Preparation method of adjustable resistance heating plate and application thereof

Abstract

The application provides a preparation method of a heating plate with adjustable resistance and application thereof, and comprises the following operations: dispersing a porous graphene-carbon nanotube hybrid in a solvent, adding a silicone polymer precursor, and grinding after mixing to obtain a slurry; coating the slurry on a substrate to form a coating area, arranging at least one high-temperature sintering area and at least one low-temperature sintering area in the coating area, and respectively sintering the high-temperature sintering area and the low-temperature sintering area, and the sintering temperature of the high-temperature sintering area is greater than that of the low-temperature sintering area; and obtaining the heating plate. The preparation method of the heating plate with adjustable resistance provided by the application prepares the slurry by using the porous graphene-carbon nanotube hybrid and the silicone polymer precursor, forms a uniform conductive network by means of the porous structure of the hybrid, and guarantees film formation and bonding strength; the same coating area is sintered in sections, high and low surface resistance areas are formed by using temperature differences, and the integrated conductive layer reduces thermal stress, thereby simplifying the process and significantly improving the reliability of the heating plate.

Description

Technical Field

[0001] This invention relates to the field of heating plate technology, and in particular to a method for preparing an adjustable resistance heating plate and its application. Background Technology

[0002] In electronic devices and heating equipment with heating plates, the heating plates typically require coating structures with different surface resistance zones to achieve zoned functions (such as zoned heating). Traditional methods for preparing such coatings often rely on adjusting the formulation of the conductive paste, changing the coating thickness, or using complex processes such as multiple coatings and step-by-step drying to achieve differences in surface resistance in different areas. This is not only cumbersome and time-consuming, but also prone to causing poor performance consistency across different areas, thus affecting product reliability. Summary of the Invention

[0003] To address the issues of complex processes and low product reliability in existing technologies for achieving different surface resistances on the same coating surface of a heating plate, a method for preparing an adjustable resistance heating plate and its application are provided.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] On one hand, the present invention provides a method for preparing a heating plate with adjustable resistance, comprising the following operations:

[0006] Graphene and carbon nanotubes were mixed, dispersed in water, and an etchant was added. The mixture was then reacted at high temperature to obtain a porous graphene-carbon nanotube hybrid.

[0007] The porous graphene-carbon nanotube hybrid was dispersed in a solvent, an organosilicon polymer precursor was added, and the mixture was ground to obtain a slurry.

[0008] A slurry is coated onto a substrate to form a coating area. At least one high-temperature sintering area and at least one low-temperature sintering area are provided in the coating area. The high-temperature sintering area and the low-temperature sintering area are sintered separately, and the sintering temperature of the high-temperature sintering area is greater than that of the low-temperature sintering area.

[0009] Obtain the heating plate;

[0010] The sintering temperature of the low-temperature sintering zone is 450~550℃, and the sheet resistance is 500~1000 ohms / cube.

[0011] The sintering temperature of the high-temperature sintering zone is 550~800℃, and the surface resistivity is 50~500 ohms / cube.

[0012] Optionally, the mass ratio of graphene to carbon nanotubes is 1:(0.2~5).

[0013] Optionally, the etching agent includes one or more of a strong oxidant and a strong base;

[0014] The strong oxidizing agent includes one or more of nitric acid, hydrogen peroxide, perchloric acid, and potassium permanganate; and / or,

[0015] The strong base includes one or more of sodium hydroxide and potassium hydroxide.

[0016] Optionally, the mass ratio of the porous graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:(5~50).

[0017] Optionally, the organosilicon polymer precursor includes one or more of polycarbosilane, polysiloxane, polysilazane, polysiloxane, and polysiloxane.

[0018] Optionally, the solvent includes one or more of toluene and xylene; and / or,

[0019] The substrate includes one or more of alumina ceramic plates, zirconia ceramic plates, and microcrystalline glass plates.

[0020] Optionally, the slurry comprises the following components by mass:

[0021] 1 part graphene

[0022] 0.2-5.0 parts of carbon nanotubes

[0023] 6-100 parts of organosilicon polymer precursor

[0024] 0.1-0.5 parts of auxiliary agent

[0025] 1-5 parts of filler.

[0026] Optionally, the slurry includes additives and fillers, the additives including silane coupling agents, the silane coupling agents including one or more of KH550, KH560, and KH570; and / or,

[0027] The filler includes one or more of alumina, silicon carbide, and silicon oxide;

[0028] The thickness of the slurry coating is 40~200μm.

[0029] On the other hand, the heating plate prepared by the heating plate preparation method provided by the present invention can be used in heating devices.

