A colored carbon-based electro-variable infrared emissivity film and a preparation method thereof

Abstract

The present invention discloses a colored carbon-based electrovariable infrared emissivity film, comprising a carbon-based material film and a covering coating and a colored coating sequentially covering the carbon-based material film. The present invention also discloses a method for preparing the above-mentioned colored carbon-based electrovariable infrared emissivity film. The present invention applies different colors on the black carbon-based material film by spraying or scraping, so that the electrovariable emissivity performance of the carbon-based material film is not affected while having rich colors. Different colors can be suitable for different usage scenarios, thereby meeting the need for visual invisibility under visible light; the present invention can directly obtain the corresponding color of the carbon-based material film by adjusting the color of the color paste; the carbon-based electrovariable infrared emissivity film prepared by the present invention still has the performance of electrovariable infrared emissivity, and also has good cycle stability, meeting the requirements for infrared invisibility.

Description

Technical Field

[0001] The invention relates to a colored carbon-based electrotropic infrared emissivity film and also relates to a method for preparing the colored carbon-based electrotropic infrared emissivity film. Background Art

[0002] Electrotropic infrared emissivity materials have always attracted the attention of scientists at home and abroad as stealth materials. Through the stimulation of external voltage, the optical properties of the material change, thereby adjusting the infrared emissivity of the material so that it can be used in the field of infrared stealth.

[0003] As a new material, carbon-based materials have been widely studied in the field of electro-variable infrared emissivity. For example, Coskun Kocabas designed an electro-variable infrared emissivity material based on multilayer graphene, which can achieve an infrared emissivity modulation range of 0.76-0.33 under an applied voltage of 0-4V (Graphene-Based Adaptive Thermal Camouflage [J]. Nano Letters, 2018 18 (7), 4541-4548). Domestic scholars Lin Xiao and others studied multi-walled carbon nanotube thin films as electro-variable infrared emissivity devices, and the infrared emissivity of the device changed with the voltage between -3V and 3V (Large-Scale Multifunctional Carbon Nanotube Thin Film as Effective Mid-Infrared Radiation Modulator with Long-Term Stability [J]. Adv. Optical Mater. 2021, 9, 2001216.). Many carbon-based electrovariable infrared emissivity materials have been reported. However, due to the black color of carbon-based materials themselves, they cannot be visually invisible in the visible light band, making it difficult to meet the visible light-infrared compatible stealth requirements. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a colored carbon-based electrotropic infrared emissivity film, which can adjust the color of the film based on the color of the environment, thereby simultaneously meeting the requirements of visible light (visual invisibility) and infrared invisibility; another purpose of the present invention is to provide a method for preparing the above-mentioned colored carbon-based electrotropic infrared emissivity film.

[0005] Technical solution: The colored carbon-based electrovariable infrared emissivity film of the present invention comprises a carbon-based material film and a covering coating and a colored coating sequentially covering the carbon-based material film.

[0006] Wherein, the covering coating is a white coating.

[0007] Wherein, the total thickness of the covering coating and the color coating on the carbon-based material film is 10-20 μm.

[0008] It also includes a diaphragm and a conductive layer; the carbon-based electrovariable infrared emissivity film is composed of a carbon-based material film covered with a covering coating and a color coating in sequence, a diaphragm and a conductive layer.

[0009] Among them, the carbon-based material film is a carbon nanotube film or a graphene film; the conductive layer is one of a carbon nanotube film, a graphene film, a gold film, a silver film or an ITO film; the diaphragm is a Celgard diaphragm or a PE diaphragm, which is immersed in an ionic liquid to obtain a porous organic diaphragm loaded with ionic liquid.

[0010] The method for preparing the above-mentioned colored carbon-based electrovariable infrared emissivity film comprises the following steps:

[0011] (1) Preparing a covering coating: dissolving polyurethane in butyl acetate at room temperature, adding white nano powder, stirring ultrasonically, adding a curing agent after mixing, obtaining a white slurry, spraying the white slurry onto the carbon-based material film, and drying to obtain a white coating;

[0012] (2) Preparing a color coating: dissolving polyurethane in butyl acetate at room temperature, adding a color paste, stirring ultrasonically, adding a curing agent after mixing, obtaining a color slurry, spraying the color slurry onto the white coating, and drying to obtain a color coating;

[0013] (3) The porous membrane is immersed in the ionic liquid, and after the immersion, the porous membrane loaded with the ionic liquid is placed on the conductive layer, and then the carbon-based material film covered with the covering coating and the color coating is placed on the side of the porous membrane away from the conductive layer, and finally the composite material is bonded and sealed with a sealant to obtain a colored flexible carbon nanotube electro-variable emissivity device. Before the device is encapsulated with the sealant, two sections of conductive copper foil tape are respectively bonded to the carbon-based material film and the bottom electrode, and the conductive copper foil tape is used as a wire when the device is connected to an external power supply, the carbon-based material film is connected to the positive electrode of the power supply, and the bottom electrode is connected to the negative electrode of the power supply.

