A multi-scale wear-resistant superhydrophobic drag-reducing surface and its preparation method

Abstract

The present invention relates to the technical field of hydrodynamics, and particularly relates to a multi-scale wear-resistant superhydrophobic drag-reducing surface and a preparation method thereof, including: a substrate having a drag-reducing surface; the drag-reducing surface includes large ribs with a trapezoidal cross-section and grooves arranged at intervals; small ribs with a rectangular cross-section are provided on both sides of the upper end surface of the large ribs; a superhydrophobic coating is coated on the surfaces of the small ribs, large ribs and grooves. It can solve the problems that the coating on the top of the ribs will quickly fail after mechanical wear and the contact area increases due to water immersion in the grooves, resulting in a decrease in drag-reducing efficiency or even an increase in drag. The preparation of the superhydrophobic coating and the structures of the small ribs, large ribs and grooves is simple and easy to implement, and more excellent drag-reducing stability and efficiency can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrodynamics, and particularly relates to a multi-scale wear-resistant superhydrophobic drag reduction surface and a preparation method thereof. Background Art

[0002] When a ship sails, the water resistance it encounters consumes a large amount of energy. Among them, the frictional resistance accounts for the largest proportion of the total resistance. Reducing the frictional resistance can save a large amount of energy for the ship. When water flows over a solid surface, due to viscous action, a shear force will be generated on the solid surface, which is the main reason for generating frictional resistance. The methods for reducing frictional resistance mainly include air lubrication drag reduction, bionic jet drag reduction, surface microstructure design, superhydrophobic surfaces, etc. The air lubrication technology realizes drag reduction by actively injecting gas to form an air layer on the surface, but it requires the installation of a complex air pumping system. The bionic jet drag reduction technology is inspired by the jet phenomenon of shark gills and requires the installation of jet holes on the surface. However, both of the above two technologies require the modification of the ship hull, which is costly and difficult to apply on a large scale. In contrast, when a superhydrophobic surface comes into contact with the water surface, air can be trapped in the gaps of the micro-nano structures, thereby transforming the solid-liquid contact between the surface and the water flow into a solid-gas-liquid contact, causing the water flow to produce a certain slip on the solid surface, reducing the shear force of the water flow on the wall surface, and ultimately reducing the frictional resistance. Generally, a surface with a contact angle > 150° and a sliding angle < 10° is considered a superhydrophobic surface.

[0003] In the prior art, superhydrophobic coatings are combined with groove structures to achieve more efficient drag reduction; however, these groove sizes are relatively large, and the groove spacing is not regulated, failing to effectively limit the role of vortices under high-speed flow. When water flows into the grooves, the overall surface even shows an increased resistance state, failing to achieve the ideal drag reduction effect. Most of the coatings have poor wear resistance. Even when materials such as resins are added to enhance the wear resistance, the characteristics of the micro-nano structures determine that it is still difficult to resist the wear of the micro-nano structures caused by contact friction with objects such as metals. The coating on the top of the rib will quickly fail after mechanical wear, reducing the drag reduction performance and making it difficult to apply in practice. On the other hand, when the water pressure is relatively large, the water flow will flow into the grooves and even completely contact the bottom of the grooves, which increases the contact area between the water flow and the surface, reducing the drag reduction effect and even increasing the surface resistance. At present, few studies have taken reasonable solutions to this problem. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-scale wear-resistant superhydrophobic drag reduction surface and a preparation method thereof, which can solve the problems that the coating on the top of the rib will quickly fail after mechanical wear and the contact area increases due to water immersion in the grooves, resulting in a reduction in drag reduction efficiency or even an increase in resistance.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A multi-scale wear-resistant superhydrophobic drag reduction surface, comprising:

[0006] A substrate having a drag-reducing surface; the drag-reducing surface includes large ribs and grooves with trapezoidal cross-sections arranged at intervals; small ribs with rectangular cross-sections are provided on both sides of the upper end surface of the large ribs; a superhydrophobic coating is applied to the surfaces of the small ribs, large ribs and grooves.

[0007] Furthermore, the grooves have a pitch of 240 - 360 μm, a groove width of 160 - 240 μm, and a groove depth of 120 μm.

[0008] Furthermore, the bottom of the groove has a porous shrub-like structure.

