Electric heating film and preparation method thereof

Abstract

The invention discloses an electric heating film and a preparation method thereof. The electric heating film comprises a graphene conductive fabric layer, an electrode, a fabric transition layer and a ceramic packaging coating. The graphene conductive fabric layer is formed by weaving montmorillonite fibers; the fabric transition layers are stacked on the upper surface and the lower surface of the graphene conductive fabric layer respectively, and the fabric transition layers are insulating fiber fabric layers; the ceramic packaging coating is arranged on the surface, far away from the graphene conductive fabric layer, of the fabric transition layer, and part of the ceramic packaging coating is embedded into the graphene conductive fabric layer and the fabric transition layer; the electrode is electrically connected with the graphene conductive fabric layer. According to the invention, the ceramic packaging coating is adopted to package the graphene conductive fabric, so that the defect that an electric heating film cannot realize long-time heating at a high temperature can be overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of electric heating materials, and in particular relates to a ceramic electric heating film based on graphene conductive fabric and a preparation method thereof. Background Art

[0002] Graphene, a carbon nanomaterial in which carbon atoms are arranged in a two-dimensional honeycomb structure, has attracted much attention due to its unique mechanical properties, ultra-high carrier mobility, excellent thermal conductivity and large specific surface area. By means of high-temperature vapor deposition, graphene is compounded with flexible and high-strength fiber fabrics, and the obtained graphene conductive fabrics show good application prospects in the field of ultra-thin electric heating technology. Compared with traditional electric heating materials (for example, iron-chromium alloy wires), graphene electric heating fabrics have many advantages. For example, fast surface heating response (100-200℃ / s), ultra-thinness (~1mm), high emissivity (90%), and flexibility and bendability. However, the easy oxidation of graphene limits the industrial application of this material in the field of medium and high temperature electric heating. Encapsulation with high-temperature resistant and anti-oxidation coating materials is an effective way to solve the above problems.

[0003] Prior art CN117769068A discloses a fabric-based laser-induced graphene electrically heated flexible film, which is obtained by laminating or coating a flexible packaging material on the upper and lower surfaces of a fabric-based laser-induced graphene connected to electrodes for packaging.

[0004] The disadvantages of the existing technology are: (1) the packaging materials are all organic materials, which cannot achieve long-term heating above 300°C; (2) the preparation process is complicated and costly, making it difficult to apply industrially; (3) the heating is uneven and there are many hot spots. Summary of the invention

[0005] In order to overcome at least one of the above-mentioned disadvantages, the present invention provides an electric heating film for solving the oxidation failure problem of the graphene heating film in an environment above 400°C.

[0006] The present invention provides an electric heating film, comprising a graphene conductive fabric layer, an electrode, a fabric transition layer and a ceramic packaging coating; the graphene conductive fabric layer is woven from graphene fibers; the fabric transition layer is stacked on the upper and lower surfaces of the graphene conductive fabric layer, respectively, and the fabric transition layer is an insulating fiber fabric layer; the ceramic packaging coating is arranged on the surface of the fabric transition layer away from the graphene conductive fabric layer and part of the ceramic packaging coating is embedded in the graphene conductive fabric layer and the fabric transition layer; the electrode is electrically connected to the graphene conductive fabric layer.

[0007] According to one embodiment of the present invention, the sheet resistance of the graphene conductive fabric layer is 10-5000Ω / sq, the thickness of the graphene conductive fabric layer is 0.1-0.2mm; and / or the weaving method of the graphene fabric layer is plain or twill.

[0008] According to another embodiment of the present invention, the matrix of the graphene conductive fabric layer and the fabric transition layer respectively include one or more of glass fiber fabric, alumina fiber fabric, aluminum nitride fiber fabric, and mullite fiber fabric.

[0009] According to another embodiment of the present invention, the thickness of the fabric transition layer is 0.2-0.5 mm; and / or the weaving pattern of the fabric transition layer is plain weave or twill weave.

