Electric heating assembly based on graphene alumina fiber fabric and preparation method thereof

Abstract

The invention relates to the technical field of electric heating assemblies, in particular to an electric heating assembly based on graphene alumina fiber fabric and a preparation method thereof, and the preparation method comprises the following steps: dissolving submicron alumina powder and a binder in a solvent to obtain ceramic slurry; clamping a graphene alumina fiber fabric between two alumina fiber needled felts to form a composite structure, wherein the graphene alumina fiber fabric comprises an alumina fiber fabric and a continuous graphene layer conformally coating the surface of the alumina fiber fabric; the composite structure is placed in the ceramic slurry for vacuum impregnation; after the vacuum impregnation is finished, the composite structure is subjected to heat treatment and sintering in sequence, the heat treatment temperature is lower than the sintering temperature, and the heat treatment is used for removing the solvent in the composite structure. According to the method, the packaging effect on the graphene alumina fiber fabric can be improved, and the service life of the graphene alumina fiber fabric can be prolonged.

Description

Technical Field

[0001] This invention relates to the field of electric heating components, specifically to an electric heating component based on graphene alumina fiber fabric and its preparation method. Background Technology

[0002] Graphene has attracted much attention due to its unique mechanical properties, ultra-high carrier mobility, excellent thermal conductivity, and large specific surface area. Graphene fiber fabrics can be synthesized by high-temperature vapor deposition (HCVD) by combining graphene with flexible, high-strength fiber fabrics. These fabrics show promising applications in ultra-thin electric heating technology. Among them, graphene alumina fiber fabrics, due to their high-temperature resistance, are expected to achieve a steady-state operating temperature exceeding 1100℃. However, graphene is prone to oxidation at high temperatures, leading to rapid aging with prolonged use. Therefore, an encapsulation layer can be formed on the surface of the graphene alumina fiber fabric to encapsulate it, preventing contact between graphene and oxygen in the environment and thus extending its service life.

[0003] However, rapid heating and cooling of graphene alumina fiber fabric can cause the encapsulation layer to peel or crack, affecting the encapsulation effect of the graphene alumina fiber fabric and thus impacting its service life. Summary of the Invention

[0004] In view of this, the present invention provides an electric heating component based on graphene alumina fiber fabric and its preparation method, so as to improve the encapsulation effect of graphene alumina fiber fabric.

[0005] In a first aspect, the present invention provides a method for preparing an electric heating component based on graphene alumina fiber fabric, comprising: Submicron-sized alumina powder and binder are dissolved in a solvent to obtain a ceramic slurry; A composite structure is formed by sandwiching graphene alumina fiber fabric between two alumina fiber needle-punched felts. The graphene alumina fiber fabric includes alumina fiber fabric and a graphene layer that conformally covers the surface of the alumina fiber fabric and is in a continuous state. The composite structure is placed in the ceramic slurry for vacuum impregnation; After the vacuum impregnation is completed, the composite structure is subjected to heat treatment and sintering in sequence. The heat treatment temperature is lower than the sintering temperature. The heat treatment is used to remove the solvent from the composite structure.

[0006] The ceramic sealing layer, alumina fiber needle-punched felt, and graphene alumina fiber fabric formed after sintering the ceramic slurry all contain alumina. This results in a small difference in the coefficients of thermal expansion between the encapsulation structure and the graphene alumina fiber fabric. Therefore, when the graphene alumina fiber fabric undergoes rapid heating and cooling, the volume changes between the encapsulation structure and the graphene alumina fiber fabric are similar, reducing the risk of stress concentration at the interface between the encapsulation structure and the graphene alumina fiber fabric. This reduces the risk of peeling or cracking of the encapsulation structure, thereby improving the encapsulation effect on the graphene alumina fiber fabric and extending its service life. Furthermore, submicron-sized alumina powder has a large surface energy, which can lower the sintering temperature, thus avoiding the adverse effects of excessively high-temperature sintering on the mechanical properties of the graphene alumina fiber fabric.

[0007] In some optional embodiments, the submicron-sized alumina powder consists of a first group of alumina powder to an Nth group of alumina powder with sequentially increasing Dv50, where N is an integer greater than or equal to 2, and the difference in Dv50 between adjacent groups of alumina powder is 50nm~500nm, with the first group of alumina powder having the largest mass proportion.

[0008] In some optional embodiments, N is 3, wherein the Dv50 of the first group of alumina powders is 50nm~150nm, the Dv50 of the second group of alumina powders is 200nm~500nm, and the Dv50 of the third group of alumina powders is 500nm~1000nm.

[0009] In some optional embodiments, the concentration of the first group of alumina powder in the ceramic slurry is 30wt%~40wt%, the concentration of the second group of alumina powder is 10wt%-20wt%, and the concentration of the third group of alumina powder is 10wt%-20wt%.

[0010] In some optional embodiments, the ceramic slurry further contains silica powder and boron oxide powder, wherein the concentration of silica powder is 4wt% to 8wt% and the concentration of boron oxide powder is 1wt% to 3wt%.

[0011] In some optional embodiments, the Dv50 of the silicon oxide powder is 50nm~150nm; the Dv50 of the boron oxide powder is 50nm~150nm.

