Carbon ceramic resistor material and method for making same

Abstract

The application discloses a carbon ceramic resistance material and a preparation method thereof. The ceramic resistance material is composed of conductive carbon black and a ceramic matrix, and the conductive carbon black forms a continuous three-dimensional conductive network in the ceramic matrix; the carbon ceramic resistance material has a resistivity of 1.14 Omega*m to 2.40 Omega*m at room temperature, and a resistance temperature coefficient of 0 to -0.15% / DEG C. The material not only significantly reduces the high resistance characteristics of traditional ceramic resistance, but also considers long-term reliability, and solves the technical problems of poor conductivity and unstable performance in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of ceramic resistance materials technology, and relates to a carbon ceramic resistance material and its preparation method. Background Technology

[0002] Carbon ceramic linear resistors are an important type of functional composite material, mainly made by mixing and molding conductive carbon phases (such as carbon black and graphite) and insulating ceramic matrices (such as alumina, mullite, and clay) and then sintering at high temperatures. Due to their excellent energy absorption capacity, stable resistance characteristics, and good thermal shock resistance, these materials are widely used as core components of the closing resistors in circuit breakers of high-voltage power transmission and transformation equipment, playing a crucial role in limiting operational overvoltages and ensuring the safe operation of power systems.

[0003] The electrical properties of carbon ceramic linear resistors are strongly dependent on the formation and stability of their internal conductive network. According to percolation theory, only when conductive carbon black particles form uniform and continuous three-dimensional conductive pathways within an insulating ceramic matrix can the composite material exhibit stable linear resistance characteristics and a low temperature coefficient of resistance. However, conductive carbon black, as a nanoscale functional filler, is characterized by its small particle size, large specific surface area, and high surface energy. During mixing and sintering, it readily agglomerates to form micron-sized secondary particles. This agglomeration effect leads to uneven distribution of carbon black within the ceramic matrix. On the one hand, it disrupts the integrity and uniformity of the conductive pathways, resulting in large resistance value dispersion and poor performance consistency. On the other hand, the agglomerates also hinder the densification sintering of the ceramic matrix, leading to increased porosity and decreased mechanical strength.

[0004] To address the aforementioned technical challenges, researchers both domestically and internationally have explored various process approaches. Early methods primarily employed dry mixing, but this approach struggled to achieve uniform dispersion of nano-carbon black, resulting in green bodies with low strength and poor reproducibility. In recent years, wet mixing has gradually become the mainstream method. Studies have shown that a stepwise mixing method, where carbon black and dispersant are pre-ball-milled and dispersed before being mixed with ceramic raw materials, is beneficial for reducing the dispersion of resistivity. Regarding the selection of dispersants, existing literature reports the use of polyvinylpyrrolidone (PVP) to disperse carbon black, which can reduce the size of carbon black agglomerates. However, microscopic observation after sintering shows that carbon black still largely exists in submicron-sized agglomerates. Furthermore, research on carbon nanotube-reinforced ceramic composites has revealed that while physical ball milling can achieve a certain degree of dispersion, it often leads to a decrease in conductivity due to damage to the original structure of the conductive filler or uneven dispersion. Adding surfactants to regulate the network structure of the conductive phase in the slurry is considered an effective strategy for improving the electrical properties of composite materials.

[0005] Although existing technologies have made some progress in carbon black dispersion, there are still significant shortcomings: First, single dispersion methods, such as using only one dispersant or performing a single ball milling, have limited ability to deagglomerate carbon black agglomerates, making it difficult to achieve ideal primary particle-scale dispersion in ceramic matrices; Second, the stability of the dispersed slurry system is insufficient, making it prone to re-agglomeration in subsequent processes; Third, traditional sintering processes fail to fully consider the synergistic relationship between the removal of residual organic matter and dispersants and the solidification of conductive networks, resulting in uneven carbon black distribution and imperfect conductive pathway construction in the sintered body, which in turn affects the temperature coefficient of resistance and electrical performance stability of the resistive material.

[0006] Therefore, developing a new method that can significantly improve the uniformity of conductive carbon black dispersion in a ceramic matrix is ​​of great significance for improving the overall performance and large-scale production of carbon ceramic linear resistors. Summary of the Invention

[0007] To overcome the aforementioned problems, this invention proposes a carbon ceramic resistive material and its preparation method. The ceramic resistive material is composed of conductive carbon black and a ceramic matrix, with the conductive carbon black forming a continuous three-dimensional conductive network within the ceramic matrix. The resistivity of the carbon ceramic resistive material at room temperature is 1.14 Ω·m to 2.40 Ω·m, and its temperature coefficient of resistance is 0 to -0.15% / ℃. This material not only significantly reduces the high resistance characteristics of traditional ceramic resistors but also ensures long-term reliability, solving the technical problems of poor conductivity and unstable performance in existing technologies. The preparation process of this invention is simple and low-cost, applicable to fields such as electronic components and power system protection devices, and has broad market application prospects.

[0008] Specifically, the object of the present invention is to provide the following aspects:

[0009] In a first aspect, a carbon ceramic resistive material is provided, wherein the carbon ceramic resistive material is composed of conductive carbon black and a ceramic matrix, and the conductive carbon black forms a continuous three-dimensional conductive network in the ceramic matrix; the resistivity of the carbon ceramic resistive material at room temperature is 1.14 Ω·m to 2.40 Ω·m, and the temperature coefficient of resistance is 0 to -0.15% / ℃.

[0010] On the other hand, a method for preparing the carbon ceramic resistive material described in the first aspect is provided, the method comprising:

[0011] Step 1: The conductive carbon black is mixed with the first dispersant and ball-milled once to obtain a pre-dispersed slurry;

[0012] Step 2: Add ceramic raw materials to the pre-dispersed slurry and then ball mill it twice to obtain a composite slurry;

[0013] Step 3: Add a second dispersant to the composite slurry and ball mill three times to obtain a stable slurry;

[0014] Step 4: The stabilized slurry is pretreated and then sintered to obtain the carbon ceramic resistive material.

