Preparation method of micro-nano hierarchical super-hydrophobic coating

Abstract

The application belongs to the field of super-wetting material manufacturing, and discloses a preparation method of micro-nano hierarchical super-hydrophobic coating. The coating comprises a hydrophobic nanoparticle solution and a microstructure construction solution. The hydrophobic nanoparticle solution comprises ethanol, water, 25wt.% concentrated ammonia, tetraethyl silicate and hexadecyl trimethoxysilane, and the volume ratio is 18-22:1-2:1.8-3.3:0.8-2.0:0.3-0.7. The microstructure construction solution comprises dichloromethane, polydimethylsiloxane, polystyrene and a curing agent, and the mass ratio is 20-30:1.8-3.0:0.5-0.8:0.18-0.3. The application adopts a solvent evaporation phase separation method to construct the microstructure. The preparation and modification process of the nanoparticle solution is carried out in series in a single reaction container. Alkyl siloxane is used instead of highly toxic perfluorosiloxane. The method has a simple manufacturing process, low cost and is suitable for large-area spraying applications.

Description

Technical Field

[0001] The invention belongs to the field of super-wetting material production and relates to a method for preparing a micro-nano graded super-hydrophobic coating. Technical Background

[0002] Superhydrophobic coatings possess excellent self-cleaning, antifouling, water-repellent, anti-icing, and drag-reducing properties, and have broad application prospects in biomedicine, environmental remediation, industrial protection, and national defense. However, poor durability and high production costs are major factors hindering the widespread application of superhydrophobic coatings in various fields. Constructing distinct and robust micro- and nanostructures is an important strategy for improving the surface durability of superhydrophobic materials. The presence of microstructures provides mechanical strength to the surface and protects the nanostructures during mechanical wear, thereby improving the mechanical strength and durability of superhydrophobic surfaces.

[0003] 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, 2023, 471) reports a method for preparing a micro-nano graded super-hydrophobic material by adding micro-nano particles using a one-step spraying method. The disadvantage of this method is that the silicon dioxide micro-nano particles used are difficult to disperse evenly, a portion of the particles are covered by the coating, and the utilization rate is low. The modifier of silicon dioxide is a fluorine-containing organic compound, which can cause certain harm to the environment. Patent document CN110653493B reports a method for preparing a micro-nano multi-stage super-hydrophobic material 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] To reduce coating production costs, increase nanoparticle utilization, minimize environmental hazards, and expand its application, the present invention utilizes the principle of solvent evaporation phase separation to create a uniformly distributed micron structure through a spray coating method. The nanoparticle solution preparation and modification processes are performed in series within a single reaction vessel. Alkylsiloxane (HDTMS) is used as the hydrophobic modifier instead of perfluorosiloxane, and a secondary cold spraying method is employed, thereby increasing nanoparticle utilization and ensuring the mechanical stability of the coating. Summary of the Invention

[0005] The purpose of the present invention is to provide a formula and preparation method of a multi-level super-hydrophobic coating with low cost, low toxicity, uniform mixing and certain mechanical stability, in order to address the shortcomings of the prior art in preparing graded super-hydrophobic surfaces, such as high cost, difficulty in uniformly dispersing particles and harm to the environment.

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

[0007] A micro-nano graded super-hydrophobic coating is prepared. The multi-level hydrophobic surface uses the principle of solvent evaporation phase separation and the rapid volatilization of dichloromethane. After being sprayed onto a substrate, PS immediately precipitates as a solid, while PDMS remains a liquid, thereby constructing a uniformly distributed micron structure. At the same time, the wettability of PDMS and a modified hydrophobic nano-silica solution is utilized to evenly embed nanoparticles on the PDMS.

[0008] A method for preparing a micro-nano graded super-hydrophobic coating comprises the following steps:

[0009] (1) Adoption The method is to prepare nano-silica; after anhydrous ethanol, water and ammonia water are stirred evenly, tetraethyl silicate (TEOS) is added dropwise, and the mixture is stirred and reacted for a certain period of time to prepare a silica seed suspension.

