Ultra-black coating with wide-angle absorption and preparation method and application thereof

Abstract

The invention discloses an ultra-black coating with wide-angle absorption as well as a preparation method and application of the ultra-black coating, and belongs to the technical field of ultra-black coatings and preparation of the ultra-black coatings. The problem that an existing ultra-black coating cannot present extremely low scattering and high absorptivity under large-angle incident light is solved. According to the method, carbon black is used as an absorbent, a high-temperature-resistant silica sol solution is used as a binder, a stable structure is formed by adopting a one-step sintering method, and meanwhile, an ultra-black coating with a forest-shaped light trap array structure is constructed. The refractive index of the surface of the coating is obviously changed by utilizing the forest-shaped array structure on the surface of the ultra-black coating, so that the optical reflection of the surface is reduced; the surface forest-like light trap structures are closely arranged, so that light incident from each angle can be reflected back and forth in the structure, the incident light is absorbed to the greatest extent, stable high light absorption at a wide angle is realized, the reflectivity of the ultra-black coating does not change obviously along with the angle of the incident light, and the deep space detection precision of a space optical system is improved.

Description

Technical Field

[0001] The invention relates to an ultra-black coating with wide-angle absorption, a preparation method and application thereof, and belongs to the technical field of ultra-black coatings and preparation thereof. Background Art

[0002] The stray light received by the space optical system during its on-orbit operation is an important factor affecting its detection accuracy. The ultra-black coating can effectively absorb the stray light on the key surfaces of the space optical payload and reduce imaging reflection, thereby significantly improving the detection accuracy of the space optical system. The stray light suppression performance of the ultra-black coating is determined by the intrinsic light absorption characteristics of the pigment and the resin. At present, carbon-based materials, metal-based materials, ceramic-based materials, etc. are generally selected as coating pigments, and highly stable organic epoxy resins, inorganic potassium silicate resins, etc. are used as coating binders to form a stable structure. Carbon-based materials have relatively ideal wide-spectrum intrinsic extinction properties. However, they are limited by the interface scattering effect after the coating is formed. They usually show low absorption rates in the ultraviolet-visible-near infrared bands, and show more obvious scattering under the action of large-angle incident light, which is not conducive to achieving high-performance stray light suppression of ultra-black coatings.

[0003] Ultra-black coatings can maintain extremely low scattering and reflectivity at different incident angles. This feature is particularly important for applications in the field of stray light suppression. Therefore, in response to the design of the light absorption structure of the ultra-black coating, a light-trapping structure that matches the wavelength of the incident light is constructed, which can effectively reduce the effective refractive index of the coating, reduce Fresnel reflection, and improve the wide-angle light absorption performance of the coating, so that the ultra-black coating can still maintain an extremely high absorption rate under large-angle incident light. The forest-like light trap array of the coating can give the ultra-black coating an ultra-high light absorption rate, but its molding conditions are harsh and currently rely on expensive processing equipment, often requiring vacuum, physical or chemical etching, prefabricated templates, etc. Moreover, the ultra-black coating obtained cannot exhibit extremely low scattering and high absorption rate under large-angle incident light, and cannot meet the requirements of stray light suppression at different incident angles. Summary of the invention

[0004] In order to solve the above problems existing in the existing ultra-black coating, the present invention provides an ultra-black coating with wide-angle absorption, a preparation method and application thereof.

[0005] The technical solution of the present invention:

[0006] One of the objects of the present invention is to provide a method for preparing an ultra-black coating with wide-angle absorption, the method comprising the following steps:

[0007] (1) mixing carbon black, silica sol solution and ultrapure water uniformly to obtain a first slurry;

[0008] (2) adding urea to the first slurry and mixing them evenly to obtain a second slurry;

[0009] (3) pre-treating the surface of the aluminum sheet, spraying the first slurry and the second slurry on the pre-treated aluminum sheet in sequence, and drying after each spraying until the coating thickness is 100 to 150 μm, thereby obtaining a sample to be sintered;

[0010] (4) The sample to be sintered is placed in a muffle furnace for sintering treatment to obtain an ultra-black coating with wide-angle absorption.

[0011] It is further defined that the mass concentration of the silica sol solution in (1) is 30-40%, and the mass ratio of carbon black, silica sol solution and ultrapure water is 1.2:20:30.

[0012] It is further defined that the mass ratio of the first slurry to urea in (2) is 50:0.3.

[0013] It is further defined that the surface pretreatment process of the aluminum sheet in (3) is as follows: after sandblasting to remove the surface oxide layer, acetone is used to remove the surface oil stains, and then the surface is immersed in ethanol and deionized water for ultrasonic treatment in turn, and finally dried for use.

