Preparation method of micro-nano graded super-hydrophobic coating

Abstract

The invention belongs to the field of super-infiltration material manufacturing, and discloses a preparation method of a micro-nano graded super-hydrophobic coating. The coating comprises a hydrophobic nanoparticle solution and a microstructure construction solution, the hydrophobic nanoparticle solution is prepared from ethanol, water, 25wt% stronger ammonia water, tetraethyl silicate and hexadecyl trimethoxy silane according to the volume ratio of (18 to 22) to (1 to 2) to (1.8 to 3.3) to (0.8 to 2.0) to (0.3 to 0.7); the microstructure construction solution comprises dichloromethane, polydimethylsiloxane, polystyrene and a curing agent, and the mass ratio of the dichloromethane to the polydimethylsiloxane to the polystyrene to the curing agent is (20-30): (1.8-3.0): (0.5-0.8): (0.18-0.3). The micron structure is constructed by adopting a solvent evaporation phase separation method; the preparation and modification processes of the nanoparticle solution are carried out in series in a single reaction container; and alkyl siloxane is used for replacing perfluorosiloxane with relatively high toxicity. The method is simple in manufacturing process, low in cost and suitable for application of large-area spraying.

Description

Technical Field

[0001] The present invention belongs to the field of manufacturing superwetting materials and relates to a preparation method of a micro-nano hierarchical superhydrophobic coating. Technical Background

[0002] Superhydrophobic coatings have excellent properties such as self-cleaning, anti-fouling, water resistance, ice resistance, and drag reduction, and have broad application prospects in biomedicine, environmental governance, industrial protection, and national defense construction. However, poor durability and high production costs are the main factors restricting the wide application of superhydrophobic coatings in various fields. Constructing obvious and firm micro-nano structures is an important strategy to improve the durability of superhydrophobic material surfaces. The existence of microstructures can provide mechanical strength for the surface and protect the nanostructures during the process of mechanical loss, thereby improving the mechanical strength and durability of superhydrophobic surfaces.

[0003] The literature (Yamei Zhao, Pengyuan Zhang, Xiaoqi Gu, et al. Preparation of PVDF-PDMS-SiO2 multi-stage rough superhydrophobic coating with excellent anti-corrosion and drag reduction performance via one-step cold spraying[J]. Surface&Coatings Technology, 471) reported a method for preparing micro-nano hierarchical superhydrophobic materials by adding micro-nano particles using a one-step spraying method. The disadvantage of this method is that the silica micro-nano particles used are difficult to disperse evenly, and some particles are covered by the coating, resulting in low utilization rate. The modifier of silica is a fluorinated organic compound, which will cause certain harm to the environment. The patent document CN110653493B reported a method for preparing micro-nano multi-stage superhydrophobic materials using laser etching. The disadvantage of this method is that the cost of laser etching is high and there are requirements for the spraying substrate.

[0004] In order to reduce the production cost of the coating, improve the utilization rate of nano-particles, reduce the harm to the environment, and expand its application range. The present invention uses the principle of solvent evaporation-induced phase separation to construct a uniformly distributed micro-structure by spraying method. The preparation and modification process of the nano-particle solution are carried out in series in a single reaction vessel. The hydrophobic modifier is replaced by alkylsiloxane (HDTMS) instead of perfluorosiloxane, and the method of secondary cold spraying is adopted to improve the utilization rate of nano-particles and ensure the mechanical stability of the coating. Summary of the Invention

[0005] The object of the present invention is to provide a formulation for a multi-stage superhydrophobic coating and a preparation method thereof, which are low-cost, low-toxic, uniformly mixed, and have certain mechanical stability, aiming at the disadvantages of high cost, difficult uniform dispersion of particles, and environmental harm existing in the preparation of hierarchical superhydrophobic surfaces in the prior art.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows:

[0007] The preparation of a micro-nano hierarchical superhydrophobic coating. According to the principle of solvent evaporation-induced phase separation, by using the rapid evaporation of dichloromethane, when PS is sprayed onto the substrate, it immediately precipitates as a solid, while PDMS remains in a liquid state, thus constructing a uniformly distributed micron structure. At the same time, by using the wettability of PDMS and the modified hydrophobic nano-silica solution, nano-particles are uniformly embedded on PDMS.

[0008] A preparation method of a micro-nano hierarchical superhydrophobic coating, comprising the following steps:

[0009] (1) Prepare nano-silica by the method; after uniformly stirring absolute ethanol, water and ammonia water, dropwise add tetraethyl orthosilicate (TEOS), and stir and react for a certain period of time to prepare a silica seed suspension.