[0015] The beneficial effects of this invention include:

[0016] (1) The carbon ceramic resistive material provided by the present invention significantly reduces the resistivity and temperature coefficient of resistance of the material by introducing conductive carbon black into the ceramic matrix and constructing a continuous conductive network. At the same time, it improves the environmental stability. The uniform conductive network means that the current transmission path is more consistent, reducing the risk of local overheating and resistance drift, thereby improving the service reliability of the material under high voltage and high current conditions.

[0017] (2) The method for preparing carbon ceramic resistive materials provided by the present invention achieves highly uniform dispersion of conductive carbon black in the ceramic matrix through the stepwise addition of dispersant and three-stage distributed ball milling, and avoids the problems of poor dispersion effect or poor slurry stability caused by the functional combination of a single process. In particular, the staged sintering method densifies the ceramic matrix while guiding the conductive carbon black to build a stable and continuous three-dimensional conductive network on the basis of the already formed uniform distribution, avoiding the secondary agglomeration of carbon black or the breakage of conductive pathways caused by improper heating rate in traditional sintering processes. Attached Figure Description

[0018] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0019] In the attached diagram:

[0020] Figure 1 A schematic diagram of the process for preparing a carbon ceramic linear resistor according to a preferred embodiment of the present invention is shown;

[0021] Figure 2(a) shows the microstructure of the carbon ceramic resistive material prepared in Example 1;

[0022] Figure 2(b) shows the internal carbon element distribution of the carbon ceramic resistive material prepared in Example 1;

[0023] Figure 3(a) shows the carbon element distribution of the carbon ceramic resistive material prepared in Example 1;

[0024] Figure 3(b) shows the carbon element distribution of the carbon ceramic resistive material prepared in Comparative Example 1.

[0025] Figure 4 The temperature coefficient of resistance of the carbon ceramic linear resistors prepared in Examples 1 and 3 is shown.

[0026] Figure 5 The diagram shows the sintering curve changes during the preparation of carbon ceramic linear resistors in Example 1. Detailed Implementation

[0027] The following will refer to the appendix. Figures 1 to 5 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0028] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0029] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0031] On one hand, according to the present invention, a carbon ceramic resistive material is composed of conductive carbon black and a ceramic matrix, wherein the conductive carbon black forms a continuous conductive network in the ceramic matrix; the resistivity of the carbon ceramic resistive material at room temperature is 1.14 Ω·m to 2.40 Ω·m, and the temperature coefficient of resistance is 0 to -0.15% / ℃.

[0032] According to a preferred embodiment, the ceramic matrix includes at least alumina, silicon dioxide, kyanite, and albite.

[0033] Alumina serves as the main crystalline framework, providing high insulation, excellent mechanical strength, and high-temperature stability. During sintering, alumina and silica react to form mullite, which together constitutes a rigid support network for the carbon ceramic resistive material. This effectively constrains the migration of conductive carbon black particles during sintering, laying the physical foundation for constructing a stable conductive pathway. During sintering, albite reacts to form a low-viscosity silicate glass phase, promoting ceramic rearrangement and densification. However, its content and viscosity are precisely controlled to both assist in green body shrinkage and prevent excessive encapsulation of conductive carbon black particles, thus ensuring the integrity of the conductive carbon black dispersion and preventing it from being isolated by the insulating liquid phase and damaging the conductive network. Kyanite provides an in-situ expansion compensation effect; it undergoes irreversible decomposition at high temperatures, transforming into mullite with accompanying volume expansion. This characteristic is cleverly used to counteract the overall shrinkage of the ceramic matrix during densification and effectively alleviate the problem of secondary agglomeration of conductive carbon black caused by shrinkage stress.

[0034] Furthermore, based on the total mass of the carbon ceramic resistive material as 100%, it comprises: 7wt%~10wt% conductive carbon black, 50wt%~55wt% alumina, 20wt%~25wt% silicon oxide, 4wt% kyanite, and 3wt%~8wt% albite; the alumina content in the kyanite is 54~58wt%, and the silicon oxide content in the albite is 66~68wt%. This formulation, deeply coupled with the three-stage ball milling and sintering process in the method, is a necessary condition for obtaining excellent performance.

[0035] In a second aspect, according to the method for preparing the carbon ceramic resistive material described in the first aspect of the present invention, the method includes:

[0036] Step 1: The conductive carbon black is mixed with the first dispersant and ball-milled once to obtain a pre-dispersed slurry;

[0037] Step 2: Add ceramic raw materials to the pre-dispersed slurry and then ball mill it twice to obtain a composite slurry;

[0038] Step 3: Add a second dispersant to the composite slurry and ball mill three times to obtain a stable slurry;

[0039] Step 4: The stabilized slurry is pretreated and then sintered to obtain the carbon ceramic resistive material.

[0040] The above methods will be described in detail below.

[0041] Step 1: Mix conductive carbon black with the first dispersant and ball mill once to obtain a pre-dispersed slurry.

[0042] In step 1, the conductive carbon black has a purity of 99.9% or higher and a particle size of 4-6 μm. High-purity conductive carbon black can effectively prevent metallic impurities such as Fe, Cu, and ash from catalyzing the oxidation of carbon black or forming non-uniform conductive microchannels during sintering, thereby ensuring the stability of the resistance value and the controllability of the resistance temperature coefficient. The particle size of 4-6 μm falls within the submicron to micron transition range, possessing both a low specific surface area and a suitable size. This significantly weakens the strong agglomeration tendency of nano-carbon black caused by its high surface energy, while also being sufficient to achieve uniform distribution in the ceramic matrix and support the electron tunneling conductivity mechanism.