[0010] (2) Hexadecyltrimethoxysilane (HDTMS) was then added, and 25 wt.% ammonia was added dropwise a second time to further increase the rate of formation and modification of the nanosilica particles. The reaction was stirred and continued for a certain period of time to obtain a modified hydrophobic nanosilica solution. Because ammonia is easily volatile, the reaction vessel was sealed and the reaction temperature was room temperature.

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

[0012] (4) Use a spray gun to evenly spray the PS / PDMS mixture onto the substrate, and completely evaporate the dichloromethane.

[0013] (5) Using a spray gun, the modified hydrophobic nano-silica solution is sprayed onto the substrate sprayed with the PS / PDMS mixed solution prepared in step (4), and the nanoparticles are adhered to the surface of the microstructure by utilizing the wettability.

[0014] (6) The substrate prepared in step (5) is cured in a vacuum drying oven, then washed with ethanol, and dried again to obtain a super-hydrophobic coating with a distinct micro-nano hierarchical structure.

[0015] The volume ratio of anhydrous ethanol, water, 25wt.% ammonia water and tetraethyl silicate in step (1) 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 hours.

[0016] In step (2), the volume ratio of 25wt.% ammonia water added in step (1) to 25wt.% ammonia water is (1.0-1.8):(0.8-1.5), the volume ratio of hexadecyltrimethoxysilane (HDTMS) to tetraethyl silicate is (0.3-0.7):(0.8-2.0), and 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). Because polydimethylsiloxane will slowly cure at room temperature after adding the curing agent, generally, the PDMS and the curing agent are added after the PS is completely dissolved when preparing the microstructure solution.

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

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

[0020] In step (6), the curing temperature is 80-90℃, the curing time is 2-3 hours, the coating surface is washed with ethanol after curing, and then dried in a drying oven at 80-90℃ for 5-15 minutes.

[0021] The beneficial effects of the present application are as follows:

[0022] (1) The micro-nano hierarchical super-hydrophobic coating prepared by the present application is constructed by the principle of solvent evaporation phase separation, and the polystyrene sprayed on the surface is quickly precipitated due to the volatile nature of dichloromethane, while the PDMS remains in liquid form, thus constructing a uniform microstructure and solving the problem of uniform dispersion of micron oxide particles or graphene in the solution.

[0023] (2) The present invention prepares a micro-nano graded super hydrophobic coating. In the process of preparing a modified nano-silica suspension, by controlling the reaction rate and the order of material addition, the preparation and modification processes of silica particles are carried out in series in a single reaction vessel, which has good continuity and simplifies the preparation process.

[0024] (3) The present invention prepares a micro-nano graded super hydrophobic coating, which uses a secondary spraying method to embed the modified hydrophobic silica in PDMS, thereby reducing the wrapping of PDMS on nanoparticles and improving the utilization rate of nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The change of contact angle of Examples 1, 2, 3, 4 and 5 of the present invention before and after the sandpaper friction test.

[0026] Figure 2 The microstructure of the surface morphology of Example 1 of the present invention before the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0027] Figure 3 The microstructure of the surface morphology of Example 1 of the present invention after the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0028] Figure 4 The microstructure of the surface morphology of Example 2 of the present invention before the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0029] Figure 5 The microstructure of the surface morphology of Example 2 of the present invention after the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0030] Figure 6 This is the microstructure of the surface morphology of Example 4 of the present invention before the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0031] Figure 7 The microstructure of the surface morphology of Example 4 of the present invention after the sandpaper friction test at (a) 2000 times and (b) 20000 times magnification.

[0032] Figure 8 This is a diagram showing the water wetting effect of Examples 1, 2, and 4 of the present invention after 50 times of sandpaper friction. DETAILED DESCRIPTION

[0033] The following further illustrates the specific implementation mode i of the present invention in combination with the accompanying drawings and technical solutions.

[0034] The ethanol, tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), dichloromethane, and polystyrene (PS) used in the following examples were all analytical grade. The ammonia solution was 25% by weight. The polydimethylsiloxane (PDMS) and curing agent were Dow Corning-184. The aluminum plate used was aluminum alloy 1060 (99.6% purity), the glass plate was a glass slide, and the copper plate was red copper.

