Preparation method of sodium chloride etching micro-nano structure wear-resistant super-hydrophobic coating

Abstract

This invention belongs to the field of hydrophobic coating technology, specifically relating to a method for preparing a wear-resistant superhydrophobic coating with a sodium chloride-etched micro / nano structure. The method includes the following steps: pretreatment of the substrate, preparation of an organic carrier, preparation of inorganic coating slurry and sodium chloride slurry, screen printing and sintering of the inorganic coating, screen printing and sodium chloride etching, post-treatment to form a micro / nano structure, preparation of superhydrophobic capsules, immersion of the post-treated sample in a superhydrophobic emulsion, extraction, and drying. This invention uses sodium chloride melt etching instead of laser etching, eliminating the need for highly corrosive chemicals, making it environmentally friendly and cost-effective. It introduces a biomimetic honeycomb structure, ensuring pattern accuracy through slurry and process control. The resulting coating possesses both excellent superhydrophobic properties and wear resistance, achieving wear-resistant superhydrophobic functionality of an inorganic coating under simple conditions. It is suitable for baking equipment and other applications, meeting the requirements for easy surface cleaning and wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of hydrophobic coating technology, specifically relating to a method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures. Background Technology

[0002] In the baking industry, the surface coating performance of baking utensils (such as baking pans and molds) directly affects food preparation efficiency, finished product quality, and the lifespan of the utensils. These utensils need to withstand high baking temperatures of 150-250℃ for extended periods during daily use, and frequently come into contact with oils, syrups, and weakly acidic substances produced during dough fermentation. They also require quick cleaning after use, leaving no food residue, and the coating must possess a certain degree of abrasion resistance to withstand friction during cleaning. Therefore, "high temperature resistance, easy cleaning, safety and non-toxicity, and wear resistance and durability" have become the core technical requirements for the surface coating of baking utensils.

[0003] However, the traditional enamel coating widely used in the baking equipment industry, while meeting basic requirements for high temperature resistance and ease of cleaning, reveals three irreconcilable core contradictions in practical applications, severely restricting the upgrading of equipment performance and industry development: Firstly, there is a significant imbalance between safety performance and process compatibility. To improve adhesion and stability, some traditional enamel coatings incorporate lead compounds as fluxes, leading to a risk of lead migration from the finished coating. When utensils come into contact with hot food, lead may penetrate the body through the food, potentially harming the nervous and digestive systems with long-term exposure. Furthermore, such lead-containing enamels fail to meet the mandatory safety standard of "≤0.01 mg / dm² lead migration from food contact surfaces" in China's GB 4806.10-2016 standard for "Enamel Products for Food Contact Materials and Articles". To meet safety requirements, the industry has developed lead-free enamel formulas. However, the melting point of these lead-free systems is generally higher than 850℃, while the heat deformation temperature of commonly used base materials for baking utensils (such as Q235 steel plates) is 600-700℃. At the sintering temperature of lead-free enamel, the base material is prone to thermal expansion and deformation, which can lead to problems such as warping and reduced dimensional accuracy of the utensils. This not only affects the uniformity of heating during baking (such as excessively high local temperatures after the baking pan is deformed, which can easily cause food to burn), but also shortens the service life of the utensils.

[0004] Secondly, maintaining the non-stick properties while meeting food hygiene requirements is difficult. Conventional enamel coatings have high surface energy, with a water contact angle typically less than 80°, making them hydrophilic. During baking, oils, sugars, and proteins in the dough easily adhere to the coating surface, forming residues that are difficult to remove. Data shows that the oil residue rate of traditional enamelware generally exceeds 20% after use. Cleaning requires repeated scrubbing with steel wool and strong detergents, a process that is not only time-consuming and labor-intensive (especially in commercial baking settings, where frequent cleaning reduces production efficiency), but also scratches the enamel coating surface, damaging its original structure and leading to even more severe residue adhesion in subsequent uses, creating a vicious cycle of "cleaning-scratching-increased residue." Furthermore, long-term oil residue can oxidize and deteriorate at high temperatures, breeding bacteria and posing food safety hazards, failing to meet the modern baking industry's demand for "easy cleaning and low maintenance."