[0043] In step 1, the first dispersant is preferably an aqueous solution of polyvinylpyrrolidone (PVP) with a concentration of 8-12 wt%, for example, 10 wt%. The pyrrolidone ring (C=O) in the PVP molecular chain adsorbs onto the oxygen-containing functional groups on the surface of conductive carbon black via hydrogen bonds. Simultaneously, the long carbon chain provides efficient steric hindrance, synergistically inhibiting agglomeration. Its good water solubility facilitates the construction of water-based slurry systems, and its thermal decomposition temperature range closely matches the subsequent low-temperature sintering stage, ensuring complete removal without damaging the conductive carbon black structure and preventing residues from interfering with the conductive network. Experiments show that when the PVP concentration is below 8 wt%, the dispersion effect is poor; above 12 wt%, the pre-dispersed slurry viscosity is too high, weakening the ball mill shearing efficiency and increasing the burden of low-temperature degreasing; while a concentration of 8-12 wt% achieves optimal dispersion uniformity.

[0044] In step 1, the ball milling speed is 300~500 r / min, preferably 350~450 r / min, for example 400 r / min. The constraint for setting this parameter is that too low a speed is insufficient to overcome the van der Waals forces between conductive carbon black agglomerates; too high a speed easily leads to excessive breakage of the conductive carbon black, generating highly active nano-fragments, which in turn causes re-agglomeration. Within the range of 350~450 r / min, the entire process of wetting, exfoliation, and initial stabilization can be efficiently achieved.

[0045] Furthermore, the ball milling time is 0.5~2h, preferably 1~1.5h, for example 1h. The constraint for setting this parameter is: if it is less than 0.5h, the deagglomeration is insufficient; if it is more than 2h, it enters the over-milling stage, and the dispersed particles undergo secondary agglomeration due to the increase in local concentration, and the energy consumption increases linearly while the benefits decrease.

[0046] Crucially, in step 1, the PVP aqueous solution itself is used as the ball milling medium. The aqueous environment promotes rapid diffusion of PVP and dynamic coating of the conductive carbon black surface; the ball milling shear force simultaneously enhances the adsorption and depolymerization effects; the deionized water medium is free from ion interference, environmentally friendly and safe, and highly compatible with subsequent drying and sintering processes. This design avoids the uneven adsorption problem caused by the traditional method of static adsorption followed by ball milling, and is a core element in ensuring the initial dispersion quality of the conductive carbon black.

[0047] Step 2: Add ceramic raw materials to the pre-dispersed slurry and obtain a composite slurry by ball milling twice.

[0048] In step 2, the ceramic raw materials include at least alumina, silicon dioxide, kyanite, and albite.

[0049] The alumina has a purity of 99.9% or higher and a particle size of 1-3 μm. As the main crystalline framework, alumina needs high purity to avoid introducing additional conductive pathways or reducing insulation performance. Its particle size is controlled at 1-3 μm to match the size of conductive carbon black. If the alumina is too fine, it can lead to excessively high viscosity in the composite slurry, increased sedimentation, and easy encapsulation by the liquid phase during sintering, weakening the framework's supporting effect; if it is too coarse, it will be difficult to form a tight contact interface with the conductive carbon black, affecting electron transport efficiency.

[0050] The silica has a purity of ≥99.9% and a particle size of 4~6μm. As a precursor for liquid phase formation, silica's purity ≥99.9% ensures the absence of alkali metal impurities interfering with mullite phase formation. Larger silica particles fill the gaps in the alumina, increasing the packing density; simultaneously, they prevent excessively fine silica from causing premature or excessive local liquid phase formation, which could encapsulate conductive carbon black and disrupt the conductive network. This design allows silica to synergistically form a low-viscosity liquid phase with albite during sintering, only aiding densification without disrupting the established conductive carbon black dispersion structure.

[0051] In step 2, the ball milling medium is preferably water, more preferably deionized water. Water is a polar medium, which is beneficial for the stable existence of the first dispersant, such as the PVP coating layer, and promotes hydroxylation of the ceramic powder surface, enhancing the wetting affinity with the first dispersant and conductive carbon black. Secondly, the water is consistent with the aqueous solution system of the first dispersant in step 1, avoiding compatibility problems or sintering cracking risks caused by the introduction of organic solvents. In particular, deionized water can minimize the shielding effect of divalent ions such as calcium and magnesium ions on the adsorption behavior of the first dispersant, such as PVP, ensuring long-term stability.

[0052] Furthermore, the mass ratio of secondary milling media to ceramic raw materials is 1:(0.8-1.2), preferably 1:1. The constraints for setting this parameter are: if there is too little secondary milling media, the solid content of the composite slurry is too high, the viscosity rises sharply, and the milling shear force cannot be effectively transmitted to the particle interface, resulting in uneven mixing and local agglomeration; if there is too much secondary milling media, the solid content is too low, the particle collision frequency decreases, and the dispersion efficiency is reduced.

[0053] In step 2, the secondary ball milling speed is 300~500 r / min, preferably 350~450 r / min, for example 400 r / min. The constraint for setting this parameter is that, compared to the focusing on depolymerization of conductive carbon black in step 1, step 2 requires thorough mixing of the dispersed conductive carbon black with the ceramic raw material. If the rotation speed is too low, large ceramic particles such as kyanite and albite are difficult to disperse effectively; if the rotation speed is too high, ceramic particles are easily broken into fine powder, which in turn adsorbs more of the primary dispersant, weakening its protective effect on the conductive carbon black.

[0054] In step 2, the secondary ball milling time is 2-4 hours, preferably 2.5-3 hours, for example, 2.5 hours. The constraint for setting this parameter is: if it is less than 2 hours, the ceramic raw material and conductive carbon black have not yet reached the molecular level of mixing; if it is more than 4 hours, the improvement in uniformity is not significant, and energy consumption and equipment wear increase linearly.

