Rapid preparation method of charged lunar dust protection thermal control structure suitable for large-area application

Abstract

The invention discloses a rapid preparation method of a charged lunar dust protection thermal control structure suitable for large-area application, and belongs to the technical field of functional material preparation. The problem that the thermal control performance of an existing thermal control coating is rapidly reduced due to the influence of lunar dust is solved. According to the thermal control coating and the preparation method thereof, firstly, conductivity of the thermal control coating is achieved by doping conductive particles, then a microstructure with a proper size is constructed on the surface of the thermal control coating by taking low-surface-energy fluoropolyurethane as a binder and filler particle nano silicon dioxide, and Van der Waals' force between the coating and lunar dust is reduced; the sprayed thermal control coating still has good bulk resistivity, electrostatic adhesion is reduced, charged lunar dust protection is achieved, the surface of the coating is modified through low-surface-energy fluoropolyurethane, the lunar dust protection thermal control coating is obtained, and meanwhile nano SiO2 and fluoropolyurethane both have good spatial stability and adapt to the extreme environment of the lunar surface.

Description

Technical Field

[0001] The present invention relates to a rapid preparation method for a charged lunar dust protection thermal control structure suitable for large-area applications, belonging to the technical field of functional material preparation. Background Art

[0002] Thermal control coatings are coatings on the surface of spacecraft that control and regulate the reflection of sunlight and the infrared emissivity to ensure the internal working temperature balance of the spacecraft, and are important devices for realizing thermal control of spacecraft. Due to meteorite impacts and long-term weathering on the lunar surface, a layer of lunar dust particles with small particle size and irregular shapes is formed. At the same time, due to long-term exposure to space radiation, the lunar dust surface is loaded with abundant charges. During the exploration of lunar probes, lunar dust particles are extremely easy to adhere to the surface of lunar rovers due to their small particle size, large specific surface area, and low surface energy, resulting in a decline in thermal control performance, leading to thermal imbalance of the spacecraft and damage to the interior of the spacecraft. Therefore, there is an urgent need to develop a charged lunar dust protection thermal control coating. Such a coating must have the following requirements: First, this thermal control coating must have a low solar absorptance and a high infrared emissivity to ensure its efficient thermal control performance; second, this thermal control coating must have a low surface energy surface with a suitable size microstructure to reduce the adhesion of lunar dust caused by van der Waals forces; finally, this thermal control coating must have a suitable volume resistivity to reduce the electrostatic adhesion of lunar dust.

[0003] At present, there are various types of thermal control coatings, mainly including second surface mirrors, ceramic protection materials, and thermal control white paints, etc. Among them, thermal control white paint is widely applied to the surfaces of various spacecraft due to its simple preparation process, easy large-area spraying, good designability, excellent thermal control performance, etc. And organic thermal control white paint is more widely used in spacecraft due to its light weight and good bonding strength. Conductive thermal control white paint is mainly composed of an organic binder, conductive fillers, and white fillers. In the application of the space environment, thermal control white paint must have a certain conductivity to cope with the charging and discharging effects of the space environment. The common conductive method is to conductively modify through nanoparticles, so that the thermal control coating has a relatively low volume resistivity. The relatively low volume resistivity of the thermal control coating can significantly reduce the electrostatic adhesion of lunar dust.

[0004] However, due to their small particle size, large specific surface area, and high surface energy, the lunar dust particles widely distributed on the lunar surface are extremely likely to strongly adhere to the surface of the thermal control coating due to the action of van der Waals forces, resulting in a decline in the performance of the thermal control coating. The adhesion of lunar dust particles is usually caused by the combined action of van der Waals forces and electrostatic forces. In order to effectively protect against lunar dust, it is necessary to reduce the influence brought by these two forces. To reduce van der Waals forces, appropriate roughness can be constructed on the surface and the surface energy can be reduced. The application of thermal control coatings in the space environment usually has certain anti-static requirements, which can significantly reduce the adhesion caused by electrostatic forces. Therefore, in order to avoid the adhesion of lunar dust, existing research mainly focuses on reducing van der Waals forces. In order to reduce the adhesion of lunar dust on the surface of the thermal control coating caused by van der Waals forces, a low surface energy surface with appropriate micro-scale dimensions must be constructed on the surface of the thermal control coating. However, in the existing technology during surface modification, microstructures are usually constructed on the coating surface using nanoparticles and binders, and the surface is modified with low surface energy. However, the above methods often face problems such as complex processes and numerous steps, severely limiting their large-area application. Summary of the Invention

[0005] In order to solve the problem that the thermal control performance of the existing thermal control coating rapidly deteriorates due to the influence of lunar dust, the present invention provides a charged lunar dust protection thermal control coating, its preparation method, and application.