[0010] (2) Subsequently, add hexadecyltrimethoxysilane (HDTMS), and secondly dropwise add 25 wt.% ammonia water to further increase the generation and modification rate of nano-silica particles, and continue to stir and react for a certain period of time to obtain a modified hydrophobic nano-silica solution. Since ammonia water is easy to volatilize, the reaction vessel is a sealed container, and the reaction temperature is room temperature.

[0011] (3) Dissolve polydimethylsiloxane (PDMS), polystyrene (PS) and a curing agent in dichloromethane to form a PS / PDMS mixed solution.

[0012] (4) Use a spray gun to uniformly spray the PS / PDMS mixed solution onto the substrate, and dichloromethane completely evaporates.

[0013] (5) Use a spray gun to spray the modified hydrophobic nano-silica solution onto the substrate sprayed with the PS / PDMS mixed solution prepared in step (4), and make the nano-particles adhere to the surface of the micron structure by wettability.

[0014] (6) Cure the substrate prepared in step (5) in a vacuum drying oven, then wash it with ethanol and dry it again to obtain a superhydrophobic coating with an obvious micro-nano hierarchical structure.

[0015] In step (1), the volume ratio of absolute ethanol, water, 25 wt.% ammonia water, and tetraethyl orthosilicate is (18 - 22):(1 - 2):(0.8 - 1.5):(0.8 - 2.0), and the reaction is stirred at room temperature for 1.5 - 2 h.

[0016] In step (2), the volume ratio of 25 wt.% ammonia water added in step (2) to the amount of 25 wt.% ammonia water added in step (1) is (1.0 - 1.8):(0.8 - 1.5), and the volume ratio of hexadecyltrimethoxysilane (HDTMS) to tetraethyl orthosilicate is (0.3 - 0.7):(0.8 - 2.0). The reaction is stirred for 2 - 3 hours at room temperature.

[0017] In step (3), the mass ratio of dichloromethane, polydimethylsiloxane (PDMS), polystyrene (PS), and curing agent is (20 - 30):(1.8 - 3.0):(0.5 - 0.8):(0.18 - 0.3). Since polydimethylsiloxane will slowly cure at room temperature after adding the curing agent, when preparing the microstructure construction solution, PDMS and the curing agent are generally added after PS is completely dissolved.

[0018] In step (4), the substrate is a glass plate, aluminum sheet, wooden board, etc.; the spraying amount of the PS / PDMS mixture is 0.12 - 0.18 ml·cm -2 ; the spraying pressure is 0.3 - 0.4 Mpa; the spraying distance is 20 - 30 cm; the placement time in the fume hood is 10 minutes.

[0019] In step (5), the spraying amount of the modified hydrophobic nano - silica solution is 0.12 - 0.15 ml·cm -2 ; the spraying pressure is 0.2 - 0.3 Mpa; the spraying distance is 20 - 30 cm.

[0020] In step (6), the curing temperature is 80 - 90 °C, and the curing time is 2 - 3 hours. After curing, the surface of the coating is rinsed with ethanol, and then dried in an 80 - 90 °C drying oven for 5 - 15 minutes.

[0021] Advantages of the present invention:

[0022] (1) A micro - nano hierarchical super - hydrophobic coating prepared by the present invention, based on the principle of solvent - evaporation - induced phase separation, utilizes the property that dichloromethane is volatile, so that polystyrene sprayed on the surface first precipitates rapidly, and due to the property that PDMS remains liquid, a uniformly distributed micron - scale structure is constructed, solving the problem that micron - scale oxide particles or graphene are difficult to be uniformly dispersed in the solution.

[0023] (2) A micro-nano hierarchical superhydrophobic coating prepared by the present invention, during the process of preparing the modified nano-silica suspension, by controlling the reaction rate and the order of material addition, the preparation and modification processes of the silica particles are carried out in series in a single reaction vessel, having good continuity and simplifying the preparation process.

[0024] (3) A micro-nano hierarchical superhydrophobic coating prepared by the present invention, adopting the method of secondary spraying, embeds the modified hydrophobic silica in PDMS, reduces the encapsulation of PDMS on the nanoparticles, and improves the utilization rate of the nanoparticles. Description of the Drawings

[0025] Figure 1 Shows the changes in the contact angle before and after the sandpaper friction experiment for Examples 1, 2, 3, 4, and 5 of the present invention.