[0055] Step 3: Add a second dispersant to the composite slurry and ball mill three times to obtain a stable slurry.

[0056] In step 3, the second dispersant is preferably hydroxypropyl methylcellulose ether, with a concentration of 1 to 3 wt%, preferably 1.5 to 2.5 wt%; for example, 2 wt%.

[0057] The hydroxypropyl methylcellulose ether is a nonionic polymer with a large number of hydroxypropyl and methoxy side groups in its molecular chain, exhibiting excellent steric stabilization and film-forming properties. At this stage, hydroxypropyl methylcellulose ether primarily functions as a slurry rheology regulator and interface protector: in composite slurries, the adsorption layer on the particle surface tends to be saturated, and further addition of the first dispersant can easily lead to competitive adsorption or gelation; however, hydroxypropyl methylcellulose ether interacts with the hydroxyl groups on the particle surface through hydrogen bonds, forming a flexible polymer bridging layer between particles, effectively inhibiting re-agglomeration and sedimentation stratification caused by standing or subsequent operations.

[0058] Experiments show that when the concentration of hydroxypropyl methylcellulose ether is below 1 wt%, the yield stress of the stabilized slurry is insufficient; above 3 wt%, the viscosity is too high, affecting the molding density; while 1~3 wt% ensures the stability of the slurry while maintaining suitable fluidity, providing a process window for subsequent molding.

[0059] It should be emphasized that hydroxypropyl methylcellulose ether is pre-dissolved in water to the required concentration to ensure the consistency of the ball milling media.

[0060] In step 3, the ball milling speed is 300-500 r / min, preferably 350-450 r / min, for example, 400 r / min. The constraint for setting this parameter is that the main purpose of this stage is to achieve uniform coating and network construction of the second dispersant on the existing particle surface. If the rotation speed is too low, the shear force is insufficient to drive the long chains of the second dispersant to fully extend and anchor to the particle surface, resulting in uneven coating and poor stability; if the rotation speed is too high, it may destroy the already formed primary stable layer of the first dispersant-conductive carbon black, causing some conductive carbon black to desorb and re-aggregate.

[0061] Furthermore, the three ball milling times are 0.5~2h, preferably 1~1.5h, for example 1h. The constraint for setting this parameter is that the second dispersant can only achieve preliminary surface coverage within 0.5h; if extended to more than 2h, the second dispersant may entangle and crosslink, which will increase internal friction and is not conducive to subsequent molding.

[0062] In steps 1-3, with the total mass of conductive carbon black, the first dispersant, and the ceramic raw material being 100%, each component satisfies the following:

[0063] Conductive carbon black 7wt%~10wt%;

[0064] First dispersant: 0.5wt%~2wt%;

[0065] Alumina 50wt%~55wt%;

[0066] 20wt%~25wt% silicon dioxide;

[0067] Kyanite 4 wt%; of which alumina accounts for 54-58 wt% of kyanite;

[0068] The albite content is 3 wt% to 8 wt%, of which silica accounts for 66 to 68 wt% of the albite content.

[0069] In one specific embodiment, with the total mass of conductive carbon black, the first dispersant, and the ceramic raw material being 100%, each component satisfies the following:

[0070] 10 wt% conductive carbon black

[0071] First dispersant 1wt%;

[0072] 55 wt% alumina

[0073] 25 wt% silicon dioxide

[0074] Kyanite 4 wt%; of which alumina accounts for 55 wt% of kyanite;

[0075] The albite content is 5 wt%, of which silica accounts for 67.4 wt% of the albite content.

[0076] In another specific embodiment, with the total mass of conductive carbon black, the first dispersant, and the ceramic raw material being 100%, each component satisfies the following:

[0077] 7wt% conductive carbon black

[0078] First dispersant 1wt%;

[0079] 55 wt% alumina

[0080] 25 wt% silicon dioxide

[0081] Kyanite 4 wt%; of which alumina accounts for 55 wt% of kyanite.

[0082] The albite content is 8 wt%, of which silica accounts for 67.4 wt% of the albite content.

[0083] Furthermore, the second dispersant is 1 wt% to 2 wt% of the total mass of conductive carbon black, the first dispersant, and the ceramic raw material.

[0084] The aforementioned conductive carbon black is used to achieve percolation conductivity and structural stability; alumina is used to ensure the strength and insulation of the main crystalline phase; silica and albite synergistically generate an appropriate amount of transient liquid phase, promoting densification without encapsulating the conductive carbon black; the directional volume expansion generated by the high-temperature decomposition of kyanite compensates for sintering shrinkage and prevents secondary agglomeration of the conductive carbon black. The conductive carbon black and ceramic raw materials are uniformly mixed using a first and second dispersant. This composite formulation system is deeply coupled with the three-stage ball milling and sintering process in step 4, ultimately yielding a carbon ceramic resistance material with both low resistivity and a narrow temperature coefficient. This successfully solves the technical bottlenecks in traditional carbon ceramic materials, such as uneven conductive phase distribution and the difficulty in simultaneously achieving sintering densification and network maintenance.

[0085] In one specific embodiment, conductive carbon black and PVP aqueous solution are ball-milled once. PVP, as a highly efficient dispersant, effectively wets the surface of conductive carbon black and initially breaks up its agglomerates through steric hindrance. Then, ceramic raw materials are added for a second ball milling to fully mix the initially dispersed conductive phase with the ceramic raw materials. Finally, hydroxypropyl methylcellulose ether is added for a third ball milling. Hydroxypropyl methylcellulose ether, as a dispersant and stabilizer, effectively inhibits the re-agglomeration of dispersed particles by regulating the rheological properties of the slurry, ensuring the long-term stability of the dispersion system.

