Preparation method of black high-emission thermal control coating on surface of aluminum-lithium alloy
By preparing a black high-emissivity thermal control coating on the surface of aluminum-lithium alloy using a phosphate-borate-copper-chromium black micro-arc oxidation electrolyte, the problems of unsatisfactory biotoxicity and infrared emissivity in existing technologies are solved, resulting in a dense, hard coating with high infrared emissivity, suitable for large-scale production applications.
Patent Information
- Application Number
- CN202511581519.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-16
AI Technical Summary
Existing methods for preparing black thermal control coatings on aluminum-lithium alloy surfaces suffer from high biotoxicity, high levels of heavy metals, and unsatisfactory infrared emissivity. In particular, there is a lack of research on related processes using copper chromium black as a colorant.
A black, high-emissivity thermal control coating is prepared by using a phosphate-borate-copper chromium black micro-arc oxidation electrolyte on the surface of an aluminum-lithium alloy through micro-arc oxidation treatment. The electrolyte is non-toxic and environmentally friendly, and copper chromium black acts as a colorant in the coating film-forming reaction, improving the coating density and infrared emissivity.
The prepared black high-emissivity thermal control coating has a dense microstructure, high hardness, and high infrared emissivity. The electrolyte is environmentally friendly and suitable for large-scale production. The coating has a strong metallurgical bond with the substrate, significantly improves hardness, and achieves an infrared emissivity of up to 0.92.
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Figure CN121344718A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal material surface treatment technology, specifically a method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy. Background Technology
[0002] Aluminum-lithium alloys possess high specific strength, good corrosion resistance, and excellent processing performance, making them a key material for lightweight spacecraft manufacturing and offering broad application prospects. In the space environment, the surfaces of high-speed spacecraft must withstand complex and variable environmental challenges, including impacts from space particles, ion radiation, atomic oxygen corrosion, and thermal cycling, posing significant challenges to the long lifespan and stable operation of spacecraft. However, the inherent low hardness and poor thermal control properties of aluminum-lithium alloys limit their further application in the aerospace field. Therefore, aluminum-lithium alloys used in aerospace typically require surface treatment to improve their overall surface properties.
[0003] With the development of surface technology, micro-arc oxidation technology has attracted increasing attention. By introducing colorants such as vanadates, tungstates, and manganates into the electrolyte, micro-arc oxidation technology can prepare black thermal control coatings with different properties on aluminum alloy surfaces. These coatings are characterized by high hardness and good thermal control performance, and are widely used in spacecraft surface modification and optical instrument matting. However, many of the black colorants commonly used in micro-arc oxidation electrolytes are biotoxic or have high levels of heavy metals, which are not environmentally friendly or good for human health. Furthermore, the infrared emissivity of the prepared black thermal control coatings is not ideal, making it difficult to meet actual service requirements. On the other hand, there are few reports on the related processes and performance studies of preparing black thermal control coatings on aluminum-lithium alloy surfaces using micro-arc oxidation technology, especially using copper chromium black as a colorant, which urgently needs further research and exploration. Therefore, how to develop a method for preparing a high-emissivity black thermal control coating on aluminum-lithium alloy surfaces using copper chromium black is a technical problem that needs to be seriously addressed. Summary of the Invention
[0004] In view of the above situation and to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a black high-emissivity thermal control coating on the surface of aluminum-lithium alloy, which can effectively solve the problem of preparing a black high-emissivity thermal control coating on the surface of aluminum-lithium alloy. The resulting thermal control coating has a dense microstructure, high hardness, and high infrared emissivity.
