Graphene thick film electric heating element and preparation method and application thereof

Abstract

The invention discloses a graphene thick film electric heating element and a preparation method and application thereof. The graphene thick film electric heating element comprises a base material, an inner insulating dielectric layer, a conductor layer, a graphene resistance layer and an outer insulating dielectric layer which are sequentially arranged. And the graphene resistance layer is obtained by sintering high-temperature graphene resistance paste. The graphene water-based slurry has good thermal conductivity, uneven heating caused by limitation of a printing process can be relieved, graphene is a carbon material, the resistance value can be accurately corrected through laser resistance trimming, and the product resistance consistency is higher; the high-temperature graphene resistance paste is sintered to serve as a resistance heating layer on the graphene thick film electric heating element, the power density of the high-temperature graphene resistance paste exceeds 30-250 W / cm < 2 > and is far higher than that of an existing graphene electric heating film, and meanwhile the problem of high-temperature migration does not exist.

Description

Technical Field

[0001] This application relates to the field of electrothermal materials technology, and in particular to a graphene thick film electrothermal element, its preparation method and application. Background Technology

[0002] Thick-film heating technology, including thick-film heating plates, heating tubes, and other heating elements, is a replacement for traditional electric heating devices. It features small size, rapid heating rate, high thermal efficiency, and uniform heating. Thick-film heating elements are classified by their substrate material into metallic and non-metallic types, and by shape into cylindrical and planar types. Non-metallic planar elements are mostly made of microcrystalline or alumina ceramic plates. Due to their structural characteristics, sealing is difficult, and they generally do not directly contact the water during boiling. Instead, they heat water through a pot or kettle. They have poor thermal conductivity and are generally used for lower-power boiling, with a power density not exceeding 10 W / cm³. 2 Metallic flat or round tubes are easy to process, have good sealing and thermal conductivity, and can directly heat water on their inner walls, thus achieving a power density of 30-250W / cm³. 2 It has a high heating rate. Existing thick-film heaters use precious metal pastes such as silver, palladium, and ruthenium for the resistive layer, which is screen-printed and sintered, resulting in very high costs.

[0003] In existing instantaneous heaters, the heating element is mostly a rare-earth thick-film electric heating element, and the resistive heating layer is mostly made of precious metals such as silver, palladium, and ruthenium. Because of their precious metal composition, they are very expensive, resulting in a high cost for rare-earth thick-film electric heating elements. Among them, the resistive heating layer of silver and palladium thick-film electric heating elements is prone to damage due to its low sheet resistance and series circuit configuration.

[0004] Therefore, developing a low-cost resistive paste for preparing thick-film electrothermal elements is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, this application provides a graphene thick film electrothermal element with a heating power density exceeding 30-250 W / cm². 2 It is far superior to current graphene electrothermal films and does not have the problem of high-temperature migration.

[0006] Graphene is a type of carbon atom arranged in sp... 2 Two-dimensional carbon nanomaterials with a hexagonal honeycomb lattice composed of hybrid orbitals. Due to its unique structure and properties, such as high electron mobility, high thermal conductivity, and high strength, graphene has broad application prospects in various fields, especially in the manufacturing of heating elements. Graphene is widely used in heating and heat dissipation due to its excellent electrical and thermal conductivity. However, currently, most graphene applications use resin as a binder, primarily in low-temperature, low-power-density heating films. Even when used on microcrystals, the power density is below 3 W / cm². 2 .

[0007] This application provides a graphene thick film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially.

[0008] The graphene resistive layer is obtained by printing high-temperature graphene resistive paste and then sintering it.

[0009] The high-temperature graphene resistive slurry comprises, by weight, 20 to 30 parts of graphene aqueous slurry, 40 to 60 parts of 800-degree glass powder, and 10 to 30 parts of organic carrier.

[0010] The solid content of the graphene aqueous slurry is from 5 wt% to 20 wt%.

[0011] In some specific implementations, the graphene resistive layer is composed of 2 to 50 graphene circuits connected in parallel;

[0012] The spacing between graphene circuits in the graphene resistive layer is 0.01 mm to 1 mm; the sheet resistance of the graphene resistive layer is 20 Ω / □ to 60 Ω / □.

[0013] In some specific implementations, the viscosity of the graphene aqueous slurry is 60 Pa·s to 100 Pa·s; the organic carrier includes one or more of butyl carbitol, hydrogenated rosin, or dodecyl alcohol ester; and the diameter of the graphene sheet used as the raw material for the graphene aqueous slurry is 1 μm to 10 μm.