[0005] Third, the construction of micro- and nano-structures is challenging, hindering the upgrading of coating functions. To improve the non-stick and wear-resistant properties of enamel coatings, the industry generally adopts the technical approach of constructing micro- and nano-rough structures. This involves forming uniform micron- and nano-scale protrusions and depressions on the coating surface to reduce the surface contact area, achieving a superhydrophobic effect (water contact angle > 150°) and reducing residue adhesion. However, existing micro- and nano-structure fabrication technologies have significant drawbacks: while mainstream physical etching methods (such as laser etching) can achieve high-precision structure construction, their equipment investment costs are high, with the etching cost per piece of equipment increasing by more than 200% compared to traditional processes, making them unsuitable for large-scale production of low- to mid-range baking equipment; furthermore, the localized instantaneous high temperatures during laser etching can easily cause micro-cracks in the enamel coating, with a breakage rate exceeding 15%, which in turn reduces the coating's wear resistance and sealing performance. Other alternatives, such as sandblasting, are lower in cost but have poor etching precision, cannot form uniform and ordered micro-nano structures, and have unstable superhydrophobic effects. Traditional chemical etching methods rely on highly corrosive reagents such as hydrofluoric acid and nitric acid, which not only corrode the substrate of the equipment but also generate a large amount of toxic waste liquid, polluting the environment. At the same time, they pose a significant risk to the safety of operators and do not conform to the development trend of "green, environmentally friendly, safe and efficient" in modern manufacturing.

[0006] In summary, the shortcomings of traditional enamel coatings in terms of safety, performance durability, and structural preparation can no longer meet the current high-quality requirements of baking utensils for "safety, non-toxicity, long-lasting and easy cleaning, and wear resistance and durability." There is an urgent need to develop a new coating preparation technology to solve the above-mentioned industry pain points. Summary of the Invention

[0007] This invention aims to address the shortcomings of existing technologies (such as high cost and complex equipment of laser etching), and proposes a method for preparing wear-resistant superhydrophobic coatings of micro / nano structures etched with sodium chloride. This method, by using sodium chloride melt etching instead of laser etching, enables the preparation of biomimetic superhydrophobic coatings in a simpler and more economical way. It solves the problems of safety and performance imbalance, poor non-stick durability, and high cost and easy damage to coating integrity associated with traditional enamel coatings.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures includes the following steps: (1) Substrate pretreatment: Remove and clean the surface oxide layer of the substrate; (2) Preparation of organic carrier: Mixed solvent and thickener are magnetically stirred in an oil bath at 60-90℃ for 1-2 hours until the thickener is completely dissolved. Then, thixotropic agent, dispersant and antioxidant are added. Stirring is continued at 60-90℃ for 1-2 hours. After cooling to room temperature, the mixture is defoamed by a vacuum defoamer and finally transferred to a small centrifuge tube for later use. (3) Slurry preparation: Low melting point glass powder and the organic carrier obtained in step (2) are mixed in proportion, and inorganic coating slurry is prepared by high-speed vacuum degassing and homogenization and three-roll rolling. Low melting point glass powder, sieved sodium chloride and organic carrier in step (2) are mixed in proportion, and sodium chloride slurry is prepared by high-speed vacuum degassing and homogenization and three-roll rolling. (4) Screen printing and inorganic coating sintering: Screen printing is used to print the inorganic coating pattern on the substrate surface in step (1) of the inorganic coating slurry obtained in step (3), and then sintering is performed to form an inorganic coating. (5) Screen printing and sodium chloride etching: Screen printing is used to print biomimetic patterns on the surface of the inorganic coating described in step (4) using the sodium chloride slurry obtained in step (3). After drying, the slurry is placed in a muffle furnace for etching. (6) Post-processing: The sample after etching in step (5) is treated with deionized water to remove sodium chloride in order to form micro-nano structures; (7) Preparation and treatment of superhydrophobic capsules: The post-treated micro-nano structure sample is immersed in the superhydrophobic capsule, pulled out and dried.

[0009] Further, in step (1), sandpaper is used to polish the steel plate until there is no obvious oxide layer on the surface and the scratches are consistent. After polishing, anhydrous ethanol is used to clean the steel plate to remove the shavings and oil. The substrate is a steel plate, including one of carbon steel, stainless steel, aluminum steel and cast iron.

[0010] Further, in the organic carrier described in step (2), the mixed solvent comprises, by mass fraction, 45-50% terpineol, 20-25% diethylene glycol butyl ether acetate and 6-10% dibutyl phthalate; The thickener accounts for 3-6% by mass, and the thixotropic agent includes 2-4% hydrogenated castor oil and 2-4% polyamide wax; The dispersant accounts for 4-6% of the mass, and the antioxidant accounts for 3-6% of the mass.

[0011] Furthermore, in step (3), when the inorganic coating slurry is prepared, the low melting point glass powder is FD66 low melting point glass powder, a product of Anmi Micro-Nano New Materials Co., Ltd., with an initial melting temperature of 480℃; The inorganic coating slurry has a low melting point glass powder to organic carrier mass ratio of 3-4:0.8-1.2. The high-speed vacuum degassing and homogenization parameters are 1000-1200 r / min for 2-5 min, repeated three to five times. The rolling thickness of the three-roll mill is 15-25 micrometers.