[0012] In some optional embodiments, the sintering includes a first sintering and a second sintering performed sequentially. The temperature of the first sintering is 900℃~1100℃, and the time is 30min~60min. The temperature of the second sintering is 1200℃~1300℃, and the time is 60min~90min. The vacuum degree during the sintering process is 2×10⁻⁶.-3 Pa~5×10 -3 Pa.

[0013] In some optional embodiments, the binder is an alkaline silica sol, and the concentration of the alkaline silica sol in the ceramic slurry is 5wt%~10wt%.

[0014] In some alternative embodiments, the alkaline silica sol has a pH of 9-11, and the concentration of silica is 10wt% to 50wt%.

[0015] In some alternative embodiments, the porosity of the alumina fiber needle-punched felt is 40% to 60%.

[0016] In some alternative embodiments, the area of ​​the alumina fiber needle-punched felt is larger than the area of ​​the graphene alumina fiber fabric.

[0017] In some optional embodiments, the vacuum degree of the vacuum impregnation is 1 Pa to 10 Pa, and the vacuum impregnation time is 15 min to 30 min.

[0018] In some optional embodiments, the heat treatment includes a first heat treatment and a second heat treatment performed sequentially, wherein the temperature of the first heat treatment is 180°C to 200°C and the time of the first heat treatment is 30 min to 90 min; and the temperature of the second heat treatment is 250°C to 300°C and the time of the second heat treatment is 90 min to 180 min.

[0019] Secondly, the present invention provides an electric heating component based on graphene alumina fiber fabric, comprising graphene alumina fiber fabric, two alumina fiber needled felts, and a ceramic sealing layer; the graphene alumina fiber fabric includes alumina fiber fabric and a graphene layer conformally covering the surface of the alumina fiber fabric and in a continuous state; the two alumina fiber needled felts respectively cover two opposing surfaces of the graphene alumina fiber fabric; the ceramic sealing layer seals the graphene alumina fiber fabric and the alumina fiber needled felts, and at least a portion of the ceramic sealing layer is embedded in the pores of the graphene alumina fiber fabric and the pores of the alumina fiber needled felts, wherein the ceramic sealing layer contains alumina.

[0020] In some alternative embodiments, the ceramic sealing layer also contains boron oxide and silicon oxide.

[0021] In some alternative embodiments, the area of ​​the alumina fiber needle-punched felt is larger than the area of ​​the graphene alumina fiber fabric. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of the present invention, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional view of an electric heating assembly according to an embodiment of the present invention.

[0024] Figure 2 A photograph of the electric heating component in Example 1 after one heating and cooling cycle.

[0025] Figure 3 This is a photograph of the electric heating component in Comparative Example 1 after one heating and cooling cycle.

[0026] Figure 4 The image shows an infrared thermal imaging image of the electric heating component in Example 1 during a thermal cycling test.

[0027] Explanation of reference numerals in the attached figures: 1-Graphene alumina fiber fabric; 2-Alumina fiber needle-punched felt; 3-Ceramic coating; 4-Electrode. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the drawings, not the entire structure.

[0029] In a first aspect, the present invention provides a method for preparing an electric heating component based on graphene alumina fiber fabric, wherein the prepared electric heating component is as follows: Figure 1 As shown, for reference Figure 1 The method for preparing the electric heating component includes: dissolving submicron-sized alumina powder and a binder in a solvent to obtain a ceramic slurry; sandwiching a graphene alumina fiber fabric 1 between two alumina fiber needle-punched felts 2 to form a composite structure, wherein the graphene alumina fiber fabric 1 includes an alumina fiber fabric and a graphene layer conformally covering the surface of the alumina fiber fabric in a continuous state; placing the composite structure in the ceramic slurry for vacuum impregnation; after the vacuum impregnation is completed, the composite structure is subjected to heat treatment and sintering in sequence, wherein the heat treatment temperature is lower than the sintering temperature, and the heat treatment is used to remove the solvent in the composite structure.

[0030] During the vacuum impregnation process, the ceramic slurry penetrates into the pores of the graphene alumina fiber fabric 1 and the alumina fiber needled felt 2. After heat treatment and sintering, the submicron-sized alumina powder in the ceramic slurry forms an interconnected continuous polycrystalline structure, which is connected to the graphene alumina fiber fabric 1 and the alumina fiber needled felt 2 to form a whole. The alumina fiber needled felt and the ceramic sealing layer formed after the ceramic slurry are sintered together constitute the encapsulation structure of the graphene alumina fiber fabric 1. The ceramic sealing layer, alumina fiber needle-punched felt 2, and graphene alumina fiber fabric 1 all contain alumina, which makes the difference in the coefficient of thermal expansion between the encapsulation structure and the graphene alumina fiber fabric 1 small. Therefore, when the graphene alumina fiber fabric 1 is rapidly heated or cooled, the volume change between the encapsulation structure and the graphene alumina fiber fabric 1 is similar, reducing the risk of stress concentration at the interface between the encapsulation structure and the graphene alumina fiber fabric 1. This reduces the risk of peeling or cracking of the encapsulation structure, thereby improving the encapsulation effect of the graphene alumina fiber fabric 1 and helping to extend its service life.

[0031] The sintering temperature of conventional alumina materials exceeds 1600℃, and sintering at this temperature will cause a serious decline in the mechanical properties of the graphene alumina fiber fabric 1. However, submicron-sized alumina powder has a large surface energy, which can lower the sintering temperature and thus avoid the adverse effects of excessively high-temperature sintering on the mechanical properties of the graphene alumina fiber fabric 1.

