A polytetrafluoroethylene infrared camouflage film material and its preparation method

Abstract

This invention belongs to the field of thin film materials technology, specifically relating to a polytetrafluoroethylene (PTFE) infrared camouflage thin film material and its preparation method. The invention involves stacking multiple layers of single-layer expanded PTFE films and heat-treating them to obtain a heat-insulating film. Then, multiple layers of single-layer expanded PTFE films are vacuum-impregnated in a phase change material solution and dried to obtain a phase change film. Next, silver paste, aluminum paste, or MXene paste is sprayed onto the surface of the phase change film to obtain a phase change film with a low emissivity layer. Finally, the heat-insulating film and the phase change film with the low emissivity layer are laminated together to obtain a sandwich-shaped PTFE infrared camouflage thin film material. The PTFE infrared camouflage thin film material prepared by this invention exhibits outstanding infrared stealth and long-lasting thermal camouflage effects in various complex scenarios, solving the problem that existing single-function infrared camouflage strategies cannot meet the long-lasting camouflage requirements under dynamic environmental conditions.

Description

Technical Field

[0001] This invention relates to the field of thin film materials technology, specifically to a polytetrafluoroethylene infrared camouflage thin film material and its preparation method. Background Technology

[0002] The rapid development of various infrared surveillance technologies has significantly increased the probability of target exposure. Infrared camouflage refers to the use of shielding layers, low-emissivity layers, and heat-insulating films to reduce the infrared radiation characteristics of a target, making the infrared radiation emitted by the object as consistent as possible with the ambient background radiation, thus rendering it indistinguishable from infrared detection sensors. All objects with temperatures above absolute zero produce infrared radiation, and infrared detectors primarily detect infrared radiation signals in the 3-5 and 8-14 μm ranges. According to the Stefan-Boltzmann law, the radiant energy of an object is proportional to the fourth power of its surface emissivity and surface temperature; therefore, reducing the surface emissivity of a target and controlling its surface temperature are two fundamental approaches to achieving infrared camouflage.

[0003] Constructing micro / nano structures such as photonic crystals, photonic cavities, and gratings on object surfaces can significantly reduce the emissivity of objects. However, these structures rely on precise vacuum deposition and photolithography techniques. Furthermore, these substrates are typically rigid structures, which cannot meet the diverse application requirements. Using aerogel materials with low density, high porosity, and low thermal conductivity can effectively suppress the surface temperature of objects. However, simple heat insulation does not solve the problem of heat accumulation within the object itself; the inability to dissipate heat in a timely manner affects the normal operation of the target. In addition, the temperature of the external environment is usually complex and variable, and existing single-function infrared camouflage strategies cannot meet the long-term camouflage requirements under dynamic environmental conditions. Summary of the Invention

[0004] To address the problems of high cost and insufficient rigidity in the preparation of surface optical structures using existing technologies, this invention proposes a method for preparing a polytetrafluoroethylene (PTFE) infrared camouflage film material. This method involves laminating a heat-insulating film and a phase-change film with a low-emissivity layer. The heat-insulating film blocks vertical heat transfer, the phase-change film further prevents heat penetration from the underlying layer through its latent heat of phase change, and imparts dynamic temperature regulation capabilities to the film. The low-emissivity coating reduces the target's radiated heat. The resulting film material can suppress the rise in target surface temperature for extended periods, reduce surface radiation signals, and possesses long-lasting camouflage and dynamic self-adaptive capabilities.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a polytetrafluoroethylene infrared camouflage film material, comprising the following steps:

[0006] S1. Stack multiple layers of 2-10μm expanded polytetrafluoroethylene film and heat-treat at a high temperature of 280-380℃ for 1-60min to obtain a heat insulation film with low thermal conductivity.

[0007] S2. After stacking multiple layers of 2-10μm expanded polytetrafluoroethylene film, vacuum impregnate it in a low-temperature phase change material, remove and dry it to obtain a phase change film; spray silver paste, aluminum paste or MXene paste on the upper surface of the phase change film with a thickness of 10-50μm as a low emissivity layer, and bake and cure it to obtain a phase change film with a low emissivity layer.

