CN117126561A - Preparation method of micro-nano structure carbon-based light absorption coating - Google Patents

Abstract

The invention discloses a preparation method of a micro-nano structure carbon-based light absorption coating. The light absorbing coating is prepared by uniformly mixing Carbon Nanotubes (CNTs) with different pipe diameters, reduced Graphene Oxide (RGO), a diluent and an organic solvent, adding ink to prepare modified ink for spraying, and uniformly spraying the modified ink on a substrate by adopting a high-voltage electrostatic spraying technology to prepare the coating with a special micro-nano structure optical cavity. The light absorption coating obtained by the preparation method of the invention obviously improves the light absorption rate of the coating.

Description

A method for preparing a micro-nano structure carbon-based light-absorbing coating

Technical field

The invention belongs to the technical field of chemical materials and relates to a method for preparing an infrared signal absorbing coating, and in particular to a method for preparing a micro-nano structure carbon-based light absorbing coating.

Background technique

Optical devices have a wide range of applications in both civilian and military fields, such as space cameras used to detect and monitor the operating status of spacecraft, spectrophotometers that measure the absorption spectrum of materials, and CMOS image sensors for digital cameras. The performance of optical devices is affected by stray light, which can cause problems such as reduced image contrast, false signals and false phases, and even damage fragile optical components. Therefore, it is essential to reduce stray light in optics as much as possible. Using light-absorbing coatings on the surfaces of optical mechanical parts and optical elements to absorb stray light is an effective method to suppress stray light.

As people's requirements for the performance of optoelectronic devices have become more stringent, higher requirements have been placed on the light absorption performance of absorbing coatings. Research shows that creating micro-nano structures is an effective method to improve the light absorption performance of coatings. However, conventional methods such as magnetron sputtering, femtosecond laser and chemical vapor deposition involve expensive equipment, complex processes and stringent conditions.

The principle of high-voltage electrostatic spraying technology is to generate corona discharge at the cathode to charge the sprayed paint medium. The charged droplets are affected by Coulomb repulsion and surface tension, which causes the stability of the droplet surface to be destroyed, and then breaks and disperses into particles. Smaller droplets create an atomizing effect.

At present, there is no light-absorbing coating with strong absorption rate for light in the visible to near-infrared band.

Contents of the invention

The object of the present invention is to overcome the above shortcomings and provide a method for preparing a micro-nano structure carbon-based light-absorbing coating. This method uses spray slurries with appropriate process properties, combined with high-voltage electrostatic spraying technology, to prepare coatings with high absorption properties in a simple and efficient manner. The light-absorbing coating prepared by this method constructs a composite structure containing micron-sized optical cavities and nano-sized optical cavities, and has strong absorption rate for light from visible light to near-infrared bands.

The purpose of the present invention is achieved in the following ways:

A method for preparing a micro-nano structure carbon-based light-absorbing coating, which method includes the following steps:

1) Stir and mix the carbon nanotube (CNT) slurry and the reduced graphene oxide (RGO) slurry with the diluent to form a dispersed suspension;

2) Add a mixed solvent containing an organic solvent and a resin solvent to each suspension, and mix them to obtain a uniformly dispersed slurry of each raw material;

3) Mix all the raw material slurries and then add the ink and mix again. Use high-voltage electrostatic spraying technology to spray evenly on the substrate. After drying, take it out and cool it.

Preferably, the mass ratio of reduced graphene oxide (RGO) slurry to carbon nanotube (CNT) slurry in step 1) is 1:0.2~2.0, preferably reduced graphene oxide slurry and carbon nanotube slurry The mass ratio is 1:1.

Preferably, the solid mass content of reduced graphene oxide in the reduced graphene oxide slurry in step 1) is 4%, and the reduced graphene oxide is in an irregular flake shape, and its size perpendicular to the thickness direction is 100 nm to 5000 nm. ;

The carbon nanotube solid mass content in the carbon nanotube slurry is 4%. The carbon nanotube solid is in the shape of a curved tube with a diameter of 5 to 50 nm, preferably a diameter of 10 to 20 nm, and a length of 100 to 5000 nm. The carbon nanotube solid can also be Mixtures of different diameters.

Preferably, the diluent in step 1) is one or more of ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and ethyl benzoate, preferably The diluent is ethyl acetate.

Preferably, the mass ratio of the carbon nanotube slurry and the reduced graphene oxide slurry to the diluent in step 1) is 1:0.5-5.0, and the preferred mass ratio is 1:0.5-1.0.