[0032] If sintering is carried out directly without heat treatment, the solvent in the ceramic slurry will evaporate rapidly during the sintering process, which will cause the encapsulation structure to crack, which is not conducive to the encapsulation effect of the encapsulation structure on the graphene alumina fiber fabric 1.

[0033] The following provides a clear and complete illustration of the preparation method of the electric heating component: Step S1: Dissolve submicron alumina powder and binder in a solvent to obtain ceramic slurry.

[0034] Submicron-sized alumina powder and binder can be added to a solvent and then mixed by magnetic stirring. The stirring speed can be 400 r / min to 700 r / min, such as 400 r / min, 500 r / min, 600 r / min, 700 r / min, etc., and the stirring time can be 6 h to 12 h, such as 6 h, 9 h, 12 h, etc.

[0035] The submicron-sized alumina powder can be composed of a first group of alumina powders to an Nth group of alumina powders with sequentially increasing Dv50, where N is an integer greater than or equal to 2. The difference in Dv50 between adjacent groups of alumina powders is 50nm to 500nm, with the first group of alumina powders having the largest mass proportion. Dv50 represents the volume median particle size. Using multiple groups of alumina powders with different particle size distributions, and with the first group of alumina powders having the smallest Dv50 having the largest mass proportion, can increase the powder packing density in the composite structure after vacuum impregnation, reduce the gaps between powders in the composite structure, thereby reducing the shrinkage stress generated during sintering and further reducing the risk of cracking in the encapsulation structure. For example, the difference in Dv50 between adjacent groups of alumina powders can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., or any range of the above values.

[0036] In some optional embodiments, N is 3. The Dv50 of the first group of alumina powders can be 50nm~150nm, such as 50nm, 75nm, 100nm, 125nm, 150nm, etc., or any range of the above values; the Dv50 of the second group of alumina powders can be 200nm~500nm, such as 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., or any range of the above values; the Dv50 of the third group of alumina powders can be 500nm~1000nm, such as 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, etc., or any range of the above values.

[0037] In the ceramic slurry, the concentration of the first group of alumina powder can be 30wt%~40wt%, such as 30wt%, 32wt%, 34wt%, 35wt%, 36wt%, 38wt%, 40wt%, etc., or any range of the above values; the concentration of the second group of alumina powder can be 10wt%-20wt%, such as 10wt%, 12wt%, 14wt%, 15wt%, 16wt%, 18wt%, 20wt%, etc., or any range of the above values; the concentration of the third group of alumina powder can be 10wt%-20wt%, such as 10wt%, 12wt%, 14wt%, 15wt%, 16wt%, 18wt%, 20wt%, etc., or any range of the above values.

[0038] In some optional embodiments, the ceramic slurry may also contain silica powder and boron oxide powder. The sintering type of alumina powder is solid-state sintering, with no liquid phase throughout the process; densification is achieved solely through solid-phase atomic diffusion, resulting in a high sintering temperature. Boron oxide powder can lower the sintering temperature of alumina through a liquid-phase sintering mechanism. However, the glassy liquid phase formed by boron oxide softens at high temperatures, leading to a decrease in the high-temperature strength of the encapsulation structure. The addition of silica powder can introduce a mullite phase through a chemical reaction, thereby improving the high-temperature strength of the encapsulation structure. That is, silica powder and boron oxide powder can form a eutectic aluminoborosilicate glass phase with alumina powder at around 1000℃, effectively reducing the sintering temperature of the alumina powder and preventing excessively high sintering temperatures from causing thermal damage to the graphene alumina fiber fabric 1, thus helping to maintain the excellent electrothermal properties of the graphene alumina fiber fabric 1.

[0039] Meanwhile, the liquid phase formed by silicon oxide powder and boron oxide powder at high temperature can also inhibit the growth of alumina grains, thereby refining the microstructure. This not only improves the strength and thermal shock resistance of the encapsulation structure, but also enhances the matching degree between the high-temperature performance of the encapsulation structure and the rapid heating and cooling characteristics of the graphene alumina fiber fabric 1.

[0040] Furthermore, based on the fluidity of the liquid phase, the liquid phase can fill the pores of the alumina powder, further improving the density of the encapsulation structure, thereby further improving the encapsulation effect of the encapsulation structure on the graphene alumina fiber fabric 1, improving the isolation effect against oxygen, and reducing the risk of oxidation of the graphene alumina fiber fabric 1.

[0041] The concentration of the silica powder can be 4wt% to 8wt%, such as 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, or any range thereof; the concentration of the boron oxide powder can be 1wt% to 3wt%, such as 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or any range thereof. Insufficient addition of silica and boron oxide powder will not effectively reduce the sintering temperature; excessive addition will reduce the matching degree of thermal expansion coefficients between the ceramic sealing layer formed after sintering and the graphene alumina fiber fabric 1; furthermore, excessive boron oxide powder will lead to excessive volatilization during sintering, resulting in a porous structure in the ceramic sealing layer, which is detrimental to the sealing effect of the encapsulation structure. By limiting the concentrations of silica and boron oxide powder within the above ranges, the structural stability and sealing effect of the encapsulation structure can be improved while effectively reducing the sintering temperature.

