A metal-based anti-icing and drag-reducing superhydrophobic surface and its preparation method

Abstract

The present invention discloses a preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface, comprising the following steps: (1) The metal surface is polished, and then placed in absolute ethanol for ultrasonic cleaning and dried; (2) The obtained product in step (1) is processed by nanosecond laser to prepare a rhombic array with a circular protrusion in the center. After processing, it is ultrasonically cleaned in absolute ethanol, rinsed with deionized water and then naturally dried; (3) Then the obtained product in step (2) is placed in a low surface energy solution, vacuum dried, then left standing in a cool place, taken out, cleaned with absolute ethanol and air dried. The present invention also discloses the metal-based anti-icing and drag-reducing superhydrophobic surface obtained by this method. The superhydrophobic surface of the present invention has the properties of drag reduction and anti-icing, can solve the two key problems in the surface engineering of polar ships, namely underwater drag reduction and water surface anti-icing, extends the icing time by 4 times under extremely cold conditions, and achieves a drag reduction rate of 39%.

Description

Technical Field

[0001] The present invention belongs to superhydrophobic surfaces and preparation methods, and particularly relates to a metal-based anti-icing and drag-reducing superhydrophobic surface and a preparation method thereof. Background Art

[0002] In the process of economic globalization, shipping is crucial for global trade as it is generally one of the most economical and environmentally friendly transportation methods. With global warming, the Arctic ice coverage area is decreasing day by day, and the opening of the Arctic shipping route has brought great opportunities to ship transportation. However, opportunities are always accompanied by challenges. Polar ships need to face three classic problems during navigation - anti-icing on water, icebreaking on the water surface, and drag reduction underwater. Among them, icebreaking on the water surface is determined by the structural strength of the hull, while anti-icing on water and drag reduction underwater are both related to the surface structure and its performance.

[0003] Currently, research on icebreaking of the hull structure has been relatively mature, while there is a lack of relevant research on underwater drag reduction and anti-icing on the hull surface. The existence of resistance is an issue that cannot be ignored during ship navigation, and these resistances consume a considerable amount of energy and resources. Among them, frictional resistance is one of the main components of resistance, accounting for about 60 - 80% of the total resistance. In addition, ship icing caused by severe cold not only poses a great threat to hull equipment but also risks for crew deck operations. Once the exposed deck equipment freezes, it is extremely easy to cause cracks at the interfaces, leading to potential safety hazards. The freezing of communication equipment such as radar antennas will also seriously affect the external communication function, resulting in many difficulties in shipping.

[0004] Therefore, solving the two problems of underwater drag reduction and anti-icing on water has become a key and difficult problem in the surface engineering of polar ships. Superhydrophobic surfaces have not only made significant progress in the field of drag reduction but also been widely applied in the field of anti-icing, providing important ideas for meeting the requirements of underwater drag reduction and anti-icing on water for polar ships.

[0005] The patent with the application number CN201110407972.9 discloses a bionic micro-nano composite structure anti-icing surface and its preparation method. A micron structure is fabricated on the surface using machining methods and laser etching, and then a nano structure is grown on the surface through hydrothermal synthesis. Subsequently, the surface is modified by vacuum evaporation of fluorine-containing compounds. This method is not only cumbersome and costly to manufacture, but also highly polluting to the environment due to the use of fluorine-containing compounds. The patent with the application number CN201110396837.9 discloses a drag-reducing superhydrophobic coating based on electroless metal deposition technology and its preparation method. A micro-nano structure is prepared on a metal substrate using metal deposition technology and vapor deposition, and then modified with low surface energy substances. This surface has a 20% drag reduction effect. However, the drag reduction effect of this superhydrophobic surface is limited, and it does not address the drag reduction situation on the surface under cold conditions. Its application environment is relatively limited and it is still difficult to apply in complex environments.

[0006] Generally speaking, there is currently a lack of a solution that can simultaneously meet the drag reduction requirements for the underwater part of a ship and the anti-icing requirements for the above-water part of the hull. Summary of the Invention

[0007] Object of the Invention: To overcome the deficiencies in the prior art, the object of the present invention is to provide a preparation method for an anti-icing and drag-reducing superhydrophobic surface that is free of fluorine-containing compounds and environmentally friendly. Another object of the present invention is to provide an anti-icing and drag-reducing superhydrophobic surface suitable for polar ships to solve the problems of icing and navigation resistance under extremely cold conditions.