[0014] It is further defined that the spraying pressure in (3) is 20-40 psi, and the distance between the nozzle and the aluminum sheet is 5-10 cm.

[0015] It is further defined that the drying process in (3) is: natural drying at room temperature for 30 minutes, and then drying at 100°C for 1 to 2 hours.

[0016] It is further defined that the sintering process in (4) is: raising the temperature from room temperature to 400°C within 1 hour, then keeping the temperature for 1 hour, and cooling to room temperature to obtain an ultra-black coating.

[0017] The second object of the present invention is to provide an ultra-black coating with wide-angle absorption prepared by the above method.

[0018] It is further defined that at an incident angle of 0° to 70°, the absorbance in the wavelength range of 200 to 2500 nm is above 98%.

[0019] The third purpose of the present invention is to provide an application of the above-mentioned ultra-black coating, specifically as an ultra-black coating for deep space exploration.

[0020] Beneficial effects:

[0021] The present invention uses carbon black as an absorbent to absorb incident light, and uses a high-temperature resistant silica sol solution as a binder to bond the carbon black. A one-step sintering method is used to form a stable structure while constructing an ultra-black coating with a forest-like light trap array structure. The forest-like array structure on the surface of the ultra-black coating significantly changes the refractive index and roughness of the coating, thereby changing its optical reflectivity, providing a mechanism for minimizing reflection, and the light traps are closely arranged like a forest, so that the incident light is reflected back and forth inside its structure, thereby absorbing all photons to the maximum extent, achieving a stable high absorbance at a wide angle, so that the reflectivity of the ultra-black coating does not change significantly with the angle of the incident light, and improves the deep space detection accuracy of the space optical system. Compared with the prior art, the present invention also has the following advantages:

[0022] (1) The present invention provides a simple and easy one-step sintering method for constructing a forest-like light trap array structure, which improves the existing technology's reliance on laser etching, ion sputtering equipment, and hard templates such as AAO.

[0023] (2) The forest-like light trap structures on the surface of the ultra-black coating prepared by the present invention are closely arranged, which can make the light incident at various angles reflect back and forth inside the structure, thereby absorbing the incident light to the greatest extent, achieving stable high light absorption at a wide angle, and making the reflectivity of the ultra-black coating not change significantly with the angle of the incident light, thereby improving the deep space detection accuracy of the space optical system.

[0024] (3) The forest-like structure on the surface of the ultra-black coating prepared by the present invention is in micron size, which helps to enhance the multi-scale scattering of the structure under large light incidence angles, thereby effectively improving the light absorption of the ultra-black coating under oblique incidence, achieving a stable high absorption rate within a wide angle range, and improving the existing ultra-black coating's dependence on the incident light angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a SEM photo of the surface of the ultra-black coating prepared in Example 1;

[0026] Figure 2 This is a SEM photo of the interior of the ultra-black coating prepared in Example 1;

[0027] Figure 3 The average absorbance of the ultra-black coating prepared in Example 1 in the 200-2500nm band at different incident angles;

[0028] Figure 4 This is an absorbance mapping diagram of the ultra-black coating prepared in Example 1 at different incident angles;

[0029] Figure 5 This is a SEM photo of the surface of the ultra-black coating prepared in Comparative Example 1;

[0030] Figure 6This is a SEM photo of the interior of the ultra-black coating prepared in Comparative Example 1;

[0031] Figure 7 The average absorbance of the ultra-black coating prepared in Comparative Example 1 in the 200-2500nm band at different incident angles;

[0032] Figure 8 This is the absorbance mapping diagram of the ultra-black coating prepared in Comparative Example 1 at different incident angles. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0037] Example 1

[0038] (1) 1.2 g of carbon black, 20 g of silica sol solution with a mass concentration of 40%, and 30 g of ultrapure water were placed in a stirring barrel. After ultrasonication for 30 min at room temperature, ultrasonic cutting stirring was performed at a speed of 1000 r / min for 1 h to obtain a uniformly mixed ultra-black slurry 1. 50 g of ultra-black slurry 1 was taken, 0.3 g of urea was added thereto, and magnetic stirring was performed for 30 min to mix uniformly to prepare ultra-black slurry 2.

[0039] (2) The aluminum sheet was pre-treated by sandblasting to remove the surface oxide layer, and the surface oil was removed by acetone. The aluminum sheet was immersed in ethanol and deionized water for ultrasonic treatment for 30 minutes, and then dried for later use.

[0040] (3) Use a spray gun to evenly spray the two prepared slurries on the treated aluminum sheet in sequence, control the spraying pressure to 40psi, and keep the distance between the nozzle and the aluminum sheet at 8cm. First spray the ultra-black slurry 1 with a spraying thickness of 70μm. After spraying, dry it at room temperature for 30min, and then place it in a 100℃ forced air drying oven for 2h. Then spray the ultra-black slurry 2 with a spraying thickness of 30μm. After spraying, dry it at room temperature for 30min, and then place it in a 100℃ forced air drying oven for 2h to obtain a sample to be sintered with a coating thickness of 100μm.