[0005] To achieve the objective of this invention, the technical solution is a method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy, which is accomplished through the following steps: S1, Material Pretreatment S1.1, Surface pretreatment of aluminum-lithium alloy Use 400#, 600#, 800#, 1000#, 1200#, and 1500# silicon carbide sandpaper in sequence to polish and clean the surface of the aluminum-lithium alloy until a clean metal substrate is exposed. Then clean it with anhydrous ethanol, rinse it with deionized water, and blow it dry for later use. S1.2, Copper Chromium Black Pretreatment Copper chromium black pretreatment: The copper chromium black is ultrasonically cleaned in anhydrous ethanol for 30-50 min at 40 kHz, then centrifuged at 8000-10000 r / min for 15-30 min. After discarding the cleaning solution, the obtained copper chromium black is placed in a vacuum drying oven and dried at 80-130℃ for 1-3 h for later use. S2, Preparation of micro-arc oxidation electrolyte First, phosphate, borate, organic additives, and alkaline compounds are added sequentially to deionized water and magnetically stirred at 800–1200 rpm for 15–30 min to ensure complete dissolution. Then, copper chromate black is added as a colorant, and the mixture is magnetically stirred at 1600–2000 rpm for 30–60 min until the solution is evenly dispersed, thus obtaining the micro-arc oxidation electrolyte. The composition of the micro-arc oxidation electrolyte is as follows: phosphate concentration of 15-40 g / L, borate concentration of 5-15 g / L, organic additive concentration of 3-8 ml / L, colorant copper chromate black concentration of 2-10 g / L, and alkaline compound concentration of 2-8 g / L.
[0006] The phosphate mentioned is sodium hexametaphosphate; The borate mentioned is sodium tetraborate; The organic additive mentioned is triethanolamine; The alkaline compound is sodium hydroxide; The particle size of the colorant copper chromium black is 0.1–1.0 μm; Preparation of S3 Black High-Emittance Thermal Control Coating The pretreated aluminum-lithium alloy sample was placed in a stainless steel electrolytic cell of a micro-arc oxidation device. The aluminum-lithium alloy was used as the micro-arc oxidation anode, and the stainless steel electrolytic cell as the micro-arc oxidation cathode. The micro-arc oxidation electrolyte prepared in step S2 was added to the stainless steel electrolytic cell. During the micro-arc oxidation process, the electrolyte was continuously mechanically stirred at a speed of 1000–2000 r / min. The sample was then subjected to micro-arc oxidation treatment using a micro-arc oxidation power source to obtain a black high-emissivity thermally controlled coating on the sample surface. The micro-arc oxidation process parameters were as follows: Current: 6–12 A / dm³ 2The frequency is 200-600 Hz, the duty cycle is 15-45%, the electrolyte temperature is adjusted to 15-30℃ using a low-temperature constant temperature bath, and the micro-arc oxidation treatment time is 20-50 min. After the micro-arc oxidation treatment, the obtained sample is ultrasonically treated in anhydrous ethanol at 40 kHz for 10-30 min, then taken out and air-dried naturally to obtain a black high-emission thermal control coating with a thickness of 30-70 μm on the surface of aluminum-lithium alloy.
[0007] This invention employs a phosphate-borate-colorant electrolyte system to prepare a black high-emissivity thermal control coating on the surface of an aluminum-lithium alloy using micro-arc oxidation technology. The electrolyte used has a simple composition, is non-toxic and environmentally friendly, and can be reused, making it suitable for large-scale production applications. The black high-emissivity thermal control coating prepared on the surface of the aluminum-lithium alloy using copper chromium black (common chemical name: copper chromite, chemical formula CuCr2O4) as a colorant has a dense microstructure, high hardness, and high infrared emissivity. This is a major innovation in the field of metal material surface treatment technology and has practical application value. Attached Figure Description
[0008] Figure 1 This is a microstructure diagram of the black high-emission thermal control coating on the aluminum-lithium alloy surface prepared in Example 1 of the present invention. Figure 2 This is a microstructure diagram of the black high-emission thermal control coating on the aluminum-lithium alloy surface prepared in Example 2 of the present invention. Figure 3 This is a microstructure diagram of the black high-emission thermal control coating on the aluminum-lithium alloy prepared in Example 3 of the present invention. Figure 4 The images show the XRD patterns of the black high-emission thermal control coatings on the surface of the aluminum-lithium alloy prepared in Examples 1-3 of this invention. Figure 5 Infrared emissivity images of the black high-emission thermal control coating on the surface of the aluminum-lithium alloy prepared in Examples 1-3 of this invention. Detailed Implementation
[0009] The specific implementation of the present invention will be described in detail below with reference to examples and specific circumstances.