[0042] The Dv50 of the silicon oxide powder can be 50nm~150nm, such as 50nm, 75nm, 100nm, 125nm, 150nm, etc., or any range of the above values; the Dv50 of the boron oxide powder can be 50nm~150nm, such as 50nm, 75nm, 100nm, 125nm, 150nm, etc., or any range of the above values. The nanoscale size of the silicon oxide and boron oxide powders facilitates the formation of a liquid phase during sintering, thereby inhibiting the growth of alumina grains. The Dv50 of the silicon oxide powder and the Dv50 of the boron oxide powder can be the same or different. The Dv50 of the silicon oxide powder and / or the boron oxide powder can be the same as that of the first group of alumina powders.

[0043] The binder can be an alkaline silica sol. Conventional organic binders such as polyvinyl butyral and polyacrylamide contain oxygen-containing functional groups, which can oxidize graphene and affect the service life of the electric heating component. Alkaline silica sol is an inorganic binder and does not have oxidizing properties, thus avoiding oxidation of graphene. Furthermore, during sintering, the alkaline silica sol transforms into silica. Silica has high high-temperature stability, enabling stable bonding between structures. Moreover, the silica generated after sintering is homogeneously bonded to alumina, improving the density of the encapsulation structure.

[0044] The pH value of the alkaline silica sol can be 9-11, such as 9, 9.5, 10, 10.5, 11, or any range of the above values; the concentration of silica in the alkaline silica sol can be 10wt%~50wt%, such as 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, or any range of the above values.

[0045] The concentration of the alkaline silica sol in the ceramic slurry can be 5wt% to 10wt%, such as 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc., or any range of the above values.

[0046] The solvent for ceramic slurry can be water or the like.

[0047] Step S2: The graphene alumina fiber fabric 1 is sandwiched between two alumina fiber needle-punched felts 2 to form a composite structure. The graphene alumina fiber fabric 1 includes an alumina fiber fabric and a graphene layer conformally covering the surface of the alumina fiber fabric in a continuous state.

[0048] Alumina fiber needle-punched felt 2 serves as the molding skeleton for ceramic slurry, capable of bearing and fixing the ceramic slurry, forming the initial shape and size basis of the encapsulation structure, thereby affecting the shape and size of the electric heating component.

[0049] The porosity of the alumina fiber needle-punched felt 2 can be 40%~60%, such as 40%, 45%, 50%, 55%, 60%, or any range thereof. Submicron-sized alumina powder in the ceramic slurry that permeates into the pores of the graphene alumina fiber fabric 1 and the alumina fiber needle-punched felt 2 will form an interconnected continuous polycrystalline structure after sintering, connecting the graphene alumina fiber fabric 1 and the alumina fiber needle-punched felt 2 into a whole. The porosity of the alumina fiber needle-punched felt 2 directly affects the density of the continuous polycrystalline structure within the alumina fiber needle-punched felt 2 after sintering, thus affecting the connection strength between the alumina fiber needle-punched felt 2 and the graphene alumina fiber fabric 1. By limiting the porosity of the alumina fiber needle-punched felt 2 to the above range, a greater connection strength can be achieved between the alumina fiber needle-punched felt 2 and the graphene alumina fiber fabric 1, and the alumina fiber needle-punched felt 2 is less prone to peeling.

[0050] The area of ​​the alumina fiber needle-punched felt 2 is larger than the area of ​​the graphene alumina fiber fabric 1. Specifically, the length of the alumina fiber needle-punched felt 2 is greater than the length of the graphene alumina fiber fabric 1, and the width of the alumina fiber needle-punched felt 2 is greater than the width of the graphene alumina fiber fabric 1. This ensures that the graphene alumina fiber fabric 1 is located within the formed encapsulation structure after sintering, which is beneficial for improving the encapsulation effect of the graphene alumina fiber fabric 1. The difference in length between the alumina fiber needle-punched felt 2 and the graphene alumina fiber fabric 1 can be 2cm-4cm, and the difference in width between the alumina fiber needle-punched felt 2 and the graphene alumina fiber fabric 1 can be 2cm-4cm.

[0051] The thickness of the alumina fiber needle-punched felt 2 can be selected according to the thickness of the encapsulation structure. For flexible electric heating components, the thickness of the alumina fiber needle-punched felt 2 is 0.5mm-4mm, preferably 1mm-3mm.

[0052] The sheet resistance of the graphene alumina fiber fabric 1 can be 100 Ω / sq-300 Ω / sq; the thickness of the graphene alumina fiber fabric 1 can be 0.2 mm-0.4 mm; the weaving method of the graphene alumina fiber fabric 1 can be plain weave or twill weave; and the areal density is 240 g / m². 2 -320g / m 2 .

[0053] Step S3: Vacuum impregnate the composite structure in the ceramic slurry.

[0054] Vacuum impregnation is performed in a molding mold. Specifically, the composite structure is placed flat in the molding mold, and ceramic slurry is poured into the mold. The slurry can cover the composite structure (0.5mm~1mm) or be flush with it. The molding mold is then placed in a vacuum environment for impregnation. The shape and dimensions of the molding mold are the same as or substantially the same as those of the alumina fiber needle-punched felt 2.

[0055] The vacuum degree of the vacuum impregnation can be 1 Pa to 10 Pa, such as 2 Pa, 5 Pa, 8 Pa, or any range of the above values; the vacuum impregnation time can be 15 min to 30 min, such as 15 min, 20 min, 25 min, 30 min, or any range of the above values.