[0006] Technical solution of the present invention:

[0007] One of the objectives of the present invention is to provide a preparation method of a charged lunar dust protection thermal control coating, which includes the following steps:

[0008] (1) Coating AZO on the surface of ZrO2 using atomic layer deposition technology to obtain AZO@ZrO2 powder;

[0009] (2) Mixing the AZO@ZrO2 powder, fluorinated polyurethane, and butyl acetate evenly to obtain AZO@ZrO2 thermal control slurry, and spraying the AZO@ZrO2 thermal control slurry on the surface of the substrate by spraying to obtain an anti-static AZO@ZrO2 thermal control coating;

[0010] (3) Mixing hydrophobic silica, fluorinated polyurethane, and butyl acetate evenly to obtain SiO2 hydrophobic dust-proof slurry, and spraying the SiO2 hydrophobic dust-proof slurry on the surface of the anti-static AZO@ZrO2 thermal control coating by the same spraying method as in (2) to obtain a charged lunar dust protection thermal control coating.

[0011] Further limitation: The operation process of (1) is as follows: Place nano-ZrO2 powder in the deposition chamber of an atomic layer deposition instrument, set the deposition pressure to 0.15 torr, the temperature to 140 °C, the rotation speed of the drum-type deposition chamber to 600 r / min, the atomic ratio of zinc to aluminum to 23:1, the spraying source time for each deposition growth cycle to 60 s, and repeat the process for 48 cycles.

[0012] Further limitation: In (2), the mass-volume ratio of AZO@ZrO2 powder, fluoropolyurethane, and butyl acetate is 20 g: 4 g: 20 mL.

[0013] Further limitation: In (2), the spraying parameters are as follows: the gun nozzle diameter is 1.5 mm, the spraying atmosphere is 0.3 mpa high-purity nitrogen, the distance between the gun and the substrate does not exceed 25 cm, the spraying fan surface is at 90° to the surface. After one spraying, rotate the substrate 90° for the next spraying. After multiple sprayings to reach the target thickness, complete the spraying, and finally place it in an oven for drying.

[0014] Even further limitation: The drying temperature is 60 °C and the time is 3 h.

[0015] Further limitation: In (3), the mass-volume ratio of hydrophobic silica, fluoropolyurethane, and butyl acetate is 0.2 g: 0.1 g: 20 mL.

[0016] Further limitation: In (3), the particle size of the hydrophobic silica is 15 nm.

[0017] Further limitation: In (2), the substrate is a 40×40 mm aluminum substrate.

[0018] The second object of the present invention is to provide a charged lunar dust protection thermal control coating prepared by the above method.

[0019] The third object of the present invention is to provide an application of the above charged lunar dust protection thermal control coating, specifically for lunar dust protection on the surface of a spacecraft.

[0020] Beneficial effects:

[0021] The present invention first realizes the conductivity of the thermal control coating by doping conductive particles, and then constructs a microstructure with appropriate size on the surface of the thermal control coating by using fluoropolyurethane with low surface energy as the binder and filler particles of nano-silica, and modifies the surface of the coating by using fluoropolyurethane with low surface energy to obtain a lunar dust protection thermal control coating. The present invention uses fluoropolyurethane as the binder and nano-silica as the filler, and can prepare a lunar dust protection thermal control coating by spraying method, avoiding the multi-step complex process of surface modification and being easy to be applied in large areas. Moreover, the filler particles of nano-silica construct the microstructure required for lunar dust protection on the surface of the thermal control coating, reducing the van der Waals force between the coating and lunar dust, and the thermal control coating after spraying still has good volume resistivity, reducing electrostatic adhesion and realizing the protection of charged lunar dust. At the same time, both nano-SiO2 and fluoropolyurethane have good spatial stability and can adapt to the extreme lunar surface environment. Description of the Drawings

[0022] Figure 1 SEM photos (at different magnifications) of the coating prepared in Comparative Example 1;

[0023] Figure 2 SEM photos (at different magnifications) of the coating prepared in Example 1;

[0024] Figure 3 Reflection spectra of the coatings prepared in Example 1 and Comparative Example 1;

[0025] Figure 4 Emission spectra of the coatings prepared in Example 1 and Comparative Example 1;

[0026] Figure 5 Comparison chart of the volume resistivity of the coatings prepared in Example 1 and Comparative Example 1;

[0027] Figure 6 Dust removal angle chart of the coatings prepared in Example 1 and Comparative Example 1;

[0028] Figure 7 TEM photo and EDS element distribution map of AZO@ZrO2 powder. Detailed Description of the Invention

[0029] To make the above objects, features and advantages of the present invention more obvious and understandable, the following describes the specific embodiments of the present invention in detail in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] Secondly, the so-called "one embodiment" or "embodiment" herein refers to specific features, structures or characteristics that may be included in at least one implementation manner of the present invention. The "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or selectively mutually exclusive embodiment with other embodiments.

