An ultrablack coating with wide-angle absorption and a preparation method and application thereof

Abstract

The application discloses an ultrablack coating with wide-angle absorption and a preparation method and application thereof, and belongs to the technical field of ultrablack coatings and preparation thereof. The application solves the problem that the existing ultrablack coating cannot present extremely low scattering and high absorption under large-angle incident light. In the application, carbon black is used as an absorbent, a high-temperature-resistant silica sol solution is used as a binder, and a one-step sintering method is adopted to form a stable structure and construct an ultrablack coating with a forest-like light trap array structure. The forest-like array structure on the surface of the ultrablack coating significantly changes the refractive index of the coating surface, thereby reducing the surface optical reflection; the surface forest-like light trap structure is closely arranged, can make the light incident from each angle to reflect back and forth in the structure, and then maximally absorbs the incident light, realizes stable high light absorption under wide angles, makes the reflectivity of the ultrablack coating not obviously change with the angle of incident light, and improves the deep space exploration precision of a space optical system.

Description

Technical Field

[0001] This invention relates to an ultra-black coating with wide-angle absorption, its preparation method and application, belonging to the field of ultra-black coating and its preparation technology. Background Technology

[0002] Stray light received by space optical systems during on-orbit operation is a significant factor affecting their detection accuracy. Ultra-black coatings can effectively absorb stray light from critical surfaces of space optical payloads, reducing imaging reflections and thus significantly improving the detection accuracy of space optical systems. The stray light suppression performance of ultra-black coatings is determined by the intrinsic light absorption characteristics of the pigments and resins. Currently, carbon-based, metal-based, and ceramic-based materials are commonly selected as coating pigments, and highly stable organic epoxy resins and inorganic potassium silicate resins are used as coating binders to form a stable structure. Carbon-based materials possess relatively ideal broad-spectrum intrinsic extinction properties; however, limited by interfacial scattering after coating formation, they typically exhibit low absorption rates in the ultraviolet-visible-near-infrared bands and show significant scattering under large-angle incident light, which is detrimental to achieving high-performance stray light suppression in ultra-black coatings.

[0003] The ultra-black coating maintains extremely low scattering and reflectivity under different incident angles, a characteristic particularly important for stray light suppression applications. Therefore, to address the light absorption structure design of the ultra-black coating, constructing a light-trapping structure that matches the incident light wavelength can effectively reduce the coating's effective refractive index, decrease Fresnel reflection, and improve the coating's wide-angle light absorption performance, allowing the ultra-black coating to maintain extremely high absorption even under large-angle incident light. While a forest-like light trap array can impart ultra-black coatings with extremely high light absorption, its forming conditions are demanding, currently relying on expensive processing equipment and often requiring vacuum, physical or chemical etching, and pre-fabrication templates. Furthermore, the resulting ultra-black coating cannot exhibit extremely low scattering and high absorption under large-angle incident light, failing to meet the stray light suppression requirements at different incident angles. Summary of the Invention

[0004] In order to solve the above-mentioned problems of existing super-black coatings, the present invention provides a super-black coating with wide-angle absorption, its preparation method and application.

[0005] The technical solution of the present invention:

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

[0007] (1) Mix carbon black, silica sol solution and ultrapure water evenly to obtain the first slurry;

[0008] (2) Add urea to the first slurry and mix well to obtain the second slurry;

[0009] (3) Pre-treat the surface of the aluminum sheet, spray the first slurry and the second slurry onto the pre-treated aluminum sheet in sequence, and dry it after each spraying until the coating thickness is 100-150μm to obtain the 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] Further specified, (1) the mass concentration of silica sol solution is 30-40%, and the mass ratio of carbon black, silica sol solution and ultrapure water is 1.2:20:30.

[0012] Further specifying, in (2), the mass ratio of the first slurry to urea is 50:0.3.

[0013] Further specifying, (3) the surface pretreatment process of aluminum sheet is as follows: after sandblasting to remove the surface oxide layer, acetone is used to remove surface oil stains, then it is soaked in ethanol and deionized water in sequence for ultrasonic treatment, and finally dried for later use.