[0008] Technical Solution: The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to the present invention includes the following steps:

[0009] (1) The metal surface is polished and then placed in absolute ethanol for ultrasonic cleaning, and then dried.

[0010] (2) The product obtained in step (1) is processed by nanosecond laser to prepare a rhombic array with a circular protrusion in the center. After processing, it is ultrasonically cleaned in absolute ethanol, rinsed with deionized water, and then air-dried naturally.

[0011] (3) Then the product obtained in step (2) is placed in a low surface energy solution, vacuum dried, and then left to stand in a cool place. It is taken out, cleaned with absolute ethanol, and air-dried to obtain a metal-based anti-icing and drag-reducing superhydrophobic surface.

[0012] Further, in step (1), the metal is any one of brass, aluminum alloy, and stainless steel, preferably brass. The combination effect between the brass surface and the low surface energy substance is better, and the time for low surface energy treatment is shorter. The temperature of ultrasonic cleaning is 20 - 60 °C, the ultrasonic frequency is 20 - 100 KHz, the input power is 50 - 200 W, and the cleaning time is 5 - 10 min. Drying is carried out at a constant temperature of 40 - 100 °C for 10 - 30 min. The grinding and polishing treatment is carried out by a grinding machine, and the metal surface is sanded with 1000cw sic sandpaper.

[0013] Further, in step (2), the rhombic array includes a number of rhombic structures. The distance between the rhombic structures is 8 - 12 μm, the length of the long diagonal is 100 - 150 μm, the horizontal spacing is 180 - 200 μm, and the vertical spacing is 35 - 40 μm. The diameter of the circular protrusion is 20 - 30 μm. The scanning speed of the nanosecond laser processing is 100 - 500 mm / s, the laser frequency is 20 - 200 kHz, the pulse width is 5 - 20 μs, the current intensity is 1 - 3 A, and the number of processing layers is 8 - 10 layers. The role of the circular protrusion is to provide a hierarchical composite structure. Without it, it is a single rhombic structure, which will lead to a decrease in its surface roughness and hydrophobicity.

[0014] Further, in step (3), the low surface energy solution is myristic acid solution, n-dodecyl mercaptan solution, or stearic acid solution, and the concentration is 0.07 - 0.2 mol / L, preferably myristic acid solution, with a shorter treatment time and better effect. The pressure of vacuum drying is 0.05 - 0.10 MPa, the time is 10 - 20 min, and the standing time is 7 - 9 h.

[0015] The metal-based anti-icing and drag-reducing superhydrophobic surface obtained by the above preparation method of the metal-based anti-icing and drag-reducing superhydrophobic surface is in the shape of an iris leaf.

[0016] The present invention is inspired by a cold-resistant iris plant that inhabits the vicinity of water-edge wetlands. The leaves of this iris plant remain emerald green in winter and possess excellent cold-resistant characteristics. The hydrophobic properties of the iris plant leaves vary at different stages. In the seedling stage, the leaves exhibit excellent superhydrophobicity. Compared with lotus leaves, the iris plant has stronger tolerance to cold environments. The humidity at water-edge wetlands is extremely high, and water vapor easily adheres to the leaf surface. However, when water vapor or water mist condenses on the leaf surface, the superhydrophobicity of the leaves causes the droplets to roll off rapidly. By observing the microscopic images of the leaves, it is found that the leaf structure is a rhomboid-like composite structure. The longest diagonal of the rhomboid-like structure is 100 - 150 μm, and the convex structure is located at the center of the rhomboid-like structure. By using a higher magnification lens for observation, it can be found that the composite structure is composed of flaky structures. This special composite structure and flaky structure can significantly reduce the contact area between the droplet and the leaf surface, reduce the resistance of the droplet rolling off the surface, and obtain an anti-icing effect by inhibiting the growth of ice crystals on the surface. Based on this surface microstructure, the present invention has successfully prepared a superhydrophobic surface imitating the iris family that simultaneously has anti-icing and drag reduction properties.