Preferably, the mass ratio of the resin solvent to the organic solvent in the mixed solvent in step 2) is 1:1.0-5.0, and further preferably the mass ratio is 1:1; the resin solvent is a solvent-based acrylic resin, and the organic solvent Including but not limited to one or more of absolute ethanol, acetone, diethyl ether, toluene, xylene, and terpineol, with absolute ethanol being the most preferred.

Preferably, the mass ratio of each suspension to the mixed solvent in step 2) is 1:0.5-5.0.

Preferably, in step 3), the ink contains carbon nanoparticles (CNP) with a particle size of 20 nm and epoxy resin.

Preferably, the mass ratio of the total mixing amount of each raw material slurry to the ink in step 3) is 100:0.5-5.0, and more preferably the mass ratio is 100:2.0-4.0.

Preferably, the electrostatic voltage used in the high-voltage electrostatic spraying in step 3) is 9kV, the spraying height is 30mm, and the spraying amount is 35μ; the thickness of the coating formed after spraying is 5-10μm.

In the present invention, the charged paint medium is deposited on the surface of the positively charged object to be coated along the force direction under the action of electric field force and gravity, forming a uniform and firmly adherent thin film. The method of the invention has the characteristics of small droplet size, easy adjustment of process conditions, simple equipment, low cost, high adhesion between the prepared film and the substrate, uniform composition and durability.

Compared with the existing technology, the present invention has the following advantages:

(1) The addition of CNT in the method of the present invention causes the RGO to be tilted and stacked at a certain angle, so that the product forms a composite structure with optical cavities of different sizes and improves the light absorption performance;

(2) By regulating the CNT diameter, the number of micron- and nano-scale optical cavities in the coating can be effectively adjusted, thereby adjusting the light absorption rate of the coating;

(3) Using specific high-voltage electrostatic spraying technology, the modified ink has excellent atomization effect, simple preparation process, high production efficiency, and strong controllability of the preparation process.

Description of the drawings

Figure 1 is a scanning electron microscope photograph of each coating of the Example and Comparative Example, in which (a) to (d) are RGO/CNP (Comparative Example 1), RGO/CNT ₁₀ -CNP (Example 1), and RGO/CNT respectively. _{15 -} Microstructure of CNP (Example 2) and RGO/CNT ₂₀ -CNP (Example 3) coating surfaces (the subscript of CNT is its diameter size in nm).

Figure 2 shows the average light absorption rate of each coating in Examples and Comparative Examples.

Figure 3 is the absorption spectra of each coating in Examples 1 to 3 and Comparative Example 1 in the wavelength range of 400 to 1400 nm.

Figure 4 is a schematic diagram of the morphology of the coatings of Examples 1 to 3 and Comparative Example 1 and an illustration of their light reflection and scattering effects. (a) is the reflection effect of RGO/CNP (Comparative Example 1) coating on light and Schematic diagram of the scattering effect, (b) is a schematic diagram of the morphology of the RGO/CNT-CNP coating (Examples 1 to 3), (c) is a schematic diagram of the reflection and scattering effects of the RGO/CNT-CNP coating on light (Example 1 ~3).

Detailed ways

The invention is further explained below through specific examples: among them, RGO slurry is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.; CNT slurry is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.; solvent-based acrylic resin is purchased from From Weifang Ruiguang Chemical Co., Ltd.; the ink was purchased from Dongguan Dongke Electronic Technology Co., Ltd.;

Example 1

1. Weigh 6.25g RGO slurry and 6.25g CNT slurry respectively. The mass content of solids in both slurries is 4%. The CNT solid is a curved tube with a diameter of 10nm and a length of 500~5000nm (hereinafter referred to as CNT ₁₀ ) .

2. Dilute and mix the RGO slurry and CNT ₁₀ slurry with 4g of ethyl acetate respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, RGO suspension and CNT ₁₀ suspension were obtained.

3. Add 6g of solvent-based acrylic resin to 6g of absolute ethanol, stir magnetically until completely dissolved, the stirring rate is 8rad/s, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add 6g of the mixed solvent to each of the RGO suspension and CNT ₁₀ suspension, and disperse through a magnetic stirrer. The stirring rate is 8rad/s. After stirring for 30 minutes, the RGO mixed slurry and CNT ₁₀ mixed slurry are obtained. .

5. Mix the RGO mixed slurry and the CNT ₁₀ mixed slurry, add 1g of ink, stir for 30 minutes using a magnetic stirrer at a stirring rate of 8 rad/s, and then disperse by ultrasonic for 30 minutes to prepare CNT ₁₀ -RGO modified ink.

6. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

7. Absorb the CNT ₁₀ -RGO modified ink to the high-voltage electrostatic spray gun, adjust the spray height to 30mm, the spray voltage to 9kV, and the spray volume to 35 μL, and spray.

8. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

Example 2

1. Weigh 6.25g RGO slurry and 6.25g CNT slurry respectively. The mass content of solids in both slurries is 4%. The CNT solid is a curved tube with a diameter of 15nm and a length of 500~5000nm (hereinafter referred to as CNT ₁₅ ). .

2. Dilute and mix the RGO slurry and CNT ₁₅ slurry with 2g of ethyl acetate respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, RGO suspension and CNT ₁₅ suspension are obtained.

3. Add 10g of solvent-based acrylic resin to 10g of absolute ethanol, stir magnetically until completely dissolved, the stirring rate is 8rad/s, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add RGO suspension and CNT ₁₅ suspension to 10g of mixed solvent respectively, and disperse through a magnetic stirrer. The stirring rate is 8rad/s. After stirring for 30 minutes, RGO mixed slurry and CNT ₁₅ mixed slurry are obtained. .

5. Mix the RGO mixed slurry and the CNT ₁₅ mixed slurry, add 1g of ink, stir for 30 minutes using a magnetic stirrer at a stirring rate of 8 rad/s, and then disperse by ultrasonic for 30 minutes to prepare CNT ₁₅ -RGO modified ink.

6. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

7. Absorb the CNT ₁₅ -RGO modified ink to the high-voltage electrostatic spray gun, adjust the spraying height to 30mm, the spraying voltage to 9kV, and the spraying volume to 35μL, and spray.

8. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

Example 3

1. Weigh 6.25g RGO slurry and 6.25g CNT slurry respectively. The mass content of solids in both slurries is 4%. The CNT solid is in the shape of a curved tube with a diameter of 20nm and a length of 500~5000nm (hereinafter referred to as CNT ₂₀ ) .

2. Dilute and mix the RGO slurry and CNT ₂₀ slurry with 8g of ethyl acetate respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, RGO suspension and CNT ₂₀ suspension are obtained.

3. Add 4g of solvent-based acrylic resin to 4g of absolute ethanol, stir magnetically until completely dissolved, the stirring rate is 8rad/s, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add 4g of RGO suspension and CNT ₂₀ suspension into the mixed solvent respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, the RGO mixed slurry and CNT ₂₀ mixed slurry are obtained. .

5. Mix the RGO mixed slurry and the CNT ₂₀ mixed slurry, add 1g of ink, stir for 30 minutes using a magnetic stirrer at a stirring rate of 8 rad/s, and then disperse by ultrasonic for 30 minutes to prepare CNT ₂₀ -RGO modified ink.

6. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

7. Absorb the CNT ₂₀ -RGO modified ink to the high-voltage electrostatic spray gun, adjust the spraying height to 30mm, the spraying voltage to 9kV, and the spraying volume to 35μL, and spray.

8. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

Comparative example 1

1. Weigh 6.25g RGO slurry.

2. Dilute the RGO slurry with 4g of ethyl acetate and place it in a beaker. Disperse it with a magnetic stirrer. Adjust the stirring rate to 8rad/s and stir for 30 minutes to prepare an RGO suspension.

3. Add 1g of solvent-based acrylic resin to 1g of absolute ethanol, stir magnetically for 30 minutes until completely dissolved, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add the RGO suspension into the mixed solvent, then add 1g of ink, continue to stir with a magnetic stirrer for 30 minutes, and then disperse with ultrasonic for 30 minutes to prepare RGO modified ink.

5. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

6. Pour the RGO modified ink into the high-voltage electrostatic spray gun, adjust the spraying height to 30mm, the spraying voltage to 9kV, and the spraying volume to 35μL, and spray.

7. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

Comparative example 2

1. Weigh 6.25g RGO slurry and 6.25g CNT slurry respectively. The mass content of solids in both slurries is 4%. The CNT solid is a curved tube with a diameter of 80nm and a length of 500~5000nm (hereinafter referred to as CNT ₈₀ ) .

2. Dilute and mix the RGO slurry and CNT ₈₀ slurry with 4g of ethyl acetate respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, RGO suspension and CNT ₈₀ suspension were obtained.

3. Add 6g of solvent-based acrylic resin to 6g of absolute ethanol, stir magnetically until completely dissolved, the stirring rate is 8rad/s, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add RGO suspension and CNT ₁₀ suspension to 6g of mixed solvent respectively, and disperse them with a magnetic stirrer at a stirring rate of 8rad/s. After stirring for 30 minutes, RGO slurry and CNT ₈₀ slurry are obtained.