[0035] The low-cost, stable super-hydrophobic coating prepared in the embodiment was measured using a contact angle meter to measure the static contact angle and rolling angle of the coating to characterize the hydrophobicity of the coating: the surface microstructure was observed using a field emission scanning electron microscope JSM-7900; and its mechanical stability was tested using a sandpaper wear test. The specific operation was as follows: a 2cm*2cm sample was placed face down on 800-mesh sandpaper, a weight of 100g was placed on the back of the sample, and the sample was pushed at a constant speed of 10cm. The sample was rotated 90° and continued to move forward at a constant speed of 10cm. This was one wear cycle, and 50 cycles were repeated.

[0036] Example 1

[0037] Preparation of modified nano-silica suspension:

[0038] Anhydrous ethanol, water, and 25% ammonia water were added to the reaction vessel. After stirring in a sealed container for 10 minutes, tetraethyl silicate (TEOS) was added dropwise. The reaction was continued in a sealed container with stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water was added dropwise a second time to adjust the reaction rate. Hexadecyltrimethoxysilane (HDTMS) was added, and the silica particles were hydrophobically modified. The reaction was continued in a sealed container with stirring for 3 hours to obtain a hydrophobic nanoparticle suspension. Because ammonia water is easily volatile, the container was sealed except for the addition of the materials. The reaction temperature was room temperature. The amounts of anhydrous ethanol, water, and 25% ammonia water added for the first time were 18 ml: 1 ml: 1.5 ml; the amounts of tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and ammonia water added for the second time were 2.0 ml: 0.7 ml: 1 ml.

[0039] Preparation of microstructure building solution:

[0040] 0.5 g of polystyrene was added to 20 g of dichloromethane and stirred for 15 minutes to fully dissolve it. Then, 1.8 g of PDMS and 0.18 g of curing agent were added and stirred continuously to mix evenly.

[0041] Preparation of superhydrophobic coating with hierarchical structure:

[0042] In this example, a glass slide was used as the spray substrate. The cut slide was rinsed with ethanol and deionized water and then dried with a hair dryer. The microstructuring solution was sprayed at a rate of 0.15 ml / cm², a pressure of 0.4 MPa, and a spray distance of 25 cm. After spraying, the plate was placed in a fume hood for approximately 10 minutes to produce a roughened surface with microstructures.

[0043] After the dichloromethane evaporates, the rough surface is modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.15 ml / cm2, the spraying pressure is set to 0.2 MPa, and the spraying distance is 20 cm. After spraying, the sample is placed in a drying oven at 80 ° C for 2 hours. After curing, the coating surface is rinsed with ethanol and then dried in a drying oven at 80 ° C for 10 minutes to obtain a super-hydrophobic coating with a hierarchical structure. The average value of the initial static contact angle of the coating is greater than 155 ° by multiple measurements with a contact angle meter. After 50 sandpaper friction tests, the static contact angle is greater than 150 °, as shown in FIG. Figure 1 As shown in the figure, the samples before and after friction were magnified 2000 times and 20000 times by scanning electron microscopy. It was observed that although part of the micro-nano structure was destroyed after friction, nanoparticles could still be observed in the gaps of the micron structure. The existence of the micron structure provided protection for the nanoparticles, as shown in the figure. Figure 2 (a), (b) and Figure 3 (a) and (b) show that the coating still exhibits good hydrophobicity after friction, as shown in Figure 8 As shown in (a).

[0044] Example 2

[0045] Preparation of modified nano-silica suspension:

[0046] Anhydrous ethanol, water, and 25% ammonia water were added to a reaction vessel. After stirring in a sealed container for 10 minutes, tetraethyl silicate (TEOS) was added dropwise. The reaction was continued in a sealed container with stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water was added dropwise a second time to adjust the reaction rate. Hexadecyltrimethoxysilane (HDTMS) was added, and the silica particles were hydrophobically modified. The reaction was continued in a sealed container with stirring for 3 hours to obtain a hydrophobic nanoparticle suspension. Because ammonia water is easily volatile, the container was sealed except for the addition of the materials. The reaction temperature was room temperature. The amounts of anhydrous ethanol, water, and 25% ammonia water added initially were 18 ml: 2 ml: 0.8 ml; the amounts of tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and ammonia water added in the second addition were 1.0 ml: 0.3 ml: 1.6 ml.