[0030] The beneficial effects of this application are as follows:

[0031] In the method for preparing the heating plate provided in this application, a porous graphene-carbon nanotube hybrid is used as the conductive substrate, and a slurry is prepared in combination with an organosilicon polymer precursor. The porous structure of the hybrid can form a uniform conductive network, and the organosilicon precursor provides good film-forming properties and bonding strength with the substrate for the slurry. Simultaneously, by setting high-temperature and low-temperature sintering zones in the same coating area and implementing zoned sintering, the microstructure of the conductive layer is controlled by the sintering temperature. The high-temperature sintering zone, due to its higher sintering temperature, allows for more complete cross-linking, curing, and carbonization of the organosilicon polymer precursor, while also allowing the conductive network of the porous graphene-carbon nanotube hybrid to form a tighter contact, reducing the contact resistance of the conductive pathway and thus obtaining a low surface resistivity region. The low-temperature sintering zone, due to its lower sintering temperature... The low cross-linking and curing degree of the organosilicon precursor, the weak carbonization degree, and the relatively low contact density of the conductive network result in higher contact resistance and thus a high surface resistivity region. The partitioned sintering in this preparation method does not require multiple coatings, etchings, or doping modifications on the same coating surface. Different surface resistivity regions can be constructed simply by controlling the sintering temperature after coating. Furthermore, the entire conductive layer is formed by coating the same uniform slurry in one go, and the sintering regions are integrated structures, avoiding problems such as poor interlayer bonding and interface cracking caused by multiple coatings. The temperature gradient control during partitioned sintering can also reduce the concentration of thermal stress inside the conductive layer, ensuring the structural continuity and stability of different surface resistivity regions on the same coating surface of the heating plate, and significantly improving the reliability of the product. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a heating plate structure provided in an embodiment of the present invention;

[0033] Figure 2 This is a product drawing of a heating plate provided in an embodiment of the present invention;

[0034] Figure 3 This is a thermal imaging image of the heating plate provided in Embodiment 1 of the present invention.

[0035] The reference numerals in the accompanying drawings are as follows:

[0036] 1. Substrate; 2. Coating area; 21. High-temperature sintering area; 22. Low-temperature sintering area; 3. Heating plate. Detailed Implementation

[0037] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0038] This invention provides a method for preparing a heating plate with adjustable resistance, comprising the following operations:

[0039] Graphene and carbon nanotubes were mixed, dispersed in water, and an etchant was added. The mixture was then reacted at high temperature to obtain a porous graphene-carbon nanotube hybrid.

[0040] The porous graphene-carbon nanotube hybrid was dispersed in a solvent, an organosilicon polymer precursor was added, and the mixture was ground to obtain a slurry.

[0041] A slurry is coated onto a substrate to form a coating area. At least one high-temperature sintering area and at least one low-temperature sintering area are provided in the coating area. The high-temperature sintering area and the low-temperature sintering area are sintered separately, and the sintering temperature of the high-temperature sintering area is greater than that of the low-temperature sintering area.

[0042] Obtain the heating plate;

[0043] The sintering temperature of the low-temperature sintering zone is 450~550℃, and the sheet resistance is 500~1000 ohms / cube.

[0044] The sintering temperature of the high-temperature sintering zone is 550~800℃, and the surface resistivity is 50~500 ohms / cube.

[0045] Specifically, in the method for preparing an adjustable resistance heating plate provided in this application, a porous graphene-carbon nanotube hybrid is used as the conductive substrate, and a slurry is prepared in combination with an organosilicon polymer precursor. The porous structure of the hybrid can form a uniform conductive network, and the organosilicon precursor provides the slurry with good film-forming properties and bonding strength with the substrate. Simultaneously, by setting high-temperature and low-temperature sintering zones in the same coating area and implementing zoned sintering, the microstructure of the conductive layer is controlled by the sintering temperature. In the high-temperature sintering zone, due to the higher sintering temperature, the organosilicon polymer precursor undergoes more complete cross-linking, curing, and carbonization, while the conductive network of the porous graphene-carbon nanotube hybrid forms a tighter contact, reducing the contact resistance of the conductive pathway and thus obtaining a low surface resistivity region. In the low-temperature sintering zone, due to the higher sintering temperature, the microstructure of the conductive layer is controlled. The lower junction temperature results in a lower degree of cross-linking and curing of the organosilicon precursor, weaker carbonization, and lower contact density of the conductive network, leading to higher contact resistance and the formation of high surface resistivity regions. This preparation method eliminates the need for multiple coatings, etchings, or doping modifications on the same coating surface; different surface resistivity zones can be constructed simply by controlling the sintering temperature after coating. Furthermore, the entire conductive layer is formed by a single coating of the same uniform slurry, creating an integrated structure between the sintering zones. This avoids problems such as poor interlayer bonding and interface cracking caused by multiple coatings. The temperature gradient control during the sintering process also reduces thermal stress concentration within the conductive layer, ensuring the structural continuity and stability of different surface resistivity regions on the same coating surface of the heating plate, significantly improving product reliability.