[0056] Step S4: After the vacuum impregnation is completed, the composite structure is subjected to heat treatment in sequence. The heat treatment is used to remove the solvent in the composite structure.

[0057] The heat treatment may include a first heat treatment and a second heat treatment performed sequentially. The temperature of the first heat treatment is 180℃~200℃, and the time of the first heat treatment is 30min~90min; the temperature of the second heat treatment is 250℃~300℃, and the time of the second heat treatment is 90min~180min. Gradient heat treatment is used to ensure complete removal of the solvent from the composite structure.

[0058] For example, the temperature of the first heat treatment can be 180°C, 190°C, 200°C, etc., or a range of any of the above values; the time of the first heat treatment can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, etc., or a range of any of the above values; the temperature of the second heat treatment can be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, etc., or a range of any of the above values; the time of the second heat treatment can be 90 min, 105 min, 120 min, 135 min, 150 min, 165 min, 180 min, etc., or a range of any of the above values.

[0059] Step S5: Sinter the composite structure, wherein the heat treatment temperature is lower than the sintering temperature.

[0060] The sintering temperature is 1200℃~1300℃, such as 1200℃, 1225℃, 1250℃, 1275℃, 1300℃, etc., or a range of any of the above values.

[0061] When the ceramic slurry contains silicon oxide powder and boron oxide powder, the sintering may include a first sintering and a second sintering performed sequentially. The temperature of the first sintering is 900℃~1100℃, and the time is 30min~60min; the temperature of the second sintering is 1200℃~1300℃, and the time is 60min~90min; the vacuum degree during the sintering process is 2×10⁻⁶. -3 Pa~5×10 -3 Pa. The first sintering stage is used to fully form the aluminum borosilicate eutectic liquid phase, and the second sintering stage is used to densify the alumina powder.

[0062] For example, the first sintering temperature can be 900℃, 950℃, 1000℃, 1050℃, 1100℃, or any range of the above values; the first sintering time can be 30min, 40min, 50min, 60min, or any range of the above values; the second sintering temperature can be 1200℃, 1225℃, 1250℃, 1275℃, 1300℃, or any range of the above values; the second sintering time can be 60min, 70min, 80min, 90min, or any range of the above values.

[0063] refer to Figure 1 The method for preparing the electric heating component further includes: before sandwiching the graphene alumina fiber fabric 1 between two alumina fiber needled felts 2, setting two electrodes 4 on the two opposite edges of the graphene alumina fiber fabric 1 respectively; welding two tabs (not shown) to the two electrodes 4 respectively, with the tabs extending away from the graphene alumina fiber fabric 1; when the graphene alumina fiber fabric 1 is sandwiched between the two alumina fiber needled felts 2, the tabs extend laterally beyond the alumina fiber needled felts 2, and after sintering, the tabs extend laterally beyond the encapsulation structure.

[0064] In some embodiments, electrode 4 is a metal film layer, which can be disposed on the edge of graphene alumina fiber fabric 1 by plasma spraying or electroplating; in other embodiments, electrode 4 is a metal mesh, which can be disposed on the edge of graphene alumina fiber fabric 1 by sewing conductive fibers. The material of electrode 4 includes one or more of nickel, molybdenum, copper molybdenum, and tungsten, and the thickness of electrode 4 can be 80μm-150μm; the width can be 8mm-22mm.

[0065] The electrode tab can be welded to electrode 4 by spot welding, ultrasonic welding, or pulse welding, with spot welding being preferred. The welding power for spot welding can be 2000W-4000W, such as 2000W, 2500W, 3000W, 3500W, 4000W, or any range of the above values. The electrode tab material includes one or more of nickel, molybdenum, copper molybdenum, and tungsten, and the thickness of the electrode tab can be 80μm-150μm, and the width can be 8mm-22mm.

[0066] Secondly, refer to Figure 1 This invention provides an electric heating component based on graphene alumina fiber fabric 1, comprising graphene alumina fiber fabric 1, two alumina fiber needled felts 2, and a ceramic sealing layer (not shown); the graphene alumina fiber fabric 1 includes alumina fiber fabric and a graphene layer conformally covering the surface of the alumina fiber fabric and in a continuous state; the two alumina fiber needled felts 2 respectively cover two opposing surfaces of the graphene alumina fiber fabric 1; the ceramic sealing layer seals the graphene alumina fiber fabric 1 and the alumina fiber needled felts 2, and at least a portion of the ceramic sealing layer is embedded in the pores of the graphene alumina fiber fabric 1 and the pores of the alumina fiber needled felts 2, the ceramic sealing layer containing alumina.

[0067] The preparation method provided in the first aspect can be used to prepare the electric heating component of the second aspect. Therefore, the characteristics (such as materials and dimensions) and effects described in the preparation method for the electric heating component are also applicable to the electric heating component, and will not be repeated here.

[0068] In some alternative embodiments, the ceramic sealing layer also contains boron oxide and silicon oxide.

[0069] In some alternative embodiments, the area of ​​the alumina fiber needle-punched felt 2 is larger than the area of ​​the graphene alumina fiber fabric 1.

[0070] In some alternative implementations, refer to Figure 1 The ceramic sealing layer further includes a ceramic covering layer 3 located on the side of the alumina fiber needle-punched felt 2 facing away from the graphene alumina fiber fabric 1, and the thickness of the ceramic covering layer 3 is 0.4mm-0.8mm.