[0047] Preparation of microstructure building solution:

[0048] 0.7 g of polystyrene was added to 25 g of dichloromethane and stirred for 15 minutes to fully dissolve it. Then, 2.5 g of PDMS and 0.25 g of curing agent were added and stirred continuously to mix evenly.

[0049] Preparation of superhydrophobic coating with hierarchical structure:

[0050] In this example, a glass slide was used as the spray substrate. The cut slide was rinsed with ethanol and deionized water and then dried with a hair dryer. The microstructuring solution was sprayed at a rate of 0.18 ml / cm², a pressure of 0.4 MPa, and a spray distance of 25 cm. After spraying, the plate was placed in a fume hood for approximately 10 minutes to produce a roughened surface with microstructures.

[0051] After the dichloromethane has evaporated, the rough surface is 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 to 0.2 MPa, and the spraying distance is 25 cm. After spraying, the sample is placed in a drying oven at 80 ° C for 2 hours. After curing, the coating surface is rinsed with ethanol and then dried in a drying oven at 80 ° C for 10 minutes to obtain a super-hydrophobic coating with a hierarchical structure. The hydrophobic properties of the plate are characterized. The average value of the multiple measurements using a contact angle meter shows that the initial static contact angle of the coating is greater than 155 °. After 50 sandpaper friction tests, the static contact angle is greater than 150 °. Figure 1 As shown in the figure, the samples before and after friction were magnified 2000 times and 20000 times by scanning electron microscopy. It was observed that although part of the micro-nano structure was destroyed after friction, nanoparticles could still be observed in the gaps of the micron structure. The existence of the micron structure provided protection for the nanoparticles, as shown in the figure. Figure 4 (a), (b) and Figure 5 (a) and (b) show that the coating still exhibits good hydrophobicity after friction, as shown in Figure 8 (b) shown.

[0052] Example 3

[0053] Preparation of modified nano-silica suspension:

[0054] Anhydrous ethanol, water, and 25% ammonia were added to a reaction vessel. After stirring in a sealed container for 10 minutes, tetraethyl silicate (TEOS) was added dropwise. The reaction was continued in a sealed container with stirring for 1.5 hours to prepare a silica seed suspension. A second 25 wt.% ammonia solution was then added to adjust the reaction rate. Hexadecyltrimethoxysilane (HDTMS) was then added, and the silica particles were hydrophobically modified. The reaction was continued in a sealed container with stirring for 2 hours to obtain a hydrophobic nanoparticle suspension. Because ammonia solution is easily volatile, the container was sealed except for the addition of the materials, and the reaction temperature was room temperature. The initial addition of anhydrous ethanol, water, and 25% ammonia solution was in the ratio of 18 ml:1 ml:1 ml; the second addition of tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and ammonia solution was in the ratio of 1.5 ml:0.6 ml:1.6 ml.

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

[0056] Preparation of superhydrophobic coating with hierarchical structure:

[0057] In this example, an aluminum plate was used as the spray substrate. A cut glass slide was rinsed with ethanol and deionized water and then dried with a hair dryer. The microstructuring solution was sprayed at a rate of 0.18 ml / cm², a pressure of 0.4 MPa, and a spray distance of 25 cm. After spraying, the plate was placed in a fume hood for 10 minutes to produce a roughened surface with microstructures.

[0058] After the dichloromethane has evaporated, the rough surface is modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.15 ml / cm2, the spraying pressure is set to 0.2 MPa, and the spraying distance is 25 cm. After spraying, the sample is placed in a drying oven at 90 ° C for 2 hours. After curing, the coating surface is rinsed with ethanol and then dried in a drying oven at 90 ° C for 10 minutes to obtain a super-hydrophobic coating with a hierarchical structure. The hydrophobic properties of the plate are characterized. The average value of the multiple measurements using a contact angle meter shows that the initial static contact angle of the coating is greater than 155 °. After 50 sandpaper friction tests, the static contact angle is greater than 150 °. Figure 1 shown.