[0086] Step 4: The stabilized slurry is pretreated and then sintered to obtain the carbon ceramic resistive material.

[0087] In step 4, the pretreatment includes drying, sieving, pressing green bodies, and sintering.

[0088] The stabilized slurry is dried at 100-120°C for 8-24 hours, for example, at 110°C for 10 hours. Drying thoroughly removes physically adsorbed water and weakly bound water from the ball milling media, while preventing premature degradation of the first dispersant (e.g., PVP) and the second dispersant (e.g., hydroxypropyl methylcellulose ether) during the drying stage. A temperature slightly above 100°C can overcome capillary resistance and accelerate dehydration.

[0089] The dried powder is sieved to collect fine particles of 40-100 mesh, while coarse particles larger than 40 mesh are retained for later use. Sieving to select coarse particles prevents stress concentration and bridging defects during pressing.

[0090] The pressed green body is formed using a dry pressing method. Fine particles are pressed. The pressing pressure is 90-110 MPa, preferably 90-105 MPa, for example, 100 MPa; the pressing time is 10-60 s, preferably 20-30 s, for example, 30 s. By selecting the parameter range for the pressed green body, high porosity due to low pressure and damage to the conductive carbon black network caused by high pressure are avoided. Furthermore, sufficient densification and springback suppression are achieved through the holding time.

[0091] The sintering process employs gradient temperature sintering, where the green body is pre-placed on a coarse-grained surface, followed by sintering, including:

[0092] First stage: Increase the temperature from room temperature to 500℃~600℃ at a heating rate of 2~5℃ / min;

[0093] Second stage: Continue to heat up from the temperature of the first stage to 900-1000℃ at a heating rate of 4~7℃ / min;

[0094] The third stage: continue to heat the temperature from the second stage to 1250~1400℃ at a heating rate of 1~3℃ / min, and hold at this temperature for 3~4 hours;

[0095] Fourth stage: The temperature is reduced from the third stage temperature to 700-800℃ at a rate of 2-5℃ / min, and then cooled to room temperature in the furnace.

[0096] During sintering, the first stage is used to complete the pyrolysis of the first and second dispersants and remove residual moisture to prevent cracking. In particular, the use of a slower rate is conducive to the slow removal of residual first and second dispersants, avoiding cracking of the green body or disturbance of the conductive carbon black distribution due to excessive volatilization. The second stage is used to activate the albite-silica-alumina system to generate a transient liquid phase, promoting particle rearrangement without encapsulating conductive carbon black. The ceramic phase transformation is achieved quickly by appropriately increasing the heating rate. In the third stage, kyanite undergoes directional decomposition and expansion to compensate for the sintering shrinkage of the ceramic matrix, effectively inhibiting the secondary agglomeration and network breakage of conductive carbon black. By reducing the heating rate again, the ceramic matrix is ​​slowly densified, while the conductive carbon black is guided to build a stable and continuous three-dimensional conductive network on the basis of the already formed uniform distribution. The fourth stage realizes thermal stress relaxation and mullite crystal phase perfection, ensuring the stability of the temperature coefficient of resistance.

[0097] The aforementioned gradient heating effectively coordinates the contradictions between the elimination of the first and second dispersants, ceramic sintering, and the formation of the conductive network, avoiding secondary agglomeration of carbon black or breakage of conductive pathways caused by improper heating rates in traditional sintering processes.

[0098] Furthermore, the protective atmosphere for sintering is argon to prevent the conductive carbon black from oxidizing at high temperatures.

[0099] Preferably, the sintering includes:

[0100] First stage: Increase the temperature from room temperature to 550℃~600℃ at a heating rate of 2~4℃ / min;

[0101] Second stage: Continue to heat the temperature from the first stage to 950-1000℃ at a heating rate of 5-6℃ / min;

[0102] The third stage: continue to heat the temperature from the second stage to 1300-1400℃ at a heating rate of 2-3℃ / min, and hold at this temperature for 3-4 hours;

[0103] Fourth stage: The temperature is reduced from the third stage temperature to 750-800℃ at a rate of 2-4℃ / min, and then cooled to room temperature in the furnace.

[0104] In one specific embodiment, the sintering includes:

[0105] First stage: Increase the temperature from room temperature to 600℃ at a heating rate of 3℃ / min;

[0106] Second stage: Continue heating from 600℃ to 1000℃ at a heating rate of 6℃ / min;

[0107] The third stage: continue heating from 1000℃ to 1350℃ at a heating rate of 2℃ / min, and hold at this temperature for 3 hours;

[0108] Fourth stage: The temperature is reduced from 1350℃ to 800℃ at a rate of 3℃ / min, and then cooled to room temperature in the furnace.

[0109] In this invention, by constructing a three-stage step-by-step ball milling and staged sintering process, the core challenges of uneven dispersion of the conductive phase and the difficulty in simultaneously achieving sintering densification and maintaining the conductive network in carbon ceramic resistive materials are solved. Compared to traditional single dispersion or one-step mixing processes, this solution exhibits significant advantages in multiple dimensions:

[0110] First, a dual dispersant is introduced in stages to fully utilize the adsorption and depolymerization of conductive carbon black by the first dispersant and the steric stabilization effect of the second dispersant on the high solids content slurry.

[0111] Secondly, the three-stage ball milling process ensures the three-dimensional uniform mixing of conductive carbon black and ceramic powder while avoiding excessive mechanical damage, laying a structural foundation for building a continuous conductive network.

[0112] Furthermore, the directional volume expansion generated by the high-temperature decomposition of kyanite effectively offsets the overall shrinkage of the ceramic matrix during the densification process, preventing secondary agglomeration of carbon black or network breakage caused by stress concentration.