[0010] The present invention can be described in the following embodiments. Example
[0011] A method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy comprises the following steps: S1, Material Pretreatment S1.1, Surface pretreatment of aluminum-lithium alloy First, use 400#, 600#, 800#, 1000#, 1200#, and 1500# silicon carbide sandpaper to polish and clean the surface of 2099 aluminum-lithium alloy (size: diameter 25mm, thickness 5mm) until a clean metal substrate is exposed. Then, clean it with anhydrous ethanol, rinse the sample thoroughly with deionized water, and blow it dry for later use. S1.2, Copper Chromium Black Pretreatment: The copper chromium black was ultrasonically cleaned in anhydrous ethanol for 35 min at 40 kHz, then centrifuged at 9500 r / min for 20 min. After discarding the cleaning solution, the obtained copper chromium black was placed in a vacuum drying oven and dried at 100℃ for 2.0 h for later use. S2. Preparation of micro-arc oxidation electrolyte First, 150g of sodium hexametaphosphate, 50g of sodium tetraborate, 25ml of triethanolamine, and 25g of sodium hydroxide were added sequentially to deionized water to a total volume of 5L. The mixture was then magnetically stirred at 850r / min for 30min to ensure complete dissolution. Subsequently, 22.5g of copper chromate black (0.2μm particle size) was added, and the mixture was magnetically stirred at 2000r / min for 30min until the solution was uniformly dispersed, thus obtaining the micro-arc oxidation electrolyte. S3. Preparation of functional film layers The pretreated 2099 aluminum-lithium alloy sample was placed in the stainless steel electrolytic cell of the micro-arc oxidation equipment. The aluminum-lithium alloy was used as the micro-arc oxidation anode, and the stainless steel electrolytic cell as the micro-arc oxidation cathode. The micro-arc oxidation electrolyte prepared in step S2 was added to the stainless steel electrolytic cell. During the micro-arc oxidation process, the electrolyte was continuously mechanically stirred at a speed of 1350 r / min. The sample was subjected to micro-arc oxidation treatment using a micro-arc oxidation power supply. The micro-arc oxidation process parameters were as follows: Current: 8 A / dm 2 The frequency was 300 Hz, the duty cycle was 25%, and the temperature of the micro-arc oxidation electrolyte was adjusted to 25 ℃ using a low-temperature constant temperature bath. The micro-arc oxidation treatment time was 25 min. Then, the sample was ultrasonically treated in anhydrous ethanol at 40 kHz for 20 min. The sample was then taken out and air-dried naturally to obtain a black high-emission thermal control coating with a thickness of 36 μm on the surface of the aluminum-lithium alloy. Example
[0012] A method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy comprises the following steps: S1, Material Pretreatment S1.1, Surface pretreatment of aluminum-lithium alloy First, use 400#, 600#, 800#, 1000#, 1200#, and 1500# silicon carbide sandpaper to polish and clean the surface of 2099 aluminum-lithium alloy (size: diameter 25mm, thickness 5mm) until a clean metal substrate is exposed. Then, clean it with anhydrous ethanol. Finally, rinse the sample thoroughly with deionized water and blow it dry for later use. S1.2, Copper Chromium Black Pretreatment: The copper chromium black was ultrasonically cleaned in anhydrous ethanol for 30 min at 40 kHz, then centrifuged at 8000 r / min for 30 min. After discarding the cleaning solution, the copper chromium black was placed in a vacuum drying oven and dried at 95℃ for 3 h for later use. S2. First, add 175g sodium hexametaphosphate, 40g sodium tetraborate, 20ml triethanolamine, and 22.5g / L sodium hydroxide to deionized water to a total volume of 5L. Stir magnetically at 1100r / min for 20min to ensure complete dissolution of the added substances. Then, add 30g copper chromate black colorant with a particle size of 0.5μm. Stir the mixed solution magnetically at 1700r / min