[0008] S3. The heat insulation film with low thermal conductivity from step S1 and the phase change film with low emissivity layer from step S2 are laminated and pressed together, wherein the heat insulation film with low thermal conductivity and the phase change film are connected to obtain a polytetrafluoroethylene infrared camouflage film material.

[0009] Further improvements to the preparation method of polytetrafluoroethylene infrared camouflage film material:

[0010] Preferably, the expanded polytetrafluoroethylene film has a porosity greater than 90% and a pore size of 0.5-5 μm.

[0011] Preferably, the low-temperature phase change material is one or a combination of two or more of paraffin wax, polyethylene glycol, stearic acid, n-dodecane, and tetradecanoic acid.

[0012] Preferably, the thickness of the heat-insulating film with low thermal conductivity in step S1 is 100-1000 μm.

[0013] Preferably, the phase change film with a low emissivity layer in step S2 has a thickness of 100-1000 μm, which is the same as the thickness of the heat insulation film with low thermal conductivity in step S1.

[0014] Preferably, the baking and curing temperature in step S2 is 60-80℃ and the time is 3-5 minutes.

[0015] Preferably, the lamination pressure in step S3 is 0.01-5 MPa, and the time is 30s-300s.

[0016] Preferably, the solid content of the silver or aluminum paste in step S2 is greater than 70%, and the volume resistivity is less than 2 × 10⁻⁶. -4 Ω·cm.

[0017] Preferably, the concentration of the MXene slurry in step S2 is 10-50 mg / ml.

[0018] Preferably, the preparation method of the MXene slurry is as follows: 0.5-3g of LiF is added to 5-50ml of hydrochloric acid solution with a concentration of 3-12mol / L, and after being mixed evenly, it is used as an etchant. 1-5g of Ti3AlC2 powder is added to the etchant, and the mixture is stirred thoroughly at room temperature to obtain a dispersion. The dispersion is centrifuged, washed with water, and dried to obtain MXene solid powder, which is then dispersed in water to obtain an MXene slurry with a concentration of 10-50mg / ml.

[0019] The advantages of this invention compared to the prior art are as follows:

[0020] 1) This invention provides a method for preparing a polytetrafluoroethylene infrared camouflage film material, which involves stacking multiple layers of single-layer expanded polytetrafluoroethylene film and heat-treating them at high temperature to obtain a heat-insulating film; vacuum impregnating the single-layer expanded polytetrafluoroethylene film in a low-temperature phase change material solution to obtain a phase change film; spraying a low-emissivity silver paste, aluminum paste, or MXene paste onto the upper surface of the phase change film to form a low-emissivity layer; and then laminating the heat-insulating film and the phase change film with the low-emissivity layer together, wherein the heat-insulating film and the low-emissivity layer are connected to obtain the polytetrafluoroethylene infrared camouflage film material.

[0021] Polytetrafluoroethylene (PTFE) possesses excellent waterproof, moisture-proof, fire-retardant, UV-resistant, chemically inert, and abrasion-resistant properties, making it ideal for outdoor hood fabrics. Expanded PTFE is obtained by unidirectional or bidirectional stretching and expansion of PTFE, exhibiting high porosity, soft texture, light weight, and superhydrophobicity. By layering multiple layers of single-layer expanded PTFE films and then treating them at high temperatures, a thermally insulating film with low thermal conductivity is produced. This film can function similarly to aerogels for insulation and also acts as a porous carrier for phase change materials, preventing leakage of the molten phase change liquid.

[0022] Low-temperature phase change materials can absorb heat by melting when heated without causing a significant increase in temperature. When the ambient temperature decreases, they slowly solidify and release heat, thereby cooling the target and overcoming the heat accumulation problem caused by simple heat insulation films. The low emissivity layer can achieve long-term camouflage and has an electric heating function, realizing the function of surface temperature changing with the environment.

[0023] The polytetrafluoroethylene infrared camouflage film material prepared by this invention has a sandwich structure, with a porous heat-insulating film at the bottom, a phase change film in the middle, and a low emissivity layer at the top. The heat-insulating film can block heat transfer in the vertical direction, and the reversible phase change process of the phase change film keeps the surface temperature of the object constant, exhibiting good infrared stealth performance. The latent heat of phase change further prevents the heat from penetrating the bottom layer and gives the film dynamic temperature regulation capability. The low emissivity coating gives the film Joule heating capability, and the surface temperature can be adjusted and controlled by controlling the voltage, which can reduce the target's radiant heat.