[0017] Preparation principle: Through the research and simulation of iris plants, an array composite micro-scale structure imitating the iris family is fabricated on a metal substrate. After the metal surface is treated by laser processing and burning, the surface roughness of the substrate significantly increases, making the metal surface become superhydrophilic. After being modified with a low surface energy solvent, the flaky nano-structure on the surface of the iris plant is successfully simulated on the metal substrate. Under the combined action of the micro-scale and nano-scale rough structures imitating the iris family, the smooth metal surface becomes rough.

[0018] Since the modification of the metal surface with a low surface energy solvent makes the metal surface hydrophobic, the metal surface becomes hydrophobic. According to the Wenzel wetting state model, the increase in the surface roughness of a hydrophobic surface will result in the surface being more hydrophobic, and the biomimetic micro-nano structure generated by laser etching and low surface energy modification gives the metal surface extremely high roughness. Therefore, the combined action of the array composite rough structure imitating the iris plant and the hydrophobic treatment with a low surface energy substance endows the metal surface with excellent superhydrophobic properties.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. The superhydrophobic surface simultaneously possesses two properties of drag reduction and anti-icing. Therefore, it can simultaneously solve two key problems in the surface engineering of polar ships, namely underwater drag reduction and above-water anti-icing. The prepared superhydrophobic surface with an iris family structure can extend the ice formation time by 4 times under extremely cold conditions and can achieve a drag reduction rate of 39%.

[0021] 2. The superhydrophobic surface still maintains a rolling angle of 5° in an ultra-low temperature environment, enabling the liquid to remain in a flowing state without freezing, thus solving the problem that polar ships are extremely prone to icing in a sea fog environment and after seawater splashing.

[0022] 3. Compared with other methods, the preparation method of the present invention greatly simplifies the processing technology, provides the possibility for the large-scale application of superhydrophobic performance in industry, and also ensures no environmental pollution caused by the corrosion of fluorine-containing compounds. Brief Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of the rhombic structure of the present invention;

[0024] Figure 2 is a 3D height diagram of the rhombic structure of the present invention;

[0025] Figure 3 is a scanning electron microscope image. Among them, a, b, and c are the surface topography diagrams of irises under scales of 50μm, 10μm, and 2μm respectively, and d, e, and f are the surface topography diagrams of the anti-icing superhydrophobic surface obtained in Example 2 of the present invention under scales of 50μm, 10μm, and 2μm respectively;

[0026] Figure 4 is the static water contact angle of the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention in air;

[0027] Figure 5 is the dynamic water repellency of the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention in air;

[0028] Figure 6 is an image of the freezing time of distilled water droplets on the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention and on the surface of a smooth metal substrate;

[0029] Figure 7 is an image of the freezing time of simulated seawater droplets on the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention and on the surface of a smooth metal substrate;

[0030] Figure 8 is a curve showing the drag reduction rate of the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention and a smooth metal substrate in a rheometer test;

[0031] Figure 9 is an image of droplets rolling off the anti-icing and drag-reducing superhydrophobic surface obtained in the present invention in an environment of -10°C. Detailed Embodiments

[0032] To prove that the prepared sample successfully imitated the array composite structure of irises, the surface of the bionic prepared sample and the surface of irises were observed through a microscope, and the surface morphologies of the two were compared to verify that the surface prepared by bionics had similar micro- and nano-scale structures to the surface of irises, thus verifying that the prepared bionic surface successfully simulated the unique structure of irises. Example 1 was carried out.

[0033] To verify whether the prepared surface of the irises imitated array composite structure had excellent superhydrophobic, anti-icing and drag reduction properties, a bouncing experiment, a droplet freezing experiment and a droplet flow performance test were carried out. The dynamic superhydrophobic performance was evaluated by comparing the bouncing height of the droplet and the contact time of the droplet on the surface; the anti-icing performance of the prepared bionic surface was evaluated by comparing the freezing time of the droplet on the bionic surface; and the drag reduction performance of the prepared bionic surface was judged by measuring the slip length with a rheometer. Example 2 was carried out.

[0034] To verify that the prepared surface of the irises imitated array composite structure could still maintain an ultra-low rolling angle in an ultra-low temperature environment, enabling the liquid to remain in a flowing state without freezing. A rolling angle test experiment of the droplet in a low temperature environment was carried out, and the low temperature superhydrophobic performance of the prepared surface was verified by observing the rolling angle of the droplet in a low temperature environment. Example 2 was carried out.

