2.5 parts by mass), and 0.8 g defoamer (equivalent to 0.40 parts by mass). Transfer the entire system to a planetary mixer and mix at 1000 rpm for 2 hours to obtain the final conductive ceramic slurry E.

[0057] b. Preparation of ceramic resistors b1. Slurry spray granulation: inlet air temperature 200°C, outlet air temperature 85°C, atomizing disc speed 18000 rpm.

[0058] b2. Powder compaction: pressing pressure 30 MPa, holding pressure for 20 seconds, green compact diameter 40 mm, thickness 12 mm.

[0059] b3. Blank debinding and sintering: During the debinding stage, the temperature is increased to 500°C at 2°C / min and held for 150 minutes; during the sintering stage, the temperature is increased to 1350°C at 8°C / min under nitrogen protection and held for 60 minutes.

[0060] b4. Post-processing: Cool with the furnace and then perform aluminum sputtering to form ohmic contacts.

[0061] Example 6 The ceramic slurry, ceramic resistor, and preparation method for the highly efficient dispersed conductive carbon black provided in this embodiment are based on the basic embodiment with specific selections. The difference lies in: a. Dispersion and slurry preparation of conductive carbon black a1. Take 6.0 g of conductive carbon black with an average particle size of 40 nm (equivalent to 3.33 parts by mass of 100 parts by mass of ceramic powder) and add it to a mixed solvent (150 g in total) consisting of 120 g of deionized water and 30 g of anhydrous ethanol. Add 0.18 g of dispersant A (3.0% of the mass of conductive carbon black), wherein dispersant A is a polycarboxylic acid ammonium salt (molecular weight approximately 10,000, containing carboxyl and amino functional groups). Place the above mixture in a high-speed disperser and pre-disperse it at 2000 rpm for 12 minutes.

[0062] a2. Transfer the above primary slurry to a high-pressure micro-jet homogenizer. Set the homogenization pressure to 100 MPa and circulate the slurry three times.

[0063] a3. Add 180.0 g (100 parts by weight, barium titanate) of ceramic powder with an average particle size of 1.0 μm to the slurry treated in step a2. Add 2.7 g of dispersant B (1.5% of the ceramic powder mass), wherein dispersant B is silane coupling agent KH-560 (γ-glycidoxypropyltrimethoxysilane). Place the mixture in an ultrasonic cell disruptor (power: 600 W, operating mode: ultrasonic for 2 seconds, interval for 1 second) for assisted dispersion for 20 minutes. The epoxy groups react with the surface of barium titanate, and the other end of the silane forms a strong interaction with carbon black.

[0064] a4. Add the following to the slurry obtained in step a3 in sequence: 10.0 g ethyl cellulose (binder, equivalent to 5.56 parts by mass), 3.0 g dibutyl phthalate (plasticizer, equivalent to 1.67 parts by mass), and 0.5 g defoamer (equivalent to 0.28 parts by mass). Transfer the entire system to a planetary mixer and mix at 800 rpm for 1.5 hours to obtain the final conductive ceramic slurry F.

[0065] b. Preparation of ceramic resistors b1. Slurry spray granulation: inlet air temperature 180°C, outlet air temperature 80°C, atomizing disc speed 15000 rpm.

[0066] b2. Powder compaction: pressing pressure 15 MPa, holding pressure for 10 seconds, green compact diameter 40 mm, thickness 12 mm.

[0067] b3. Blank debinding and sintering: During the debinding stage, the temperature is increased to 380°C at a rate of 1°C / min and held for 120 minutes; during the sintering stage, the temperature is increased to 1250°C at a rate of 2.5°C / min under nitrogen protection and held for 90 minutes.

[0068] b4. Post-processing: Cool with the furnace and then perform aluminum sputtering to form ohmic contacts.

[0069] Comparative Example 1 a. Slurry preparation (traditional ball milling method) 5.0 g of conductive carbon black with an average particle size of 30 nm and 180.0 g of ceramic powder (70% alumina, 30% kaolin) with an average particle size of 2.0 μm were added to a stirred ball mill jar along with 150 g of deionized water, 30 g of ethanol, 0.2 g of sodium polyacrylate, 10.0 g of ethyl cellulose, 2.0 g of dibutyl phthalate, and 0.5 g of defoamer. Zirconia grinding balls (3:1 ball-to-powder ratio) were added, and the mixture was ball-milled at 300 rpm for 24 hours. The resulting slurry was used directly in subsequent steps without high-pressure microfluidic treatment.