[0010] According to another embodiment of the present invention, the ceramic packaging coating is made of 25% to 33% polysilazane resin, 30% to 40% Al2O3 and 27% to 45% silica sol as raw materials in mass percentage.

[0011] According to another embodiment of the present invention, the thickness of the ceramic packaging coating beyond the adjacent graphene conductive fabric layer is 80-120 μm.

[0012] The present invention also provides a method for preparing the above-mentioned electric heating film, comprising: S1, arranging insulating fabrics on the two surfaces of the graphene conductive fabric layer as the fabric transition layer; S2, mixing ceramic slurry and polysilazane resin to obtain a composite ceramic coating; S3, brushing the composite ceramic coating onto the surface of the fabric transition layer and allowing the composite ceramic coating to be immersed in the graphene fabric layer and the fabric transition layer, and then curing to obtain the electric heating film; wherein the ceramic slurry is a mixture of Al2O3 powder and silica sol.

[0013] According to an embodiment of the present invention, in step S3, the number of times of brushing is 3 to 4 times, with an interval of 10 to 15 minutes between each times.

[0014] According to another embodiment of the present invention, in step S3, the curing temperature is 180-250° C., and the curing time is 45-75 min.

[0015] The present invention uses a ceramic encapsulation coating to encapsulate the graphene conductive fabric, which can solve the defect that the electric heating film cannot achieve long-term heating at high temperature. In addition, in the electric heating film of the present invention, a fabric transition layer is provided between the graphene conductive fabric and the ceramic encapsulation coating, which can improve the pressure resistance and insulation of the encapsulation layer on the one hand; on the other hand, it can increase the bonding force between the graphene conductive fabric and the ceramic encapsulation coating, thereby improving the structural stability of the electric heating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic cross-sectional view of the electric heating film of the present invention.

[0017] Figure 2 It is a schematic diagram of the process of the electric heating film of the present invention.

[0018] Figures 3 to 7 These are infrared thermal imaging photos of the electric heating films prepared in Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION

[0019] The best implementation mode of the present invention is described below through preferred embodiments in conjunction with the accompanying drawings. The specific implementation mode here is to illustrate the present invention in detail and should not be understood as limiting the present invention. Various deformations and modifications can be made without departing from the spirit and essential scope of the present invention, which should be included in the protection scope of the present invention.

[0020] like Figure 1 As shown, the electric heating film of the present invention comprises a graphene conductive fabric layer, an electrode, a fabric transition layer and a ceramic encapsulation coating. The graphene conductive fabric layer is woven from monene fibers. "Monene fibers" refer to composite fibers obtained by directly growing graphene films on substrate fibers by vapor deposition. The fabric transition layers are stacked on the upper and lower surfaces of the graphene conductive fabric layer, and the fabric transition layer is an insulating fiber fabric layer. The ceramic encapsulation coating is arranged on the surface of the fabric transition layer away from the graphene conductive fabric layer, and part of the ceramic encapsulation coating is embedded in the graphene conductive fabric layer and the fabric transition layer (not shown in the figure). The electrode is electrically connected to the graphene conductive fabric layer. The present invention uses a ceramic encapsulation coating to encapsulate the graphene conductive fabric to solve the defect that the electric heating film cannot achieve long-term heating at high temperature. In addition, in the electric heating film of the present invention, a fabric transition layer is arranged between the graphene conductive fabric and the ceramic encapsulation coating. On the one hand, the pressure resistance insulation of the encapsulation layer can be improved; on the other hand, the bonding force between the graphene conductive fabric and the ceramic encapsulation coating can be increased, thereby improving the structural stability of the electric heating film.

[0021] In an optional embodiment, the sheet resistance of the graphene conductive fabric is 10 to 5000 Ω / sq, and the thickness of the graphene conductive fabric is 0.1 to 0.2 mm. The appropriate sheet resistance and thickness can be selected according to actual needs, such as power and other factors. The weaving method of the graphene conductive fabric can be plain or twill. At the same thickness, plain weave has better tensile properties than twill weave fabrics, so plain weave is preferred.