[0026] Figure 2 Shows the microscopic structures of the surface morphology of Example 1 of the present invention before the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0027] Figure 3 Shows the microscopic structures of the surface morphology of Example 1 of the present invention after the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0028] Figure 4 Shows the microscopic structures of the surface morphology of Example 2 of the present invention before the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0029] Figure 5 Shows the microscopic structures of the surface morphology of Example 2 of the present invention after the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0030] Figure 6 Shows the microscopic structures of the surface morphology of Example 4 of the present invention before the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0031] Figure 7 Shows the microscopic structures of the surface morphology of Example 4 of the present invention after the sandpaper friction experiment at magnifications of (a) 2000 times and (b) 20000 times.

[0032] Figure 8 Shows the water wetting effect diagrams of Examples 1, 2, and 4 of the present invention after 50 times of sandpaper friction. Detailed Embodiments

[0033] The following further describes the specific embodiments of the present invention in combination with the drawings and technical solutions.

[0034] The ethanol, tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), dichloromethane, and polystyrene (PS) used in the following examples are all of analytical grade. The ammonia water is ammonia water with a mass percentage concentration of 25%. The polydimethylsiloxane (PDMS) and the curing agent are Dow Corning - 184. The aluminum plate used is aluminum alloy 1060 (with a purity of 99.6%), the glass plate is a glass slide, and the copper plate is pure copper.

[0035] For the low - cost and stable super - hydrophobic coating prepared in the examples, a contact angle measuring instrument is used to measure the static contact angle and rolling angle of the coating to characterize the hydrophobic performance of the coating; a field - emission scanning electron microscope JSM - 7900 is used for observing the surface microstructure; a sandpaper abrasion experiment is used to test its mechanical stability. The specific operation is as follows: Place a 2 cm * 2 cm sample face - down on 800 - mesh sandpaper, place a 100 - g weight on the back of the sample, push it forward uniformly for 10 cm, rotate the sample 90°, and continue to move forward uniformly for 10 cm. This is one abrasion cycle, and repeat 50 cycles.

[0036] Example 1

[0037] Preparation of modified nano - silica suspension:

[0038] Add anhydrous ethanol, water, and 25% ammonia water to the reaction vessel, seal and stir for 10 minutes, then drop - add tetraethyl orthosilicate (TEOS), and continue to seal and stir - react for 2 hours to prepare a silica seed suspension. Subsequently, drop - add 25 wt.% ammonia water for the second time to adjust the reaction rate, add hexadecyltrimethoxysilane (HDTMS), and perform hydrophobic modification on the silica particles. Seal and stir - react for 3 hours to obtain a hydrophobic nanoparticle suspension. Since ammonia water is volatile, except when adding materials drop - by - drop, it is sealed at other times, and the reaction temperature is room temperature. The initial amounts of anhydrous ethanol, water, and 25% ammonia water added are 18 ml:1 ml:1.5 ml; the amounts of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and the second ammonia water added are 2.0 ml:0.7 ml:1 ml.

[0039] Preparation of microstructure construction solution:

[0040] Add 0.5 g of polystyrene to 20 g of dichloromethane and stir for 15 minutes to dissolve it fully. Then add 1.8 g of PDMS and 0.18 g of the curing agent, and continuously stir and mix evenly.

[0041] Preparation of super - hydrophobic coating with hierarchical structure:

[0042] In this example, a glass slide was used as the spraying substrate. After the cut slide was cleaned with ethanol and deionized water, it was dried using a hair dryer. The spraying amount of the microstructural construction solution was 0.15 ml / cm2, the spraying pressure was set at 0.4 Mpa, and the spraying distance was 25 cm. After spraying, the plate was placed in a fume hood for about 10 minutes to obtain a rough surface with a micron structure.

[0043] After the dichloromethane had evaporated, the rough surface was further modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension was 0.15 ml / cm2, the spraying pressure was set at 0.2 Mpa, and the spraying distance was 20 cm. After spraying, the sample was placed in an oven at 80 °C for curing for 2 h. After curing, the surface of the coating was rinsed with ethanol, and then dried in an 80 °C oven for 10 minutes to obtain a superhydrophobic coating with a hierarchical structure. By measuring the contact angle with a contact angle measuring instrument multiple times and taking the average value, the initial static contact angle of the coating was greater than 155°, and the static contact angle was greater than 150° after 50 sandpaper friction experiments, as Figure 1 shown; the samples before and after friction were magnified 2000 times and 20000 times by scanning electron microscopy. It was observed that although some micro-nano structures were damaged after friction, nano-particles could still be observed in the voids of the micron structure. The existence of the micron structure provided protection for the nano-particles, as Figure 2 (a), (b) and as Figure 3 (a), (b) shown. The coating still showed good hydrophobicity after friction, as Figure 8 (a) shown.