[0014] In some specific implementations, the conductor layer is obtained by sintering electrode paste;

[0015] The electrode paste includes one or more of silver electrode paste, silver-platinum electrode paste, or silver-palladium electrode paste.

[0016] In some specific implementations, the thickness of the inner insulating dielectric layer is 80 μm to 130 μm; the thickness of the conductor layer is 7 μm to 15 μm; the thickness of the graphene resistive layer is 7 μm to 15 μm; and the thickness of the outer insulating dielectric layer is 25 μm to 35 μm.

[0017] This application also provides a method for preparing a graphene thick-film electrothermal element, comprising:

[0018] A graphene thick-film electrothermal element is obtained by sequentially printing and sintering an inner insulating dielectric paste to form an inner insulating dielectric layer, printing and sintering an electrode paste to form a conductor layer, printing and sintering a high-temperature graphene resistive paste to form a graphene resistive layer, and printing and sintering an outer insulating dielectric paste to form an outer insulating dielectric layer.

[0019] In some specific implementations, in the process of printing and sintering high-temperature graphene resistive paste to form a graphene resistive layer, the thickness of the graphene resistive layer before sintering is 20-30 μm; the sintering includes drying, debinding, and melt sintering; the drying temperature is 120℃ to 180℃, the drying time is 10 minutes to 20 minutes, the debinding temperature is 330℃ to 550℃, the debinding time is 10 minutes to 20 minutes, the melt sintering temperature is 800℃ to 850℃, the melt sintering time is 5 minutes to 20 minutes, and the melt sintering is carried out under inert gas protection.

[0020] In some specific implementations, the sintering temperature in the printed and sintered electrode paste forming the conductor layer is 120°C to 850°C, and the sintering time is 15 min to 40 min.

[0021] In some specific implementations, after the high-temperature graphene resistive paste is printed and sintered to form a graphene resistive layer, if the sheet resistance of the graphene resistive layer is >60Ω / □, the high-temperature graphene resistive paste is printed and sintered again; if the sheet resistance of the graphene resistive layer is <20Ω / □, laser trimming is performed.

[0022] This application also provides an instant heating device, including a graphene thick film electrothermal element prepared as described above or according to the preparation method described above.

[0023] This application utilizes an aqueous graphene paste with excellent thermal conductivity, which can alleviate uneven heating caused by limitations in the printing process. Graphene, being a carbon material, allows for precise correction of resistance values ​​using laser trimming, resulting in stronger resistance consistency in the product. High-temperature graphene resistance paste is used and sintered to form the resistive heating layer on the graphene thick-film heating element, achieving a power density exceeding 30-250 W / cm². 2 It is far superior to current graphene electrothermal films, and it does not have the problem of high-temperature migration. Attached Figure Description

[0024] Figure 1 A cross-sectional view of the graphene thick film electrothermal element provided in this application;

[0025] Figure 2 A planar unfolded view of the printed coating of the graphene thick film electrothermal element provided in this application. Detailed Implementation

[0026] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0027] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0028] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions may be performed simultaneously.

[0029] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0030] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0031] This application provides a graphene thick film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially.

[0032] The graphene resistive layer is obtained by printing high-temperature graphene resistive paste and then sintering it.

[0033] The high-temperature graphene resistive slurry comprises, by weight, 20 to 30 parts of graphene aqueous slurry, 40 to 60 parts of 800-degree glass powder, and 10 to 30 parts of organic carrier.

[0034] The solid content of the graphene aqueous slurry is from 5 wt% to 20 wt%.

[0035] The high-temperature graphene resistive slurry includes an aqueous graphene slurry. In some specific implementations, the solid content of the aqueous graphene slurry is from 5 wt% to 20 wt%, and can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, 16 wt%, 18 wt%, or 20 wt%. The viscosity of the aqueous graphene slurry is from 60 Pa·s to 100 Pa·s, and can be 60 Pa·s, 65 Pa·s, 70 Pa·s, 75 Pa·s, 80 Pa·s, 85 Pa·s, 90 Pa·s, 95 Pa·s, or 100 Pa·s. The mass fraction of the aqueous graphene slurry is from 20 parts to 30 parts, and can be 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, or 30 parts. The preparation method of the graphene aqueous slurry includes: 1) Pre-dispersion: Deionized water, dispersant, pH adjuster and defoamer are mixed. After the dispersant is completely dissolved, expanded graphite powder is added and dispersed evenly to form a viscous high-solids graphite slurry; 2) Ultra-high pressure jet stripping in a homogenizing valve: The pre-dispersed slurry is passed through a high-pressure homogenizing device. The slurry undergoes shearing, cavitation and impact under high-speed jet, and is fully stripped and broken before being discharged; 3) Concentration: After the high-solids slurry is mixed with the jet, the solids content decreases and the viscosity decreases. The slurry with reduced solids content is concentrated and filtered to obtain a viscous slurry, which is then reintroduced into the high-pressure homogenizing device. Pressurization is applied to form an ultra-high pressure jet again, and after discharge, a high-solids content small-diameter graphene aqueous slurry is obtained.