5. Mix RGO slurry and CNT ₁₀ slurry, add 1g of ink, use a magnetic stirrer to stir for 30 minutes at a stirring rate of 8 rad/s, and then disperse it ultrasonic for 30 minutes to prepare CNT ₈₀ -RGO modified ink.

6. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

7. Absorb the CNT ₈₀ -RGO modified ink into the high-voltage electrostatic spray gun, adjust the spray height to 30mm, the spray voltage to 9kV, and the spray volume to 35 μL, and spray.

8. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

Comparative example 3

1. Weigh 6.25g RGO slurry and 6.25g CNT slurry respectively. The mass content of solids in both slurries is 4%. The CNT solid is a curved tube with a diameter of 10nm and a length of 500~5000nm (hereinafter referred to as CNT ₁₀ ) .

2. Mix the RGO slurry and CNT ₁₀ slurry with 4g of ethyl acetate diluent respectively, and disperse them with a magnetic stirrer at a stirring rate of 8 rad/s. After stirring for 30 minutes, RGO suspension and CNT ₁₀ suspension are obtained. .

3. Add 6g of solvent-based acrylic resin to 6g of absolute ethanol, stir magnetically until completely dissolved, the stirring rate is 8rad/s, and let stand for 30 minutes to form a uniform mixed solvent.

4. Add RGO suspension and CNT ₁₀ suspension to 6g of mixed solvent respectively, and disperse through a magnetic stirrer at a stirring rate of 8rad/s. After stirring for 30 minutes, RGO mixed slurry and CNT ₁₀ mixed slurry are obtained. .

5. Mix the RGO mixed slurry and the CNT ₁₀ mixed slurry, add 5g of ink, stir for 30 minutes using a magnetic stirrer at a stirring rate of 8 rad/s, and then disperse by ultrasonic for 30 minutes to prepare CNT ₁₀ -RGO modified ink.

6. Wash and dry the pure aluminum sheet with a size of 20×20mm and a thickness of 1mm to be used for spraying.

7. Absorb the CNT ₁₀ -RGO modified ink to the high-voltage electrostatic spray gun, adjust the spray height to 30mm, the spray voltage to 9kV, and the spray volume to 35 μL, and spray.

8. Put the sprayed workpiece into the oven, set the drying temperature to 120°C, the drying time to 20 minutes, and cool after drying.

The comparison of the microstructure and light absorption properties of the samples prepared in each Example and Comparative Example is as follows:

1. Microstructure

As shown in Figure 1(a), in the RGO/CNP coating prepared in Comparative Example 1, RGO flakes are stacked into a flat RGO framework, and the coating surface contains several pores with sizes ranging from 800 to 1400 nm. The CNP in the ink Evenly attached to the RGO surface. It can be seen that the composite structure formed by the RGO/CNP coating is composed of nano-scale CNP attachments attached to the micron-scale RGO framework.

As shown in Figure 1(b)-(d), in the RGO/CNT ₁₀ -CNP, RGO/CNT ₁₅ -CNP and RGO/CNT ₂₀ -CNP coatings prepared in Examples 1-3, the added CNT is attached to on the RGO framework. In comparison, the coverage of RGO by CNT ₁₀ is low. Some exposed RGO can still be seen on the coating surface, and the coating structure is still relatively flat. RGO/CNT ₁₅ -CNP coating and RGO/CNT ₂₀ -CNP The RGO in the coating is almost completely covered by the CNT network. The surface of the coating presents a porous network structure. The interior of the coating contains a large number of optical cavities with sizes ranging from tens to hundreds of nanometers. The addition of CNT allows RGO to be tilted and stacked at a certain angle to form a CNT-CNP/RGO/CNT-CNP sandwich structure. This porous framework constructed from the sandwich structure also contains some micron-sized optical cavities, thereby creating a perfect structure in RGO/CNT-CNP. A composite structure containing micron-sized optical cavities and nano-sized optical cavities is formed in the coating. As the CNT diameter increases, the number of micron- and nanometer-sized optical cavities increases significantly.