[0059] Example 4

[0060] Preparation of modified nano-silica suspension:

[0061] Anhydrous ethanol, water, and 25% ammonia were added to a reaction vessel. After stirring in a sealed container for 10 minutes, tetraethyl silicate (TEOS) was added dropwise. The reaction was continued in a sealed container with stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia was added dropwise a second time to adjust the reaction rate. Hexadecyltrimethoxysilane (HDTMS) was added, and the silica particles were hydrophobically modified. The reaction was continued in a sealed container with stirring for 3 hours to obtain a hydrophobic nanoparticle suspension. Because ammonia is easily volatile, the container was sealed except for the addition of the materials. The reaction temperature was room temperature. The amounts of anhydrous ethanol, water, and 25% ammonia added in the initial step were 22 ml: 2 ml: 0.8 ml; the amounts of tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and ammonia added in the second step were 0.8 ml: 0.3 ml: 1.6 ml.

[0062] Preparation of microstructure building solution:

[0063] 0.8 g of polystyrene was added to 30 g of dichloromethane and stirred for 15 minutes to fully dissolve it. Subsequently, 3.0 g of PDMS and 0.3 g of curing agent were added and stirred continuously to mix evenly.

[0064] Preparation of superhydrophobic coating with hierarchical structure:

[0065] In this example, a glass slide was used as the spray substrate. The cut slide was rinsed with ethanol and deionized water and then dried with a hair dryer. The microstructuring solution was sprayed at a rate of 0.12 ml / cm², a pressure of 0.4 MPa, and a spray distance of 25 cm. After spraying, the plate was placed in a fume hood for approximately 10 minutes to produce a roughened surface with microstructures.

[0066] After the dichloromethane has evaporated, the rough surface is modified with a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.15 ml / cm2, the spraying pressure is set to 0.2 MPa, and the spraying distance is 25 cm. After spraying, the sample is placed in a drying oven at 80 ° C for 2 hours. After curing, the coating surface is rinsed with ethanol and then dried in a drying oven at 80 ° C for 10 minutes to obtain a super-hydrophobic coating with a hierarchical structure. The hydrophobic properties of the plate are characterized. The average value of the multiple measurements using a contact angle meter shows that the initial static contact angle of the coating is greater than 155 °. After 50 sandpaper friction tests, the static contact angle is greater than 150 °. Figure 1 As shown in the figure, the samples before and after friction were magnified 2000 times and 20000 times by scanning electron microscopy. It was observed that although part of the micro-nano structure was destroyed after friction, nanoparticles could still be observed in the gaps of the micron structure. The existence of the micron structure provided protection for the nanoparticles, as shown in the figure. Figure 6 (a), (b) and Figure 7(a) and (b) show that the coating still exhibits good hydrophobicity after friction, as shown in Figure 8 (c) shown.

[0067] Example 5

[0068] Preparation of modified nano-silica suspension:

[0069] Anhydrous ethanol, water, and 25% ammonia water were added to a reaction vessel. After stirring in a sealed container for 10 minutes, tetraethyl silicate (TEOS) was added dropwise. The reaction was continued in a sealed container with stirring for 2 hours to prepare a silica seed suspension. Subsequently, 25 wt.% ammonia water was added dropwise a second time to adjust the reaction rate. Hexadecyltrimethoxysilane (HDTMS) was added, and the silica particles were hydrophobically modified. The reaction was continued in a sealed container with stirring for 2 hours to obtain a hydrophobic nanoparticle suspension. Because ammonia water is easily volatile, the container was sealed except for the addition of the materials. The reaction temperature was room temperature. The amounts of anhydrous ethanol, water, and 25% ammonia water added initially were 22 ml: 2 ml: 0.8 ml; the amounts of tetraethyl silicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and ammonia water added in the second addition were 0.8 ml: 0.3 ml: 1.8 ml.

