Preparation method of graphene modified electric heating ceramic

Abstract

The application relates to a preparation method of graphene modified electric heating ceramics, which comprises the following steps: step 1, preparing a graphite slurry; step 2, encapsulating the prepared graphite slurry and a ceramic matrix; step 3, electrochemically preparing graphene; and step 4, post-treatment. The graphene is prepared on the surface of the honeycomb ceramic in an electrochemical mode, and the problems of functionality and dispersity are solved. The preparation process is simple, the materials used are expanded graphite and conventional chemicals, and the method is green and environment-friendly. The graphene is uniformly distributed on the ceramic product, and the electric heating ceramic has good electric conductivity and heat conductivity, and the rapid heating and uniform heating capacity of the electric heating ceramic is greatly improved.

Description

Technical Field

[0001] This invention relates to a method for preparing ceramics, specifically to a method for preparing graphene-modified electric heating ceramics with uniform graphene distribution, good electrical and thermal conductivity, and significantly improved ability of electric heating ceramics to generate rapid and uniform heat. Background Technology

[0002] This invention relates to a method for preparing an electrically heated ceramic, specifically a method for preparing an electrically heated ceramic modified with graphene.

[0003] There are two main existing technologies. One is PTC ceramic, which is the mainstream material used in automobiles. Its core material is barium titanate (BaTiO3), which is modified by doping with acceptor impurities such as Mn, Fe, and Cu. It is then sintered and processed into semiconductor ceramic elements. Its most significant characteristic is that its resistivity increases non-linearly and sharply near a specific temperature (Curie point, typically 120-135℃), with a change ranging from 3 to 8 orders of magnitude. This characteristic distinguishes it from traditional constant-resistance heating elements, giving it natural self-limiting, self-regulating, and overheat protection functions, achieving dynamic temperature balance without the need for additional temperature control devices. The other technology is graphene-modified ceramic, which has similar effects. This involves mixing graphene powder or slurry with ceramic powder, grinding the mixture, and finally sintering it into ceramic. Patent CN121673043A describes the characteristics of PTC ceramics mentioned above, while also indicating that the performance of PTC ceramics depends on complex sintering processes, resulting in high costs. Patent CN121573973A indicates that traditional PTC ceramics generally contain lead, posing significant environmental problems. Lead-free PTC ceramics require even more stringent processing techniques and are still largely in the research and development stage. Patent CN121583671A indicates that there are significant technical contradictions between the power consumption and other performance characteristics of traditional PTC ceramics. For example, it is impossible to maintain product reliability while reducing product size, to maintain recovery time without increasing Curie temperature, and to maintain chip thermal shock resistance without increasing chip temperature rise. All of these require specialized technical research. Patent CN121405482B mentions that graphene composite ceramics need to be used together with binders to solve dispersion problems. Summary of the Invention

[0004] To address the aforementioned problems, the main objective of this invention is to provide a method for preparing graphene-modified electric heating ceramics that exhibits uniform graphene distribution, excellent electrical and thermal conductivity, and significantly improves the rapid and uniform heating capabilities of electric heating ceramics.

[0005] This invention solves the above-mentioned technical problems through the following technical solution: a method for preparing graphene-modified electrically heated ceramics, the preparation method comprising: Step 1: Prepare graphite slurry; Step 2: Encapsulation preparation of graphite slurry and ceramic matrix; Step 3: Electrochemical preparation of graphene; Step 4: Post-processing.

[0006] In a specific embodiment of the present invention, step 1 includes: Step 101: Calcining the expanded graphite at a low temperature under an inert atmosphere to remove impurities; Step 102: Place the graphite that has been calcined at low temperature into water, add a dispersant and sulfate, and perform shearing and emulsification to prepare a graphite slurry. The dispersant is selected from one or more of the following: silane coupling agent, polyethylene glycol, silica sol, methylcellulose, and aluminum dihydrogen phosphate. The sulfate is selected from one or more of the following: sodium sulfate, ammonium sulfate, potassium sulfate, cobalt sulfate, nickel sulfate, stannous sulfate, and ferrous sulfate. Step 103: Perform ultrasonic treatment on the graphite slurry from step 102 to ensure uniform dispersion of the graphite material.