[0113] Finally, gradient sintering provides a sufficient time window for the removal of the first and second dispersants, liquid phase formation, crystal phase change, and stress relaxation, allowing the densification process and conductive network to proceed fully.

[0114] The combined effect of the aforementioned multi-scale synergistic mechanisms results in a carbon ceramic resistive material that not only possesses stable low resistivity and an extremely narrow temperature coefficient of resistance, but also exhibits high batch repeatability, excellent mechanical strength, and good structural uniformity. This fully demonstrates the systematic innovation and technological advancement of this invention in material design and preparation processes.

[0115] Thirdly, according to the present invention, a carbon ceramic linear resistor is obtained by surface polishing and metal spraying of the carbon ceramic resistor material.

[0116] Polishing improves the adhesion and mechanical strength of the sprayed metal layer and effectively removes impurities, ensuring the purity of subsequent metal layers. The metal layer is preferably any one or more of aluminum, gold, silver, and copper, but is not limited to these. Example

[0117] The present invention is further described below through specific examples; however, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention. Example 1

[0118] This embodiment provides a method for preparing a carbon ceramic linear resistor, such as... Figure 1 As shown, the specific steps include:

[0119] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0120] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55wt%), and 5% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0121] (3) Weigh 1.2% of hydroxypropyl methylcellulose ether (HPMC) based on the mass of conductive carbon black, PVP and ceramic raw materials as 100%, prepare an HPMC aqueous solution with a concentration of 2wt%, add it to the composite slurry obtained in step 2, and continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0122] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0123] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1350℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1350℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0124] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 2

[0125] The carbon ceramic linear resistor was prepared in a manner similar to that in Example 1, except that the temperature in the final stage of sintering was different. Specifically, the following steps were included:

[0126] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0127] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55 wt%), and 5% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0128] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0129] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0130] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1300℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1300℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0131] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 3

[0132] The carbon ceramic linear resistor was prepared in a manner similar to that in Example 1, except that the temperature in the final stage of sintering was different. Specifically, the following steps were included:

[0133] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0134] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55wt%), and 5% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0135] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0136] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0137] The green body is placed in a crucible containing the aforementioned coarse particles, and the crucible is placed in a tube sintering furnace, which is then filled with argon gas as a protective atmosphere for sintering. Figure 5 The sintering temperature change curve is shown as follows: the temperature is increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature is increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature is increased from 1000℃ to 1400℃ at a heating rate of 2℃ / min; the temperature is held at this temperature for 3 hours; the temperature is decreased from 1400℃ to 800℃ at a heating rate of 3℃ / min; and then the temperature is cooled to room temperature in the furnace to obtain carbon ceramic resistance material.

[0138] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 4

[0139] The carbon ceramic linear resistor was prepared in a manner similar to that of Example 1, except that the raw material composition was different in step (1), specifically including the following steps:

[0140] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 7% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0141] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55wt%), and 8% albite (silicon oxide content approximately 67.4wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0142] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0143] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0144] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1350℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1350℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0145] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 5

[0146] The carbon ceramic linear resistor was prepared in a manner similar to that in Example 4, except that the temperature in the final stage of sintering was different. Specifically, the following steps were included:

[0147] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 7% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0148] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55wt%), and 8% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0149] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0150] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0151] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1300℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1300℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0152] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 6

[0153] The carbon ceramic linear resistor was prepared in a manner similar to that in Example 4, except that the temperature in the final stage of sintering was different. Specifically, the following steps were included:

[0154] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 7% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0155] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55 wt%), and 8% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0156] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0157] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0158] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1380℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1380℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0159] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor. Example 7

[0160] The carbon ceramic linear resistor was prepared in a manner similar to that in Example 4, except that the temperature in the final stage of sintering was different. Specifically, the following steps were included:

[0161] (1) Based on the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 7% conductive carbon black (purity 99.9%, particle size 4~6μm, D50 5μm) and 1% polyvinylpyrrolidone (PVP). Dissolve PVP in deionized water to prepare a 10wt% PVP aqueous solution. Add the above conductive carbon black and PVP aqueous solution together to a ball mill jar, place it in a ball mill, and pre-ball mill at 400 r / min for 1 hour to obtain a pre-dispersed slurry.

[0162] (2) Taking the mass of conductive carbon black, PVP, and ceramic raw materials as 100%, accurately weigh 55% alumina (purity 99.9%, particle size 1~3μm, D50 2μm), 25% silica (purity 99.9%, particle size 4~6μm, D50 5μm), 4% kyanite (alumina content approximately 55 wt%), and 8% albite (silicon oxide content approximately 67.4 wt%). Add the above ceramic powder to the pre-dispersed slurry, and add deionized water at a mass ratio of 1:1 to ceramic powder. Ball mill at 400 r / min for 2.5 hours to obtain the composite slurry.

[0163] (3) Weigh hydroxypropyl methylcellulose ether (HPMC) in a mass of 1.2% of the total mass of conductive carbon black, PVP and ceramic raw materials. Prepare an aqueous solution of HPMC with a concentration of 2wt% and add it to the composite slurry obtained in step 2. Continue to ball mill at 400 r / min for 1 hour to obtain a stable slurry.

[0164] (4) The stabilized slurry is dried in an oven at 110°C for 10 hours to obtain a dried powder. The dried powder is sieved to collect particles of 40-100 mesh; coarse particles with a particle size greater than 40 mesh are kept for later use. The 40-100 mesh particles are subjected to a dry pressing process, under a pressure of 100 MPa, and held for 30 seconds to obtain a green body.