[0036] The high-temperature graphene resistance paste includes 800°C glass powder. The 800°C glass powder is from Foshan Jinggu Technology Co., Ltd., and its model number is HMB4538A. This 800°C glass powder has a melting point of 800°C and, combined with a stainless steel substrate, exhibits better high-temperature resistance, a higher heat load, and stable operation at high temperatures for extended periods. In water boiling applications, where rapid heating is paramount, its superior high-temperature resistance allows for higher power density and faster heating. Furthermore, the more uniform distribution of graphene ensures excellent stability even at high power. The mass fraction of the 800°C glass powder ranges from 40 to 60 parts, specifically 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, and 60 parts.

[0037] The high-temperature graphene resistive paste includes an organic carrier. In some specific implementations, the organic carrier includes, but is not limited to, one or more of butylcarbidol, hydrogenated rosin, or dodecyl alcohol ester. This application does not have specific requirements for the selection of the organic carrier. The organic carrier is present in parts by weight from 10 to 30, and can be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, or 30 parts.

[0038] This application uses graphene aqueous slurry, not graphene powder, to avoid the need to add leveling agents. Compared with graphene powder, graphene has better dispersibility in slurry, has excellent leveling properties, and its viscosity can be directly adjusted by organic solvents without the need for other additives. In addition, because graphene has better dispersibility in aqueous slurry, graphene is more evenly dispersed during printing, resulting in more uniform heating effect of the product.

[0039] The cross-sectional view of the graphene thick film electric heating element provided in this application is as follows: Figure 1 As shown, the planar unfolded diagram of the printed coating of the graphene thick film electrothermal element is as follows. Figure 2As shown, 1 represents the substrate, which is a high-temperature resistant stainless steel material, including but not limited to one or more of 4-series stainless steel, 430, 444, 443, or 445. This application does not have specific requirements for the selection of the substrate. The thickness of the substrate is 0.6-4 mm. Because it is a stainless steel metal substrate, and all processes are sintered at 750-850 degrees Celsius, the graphene resistive layer, with graphene and a glassy glaze layer interconnected, has higher temperature resistance, stronger strength, and longer lifespan than traditional graphene electric heating films (graphene and resin slurry coated onto a thin film and baked at low temperature). The performance of the thick film is consistent; 2 is an inner insulating dielectric layer, obtained by sintering an inner insulating dielectric slurry, which includes 4-series stainless steel insulating dielectric slurry, such as ESL's 4924 or other domestic slurries with the same performance, and the thickness of the inner insulating dielectric layer is 80μm to 130μm; between 2 and 4, there is also a conductor layer 3 (the conductor layer includes electrode circuits, which are not shown in the cross-sectional view of the graphene thick film heating element), which is obtained by sintering an electrode slurry, and the electrode slurry includes, but is not limited to, one or more of silver electrode slurry, silver-platinum electrode slurry, or silver-palladium electrode slurry. This application... There are no special requirements for the selection of electrode paste. The thickness of the conductor layer is 7μm to 15μm, preferably 15μm. The printing width of the electrode circuit is 2~3mm, and the electrode paste width is printed according to the magnitude of the current during operation. 4 is a graphene resistor layer, which consists of 2 to 50 graphene circuits connected in parallel. The graphene resistors are connected through the conductor layer. The spacing between the graphene circuits in the graphene resistor layer is 0.01mm to 1mm. The sheet resistance of the graphene resistor layer is 20Ω / □ to 60Ω / □, and its circuit configuration is parallel. Through the glassy glaze layer connection, the strength is higher. The tcr of the graphene heating resistor paste is -1100~1300ppm / ℃. The thickness of the graphene resistor layer after sintering is 7μm to 15μm. 5 is the outer insulating dielectric layer, which is obtained by sintering the outer insulating dielectric paste. The outer insulating dielectric paste includes 4-series stainless steel paste with sintering parameters of 650-800 degrees, preferably 750 degrees. The thickness of the outer insulating dielectric layer is 25μm to 35μm. It can protect the graphene resistor layer and conductive circuit, prevent the long-term effects of humidity, oxidation and other external environmental factors, and protect the strength of the graphene resistor layer.