[0071] refer to Figure 1 The electric heating assembly also includes two electrodes 4 and two tabs. The two electrodes 4 are located at two opposite edges of the graphene alumina fiber fabric 1. The two tabs are welded to the two electrodes 4 respectively. The tabs extend away from the graphene alumina fiber fabric 1 and extend laterally beyond the alumina fiber needle-punched felt 2.

[0072] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0073] Example 1 This embodiment provides a method for preparing an electric heating component, including: Alumina powder with a Dv50 of 100 nm (30 wt%), alumina powder with a Dv50 of 500 nm (15 wt%), alumina powder with a Dv50 of 1000 nm (15 wt%), silica powder with a Dv50 of 100 nm (8 wt%), boron oxide powder with a Dv50 of 100 nm (2 wt%), and alkaline silica sol (5 wt%) were added to water and stirred magnetically at 500 r / min for 8 h to obtain a homogeneous and stable ceramic slurry. The pH value of the alkaline silica sol was 9.5, and the concentration of silica in the alkaline silica sol was 30 wt%. Two electrodes are formed on two opposite edges of the graphene alumina fiber fabric using a plasma spraying process; two tabs are welded to the two electrodes respectively, and the tabs extend away from the graphene alumina fiber fabric. A composite structure is formed by sandwiching graphene alumina fiber fabric between two alumina fiber needled felts. The tabs extend laterally beyond the alumina fiber needled felts. The alumina fiber needled felts have a porosity of 60%, a thickness of 4 mm, and are 2 cm longer and wider than the graphene alumina fiber fabric. Place the composite structure flat in the molding mold, pour ceramic slurry into the molding mold, the ceramic slurry should cover the composite structure by 0.5 mm, and immerse the molding mold at 5 Pa for 30 min.

[0074] The composite structure was heat-treated in an air atmosphere: first at 200℃ for 60 min in a muffle furnace, then at 250℃ for 120 min.

[0075] Sintering of the composite structure: Maintaining a vacuum level of 3.5 × 10⁻⁶ within the vacuum sintering furnace. -3 Pa was heated to 1050℃ at 10℃ / min and held for 45min, then heated to 1200℃ at 10℃ / min and held for 90min to obtain an electric heating component, wherein the surface of the alumina fiber needle-punched felt contains a ceramic covering layer with a thickness of 0.4mm.

[0076] Example 2 The only difference between this embodiment and Embodiment 1 is that "alumina powder with Dv50 of 100nm (30wt%), alumina powder with Dv50 of 500nm (15wt%), and alumina powder with Dv50 of 1000nm (15wt%)" is replaced with "alumina powder with Dv50 of 1000nm (60wt%)".

[0077] Example 3 The only difference between this embodiment and Embodiment 1 is that it does not contain silicon oxide powder and boron oxide powder, and replaces "silicon oxide powder (8wt%) with Dv50 of 100nm and boron oxide powder (2wt%) with Dv50 of 100nm" with aluminum oxide powder (10wt%) with Dv50 of 100nm.

[0078] Example 4 The only difference between this embodiment and Embodiment 1 is that the alkaline silica sol is replaced with polyvinyl butyral.

[0079] Example 5 The only difference between this embodiment and Embodiment 1 is that the porosity of the alumina fiber needle-punched felt is 50%.

[0080] Example 6 The only difference between this embodiment and Embodiment 1 is that the porosity of the alumina fiber needle-punched felt is 40%.

[0081] Example 7 This embodiment provides a method for preparing an electric heating component, including: Alumina powder with a Dv50 of 50 nm (35 wt%), alumina powder with a Dv50 of 200 nm (10 wt%), alumina powder with a Dv50 of 500 nm (10 wt%), silica powder with a Dv50 of 50 nm (4 wt%), boron oxide powder with a Dv50 of 50 nm (2 wt%), and alkaline silica sol (7.5 wt%) were added to water and stirred magnetically at 400 r / min for 12 h to obtain a homogeneous and stable ceramic slurry. The pH value of the alkaline silica sol was 9, and the concentration of silica in the alkaline silica sol was 50 wt%. Two electrodes are formed on two opposite edges of the graphene alumina fiber fabric using a plasma spraying process; two tabs are welded to the two electrodes respectively, and the tabs extend away from the graphene alumina fiber fabric. A composite structure is formed by sandwiching graphene alumina fiber fabric between two alumina fiber needled felts. The tabs extend laterally beyond the alumina fiber needled felts. The alumina fiber needled felts have a porosity of 50%, a thickness of 0.5 mm, and are 4 cm longer and wider than the graphene alumina fiber fabric. Place the composite structure flat in the molding mold, pour ceramic slurry into the molding mold, the ceramic slurry should cover the composite structure by 1 mm, and immerse the molding mold at 5 Pa for 15 min.

[0082] The composite structure was heat-treated in an air atmosphere: first at 180℃ for 90 min in a muffle furnace, then at 250℃ for 90 min.

[0083] Sintering of the composite structure: Maintaining a vacuum level of 5 × 10⁻⁶ within the vacuum sintering furnace. -3 Pa, heated to 900℃ at 10℃ / min and held for 60min, then heated to 1250℃ at 10℃ / min and held for 75min to obtain an electric heating component, wherein the surface of the alumina fiber needle-punched felt contains a ceramic covering layer with a thickness of 0.8mm.