for 45min until the solution is evenly dispersed to obtain the micro-arc oxidation electrolyte. S3. The pretreated 2099 aluminum-lithium alloy sample is placed in the stainless steel electrolytic cell of the micro-arc oxidation equipment. The aluminum-lithium alloy is used as the micro-arc oxidation anode, and the stainless steel electrolytic cell is used as the micro-arc oxidation cathode. The micro-arc oxidation electrolyte prepared in step S2 is added to the stainless steel electrolytic cell. During the micro-arc oxidation process, the electrolyte is continuously mechanically stirred at a speed of 1200 r / min. The sample is micro-arc oxidized using a micro-arc oxidation power supply to obtain a black high-emissivity thermal control coating on the sample surface. The micro-arc oxidation process parameters are as follows: Current: 7A / dm 2 The frequency was 320 Hz, the duty cycle was 20%, the electrolyte temperature was adjusted to 22 ℃ using a low-temperature constant temperature bath, and the micro-arc oxidation treatment time was 45 min. After the micro-arc oxidation treatment, the obtained sample was subjected to ultrasonic treatment at 40 kHz for 22 min in anhydrous ethanol. Then the sample was taken out and air-dried naturally to obtain a black high-emission thermal control coating with a thickness of 63 μm on the surface of the aluminum-lithium alloy. Example
[0013] A method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy comprises the following steps: S1, Material Pretreatment S1.1, Surface pretreatment of aluminum-lithium alloy First, use 400#, 600#, 800#, 1000#, 1200#, and 1500# silicon carbide sandpaper to polish and clean the surface of 2099 aluminum-lithium alloy (size: diameter 25mm, thickness 5mm) until a clean metal substrate is exposed. Then, clean it with anhydrous ethanol. Finally, rinse the sample thoroughly with deionized water and blow it dry for later use. S1.2, Copper Chromium Black Pretreatment: The copper chromium black was ultrasonically cleaned in anhydrous ethanol for 40 min at 40 kHz, then centrifuged at 9800 r / min for 17 min. After discarding the cleaning solution, the copper chromium black was placed in a vacuum drying oven and dried at 125℃ for 1.5 h for later use. S2. First, add 140g sodium hexametaphosphate, 55g sodium tetraborate, 27.5ml triethanolamine, and 32.5g / L sodium hydroxide to deionized water to a total volume of 5L. Stir magnetically at 950r / min for 25min to ensure complete dissolution of the added substances. Then, add 47.5g copper chromate black colorant with a particle size of 0.3μm. Stir the mixed solution magnetically at 1800r / min for 40min until the solution is evenly dispersed to obtain the micro-arc oxidation electrolyte. S3. The pretreated 2099 aluminum-lithium alloy sample is placed in the stainless steel electrolytic cell of the micro-arc oxidation equipment. The aluminum-lithium alloy is used as the micro-arc oxidation anode, and the stainless steel electrolytic cell is used as the micro-arc oxidation cathode. The micro-arc oxidation electrolyte prepared in step S2 is added to the stainless steel electrolytic cell. During the micro-arc oxidation process, the electrolyte is continuously mechanically stirred at a speed of 1800 r / min. The sample is micro-arc oxidized using a micro-arc oxidation power supply to obtain a black high-emissivity thermal control coating on the sample surface. The micro-arc oxidation process parameters are as follows: Current: 9 A / dm 2 The frequency was 280 Hz, the duty cycle was 30%, the electrolyte temperature was adjusted to 23 ℃ using a low-temperature constant temperature bath, and the micro-arc oxidation treatment time was 35 min. After the micro-arc oxidation treatment, the obtained sample was ultrasonically treated in anhydrous ethanol at 40 kHz for 25 min. Then the sample was taken out and air-dried naturally to obtain a black high-emission thermal control coating with a thickness of 45 μm on the surface of aluminum-lithium alloy.