[0040] This application also provides a method for preparing a graphene thick-film electrothermal element, comprising:

[0041] A graphene thick-film electrothermal element is obtained by sequentially printing and sintering an inner insulating dielectric paste to form an inner insulating dielectric layer, printing and sintering an electrode paste to form a conductor layer, printing and sintering a high-temperature graphene resistive paste to form a graphene resistive layer, and printing and sintering an outer insulating dielectric paste to form an outer insulating dielectric layer.

[0042] This application first prints and sintersties an inner insulating dielectric paste on the substrate surface to form an inner insulating dielectric layer. In some specific implementations, the sintering temperature is 120°C to 850°C, and the sintering time is 5 min to 40 min, preferably 10 min. In some specific implementations, after printing the inner insulating dielectric paste, it is dried at 120°C to 180°C, debinded at 330°C to 550°C, and sintered at a peak temperature of 850°C. The sintering is carried out in air and repeated 3-4 times to ensure that the corresponding thickness requirement is achieved.

[0043] This application then prints and sinters electrode paste on the surface of the inner insulating dielectric layer to form a conductor layer. In some specific implementations, the sintering temperature is 120°C to 850°C, and the sintering time is 5 min to 40 min, preferably 10 min. In some specific implementations, after printing the electrode paste, it is dried at 120°C to 180°C, debinded at 330°C to 550°C, and sintered at a peak temperature of 850°C. The drying time is 10 min to 20 min, and the debinding time is 10 min to 20 min. The sintering is carried out in air and repeated 3-4 times to ensure that the corresponding thickness requirement is achieved.

[0044] This application then prints and sintersects a high-temperature graphene resistive paste on the conductive layer surface to form a graphene resistive layer. In some specific implementations, the graphene resistive layer is 20 μm to 30 μm thick before sintering during the printing and sintering of the high-temperature graphene resistive paste. The sintering process includes drying, debinding, and melt sintering. The drying temperature is 120°C to 180°C, and the drying time is 10 to 20 minutes. The debinding temperature is 330°C to 550°C, and the debinding time is 10 to 20 minutes. The melt sintering temperature is 800°C to 850°C, and the melt sintering time is 5 to 20 minutes. The melt sintering is carried out under an inert gas atmosphere, which includes, but is not limited to, nitrogen. This application does not have specific requirements for the selection of the inert gas. Oxygen is introduced during debinding, and the oxygen content is controlled between 600 ppm and 3000 ppm. High-temperature graphene resistive paste is screen-printed using a 165-mesh steel wire screen with a film thickness of 25µm. The conductive layer is covered according to the pattern, and the paste is then placed in an atmosphere-controlled mesh belt furnace for drying and sintering. The sintering is carried out under an inert gas atmosphere, including but not limited to nitrogen and / or argon. This application does not have specific requirements for the choice of inert gas. The debinding stage also requires a micro-oxygen environment with an oxygen content of 600ppm to 3000ppm. After the high-temperature graphene resistive paste is printed and sintered to form a graphene resistive layer, if the sheet resistance of the graphene resistive layer is >60Ω / □, the high-temperature graphene resistive paste is printed and sintered again; if the sheet resistance of the graphene resistive layer is <20Ω / □, laser resistance adjustment is performed; if the resistance is too high, another layer of graphene resistive paste is printed. The sheet resistance parameters of the second printed graphene resistive paste can be selected according to the resistance deviation, and it is sintered again to achieve the desired resistance value. When the resistance is too low, it can be adjusted by laser trimming. Select a 50W fiber laser and choose a laser power range of 20-50% according to the resistance deviation. Polish the graphene surface as a whole. Select different types of laser trimming equipment according to the shape of the heating element to adjust to the required precise resistance.

[0045] This application then prints and sintersects an external insulating dielectric paste on the surface of the graphene resistive layer to form an external insulating dielectric layer, thereby obtaining a graphene thick-film electrothermal element. In some specific implementations, after printing the external insulating dielectric paste, it is dried at 120°C to 180°C, debinded at 330°C to 550°C, and sintered at a peak temperature of 750°C. The drying time is 10 to 20 minutes. The sintering is carried out under inert gas protection, which includes, but is not limited to, nitrogen and / or argon. This application does not have special requirements for the selection of inert gas. The debinding stage also requires a micro-oxygen environment with an oxygen content of 600 ppm to 3000 ppm.

[0046] This application also provides an instant heating device, including the above-described graphene thick film electric heating element or a graphene thick film electric heating element prepared according to the above-described preparation method. In some specific implementations, the instant heating device includes devices that can be used in heating fields such as household appliances, industrial appliances, and new energy vehicles, such as instant water dispensers, steam boilers, wall-hung boilers, and HVCH heaters for new energy vehicles.