[0012] Furthermore, in step (3), when the sodium chloride slurry is prepared, the sodium chloride powder is passed through 40 mesh, 100 mesh and 400 mesh sieves in sequence, and the particle size is controlled to be 38 micrometers or less; In the sodium chloride slurry, the mass ratio of glass powder:sodium chloride:organic carrier is a:b:c, where a ranges from 14 to 20, b ranges from 1 to 4, and c ranges from 14 to 18. The vacuum degassing and homogenization parameters are 1000-1200 r / min for 2-5 min, repeated three to five times, and the rolling thickness of the three-roll mill is 15-25 micrometers.

[0013] Furthermore, in step (4), the pattern of the first screen printing plate used in screen printing is a square pattern; In step (5), the pattern of the second screen printing plate used in screen printing is a honeycomb pattern; Both types of screen printing plates have a mesh count of 200-400, and the thickness of the paste layer after printing is 15-30 micrometers.

[0014] Further, in step (4), when the inorganic coating is sintered, the printed sample is first dried in an oven at 60-80℃ for 2-4 hours, and then placed in a muffle furnace for sintering: the heating rate is 5-10℃ / min, and the temperature is maintained at 300-400℃ for 30-60 minutes to remove the adhesive (remove the organic carrier so that the organic carrier in the slurry can fully volatilize), and the temperature is continued to rise at 5-10℃ / min to 600-700℃ and maintained for 15-25 minutes.

[0015] Further, in step (5), during sodium chloride etching, the sample after printing sodium chloride paste is first dried in an oven at 60-80℃ for 2-4 hours, and then placed in a muffle furnace for etching: the heating rate is 5-10℃ / min, and the sample is kept at 300-400℃ for 30-60 minutes to remove the adhesive (to remove the organic carrier and allow the organic carrier in the paste to fully volatilize), and then the temperature is increased to 550-700℃ at 5-10℃ / min and kept for 10-20 minutes.

[0016] Furthermore, in step (6), the sample is soaked in deionized water at 80-100℃ for 2-5 hours to remove residual sodium chloride after etching.

[0017] Further, in step (7), the preparation method of the superhydrophobic capsule includes the following steps: mixing PFTDS, Tween 80 and deionized water in a mass ratio of x:y:z, wherein x ranges from 8 to 10, y ranges from 0.5 to 1, and z ranges from 180 to 220, and then homogenizing at 5000-6000 r / min for 100-160 min to obtain an oil-in-water microemulsion; The oil-in-water microemulsion was then transferred to a magnetic stirrer and stirred for 80-100 minutes. During stirring, a pre-set amount of fumed alumina was slowly added first, and after it was completely dispersed in the microemulsion, fumed silica was slowly added next. The fumed alumina and fumed silica were prepared in a mass ratio of m:n, where m ranges from 5.5 to 6.5 and n ranges from 0.5 to 1.5, with a total mass of 10.0-15.0 g. The sample was immersed in the superhydrophobic capsule emulsion for 25-45 minutes, then lifted and dried in an oven at 100-120℃ for 12-16 hours.

[0018] Compared with the prior art, the present invention, employing the above technical solution, has the following beneficial effects: 1. The biomimetic micro-nano structure construction method provided by the present invention uses sodium chloride to etch inorganic coatings. It does not require the use of strong corrosive chemicals or laser etching, has low cost, is simple to implement, and has low harm to the environment and human body. It is a green, environmentally friendly and low-cost processing method.

[0019] 2. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures provided by the present invention incorporates biomimetic knowledge to design a screen printing stencil. The stencil pattern is hexagonal and honeycomb-shaped.

[0020] 3. The method for preparing a wear-resistant superhydrophobic coating with sodium chloride etched micro / nano structures provided by the present invention constructs micron-level structures by screen printing, and the accuracy of the pattern can be controlled by adjusting the composition and properties of the paste.

[0021] 4. The method for preparing a wear-resistant superhydrophobic coating for etching micro-nano structures with sodium chloride provided by the present invention utilizes the physical property of sodium chloride dissolving in water and the property of glass having a softening point. After etching the micro-structure with sodium chloride in the honeycomb structure, the sodium chloride in the micro-structure can be removed by deionized water.

[0022] 5. The method for preparing a wear-resistant superhydrophobic coating with a sodium chloride-etched micro / nano structure provided by the present invention can directly introduce micro / nano particles with superhydrophobic properties into the micron structure constructed by sodium chloride. The micron structure protects the micro / nano-level superhydrophobic particles, thus constructing a multi-level micro / nano structure. The micron structure constructed by sodium chloride can protect the superhydrophobic particles, and the superhydrophobic particles can provide superhydrophobic effects for the inorganic coating, so that the inorganic coating has both wear resistance and superhydrophobic properties.

[0023] 6. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures provided by the present invention has simple and easy superhydrophobic treatment steps and does not require other binders. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 It is the pattern design image of the first screen printing plate in Examples 1-3.

[0026] Figure 2 It is the biomimetic pattern design image of the second screen printing plate in Examples 1-3.

[0027] Figure 3 This is an optical photograph of the micro / nano structure constructed after etching the inorganic coating with sodium chloride in Example 1.