[0070] Preparation of microstructure building solution:

[0071] 0.8 g of polystyrene was added to 30 g of dichloromethane and stirred for 15 minutes to fully dissolve it. Subsequently, 3.0 g of PDMS and 0.3 g of curing agent were added and stirred continuously to mix evenly.

[0072] The preparation of the microstructure construction solution is the same as that in Example 4.

[0073] Preparation of superhydrophobic coating with hierarchical structure:

[0074] In this example, a copper sheet was used as the spray substrate. The cut copper sheet was rinsed with ethanol and deionized water and then dried with a hair dryer. The microstructuring solution was sprayed at a rate of 0.15 ml / cm², a pressure of 0.4 MPa, and a spray distance of 25 cm. After spraying, the sheet was placed in a fume hood for approximately 10 minutes to obtain a roughened surface with a microstructure.

[0075] After the dichloromethane volatilizes completely, the next step of modification is performed on the rough surface using a modified nano-silica suspension. The spraying amount of the modified nano-silica suspension is 0.12 ml / cm2, the spraying pressure is set to 0.2 Mpa, and the spraying distance is 25 cm. After spraying, the sample is placed in a drying oven for curing at 80°C for 2 h. After curing, the surface of the coating is rinsed with ethanol, and then dried in a drying oven at 80°C for 10 minutes to obtain a super-hydrophobic coating with a hierarchical structure. The initial static contact angle of the coating is greater than 155°, and the static contact angle is greater than 150° after 50 times of sandpaper rubbing experiments, as shown in FIG. 8. Figure 1 ​

Claims

1. A method for preparing a micro-nano graded super-hydrophobic coating, characterized in that, The following steps are involved: (1) Adoption The method is to prepare nano-silica; after anhydrous ethanol, water and ammonia water are evenly stirred, tetraethyl silicate is added dropwise, and the mixture is stirred and reacted for a certain period of time to prepare a silica seed suspension; (2) adding hexadecyltrimethoxysilane and adding ammonia water dropwise for a second time to increase the hydrophobic modification rate, and reacting the mixture under sealed stirring at room temperature for a certain period of time to obtain a modified hydrophobic nano-silica solution; (3) dissolving polydimethylsiloxane, polystyrene and curing agent in dichloromethane to form a PS / PDMS mixed solution; (4) Use a spray gun to evenly spray the PS / PDMS mixture onto the substrate, and completely evaporate the dichloromethane; (5) using a spray gun to spray the modified hydrophobic nano-silica solution onto the substrate sprayed with the PS / PDMS mixture prepared in step (4), and utilizing the wettability to make the nanoparticles adhere to the surface of the microstructure; (6) The substrate prepared in step (5) is cured in a vacuum drying oven, then washed with ethanol, and dried again to obtain a super-hydrophobic coating with a distinct micro-nano hierarchical structure.

2. The preparation method according to claim 1, characterized in that In step (1), the volume ratio of anhydrous ethanol, water, 25 wt.% ammonia water and tetraethyl silicate 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 hours.

3. The preparation method according to claim 1, characterized in that The volume ratio of 25 wt.% ammonia water in step (2) to 25 wt.% ammonia water in step (1) is (1.0-1.8): (0.8-1.5), and the volume ratio of hexadecyltrimethoxysilane to tetraethyl silicate is (0.3-0.7): (0.8-2.0). The reaction is stirred for 2-3 hours at room temperature.

4. The preparation method according to claim 1, characterized in that In step (3), the mass ratio of dichloromethane, polydimethylsiloxane, polystyrene and 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 to 0.18 ml.cm -2 ; Spraying pressure is 0.3~0.4Mpa; Spraying distance is 20~30cm; 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 ; Spraying pressure is 0.2~0.3Mpa; Spraying distance is 20~30cm.

7. The preparation method according to claim 1, characterized in that In step (6), the curing temperature is 80-90° C., and the curing time is 2-3 hours. After curing, the coating surface is rinsed with ethanol and then dried in a drying oven at 80-90° C. for 5-15 minutes.

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