[0046] Specifically, after mixing and dispersing the graphene and carbon nanotubes, an etchant is added and etched at high temperature to form a porous structure. This preparation method can precisely construct uniform porous channels in the graphene-carbon nanotube composite system. On the one hand, it improves the dispersibility of the hybrid in the organosilicon polymer precursor, avoids the breakage of the conductive network caused by the agglomeration of the conductive substrate, and ensures the uniformity of the overall microstructure of the conductive layer. On the other hand, the porous structure can increase the contact sites of the conductive network, providing a structural prerequisite for subsequent zone sintering to change the density of the conductive network by temperature control and achieve the differentiation of surface resistance. This further improves the accuracy of surface resistance control in different sintering zones. At the same time, the optimized hybrid structure can improve the bonding force between the conductive layer and the organosilicon precursor, and enhance the overall structural stability of the heating plate.

[0047] In some embodiments, the mass ratio of graphene to carbon nanotubes is 1:(0.2~5).

[0048] The mass ratio of graphene to carbon nanotubes is limited to 1:(0.2~5). This ratio range allows the graphene sheets and carbon nanotubes to form a sheet-tube interlaced composite conductive network. The porous structure obtained after etching is uniform and continuous, which not only ensures the conductivity of the hybrid, but also allows it to be well combined with the organosilicon polymer precursor, providing a stable conductive substrate for the subsequent section sintering to control the surface resistance, while improving the structural strength of the conductive layer.

[0049] If the proportion of carbon nanotubes is too low (less than 0.2%), the graphene sheets cannot be effectively connected to form a continuous conductive network, resulting in an excessively high overall resistance of the conductive layer, and the sintering of different areas makes it difficult to achieve effective differentiation of surface resistance.

[0050] If the proportion of carbon nanotubes is too high (greater than 5%), the carbon nanotubes are prone to agglomeration. After etching, the porous structure is prone to problems such as excessively large pores and loose structure, which reduces the structural strength of the conductive layer and the bonding with the substrate, and affects the reliability of the heating plate.

[0051] Specifically, the mass ratio of graphene to carbon nanotubes includes, but is not limited to, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0052] In some embodiments, the etchant comprises one or more of a strong oxidant and a strong base;

[0053] The strong oxidizing agent includes one or more of nitric acid, hydrogen peroxide, perchloric acid, and potassium permanganate; and / or,

[0054] The strong base includes one or more of sodium hydroxide and potassium hydroxide.

[0055] Specifically, the strong oxidants (nitric acid, hydrogen peroxide, etc.) can etch the defect sites of graphene and carbon nanotubes through oxidation to form a uniform microporous structure, while the strong alkalis (sodium hydroxide, potassium hydroxide, etc.) can destroy the carbon-carbon bonds of carbon materials through alkaline etching to achieve the construction of a porous structure. Both types of etchants can be adapted to the preparation conditions of high-temperature reaction, with high etching efficiency and strong controllability of porous structure.

[0056] Choosing one or more of the above-mentioned etchants can play their corresponding positive roles, namely avoiding the problems of over-etching (structural collapse) or under-etching (no effective porous structure) of the hybrid body due to the use of unsuitable etchants, ensuring the consistency of the porous structure of the hybrid body, and avoiding the decrease in the reliability of the heating plate due to defects in the hybrid body structure.

[0057] In some embodiments, the mass ratio of the porous graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:(5~50).

[0058] Specifically, the mass ratio of the porous graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:(5~50). This ratio range allows the organosilicon precursor to fully encapsulate the porous graphene-carbon nanotube hybrid, ensuring both good film-forming properties and substrate bonding strength of the slurry, while also enabling the hybrid to form a continuous conductive network. This provides a balanced substrate system for subsequent zone sintering, allowing temperature control to alter the density of the conductive network and achieve differential surface resistance. Simultaneously, it improves the temperature resistance and aging resistance of the conductive layer, further enhancing the reliability of the heating plate.