[0024] 2) Traditional expanded polytetrafluoroethylene (ePTFE) membranes are mainly used in air or water filtration and waterproof and breathable fabrics. This invention leverages the excellent comprehensive properties and rich microporous morphology of ePTFE to prepare a composite material with heat insulation and phase change functions using ePTFE as the substrate, expanding the application fields. The product performs well in suppressing target infrared radiation temperature and dynamic temperature control.

[0025] Traditional expanded polytetrafluoroethylene (ePTFE) membranes have abundant porosity and mature pore size control, but their thickness is only a few micrometers, making it difficult to block heat conduction, and their emissivity exceeds 0.9.

[0026] This invention stacks ultrathin expanded polytetrafluoroethylene (ePTFE) films rich in pores to form a porous carrier with macroscopic thickness. This porous thick film provides thermal insulation by relying on air and also serves as a constraining framework for the phase change material, preventing leakage during the phase change process. Finally, a low-emissivity coating is applied to the surface to suppress the infrared radiation temperature of the target from multiple heat transfer angles.

[0027] 3) The thin film material of this invention can suppress the infrared radiation energy of the target through three pathways: thermal conduction, thermal convection, and thermal radiation, significantly improving the infrared camouflage effect. The composite film showed no leakage after multiple cyclic tests and can maintain a low target surface temperature for 24 hours. When the ambient temperature rises, the surface temperature can be controlled by applying a voltage to the composite film, providing a certain degree of dynamic camouflage capability. The preparation method of this invention is low-cost, suitable for large-scale application, and highly reliable. Attached Figure Description

[0028] Figure 1 This is a microscopic morphology diagram of the expanded polytetrafluoroethylene film in Comparative Example 1 of the present invention.

[0029] Figure 2 This is a cross-sectional microstructure diagram of the heat insulation film 1 prepared in Comparative Example 1 of the present invention;

[0030] Figure 3 This is a cross-sectional microstructure of the phase change thin film prepared in Comparative Example 3 of this invention.

[0031] Figure 4 The voltage-temperature matching test is performed on the polytetrafluoroethylene infrared camouflage film material prepared in Example 1, wherein (a) is a temperature curve of the film surface when different voltages are applied to the film surface; and (b) is a temperature curve of the film surface when a 6V voltage is cyclically applied to the film surface. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] Comparative Example 1

[0034] This comparative example provides a method for preparing a heat-insulating film, which specifically includes the following steps:

[0035] Expanded polytetrafluoroethylene film with a single layer thickness of 8 μm, a porosity of 93%, and a pore size of 2 μm, and a thickness of 1000 μm after multiple layers are stacked, is heat-treated at 380℃ for 10 min to obtain a heat insulation film 1 with low thermal conductivity.

[0036] Comparative Example 2

[0037] This comparative example provides a method for preparing a heat-insulating film, which specifically includes the following steps:

[0038] Expanded polytetrafluoroethylene film with a single layer thickness of 2 μm, a porosity of 95%, and a pore size of 5 μm, and a thickness of 1000 μm after multiple layers are stacked, is heat-treated at a high temperature of 380℃ for 2 min to obtain a heat insulation film 2 with low thermal conductivity.

[0039] Comparative Example 3

[0040] This comparative example provides a method for preparing a phase change thin film, which specifically includes the following steps:

[0041] Expanded polytetrafluoroethylene film with a single layer thickness of 10 μm, a porosity of 93%, and a pore size of 2 μm, and a thickness of 500 μm after multiple layers are stacked, is vacuum impregnated in tetradecanoic acid at 60°C in a molten state for 24 h, and the unimpregnated phase change material on the surface is removed to obtain a phase change film.

[0042] Comparative Example 4

[0043] This comparative example provides a method for preparing a phase change thin film with a low emissivity layer, specifically including the following steps:

[0044] A layer of silver paste was sprayed onto the surface of the phase change film obtained in Comparative Example 3. The silver paste had a solid content of 75% and a volume resistivity of 1×10⁻⁶. -4 A phase change film with a low emissivity layer was prepared by spraying a coating with a thickness of 50 μm and an Ω·cm coating thickness, and baking and curing at 60 °C for 5 min.