[0028] Figure 4 This is an optical photograph of the micro / nano structure constructed after etching the inorganic coating with sodium chloride in Example 2.

[0029] Figure 5 This is an optical photograph of the micro / nano structure constructed after etching the inorganic coating with sodium chloride in Example 3.

[0030] Figure 6 This is an optical image of the water contact angle on the sample surface after the micro / nano structure was treated with superhydrophobicity in Example 1.

[0031] Figure 7 This is an optical image of the water contact angle on the sample surface after superhydrophobic treatment of the micro / nano structure in Example 2.

[0032] Figure 8 This is an optical image of the water contact angle on the sample surface after the micro / nano structure was treated with superhydrophobicity in Example 3. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1 A method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures includes the following steps: (1) Substrate pretreatment: Prepare several 50mm×50mm Q235 steel plates, and use 80 grit, 200 grit and 600 grit sandpaper to polish the oxide layer in sequence until the surface is free of oxide layer and the scratches are consistent. After polishing, use anhydrous ethanol to clean the residual shavings and oil stains on the surface.

[0035] (2) Preparation of organic carrier: Weigh 25g terpineol, 11g diethylene glycol butyl ether acetate, 4g dibutyl phthalate (mixed solvent) and 2.5g ethyl cellulose (thickener) according to the proportion and put them into a beaker; place them in an oil bath magnetic stirrer and stir at 90°C for 1h until the thickener is completely dissolved. Then add 1.25g hydrogenated castor oil, 1.25g polyamide wax (thixotropic agent), 2.5g triethanolamine (dispersant), and 2.5g oxalic acid (antioxidant). Continue stirring at 90°C for 1h. After cooling to room temperature, remove bubbles under vacuum and transfer to a small centrifuge tube for later use.

[0036] (3) Slurry preparation: (3.1) Preparation of inorganic coating slurry: Add 9g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) and 3.3g of the organic carrier obtained in step (2) to a container. Use a vacuum degassing mixer to homogenize the slurry at a speed of 1200r / min for 2min under vacuum conditions. Repeat the above homogenization process three times. After the slurry is evenly mixed, use a three-roll mill to roll and disperse it to 25μm to obtain the inorganic coating slurry. (3.2) Preparation of sodium chloride slurry: After grinding the sodium chloride powder, it was sieved through 40 mesh, 100 mesh and 400 mesh screens in sequence. Then, 0.2g of sodium chloride and 1.8g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) were added to the mortar. After mixing, 1.6g of the organic carrier obtained in step (2) was added. The mixture was homogenized for 2min under vacuum conditions at a speed of 1200r / min using a vacuum degassing mixer. The homogenization process was repeated three times. After the mixture was homogenized, it was rolled and dispersed to 25μm using a three-roll mill to obtain sodium chloride slurry.

[0037] (4) Screen printing and inorganic coating sintering: Clean the steel surface with anhydrous ethanol, and place 1g of the inorganic coating paste obtained in step (3) on the first screen printing plate (e.g. Figure 1 As shown, the inorganic coating slurry was evenly scraped onto the Q235 steel plate using a rubber scraper to print the inorganic coating pattern. The sample was placed in an oven to remove the adhesive, and dried at 80℃ for 2 hours. The sample was then placed in a muffle furnace in an air atmosphere for inorganic coating sintering. First, the temperature was increased from room temperature to 350℃ at a rate of 5℃ / min and held at this temperature for 60 minutes. Then, the temperature was increased to 650℃ at a rate of 5℃ / min and held at this temperature for 20 minutes. The pattern of the first screen printing plate is a 50mm×50mm square with a mesh count of 200. (5) Screen printing and sodium chloride etching: Place 0.1g of the sodium chloride coating paste obtained in step (3) onto the second screen printing plate (e.g. Figure 2 As shown, a rubber squeegee was used to evenly spread the slurry onto the inorganic coating to print a biomimetic pattern. The sample was then placed in an oven to remove the adhesive, and dried at 80°C for 2 hours. The sample was then placed in a muffle furnace under an air atmosphere, and the inorganic coating was etched using sodium chloride. First, the temperature was increased from room temperature to 350°C at a rate of 5°C / min and held at this temperature for 60 minutes; then, the temperature was increased to 550°C at a rate of 5°C / min and held at this temperature for 15 minutes. The second screen printing plate has a honeycomb pattern, which is composed of an array of regular hexagonal patterns. The side length of each regular hexagon is 500μm, the spacing between each regular hexagon is 200μm, and the mesh size is 200. (6) Post-processing: Place the inorganic coated steel plate after etching in step (5) into 300mL of deionized water, heat the deionized water to 100℃, and keep it warm for 2h.