[0009] A preparation method for a multi-scale wear-resistant superhydrophobic drag-reducing surface, comprising the following steps:

[0010] Step 1: Preparation of small ribs, large ribs and grooves: Using a pulsed laser with a laser frequency of 30 kHz and a pulse width of 1 μs, processing the substrate according to a pattern at a processing speed of 500 mm / s and a processing path line density of 0.025 mm for 16 times; cleaning the processed substrate.

[0011] Step 2: Preparation of superhydrophobic coating emulsion: Mixing octadecyltrichlorosilane and silica nanoparticles in a ratio of 1 mL : 50 mg evenly and reacting fully.

[0012] Step 3: Preparation of superhydrophobic coating spraying liquid: Diluting the superhydrophobic coating emulsion obtained in Step 2 and performing ultrasonic dispersion.

[0013] Step 4: Preparation of multi-scale wear-resistant superhydrophobic drag-reducing surface: Uniformly spraying the superhydrophobic coating spraying liquid obtained in Step 3 onto the surfaces of the small ribs, large ribs and grooves obtained in Step 1, and then drying at room temperature to obtain a multi-scale wear-resistant superhydrophobic drag-reducing surface.

[0014] Furthermore, the ultrasonic frequency in Step 3 is 40 kHz.

[0015] Furthermore, in Step 4, a spray gun is used for the spraying; the spray gun orifice diameter is 0.3 mm, the spraying distance is 10 cm, the spraying time is 1 s, and the drying time is 24 h.

[0016] Furthermore, the substrate is a metal material.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. Provide a multi-scale wear-resistant superhydrophobic drag-reducing surface and its preparation method, combining the drag-reducing effect of the groove structure with the high water repellency of the superhydrophobic coating for water drag reduction and achieving a combined effect.

[0019] 2. At low flow velocities, the coating in the surface grooves prevents water flow from infiltrating, reduces the contact area between the water flow and the surface, and decreases the frictional force. At high flow velocities, part of the grooves is wetted by water. At this time, the grooves can limit the action of high-speed vortices on the surface and reduce the frictional force. That is, this surface can achieve good drag reduction effects in various flow states and will not fail.

[0020] 3. The combination of a porous shrub-like structure with micron-scale large pores and nano-rough structures coexisting and a superhydrophobic coating can greatly reduce the contact area between the inside of the grooves and the water flow.

[0021] 4. The preparation of the superhydrophobic coating, small ribs, large ribs, and groove structures is simple and easy to implement, and can achieve more excellent drag reduction stability and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present invention and do not limit the present invention.

[0023] Figure 1 It is a schematic diagram of the overall multi-scale wear-resistant superhydrophobic drag reduction surface of the present invention.

[0024] Figure 2 It is a surface topography diagram of the present invention at different line densities of laser processing paths.

[0025] Figure 3 It is a surface topography diagram of the present invention at different numbers of laser processing times.

[0026] Figure 4 It is a surface topography diagram of the present invention after laser processing.

[0027] Figure 5 It is a surface topography diagram of the present invention after spraying the superhydrophobic coating.

[0028] Figure 6 It is a diagram of the elemental composition of the surface microstructure of the present invention.

[0029] Figure 7 It is a surface contact angle test diagram of the present invention.

[0030] Figure 8 It is a diagram of the drag reduction experimental device of the present invention.

[0031] Figure 9 It is a diagram of the drag force test results of the present invention.

[0032] Figure 10 It is a schematic diagram of the underwater durability experiment of the present invention.

[0033] Figure 11This is the underwater durability test result diagram of the present invention.

[0034] Figure 12 This is the schematic diagram of the mechanical durability test of the present invention.

[0035] Figure 13 This is the mechanical durability test result diagram of the present invention. Detailed implementation manners

[0036] The present invention will be further described below through specific embodiments:

[0037] Refer to Figure 1 , a multi-scale wear-resistant superhydrophobic drag reduction surface, comprising:

[0038] A substrate having a drag reduction surface; the drag reduction surface includes large ribs and grooves with trapezoidal cross-sections arranged at intervals; small ribs with rectangular cross-sections are provided on both sides of the upper end surface of the large ribs; a superhydrophobic coating is coated on the surfaces of the small ribs, large ribs and grooves.