[0070] b. Preparation of ceramic resistors The subsequent steps (spray granulation, compaction, sintering, and post-treatment) were exactly the same as in Example 1 (b1-b4), and comparative sample D was prepared.

[0071] Comparative Example 2 a. Slurry preparation (without compatibilization treatment) a1-a2. The steps are the same as in Example 1.

[0072] a3. Add 180.0 g of ceramic powder directly to the slurry treated above, without adding dispersant B. Mix in a planetary mixer (800 rpm) for 1.5 hours to mechanically mix the powder with the slurry.

[0073] a4. The steps are the same as in Example 1.

[0074] b. Preparation of ceramic resistors The subsequent steps (spray granulation, compaction, sintering, and post-treatment) were exactly the same as in Example 1 (b1-b4), and comparative sample E was prepared.

[0075] Electrical performance testing and comparative analysis Key electrical properties of the ceramic resistive bodies prepared in Examples 1-6 (samples A, B, and C) and Comparative Examples 1-2 (samples D and E) were tested. All samples were tested under the same conditions (room temperature 25°C, humidity <30% RH) after end electrode treatment (metallization), and the results are summarized in Table 1 below.

[0076] Table 1

[0077] (1) Conductivity uniformity and consistency: The samples prepared using the method of this invention (Examples 1-6) showed stable sheet resistance and significantly lower intra-batch dispersion coefficient (<5%) than the two comparative examples. This indicates that the high-pressure micro-jet crushing + stepwise compatibility process effectively achieved highly uniform and stable dispersion of conductive carbon black in the ceramic matrix, ensuring the consistency of product performance. Comparative Example 1 used traditional ball milling, which resulted in incomplete dispersion and easy introduction of contamination, leading to severe carbon black agglomeration and high resistance dispersion. Comparative Example 2 lacked the bridging effect of coupling agent, resulting in poor compatibility between carbon black and ceramic interface, which easily led to slight phase separation during subsequent processing, resulting in decreased consistency.

[0078] (2) Temperature Coefficient of Resistance (TCR): The absolute TCR value of the sample of this invention (<200 ppm / °C) is much lower than that of the comparative example. TCR is a key indicator for measuring the stability of resistance value with temperature change. The lower TCR is due to the perfect and stable three-dimensional conductive network. In the embodiments, the uniformly dispersed carbon black forms numerous parallel conductive paths, and the changes in local paths affected by temperature compensate for each other on a macroscopic level, making the overall resistance more stable. Comparative Examples 1 and 2 have imperfect conductive networks and weak points due to agglomeration or phase separation, and their resistance values ​​are more sensitive to temperature, so their absolute TCR values ​​are higher.

[0079] (3) Pulse power tolerance and reliability: In the 2ms square wave high current absorption capacity test, the resistor of the present invention exhibited excellent stability and reliability. This is because the uniformly dispersed structure makes the current and heat distribution more uniform, avoiding performance degradation caused by local overheating. Comparative Example 1, due to the presence of large agglomerates, is prone to becoming hot spots under pulse current, resulting in large resistance value drift or even open circuit failure. Comparative Example 2, due to weak interface bonding, is prone to microcracks under thermal stress, leading to performance degradation.

[0080] The test results of the above embodiments prove that the dispersion and preparation method provided by the present invention achieves efficient physical deagglomeration of carbon black through high-pressure microjets, and achieves chemical stabilization of carbon black and interface strengthening with ceramic matrix through stepwise addition of functionalized dispersants. Finally, it achieves significant improvement and optimization of ceramic resistivity on a macroscopic level, especially in terms of high consistency, low TCR and high reliability.

[0081] The above embodiments of the present invention focus on addressing the problems of easy agglomeration, uneven dispersion, and poor interfacial compatibility of conductive carbon black in ceramic slurries. A novel strategy combining stepwise functionalized dispersion and high-energy combined treatment is proposed. This method includes: first, premixing and initially stabilizing conductive carbon black with a polymeric dispersant A containing strong adsorption functional groups; then, using a high-pressure microfluidic homogenizer for high-energy physical crushing; subsequently, adding ceramic powder and a coupling agent-type dispersant B, and constructing "molecular bridges" between the carbon black and ceramic powder using ultrasonic assistance to achieve interfacial compatibility treatment; finally, preparing a conductive ceramic slurry. This slurry is then spray-granulated, dry-pressed, debinded, and sintered to obtain a ceramic resistor. Compared to traditional processes, the embodiments of the present invention can effectively achieve nanoscale uniform dispersion of carbon black, and the resulting ceramic resistors have advantages such as good resistance consistency, significantly reduced temperature coefficient of resistance, excellent energy absorption capacity, and superior reliability.