[0035] To verify that the prepared surface of the irises imitated array composite structure could be prepared on different metal substrates, bionic surfaces were prepared on the surfaces of aluminum and stainless steel, and the hydrophobic performance of the surface was measured to verify that this example could prepare superhydrophobic surfaces on different metal substrates. Example 3 was carried out.

[0036] Example 1

[0037] A preparation method of a metal-based anti-icing and drag reduction superhydrophobic surface includes the following steps:

[0038] (1) Using brass as the base material (20mm×20mm×2mm), first carry out pretreatment: polish the brass surface with 1000-mesh sic sandpaper to remove copper oxide, and then use anhydrous ethanol and deionized water to ultrasonically clean the treated brass surface at 30°C for 5 minutes, with an ultrasonic frequency of 40KHz and an input power of 100W to remove surface residues. Finally, place it in a constant temperature drying oven at 70°C for 10 minutes for drying.

[0039] (2) Use laser processing to prepare a diamond array structure on the surface of the treated brass sample. The laser parameters used are: the processed size is a 20*20mm square, the pulse width is 5μs, the frequency is 100kHz, the scanning speed is 400mm / s, the current is 1A, and the number of processed layers is 10 layers. As Figures 1 - 2, The processed diamond structures are 10 μm apart from each other. The length of the long diagonal of the diamond array is 100 μm, one angle of the diamond is 20°, the lateral spacing of the center of the diamond array is 200 μm, and the longitudinal spacing is 40 μm. The center of the circular protrusion is located at the exact center of the diamond structure, and the diameter is 20 μm. After processing, ultrasonic cleaning is carried out in absolute ethanol, and it is rinsed with deionized water and then air-dried naturally.

[0040] (3) Then, the product obtained in step (2) is put into a low surface energy solution of myristic acid solution with a concentration of 0.1 mol / L, placed in a vacuum drying oven to evacuate the air. The pressure of the vacuum drying oven is set to 0.08 MPa, and the time for evacuating the air is 10 min. Subsequently, it is left standing in a cool place for 8 h. It is taken out and washed with absolute ethanol, and then air-dried naturally at room temperature to obtain the anti-icing superhydrophobic surface S1 with a multi-level microstructure.

[0041] As Figure 3 shown, the bionic superhydrophobic S1 surface and the surface of the iridaceae plants are observed by using a scanning electron microscope. It can be observed that the prepared surface has a similar micro- and nano-scale structure to the surface of the iridaceae plants, and the prepared bionic surface successfully simulates the unique structure of the iridaceae plants. By observing Figure 3 the microscope image of the leaf of the iridaceae, it is found that the structure of the leaf is a composite structure in the shape of a quasi-rhombic array, and the convex structure is located at the center of the quasi-rhombic structure.

[0042] Example 2

[0043] A preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface, comprising the following steps:

[0044] (1) Using brass as the substrate (20 mm × 20 mm × 2 mm), first perform pretreatment: polish the brass surface with 1000-mesh sic sandpaper to remove copper oxide, and then use absolute ethanol and deionized water to perform ultrasonic cleaning on the treated brass surface at 30 °C for 5 min, with an ultrasonic frequency of 40 KHz and an input power of 100 W to remove surface residues. Finally, put it into a constant temperature drying oven at 70 °C for 10 min for drying.

[0045] (2) A diamond array structure was prepared on the surface of the treated brass sample by laser processing. The laser parameters used were as follows: the processed size was a 20*20 mm square, the pulse width was 5 μs, the frequency was 100 kHz, the scanning speed was 400 mm / s, the current was 1 A, and the number of processed layers was 10. The distance between the processed diamond structures was 10 μm, the length of the long diagonal of the diamond array was 150 μm, one angle of the diamond was 20°, the lateral spacing of the diamond array center was 200 μm, and the longitudinal spacing was 40 μm. The center of the circular protrusion was located at the exact center of the diamond structure, and the diameter was 25 μm. After processing, ultrasonic cleaning was carried out in absolute ethanol, and after rinsing with deionized water, it was naturally dried.

[0046] (3) Then, the product obtained in step (2) was placed in a low surface energy solution of myristic acid with a concentration of 0.1 mol / L, and vacuum was pumped in a vacuum drying oven. The pressure of the vacuum drying oven was set to 0.08 MPa, and the vacuum pumping time was 10 min. Subsequently, it was left to stand in a cool place for 8 h. It was taken out and cleaned with absolute ethanol, and then naturally air-dried at room temperature, thus obtaining the anti-icing superhydrophobic surface S2 with a multi-level microstructure.