[0084] Example 8 This embodiment provides a method for preparing an electric heating component, including: Alumina powder with a Dv50 of 150 nm (40 wt%), alumina powder with a Dv50 of 400 nm (20 wt%), alumina powder with a Dv50 of 800 nm (20 wt%), silica powder with a Dv50 of 150 nm (8 wt%), boron oxide powder with a Dv50 of 150 nm (3 wt%), and alkaline silica sol (10 wt%) were added to water and stirred magnetically at 700 r / min for 6 h to obtain a homogeneous and stable ceramic slurry. The pH value of the alkaline silica sol was 11, and the concentration of silica in the alkaline silica sol was 10 wt%. Two electrodes are formed on two opposite edges of the graphene alumina fiber fabric using a plasma spraying process; two tabs are welded to the two electrodes respectively, and the tabs extend away from the graphene alumina fiber fabric. A composite structure is formed by sandwiching graphene alumina fiber fabric between two alumina fiber needled felts. The tabs extend laterally beyond the alumina fiber needled felts. The alumina fiber needled felts have a porosity of 40% and a thickness of 2mm. Its length and width are both 3cm greater than the graphene alumina fiber fabric. The composite structure is placed flat in the molding mold, and ceramic slurry is poured into the molding mold, with the ceramic slurry covering the composite structure by 0.8 mm. The molding mold is then immersed in 5 Pa for 20 min.

[0085] The composite structure was heat-treated in an air atmosphere: first at 200℃ for 30 min in a muffle furnace, then at 300℃ for 180 min.

[0086] Sintering of the composite structure: Maintaining a vacuum level of 2×10⁻⁶ within the vacuum sintering furnace. -3Pa was heated to 1100℃ at 10℃ / min and held for 30min, then heated to 1300℃ at 10℃ / min and held for 60min to obtain an electric heating component, wherein the surface of the alumina fiber needle-punched felt contains a ceramic covering layer with a thickness of 0.64mm.

[0087] Comparative Example 1 The only difference between this embodiment and Embodiment 2 is that "alumina powder with Dv50 of 100nm" is replaced with aluminum nitride powder with Dv50 of 100nm, and "alumina fiber needle-punched felt" is replaced with mullite fiber needle-punched felt.

[0088] Performance testing Power density test: Connect the electric heating element (heating area size is 110 mm × 90 mm × 0.28 mm) to the AC frequency converter (Hunan Enzhi Measurement and Control Technology Co., Ltd., model N38318), apply voltage to the electric heating element to obtain power, and calculate the power density according to the formula: power density = power / area.

[0089] Steady-state temperature test: The temperature of the electric heating component is monitored using an infrared thermal imager (Fairer, model A615). When the input power and heat dissipation power reach a dynamic balance, the temperature of the electric heating component itself remains constant. This temperature is recorded as the steady-state temperature of the electric heating component.

[0090] Service life test: The electric heating element is continuously powered on at 1.3 times the rated voltage. The power-on time when the electro-thermal radiation conversion efficiency of the electric heating element reaches 90% of the initial value is recorded. This time is recorded as the service life of the electric heating element.

[0091] Thermal cycling performance test: The temperature of the electric heating component was raised to 700℃ and held for 20 minutes; then the temperature of the electric heating component was lowered to room temperature and held for 20 minutes. The electric heating component was subjected to the above temperature cycling, and the number of cycles when the encapsulation structure cracked was recorded.

[0092] The electric heating components of Examples 1-8 and Comparative Example 1 were tested using the above test steps, and the test results are shown in Table 1.

[0093] Table 1: Test results of Examples 1-8 and Comparative Example 1

[0094] As can be seen from the comparison between Examples 1-8 and Comparative Example 1, using alumina fiber needle-punched felt and alumina powder as the main material of ceramic slurry can improve the encapsulation effect of graphene alumina fiber fabric, enabling the electric heating component to have higher power density and steady-state temperature; it can also improve the heat resistance of the electric heating component, reduce the risk of cracking of the encapsulation structure after repeated temperature changes, and extend the service life of graphene alumina fiber fabric. Figure 2 This is a photograph of the electric heating component in Example 1 after one heating and cooling cycle. Figure 2 The encapsulation structure of the electric heating component was not cracked; Figure 3 This is a photograph of the electric heating component in Comparative Example 1 after one heating and cooling cycle. Figure 3 The encapsulation structure of the electric heating component peeled off and cracked.

[0095] It should be noted that poor encapsulation of graphene alumina fiber fabric can cause graphene to oxidize at high temperatures, thereby reducing its power density and steady-state temperature. If the heat resistance of the electric heating component is poor, the encapsulation structure is prone to cracking after repeated temperature changes, causing the graphene alumina fiber fabric to be exposed to an oxygen-containing environment, thus affecting the service life of the graphene alumina fiber fabric.

[0096] As can be seen from the comparison between Example 1 and Example 2, the ceramic slurry prepared by using multiple groups of alumina powders with different particle size distributions can further improve the encapsulation effect of graphene alumina fiber fabric, enabling the electric heating component to have higher power density and steady-state temperature; it can also further improve the heat resistance of the electric heating component, further reduce the risk of cracking of the encapsulation structure after repeated temperature changes, and extend the service life of graphene alumina fiber fabric.