[0014] It should be noted that the above descriptions are merely illustrative embodiments used to illustrate specific implementations of the present invention, and are not intended to limit the present invention in any form or substance. It should be pointed out that those skilled in the art can make several improvements and additions without departing from the method of the present invention, but these improvements and additions are essentially the same as the technical solution of this application, and should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention; at the same time, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.
[0015] This invention utilizes a phosphate-borate-colorant electrolyte system and micro-arc oxidation technology to prepare a black high-emissivity thermal control coating on the surface of aluminum-lithium alloys. The electrolyte composition is simple, non-toxic, environmentally friendly, and reusable, making it suitable for large-scale production applications. The black high-emissivity thermal control coating prepared on the aluminum-lithium alloy surface using copper chromium black as a colorant exhibits a dense microstructure, high hardness, and high infrared emissivity. Experiments have shown that it achieves very good and beneficial technical results. Relevant information is as follows: 1. Hardness Measurement The black high-emission thermal control coatings on the surface of the aluminum-lithium alloy prepared in Examples 1-3 were subjected to microhardness tests, and their hardness values were 1270HV, 1345HV and 1310HV, respectively.
[0016] 2. Microscopic morphology determination The surface microstructure of the black high-emission thermal control coating on the aluminum-lithium alloy prepared in Example 1 of this invention is shown in [the figure]. Figure 1 As can be seen, its coating has a dense structure and few pores; The surface microstructure of the black high-emission thermal control coating on the aluminum-lithium alloy prepared in Example 2 of this invention is shown in [the figure]. Figure 2 As can be seen, its coating has a large number of dense areas, and the number of micropores in the coating is small and the pore size is small, which is beneficial to improving the coating hardness. The surface microstructure of the black high-emission thermal control coating on the aluminum-lithium alloy prepared in Example 3 of this invention is shown in [the figure]. Figure 3 It can be seen that the coating has few micropores and microcracks and high coating density.
[0017] 3. XRD pattern determination XRD patterns of the black high-emission thermal control coatings on the surface of the aluminum-lithium alloy prepared in Examples 1-3 of this invention are shown in [the original text]. Figure 4The analysis results showed that copper chromium black was present in the phase composition of the coating, indicating that the copper chromium black added to the electrolyte effectively participated in the coating film-forming reaction and became a component of the thermal control coating.
[0018] 4. Infrared emissivity measurement The infrared emissivity of the black high-emissivity thermal control coatings on the surface of the aluminum-lithium alloy prepared by the methods in Examples 1-3 was measured, and the infrared emissivity was found to be 0.88, 0.91 and 0.92 respectively.
[0019] In summary, the coating prepared by the method of this invention has a dense microstructure, high hardness, and high infrared emissivity. Compared with the prior art, its main advantages are: (1) The present invention uses a phosphate-borate-colorant system electrolyte. The electrolyte composition does not contain heavy metals or toxic substances. The electrolyte formula is non-toxic and environmentally friendly, and is suitable for large-scale production applications. (2) The thickness of the black high-emissivity thermal control coating can be controlled by adjusting the processing time during the micro-arc oxidation process. Specifically, when the micro-arc oxidation time is 20–30 min, the thickness of the obtained black high-emissivity thermal control coating is 30–40 μm; when the micro-arc oxidation time is 30–40 min, the thickness of the obtained black high-emissivity thermal control coating is 40–60 μm; and when the micro-arc oxidation time is 40–50 min, the thickness of the obtained black high-emissivity thermal control coating is 60–70 μm. (3) The black high-emissivity thermal control coating is formed in situ on the surface of the aluminum-lithium alloy. The coating and the substrate are metallurgically bonded, and the bond is strong and not easy to fall off. Copper chromium black, as a second phase, participates in the micro-arc oxidation film formation reaction, effectively filling the pores and cracks in the coating, improving the density and structural integrity of the coating, thereby increasing the hardness of the coating. The black high-emissivity thermal control coating prepared by the method of the present invention has a hardness of 1240-1350 HV, which is significantly higher than the thermal control coating prepared in the electrolyte without copper chromium black (with the same other components) (hardness of 820-860 HV). (4) The introduction of copper chromium black into the electrolyte used in the method of the present invention results in a black thermal control coating, indicating that copper chromium black significantly deepens the coating color and improves the infrared emissivity of the black high-emissivity thermal control coating. Testing shows that the infrared emissivity of the black high-emissivity thermal control coating prepared by the method of the present invention can reach 0.92, which is a major innovation in the field of metal material surface treatment technology and has practical application value.