[0014] Wherein, in step (1), in the white slurry, the mass ratio of polyurethane, white nano powder and curing agent is 1-3:0.1-1.5:1-3.

[0015] Wherein, the white nano powder is TiO2 or ZnO with high refractive index.

[0016] Wherein, in step (1) and step (2), the thickness of the white coating is not higher than 10 μm; the thickness of the color coating is not higher than 10 μm. When the color coating and the covering coating are of the above thicknesses, it can ensure that the black carbon-based material film has visual color changes, thereby obtaining different colors, and it can not only not affect the electro-variable emissivity performance of the carbon-based material film, but also ensure the adhesion between the color paste and the carbon-based material film. If there is no covering coating, the color coating needs to be made thicker than 1 mm to ensure that the black carbon-based material film has visual color changes, but this will greatly affect the electro-variable emissivity performance of the carbon-based material film.

[0017] Wherein, in step (2), in the color paste, the mass ratio of polyurethane, color paste and curing agent is 1 to 3: 0.1 to 1.5: 1 to 3. The color paste includes yellow paste, green paste and blue paste.

[0018] Wherein, in step (1) and step (2), the drying temperature is 40 to 60° C. and the drying time is 8 to 12 hours.

[0019] Wherein, in step (1) and step (2), the curing agent used is polyurethane or silicone.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention applies different colors on the black carbon-based material film by spraying or scraping, so that the carbon-based material film has rich colors without affecting the electrovariable emissivity performance. Different colors can be suitable for different usage scenarios, thereby meeting the visual invisibility requirements under visible light; the present invention can directly obtain the corresponding color of the carbon-based material film by adjusting the color of the color paste; (2) The carbon-based electrovariable infrared emissivity film prepared by the present invention still has the performance of electrovariable infrared emissivity, and also has good cycle stability, meeting the requirements for infrared invisibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the method for preparing a colored carbon-based electro-variable emissivity film of the present invention;

[0022] Figure 2 It is a schematic diagram of the structure of the colored carbon-based electro-variable emissivity film of the present invention;

[0023] Figure 3 This is an optical photograph of a colored carbon nanotube film prepared by the method of the present invention;

[0024] Figure 4 The optical spectrum of the colored carbon nanotube film prepared by the method of the present invention;

[0025] Figure 5The following are histograms showing the emissivity modulation of the colored carbon-based electrovariable emissivity films prepared in Examples 1 to 3 when different voltages are applied. DETAILED DESCRIPTION

[0026] Example 1

[0027] like Figure 1 As shown, the method for preparing the colored carbon-based electrovariable infrared emissivity film of the present invention comprises the following steps:

[0028] (1) Preparation of covering coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then nano titanium dioxide powder was added thereto, and then a certain amount of butyl acetate was added thereto, and ultrasonic stirring was performed to make the mixture uniform, and finally a curing agent was added thereto, and a white color paste was obtained after mixing, and the obtained white color paste was sprayed on the carbon nanotube film, and the obtained film was dried in an oven at 50°C overnight to obtain a carbon nanotube film covered with a white coating; the mass ratio of PU resin, nano titanium dioxide powder and curing agent was 2:1:1 (2 g, 1 g and 1 g were added respectively); the thickness of the covering coating was 8 μm; the curing agent used was polyurethane; and the total amount of butyl acetate added was 10 mL;

[0029] (2) Preparation of color coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then yellow color paste was added thereto, and then a certain amount of butyl acetate was added, ultrasonic stirring was performed, and finally a curing agent was added; after mixing, a yellow color paste was obtained, and the obtained yellow color paste was sprayed on the carbon nanotube film to obtain a yellow carbon nanotube film, and finally placed in a 50°C oven for drying; the mass ratio of PU resin, yellow color paste and curing agent was 2:1:1 (2g, 1g and 1g were added respectively); the thickness of the color coating was 8 μm; the curing agent used was polyurethane; the total amount of butyl acetate added was 10 mL;

[0030] (3) First, the Celgard membrane (porous organic membrane) is immersed in an ionic liquid for 1 hour. The ionic liquid used is an imidazole-based ionic liquid. After the impregnation, the porous organic membrane loaded with the ionic liquid is placed on the bottom electrode. Then, the yellow carbon nanotube film is placed on the side of the porous organic membrane away from the bottom electrode. Finally, the composite material is bonded and sealed with epoxy resin glue to obtain a yellow flexible carbon nanotube electrovariable emissivity device.