[0047] The graphene resistive layer prepared with the water-based graphene slurry used in this application has a sheet resistance of 20~60Ω / □. When connected in parallel to form a circuit, even if one circuit burns out due to uneven heating, the overall heating function remains unaffected. Furthermore, graphene's excellent thermal conductivity reduces uneven heating caused by limitations in the printing process. As a carbon material, graphene's resistance value can be precisely corrected using laser trimming, resulting in stronger resistance consistency in the product. Using 800°C high-temperature graphene resistive slurry, sintered as the resistive heating layer on the graphene thick-film heating element, its power density exceeds 30-250W / cm². 2 It is far superior to current graphene electrothermal films, and it does not have the problem of high-temperature migration.

[0048] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0049] Example 1

[0050] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0051] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0052] Step Two: An insulating dielectric paste is screen-printed onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is used. The thickness of the insulating dielectric paste is 30µm. It is then placed in a high-temperature air-mesh conveyor belt oven and dried at 180°C for 10 minutes. The paste is then degassed at 330-550°C (using a segmented heating method, a conventional technique in this field) for 20 minutes. Finally, it is sintered at a peak temperature of 850°C for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated three times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0053] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0054] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 24 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 10%wt, viscosity 70Pa.s, graphene sheet diameter 5μm for preparing the graphene aqueous paste), 50 parts of 800°C glass powder, and 26 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 1,4-diol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0055] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. Measuring the graphene resistance, the value of 38Ω is too high. Repeating step 4, another graphene resistive layer is printed and sintered, yielding a resistance of 20Ω. Laser trimming is then performed using a 50W fiber laser at 20% power to uniformly polish the graphene resistive layer, correcting the resistance to 28.8Ω.

[0056] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire screen. The paste thickness is 25µm, covering both layers and leaving the solder joints of the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section). The mixture is then debonded at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm), and sintered at a peak temperature of 750°C for 10 minutes under nitrogen atmosphere protection to form the outer insulating dielectric layer.

[0057] A graphene thick-film heating element with dimensions of Φ20*0.8*120mm was obtained, exhibiting a resistance of 28.8±1Ω. Performance testing was conducted on this graphene thick-film heating element. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on a 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2 The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0058] Example 2

[0059] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0060] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0061] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0062] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0063] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 24 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 15%wt, viscosity 80Pa.s, graphene sheet diameter 5μm for preparing the graphene aqueous paste), 50 parts of 800°C glass powder, and 26 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 12-ol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0064] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. The measured resistance of graphene is 28 ohms. Using laser trimming with a 50W fiber laser at 5% power, the graphene resistive layer is uniformly polished to correct the graphene resistance to 28.8Ω.

[0065] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire screen. The paste thickness is 25µm, covering both layers and leaving the solder joints of the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section). The mixture is then debonded at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm), and sintered at a peak temperature of 750°C for 10 minutes under nitrogen atmosphere protection to form the outer insulating dielectric layer.

[0066] A graphene thick-film heating element with dimensions of Φ20*0.8*120mm was obtained, exhibiting a resistance of 28.8±1Ω. Performance testing was conducted on this graphene thick-film heating element. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on a 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0067] Example 3

[0068] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0069] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0070] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0071] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0072] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 24 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 20%wt, viscosity 90Pa.s, graphene sheet diameter 5μm for preparing the graphene aqueous paste), 50 parts of 800°C glass powder, and 26 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 12-ol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0073] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. The measured resistance of the graphene is 22 ohms. Using laser trimming with a 50W fiber laser at 16% power, the graphene resistive layer is uniformly polished to correct the graphene resistance to 28.8Ω.

[0074] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire mesh. The paste thickness is 25µm, covering both layers and leaving the solder joints on the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section), followed by debinding at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm). Melting and sintering are then performed at the peak temperature of 750°C under nitrogen atmosphere protection for 10 minutes, forming the outer insulating dielectric layer. This yields a graphene thick-film heating element with dimensions of Φ20*0.8*120mm and a resistance of 28.8±1Ω. Performance testing of this graphene thick-film heating element was conducted. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on the 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2 The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0075] Example 4

[0076] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0077] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0078] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0079] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0080] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 20 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 5%wt, viscosity 65Pa.s, graphene sheet diameter of 10μm used to prepare the graphene aqueous paste), 60 parts of 800°C glass powder, and 20 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 12-ol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0081] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. The measured resistance of the graphene is 80Ω, which is too high. Repeating step 4, the resistance of two layers of graphene is measured at 38Ω. Repeating step 4 again, the resistance of three layers of graphene is 25Ω. Using laser trimming with a 50W fiber laser at 15% power, the graphene resistive layer is uniformly polished, correcting the graphene resistance to 28.8Ω.