[0007] In a specific embodiment of the present invention, step 2 includes: Step 201: Place the graphite slurry prepared in step 1 and the honeycomb ceramic together in a tubular container, with the inner diameter of the tubular container being slightly larger than the outer diameter of the honeycomb ceramic. Step 202: Place the honeycomb ceramic into the tubular container to ensure it is in full contact with the graphite slurry; Step 203: Using the two ends of the tubular container as electrodes, apply direct current to prepare graphene electrochemically at a voltage of 20-30V and 0.1-1A for 30-60 minutes.

[0008] The tubular container is insulated in the middle and conductive at both ends. When energized, the current flows from one end to the other through graphite slurry. Under the combined action of the current and sulfate, the graphite undergoes a chemical reaction. On the one hand, the edges of the graphite are oxidized, and on the other hand, the sulfate is intercalated between the graphite sheets to form a graphene precursor. This method directly grows graphene in situ on the ceramic surface, with good bonding force with the ceramic and uniform distribution, without the need for subsequent mixing processing.

[0009] In a specific embodiment of the present invention, step 3 includes: Step 301: After the graphene precursor in step 203 is prepared, immediately place the tubular container in an ultrasonic tank for ultrasonic exfoliation at a frequency of 40-60kHz and a power of 200-400W. Step 302: Remove the ceramic after ultrasonic peeling and let it air dry naturally; Step 303: Coat both ends of the ceramic with conductive silver paste.

[0010] In a specific embodiment of the present invention, step 4 includes: Step 401: The ceramic coated with conductive silver paste is calcined at high temperature in an inert atmosphere at 600-800℃ for 1-2 hours. Step 402: After naturally cooling to room temperature, measure the resistance value of the ceramic; Step 403: Adjust the coating thickness of the conductive silver paste according to the measured resistance value.

[0011] In a specific embodiment of the present invention, the honeycomb ceramic is selected from one or more of cordierite, alumina, and silicon oxide.

[0012] The positive and progressive effects of this invention are as follows: The method for preparing graphene-modified electrically heated ceramics provided by this invention has the following beneficial effects: 1. This invention uses low-temperature calcination to expand graphite and remove impurities before further processing. The preparation process is simple, significantly reducing production costs and avoiding environmental pollution problems that may occur during high-temperature processing, resulting in excellent environmental performance.

[0013] 2. This invention achieves uniform dispersion and stable bonding of graphene on the ceramic surface by directly covering it with graphene, effectively solving the problem that traditional mechanical mixing methods are difficult to achieve uniform dispersion of graphene and improving the overall performance of the composite material.

[0014] 3. The graphene-modified electric heating ceramic prepared by this invention has excellent electrical and thermal conductivity, can generate heat uniformly, and due to the high thermal conductivity of graphene, it can rapidly heat up the external environment, significantly improving the thermal response speed and heat dissipation efficiency of the ceramic material.

[0015] 4. The preparation method used in this invention can easily form a graphene modified layer on the surface of the ceramic matrix without changing its properties, thus giving the original ceramic products new application value and improving their service life and market competitiveness.

[0016] 5. The composite material prepared by this invention has good mechanical properties, effectively improves the brittleness and fracture toughness of ceramic materials, enhances the impact resistance of materials, and expands its application range in high-end fields. Detailed Implementation

[0017] The preferred embodiments of the present invention are given below with reference to specific data to illustrate the technical solution of the present invention in detail.

[0018] Traditional PTC ceramics suffer from high costs, environmental restrictions, and power dependence on heat dissipation. Their material doping processes are complex, resulting in high manufacturing costs, and they require additional circuit protection devices to handle cold-start inrush currents. Furthermore, the stability and durability of PTC ceramics at high temperatures need improvement, as high temperatures can lead to performance degradation and affect their reliability in long-term use.

[0019] In existing graphene-modified ceramic composites, the dispersion and uniformity of graphene are still not ideal, easily leading to agglomeration and affecting the overall performance of the composite material. This agglomeration not only reduces the conductivity of the material but may also cause localized overheating or current concentration during use, thus affecting its safety and stability in practical applications.