[0032] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in this field and can be obtained by those skilled in the art through commercial channels without special instructions.

[0033] Example 1:

[0034] (1) Preparation of AZO@ZrO2 powder:

[0035] Place 15 g of ZrO2 powder with a particle size of 200 nm in the deposition chamber of an atomic layer deposition instrument. Set the pressure in the deposition chamber to 0.15 torr, the temperature in the deposition chamber to 140 °C, the rotation speed of the drum-type deposition chamber to 600 r / min, the zinc-aluminum atomic ratio during deposition to 23:1, the spraying source time to 60 s, and repeat 48 atomic layer deposition growth cycles to coat AZO on the surface of the ZrO2 powder to obtain AZO@ZrO2 powder.

[0036] (2) Substrate pretreatment:

[0037] Ultrasonically clean a 40×40 mm aluminum substrate with anhydrous ethanol, acetone, and anhydrous ethanol in sequence for 15 min, and dry it in an oven for standby.

[0038] (3) Preparation of AZO@ZrO2 thermal control slurry:

[0039] Dissolve 4 g of fluoropolyurethane in 20 mL of butyl acetate solution, add 20 g of AZO@ZrO2 powder to the solution, and stir with a magnetic stirrer for 2 h to disperse evenly to obtain AZO@ZrO2 thermal control slurry.

[0040] (4) Preparation of antistatic thermal control coating:

[0041] Using a spraying device, a spray gun with a 1.5 mm caliber is used for spraying under high-purity nitrogen with a pressure of 0.3 mpa. During spraying, the AZO@ZrO2 thermal control slurry is injected into the pigment cup. The substrate treated in (2) is placed on the spraying table. Hold the spray gun, keep the distance from the sample piece no more than 25 cm, press the spray gun switch. After stabilization, move uniformly parallel to the spraying surface, keep the spraying fan surface at 90° to the surface. During the spraying process, the cross-cross spraying method is adopted. After the sample piece is sprayed once, it is rotated 90° to complete the second spraying to ensure the uniformity of spraying. After the first spraying is completed, the substrate is placed in an oven at 60 °C for constant-temperature drying for 3 h, and then the next spraying is carried out. After multiple sprayings reach a thickness of 175 μm, stop spraying. After spraying is completed, the sample piece is taken off and placed in an oven at 60 °C for constant-temperature drying for 3 h to obtain a substrate with an anti-static AZO@ZrO2 thermal control coating.

[0042] (5) Preparation of SiO2 hydrophobic and dust-proof slurry:

[0043] Dissolve 0.1 g of fluoropolyurethane in 20 mL of butyl acetate solution, add 0.2 g of 15 nm hydrophobic silica to the solution, and stir with a magnetic stirrer for 2 h to disperse evenly to obtain SiO2 hydrophobic and dust-proof slurry.

[0044] (6) Preparation of charged lunar dust protection thermal control coating:

[0045] Using the same spraying method as in (4), spray the SiO2 hydrophobic and dust-proof slurry on the surface of the thermal control coating to adjust the microstructure, and the spraying thickness is 1 μm to prepare a charged lunar dust protection thermal control coating.

[0046] Comparative Example 1:

[0047] (1) Preparation of AZO@ZrO2 powder:

[0048] Place 15 g of ZrO2 powder with a particle size of 200 nm in the deposition chamber of the atomic layer deposition instrument. Set the pressure in the deposition chamber to 0.15 torr, set the temperature in the deposition chamber to 140 °C, the rotation speed of the drum-type deposition chamber is 600 r / min, the zinc-aluminum atomic ratio during deposition is 23:1, the spray source time is 60 s, and repeat 48 atomic layer deposition growth cycles to coat AZO on the surface of the ZrO2 powder to obtain AZO@ZrO2 powder.

[0049] (2) Substrate pretreatment:

[0050] Ultrasonically clean a 40×40 mm aluminum substrate with anhydrous ethanol, acetone, and anhydrous ethanol for 15 min in sequence, and dry it in an oven for standby.