[0097] A comparison between Example 1 and Example 3 shows that the ceramic slurry contains silicon oxide powder and boron oxide powder, which can further improve the encapsulation effect of graphene alumina fiber fabric, extend the service life of graphene alumina fiber fabric, avoid thermal damage to graphene alumina fiber fabric caused by excessively high sintering temperature, and help maintain the excellent electrothermal performance of graphene alumina fiber fabric.

[0098] As can be seen from the comparison between Example 1 and Example 4, the use of alkaline silica sol as a binder in ceramic slurry can avoid oxidation of graphene, which is beneficial to extending the service life of graphene alumina fiber fabric; and can improve the density and structure of the encapsulation structure.

[0099] Figure 4 The image shown is an infrared thermal imaging image of the electric heating component in Example 1 during a thermal cycling test. Figure 4 It can be seen that the electric heating component can achieve a large-area, stable and uniform heat field distribution, with good temperature uniformity and high heating temperature.

[0100] In this document, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation can be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0102] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0103] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0104] The above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described above, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of protection of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing an electric heating component based on graphene alumina fiber fabric, characterized in that, include: Submicron-sized alumina powder and binder are dissolved in a solvent to obtain a ceramic slurry; A composite structure is formed by sandwiching graphene alumina fiber fabric between two alumina fiber needle-punched felts. The graphene alumina fiber fabric includes alumina fiber fabric and a graphene layer that conformally covers the surface of the alumina fiber fabric and is in a continuous state. The composite structure is placed in the ceramic slurry for vacuum impregnation; After the vacuum impregnation is completed, the composite structure is subjected to heat treatment and sintering in sequence. The heat treatment temperature is lower than the sintering temperature. The heat treatment is used to remove the solvent from the composite structure.

2. The preparation method according to claim 1, characterized in that, The submicron-sized alumina powder consists of a first group of alumina powders to an Nth group of alumina powders with sequentially increasing Dv50, where N is an integer greater than or equal to 2. The difference in Dv50 between adjacent groups of alumina powders is 50nm to 500nm, with the first group of alumina powders having the largest mass proportion.

3. The preparation method according to claim 2, characterized in that, N is 3, where the Dv50 of the first group of alumina powder is 50nm~150nm, the Dv50 of the second group of alumina powder is 200nm~500nm, and the Dv50 of the third group of alumina powder is 500nm~1000nm.

4. The preparation method according to claim 3, characterized in that, In the ceramic slurry, the concentration of the first group of alumina powder is 30wt%~40wt%, the concentration of the second group of alumina powder is 10wt%-20wt%, and the concentration of the third group of alumina powder is 10wt%-20wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The ceramic slurry also contains silicon oxide powder and boron oxide powder, wherein the concentration of silicon oxide powder is 4wt%~8wt% and the concentration of boron oxide powder is 1wt%~3wt%.

6. The preparation method according to claim 5, characterized in that, The Dv50 of the silicon oxide powder is 50nm~150nm; the Dv50 of the boron oxide powder is 50nm~150nm.

7. The preparation method according to claim 5, characterized in that, The sintering process includes a first sintering and a second sintering performed sequentially. The temperature of the first sintering is 900℃~1100℃, and the time is 30min~60min. The temperature of the second sintering is 1200℃~1300℃, and the time is 60min~90min. The vacuum degree during the sintering process is 2×10⁻⁶. -3 Pa~5×10 -3 Pa.

8. The preparation method according to any one of claims 1 to 4, characterized in that, The binder is an alkaline silica sol, and the concentration of the alkaline silica sol in the ceramic slurry is 5wt%~10wt%.

9. The preparation method according to claim 8, characterized in that, The alkaline silica sol has a pH of 9-11 and a silica concentration of 10wt%~50wt%.

10. The preparation method according to any one of claims 1 to 4, characterized in that, The porosity of the alumina fiber needle-punched felt is 40%~60%; and / or, the area of ​​the alumina fiber needle-punched felt is larger than the area of ​​the graphene alumina fiber fabric.

11. The preparation method according to any one of claims 1 to 4, characterized in that, The vacuum degree of the vacuum impregnation is 1 Pa to 10 Pa, and the vacuum impregnation time is 15 min to 30 min; And / or, the heat treatment includes a first heat treatment and a second heat treatment performed sequentially, wherein the temperature of the first heat treatment is 180℃~200℃ and the time of the first heat treatment is 30min~90min; the temperature of the second heat treatment is 250℃~300℃ and the time of the second heat treatment is 90min~180min.

12. An electric heating component based on graphene alumina fiber fabric, characterized in that, include: Graphene alumina fiber fabric, wherein the graphene alumina fiber fabric includes an alumina fiber fabric and a graphene layer conformally coated on the surface of the alumina fiber fabric in a continuous state. Two alumina fiber needle-punched felts, which respectively cover two opposing surfaces of the graphene alumina fiber fabric; A ceramic sealing layer that seals the graphene alumina fiber fabric and the alumina fiber needle-punched felt, wherein at least a portion of the ceramic sealing layer is embedded in the pores of the graphene alumina fiber fabric and the alumina fiber needle-punched felt, and the ceramic sealing layer contains alumina.

13. The electric heating assembly according to claim 12, characterized in that, The ceramic sealing layer also contains boron oxide and silicon oxide, and the area of ​​the alumina fiber needle-punched felt is larger than the area of ​​the graphene alumina fiber fabric.

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