[0020] Traditional ceramic materials are brittle, have low fracture toughness, and their thermal conductivity is not ideal, which limits their application in certain high-end fields. These characteristics make ceramic materials prone to breakage or deformation when subjected to external impacts or mechanical stress, affecting their application in fields requiring long-term durability, such as electronic devices. In addition, the insufficient thermal conductivity of ceramic materials also limits their heat dissipation capacity in high-power applications, which may lead to a decrease in the material's operating efficiency at high temperatures.

[0021] Existing graphene semiconductor ceramic paste formulations require further optimization to improve their heating temperature and power density. Current paste formulations are insufficient in enhancing the material's electrical and thermal conductivity, limiting its performance under high-temperature, high-power conditions. Furthermore, the paste's adhesion and stability also need improvement to ensure controllability and consistency during coating and processing.

[0022] The isothermal point of traditional PTC ceramics is determined by the material formulation and cannot be adjusted after leaving the factory. Furthermore, its power regulation method is unique, making linear power regulation impossible through simple voltage adjustment; special methods such as PWM on / off switching or heat dissipation adjustment are required. This fixed isothermal point limits the material's adaptability to different environmental conditions, especially in applications with significant temperature variations, making it difficult to maintain stable performance. In addition, the special power regulation method increases system complexity and control difficulty, potentially affecting system response speed and accuracy, and failing to meet rapidly changing power demands.

[0023] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing graphene-modified electrically heated ceramics, comprising: Step 1: Prepare graphite slurry; Step 2: Encapsulation preparation of graphite slurry and ceramic matrix; Step 3: Electrochemical preparation of graphene; Step 4: Post-processing.

[0024] Step 1 includes: Step 101: Calcining the expanded graphite at a low temperature under an inert atmosphere to remove impurities; Step 102: Place the graphite that has been calcined at low temperature into water, add a dispersant and sulfate, and perform shearing and emulsification to prepare a graphite slurry. The dispersant is selected from one or more of the following: silane coupling agent, polyethylene glycol, silica sol, methylcellulose, and aluminum dihydrogen phosphate. The sulfate is selected from one or more of the following: sodium sulfate, ammonium sulfate, potassium sulfate, cobalt sulfate, nickel sulfate, stannous sulfate, and ferrous sulfate. Step 103: Ultrasonic treatment of the graphite slurry to ensure uniform dispersion of the graphite material.

[0025] Step 2 includes: Step 201: Place the graphite slurry in a tubular container, the inner diameter of which is slightly larger than the outer diameter of the honeycomb ceramic. Step 202: Place the honeycomb ceramic into the tubular container to ensure it is in full contact with the graphite slurry; Step 203: Using the two ends of the tubular container as electrodes, apply direct current to prepare graphene electrochemically at a voltage of 20-30V and 0.1-1A for 30-60 minutes.

[0026] The tubular container is insulated in the middle and conductive at both ends. When energized, the current flows from one end to the other through graphite slurry. Under the combined action of the current and sulfate, the graphite undergoes a chemical reaction. On one hand, the edges of the graphite are oxidized; on the other hand, sulfate is intercalated between the graphite sheets, forming a graphene precursor. This method allows for the direct in-situ growth of graphene on the ceramic surface, resulting in excellent adhesion to the ceramic and uniform distribution, eliminating the need for subsequent mixing processes.

[0027] Step 3 includes: Step 301: After the graphene precursor is prepared, immediately place the tubular container in an ultrasonic tank for ultrasonic peeling at a frequency of 40-60kHz and a power of 200-400W. Step 302: Remove the ceramic after ultrasonic peeling and let it air dry naturally; Step 303: Coat both ends of the ceramic with conductive silver paste.

[0028] Step 4 includes: Step 401: The ceramic coated with conductive silver paste is calcined at high temperature in an inert atmosphere at 600-800℃ for 1-2 hours. Step 402: After naturally cooling to room temperature, measure the resistance value of the ceramic; Step 403: Adjust the coating thickness of the conductive silver paste according to the measured resistance value to ensure that the resistance of the final product is within the set range.

[0029] The honeycomb ceramic is selected from one or more of cordierite, alumina, and silicon dioxide.