[0045] Comparative Example 5

[0046] This comparative example provides a method for preparing a heat-insulating-phase change composite film, specifically including the following steps:

[0047] The heat insulation film 1 of Comparative Example 1 and the phase change film of Comparative Example 3 were laminated under a flatbed hydraulic press at a pressure of 0.1 MPa for 180 s to obtain a heat insulation-phase change composite film.

[0048] Comparative Example 6

[0049] This comparative example provides a method for preparing a heat-insulating film with a low emissivity layer, specifically including the following steps:

[0050] A layer of silver paste was sprayed onto the surface of the heat insulation film 1 in Comparative Example 1. The silver paste had a solid content of 75% and a volume resistivity of 1×10⁻⁶. -4 A heat-insulating film with a low emissivity layer was prepared by spraying a coating with an Ω·cm thickness of 50 μm as a low emissivity layer and baking and curing it at 60 °C for 5 min.

[0051] Example 1

[0052] This embodiment provides a method for preparing a polytetrafluoroethylene infrared camouflage film material, which specifically includes the following steps:

[0053] The heat-insulating film 1 of Comparative Example 1 and the phase change film with a low emissivity layer of Comparative Example 4 were laminated and pressed together under a flatbed hydraulic press, wherein the heat-insulating film and the phase change film were connected. The pressing pressure was 0.01 MPa and the pressing time was 300 s, resulting in a sandwich-structured polytetrafluoroethylene infrared camouflage film material.

[0054] Example 2

[0055] This embodiment provides a method for preparing a polytetrafluoroethylene infrared camouflage film material, which specifically includes the following steps:

[0056] The heat insulation film 1 of Comparative Example 1 and the phase change film with a low emissivity layer of Comparative Example 4 were laminated and pressed together under a flat hydraulic press, wherein the heat insulation film and the phase change film were connected. The pressing pressure was 5 MPa and the pressing time was 30 s, resulting in a sandwich-structured polytetrafluoroethylene infrared camouflage film material.

[0057] Example 3

[0058] This embodiment provides a method for preparing a polytetrafluoroethylene infrared camouflage film material, which specifically includes the following steps:

[0059] S1. Take expanded polytetrafluoroethylene film. The single layer thickness of the film is 5μm, the porosity is 93%, the pore size is 5μm, and the thickness after multiple layers are stacked is 800μm. Heat treat it at a high temperature of 280℃ for 60min to obtain a heat insulation film 3 with low thermal conductivity.

[0060] S2. The heat insulation film 3 and the phase change film with a low emissivity layer of Comparative Example 4 are laminated and pressed together under a flat hydraulic press, wherein the heat insulation film and the phase change film are connected. The pressing pressure is 0.1 MPa and the pressing time is 180 s to obtain a sandwich structure polytetrafluoroethylene infrared camouflage film material.

[0061] Example 4

[0062] This embodiment provides a method for preparing a polytetrafluoroethylene infrared camouflage film material, which specifically includes the following steps:

[0063] S1, the same as step S1 in Example 3, to obtain a heat insulation film 4 with low thermal conductivity;

[0064] S2. Add 1g of LiF to 20ml of 9mol / L hydrochloric acid solution and mix well as an etchant. Add 1g of Ti3AlC2 powder to the etchant and stir at room temperature for 24h to obtain a dispersion. Then centrifuge, wash with water and dry the dispersion to obtain MXene solid powder, and then disperse it in water to obtain 30mg / ml MXene slurry.

[0065] Take the phase change film prepared in Comparative Example 3, spray MXene slurry on its upper surface with a thickness of 20 μm as a low emissivity layer, and bake and cure to obtain a phase change film with a low emissivity layer.

[0066] S3. The heat insulation film 4 and the phase change film with a low emissivity layer obtained in step S2 are laminated and pressed together under a flat hydraulic press, wherein the heat insulation film and the phase change film are connected. The pressing pressure is 0.1 MPa and the pressing time is 180 s to obtain a sandwich structure polytetrafluoroethylene infrared camouflage film material.