[0051] (3) Preparation of AZO@ZrO2 thermal control slurry:

[0052] Dissolve 4 g of fluoropolyurethane in 20 mL of butyl acetate solution. Add 20 g of AZO@ZrO2 powder to the solution and stir it evenly for 2 h with a magnetic stirrer to obtain AZO@ZrO2 thermal control slurry.

[0053] (4) Preparation of antistatic thermal control coating

[0054] Using a spraying device and a spray gun with a 1.5 mm diameter, spray under high-purity nitrogen at a pressure of 0.3 mpa. During spraying, inject the AZO@ZrO2 thermal control slurry into the pigment cup. Place the substrate treated in (2) on the spraying table, hold the spray gun, keep the distance from the sample piece no more than 25 cm, press the spray gun switch, and move uniformly parallel to the spraying surface after stabilization, keeping the spray fan at 90° to the surface. During spraying, use the cross-cross spraying method. After the sample piece is sprayed once, rotate it 90° to complete the second spraying to ensure the uniformity of spraying. After the first spraying is completed, place the substrate in an oven at 60 °C for constant-temperature drying for 3 h, and then perform the next spraying. After multiple sprayings reach a thickness of 175 μm, stop spraying. After spraying is completed, remove the sample piece and place it in an oven at 60 °C for constant-temperature drying for 3 h to obtain an antistatic AZO@ZrO2 thermal control coating.

[0055] Comparative Example 2:

[0056] The difference between this comparative example and Example 1 is that: use ZrO2 powder to replace the AZO@ZrO2 powder in (3), and the rest of the process steps and parameter settings are the same as those in Example 1.

[0057] Effect example:

[0058] (1) Figure 7 Figure 1 is the TEM image and EDS element distribution map of the AZO@ZrO2 powder prepared in Example 1. Figure 1 It can be seen that AZO can completely coat zirconia and form an AZO@ZrO2 core-shell structure. At this time, the thickness of the AZO shell is about 5.3 nm. And according to the EDS element distribution results, it can be seen that the AZO@ZrO2 powder contains four elements: Zr, O, Zn, and Al, and the distribution of Zn and Al is uniform, indicating that the AZO conductive layer has been successfully deposited on the surface of ZrO2 particles uniformly by ALD.

[0059] (2) Figure 1 and Figure 2SEM images of the antistatic AZO@ZrO2 thermal control coating prepared in Comparative Example 1 and the charged lunar dust protection thermal control coating prepared in Example 1 at different magnifications. As can be seen from the figure, the surface of the antistatic AZO@ZrO2 thermal control coating presents micron-sized pores and protruding microstructures. The pores and protrusions of this micron structure easily cause lunar dust particles to get stuck in the pores, resulting in lunar dust adhesion, which is not conducive to dust prevention of the thermal control coating. However, the micron-sized pores and protrusions on the surface of the charged lunar dust protection thermal control coating prepared in Example 1 are smoothed, effectively avoiding lunar dust adhesion caused by lunar dust particles getting stuck in the pores. It can be observed under a high-magnification scanning electron microscope that the original submicron-sized protrusions on the surface of the thermal control coating completely disappear, replaced by a dense nano-structure. These nano-sized protrusions enable the contact area to be significantly reduced when the coating contacts lunar dust, effectively reducing the van der Waals force.

[0060] (3) Using an ultraviolet-visible-near-infrared spectrometer and a Fourier transform infrared spectrometer to compare the absorption rate in the 200 - 2500 nm band and the emissivity in the 2 - 16 μm band of the antistatic AZO@ZrO2 thermal control coating prepared in Comparative Example 1 and the charged lunar dust protection thermal control coating prepared in Example 1 to verify the influence of the hydrophobic dust-proof layer on the thermal control performance of the coating. The results are as Figure 3 and Figure 4 shown. As can be seen from the figure, in the 200 - 2500 nm band, the absorption rate of Experimental Example 1 is 0.125, and the absorption rate of Comparative Example 2 is 0.123, indicating that the absorption rate does not change much after spraying the hydrophobic dust-proof layer on the surface of the antistatic AZO@ZrO2 thermal control coating, and still maintains good reflection performance in the near-ultraviolet and far-infrared bands.

[0061] For the analysis of the emission performance, in the 2 - 16 μm band, the emissivity of Experimental Example 1 is 0.923, and the emissivity of Comparative Example 1 is 0.919, indicating that the emissivity does not change much after spraying the hydrophobic dust-proof layer on the surface of the antistatic AZO@ZrO2 thermal control coating.

[0062] In summary, it can be seen that after hydrophobic dust-proof modification of the AZO@ZrO2 thermal control coating, there is no obvious change in the thermal control performance of the coating.