[0030] Below are some specific implementation examples: Example 1: This invention provides a method for preparing graphene-modified electrically heated ceramics, the specific steps of which are as follows: Step 1: Prepare graphite slurry: Step 101: Heat the expanded graphite to 600°C in a nitrogen atmosphere at a heating rate of 2°C / min, hold for 2 hours, and allow it to cool naturally to room temperature to remove impurities. Step 102: Place the graphite that has been calcined at low temperature into deionized water, add polyethylene glycol and sodium sulfate in a mass ratio of 1:0.01, perform high-speed shearing for 30 minutes, and ultrasonic emulsify for 1 hour to prepare graphite slurry. Step 103: Treat the graphite slurry under ultrasonic conditions of 40kHz and 200W for 30 minutes to ensure uniform dispersion of the graphite material.

[0031] Step 2: Encapsulation and preparation of graphite slurry and ceramic substrate: Step 201: Place the graphite slurry inside a stainless steel tube with an inner diameter of 15mm; Step 202: Place the cordierite honeycomb ceramic with a diameter of 12mm into the stainless steel tube mentioned above, so that it is in full contact with the graphite slurry; Step 203: Using the two ends of the stainless steel tube as electrodes, apply direct current to prepare graphene electrochemically at a voltage of 25V and 0.5A for 45 minutes.

[0032] Step 3: Electrochemical preparation of graphene: Step 301: After the graphene growth is complete, immediately place the stainless steel tube in an ultrasonic tank for ultrasonic peeling at a frequency of 50kHz and a power of 300W. Step 302: Remove the ceramic after ultrasonic peeling and let it air dry naturally; Step 303: Coat both ends of the ceramic with a conductive silver paste with a thickness of 50μm.

[0033] Step 4, Post-processing: Step 401: The ceramic coated with conductive silver paste is heated to 700°C at a heating rate of 5°C / min under a nitrogen atmosphere and held at that temperature for 1.5 hours. Step 402: After naturally cooling to room temperature, the resistance of the ceramic is measured to be 100Ω; Step 403: Adjust the coating thickness of the conductive silver paste according to the measured resistance value to ensure that the resistance of the final product is within the range of 80-120Ω.

[0034] Example 2: This invention provides a method for preparing graphene-modified electrically heated ceramics, the specific steps of which are as follows: Step 1: Prepare graphite slurry: Step 101: Heat the expanded graphite to 650°C in an argon atmosphere at a heating rate of 3°C / min, hold for 1.5 hours, and allow it to cool naturally to room temperature to remove impurities. Step 102: Place the graphite that has been calcined at low temperature into deionized water, add polyethylene glycol and potassium sulfate in a mass ratio of 1:0.005, perform high-speed shearing for 45 minutes, and ultrasonic emulsify for 1.5 hours to prepare graphite slurry. Step 103: Treat the graphite slurry under ultrasonic conditions of 45kHz and 250W for 45 minutes to ensure uniform dispersion of the graphite material.

[0035] Step 2: Encapsulation and preparation of graphite slurry and ceramic substrate: Step 201: Place the graphite slurry inside a stainless steel tube with an inner diameter of 20mm; Step 202: Place the alumina honeycomb ceramic with a diameter of 18mm into the stainless steel tube above to make it fully contact the graphite slurry; Step 203: Using the two ends of the stainless steel tube as electrodes, apply direct current to prepare graphene electrochemically at a voltage of 28V and 0.8A for 60 minutes.

[0036] Step 3: Electrochemical preparation of graphene: Step 301: After the graphene growth is complete, immediately place the stainless steel tube in an ultrasonic tank for ultrasonic peeling at a frequency of 55kHz and a power of 350W. Step 302: Remove the ceramic after ultrasonic peeling and let it air dry naturally; Step 303: Coat both ends of the ceramic with a conductive silver paste with a thickness of 70μm.

[0037] Step 4, Post-processing: Step 401: The ceramic coated with conductive silver paste is heated to 750°C at a heating rate of 6°C / min under a nitrogen atmosphere and held at that temperature for 2 hours. Step 402: After naturally cooling to room temperature, the resistance of the ceramic is measured to be 80Ω; Step 403: Adjust the coating thickness of the conductive silver paste according to the measured resistance value to ensure that the resistance of the final product is within the range of 90-110Ω.

[0038] Compared with existing technologies, this invention uses low-temperature calcination to expand graphite and remove impurities before further processing. The preparation process is simple, significantly reducing production costs and avoiding environmental pollution problems that may occur during high-temperature processing, resulting in excellent environmental performance.