Claims
1. A method for preparing a black high-emissivity thermal control coating on the surface of an aluminum-lithium alloy, characterized in that, It is realized by the following steps: S1, material pretreatment S1.1, aluminum lithium alloy surface pretreatment The surface of the aluminum lithium alloy is polished and cleaned with 400#, 600#, 800#, 1000#, 1200# and 1500# silicon carbide sandpaper in sequence until the clean metal matrix is exposed, then washed with anhydrous ethanol, rinsed with deionized water, and dried for standby; S1.2, copper chromium black pretreatment Copper chromium black pretreatment: ultrasonic cleaning treatment of copper chromium black in anhydrous ethanol for 30-50 min at 40 KHz, then centrifuged in a centrifuge at a speed of 8000-10000 r / min for 15-30 min, after discarding the cleaning solution, the obtained copper chromium black is placed in a vacuum drying oven and dried at 80-130°C for 1-3 h for standby; S2, preparation of micro-arc oxidation electrolyte First, add phosphate, borate, organic additive and alkaline compound into deionized water in sequence, and magnetically stir at a speed of 800-1200 r / min for 15-30 min to ensure complete dissolution of the added substances; then add the colorant copper chromium black, and magnetically stir the mixed solution at a speed of 1600-2000 r / min for 30-60 min until the solution is uniformly dispersed, to obtain the micro-arc oxidation electrolyte; The content of each component of the micro-arc oxidation electrolyte is: phosphate concentration is 15-40 g / L, borate concentration is 5-15 g / L, organic additive concentration is 3-8 ml / L, colorant copper chromium black concentration is 2-10 g / L, and alkaline compound concentration is 2-8 g / L; The phosphate is sodium hexametaphosphate; The borate is sodium tetraborate; The organic additive is triethanolamine; The alkaline compound is sodium hydroxide; The particle size of the colorant copper chromium black is 0.1-1.0 μm; S3, preparation of black high-emission thermal control coating The pretreated aluminum-lithium alloy sample is placed in a stainless steel electrolytic cell of a micro-arc oxidation device, the aluminum-lithium alloy is used as a micro-arc oxidation anode, the stainless steel electrolytic cell is used as a micro-arc oxidation cathode, the micro-arc oxidation electrolyte configured in step S2 is added into the stainless steel electrolytic cell, mechanical stirring is continuously implemented on the electrolyte during the micro-arc oxidation process, and the rotating speed is 1000-2000 r / min; the micro-arc oxidation power source is used to perform micro-arc oxidation treatment on the sample, and a black high-emission thermal control coating is obtained on the surface of the sample; the micro-arc oxidation treatment process parameters are as follows: current: 6-12 A / dm 2 , frequency: 200-600 Hz, duty cycle: 15-45%, the temperature of the electrolyte is adjusted by a low-temperature constant-temperature tank to be 15-30 ℃, and the micro-arc oxidation treatment time is 20-50 min; after the micro-arc oxidation treatment is completed, the obtained sample is subjected to ultrasonic treatment in anhydrous ethanol at 40 KHz for 10-30 min, then taken out, and naturally dried, so that a black high-emission thermal control coating product with a thickness of 30-70 μm on the surface of the aluminum-lithium alloy is obtained.