[0044] Example 2

[0045] Preparation of the modified nano-silica suspension:

[0046] Absolute ethanol, water and 25% ammonia water were added to the reaction vessel. After sealing and stirring for 10 minutes, tetraethyl orthosilicate (TEOS) was added dropwise, and the reaction was continued under sealed stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water was added dropwise for the second time to adjust the reaction rate, and hexadecyltrimethoxysilane (HDTMS) was added to hydrophobically modify the silica particles. The reaction was carried out under sealed stirring for 3 hours to obtain a hydrophobic nano-particle suspension. Since ammonia water is volatile, except for the addition of materials, the rest of the time was under sealed conditions, and the reaction temperature was room temperature. The initial amounts of absolute ethanol, water, and 25% ammonia water added were 18 ml:2 ml:0.8 ml; the amounts of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and the second ammonia water were 1.0 ml:0.3 ml:1.6 ml.

[0047] Preparation of the microstructural construction solution:

[0048] Add 0.7 g of polystyrene to 25 g of dichloromethane and stir for 15 minutes to dissolve it completely. Then add 2.5 g of PDMS and 0.25 g of curing agent, and continuously stir to mix evenly.

[0049] Preparation of superhydrophobic coating with hierarchical structure:

[0050] In this example, a glass slide was used as the spraying substrate. After cutting the slide, it was cleaned with ethanol and deionized water and then dried with a hair dryer. The spraying amount of the microstructural construction solution was 0.18 ml / cm2, the spraying pressure was set at 0.4 Mpa, and the spraying distance was 25 cm. After spraying, the plate was placed in a fume hood for about 10 minutes to obtain a rough surface with a micron structure.

[0051] After the dichloromethane had evaporated completely, the rough surface was further modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension was 0.12 ml / cm2, the spraying pressure was set at 0.2 Mpa, and the spraying distance was 25 cm. After spraying, the sample was placed in an oven at 80 °C for curing for 2 h. After curing, the surface of the coating was rinsed with ethanol and then dried in an oven at 80 °C for 10 minutes to obtain a superhydrophobic coating with a hierarchical structure. The hydrophobic performance of the plate was characterized. By measuring the contact angle with a contact angle measuring instrument multiple times and taking the average value, the initial static contact angle of the coating was greater than 155°, and the static contact angle was greater than 150° after 50 sandpaper friction experiments, as Figure 1 shown; the samples before and after friction were magnified 2000 times and 20000 times by scanning electron microscopy. It was observed that although some micro-nano structures were damaged after friction, nano-particles could still be observed in the voids of the micron structure. The existence of the micron structure provided protection for the nano-particles, as Figure 4 (a), (b) and as Figure 5 (a), (b) shown. The coating still showed good hydrophobicity after friction, as Figure 8 (b) shown.

[0052] Example 3

[0053] Preparation of modified nano-silica suspension:

[0054] Add anhydrous ethanol, water and 25% ammonia water into the reaction vessel. After sealing and stirring for 10 minutes, tetraethyl orthosilicate (TEOS) is added dropwise, and the reaction continues to be sealed and stirred for 1.5 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water is added dropwise for the second time to adjust the reaction rate, and hexadecyltrimethoxysilane (HDTMS) is added, and the silica particles are hydrophobically modified. The reaction is sealed and stirred for 2 hours to obtain a hydrophobic nanoparticle suspension. Since ammonia water is volatile, except for the addition of materials, the rest of the time is sealed, and the reaction temperature is room temperature. The dosages of anhydrous ethanol, water and 25% ammonia water added initially are 18 ml: 1 ml: 1 ml; the dosages of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS) and the ammonia water added for the second time are 1.5 ml: 0.6 ml: 1.6 ml.

[0055] The preparation of the microstructural construction solution is the same as that in Example 2.

[0056] Preparation of a superhydrophobic coating with a hierarchical structure:

[0057] In this example, an aluminum plate is used as the spraying substrate. After the cut glass slides are cleaned with ethanol and deionized water, they are dried with a hair dryer. The spraying amount of the microstructural construction solution is 0.18 ml / cm2, the spraying pressure is set at 0.4 Mpa, and the spraying distance is 25 cm. After spraying, the plate is placed in a fume hood for 10 minutes to obtain a rough surface with a micron structure.