[0039] Compared with existing technologies, this invention achieves uniform dispersion and stable bonding of graphene on the ceramic surface by directly covering it with graphene, effectively solving the problem that traditional mechanical mixing methods are difficult to achieve uniform dispersion of graphene and improving the overall performance of the composite material.

[0040] Compared with existing technologies, the graphene-modified electric heating ceramic prepared by this invention has excellent electrical and thermal conductivity, can generate heat uniformly, and due to the high thermal conductivity of graphene, it can rapidly heat up the external environment, significantly improving the thermal response speed and heat dissipation efficiency of the ceramic material.

[0041] Compared with existing technologies, the preparation method of this invention can easily form a graphene modified layer on the surface of a ceramic matrix without changing its properties, giving the original ceramic products new application value and improving their service life and market competitiveness.

[0042] Compared with existing technologies, the composite material prepared by this invention has good mechanical properties, effectively improves the brittleness and fracture toughness of ceramic materials, enhances the impact resistance of materials, and expands its application range in high-end fields.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A method for preparing graphene-modified electrically heated ceramics, characterized in that: The preparation method of the graphene-modified electric heating ceramic includes: Step 1: Prepare graphite slurry; Step 2: Encapsulation preparation of graphite slurry and ceramic matrix; Step 3: Electrochemical preparation of graphene; Step 4: Post-processing.

2. The preparation method of graphene-modified electrically heated ceramics according to claim 1, characterized in that: Step 1 includes: Step 101: Calcining the expanded graphite at a low temperature under an inert atmosphere to remove impurities; Step 102: Place the graphite that has been calcined at low temperature into water, add a dispersant and sulfate, and perform shearing and emulsification to prepare a graphite slurry. The dispersant is selected from one or more of the following: silane coupling agent, polyethylene glycol, silica sol, methylcellulose, and aluminum dihydrogen phosphate. The sulfate is selected from one or more of the following: sodium sulfate, ammonium sulfate, potassium sulfate, cobalt sulfate, nickel sulfate, stannous sulfate, and ferrous sulfate. Step 103: Perform ultrasonic treatment on the graphite slurry from step 102 to ensure uniform dispersion of the graphite material.

3. The method for preparing graphene-modified electrically heated ceramics according to claim 1, characterized in that: Step 2 includes: Step 201: Place the graphite slurry prepared in step 1 and the honeycomb ceramic together in a tubular container, with the inner diameter of the tubular container being slightly larger than the outer diameter of the honeycomb ceramic. Step 202: Place the honeycomb ceramic into the tubular container to ensure it is in full contact with the graphite slurry; Step 203: Using the two ends of the tubular container as electrodes, apply direct current to prepare graphene electrochemically at a voltage of 20-30V and 0.1-1A for 30-60 minutes.

4. The tubular container is insulated in the middle and conductive at both ends. When energized, the current flows from one end to the other through the graphite slurry. Under the combined action of the current and sulfate, the graphite undergoes a chemical reaction. On the one hand, the edges of the graphite are oxidized, and on the other hand, the sulfate is intercalated between the graphite sheets to form a graphene precursor. This method directly grows graphene in situ on the ceramic surface, with good bonding force with the ceramic and uniform distribution, without the need for subsequent mixing processing.

5. The method for preparing graphene-modified electrically heated ceramics according to claim 3, characterized in that: Step 3 includes: Step 301: After the graphene precursor in step 203 is prepared, immediately place the tubular container in an ultrasonic tank for ultrasonic exfoliation at a frequency of 40-60kHz and a power of 200-400W. Step 302: Remove the ceramic after ultrasonic peeling and let it air dry naturally; Step 303: Coat both ends of the ceramic with conductive silver paste.

6. The method for preparing graphene-modified electrically heated ceramics according to claim 4, characterized in that: Step 4 includes: Step 401: The ceramic coated with conductive silver paste is calcined at high temperature in an inert atmosphere at 600-800℃ for 1-2 hours. Step 402: After naturally cooling to room temperature, measure the resistance value of the ceramic; Step 403: Adjust the coating thickness of the conductive silver paste according to the measured resistance value.

7. The method for preparing graphene-modified electrically heated ceramics according to claim 3, characterized in that: The honeycomb ceramic is selected from one or more of cordierite, alumina, and silicon dioxide.