[0059] If the proportion of organosilicon precursor is too low (less than 5%), the slurry has poor film-forming properties, and cracking and powdering are likely to occur after coating. Furthermore, it cannot effectively encapsulate the porous graphene-carbon nanotube hybrid, resulting in low bonding strength between the conductive layer and the substrate. The conductive layer is prone to peeling off during the use of the heating plate. If the proportion of organosilicon precursor is too high (greater than 50%), the dispersion of the porous graphene-carbon nanotube hybrid in the slurry is too low, the conductive network is discontinuous, resulting in excessively high overall resistance of the conductive layer. Moreover, it is difficult to achieve effective differentiation of sheet resistance through partitioned sintering.

[0060] Specifically, the mass ratio of the graphene-carbon nanotube hybrid to the organosilicon polymer precursor includes, but is not limited to, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, or 1:50.

[0061] In some embodiments, the sintering temperature of the low-temperature sintering zone is 450~550℃, and the sheet resistance is 500~1000 ohms / cube.

[0062] The sintering temperature of the high-temperature sintering zone is 550~800℃, and the surface resistivity is 50~500 ohms / cube.

[0063] The high-temperature range of 550~800℃ allows the organosilicon precursor to undergo full cross-linking, curing, and deep carbonization, enabling the hybrid conductive network to form tight contact sites, significantly reducing the contact resistance of the conductive path, thereby obtaining a low surface resistance region of 50~500 ohms / square. Furthermore, this temperature range avoids problems such as carbon material oxidation and conductive layer embrittlement caused by excessively high temperatures.

[0064] The low-temperature range of 450~550℃ allows the silicone precursor to undergo moderate cross-linking and curing, with a weaker degree of carbonization. The contact tightness of the conductive network is at a moderate level, and the contact resistance can be controllably increased to a high surface resistance range of 500~1000 ohms / square. At the same time, this temperature range can ensure the basic bonding strength between the conductive layer and the substrate, avoiding problems such as poor film formation and large fluctuations in surface resistance caused by excessively low temperatures.

[0065] Specifically, based on the actual requirements for the heating plate in the manufacturing process, multiple high-temperature sintering zones and multiple low-temperature sintering zones can be formed on the substrate at different sintering temperatures. Therefore, the actual sintering temperature can also be adjusted according to actual needs; as shown in the attached figure. Figure 1 As shown, the two sides of the coating area 2 of the substrate 1 are set as low-temperature sintering areas 22, and the middle area of ​​the substrate is set as a high-temperature sintering area 21. Correspondingly, on the heating plate 3 obtained in the end, the low-temperature sintering area forms a high-resistance area, and the high-temperature sintering area forms a low-resistance area. Further, as in this application... Figure 2 The image shown is of the heating plate product.

[0066] In some embodiments, the organosilicon polymer precursor includes one or more of polycarbosilane, polysiloxane, polysilazane, polysiloxane, and polysiloxane.

[0067] Specifically, the aforementioned organosilicon polymer precursors can all enable the slurry to form a uniform and continuous wet film during coating. During sintering, they can be tightly bonded to the porous graphene-carbon nanotube hybrid and achieve different degrees of cross-linking, curing, and carbonization within the temperature range of partitioned sintering, providing a stable film-forming substrate basis for differentiated control of sheet resistance. At the same time, the suitable organosilicon precursors can improve the temperature resistance, corrosion resistance, and flexibility of the conductive layer, further reducing structural damage during the use of the heating plate and improving product lifespan and reliability.

[0068] In some embodiments, the solvent includes one or more of toluene and xylene.

[0069] Toluene and / or xylene solvents have good compatibility with organosilicon polymer precursors and porous graphene-carbon nanotube hybrids, ensuring uniform dispersion of the hybrids in the solvent and preventing aggregation.

[0070] In some embodiments, the substrate includes one or more of alumina ceramic plates, zirconia ceramic plates, and microcrystalline glass plates.

[0071] Specifically, the substrate is selected from alumina ceramic plates, zirconia ceramic plates, and microcrystalline glass plates. These substrates have the characteristics of high temperature resistance, low coefficient of thermal expansion, and high bonding strength with the organosilicon-based conductive layer. They are suitable for high-temperature processes of partitioned sintering, avoiding deformation and cracking of the substrate during sintering. At the same time, they reduce the thermal stress difference between the substrate and the conductive layer, preventing the conductive layer from falling off. In addition, these substrates have excellent insulation properties, which can ensure the safety of the heating plate.

[0072] In some embodiments, the slurry comprises the following components by mass:

[0073] 1 part graphene

[0074] 0.2-5.0 parts of carbon nanotubes

[0075] 6-100 parts of organosilicon polymer precursor

[0076] 0.1-0.5 parts of auxiliary agent

[0077] 1-5 parts of filler.