[0022] In an optional embodiment, the matrix and fabric transition layer of the graphene conductive fabric include one or more of glass fiber fabric, alumina fiber fabric, aluminum nitride fiber fabric, and mullite fiber fabric.

[0023] In an optional embodiment, the thickness of the fabric transition layer is 0.2 to 0.5 mm. The transition layer fabric can improve the toughness and pressure-resistant insulation of the electric heating film. If the thickness of the fabric transition layer is too large (greater than 0.5 mm), more ceramic slurry will be required, resulting in a heavier product weight, which cannot reflect the "lightweight" feature, and the ceramic packaging coating is prone to cracking due to high stress, which will also affect the heating efficiency. If the thickness of the fabric transition layer is too low (less than 0.2 mm), the pressure-resistant insulation of the electric heating film will be affected, and the coating will also easily crack as the temperature rises and falls during use. The weaving method of the fabric transition layer can also be plain or twill.

[0024] In an optional embodiment, the ceramic encapsulation coating is made of 25% to 33% polysilazane resin, 30% to 40% Al2O3 and 27% to 45% silica sol as raw materials in mass percentage. The silica sol and polysilazane resin in the raw materials are used as binders, and the Al2O3 powder is used as aggregate in the coating. After curing, a composite ceramic composed of Si-CN amorphous ceramics, Al2O3 and SiO2 is obtained. The ceramic encapsulation coating obtained by the content ratio of the three substances within the above range has good thermal shock resistance, density and temperature resistance.

[0025] In an optional embodiment, the thickness of the ceramic encapsulation coating is 80 to 120 μm beyond the adjacent graphene conductive fabric layer. If this thickness is too large (greater than 120 μm), the product weight value is too large, the coating stress is large and easy to crack, and it will affect the heating efficiency. If the thickness is too small (less than 80 μm), it will affect the product's pressure resistance and insulation, and the coating will also be prone to cracking as the temperature rises and falls during use.

[0026] In an optional embodiment, the electrode electrically connected to the graphene conductive fabric may be a copper sheet welded to the edge of the graphene conductive fabric, or may be an electrode of other metals in any other appropriate connection manner.

[0027] like Figure 2 As shown, the preparation method of the above-mentioned electric heating film may include: S1, arranging insulating fabrics as fabric transition layers on the two surfaces of the graphene conductive fabric layer respectively; S2, mixing ceramic slurry and polysilazane resin to obtain a composite ceramic coating; S3, brushing the composite ceramic coating onto the surface of the fabric transition layer and filling the composite ceramic coating into the graphene fabric layer and the fabric transition layer, and then curing to obtain the electric heating film; wherein the ceramic slurry is a mixture of Al2O3 powder and silica sol.

[0028] In step S1, insulating fabrics can be provided on the upper and lower surfaces of the graphene conductive fabric as a fabric transition layer. The fabric transition layer is an insulating fiber fabric layer. The toughness and pressure-resistant insulation of the electric heating film can be improved by providing this layer.

[0029] In step S2, the ceramic slurry and polysilazane resin are weighed in a certain ratio and mixed evenly to obtain a composite ceramic coating. The ceramic slurry is a mixture of alumina powder and silica sol. The polysilazane resin can be selected to be a polysilazane polymer that is liquid at room temperature and can be converted into Si-CN amorphous ceramic after curing. The composite ceramic coating can be formed by mixing by electromagnetic stirring, with a rotation speed of 200-350r / min, a temperature of 45-60°C, and a stirring time of 30-60min.

[0030] In step S3, the composite ceramic coating can be applied to the surface of the fabric transition layer by brushing multiple times. The specific number of brushing times can be 3 to 4 times, with an interval of 10 to 15 minutes each time. The density and uniformity of the coating can be improved by brushing multiple times. After the coating is completed, the coating is cured at a curing temperature of 180 to 250° C. and a curing time of 45 to 75 minutes. A ceramic encapsulation coating of a composite ceramic composed of Si-CN amorphous ceramics, Al2O3 and SiO2 is formed by curing.