2. The method of claim 1, wherein the aluminum-lithium alloy surface black high-emissivity thermal control coating is prepared by the steps of: It is realized by the following steps: S1, material pretreatment S1.1, aluminum lithium alloy surface pretreatment First, polish and clean the surface of 2099 aluminum lithium alloy (size: diameter 25 mm, thickness 5 mm) with 400#, 600#, 800#, 1000#, 1200# and 1500# silicon carbide sandpaper in sequence until the clean metal matrix is exposed, then wash with anhydrous ethanol, rinse the sample with deionized water, and dry for standby; S1.2, copper chromium black pretreatment: ultrasonic cleaning treatment of copper chromium black in anhydrous ethanol for 35 min at 40 KHz, then centrifuged in a centrifuge at a speed of 9500 r / min for 20 min, after discarding the cleaning solution, the obtained copper chromium black is placed in a vacuum drying oven and dried at 100°C for 2.0 h for standby; S2, preparation of micro-arc oxidation electrolyte Firstly, 150g sodium hexametaphosphate, 50g sodium tetraborate, 25ml triethanolamine, 25g sodium hydroxide were added into deionized water to 5L (i.e. total volume 5L) in turn, and magnetic stirring was carried out at 850r / min for 30min to ensure that the added substances were completely dissolved; then 22.5g colorant copper chromium black with a particle size of 0.2μm was added, and the mixed solution was magnetically stirred at 2000r / min for 30min until the solution was uniformly dispersed, thereby obtaining a micro-arc oxidation electrolyte; S3, preparation of functional film layer The pretreated 2099 aluminum lithium alloy sample is placed in a stainless steel electrolytic cell of a micro-arc oxidation device, the aluminum lithium alloy is used as a micro-arc oxidation anode, the stainless steel electrolytic cell is used as a micro-arc oxidation cathode, the micro-arc oxidation electrolyte configured in step S2 is added into the stainless steel electrolytic cell, mechanical stirring with a rotating speed of 1350 r / min is continuously performed on the electrolyte during the micro-arc oxidation process, and the sample is subjected to micro-arc oxidation treatment by using a micro-arc oxidation power supply; the micro-arc oxidation treatment process parameters are as follows: current: 8 A / dm 2 , frequency: 300 Hz, duty cycle: 25%, the temperature of the micro-arc oxidation electrolyte is adjusted to 25 DEG C by using a low-temperature constant-temperature tank, and the micro-arc oxidation treatment time is 25 min; then the sample is subjected to ultrasonic treatment in anhydrous ethanol at 40 KHz for 20 min, the sample is taken out, and is naturally dried, and thus a black high-emission thermal control coating product with a thickness of 36 mu m on the surface of the aluminum lithium alloy is obtained.
3. The method for preparing a black high-emission thermal control coating on the surface of an aluminum-lithium alloy according to claim 1, characterized in that, The following steps are implemented: S1, material pretreatment S1.1, surface pretreatment of aluminum lithium alloy Firstly, 400#, 600#, 800#, 1000#, 1200# and 1500# silicon carbide sandpaper were used to polish and clean the surface of 2099 aluminum lithium alloy (size: diameter 25mm, thickness 5mm) until the clean metal matrix was exposed, then the sample was washed with anhydrous ethanol, and finally the sample was washed with deionized water and dried for standby; S1.2, copper chromium black pretreatment: The copper chromium black was ultrasonically cleaned in anhydrous ethanol for 30min at 40KHz, then centrifuged at 8000r / min for 30min, and the cleaning solution was discarded. The obtained copper chromium black was dried in a vacuum drying oven at 95℃ for 3h for standby; S2, firstly, 175g sodium hexametaphosphate, 40g sodium tetraborate, 20ml triethanolamine, 22.5g / L sodium hydroxide were added into deionized water to 5L (i.e. total volume 5L) in turn, and magnetic stirring was carried out at 1100r / min for 20min to ensure that the added substances were completely dissolved; then 30g colorant copper chromium black with a particle size of 0.5μm was added, and the mixed solution was magnetically stirred at 1700r / min for 45min until the solution was uniformly