[0078] By limiting the specific mass ratio of each component in the above slurry, the synergistic effect of each component is achieved. Specifically, the ratio of graphene to carbon nanotubes is adapted to construct a porous hybrid conductive network. The ratio of organosilicon polymer precursor takes into account the film-forming properties of the slurry, the bonding strength with the substrate, and the continuity of the conductive network. The precise ratio of additives and fillers further optimizes the dispersibility and leveling properties of the slurry, and improves the hardness, wear resistance, and thermal expansion matching of the conductive layer. The proportions of each component are adapted to each other to achieve the control of high and low surface resistivity in different regions, while ensuring the structural stability and reliability of the conductive layer of the heating plate.

[0079] In some embodiments, the slurry includes additives and fillers, the additives including silane coupling agents, the silane coupling agents including one or more of KH550, KH560, and KH570; and / or,

[0080] The filler includes one or more of alumina, silicon carbide, and silicon oxide;

[0081] The thickness of the slurry coating is 40~200μm.

[0082] Specifically, the additives are selected from silane coupling agents (KH550, KH560, KH570). These coupling agents can chemically bond with both inorganic conductive hybrids (graphene-carbon nanotubes) and organosilicon precursors, thereby improving the dispersibility and compatibility of the hybrids in the slurry and enhancing the bonding strength between the conductive layer and the substrate, thus preventing the conductive layer from falling off.

[0083] Alumina, silicon carbide, and silicon oxide are selected as fillers. These inorganic fillers can optimize the microstructure of the conductive layer, improve its hardness, wear resistance, and high temperature resistance, and adjust the thermal expansion coefficient of the conductive layer to better match the substrate, reduce thermal stress concentration, and prevent the conductive layer from cracking.

[0084] The slurry coating thickness is limited to 40~200μm. This thickness range ensures that the conductive layer has sufficient structural strength and conductivity, avoiding the easy damage and large fluctuations in surface resistance caused by excessively thin thickness (less than 40μm), while avoiding insufficient drying after coating and easy bubbles and cracking during sintering caused by excessively thick thickness (greater than 200μm). At the same time, this thickness range is suitable for temperature control of zone sintering, ensuring the accuracy of surface resistance control in different sintering zones, and further improving the product yield and reliability of the heating plate.

[0085] In another embodiment, the heating plate prepared by the adjustable resistance heating plate preparation method provided by the present invention is used in a heating device.

[0086] Specifically, when the heating device uses the heating plate provided in this application, it can achieve precise zoned heating (different surface resistance areas correspond to different heating powers). Simultaneously, the high reliability of the heating plate can improve the service life of the heating device and reduce maintenance costs, solving the problems of poor heating accuracy and short service life caused by the complex surface resistance control and low reliability of traditional heating devices. In the preparation of the heating plate, a porous graphene-carbon nanotube hybrid is used as the conductive substrate, combined with an organosilicon polymer precursor to prepare the slurry. The porous structure of the hybrid can form a uniform conductive network, and the organosilicon precursor provides good film-forming properties and bonding strength with the substrate. Furthermore, by setting high-temperature and low-temperature sintering zones in the same coating area and implementing zoned sintering, the microstructure of the conductive layer can be controlled using the sintering temperature. The higher sintering temperature in the high-temperature sintering zone allows for more complete cross-linking, curing, and carbonization of the organosilicon polymer precursor, while simultaneously allowing… The porous graphene-carbon nanotube hybrid forms a denser conductive network, reducing the contact resistance of the conductive pathway and thus obtaining a low surface resistivity region. Conversely, the low-temperature sintering region, due to its lower sintering temperature, has a relatively lower degree of cross-linking and curing of the organosilicon precursor, weaker carbonization, and a relatively lower contact density of the conductive network, resulting in higher contact resistance and thus forming a high surface resistivity region. This preparation method eliminates the need for multiple coatings, etchings, or doping modifications on the same coating surface; different surface resistivity zones can be constructed simply by controlling the sintering temperature after coating. Furthermore, the entire conductive layer is formed by a single coating of the same uniform slurry, creating an integrated structure between the sintering zones. This avoids problems such as poor interlayer bonding and interface cracking caused by multiple coatings. The temperature gradient control during the zoned sintering process also reduces thermal stress concentration within the conductive layer, ensuring the structural continuity and stability of different surface resistivity regions on the same coating surface of the heating plate, significantly improving product reliability.

[0087] The present invention will be further illustrated by the following examples.