[0031] The present invention is further described below by specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention. In the following examples and comparative examples, the reagents, materials and instruments used are commercially available unless otherwise specified. Among them, the polysilazane resins used are all products with the brand name ZG-511B of Zhongsi New Materials (Quanzhou) Co., Ltd.

[0032] Example 1

[0033] S1: A graphene conductive fabric with a sheet resistance of 200±10Ω / sq, a thickness of 0.1mm, and a twill weave is used. Copper powder is sprayed on both ends of the graphene conductive fabric by plasma spraying to form a copper electrode, and then a spot welder is used to weld a nickel sheet to lead out the electrode at the edge of the copper electrode. Subsequently, a layer of glass fiber fabric is laid on each of the upper and lower surfaces of the graphene conductive fabric as an insulating transition layer.

[0034] S2: The composition of the composite coating is as follows: 30% polysilazane resin, 30% alumina, and 40% silica sol by mass percentage. The composite coating is mixed by electromagnetic stirring, with the speed set at 300 r / min, the temperature set at 50°C, and the stirring time set at 40 min, and finally a uniformly mixed ceramic coating is obtained.

[0035] S3: Apply the coating to the surface of the graphene conductive fabric by brushing for 3 times, with an interval of 10 minutes between each application. Place the coated fabric on Teflon paper and cure it in a muffle furnace. The curing temperature of the coating is 200°C, the curing time is 60 minutes, and the thickness of the coating after curing is 100±5μm.

[0036] Finally, a ceramic electric heating film based on graphene conductive fabric was obtained.

[0037] Example 2

[0038] Step S1 is the same as that of Example 1. In step S2, the composition of the composite coating is as follows by mass percentage: 25% polysilazane resin, 35% alumina, and 40% silica sol, and the mixing method is the same as that of Example 1. In step S3, the coating method is the same as that of Example 1, and the curing temperature of the coating is 210° C. and the curing time is 60 min.

[0039] Example 3

[0040] Step S1 is the same as that of Example 1. In step S2, the composition of the composite coating is as follows by mass percentage: 30% polysilazane resin, 40% alumina, and 30% silica sol, and the mixing method is the same as that of Example 1. In step S3, the coating method is the same as that of Example 1, and the curing temperature of the coating is 220° C. and the curing time is 60 min.

[0041] Example 4

[0042] Step S1 is the same as that of Example 1. In step S2, the composition of the composite coating is as follows by mass percentage: 33% polysilazane resin, 40% alumina, and 27% silica sol, and the mixing method is the same as that of Example 1. In step S3, the coating method is the same as that of Example 1, and the curing temperature of the coating is 220° C. and the curing time is 60 min.

[0043] Comparative Example 1

[0044] Except that the composition of the composite ceramic coating is 50% polysilazane resin and 50% aluminum oxide by mass percentage, other conditions are the same as those in Example 3.

[0045] The electric heating film prepared in Examples 1 to 4 and Comparative Example 1 was subjected to an electric heating test. The electric heating film prepared in Examples 1 to 4 and Comparative Example 1 was tested. The electric heating test process used an infrared thermal imager (manufacturer: American Philier, model: A615) and an AC variable frequency power supply (manufacturer: Shenzhen Toward Technology Co., Ltd., model: TAC6003). The electrodes of the electric heating film were connected to the AC variable frequency power supply, and a constant power supply of 350V was set. The infrared thermal imager monitored the real-time temperature of the sample and recorded the current value when the sample reached a steady-state temperature. Figures 3 to 7Infrared thermal imaging photos of the electric heating films prepared in Examples 1 to 4 and Comparative Example 1 when reaching a steady-state temperature. A withstand voltage tester (manufacturer: Shenzhen Meiruike Electronic Technology Co., Ltd., model: RK2672AM) was used to conduct the withstand voltage test.