[0041] (5) The sample to be sintered is placed in a muffle furnace, and the temperature is raised to 400°C at a heating rate of 1 h, and then maintained at a constant temperature of 400°C for 1 h. After the urea in the coating is gasified and removed, an ultra-black coating sample is obtained.

[0042] The surface microstructure of the obtained ultra-black coating was characterized, and the SEM photos are shown in Figure 1 As shown by Figure 1 It can be seen that the coating surface presents a micron-sized forest-like protrusion and hole light trap structure. The internal microstructure of the ultra-black coating was further characterized, and the SEM photos are shown in Figure 2 As shown by Figure 2 It can be seen that there are a large number of pore structures inside. In summary, the ultra-black coating has a microscopic forest-like morphology, which makes incident light at different angles reflect back and forth inside its structure, thereby increasing the optical path of the incident light in the coating, greatly improving the coating's absorption of incident light, thereby reducing its optical reflectivity and providing a mechanism for minimizing reflection.

[0043] The absorbance of the obtained ultra-black coating in the 200-2500nm band at different incident angles was tested. The test results are as follows: Figure 3 and Figure 4 As shown in the figure, it can be seen that the ultra-black coating can maintain a high absorption rate of more than about 98% in the band of 200-2500nm at an incident angle of 0° to 60°. At 70°, the absorbance can still reach 98%, achieving a relatively stable high absorption rate within a wide-angle range.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that 0 g of urea is added, and the remaining process steps and parameter settings are the same as those in Example 1.

[0046] The ultra-black coating prepared in this comparative example has an absorbance of 97% in the wavelength range of 200 to 2500 nm at an incident angle of 0° to 60°, and an absorbance of 96% at 70°. Figure 7 and 8The surface and internal microstructures of the ultra-black coating prepared in this comparative example were further characterized (as shown in Figure 5 and 6 The results show that the light trap structure formed on the surface of the ultra-black coating prepared in Comparative Example 1 is significantly less than that of the ultra-black coating prepared in Example 1. This indicates that urea is gasified and removed at high temperature, resulting in a forest-like light trap structure, which has a significant impact on the construction of the microscopic morphology of the ultra-black coating.

[0047] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing an ultra-black coating with wide-angle absorption, characterized in that: include: (1) mixing carbon black, silica sol solution and ultrapure water uniformly to obtain a first slurry; (2) adding urea to the first slurry and mixing them evenly to obtain a second slurry; (3) pre-treating the surface of the aluminum sheet, spraying the first slurry and the second slurry on the pre-treated aluminum sheet in sequence, and drying after each spraying until the coating thickness is 100 to 150 μm, thereby obtaining a sample to be sintered; (4) The sample to be sintered is placed in a muffle furnace for sintering treatment to obtain an ultra-black coating with wide-angle absorption.

2. The preparation method according to claim 1, characterized in that: (1) The mass concentration of the silica sol solution is 30-40%, and the mass ratio of carbon black, silica sol solution and ultrapure water is 1.2:20:

30.

3. The preparation method according to claim 1, characterized in that: In (2), the mass ratio of the first slurry to urea is 50:0.

3.

4. The preparation method according to claim 1, characterized in that: (3) The surface pretreatment process of the aluminum sheet is as follows: after sandblasting to remove the surface oxide layer, use acetone to remove the surface oil stains, then soak in ethanol and deionized water for ultrasonic treatment, and finally dry for use.

5. The preparation method according to claim 1, characterized in that: (3) The spraying pressure is 20-40 psi, and the distance between the nozzle and the aluminum sheet is 5-10 cm.

6. The preparation method according to claim 1, characterized in that: (3) The drying process is as follows: natural drying at room temperature for 30 minutes, followed by drying at 100°C for 1 to 2 hours.

7. The preparation method according to claim 1, characterized in that: (4) The sintering process is as follows: the temperature is raised from room temperature to 400°C within 1 hour, then kept at this temperature for 1 hour, and cooled to room temperature to obtain an ultra-black coating.

8. An ultra-black coating with wide-angle absorption prepared by the method according to any one of claims 1 to 7.

9. The ultra-black coating with wide-angle absorption according to claim 8, characterized in that: At an incident angle of 0° to 70°, the absorbance in the wavelength range of 200 to 2500 nm is over 98%.

10. An application of the ultra-black coating according to claim 8, characterized in that: Used as an ultra-black coating for deep space exploration.

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