[0088] Table 1

[0089]

[0090] Example 1

[0091] This embodiment illustrates a method for preparing an adjustable resistance heating plate disclosed in this invention, including the following steps:

[0092] One part graphene and one part carbon nanotubes were mixed, dispersed in water, and an etchant (nitric acid) was added. The mixture was reacted at high temperature to obtain a porous graphene-carbon nanotube hybrid.

[0093] The mass ratio of graphene to carbon nanotubes is 1:1.

[0094] The porous graphene-carbon nanotube hybrid was dispersed in a solvent (toluene), and 10 parts of an organosilicon polymer precursor (polycarbosilane) were added. After mixing and grinding, a slurry was obtained.

[0095] The mass ratio of the graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:5.

[0096] The slurry is coated onto the substrate to form a coating area. A high-temperature sintering area and a low-temperature sintering area are set in the coating area. The high-temperature sintering area and the low-temperature sintering area are sintered separately. The sintering temperature of the high-temperature sintering area is 800℃, and the sintering temperature of the low-temperature sintering area is 450℃.

[0097] The slurry coating thickness is 40μm;

[0098] Obtain the heating plate.

[0099] Examples 2-9

[0100] Examples 2-9 illustrate a method for preparing an adjustable resistance heating plate disclosed in this invention, including most of the operations in Example 1, with the following differences:

[0101] In Examples 2-9, the graphene / part, carbon nanotube / part, graphene:carbon nanotube, type of organosilicon polymer precursor, organosilicon polymer precursor / part, graphene-carbon nanotube hybrid:organosilicon polymer precursor, high-temperature sintering zone temperature, low-temperature sintering zone temperature, and slurry coating thickness are all based on Table 1.

[0102] Comparative Example 1

[0103] This comparative example is used to illustrate the method for preparing an adjustable resistance heating plate disclosed in this invention, including most of the operations in Example 1, except that:

[0104] One part of graphene was dispersed in a solvent (toluene), and 10 parts of an organosilicon polymer precursor (polycarbosilane) were added. After mixing and grinding, a slurry was obtained.

[0105] The slurry is coated onto the substrate to form a coating area. A high-temperature sintering area and a low-temperature sintering area are set in the coating area. The high-temperature sintering area and the low-temperature sintering area are sintered separately. The sintering temperature of the high-temperature sintering area is 800℃, and the sintering temperature of the low-temperature sintering area is 450℃.

[0106] The slurry coating thickness is 40μm;

[0107] Obtain the heating plate.

[0108] Comparative Example 2

[0109] This comparative example is used to illustrate the method for preparing an adjustable resistance heating plate disclosed in this invention, including most of the operations in Example 1, except that:

[0110] One part graphene and one part carbon nanotubes were mixed, dispersed in water, and an etchant (nitric acid) was added. The mixture was reacted at high temperature to obtain a porous graphene-carbon nanotube hybrid.

[0111] The mass ratio of graphene to carbon nanotubes is 1:1.

[0112] The porous graphene-carbon nanotube hybrid was dispersed in a solvent (toluene), and 10 parts of an organosilicon polymer precursor (polycarbosilane) were added. After mixing and grinding, a slurry was obtained.

[0113] The mass ratio of the graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:5.

[0114] The paste is coated onto the substrate to form a coating area, and the entire coating area is sintered at a temperature of 600°C. After sintering, different resistance areas are etched out by laser etching to obtain the heating plate.

[0115] The slurry coating thickness is 40μm;

[0116] Obtain the heating plate.

[0117] Performance testing

[0118] Thermal imaging was performed on the heating plate prepared in Example 1 above.

[0119] The heating plate prepared in Example 1 was placed on a heat-insulating pad and powered on (operating voltage 220~380V, adjustable via a transformer). After reaching a stable operating temperature, a FOTRIC326 thermal imager was used to record the temperature of each area. The emissivity was set to 0.95, the ambient temperature was 25℃, and the distance between the thermal imager lens and the sample was 0.5m. The lens was aimed at the boundary between the high-temperature sintering zone and the low-temperature sintering zone to take pictures, obtaining... Figure 3 ;

[0120] in, Figure 3 The temperature on the left is in °C, and the "44.6-283.2" on the right is a temperature-color label bar, which shows the correspondence between different colors and temperatures in thermal imaging. The higher the temperature, the brighter the color, and the lower the temperature, the darker the color.