[0082] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire mesh. The paste thickness is 25µm, covering both layers and leaving the solder joints on the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section), followed by debinding at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm). Melting and sintering are then performed at the peak temperature of 750°C under nitrogen atmosphere protection for 10 minutes, forming the outer insulating dielectric layer. This yields a graphene thick-film heating element with dimensions of Φ20*0.8*120mm and a resistance of 28.8±1Ω. Performance testing of this graphene thick-film heating element was conducted. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on the 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2 The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0083] Example 5

[0084] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0085] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0086] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0087] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0088] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 30 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 5%wt, viscosity 60Pa.s, graphene sheet diameter 5μm for preparing the graphene aqueous paste), 40 parts of 800°C glass powder, and 30 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 1,4-ol ester dodecyl in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0089] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. Measuring the graphene resistance at 50 ohms, and repeating Step 4, the resistance of two graphene layers was measured at 24.5Ω. Using laser trimming with a 50W fiber laser at 10% power, the graphene resistance layer was uniformly polished to correct the graphene resistance to 28.8Ω.

[0090] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire screen. The paste thickness is 25µm, covering both layers and leaving the solder joints of the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section). The mixture is then debonded at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm), and sintered at a peak temperature of 750°C for 10 minutes under nitrogen atmosphere protection to form the outer insulating dielectric layer.

[0091] A graphene thick-film heating element with dimensions of Φ20*0.8*120mm was obtained, exhibiting a resistance of 28.8±1Ω. Performance testing was conducted on this graphene thick-film heating element. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on a 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2 The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0092] Example 6

[0093] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0094] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0095] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0096] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0097] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 20 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 15%wt, viscosity 85Pa.s, graphene sheet diameter 10μm), 60 parts of 800°C glass powder, and 20 parts of organic carrier (butyl carbitol, hydrogenated rosin, and dodecyl alcohol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0098] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. The measured resistance of the graphene is 30Ω. Repeating Step 4, the resistance of the two graphene layers is measured at 16Ω. Using laser trimming with a 50W fiber laser at 5% power, the graphene resistive layer is uniformly polished to correct the graphene resistance to 28.8Ω.

[0099] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire mesh. The paste thickness is 25µm, covering both layers and leaving the solder joints on the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section), followed by debinding at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm). Melting and sintering are then performed at the peak temperature of 750°C under nitrogen atmosphere protection for 10 minutes, forming the outer insulating dielectric layer. This yields a graphene thick-film heating element with dimensions of Φ20*0.8*120mm and a resistance of 28.8±1Ω. Performance testing of this graphene thick-film heating element was conducted. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on the 20*120mm stainless steel tube was 42cm². 2The surface heat load is calculated to be 50 W / cm². 2 The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0100] Example 7

[0101] This embodiment provides a graphene thick-film electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The fabrication method of the graphene thick-film electrothermal element includes:

[0102] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0103] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0104] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0105] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 30 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 15%wt, viscosity 70Pa.s, graphene sheet diameter 1μm for preparing the graphene aqueous paste), 40 parts of 800°C glass powder, and 30 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 12-ol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 800°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0106] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. The measured graphene resistance is 23 ohms. Using a 50W fiber laser at 13% power, the graphene resistive layer is uniformly polished to correct the graphene resistance to 28.8Ω.

[0107] Step Six: Finally, a layer of 750°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire screen. The paste thickness is 25µm, covering both layers and leaving the solder joints of the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section). The mixture is then debonded at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm), and sintered at a peak temperature of 750°C for 10 minutes under nitrogen atmosphere protection to form the outer insulating dielectric layer.

[0108] A graphene thick-film heating element with dimensions of Φ20*0.8*120mm was obtained, exhibiting a resistance of 28.8±1Ω. Performance testing was conducted on this graphene thick-film heating element. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on a 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2The graphene thick-film heating element was installed on the assembly, which included a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was conducted with 242V AC power and no water. The manual thermostat tripped normally. After cooling, the test was repeated ten times. The resistance of the graphene thick-film heating element showed no significant change, and its appearance and electrical performance remained consistent with its initial state. Tested according to the national standard GB / T-28204-2011 "Film Heating Elements for Household and Similar Purposes," it meets the national standard performance requirements.

[0109] Comparative Example 1

[0110] This comparative example provides an electric heating element. The only difference between the preparation method of the electric heating element and that of Example 1 is that the 800-degree glass powder is replaced with 600-degree low-melting-point glass powder, and the sintering temperature is 600-650 degrees.