[0165] The green body was placed in a crucible containing the aforementioned coarse particles, and the crucible was placed in a tube sintering furnace. Argon gas was introduced as a protective atmosphere for sintering: the temperature was increased from room temperature to 600℃ at a heating rate of 3℃ / min; the temperature was increased from 600℃ to 1000℃ at a heating rate of 5℃ / min; the temperature was increased from 1000℃ to 1400℃ at a heating rate of 2℃ / min; and the temperature was held at this temperature for 3 hours; the temperature was decreased from 1400℃ to 800℃ at a heating rate of 3℃ / min; and then the furnace was cooled to room temperature to obtain the carbon ceramic resistance material.

[0166] The sintered body was successively polished with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to ensure that the upper and lower surfaces were flat and smooth. Then, aluminum was sprayed onto the upper and lower surfaces as electrodes, and then dried in an oven at 100°C to obtain the carbon ceramic linear resistor.

[0167] Comparative Example 1

[0168] The carbon ceramic linear resistor was prepared using the traditional ball milling mixing method, and the specific steps are as follows:

[0169] (1) Based on the mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black, 1% naphthalene sulfonic acid formaldehyde condensate dispersant, 55% alumina, 25% silicon dioxide, 4% kyanite and 5% albite. Weigh deionized water according to the mass ratio of deionized water to powder of 1:1, pour it into the ball mill jar and mix. The ball mill speed is 400 r / min, and the ball milling is carried out for 3 hours to obtain the ball mill slurry.

[0170] (2) Dry the ball mill slurry at 110°C for 10 hours. Add 10wt% polyvinyl alcohol to the dried powder and grind it into granules. Polyvinyl alcohol is used as a binder. The amount of polyvinyl alcohol added is 3% of the total mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials.

[0171] (3) The granulated powder is dry-pressed to obtain a blank. The pressure of dry pressing is 100 MPa and the holding time is 30 s. Then, the blank is heated from room temperature to 1350℃ at a heating rate of 5℃ / min under an argon atmosphere and held for 3 h. Then, it is cooled to 800℃ at a cooling rate of 5℃ / min and then cooled to room temperature in the furnace to obtain carbon ceramic resistance material.

[0172] (4) The carbon ceramic resistor material is subjected to surface polishing treatment. The sandpaper is 200 mesh, 400 mesh, 600 mesh and 800 mesh in sequence. Aluminum is sprayed on the upper and lower surfaces by thermal spraying machine and dried in an oven at 100°C to obtain carbon ceramic linear resistor.

[0173] Comparative Example 2

[0174] The carbon ceramic linear resistor was prepared in a manner similar to Comparative Example 1, the difference being the temperature at the final stage of sintering, specifically including the following steps:

[0175] (1) Based on the mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black, 1% naphthalene sulfonic acid formaldehyde condensate dispersant, 55% alumina, 25% silicon dioxide, 4% kyanite and 5% albite. Weigh deionized water according to the mass ratio of deionized water to powder of 1:1, pour it into the ball mill jar and mix. The ball mill speed is 400 r / min, and the ball milling is carried out for 3 hours to obtain the ball mill slurry.

[0176] (2) Dry the ball mill slurry at 110°C for 10 hours. Add 10wt% polyvinyl alcohol to the dried powder and grind it into granules. Polyvinyl alcohol is used as a binder. The amount of polyvinyl alcohol added is 3% of the total mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials.

[0177] (3) The granulated powder is dry-pressed to obtain a blank. The pressure of dry pressing is 100 MPa and the holding time is 30 s. Then, the blank is heated from room temperature to 1300℃ at a heating rate of 5℃ / min under an argon atmosphere and held for 3 h. Then, it is cooled to 800℃ at a cooling rate of 5℃ / min and then cooled to room temperature in the furnace to obtain carbon ceramic resistance material.

[0178] (4) The carbon ceramic resistor material is subjected to surface polishing treatment. The sandpaper is 200 mesh, 400 mesh, 600 mesh and 800 mesh in sequence. Aluminum is sprayed on the upper and lower surfaces by thermal spraying machine and dried in an oven at 100°C to obtain carbon ceramic linear resistor.

[0179] Comparative Example 3

[0180] The carbon ceramic linear resistor was prepared in a manner similar to Comparative Example 1, the difference being the temperature at the final stage of sintering, specifically including the following steps:

[0181] (1) Based on the mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials as 100%, accurately weigh 10% conductive carbon black, 1% naphthalene sulfonic acid formaldehyde condensate dispersant, 55% alumina, 25% silicon dioxide, 4% kyanite and 5% albite. Weigh deionized water according to the mass ratio of deionized water to powder of 1:1, pour it into the ball mill jar and mix. The ball mill speed is 400 r / min, and the ball milling is carried out for 3 hours to obtain the ball mill slurry.

[0182] (2) Dry the ball mill slurry at 110°C for 10 hours. Add 10wt% polyvinyl alcohol to the dried powder and grind it into granules. Polyvinyl alcohol is used as a binder. The amount of polyvinyl alcohol added is 3% of the total mass of conductive carbon black, naphthalene sulfonic acid formaldehyde condensate dispersant and ceramic raw materials.

[0183] (3) The granulated powder is dry-pressed to obtain a blank. The pressure of dry pressing is 100 MPa and the holding time is 30 s. Then, the blank is heated from room temperature to 1400℃ at a heating rate of 5℃ / min under an argon atmosphere and held for 3 h. Then, it is cooled to 800℃ at a cooling rate of 5℃ / min and then cooled to room temperature in the furnace to obtain carbon ceramic resistance material.

[0184] (4) The carbon ceramic resistor material is subjected to surface polishing treatment. The sandpaper is 200 mesh, 400 mesh, 600 mesh and 800 mesh in sequence. Aluminum is sprayed on the upper and lower surfaces by thermal spraying machine and dried in an oven at 100°C to obtain carbon ceramic linear resistor.