[0014] Further specified, (3) the spraying pressure is 20 to 40 psi and the distance between the nozzle and the aluminum sheet is 5 to 10 cm.

[0015] Further specifying, the drying process in (3) is: after natural drying at room temperature for 30 minutes, dry at 100℃ for 1 to 2 hours.

[0016] Further specifying, (4) the sintering process is as follows: the temperature is raised from room temperature to 400℃ within 1 hour, then kept at that temperature for 1 hour, and then cooled to room temperature to obtain an ultra-black coating.

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

[0018] Further specified, the absorbance in the 200–2500 nm wavelength range reaches over 98% at incident angles of 0°–70°.

[0019] The third objective of this invention is to provide an application of the aforementioned ultra-black coating, specifically as an ultra-black coating for deep space exploration.

[0020] Beneficial effects:

[0021] This invention uses carbon black as an absorber to absorb incident light, and a high-temperature resistant silica sol solution as a binder to bond the carbon black. A one-step sintering method is employed to form a stable structure while simultaneously 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 alters the coating's refractive index and roughness, thereby changing its optical reflectivity and providing a mechanism for minimizing reflection. Furthermore, the densely packed light traps, resembling a forest, cause incident light to reflect back and forth within the structure, maximizing the absorption of all photons and achieving a stable high absorbency at wide angles. This ensures that the reflectivity of the ultra-black coating does not significantly change with the angle of incident light, improving the accuracy of deep space exploration in space optical systems. Compared with existing technologies, this invention also has the following advantages:

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

[0023] (2) The forest-like light trap structure on the surface of the super black coating prepared by the present invention is closely arranged, which enables light incident from various angles to be reflected back and forth inside its structure, thereby maximizing the absorption of incident light and achieving stable high light absorption under wide angle. This makes the reflectivity of the super black coating not change significantly with the angle of incident light, thus improving the accuracy of deep space exploration in space optical systems.

[0024] (3) The forest-like structure on the surface of the super black coating prepared by the present invention is micron-sized, which helps the coating to enhance multi-scale scattering of the structure under large incident light angles, thereby effectively improving the light absorption of the super black coating under oblique incidence, achieving a stable high absorption rate in a wide range, and improving the dependence of existing super black coatings on the incident light angle. Attached Figure Description

[0025] Figure 1 SEM image of the ultra-black coating surface prepared in Example 1;

[0026] Figure 2 SEM image 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 200–2500 nm wavelength range under different incident angles;

[0028] Figure 4 Absorbance mapping diagrams of the ultra-black coating prepared in Example 1 at different incident angles;

[0029] Figure 5 SEM image of the ultra-black coating surface prepared for Comparative Example 1;

[0030] Figure 6SEM image of the interior of the ultra-black coating prepared for Comparative Example 1;

[0031] Figure 7 The average absorbance of the ultra-black coating prepared in Comparative Example 1 in the 200–2500 nm wavelength range under different incident angles is shown.

[0032] Figure 8 The absorbance mapping diagram of the ultra-black coating prepared in Comparative Example 1 at different incident angles. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the 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 phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0037] Example 1

[0038] (1) Place 1.2g carbon black, 20g silica sol solution with a mass concentration of 40% and 30g ultrapure water into a mixing tank. After sonication for 30min at room temperature, use ultrasonic cutting and stirring at a speed of 1000r / min for 1h to obtain a uniformly mixed ultrablack slurry 1. Take 50g of ultrablack slurry 1, add 0.3g urea to it, and magnetically stir for 30min to mix evenly to prepare ultrablack slurry 2.

[0039] (2) The aluminum sheet is pretreated by sandblasting to remove the surface oxide layer, and the surface oil is removed with acetone. It is then soaked in ethanol and deionized water for ultrasonic treatment for 30 minutes and dried for later use.