[0111] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0112] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0113] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0114] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 30 parts of graphene aqueous paste from Ningbo Graphene Innovation Center Co., Ltd. (solid content 15%wt, viscosity 80Pa.s, graphene sheet diameter 5μm for preparing the graphene aqueous paste), 40 parts of 600°C glass powder, and 30 parts of organic carrier (butyl carbitol, hydrogenated rosin, and 12-ol ester in a 4:1:1 ratio). The printing thickness is 25µm. Then, place it in an atmosphere mesh belt oven, dry at 180°C for 10 minutes, remove the binder at 330-550°C for 20 minutes, under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm, and melt and sinter at a high temperature of 600°C for 10 minutes to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0115] Step 5: Based on the graphene's tcr = -1100~1300ppm / ℃, and its steady-state resistance of 23Ω at 220V 2100W, with a surface temperature of 180℃, the resistance at room temperature (25℃) is approximately 28.8Ω. Using a 50W fiber laser at 14% power, the graphene resistive layer is uniformly polished to correct the graphene resistance to 28.8Ω.

[0116] Step Six: Finally, a layer of 650°C 4-series stainless steel paste is screen-printed onto the graphene resistive layer and conductor layer using a 165-mesh steel wire screen. The paste thickness is 25µm, covering both layers and leaving the solder joints of the conductor layer exposed. Then, it is placed in an atmosphere-controlled mesh belt oven and dried at 180°C for 10 minutes (air section). The mixture is then debonded at 330-550°C for 20 minutes under nitrogen atmosphere protection (oxygen content 1800-2000ppm), and sintered at a peak temperature of 650°C for 10 minutes under nitrogen atmosphere protection to form the outer insulating dielectric layer.

[0117] A graphene thick-film heating element with dimensions of Φ20*0.8*120mm was obtained, exhibiting a resistance of 28.8±1Ω. Performance testing was conducted on this graphene thick-film heating element. With the heating element sealed at both ends and water flowing through it, and powered by an AC 220V power supply, the measured power was 2100W. The effective heating area of ​​the graphene on a 20*120mm stainless steel tube was 42cm². 2 The surface heat load is calculated to be 50 W / cm². 2 The performance was normal; the graphene thick film heating element was installed on the component, which has a KSD31 ceramic thermostat and a 210-degree manual reset thermostat. A dry-burning test was performed with 242V AC power and no water. After one dry-burning test, there were pits on the graphene surface, the coating layer peeled off, and the resistance of the heating element decreased to 26Ω, making it unable to dry-burn much.

[0118] Comparative Example 2

[0119] This comparative example provides an electrothermal element, comprising a substrate, an inner insulating dielectric layer, a conductor layer, and a graphene resistive layer sequentially disposed therefrom. The method for fabricating the electrothermal element includes:

[0120] Step 1: Using a SUS444 stainless steel tube with a length of 120mm, a diameter of 20mm, and a thickness of 0.8mm as the base material, polish its surface with 400-grit sandpaper and ultrasonically clean it to remove oil and dust.

[0121] Step 2: Screen print the insulating dielectric paste onto the substrate. The insulating dielectric paste is imported ESL 4924, and a 165-mesh steel wire mesh is selected. The thickness of the insulating dielectric paste is 30µm. Then, place it in a high-temperature air mesh belt oven, dry at 180 degrees Celsius for 10 minutes, remove the paste at 330-550 degrees Celsius for 20 minutes, and then melt and sinter at a peak temperature of 850 degrees Celsius for 10 minutes to form a dense inner insulating dielectric layer. This process is repeated 3 times to ensure that the thickness of the inner insulating dielectric layer reaches 85µm.

[0122] Step 3: Print a layer of silver-platinum electrode paste on the inner insulating dielectric layer. The paste should be 2.6 mm wide and the screen printing mesh should be 200 mesh. The paste thickness should be 15 μm. Then, place it in a high-temperature air mesh belt oven and dry it at 180°C for 10 minutes. Then, remove the adhesive at 330-550°C for 20 minutes. Finally, melt and sinter at a high temperature of 850°C for 10 minutes to form the conductor layer circuit.