[0038] (7) Preparation of superhydrophobic capsules: In a beaker, add 5.0g PFTDS (hydrogen-containing silicone oil), 0.5g Tween 80 and 100.0g deionized water in sequence. Use a high-speed homogenizer to continuously homogenize and stir at a constant speed of 5000 r / min for 120min to ensure that the system is fully emulsified, and finally obtain a uniform and stable water-in-oil microemulsion.

[0039] Subsequently, the prepared oil-in-water microemulsion was transferred to a magnetic stirrer and stirred for 90 minutes. During the stirring process, a predetermined amount of fumed alumina was slowly added first, and after it was completely dispersed in the microemulsion, fumed silica was slowly added. The fumed alumina and fumed silica were prepared at a mass ratio of 6:1, and the total mass of the two was strictly controlled to be 12g.

[0040] (8) Superhydrophobic treatment: The sample obtained from the post-treatment in step (5) is immersed in the superhydrophobic capsule emulsion in step (7) for 30 minutes, until the superhydrophobic capsules are fully inserted into the etched micro / nano structure. Then, the sample is pulled out vertically. After the emulsion is evenly distributed on the sample surface, it is placed in an oven at 120°C for 12 hours. The optical photograph of the superhydrophobic coating is shown in [reference needed]. Figure 3 .

[0041] Example 2 A method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures includes the following steps: (1) Preparatory steps: Prepare several 50mm×50mm Q235 steel plates, and use 80 grit, 200 grit and 600 grit sandpaper to polish the oxide layer in turn until the surface is free of oxide layer and the scratches are consistent. After polishing, use anhydrous ethanol to clean the residual shavings and oil stains on the surface. Clean the screen printing stencil with anhydrous ethanol; (2) Preparation of organic carrier: Weigh 25g terpineol, 11g diethylene glycol butyl ether acetate, 4g dibutyl phthalate (mixed solvent) and 2.5g ethyl cellulose (thickener) according to the proportion and put them into a beaker; place them in an oil bath magnetic stirrer and stir at 90°C for 1h until the thickener is completely dissolved. Then add 1.25g hydrogenated castor oil, 1.25g polyamide wax (thixotropic agent), 2.5g triethanolamine (dispersant), and 2.5g oxalic acid (antioxidant). Continue stirring at 90°C for 1h. After cooling to room temperature, remove bubbles under vacuum and transfer to a small centrifuge tube for later use. (3) Slurry preparation: (3.1) Preparation of inorganic coating slurry: Add 9g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) and 3.3g of the organic carrier obtained in step (2) to a container. Use a vacuum degassing mixer to homogenize the slurry at a speed of 1200r / min for 2min under vacuum conditions. Repeat the above homogenization process three times. After the slurry is evenly mixed, use a three-roll mill to roll and disperse it to 25μm to obtain the inorganic coating slurry. (3.2) Preparation of sodium chloride slurry: After grinding the sodium chloride powder, it was sieved through 40 mesh, 100 mesh and 400 mesh screens in sequence. Then, 0.3g of sodium chloride and 1.7g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) were added to the mortar. After mixing, 1.6g of the organic carrier obtained in step (2) was added. The mixture was homogenized for 2min under vacuum conditions at a speed of 1200r / min using a vacuum degassing mixer. The homogenization process was repeated three times. After the mixture was homogenized, it was rolled and dispersed to 25μm using a three-roll mill to obtain sodium chloride slurry.

[0042] (4) Screen printing and inorganic coating sintering: Clean the steel surface with anhydrous ethanol, and place 1g of the inorganic coating paste obtained in step (3) on the first screen printing plate (e.g. Figure 1 As shown, the slurry was evenly scraped onto a Q235 steel plate using a rubber scraper to print an inorganic coating pattern. The sample was placed in an oven to remove the adhesive, and dried at 80℃ for 2 hours. The sample was then placed in a muffle furnace in an air atmosphere for inorganic coating sintering. First, the temperature was increased from room temperature to 350℃ at a rate of 5℃ / min and held at this temperature for 60 minutes. Then, the temperature was increased to 650℃ at a rate of 5℃ / min and held at this temperature for 20 minutes to obtain the inorganic coating. The pattern of the first screen printing plate is a 50mm×50mm square with a mesh count of 200. (5) Screen printing and sodium chloride etching: Place 0.1g of the sodium chloride paste obtained in step (3) onto the second screen printing plate (e.g. Figure 2 As shown, a biomimetic pattern was printed on the inorganic coating by uniformly applying sodium chloride slurry to the sample using a rubber squeegee. The sample was then placed in an oven to remove the adhesive and dried at 80°C for 2 hours. The sample was then placed in a muffle furnace with an air atmosphere and etched with sodium chloride. The temperature was first increased from room temperature to 350°C at a rate of 5°C / min and held at this temperature for 60 minutes. Subsequently, the temperature was increased to 600°C at a rate of 5°C / min and held at this temperature for 15 minutes.