[0067] Figure 1 This is a microscopic morphology diagram of the surface of the single-layer expanded polytetrafluoroethylene film used in Comparative Example 1 of this invention. Figure 2 This is a cross-sectional microstructure diagram of the heat-insulating film 1 prepared in Comparative Example 1 of the present invention. Figure 1 and Figure 2 It is known that a single-layer expanded polytetrafluoroethylene film is a microporous structure formed by a large number of interwoven fibers. After multiple layers are stacked and heat-treated, a porous heat insulation film with an aerogel-like structure is obtained. The high-temperature treatment causes the layers to fuse together without obvious delamination. Figure 3 This is a cross-sectional microstructure image of the phase change thin film prepared in Comparative Example 3 of this invention; by Figure 3 It can be seen that under the capillary action of the porous expanded polytetrafluoroethylene membrane, the phase change material is fully wetted in the vacuum oven. This capillary action effectively suppresses the leakage problem after the phase change material melts.

[0068] The films prepared in Example 1 and Comparative Examples 1 and 6 were placed on a hot stage at 120°C. For films with a heat-insulating film in their structure, the heat-insulating film was in contact with the hot stage. After heating for 10 minutes, the surface temperature of the film was detected using an infrared thermal imager. Conversely, the films prepared in Comparative Examples 1-6 and Examples 1-3 were placed on a hot stage at 60°C. For films with a heat-insulating film in their structure, the heat-insulating film was in contact with the hot stage. After heating for 24 hours, the surface temperature of the film was detected using an infrared thermal imager. The test results are shown in Table 1 below.

[0069] Table 1. Surface temperature tests of the thin film products after heating in Comparative Examples 1-6 and Examples 1-3.

[0070]

[0071]

[0072] As shown in Table 1, when the hot stage temperature is 120℃, the thermal insulation film of expanded polytetrafluoroethylene (ePTFE) in Comparative Example 1 alone can achieve a thermal insulation effect of 22℃. When a low-emissivity Ag layer is added (Comparative Example 6), the surface temperature difference of the sample reaches 60℃. In Example 1, after combining the thermal insulation film and a phase change film with a low-emissivity layer, the surface temperature of the sandwich-structured composite film is as low as 54℃, and the temperature difference with the hot stage reaches 66℃. This fully demonstrates that the composite structure of the film of this invention can effectively suppress the vertical conduction of target temperature and reduce infrared radiation energy in infrared thermal imaging. When the hot stage temperature is controlled at 60℃ and maintained for 24 hours, compared with single-layer and two-layer films, the sandwich-structured composite film of this invention still exhibits the best temperature barrier performance, proving that the composite structure has long-term camouflage capability.

[0073] The surface temperature of Comparative Example 1 is lower than that of Comparative Example 2. This is because the single-layer expanded polytetrafluoroethylene (ePTFE) used in Comparative Example 1 has a smaller pore size and a larger thickness. During the stacking and heat treatment process, the porous structure can be better preserved, resulting in a thermal insulation film with lower thermal conductivity. The ePTFE film used in Comparative Example 2 is thinner, requiring more single-layer ePTFE layers to be stacked to form a thermal insulation film of the same thickness. This results in a denser thermal insulation film with lower porosity.

[0074] The surface temperatures of Comparative Examples 3 and 5 are very close to those of the hot stage. This is because when the heating time is long enough, the phase change material will completely melt. At this point, the phase change film loses its ability to continue absorbing heat, and the heat at the bottom of the film sample gradually accumulates and is conducted to the upper surface of the sample. Because Comparative Example 5 has a heat-insulating film at the bottom, the sample surface temperature is lower.

[0075] The surface temperature of Comparative Example 4 was significantly lower than that of Comparative Example 3, and the surface temperature of Comparative Example 6 was significantly lower than that of Comparative Example 1. This demonstrates that the low emissivity Ag layer can more effectively suppress the heat radiation of objects.

[0076] The surface temperature of Example 2 is higher than that of Example 1. This is because the pressing pressure in Example 2 is too high, which leads to a decrease in the porosity of the heat insulation film. Long-term pressurization may even cause the polytetrafluoroethylene to creep and produce irreversible deformation, affecting the overall temperature control effect.