[0123] Step 4: Screen print a layer of high-temperature graphene resistive paste onto the conductive layer circuit. Use a 165-mesh steel wire screen. The high-temperature graphene resistive paste, by weight, includes: 30 parts of graphene from Ningbo Graphene Innovation Center Co., Ltd. (solid content 15%wt, viscosity 80 Pa·s, graphene sheet diameter 5μm for preparing the water-based graphene paste), 40 parts of 800-degree glass powder, and organic carriers (butyl carbitol, hydrogenated rosin, and alcohol esters). Two components are prepared in a 4:1:1 ratio (30 parts in total). The printing thickness is 25µm. Then, the components are placed in an air mesh belt oven and dried at 180°C for 10 minutes. The adhesive is removed at 330-550°C for 20 minutes under nitrogen atmosphere protection with an oxygen content of 1800-2000ppm. The components are then melted and sintered at a high temperature of 800°C for 10 minutes with continuous oxygen supply to form a graphene resistive layer. The spacing between each graphene circuit is 0.6mm.

[0124] Step 5: The resistance of the graphene was measured at 600 ohms, which is too high, and the graphene showed significant oxidation, making it unusable. Preliminary power-on testing revealed that the graphene at the electrodes burned out very easily.

[0125] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A graphene thick-film electrothermal element, characterized in that, It includes a substrate, an inner insulating dielectric layer, a conductor layer, a graphene resistive layer, and an outer insulating dielectric layer arranged sequentially. The graphene resistive layer is obtained by printing high-temperature graphene resistive paste and then sintering it. The high-temperature graphene resistive slurry comprises, by weight, 20 to 30 parts of graphene aqueous slurry, 40 to 60 parts of 800-degree glass powder, and 10 to 30 parts of organic carrier. The solid content of the graphene aqueous slurry is from 5 wt% to 20 wt%.

2. The graphene thick film electrothermal element according to claim 1, characterized in that, The viscosity of the graphene aqueous slurry is from 60 Pa·s to 100 Pa·s; the organic carrier includes one or more of butyl carbitol, hydrogenated rosin, or dodecyl alcohol ester; the diameter of the graphene sheet used as the raw material for the graphene aqueous slurry is from 1 μm to 10 μm.

3. The graphene thick film electrothermal element according to claim 1, characterized in that, The graphene resistive layer is composed of 2 to 50 graphene circuits connected in parallel; The spacing between graphene circuits in the graphene resistive layer is 0.01 mm to 1 mm; the sheet resistance of the graphene resistive layer is 20 Ω / □ to 60 Ω / □.

4. The graphene thick film electrothermal element according to claim 1, characterized in that, The conductor layer is obtained by sintering electrode paste; The electrode paste includes one or more of silver electrode paste, silver-platinum electrode paste, or silver-palladium electrode paste.

5. The graphene thick film electrothermal element according to claim 1, characterized in that, The thickness of the inner insulating dielectric layer is 80 μm to 130 μm; the thickness of the conductor layer is 7 μm to 15 μm; the thickness of the graphene resistive layer is 7 μm to 15 μm; and the thickness of the outer insulating dielectric layer is 25 μm to 35 μm.

6. A method for preparing a graphene thick-film electrothermal element, characterized in that, include: A graphene thick-film electrothermal element is obtained by sequentially printing and sintering an inner insulating dielectric paste to form an inner insulating dielectric layer, printing and sintering an electrode paste to form a conductor layer, printing and sintering a high-temperature graphene resistive paste to form a graphene resistive layer, and printing and sintering an outer insulating dielectric paste to form an outer insulating dielectric layer.

7. The preparation method according to claim 6, characterized in that, After the graphene resistive layer is formed by printing and sintering the high-temperature graphene resistive paste, if the sheet resistance of the graphene resistive layer is >60Ω / □, the high-temperature graphene resistive paste is printed and sintered again; if the sheet resistance of the graphene resistive layer is <20Ω / □, laser trimming is performed.

8. The preparation method according to claim 6, characterized in that, In the process of printing and sintering high-temperature graphene resistive paste to form a graphene resistive layer, the thickness of the graphene resistive layer before sintering is 20μm to 30μm; the sintering includes drying, debinding, and melt sintering; the drying temperature is 120℃ to 180℃, the drying time is 10 minutes to 20 minutes, the debinding temperature is 330℃ to 550℃, the debinding time is 10 minutes to 20 minutes, the melt sintering temperature is 800℃ to 850℃, the melt sintering time is 5 minutes to 20 minutes, and the melt sintering is carried out under inert gas protection.

9. The preparation method according to claim 6, characterized in that, In the process of printing and sintering the electrode paste to form a conductor layer, the sintering temperature is from 120°C to 850°C, and the sintering time is from 15 min to 40 min.

10. An instant heating device, characterized in that, It includes the graphene thick film heating element as described in any one of claims 1 to 5 or the graphene thick film heating element prepared according to the preparation method described in any one of claims 6 to 9.

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