[0043] The second screen printing plate has a honeycomb pattern, which is composed of an array of regular hexagonal patterns. The side length of each regular hexagon is 500μm, the spacing between each regular hexagon is 200μm, and the mesh size is 200. (6) Post-processing: Place the inorganic coated steel plate after etching in step (5) into 300mL of deionized water, heat the deionized water to 100℃, and keep it warm for 2h.

[0044] (7) Preparation of superhydrophobic capsules: In a beaker, add 5.0g PFTDS (containing hydrogen silicone oil), 0.5g Tween 80 and 100.0g deionized water in sequence. Use a high-speed homogenizer to continuously homogenize and stir at a constant speed of 5000 r / min for 120min to ensure that the system is fully emulsified and finally obtain a uniform and stable oil-in-water microemulsion. Subsequently, the prepared oil-in-water microemulsion was transferred to a magnetic stirrer and stirred for 90 minutes. During the stirring process, a predetermined amount of fumed alumina was slowly added first, and after it was completely dispersed in the microemulsion, fumed silica was slowly added. The fumed alumina and fumed silica were prepared at a mass ratio of 6:1, and the total mass of the two was strictly controlled to be 12g.

[0045] (8) Superhydrophobic treatment: The sample obtained after the post-treatment in step (5) is immersed in the superhydrophobic capsule emulsion prepared in step (7) for 30 minutes. After the superhydrophobic capsules are fully inserted into the etched micro-nano structure, the sample is then pulled out vertically. After the emulsion is evenly distributed on the sample surface, it is placed in an oven at 120°C for 12 hours. The optical photograph of the superhydrophobic coating is shown in [reference needed]. Figure 4 .

[0046] Example 3 A method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures includes the following steps: (1) Preparatory steps: Prepare several 50mm×50mm Q235 steel plates, and use 80 grit, 200 grit and 600 grit sandpaper to polish the oxide layer in turn until the surface is free of oxide layer and the scratches are consistent. After polishing, use anhydrous ethanol to clean the residual shavings and oil stains on the surface. Clean the screen printing stencil with anhydrous ethanol; (2) Preparation of organic carrier: Weigh 25g terpineol, 11g diethylene glycol butyl ether acetate, 4g dibutyl phthalate (mixed solvent), and 2.5g ethyl cellulose (thickener) according to the proportion and put them into a beaker; place them in an oil bath magnetic stirrer and stir at 90°C for 1h until the thickener is completely dissolved. Then add 1.25g hydrogenated castor oil, 1.25g polyamide wax (thixotropic agent), 2.5g triethanolamine (dispersant), and 2.5g oxalic acid (antioxidant). Continue stirring at 90°C for 1h. After cooling to room temperature, remove bubbles under vacuum and transfer to a small centrifuge tube for later use.

[0047] (3) Slurry preparation: (3.1) Preparation of inorganic coating slurry: Add 9g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) and 3.3g of the organic carrier obtained in step (2) to a container. Use a vacuum degassing mixer to homogenize the slurry at a speed of 1200r / min for 2min under vacuum conditions. Repeat the above homogenization process three times. After the slurry is evenly mixed, use a three-roll mill to roll and disperse it to a particle size of 25μm to obtain the inorganic coating slurry. (3.2) Preparation of sodium chloride slurry: After grinding the sodium chloride powder, it was sieved through 40 mesh, 100 mesh and 400 mesh screens in sequence. Then, 0.4g of sodium chloride and 1.6g of glass powder (FD66 low melting point glass powder from Anmi Micro-Nano New Materials Co., Ltd. with an initial melting temperature of 480℃) were added to the mortar. After mixing, 1.6g of the organic carrier obtained in step (2) was added. The mixture was homogenized for 2min under vacuum conditions at a speed of 1200r / min using a vacuum degassing mixer. The homogenization process was repeated three times. After the mixture was homogenized, it was rolled and dispersed to 25μm using a three-roll mill to obtain sodium chloride slurry.