[0047] Example 3

[0048] The remaining steps of this example are the same as those of Example 1, except for the different size parameters of the diamond structure, and the bionic superhydrophobic surface S3 was obtained. The distance between the diamond structures of the bionic superhydrophobic surface S3 was 10 μm, the length of the long diagonal of the diamond array was 200 μm, one angle of the diamond was 20°, the lateral spacing of the diamond array center was 200 μm, and the longitudinal spacing was 40 μm. The center of the circular protrusion was located at the exact center of the diamond structure, and the diameter was 30 μm.

[0049] As Figure 4 shown, the bionic superhydrophobic surfaces S1, S2, and S3 prepared according to the above steps all have excellent static contact angles in the air. The static contact angle of S1 is 154°, the static contact angle of S2 is 157°, and the static contact angle of S3 is 151°.

[0050] As Figure 5 shown, the bionic superhydrophobic surfaces prepared according to the above steps have excellent dynamic water repellency. The liquid droplet can successfully achieve the processes of spreading, contracting, and bouncing on the bionic superhydrophobic surface.

[0051] The liquid droplet takes 2.2 ms to expand to the maximum diameter on the superhydrophobic S1 surface (SH-S1) and bounces within 11.4 ms.

[0052] The liquid droplet takes 1.8 ms to expand to the maximum diameter on the superhydrophobic S2 surface (SH-S2) and bounces within 8.2 ms.

[0053] It takes 1.8 ms for the droplet to expand to the maximum diameter on the superhydrophobic S3 surface (SH-S3) and bounce within 9 ms.

[0054] The above results show that the contact time of the droplet on the S2 surface is the shortest, indicating that the superhydrophobic S2 surface has the best dynamic water repellency.

[0055] As Figure 6 shown, in an environment of -10 °C, the bionic superhydrophobic surface prepared according to the above steps can effectively delay the freezing time of the distilled water droplet on the surface.

[0056] By observing the freezing process, it can be found that there are differences in the pre-cooling stage and ice nucleation growth time between the untreated bare substrate and the samples with three different microstructural sizes. First, analyze the pre-cooling stage of each sample. Compared with the 90 s pre-cooling time of the untreated bare substrate, the time required for the samples SH-S1, SH-S2, and SH-S3 to form an ice shell is 236 s, 370 s, and 200 s, respectively. The time of all three samples has been significantly extended. The heat transfer process between the sample and the droplet is hindered due to the presence of microstructures and low surface energy substances, and the heat transfer rate has decreased by 1 - 3 times. Subsequently, analyze the ice shell growth stage of each sample. This stage starts counting from the sudden formation of an ice crystal shell on the droplet surface. The ice shell growth time of the untreated bare substrate is only 9 s, the ice shell growth times of the samples SH-S1 and SH-S3 are 22 s and 27 s, respectively, while the ice nucleation growth time of the sample SH-S2 reaches 61 s. This means that after the ice shell is formed, the heat transfer rate inside the droplet on the surface of the sample SH-S2 is significantly lower than that of other samples. As a result, the ice shell growth time is much longer than that of other samples.

[0057] Therefore, the sample SH-S2 has the longest freezing time, proving that the sample SH-S2 has the best anti-icing performance in the test of distilled water droplets, which means that the microstructural size of this sample has the best anti-icing performance.

[0058] As Figure 7As shown, in order to simulate the icing caused by seawater splashing, a 3.5% NaCl solution was also selected for the delayed icing experiment. The bionic diamond array composite structure sample can also effectively extend the icing time of droplets during the experiment with the saline solution. Compared with the untreated substrate, the delayed icing time of the bionic diamond array composite structure sample is significantly extended. When using the saline solution for the experiment instead of distilled water as the droplet, the freezing time of each sample surface is correspondingly extended. For the saline solution, the freezing point can be reduced to -2.2 °C, which also leads to a significant increase in the icing time of each sample. By observing the freezing process of the saline solution, it can be found that the contact angle of sample SH-S2 decreases slowly, and its freezing time is significantly longer than that of other-sized samples. Compared with the bare substrate, the freezing time of sample SH-S2 is extended by about 4.7 times and it is not completely frozen until 640 s. In the delayed icing experiment with saline, the difference in the time required for icing between each sample increases significantly. The time required for sample SH-S2 to form an ice shell is delayed by a factor of two compared to samples SH-S1 and SH-S3. However, after the ice shell is formed, there is no obvious difference in the time for the ice-water interface to rise to the top. In addition, it can be found that when using the saline solution for the experiment, even after complete icing, no spikes can form on the droplet surface. This is attributed to the influence of the soluble salts in the salt solution on the surface tension of the droplet.