[0121] Thermal imaging detection was performed on the heating plate provided in Embodiment 1 of this application, such as... Figure 3As shown, the test results reveal a clear temperature difference between zones. The high-temperature sintering zone on the left is a bright area with a measured maximum temperature of 328.6℃, while the low-temperature sintering zone on the right is a dark area with a temperature as low as 197.1℃. The temperature boundary between the two zones is highly consistent with the preset sintering zone boundary. This result verifies the structural characteristics that 800℃ high-temperature sintering results in low surface resistivity in this area, while 450℃ low-temperature sintering results in high surface resistivity in the corresponding area. Under the same operating voltage, the low-resistivity area has higher heating power and more efficient heat energy conversion, while the high-resistivity area does the opposite. That is, while effectively reducing thermal stress concentration, it ensures the stability and accuracy of the zoned heating of the heating plate.

[0122] The following performance tests were performed on Examples 1-9 and Comparative Examples 1-2 prepared above:

[0123] Performance testing standards:

[0124] 1. The surface resistivity was tested using the four-probe method, referring to the standard GB / T 1551-2019. A digital four-probe tester was used for the test, and at least 5 points were tested for each sample, and the average value was taken.

[0125] 2. The coating strength was determined using the cross-cut test (100-grid test), referring to standard GB / T 9286-2021. A multi-blade cross-cut knife was used to cut a 6x6 standard grid in both the horizontal and vertical directions. After applying adhesive tape, the tape was peeled off to test the coating peeling. The judgment grading is listed in Table 2.

[0126] Table 2

[0127]

[0128] Coating strength grade: 0-5 (grade 0 is optimal, no peeling).

[0129] 3. The extreme thermal cycling stability test conditions are -40℃ to 400℃. The low-temperature test uses a cryogenic freezer, and the high-temperature test uses a muffle furnace. The specific test method is as follows: After raising both the cryogenic freezer and the muffle furnace to the specified temperatures (-40℃ and 400℃ respectively), the sample is first placed in the muffle furnace and held for 10 minutes until the temperature stabilizes. Then, it is placed in the cryogenic freezer and held for another 10 minutes. Finally, it is removed and placed back into the muffle furnace. This process constitutes one cycle. After repeating this process 100 times, the surface resistivity of the sample is tested using Method 1, and the rate of change of resistance after 100 cycles is calculated. Surface resistivity unit: Ω / □ (ohms / square).

[0130] The test results obtained by the above test methods are filled in Table 3.

[0131] Table 3

[0132]

[0133] As can be seen from the test results in Table 3, the carbon nanotube ratio needs to be controlled within the range of 1:(0.2~5) of graphene:carbon nanotubes. If the ratio is too high (such as in Example 3, 1:5), it will cause the carbon nanotubes to agglomerate, and the coating strength will only be grade 1 compared to Examples 1 and 2. If the carbon nanotube ratio is too low (such as in Example 6, 1:0.2), it will cause the conductive network to be discontinuous, and the resistance change rate will rise to 4.2% after thermal cycling.

[0134] The mass ratio of the porous graphene-carbon nanotube hybrid to the organosilicon polymer precursor needs to be controlled within the range of 1:(5~50). If the ratio is too high (such as in Example 5, 1:50), it will dilute the conductive network and lead to an increase in sheet resistance. When the ratio is moderate (such as in Examples 1, 2 and 4, the ratio is 1:5~10), the film-forming properties and stability are optimal.

[0135] The thickness of the slurry coating needs to be controlled between 40 and 200 μm. If the thickness is too thick (such as 200 μm in Example 8), it will lead to insufficient drying, a thermal cycling resistance change rate of 9.5-9.6%, and a coating strength of level 2.

[0136] In Examples 1 to 9, by sintering in a high-temperature zone of 550~800℃ and a low-temperature zone of 450~550℃, a stable sheet resistance range of 52~220Ω / □ in the high-temperature zone and 500~950Ω / □ in the low-temperature zone can be obtained. The sheet resistance difference between the sintered areas in the high-temperature zone and the low-temperature zone is 4-10 times, which is significant. This indicates that the heating plate preparation method provided in this application can achieve resistance adjustment after sintering the same coating surface in different zones. Furthermore, the resistance change rate after 100 thermal cycles is mostly less than 4.2%, and the coating strength is still good after multiple cycles.

[0137] In Comparative Example 1 (without carbon nanotubes), only graphene was used as the conductive substrate, which could not form a continuous conductive network. The surface resistivity in the high-temperature region increased to 350 Ω / □, and in the low-temperature region it reached 2400 Ω / □. The thermal cycling resistance change rate was 8.6%, and the coating strength was only level 2, which was far worse than the example.