[0058] After the dichloromethane has evaporated, the rough surface is further modified with the modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.15 ml / cm2, the spraying pressure is set at 0.2 Mpa, and the spraying distance is 25 cm. After spraying, the sample is placed in an oven at 90 °C for curing for 2 h. After curing, the surface of the coating is rinsed with ethanol, and then dried in an oven at 90 °C for 10 minutes to obtain a superhydrophobic coating with a hierarchical structure, and the hydrophobic performance of the plate is characterized. By measuring with a contact angle measuring instrument and taking the average value through multiple measurements, the initial static contact angle of the coating is greater than 155°, and the static contact angle is greater than 150° after 50 sandpaper friction experiments, as Figure 1 shown.

[0059] Example 4

[0060] Preparation of the modified nano-silica suspension:

[0061] Add absolute ethanol, water and 25% ammonia water into the reaction vessel. After sealing and stirring for 10 minutes, tetraethyl orthosilicate (TEOS) is added dropwise, and the reaction continues with sealing and stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water is added dropwise for the second time to adjust the reaction rate, and hexadecyltrimethoxysilane (HDTMS) is added to hydrophobically modify the silica particles. The reaction is carried out with sealing and stirring for 3 hours to obtain a suspension of hydrophobic nanoparticles. Since ammonia water is volatile, except for the addition of materials, it is sealed at other times, and the reaction temperature is room temperature. The initial amounts of absolute ethanol, water, and 25% ammonia water added are 22 ml: 2 ml: 0.8 ml; the amounts of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and the second ammonia water are 0.8 ml: 0.3 ml: 1.6 ml.

[0062] Preparation of the microstructure construction solution:

[0063] Add 0.8 g of polystyrene into 30 g of dichloromethane and stir for 15 minutes to fully dissolve it. Subsequently, add 3.0 g of PDMS and 0.3 g of curing agent, and continuously stir and mix evenly.

[0064] Preparation of the superhydrophobic coating with a hierarchical structure:

[0065] In this example, a glass slide is used as the spraying substrate. After the cut slide is cleaned with ethanol and deionized water, it is dried with a hair dryer. The spraying amount of the microstructure construction solution is 0.12 ml / cm2, the spraying pressure is set at 0.4 Mpa, and the spraying distance is 25 cm. After spraying, the plate is placed in a fume hood for about 10 minutes to obtain a rough surface with a micron structure.

[0066] After the dichloromethane has evaporated, the rough surface is further modified with the modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.15 ml / cm2, the spraying pressure is set at 0.2 Mpa, and the spraying distance is 25 cm. After spraying, the sample is placed in an oven at 80 °C for curing for 2 h. After curing, the surface of the coating is rinsed with ethanol, and then dried in an 80 °C oven for 10 minutes to obtain a superhydrophobic coating with a hierarchical structure, and the hydrophobic performance of the plate is characterized. By measuring the contact angle with a contact angle measuring instrument and averaging the values obtained from multiple measurements, the initial static contact angle of the coating is greater than 155°, and the static contact angle is greater than 150° after 50 sandpaper friction experiments, as Figure 1 shown; the samples before and after friction are magnified 2000 times and 20000 times by scanning electron microscopy, and it is observed that although some micro-nano structures are damaged after friction, nanoparticles can still be observed in the voids of the micron structure. The existence of the micron structure provides protection for the nanoparticles, as Figure 6 (a), (b) and as Figure 7(a) and (b) as shown. After friction, the coating can still exhibit good hydrophobicity, such as Figure 8 (c) as shown.

[0067] Example Five

[0068] Preparation of modified nano-silica suspension:

[0069] Add absolute ethanol, water and 25% ammonia water into the reaction vessel, seal and stir for 10 minutes, then dropwise add tetraethyl orthosilicate (TEOS), and continue to seal and stir the reaction for 2 hours to prepare a silica seed suspension. Subsequently, 25wt.% ammonia water was added dropwise for the second time to adjust the reaction rate, and hexadecyltrimethoxysilane (HDTMS) was added, and the silica particles were hydrophobically modified, and the reaction was sealed and stirred for 2 hours to obtain a hydrophobic nanoparticle suspension. Since ammonia water is easy to volatilize, except for adding materials dropwise, the rest of the time is sealed, and the reaction temperature is room temperature. The initial amounts of absolute ethanol, water, and 25% ammonia water added are 22 ml: 2 ml: 0.8 ml; the amounts of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and the second ammonia water are 0.8 ml: 0.3 ml: 1.8 ml.