[0048] (4) Screen printing and inorganic coating sintering: Clean the steel surface with anhydrous ethanol, and place 1g of inorganic coating paste on the first screen printing plate (e.g., Figure 1 As shown, the inorganic coating slurry was evenly scraped onto the Q235 steel plate using a rubber scraper. The sample was placed in an oven to remove the adhesive, and dried at 80℃ for 2 hours. The sample was then placed in a muffle furnace in an air atmosphere for inorganic coating sintering. First, the temperature was increased from room temperature to 350℃ at a rate of 5℃ / min and held at this temperature for 60 minutes. Then, the temperature was increased to 650℃ at a rate of 5℃ / min and held at this temperature for 20 minutes to obtain the inorganic coating. The pattern of the first screen printing plate is a 50mm×50mm square with a mesh count of 200. (5) Screen printing and sodium chloride etching: Place 0.1g of the sodium chloride paste obtained in step (3) onto the second screen printing plate (e.g. Figure 2 As shown, a biomimetic pattern was printed on the inorganic coating by uniformly applying sodium chloride slurry to the sample using a rubber squeegee. The sample was then placed in an oven to remove the adhesive and dried at 80°C for 2 hours. The sample was then placed in a muffle furnace with an air atmosphere and etched with sodium chloride. The temperature was first increased from room temperature to 350°C at a rate of 5°C / min and held at this temperature for 60 minutes. Subsequently, the temperature was increased to 600°C at a rate of 5°C / min and held at this temperature for 15 minutes. The second screen printing plate has a honeycomb pattern, which is composed of an array of regular hexagonal patterns. The side length of each regular hexagon is 500μm, the spacing between each regular hexagon is 200μm, and the mesh size is 200. (6) Post-processing: Place the inorganic coated steel plate after etching in step (5) into 300mL of deionized water, heat the deionized water to 100℃, and keep it warm for 2h; (7) Preparation of superhydrophobic capsules: In a beaker, add 5.0g PFTDS (containing hydrogen silicone oil), 0.5g Tween 80 and 100.0g deionized water in sequence. Use a high-speed homogenizer to continuously homogenize and stir at a constant speed of 5000 r / min for 120min to ensure that the system is fully emulsified and finally obtain a uniform and stable oil-in-water microemulsion. Subsequently, the prepared oil-in-water microemulsion was transferred to a magnetic stirrer and stirred for 90 minutes. During the stirring process, a predetermined amount of fumed alumina was slowly added first, and after it was completely dispersed in the microemulsion, fumed silica was slowly added. The fumed alumina and fumed silica were prepared at a mass ratio of 6:1, and the total mass of the two was strictly controlled to be 12g.

[0049] (8) Superhydrophobic treatment: The post-treated sample was immersed in the superhydrophobic capsule emulsion prepared in step (6) for 30 minutes until the superhydrophobic capsules were fully inserted into the etched micro / nano structure. Then the sample was pulled out vertically. After the emulsion was evenly distributed on the sample surface, it was placed in an oven at 120°C for 12 hours. The optical photograph of the superhydrophobic coating is shown in [reference needed]. Figure 5 .

[0050] Performance testing: The samples prepared in Examples 1-3 above were subjected to water contact angle testing, roughness testing, and abrasion resistance testing; hydrophobicity was measured using an industrial camera and S-EYE, and the results are shown in Table 1 and 2. Figure 6-8 The roughness test instrument was a KC series laser spectroscopic confocal microscope from KEMS; the wear resistance test was conducted using a linear reciprocating wear tester, which was provided by Saneng Instruments (Wuxi) Co., Ltd. Table 1 shows the water contact angle of a 5 μL deionized water droplet on the sample surface.

[0051] Table 1. Hydrophobicity test results of samples in Examples 1-3

[0052] Table 2 shows the test results of the wear resistance of the samples in Examples 1-3.

[0053] The friction medium used in the experiment, as shown in Table 2, was a scouring pad, with a total load mass of 1000g. Test parameters were set as follows: friction speed 60 times / min, single stroke length 50mm. When the number of wear cycles reached the number listed in Table 2, the micro / nano structure began to gradually wear down; before reaching the required number of wear cycles, the micro / nano structure remained unchanged. In Examples 1-3, when the number of wear cycles reached 25,000, the micro / nano structure constructed by sodium chloride etching and the inorganic coating covering the Q235 steel plate surface of the samples were completely worn away, exposing the Q235 steel plate substrate. At this point, the original superhydrophobic properties of the sample surface were completely lost due to the wear of the micro / nano structure and the inorganic coating.

[0054] Table 3. Roughness test results of samples in Examples 1-3

[0055] As can be seen from Tables 1, 2 and 3, the superhydrophobic properties, abrasion resistance and surface roughness of the sample of the present invention are correlated with parameters such as the proportion of sodium chloride in the sodium chloride slurry, sodium chloride etching temperature and sodium chloride etching time.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures, characterized in that, Includes the following steps: (1) Substrate pretreatment: Remove and clean the surface oxide layer of the substrate; (2) Preparation of organic carrier: Mixed solvent and thickener are magnetically stirred in an oil bath at 60-90℃ for 1-2 hours until the thickener is completely dissolved. Then, thixotropic agent, dispersant and antioxidant are added. Stirring is continued at 60-90℃ for 1-2 hours. After cooling to room temperature, the mixture is defoamed by a vacuum defoamer and finally transferred to a small centrifuge tube for later use. (3) Slurry preparation: Low melting point glass powder and the organic carrier obtained in step (2) are mixed in proportion, and inorganic coating slurry is prepared by high-speed vacuum degassing and homogenization and three-roll rolling. Low melting point glass powder, sieved sodium chloride and organic carrier in step (2) are mixed in proportion, and sodium chloride slurry is prepared by high-speed vacuum degassing and homogenization and three-roll rolling. (4) Screen printing and inorganic coating sintering: Screen printing is used to print the inorganic coating pattern on the substrate surface in step (1) of the inorganic coating slurry obtained in step (3), and then sintering is performed to form an inorganic coating. (5) Screen printing and sodium chloride etching: Screen printing is used to print biomimetic patterns on the surface of the inorganic coating described in step (4) using the sodium chloride slurry obtained in step (3). After drying, the slurry is placed in a muffle furnace for etching. (6) Post-processing: The sample after etching in step (5) is treated with deionized water to remove sodium chloride in order to form micro-nano structures; (7) Preparation and treatment of superhydrophobic capsules: The post-treated micro-nano structure sample is immersed in the superhydrophobic capsule, pulled out and dried.

2. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (1), sandpaper is used to polish the steel plate until there is no obvious oxide layer on the surface and the scratches are consistent. After polishing, anhydrous ethanol is used to clean the steel plate to remove the shavings and oil. The substrate is a steel plate, including one of carbon steel, stainless steel, aluminum steel and cast iron.

3. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (2), the organic carrier contains, by mass fraction, 45-50% terpineol, 20-25% diethylene glycol butyl ether acetate and 6-10% dibutyl phthalate; The thickener accounts for 3-6% by mass, and the thixotropic agent includes 2-4% hydrogenated castor oil and 2-4% polyamide wax; The dispersant accounts for 4-6% of the mass, and the antioxidant accounts for 3-6% of the mass.

4. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (3), when the inorganic coating slurry is prepared, the glass powder is FD66 low melting point glass powder, a product of Anmi Micro-Nano New Materials Co., Ltd., with an initial melting temperature of 480℃; The inorganic coating slurry has a low melting point glass powder to organic carrier mass ratio of 3-4:0.8-1.

2. The high-speed vacuum degassing and homogenization parameters are 1000-1200 r / min for 2-5 min, repeated three to five times. The rolling thickness of the three-roll mill is 15-25 micrometers.

5. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (3), when the sodium chloride slurry is prepared, the sodium chloride powder is passed through 40 mesh, 100 mesh and 400 mesh sieves in sequence, and the particle size is controlled to be 38 micrometers or less; In the sodium chloride slurry, the mass ratio of glass powder:sodium chloride:organic carrier is a:b:c, where a ranges from 14 to 20, b ranges from 1 to 4, and c ranges from 14 to 18. The vacuum degassing and homogenization parameters are 1000-1200 r / min for 2-5 min, repeated three to five times, and the rolling thickness of the three-roll mill is 15-25 micrometers.

6. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (4), the pattern of the first screen printing plate used in screen printing is a square pattern; In step (5), the pattern of the second screen printing plate used in screen printing is a honeycomb pattern; Both types of screen printing plates have a mesh count of 200-400, and the thickness of the paste layer after printing is 15-30 micrometers.

7. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (4), during the sintering of the inorganic coating, the printed sample is first dried in an oven at 60-80℃ for 2-4 hours, and then placed in a muffle furnace for sintering: the heating rate is 5-10℃ / min, the temperature is held at 300-400℃ for 30-60 minutes to remove the adhesive, and the temperature is further increased to 600-700℃ at 5-10℃ / min and held for 15-25 minutes.

8. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (5), during sodium chloride etching, the sample after printing sodium chloride paste is first dried in an oven at 60-80℃ for 2-4 hours, and then placed in a muffle furnace for etching: the heating rate is 5-10℃ / min, the temperature is 300-400℃ for 30-60 minutes for desizing, and the temperature is further increased to 550-700℃ at 5-10℃ / min and held for 10-20 minutes.

9. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (6), the sample is soaked in deionized water at 80-100℃ for 2-5 hours to remove residual sodium chloride after etching.

10. The method for preparing a wear-resistant superhydrophobic coating for sodium chloride-etched micro / nano structures according to claim 1, characterized in that, In step (7), the preparation method of the superhydrophobic capsule includes the following steps: mixing PFTDS, Tween 80 and deionized water in a mass ratio of x:y:z, wherein x ranges from 8 to 10, y ranges from 0.5 to 1, and z ranges from 180 to 220, and then homogenizing at 5000-6000 r / min for 100-160 min to obtain an oil-in-water microemulsion; The oil-in-water microemulsion was then transferred to a magnetic stirrer and stirred for 80-100 minutes. During stirring, a pre-set amount of fumed alumina was slowly added first, and after it was completely dispersed in the microemulsion, fumed silica was slowly added next. The fumed alumina and fumed silica were prepared in a mass ratio of m:n, where m ranges from 5.5 to 6.5 and n ranges from 0.5 to 1.5, with a total mass of 10.0-15.0 g. The sample was immersed in the superhydrophobic capsule emulsion for 25-45 minutes, then lifted and dried in an oven at 100-120℃ for 12-16 hours.

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