[0059] After the icing experiment with saline, it was found that the complete freezing time of the saline on the surface of sample SH-S2 is the longest, which is 4 times that of the bare substrate. Thus, it is proved that sample SH-S2 has the best anti-icing performance in the seawater environment, which means that the microstructure size of this sample has the best anti-icing performance.

[0060] As Figure 8 shown, by measuring the surface of the sample with a rheometer, it was found that surfaces S1, S2, and S3 all showed excellent slip lengths in the rheometer test, indicating that the bionic superhydrophobic surface prepared in this invention has excellent drag reduction performance.

[0061] The superhydrophobic S1 (SH-S1) surface has a drag reduction rate of 30% - 35%.

[0062] The superhydrophobic S2 (SH-S2) surface has a drag reduction rate of 35% - 39%.

[0063] The superhydrophobic S3 (SH-S3) surface has a drag reduction rate of 25% - 30%.

[0064] Among them, the superhydrophobic S2 surface (SH-S2) has the most excellent drag reduction rate, which can reach up to 39%. At the same time, the superhydrophobic S2 surface has the most excellent bouncing performance and the best anti-icing performance. This indicates that the prepared superhydrophobic S2 surface has the best microstructure size compared with other surfaces, enabling the superhydrophobic S2 surface to simultaneously possess the excellent anti-icing performance of quadrupling the icing time and the best drag reduction rate of 39%.

[0065] The rolling angle performance of the prepared bionic superhydrophobic surfaces S1, S2, and S3 was detected at -10°C, and the obtained results are as Figure 9 shown. It can be observed that the rolling angle of the bionic superhydrophobic S2 surface prepared by the present invention in an environment of -10°C is only 5°.

[0066] Example 4

[0067] Table 1 Surface Contact Angle Measurement Results

[0068]

[0069] Table 2 Surface Rolling Angle Measurement Results

[0070]

[0071] Three groups of parallel experiments were designed, and the remaining steps were the same as those in Example 1, except that: the metal substrates used were different, specifically 304 stainless steel, 316L stainless steel, and aluminum alloy. The performance of the prepared superhydrophobic surfaces was detected respectively, and the measurements were repeated four times. The obtained results are shown in the following table.

[0072] Example 5

[0073] A preparation method of an anti-icing and drag-reducing superhydrophobic surface includes the following steps:

[0074] (1) Using aluminum alloy as the substrate (20mm×20mm×2mm), first perform pretreatment: polish the brass surface with 1000-mesh sic sandpaper to remove aluminum oxide, and then sequentially use absolute ethanol and deionized water to perform ultrasonic cleaning on the treated brass surface at 20°C for 10 min, with an ultrasonic frequency of 20 KHz and an input power of 50 W to remove surface residues. Finally, place it in a constant temperature drying oven at 40°C for 20 min for drying.

[0075] (2) A diamond array structure was prepared on the surface of the treated brass sample by laser processing. The laser parameters used were as follows: the processed size was a 20*20 mm square, the pulse width was 20 μs, the frequency was 50 kHz, the scanning speed was 100 mm / s, the current was 3 A, and the number of processing layers was 8 layers. The distance between the processed diamond structures was 12 μm, the length of the long diagonal of the diamond array was 100 μm, one angle of the diamond was 20°, the lateral spacing of the diamond array center was 180 μm, and the longitudinal spacing was 35 μm. The center of the circular protrusion was located at the exact center of the diamond structure, and the diameter was 22 μm. After processing, ultrasonic cleaning was carried out in absolute ethanol, and after rinsing with deionized water, it was air-dried naturally.