dispersed, thereby obtaining a micro-arc oxidation electrolyte; S3, the pretreated 2099 aluminum lithium alloy sample was placed in a stainless steel electrolytic cell of a micro-arc oxidation device, the aluminum lithium alloy was used as a micro-arc oxidation anode, the stainless steel electrolytic cell was used as a micro-arc oxidation cathode, the micro-arc oxidation electrolyte prepared in step S2 was added into the stainless steel electrolytic cell, and mechanical stirring was carried out on the electrolyte without interruption during the micro-arc oxidation process at a speed of 1200r / min; the sample was treated by micro-arc oxidation using a micro-arc oxidation power supply, and a black high-emission thermal control coating was obtained on the surface of the sample; The micro-arc oxidation treatment process parameters are as follows: current: 7A / dm 2 , frequency: 320Hz, duty cycle: 20%, the temperature of electrolyte is adjusted to 22 DEG C by using a low-temperature constant temperature tank, the micro-arc oxidation treatment time is 45min; after the micro-arc oxidation treatment, the obtained sample is subjected to ultrasonic treatment in anhydrous ethanol for 22min at 40KHz, then the sample is taken out and naturally dried, thereby obtaining a black high-emission thermal control coating product with a thickness of 63um on the surface of the aluminum-lithium alloy.
4. The method of claim 1, wherein the aluminum-lithium alloy surface black high-emissivity thermal control coating is prepared by the steps of: The following steps are implemented: S1, material pretreatment S1.1, surface pretreatment of aluminum lithium alloy Firstly, 400#, 600#, 800#, 1000#, 1200# and 1500# silicon carbide sandpaper were used to polish and clean the surface of 2099 aluminum lithium alloy (size: diameter 25mm, thickness 5mm) until the clean metal matrix was exposed, then the sample was washed with anhydrous ethanol, and finally the sample was washed with deionized water and dried for standby; S1.2, copper chromium black pretreatment: The copper chromium black was subjected to ultrasonic cleaning treatment in anhydrous ethanol for 40 min at 40 KHz, and then was centrifuged in a centrifuge at a speed of 9800 r / min for 17 min. After the cleaning solution was discarded, the obtained copper chromium black was dried in a vacuum drying box at 125 ℃ for 1.5 h, and was reserved for use; S2, first, 140 g of sodium hexametaphosphate, 55 g of sodium tetraborate, 27.5 ml of triethanolamine, and 32.5 g / L of sodium hydroxide were sequentially added to deionized water to 5 L (i.e., the total volume was 5 L), and then the mixture was stirred at a speed of 950 r / min for 25 min to ensure that the added substances were completely dissolved; then 47.5 g of colorant copper chromium black with a particle size of 0.3 μm was added, and the mixed solution was stirred at a speed of 1800 r / min for 40 min to obtain a micro-arc oxidation electrolyte; S3, the pretreated 2099 aluminum lithium alloy sample was placed in a stainless steel electrolytic cell of a micro-arc oxidation device, the aluminum lithium alloy was used as a micro-arc oxidation anode, the stainless steel electrolytic cell was used as a micro-arc oxidation cathode, the micro-arc oxidation electrolyte prepared in step S2 was added to the stainless steel electrolytic cell, and the electrolyte was continuously mechanically stirred at a speed of 1800 r / min during the micro-arc oxidation process; the sample was subjected to micro-arc oxidation treatment by using a micro-arc oxidation power supply, and a black high-emission thermal control coating was obtained on the surface of the sample; The micro-arc oxidation treatment process parameters are as follows: current: 9A / dm 2 , frequency: 280Hz, duty cycle: 30%, the temperature of electrolyte is adjusted to 23 DEG C by using a low-temperature constant temperature tank, the micro-arc oxidation treatment time is 35 min; after the micro-arc oxidation treatment, the obtained sample is subjected to ultrasonic treatment in anhydrous ethanol for 40KHz for 25 min, then the sample is taken out and naturally dried, thereby obtaining a black high-emission thermal control coating product with a thickness of 45 mu m on the surface of the aluminum-lithium alloy.