2. Light absorption performance

As can be seen from Figure 2, the light absorption rates of the RGO/CNT ₁₀ -CNP, RGO/CNT ₁₅ -CNP and RGO/CNT ₂₀ -CNP coatings prepared after adding CNT in Examples 1 to 3 were increased to 93.5% and 93.8% respectively. and 94.1%. The average absorption rate of the RGO/CNP coating without CNT modification for light in the wavelength range of 400 to 1400 nm is only 90.5% (Comparative Example 1). Further comparison in Figure 3 shows that the RGO/CNP coating has The absorption of short-wavelength light around 400nm is weak, while the RGO/CNT-CNP coating shows strong absorption of light in the wavelength range of 400 to 1400nm. It can be seen that the light absorption performance of the RGO/CNT-CNP coating is greatly improved, and the light absorption rate of the coating increases as the CNT diameter increases. However, excessive CNT diameter will also cause a decrease in light absorption (Comparative Example 2). In addition, increasing the amount of ink is equivalent to reducing the content of RGO and CNT, which will also cause the light absorption rate to be lower (Comparative Example 3).

Combined with the microstructure observation results in Figure 1, the light absorption mechanism of each coating is analyzed, as shown in Figure 4. The RGO/CNP coating prepared in Comparative Example 1 was prepared with RGO as the framework and CNP as the attachment. Due to the small size of the CNP, the RGO flakes were mostly stacked in a tiled form. The surface of the RGO/CNP coating was relatively flat and lacked optical cavities. When light irradiates the surface of the RGO/CNP coating, the reflected light and scattered light are not easily absorbed, resulting in radiation loss [Figure 4(a)], so the light absorption rate of the RGO/CNP coating is relatively low. For the coating prepared in Examples 1 to 3, the CNT network is attached to the surface of RGO, which reduces the exposed area of RGO, which is beneficial to improving the anti-reflective performance of the coating; and the CNT causes the RGO to be stacked at a certain angle to form a micron-level Large-size optical cavities, while the CNT network structure also contains a large number of small-size optical cavities with sizes in the range of tens to hundreds of nanometers [Figure 4(b)], the light entering the RGO/CNT-CNP coating After large and small size optical cavities, multiple reflections occur in the cavity, which enhances the number of light absorption [Figure 4(c)]; in addition, CNT is also an excellent light scattering material, and scattered light can also be absorbed by small size optical cavities. Absorption, further improving the light absorption rate.

Claims (10)

1. A method for preparing a micro-nano structure carbon-based light-absorbing coating, characterized in that the method includes the following steps: 1) Stir and mix the carbon nanotube slurry and the reduced graphene oxide slurry with the diluent respectively to form a dispersed suspension; 2) Add a mixed solvent containing an organic solvent and a resin solvent to each suspension, and mix them to obtain a uniformly dispersed slurry of each raw material; 3) Mix all the raw material slurries and then add the ink and mix again. Use high-voltage electrostatic spraying technology to spray evenly on the substrate. After drying, take it out and cool it. 2. The preparation method of micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the mass ratio of reduced graphene oxide slurry and carbon nanotube slurry in step 1) is 1:0.2 ~2.0, preferably the mass ratio of reduced graphene oxide slurry to carbon nanotube slurry is 1:1. 3. The preparation method of micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the carbon nanotube solid mass content in the carbon nanotube slurry in step 1) is 4%, and the reduction and oxidation rate is 4%. The reduced graphene oxide solid mass content in the graphene slurry is 4%; the carbon nanotube solid is in the shape of a curved tube with a diameter of 5 to 50 nm. 4. The preparation method of micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the diluent in step 1) is ethyl formate, propyl formate, methyl acetate, ethyl acetate , one or more of propyl acetate, butyl acetate, and ethyl benzoate, and the preferred diluent is ethyl acetate. 5. The preparation method of the micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the mass ratio of the carbon nanotube slurry and the reduced graphene oxide slurry to the diluent in step 1) The mass ratio is 1:0.5-5.0, and the preferred mass ratio is 1:0.5-1.0. 6. The preparation method of the micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the mass ratio of the resin solvent and the organic solvent in the mixed solvent in step 2) is 1:1.0~5.0, so The resin solvent is a solvent-based acrylic resin, and the organic solvent includes but is not limited to one or more of absolute ethanol, acetone, ether, toluene, xylene, and terpineol. 7. The method for preparing a micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the mass ratio of each suspension to the mixed solvent in step 2) is 1:0.5~5.0. 8. The method for preparing a micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the ink described in step 3) contains carbon nanoparticles with a particle size of 20 nm and epoxy resin. 9. The method for preparing a micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the mass ratio of the total mixing amount of raw material slurry to the ink in step 3) is 100:0.5-5.0. 10. The method for preparing a micro-nano structure carbon-based light-absorbing coating according to claim 1, characterized in that the thickness of the coating formed after spraying in step 3) is 5-10 μm.