[0063] (4) Using a high-resistance micro-current tester to measure the volume resistivity of the coating. The volume resistivity of Experimental Example 1 is 4.5×10 6 Ω·m, and the volume resistivity of Comparative Example 1 is 3.5×10 6 Ω·m. After constructing the surface microstructure using nano-silica, the volume resistivity does not decrease significantly and still meets the volume resistivity standard of the international antistatic thermal control coating. The resistivity of Comparative Example 2 is 9.2×10 12Ω·m, which indicates that after the powder is modified with AZO coating, the volume resistivity of the coating decreases significantly, and the modified coating meets the volume resistivity standard of the international antistatic thermal control coating.

[0064] (5) The dust-proof performance of the antistatic AZO@ZrO2 thermal control coating prepared in Comparative Example 1 and the charged lunar dust protection thermal control coating prepared in Example 1 was tested using lunar dust. The coating was placed horizontally, and a static powder spraying machine was used to spray charged lunar dust and spread it evenly on the surface of the coating. The sample was slowly tilted, and the natural sliding of the charged lunar dust was achieved under the action of gravity. The tilt angle of the lunar dust sliding was recorded. The test results are as Figure 6 shown. It can be Figure 6 seen that the average dust removal angle of the coating prepared in Experimental Example 1 is 52°, while the average dust removal angle of the coating prepared in Comparative Example 1 for charged lunar dust is 65°, indicating that after antistatic modification, the protection ability of the coating surface against charged lunar dust has been significantly improved.

[0065] The above are only the preferred embodiments of the present invention. In view of the fact that those skilled in the art to which the present invention pertains can make appropriate changes and modifications to the above-mentioned implementation manners, the present invention is not limited to the specific implementation manners described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A rapid preparation method for a charged lunar dust protection thermal control structure suitable for large-area applications, characterized in that, Including: (1) Coating AZO on the surface of ZrO2 by atomic layer deposition technology to obtain AZO@ZrO2 powder; (2) Mixing the AZO@ZrO2 powder, fluorinated polyurethane and butyl acetate evenly to obtain AZO@ZrO2 thermal control slurry, and spraying the AZO@ZrO2 thermal control slurry on the surface of the substrate by spraying method to obtain an antistatic AZO@ZrO2 thermal control coating; (3) Mixing hydrophobic silica, fluorinated polyurethane and butyl acetate evenly to obtain SiO2 hydrophobic and dust-proof slurry, and spraying the SiO2 hydrophobic and dust-proof slurry on the surface of the antistatic AZO@ZrO2 thermal control coating by the same spraying method as in (2) to obtain a charged lunar dust protection thermal control coating.

2. The preparation method according to claim 1, characterized in that, (1) The operation process is as follows: placing 200-nanometer-sized ZrO2 powder in the deposition chamber of the atomic layer deposition instrument, setting the deposition pressure to 0.15 torr, the temperature to 140 °C, the rotation speed of the drum-type deposition chamber to 600 r / min, the atomic ratio of zinc source to aluminum source to 23:1, the spraying source time for each deposition growth cycle to 60 s, and repeating 48 cycles.

3. The preparation method according to claim 1, wherein (2) The mass-volume ratio of AZO@ZrO2 powder, fluorinated polyurethane and butyl acetate is 20 g: 4 g: 20 mL.

4. The preparation method according to claim 1, characterized in that, (2) The spraying parameters are as follows: the gun nozzle diameter is 1.5 mm, the spraying atmosphere is 0.3 mpa high-purity nitrogen, the distance between the gun and the substrate does not exceed 25 cm, the spraying fan surface is at 90° to the surface. After one spraying, rotate the substrate 90° for the next spraying. After multiple sprayings reach the target thickness, the spraying is completed, and finally it is placed in an oven for drying.

5. The preparation method according to claim 4, characterized in that, The drying temperature is 60 °C and the time is 3 h.

6. The preparation method according to claim 1, characterized in that, (3) The mass-volume ratio of hydrophobic silica, fluorinated polyurethane and butyl acetate is 0.2 g: 0.1 g: 20 mL.

7. The preparation method according to claim 1, wherein (3) The particle size of the hydrophobic silica is 15 nm.

8. The preparation method according to claim 1, characterized in that (2) The substrate is a 40×40 mm aluminum substrate.

9. A charged protection thermal control coating prepared by the method according to any one of claims 1 to 8.

10. The application of the charged protection thermal control coating according to claim 9, characterized in that, For lunar dust protection on the surface of spacecraft.

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