[0082] It should be noted that, within the range of material ratios, preparation steps, and process parameters described in this invention, other specific values ​​can be selected independently, and the resulting materials will all achieve the technical effects described in this invention. Therefore, this invention will not list them all.

[0083] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any technical features that are the same as or similar to those in the above embodiments of the present invention are within the protection scope of the present invention.

Claims

1. A ceramic slurry for efficiently dispersing conductive carbon black, characterized in that, It is prepared from the following components and steps: The amounts of each component are based on 100 parts by weight of ceramic powder: conductive carbon black 2.0-5.0, mixed solvent 80-200, dispersant A 0.1-0.5, dispersant B 0.5-2.0, binder 3-8, plasticizer 1-3, defoamer 0.2-0.8; S1. Premixing and Primary Stabilization: Conductive carbon black, mixed solvent, and dispersant A are added to a high-speed stirring device and stirred at 1000-3000 rpm for 5-15 minutes to form a primary slurry; the mixed solvent is deionized water, ethanol, isopropanol, or a mixture thereof; the dispersant A is a polymer containing carboxyl, phosphate, or amino functional groups, and its amount is 0.5%-5.0% of the mass of the conductive carbon black; S2. High-energy dispersion: The primary slurry obtained in step S1 is transferred to a high-pressure micro-jet homogenizer and circulated 2-5 times under a pressure of 80-150 MPa to obtain a homogenized slurry; S3. Interface compatibility treatment: Add ceramic powder and dispersant B to the homogeneous slurry treated in step S2, and disperse for 10-30 minutes under ultrasonic assistance; the ceramic powder is one or more of alumina, kaolin, silica, zirconium oxide or barium titanate, with an average particle size of 0.5-5.0 μm; the dispersant B is a silane coupling agent or a titanate coupling agent, and its amount is 0.5%-2.0% of the mass of the ceramic powder, to obtain a dispersion slurry; S4. Final preparation: Add binder and plasticizer to the dispersion slurry treated in step S3 in proportion, and mix in a planetary mixer at a speed of 500-1000 rpm for 1-2 hours to obtain conductive ceramic slurry.

2. The method according to claim 1, characterized in that, In step S1, the average particle size of the conductive carbon black is 20-50 nm; the dispersant A is sodium polyacrylate or ammonium polycarboxylate; and the amount of dispersant A is 1%-3% of the mass of the conductive carbon black.

3. The method according to claim 1, characterized in that, In step S1, the high-speed stirring device rotates at 2000-3000 rpm and the stirring time is 10-15 minutes.

4. The method according to claim 1, characterized in that, In step S2, the processing pressure of the high-pressure micro-jet homogenizer is 100-140 MPa, and the number of cycles is 3-5.

5. The method according to claim 1, characterized in that, In step S3, the ceramic powder is one or more of alumina, kaolin, silica, zirconium oxide, or barium titanate, with an average particle size of 0.5-5.0 μm; the dispersant B is silane coupling agent KH-550, KH-560, or titanate coupling agent NDZ-201.

6. The method according to claim 1, characterized in that, In step S4, the binder is ethyl cellulose; the plasticizer is dibutyl phthalate; the planetary mixer rotates at 800-1000 rpm and the mixing time is 1.5-2 hours.

7. A ceramic resistor, characterized in that, It is prepared using the conductive ceramic paste described in any one of claims 1-6.

8. A method for preparing the ceramic resistor according to claim 7, characterized in that, It includes the following steps performed sequentially: (1) Spray granulation: The conductive ceramic slurry is spray-dried to obtain granulated powder; (2) Dry pressing: pressing the granulated powder into a green body; (3) Debinding and sintering: The green body is subjected to debinding and sintering in sequence to obtain ceramic resistive body; (4) Electrode preparation: Electrode preparation is performed on the ceramic resistive body.

9. The preparation method according to claim 8, characterized in that, In step (1), the process parameters for spray drying are: inlet air temperature 160-200°C, outlet air temperature 70-85°C, and atomizing disc rotation speed 12000-18000 rpm; in step (2), the pressure for dry pressing is 10-30 MPa.

10. The preparation method according to claim 8, characterized in that, In step (3), the debinding process is carried out in an air atmosphere, with a heating rate of 0.5-2°C / min to 350-500°C and held at that temperature; the sintering process is carried out in a protective atmosphere or an inert atmosphere, with a heating rate of 2-8°C / min to 1100-1350°C and held at that temperature for 60-120 minutes.

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