[0076] (3) Then the product obtained in step (2) was put into a low surface energy solution of 1-dodecanethiol with a concentration of 0.2 mol / L, placed in a vacuum drying oven for vacuum pumping. The pressure of the vacuum drying oven was set to 0.05 MPa, and the vacuum pumping time was 20 min. Subsequently, it was left to stand in a cool place for 9 h. It was taken out and cleaned with absolute ethanol, and then air-dried naturally at room temperature to obtain an anti-icing superhydrophobic surface with a multi-level micro-structure.

[0077] Example 6

[0078] A preparation method of an anti-icing and drag-reducing superhydrophobic surface, comprising the following steps:

[0079] (1) Using brass as the substrate (20 mm×20 mm×2 mm), first, pretreatment was carried out: the brass surface was polished with 1000-mesh sic sandpaper to remove copper oxide, and then the treated brass surface was ultrasonically cleaned in absolute ethanol and deionized water at 60 °C for 7 min, with an ultrasonic frequency of 100 KHz and an input power of 200 W to remove surface residues. Finally, it was placed in a constant temperature drying oven at 100 °C for 30 min for drying.

[0080] (2) A diamond array structure was prepared on the surface of the treated brass sample by laser processing. The laser parameters used were as follows: the processed size was a 20*20 mm square, the pulse width was 10 μs, the frequency was 200 kHz, the scanning speed was 500 mm / s, the current was 2 A, and the number of processing layers was 9 layers. The distance between the processed diamond structures was 8 μm, the length of the long diagonal of the diamond array was 130 μm, one angle of the diamond was 20°, the lateral spacing of the diamond array center was 190 μm, and the longitudinal spacing was 37 μm. The center of the circular protrusion was located at the exact center of the diamond structure, and the diameter was 28 μm. After processing, ultrasonic cleaning was carried out in absolute ethanol, and after rinsing with deionized water, it was air-dried naturally.

[0081] (3) Then, the product obtained in step (2) is put into a low surface energy solution of stearic acid with a concentration of 0.2 mol / L, placed in a vacuum drying oven to evacuate the air. The pressure of the vacuum drying oven is set to 0.10 MPa, and the time for evacuating the air is 15 min. Subsequently, it is left to stand in a cool place for 7 h. It is taken out and washed with absolute ethanol, and then naturally air-dried at room temperature to obtain an anti-icing superhydrophobic surface with a multi-level microstructure.

Claims

1. A preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface, characterized in that, it includes the following steps: (1) Grind and polish the metal surface, then put it into absolute ethanol for ultrasonic cleaning, and dry it; (2) Perform nanosecond laser processing on the surface of the product obtained in step (1) to prepare a diamond array with a circular protrusion in the center. After processing, perform ultrasonic cleaning in absolute ethanol, rinse with deionized water, and then air-dry naturally; (3) Then put the product obtained in step (2) into a low surface energy solution, vacuum dry it, then let it stand in a cool place, take it out, clean it with absolute ethanol, and air-dry it to obtain a metal-based anti-icing and drag-reducing superhydrophobic surface; The low surface energy solution is myristic acid solution, n-dodecyl mercaptan solution or stearic acid solution, and the concentration is 0.07~0.2mol / L; In the step (2), the diamond array includes several diamond structures. The distance between the diamond structures is 8~12μm, the length of the long diagonal is 100~150μm, the horizontal spacing of the center of the diamond array is 180~200μm, and the vertical spacing is 35~40μm; the diameter of the circular protrusion is 20~30μm.

2. The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to claim 1, characterized in that: In the step (1), the metal is any one of brass, aluminum alloy, and stainless steel.

3. The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to claim 1, characterized in that: In the step (1), the temperature of ultrasonic cleaning is 20~60°C, the ultrasonic frequency is 20~100KHz, the input power is 50~200W, and the cleaning time is 5~10min.

4. The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to claim 1, characterized in that: In the step (1), drying is carried out at a constant temperature of 40~100°C for 10~30min.

5. The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to claim 1, characterized in that: In the step (2), the scanning speed of nanosecond laser processing is 100~500mm / s, the laser frequency is 50~200kHz, the pulse width is 5~20μs, the current intensity is 1~3A, and the number of processing layers is 8~10 layers.

6. The preparation method of a metal-based anti-icing and drag-reducing superhydrophobic surface according to claim 1, characterized in that: In the step (3), the pressure of vacuum drying is 0.05~0.10MPa, the time is 10~20min, and the standing time is 7~9h.

Images