[0031] At room temperature, the yellow carbon nanotube film is used as the top electrode, the bottom electrode (conductive layer) is flexible ITO, and a porous organic membrane is used to separate the bottom electrode and the top electrode.

[0032] Example 2

[0033] The method for preparing the colored carbon-based electrovariable infrared emissivity film of the present invention comprises the following steps:

[0034] (1) Preparation of covering coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then nano titanium dioxide powder was added thereto, and then a certain amount of butyl acetate was added thereto, and ultrasonic stirring was performed to make the mixture uniform, and finally a curing agent was added thereto, and a white color paste was obtained after mixing, and the obtained white color paste was sprayed on the carbon nanotube film, and the obtained film was dried in an oven at 50°C overnight to obtain a carbon nanotube film covered with a white coating; the mass ratio of PU resin, nano titanium dioxide powder and curing agent was 2:1:1 (2 g, 1 g and 1 g were added respectively); the thickness of the covering coating was 8 μm; the curing agent used was polyurethane; and the total amount of butyl acetate added was 10 mL;

[0035] (2) Preparation of color coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then green color paste was added thereto, and then a certain amount of butyl acetate was added, ultrasonic stirring was performed, and finally a curing agent was added; after mixing, a green color paste was obtained, and the obtained green color paste was sprayed on the carbon nanotube film to obtain a green carbon nanotube film, and finally the film was placed in a 50°C oven for drying; the mass ratio of PU resin, green color paste and curing agent was 2:1:1 (2g, 1g and 1g were added respectively); the thickness of the color coating was 7 μm; the curing agent used was polyurethane; the total amount of butyl acetate added was 10 mL;

[0036] (3) First, the Celgard membrane (porous organic membrane) is immersed in an ionic liquid for 1 hour. The ionic liquid used is an imidazole-based ionic liquid. After the impregnation, the porous organic membrane loaded with the ionic liquid is placed on the bottom electrode. Then, the green carbon nanotube film is placed on the side of the porous organic membrane away from the bottom electrode. Finally, the composite material is bonded and sealed with epoxy resin glue to obtain a green flexible carbon nanotube electrovariable emissivity device.

[0037] At room temperature, the green carbon nanotube film is used as the top electrode, the bottom electrode (conductive layer) is flexible ITO, and a porous organic membrane is used to separate the bottom electrode and the top electrode.

[0038] Example 3

[0039] The method for preparing the colored carbon-based electrovariable infrared emissivity film of the present invention comprises the following steps:

[0040] (1) Preparation of covering coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then nano titanium dioxide powder was added thereto, and then a certain amount of butyl acetate was added thereto, and ultrasonic stirring was performed to make the mixture uniform, and finally a curing agent was added thereto, and a white color paste was obtained after mixing, and the obtained white color paste was sprayed on the carbon nanotube film, and the obtained film was dried in an oven at 50°C overnight to obtain a carbon nanotube film covered with a white coating; the mass ratio of PU resin, nano titanium dioxide powder and curing agent was 2:1:1 (2 g, 1 g and 1 g were added respectively); the thickness of the covering coating was 8 μm; the curing agent used was polyurethane; and the total amount of butyl acetate added was 10 mL;

[0041] (2) Preparation of color coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then blue color paste was added thereto, and then a certain amount of butyl acetate was added, ultrasonic stirring was performed, and finally a curing agent was added; after mixing, a blue color paste was obtained, and the obtained blue color paste was sprayed on the carbon nanotube film to obtain a blue carbon nanotube film, and finally the film was dried in a 50°C oven; the mass ratio of PU resin, blue color paste and curing agent was 2:1:1 (2g, 1g and 1g were added respectively); the thickness of the blue coating was 6 μm; the curing agent used was polyurethane; the total amount of butyl acetate added was 10 mL;

[0042] (3) First, the Celgard membrane (porous organic membrane) is immersed in an ionic liquid for 1 hour. The ionic liquid used is an imidazole-based ionic liquid. After the impregnation, the porous organic membrane loaded with the ionic liquid is placed on the bottom electrode. Then, the blue carbon nanotube film is placed on the side of the porous organic membrane away from the bottom electrode. Finally, the composite material is bonded and sealed with epoxy resin glue to obtain a blue flexible carbon nanotube electrovariable emissivity device.