[0070] Preparation of microstructure construction solution:

[0071] Add 0.8 g of polystyrene into 30 g of dichloromethane and stir for 15 minutes to dissolve it completely, then add 3.0 g of PDMS and 0.3 g of curing agent, and continuously stir and mix evenly.

[0072] The preparation of the microstructure construction solution is the same as in Example Four.

[0073] Preparation of superhydrophobic coating with hierarchical structure:

[0074] In this example, a copper sheet was used as the spraying substrate. After the cut copper sheet was cleaned with ethanol and deionized water, it was dried with a hair dryer. The spraying amount of the microstructure construction solution was 0.15 ml / cm2, the spraying pressure was set at 0.4 Mpa, and the spraying distance was 25 cm. After spraying, the plate was placed in a fume hood for about 10 minutes to obtain a rough surface with a micron structure.

[0075] After the dichloromethane has completely volatilized, the rough surface is further modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.12 ml / cm2, the spraying pressure is set at 0.2 Mpa, and the spraying distance is 25 cm. After spraying, the sample is placed in an oven at 80 °C for curing for 2 h. After curing, the surface of the coating is rinsed with ethanol, and then dried in an oven at 80 °C for 10 minutes to obtain a superhydrophobic coating with a hierarchical structure. By measuring the contact angle with a contact angle measuring instrument multiple times and taking the average value, the initial static contact angle of the coating is greater than 155°, and the static contact angle is greater than 150° after 50 sandpaper friction experiments, as Figure 1 shown.

Claims

1. A preparation method of a micro-nano hierarchical superhydrophobic coating, characterized in that, It includes the following steps: (1) Adopt method to prepare nano-silica; after stirring anhydrous ethanol, water and ammonia water evenly, dropwise add tetraethyl orthosilicate, and stir and react for a certain period of time to prepare a silica seed suspension; (2) Subsequently, cetyltrimethoxysilane is added, and ammonia water is dropwise added for the second time to increase the hydrophobic modification rate. Stir and react at room temperature with sealing for a certain period of time to obtain a modified hydrophobic nano-silica solution; (3) Dissolve polydimethylsiloxane, polystyrene and a curing agent in dichloromethane to form a PS / PDMS mixed solution; (4) Use a spray gun to evenly spray the PS / PDMS mixed solution on a substrate, and let the dichloromethane volatilize completely; (5) Use a spray gun to spray the modified hydrophobic nano-silica solution on the substrate sprayed with the PS / PDMS mixed solution prepared in step (4). Utilize the wettability to make the nanoparticles adhere to the surface of the micro-structure; (6) Cure the substrate prepared in step (5) in a vacuum drying oven, then wash it with ethanol and dry it again to obtain a super-hydrophobic coating with an obvious micro-nano hierarchical structure.

2. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of absolute ethanol, water, 25 wt.% ammonia water and tetraethyl orthosilicate is (18-22):(1-2):(0.8-1.5):(0.8-2.0), and stir and react at room temperature for 1.5-2 h.

3. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of 25 wt.% ammonia water added in step (2) to the amount of 25 wt.% ammonia water added in step (1) is (1.0-1.8):(0.8-1.5), and the volume ratio of cetyltrimethoxysilane to tetraethyl orthosilicate is (0.3-0.7):(0.8-2.0). Stir and react for 2-3 hours, and the reaction temperature is room temperature.

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of dichloromethane, polydimethylsiloxane, polystyrene and the curing agent is (20-30):(1.8-3.0):(0.5-0.8):(0.18-0.3).

5. The preparation method according to claim 1, characterized in that, In step (4), the substrate is a glass plate, an aluminum sheet, a wooden board, etc.; the spraying amount of the PS / PDMS mixture is 0.12 - 0.18 ml·cm -2 ; the spraying pressure is 0.3 - 0.4 Mpa; the spraying distance is 20 - 30 cm; the placement time in the fume hood is 10 minutes.

6. The preparation method according to claim 1, characterized in that, In step (5), the spraying amount of the modified hydrophobic nano-silica solution is 0.12 - 0.15 ml·cm -2 ; the spraying pressure is 0.2 - 0.3 Mpa; the spraying distance is 20 - 30 cm.

7. The preparation method according to claim 1, wherein In step (6), the curing temperature is 80-90 °C, cure for 2-3 hours. After curing, rinse the surface of the coating with ethanol, and then dry it in an 80-90 °C drying oven for 5-15 minutes.

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