[0040] (3) Using a spray gun, the two prepared slurries were sequentially and evenly sprayed onto the treated aluminum sheet, with the spraying pressure controlled at 40 psi and the nozzle distance from the aluminum sheet at 8 cm. First, super black slurry 1 was sprayed to a thickness of 70 μm. After spraying, it was dried at room temperature for 30 min, and then placed in a 100℃ forced-air drying oven for 2 h. Next, super black slurry 2 was sprayed to a thickness of 30 μm. After spraying, it was dried at room temperature for 30 min, and then placed in a 100℃ forced-air drying oven for 2 h to obtain a sample with a coating thickness of 100 μm to be sintered.

[0041] (5) Place the sample to be sintered into a muffle furnace, set the heating rate to 1h to heat to 400℃, and then keep it at 400℃ for 1h. After the urea in the coating is vaporized and removed, the ultra-black coating sample is obtained.

[0042] The surface microstructure of the obtained ultra-black coating was characterized, and the SEM images are shown below. Figure 1 As shown, by Figure 1 It can be seen that the coating surface exhibits a forest-like structure of micron-sized protrusions and light-trapping pores. Further characterization of the internal microstructure of the ultra-black coating is shown in the SEM images. Figure 2 As shown, by Figure 2 It can be seen that the interior exhibits a large number of porous structures. In summary, the ultra-black coating has a microscopic forest-like morphology. This microscopic morphology causes incident light rays at different angles to reflect back and forth within its structure, thereby increasing the optical path of the incident light within the coating. This greatly enhances 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 super-black coating in the 200–2500 nm wavelength range under different incident angles was tested, and the test results are as follows: Figure 3 and Figure 4 As shown in the figure, the super black coating can maintain a high absorption rate of over 98% in the 200-2500nm wavelength range under incident angles of 0° to 60°. At 70°, the absorbance can still reach 98%, achieving a relatively stable high absorption rate in a wide-angle range.

[0044] Comparative Example 1

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

[0046] The super-black coating prepared in this comparative example exhibits an internal energy absorbance of 97% in the 200–2500 nm wavelength range at incident angles of 0°–60°, and an absorbance of 96% at 70° (e.g., ...). Figure 7 and 8As shown), the surface and internal microstructure of the ultra-black coating prepared in this comparative example are significantly lower than those obtained in Example 1. Further characterization of the surface and internal microstructure of the ultra-black coating prepared in this comparative example (e.g.) Figure 5 and 6 As shown in the figure, the results indicate 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 suggests that the vaporization and removal of urea at high temperature creates a forest-like light trap structure, which has a significant impact on the construction of the microstructure of the ultra-black coating.

[0047] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing an ultra-black coating with wide-angle absorption, characterized in that, include: (1) Mix carbon black, silica sol solution and ultrapure water evenly to obtain the first slurry; (2) Add urea to the first slurry and mix well to obtain the second slurry; In step (2), the mass ratio of the first slurry to urea is 50:0.3; (3) Pre-treat the surface of the aluminum sheet, spray the first slurry and the second slurry onto the pre-treated aluminum sheet in sequence, and dry it after each spraying until the coating thickness is 100~150μm to obtain the 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. The sintering process in (4) is as follows: the temperature is raised from room temperature to 400°C within 1 hour, then kept at that temperature for 1 hour, and then cooled to room temperature to obtain an ultra-black coating.

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, (3) The surface pretreatment process of aluminum sheet is as follows: after sandblasting to remove the surface oxide layer, acetone is used to remove surface oil stains, and then it is soaked in ethanol and deionized water in sequence for ultrasonic treatment, and finally dried for later use.

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

5. The preparation method according to claim 1, characterized in that, (3) The drying process is as follows: after natural drying at room temperature for 30 minutes, dry at 100℃ for 1~2 hours.

6. A super-black coating with wide-angle absorption prepared by the method according to any one of claims 1 to 5.

7. The ultra-black coating with wide-angle absorption according to claim 6, characterized in that, At an incident angle of 0° to 70°, the absorbance in the 200 to 2500 nm wavelength range reaches over 98%.

8. An application of the ultra-black coating as described in claim 6, characterized in that, Used as an ultra-black coating for deep space exploration.

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