[0185] The electrical performance of the carbon ceramic linear resistors obtained in Examples 1-7 and Comparative Example 1 was tested: A high-precision digital resistance meter was used to measure their DC resistance values ​​at room temperature in an environment free from electromagnetic interference; then, based on the actual geometric dimensions of the samples (length L, cross-sectional area A), the resistance values ​​were calculated according to the formula... The volume resistivity ρ (unit: Ω·m) was calculated. The test results are shown in the table below:

[0186]

[0187] As shown in Table 1, in Examples 1-3, the sintering temperature was between 1300℃ and 1400℃. With increasing sintering temperature, the resistivity initially decreased and then increased. Combined with process analysis, it can be seen that as the sintering temperature increases, the liquid phase viscosity decreases, promoting the rearrangement and densification of ceramic particles. Simultaneously, the conductive carbon black network becomes more uniformly distributed in the gradient thermal field, avoiding local aggregation, thus effectively reducing the overall resistivity. Example 1 showed the best effect. When the temperature continues to rise, excessive mullite phase formation occurs within the ceramic resistivity system, disrupting the continuous conductive network and causing an increase in resistivity. In particular, comparing Example 1 and Comparative Example 1 (both with the same mass fraction of conductive carbon black and ceramic raw materials), Example 1, employing a synergistic process of dispersant-controlled distribution + three-stage ball milling + gradient thermal field curing, exhibited a significantly lower resistivity than Comparative Example 1, with a reduction of 62%.

[0188] Table 1 also shows that, compared with Comparative Example 1, the carbon black content in Examples 4-7 decreased from 10% to 7%, while the sintering process conditions remained consistent. Test results indicate that the material resistivity shows an increasing trend. This is because, with the increase in carbon black content, it is easier to construct continuous conductive network pathways within the ceramic matrix, resulting in an increase in the number of conductive chains and thus a decrease in system resistivity. Furthermore, Examples 4-7 also show that, under the condition of fixed carbon black content, as the sintering temperature gradually increases, the material resistivity exhibits a pattern of first decreasing and then increasing, a trend consistent with the experimental results obtained in Examples 1-3.

[0189] Figure 2(a) shows the microstructure of the carbon ceramic resistive material prepared in Example 1; Figure 2(b) shows the carbon element distribution inside the carbon ceramic resistive material prepared in Example 1; Combining Figure 2(a) and Figure 2(b), it can be seen that the carbon ceramic resistive material forms a matrix structure with certain pores inside, and the carbon elements are uniformly distributed on the surface of the ceramic skeleton and overlap each other to form a continuous conductive network structure.

[0190] Figure 3(a) shows the carbon element distribution of the carbon ceramic resistive material prepared in Example 1; Figure 3(b) shows the carbon element distribution of the carbon ceramic resistive material prepared in Comparative Example 1. It can be seen that in Comparative Example 1, the carbon black agglomerates significantly, forming defect areas that interrupt the conductive path, resulting in increased resistivity; while in Example 1, the carbon black is uniformly dispersed, constructing a continuous and stable conductive network.

[0191] Figure 4 The carbon ceramic linear resistors prepared in Examples 1 (1350°C) and 3 (1400°C) have a temperature coefficient of resistance (TCR) of 0 to -0.15% / °C, which meets the performance requirements of industry standards for this type of carbon ceramic linear resistor. This indicates that they have good resistance stability within the operating temperature range and have practical application potential.

[0192] The present invention has been described in detail above with reference to preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are merely illustrative explanations of the invention and do not constitute any limitation on the scope of protection of the invention. Various improvements, equivalent substitutions, or modifications can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of protection of the invention, and all such modifications fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A carbon ceramic resistive material, characterized in that, The carbon ceramic resistive material is composed of conductive carbon black and a ceramic matrix, and the conductive carbon black forms a continuous three-dimensional conductive network in the ceramic matrix; the resistivity of the carbon ceramic resistive material at room temperature is 1.14 Ω·m to 2.40 Ω·m, and the temperature coefficient of resistance is 0 to -0.15% / ℃.

2. The carbon ceramic resistive material according to claim 1, characterized in that, Preferably, the ceramic matrix comprises at least alumina, silicon dioxide, kyanite, and albite.

3. The carbon ceramic resistive material according to claim 1, characterized in that, Based on the total mass of the carbon ceramic resistive material as 100%, it comprises: 7wt%~10wt% conductive carbon black, 50wt%~55wt% alumina, 20wt%~25wt% silicon oxide, 4wt% kyanite and 3wt%~8wt% albite.

4. A method for preparing the carbon ceramic resistive material according to any one of claims 1-3, characterized in that, The method includes: Step 1: The conductive carbon black is mixed with the first dispersant and ball-milled once to obtain a pre-dispersed slurry; Step 2: Add ceramic raw materials to the pre-dispersed slurry and then ball mill it twice to obtain a composite slurry; Step 3: Add a second dispersant to the composite slurry and ball mill three times to obtain a stable slurry; Step 4: The stabilized slurry is pretreated and then sintered to obtain the carbon ceramic resistive material.

5. The method according to claim 4, characterized in that, In step 1, the ball milling speed is 300~500 r / min, and the interval is 0.5~2h.

6. The method according to claim 4, characterized in that, In step 2, the mass ratio of the secondary ball milling media to the ceramic raw material is 1:(0.8-1.2).

7. The method according to claim 4, characterized in that, In step 3, the second dispersant is hydroxypropyl methylcellulose ether.

8. The method according to claim 4, characterized in that, The pretreatment includes drying, sieving, pressing green bodies, and sintering.

9. A carbon ceramic linear resistor, characterized in that, The carbon ceramic linear resistor is obtained by surface polishing and metal spraying of the carbon ceramic resistor material according to any one of claims 1-3.

10. The carbon ceramic linear resistor according to claim 9, characterized in that, The metal layer is any one of aluminum, gold, silver, and copper.

Images