[0077] The surface temperature of Example 4 is much lower than that of Examples 1-3. This is because MXene is composed of transition metal carbonitrides with a thickness of several atomic layers, exhibiting excellent nanoscale effects and conductivity comparable to metals. MXene paste has a single component and high purity, and coatings prepared from MXene are superior to silver paste in terms of density, continuity, and purity.

[0078] Figure 4 The voltage-temperature matching test is performed on the polytetrafluoroethylene infrared camouflage film material prepared in Example 1, where (a) is a graph showing the surface temperature of the film when different voltages are applied to the film surface; and (b) is a graph showing the surface temperature of the film when a 6V voltage is cyclically applied to the film surface. Figure 4 It can be seen that when the ambient temperature changes, by applying different voltages to the low emissivity layer, the surface temperature of the sample can be controlled to remain synchronized with the environment, achieving the effect of dynamic camouflage. The temperature control effect is very stable after repeated power-on.

[0079] In summary, the sandwich structure design in the polytetrafluoroethylene infrared camouflage film material of this invention suppresses target heat penetration from three aspects: heat conduction, heat convection, and heat radiation, significantly reducing the infrared radiation characteristics of the target under infrared thermal imaging and exhibiting excellent long-term infrared camouflage performance. Furthermore, the low emissivity layer, relying on Joule heating properties, can regulate the target surface temperature according to environmental changes, providing a dynamic camouflage effect.

[0080] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a polytetrafluoroethylene infrared camouflage film material, characterized in that, Includes the following steps: S1. Stack multiple layers of 2-10μm expanded polytetrafluoroethylene film and heat-treat at a high temperature of 280-380℃ for 1-60min to obtain a heat insulation film with low thermal conductivity. S2. After stacking multiple layers of 2-10μm expanded polytetrafluoroethylene (ePTFE) films, vacuum impregnate them in a low-temperature phase change material, remove and dry them to obtain a phase change film; spray silver paste, aluminum paste or MXene paste on the upper surface of the phase change film with a thickness of 10-50μm as a low emissivity layer, and bake and cure to obtain a phase change film with a low emissivity layer; the low-temperature phase change material is one or a combination of two or more of paraffin wax, polyethylene glycol, stearic acid, n-dodecane, and tetradecanoic acid. S3. The heat insulation film with low thermal conductivity from step S1 and the phase change film with low emissivity layer from step S2 are laminated and pressed together, wherein the heat insulation film with low thermal conductivity and the phase change film are connected to obtain a polytetrafluoroethylene infrared camouflage film material.

2. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, The expanded polytetrafluoroethylene film has a porosity greater than 90% and a pore size of 0.5-5 μm.

3. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, Step S1 has a thermal insulation film with low thermal conductivity and a thickness of 100-1000 μm.

4. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1 or 3, characterized in that, The phase change film with a low emissivity layer in step S2 has a thickness of 100-1000 μm, which is the same as the thickness of the heat insulation film with low thermal conductivity in step S1.

5. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, In step S2, the baking and curing temperature is 60-80℃ and the time is 3-5 minutes.

6. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, In step S3, the lamination pressure is 0.01-5 MPa, and the time is 30s-300s.

7. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, The silver or aluminum paste mentioned in step S2 has a solid content greater than 70% and a volume resistivity less than 2 × 10⁻⁶. -4 Ω·cm.

8. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1, characterized in that, The concentration of the MXene slurry in step S2 is 10-50 mg / ml.

9. The method for preparing the polytetrafluoroethylene infrared camouflage film material according to claim 1 or 8, characterized in that, The preparation method of the MXene slurry is as follows: 0.5-3g of LiF is added to 5-50ml of hydrochloric acid solution with a concentration of 3-12mol / L. After mixing evenly, it is used as an etchant. 1-5g of Ti3AlC2 powder is added to the etchant. The mixture is stirred thoroughly at room temperature to obtain a dispersion. The dispersion is centrifuged, washed with water and dried to obtain MXene solid powder. The powder is then dispersed in water to obtain an MXene slurry with a concentration of 10-50mg / ml.

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