[0043] At room temperature, the blue carbon nanotube film is used as the top electrode, the bottom electrode (conductive layer) is flexible ITO, and a porous organic membrane is used to separate the bottom electrode and the top electrode.

[0044] Comparative Example 1

[0045] The Celgard membrane (porous organic membrane) is immersed in ionic liquid for 1 hour. The ionic liquid used is an imidazole ionic liquid. After impregnation, the porous organic membrane loaded with ionic liquid is placed on the bottom electrode, and then the carbon nanotube film is placed on the side of the porous organic membrane away from the bottom electrode. Finally, the composite material is bonded and sealed with epoxy resin glue to obtain a flexible carbon nanotube electrovariable emissivity device.

[0046] In the colorful flexible carbon nanotube electro-emittance device prepared by the present invention, the carbon-based material film can be a carbon nanotube film; the diaphragm can be a porous polyvinyl chloride film or a Celgard diaphragm; and the bottom electrode is a flexible ITO film. The colorful flexible carbon nanotube electro-emittance device prepared by the present invention has good flexibility and can be bent arbitrarily due to the thin coating thickness, so it can be covered on any irregular outer surface.

[0047] Figure 3 This is a picture of a colored carbon nanotube film made by the method of the present invention. Films of different colors can be used against the backgrounds of desert, soil (yellow), forest (green), ocean, and blue sky (blue), and can achieve visual invisibility of the target under visible light.

[0048] Figure 4 This is the optical spectrum of the colored carbon nanotube film prepared by the method of the present invention. The carbon nanotube films with different colors have different reflection peaks in the visible spectrum, indicating that the colored paste is successfully covered on the black carbon nanotube film, and the black carbon nanotube film itself shows full absorption in the visible light, with extremely low reflectivity and no reflection peak.

[0049] Figure 5 The emissivity change diagram of the colored carbon-based electro-variable infrared emissivity film prepared in Examples 1 to 3. Figure 5 It can be seen that the yellow, green and blue carbon-based electrotropic infrared emissivity films obtained by the method of the present invention all have the performance of electrotropic infrared emissivity, among which, after applying a positive voltage (within the range of 0-4V), the infrared emissivity of the yellow carbon-based electrotropic infrared emissivity film can be adjusted in the range of 0.35 to 0.75; the carbon nanotube film without a covering coating and a color coating obtained in Comparative Example 1 has an adjustable infrared emissivity in the range of 0.3-0.76 after applying a positive voltage (within the range of 0-4V), which shows that the method of the present invention can ensure that the black carbon-based material film has a visual color change, thereby obtaining different colors, and can not affect the electrotropic emissivity performance of the carbon nanotube film.

Claims

1. A colored carbon-based electro-variable infrared emissivity film, characterized in that: The method is as follows, which specifically comprises the following steps: (1) Preparation of covering coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then nano titanium dioxide powder was added thereto, and then butyl acetate was added thereto, and ultrasonic stirring was performed to make the mixture uniform, and finally a curing agent was added thereto, and a white color paste was obtained after mixing, and the obtained white color paste was sprayed on the carbon nanotube film, and the obtained film was dried in an oven at 50°C overnight to obtain a carbon nanotube film covered with a white coating; the mass ratio of PU resin, nano titanium dioxide powder and curing agent was 2:1:1; the thickness of the covering coating was 8 μm; the curing agent used was polyurethane; and the total amount of butyl acetate added was 10 mL; (2) Preparation of color coating: at room temperature, PU resin was dissolved with a small amount of butyl acetate, and then yellow color paste was added thereto, and then butyl acetate was added, ultrasonic stirring was performed, and finally a curing agent was added; after mixing, a yellow color paste was obtained, and the obtained yellow color paste was sprayed on the carbon nanotube film to obtain a yellow carbon nanotube film, and finally the film was placed in a 50°C oven for drying; the mass ratio of PU resin, yellow color paste and curing agent was 2:1:1; the thickness of the color coating was 8 μm; the curing agent used was polyurethane; the total amount of butyl acetate added was 10 mL; (3) First, the Celgard membrane is immersed in an ionic liquid for 1 hour. The ionic liquid used is an imidazole ionic liquid. After the immersion, the porous organic membrane loaded with the ionic liquid is placed on the bottom electrode, and then the yellow carbon nanotube film is placed on the side of the porous organic membrane away from the bottom electrode. Finally, the composite material is bonded and sealed with epoxy resin glue to obtain a yellow flexible carbon nanotube electrovariable emittance device; At room temperature, a yellow carbon nanotube film is used as the top electrode, and the bottom electrode is a flexible ITO, and a porous organic membrane is used to separate the bottom electrode and the top electrode.

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