[0138] In Comparative Example 2 (traditional laser etching process), the traditional process of integral sintering combined with laser etching is adopted. The adjustable range of surface resistivity is narrow (110~180Ω / □), and it is impossible to adjust the resistance of the same heating plate. The usability is poor. After adjusting the resistance by laser etching, the high-resistivity area cannot withstand thermal cycling. The resistance change rate is as high as 30.6%, and cracking and peeling occur in this area. The coating strength drops to level 3, and the reliability is significantly worse than the embodiment provided in this application.

[0139] The specific test results from the above embodiments and comparative examples show that, in the preparation method of the heating plate provided in this application, a porous graphene-carbon nanotube hybrid is used as the conductive substrate, and a slurry is prepared in combination with an organosilicon polymer precursor. The porous structure of the hybrid can form a uniform conductive network, and the organosilicon precursor provides good film-forming properties and bonding strength with the substrate. Simultaneously, by setting high-temperature and low-temperature sintering zones in the same coating area and implementing zoned sintering, the microstructure of the conductive layer is controlled by the sintering temperature. The high-temperature sintering zone, due to its higher sintering temperature, allows for more complete cross-linking, curing, and carbonization of the organosilicon polymer precursor, while simultaneously allowing the conductive network of the porous graphene-carbon nanotube hybrid to form a tighter contact, reducing the contact resistance of the conductive pathway, and thus obtaining a low surface resistance region. Because of the lower sintering temperature, the cross-linking and curing degree of the organosilicon precursor in the low-temperature sintering zone is relatively low, the carbonization degree is weak, the contact density of the conductive network is relatively low, and the contact resistance is higher, thus forming a high surface resistivity region. The partitioned sintering in this preparation method does not require multiple coatings, etchings, or doping modifications on the same coating surface. Different surface resistivity partitions can be constructed simply by controlling the sintering temperature after coating. Secondly, the entire conductive layer is formed by coating the same uniform slurry in one go, and the sintering zones are integrated structures, avoiding problems such as poor interlayer bonding and interface cracking caused by multiple coatings. The temperature gradient control during partitioned sintering can also reduce the thermal stress concentration inside the conductive layer, ensuring the structural continuity and stability of different surface resistivity regions on the same coating surface of the heating plate, and significantly improving the reliability of the product.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a heating plate with adjustable resistance, characterized in that, Includes the following operations: Graphene and carbon nanotubes were mixed, dispersed in water, and an etchant was added. The mixture was then reacted at high temperature to obtain a porous graphene-carbon nanotube hybrid. The porous graphene-carbon nanotube hybrid was dispersed in a solvent, an organosilicon polymer precursor was added, and the mixture was ground to obtain a slurry. A slurry is coated onto a substrate to form a coating area. At least one high-temperature sintering area and at least one low-temperature sintering area are provided in the coating area. The high-temperature sintering area and the low-temperature sintering area are sintered separately, and the sintering temperature of the high-temperature sintering area is greater than that of the low-temperature sintering area. Obtain the heating plate; The sintering temperature of the low-temperature sintering zone is 450~550℃, and the sheet resistance is 500~1000 ohms / cube. The sintering temperature of the high-temperature sintering zone is 550~800℃, and the surface resistivity is 50~500 ohms / cube.

2. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The mass ratio of graphene to carbon nanotubes is 1:(0.2~5).

3. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The etching agent includes one or more of a strong oxidant and a strong base; The strong oxidizing agent includes one or more of nitric acid, hydrogen peroxide, perchloric acid, and potassium permanganate; and / or, The strong base includes one or more of sodium hydroxide and potassium hydroxide.

4. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The mass ratio of the porous graphene-carbon nanotube hybrid to the organosilicon polymer precursor is 1:(5~50).

5. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The organosilicon polymer precursor includes one or more of polycarbosilane, polysiloxane, polysilazane, polysiloxane, and polysiloxane.

6. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The solvent includes one or more of toluene and xylene; and / or, The substrate includes one or more of alumina ceramic plates, zirconia ceramic plates, and microcrystalline glass plates.

7. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The slurry comprises the following components by mass: 1 part graphene 0.2-5.0 parts of carbon nanotubes 6-100 parts of organosilicon polymer precursor 0.1-0.5 parts of auxiliary agent 1-5 parts of filler.

8. The method for preparing an adjustable resistance heating plate according to claim 1, characterized in that, The slurry includes additives and fillers, the additives including silane coupling agents, the silane coupling agents including one or more of KH550, KH560, and KH570; and / or, The filler includes one or more of alumina, silicon carbide, and silicon oxide; The coating thickness of the slurry is 40~200μm.

9. The application of the heating plate prepared by the method for preparing the adjustable resistance heating plate according to any one of claims 1 to 8 in heating devices.

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