[0046] The test results are shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] After heating for about 10 seconds, the average temperatures of the electric heating films prepared in Examples 1 to 4 and Comparative Example 1 were stabilized at 479.0°C, 490.9°C, 507.1°C and 497.7°C, respectively, which were significantly higher than the temperature of Comparative Example 1. After heating and aging for 8 hours, no attenuation was found in the samples. The insulation test results showed that the resistance values ​​of the above four electric heating films all reached 10 8 In the voltage breakdown test, the film prepared in Example 3 showed excellent voltage resistance, and the coating thickness of only 100.5 μm could withstand the test of 1620V voltage for 1 minute.

[0051] From the test data of Examples 1 to 4 and Comparative Example 1, it can be seen that the electric heating film of the present invention has an obvious advantage in light weight. The weight of the electric heating film prepared in the embodiment of the present invention is 0.143 to 0.146 g / cm 2 ; In the prior art (CN117769068A), the weight of the fabric matrix (polyimide) alone is as high as 75g / cm 2 . The electric heating film of the present invention has a high steady-state temperature. When a constant voltage of 350V is applied to the electric heating film prepared in the embodiment of the present invention, the maximum steady-state temperature is 507.1°C; while the products prepared in the prior art are limited by the temperature resistance of the packaging material, and the maximum temperature shown in its embodiment is only 128°C (CN117769068A, as shown in Figure 8). The electric heating film of the present invention is easy to use, has strong universality and low cost. The present invention can heat by turning on the power, while the prior art requires laser-induced heating.

[0052] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An electric heating film, characterized in that: It includes a graphene conductive fabric layer, an electrode, a fabric transition layer, and a ceramic packaging coating; The graphene conductive fabric layer is woven from graphene fibers; The fabric transition layer is stacked on the upper and lower surfaces of the graphene conductive fabric layer, and the fabric transition layer is an insulating fiber fabric layer; The ceramic encapsulation coating is arranged on a surface of the fabric transition layer away from the graphene conductive fabric layer, and a portion of the ceramic encapsulation coating is embedded in the graphene conductive fabric layer and the fabric transition layer; The electrode is electrically connected to the graphene conductive fabric layer.

2. The electric heating film according to claim 1, characterized in that: The sheet resistance of the graphene conductive fabric layer is 10-5000Ω / sq, and the thickness of the graphene conductive fabric layer is 0.1-0.2mm; and / or The graphene fabric layer is woven in a plain or twill weave.

3. The electric heating film according to claim 1, characterized in that: The matrix of the graphene conductive fabric layer and the fabric transition layer respectively include one or more of glass fiber fabric, alumina fiber fabric, aluminum nitride fiber fabric, and mullite fiber fabric.

4. The electric heating film according to claim 3, characterized in that: The thickness of the fabric transition layer is 0.2 to 0.5 mm; and / or The weaving mode of the fabric transition layer is plain weave or twill weave.

5. The electric heating film according to claim 1, characterized in that: The ceramic packaging coating is made of 25% to 33% of polysilazane resin, 30% to 40% of Al2O3 and 27% to 45% of silica sol as raw materials in terms of mass percentage.

6. The electric heating film according to claim 5, characterized in that: The thickness of the ceramic packaging coating beyond the adjacent graphene conductive fabric layer is 80-120 μm.

7. A method for preparing an electric heating film according to any one of claims 1 to 6, characterized in that: include: S1, arranging insulating fabrics on two surfaces of the graphene conductive fabric layer as the fabric transition layer; S2, mixing the ceramic slurry and the polysilazane resin to obtain a composite ceramic coating; S3, brushing the composite ceramic coating onto the surface of the fabric transition layer and filling the composite ceramic coating into the graphene fabric layer and the fabric transition layer, and then curing to obtain the electric heating film; The ceramic slurry is prepared by mixing Al2O3 powder and silica sol.

8. The preparation method according to claim 7, characterized in that: In step S3, the brushing is performed 3 to 4 times, with an interval of 10 to 15 minutes between each application.

9. The preparation method according to claim 7, characterized in that: In the step S3, the curing temperature is 180-250° C., and the curing time is 45-75 minutes.

Images