[0039] The grooves have a spacing of 240 - 360 μm, a groove width of 160 - 240 μm, and a groove depth of 120 μm.

[0040] The bottom of the groove has a porous shrub-like structure for reducing the contact area between the inside of the groove and the water flow.

[0041] A method for preparing a multi-scale wear-resistant superhydrophobic drag reduction surface includes the following steps:

[0042] Step 1: Preparation of small ribs, large ribs and grooves: The substrate is processed 16 times according to the pattern by using a pulsed laser with a laser frequency of 30 kHz, a pulse width of 1 μs, a processing speed of 500 mm / s, and a processing path line density of 0.025 mm; the processed substrate is cleaned;

[0043] Step 2: Preparation of the superhydrophobic coating emulsion: Octadecyltrichlorosilane and silica nanoparticles in a ratio of 1 mL:50 mg are mixed evenly and fully reacted;

[0044] Step 3: Preparation of the superhydrophobic coating spraying liquid: The superhydrophobic coating emulsion obtained in Step 2 is diluted and then ultrasonically dispersed;

[0045] Step 4: Preparation of the multi-scale wear-resistant superhydrophobic drag reduction surface: The superhydrophobic coating spraying liquid obtained in Step 3 is evenly sprayed onto the surfaces of the small ribs, large ribs and grooves obtained in Step 1, and then dried at room temperature to obtain the multi-scale wear-resistant superhydrophobic drag reduction surface.

[0046] The ultrasonic frequency in Step 3 is 40 kHz.

[0047] In Step 4, the spraying is carried out using a spray gun; the spray gun has a nozzle diameter of 0.3 mm, a spraying distance of 10 cm, a spraying time of 1 s, and a drying time of 24 h.

[0048] The substrate is a metallic material. This structure can be achieved by adjusting the laser parameters according to the material properties. Its strength depends on the characteristics of the substrate material. Different substrate materials can be used to adapt to different application scenarios, and it has strong scalability.

[0049] In Step 1, the morphology of the bottom of the groove can be controlled by controlling the laser path and line density to increase the pores. Refer to Figure 2 , when the laser path line density is 0.001, the material is heated with a relatively high density, and the material is almost completely melted and re-deposited, forming a granular stacked surface with almost no large pores formed; when the line density is 0.005, some material can be left between the paths, forming a relatively large number of random pore structures; when the line density is 0.025, a backbone-like structure is formed in the groove, and many small holes are scattered around. However, due to the too large line density, the melting degree of the central part of the groove is relatively low, and the morphology is relatively flat, which is not conducive to reducing the contact area with the water flow.

[0050] The number of processing times also has a great influence on the surface morphology. Refer to Figure 3 , when processing 4 times with the same laser parameters, due to the relatively low melting degree of the material at the bottom of the groove, a certain rough structure is formed on the surface, but it does not meet the requirements of the pore structure; when the number of times increases to 10 times, the surface pore structure gradually appears, and after 16 times, the pore structure is clearly visible and meets the requirements. The formation of this structure is due to multiple laser processing, and the material at the bottom of the groove is repeatedly ablated, forming a multi-scale structure with a large number of pores, and large ribs and small ribs are also formed simultaneously. Different from the ordinary nanostructures formed by lasers, this porous shrub-like structure with the coexistence of micron-scale large pores and nano-rough structures can greatly reduce the contact area between the inside of the groove and the water flow after being combined with the coating. This structure exists in the groove and will not be directly contacted with external solids and worn, which can ensure the integrity of the structure is not damaged and maintain the stability of drag reduction.

[0051] To solve the problem that the coating on the top of the ribs is relatively easy to wear, by adjusting the laser parameters, a protective structure of the coating is realized based on the substrate material. The high temperature of the laser melts the substrate material and reacts with oxygen in the air. Refer to Figures 4 - 6 , for example, when using an aluminum substrate, it melts and reacts with oxygen in the air to generate alumina. The hardness of alumina is higher than that of the aluminum sheet substrate, and it can be re-deposited on both sides to form a special structure, effectively protecting the coating between the top of the large ribs and the small ribs. When the coating covers the surface, the presence of the small ribs improves the mechanical wear resistance of the surface. When this surface has surface friction with other objects, the small-scale rib structure is harder and can resist mechanical wear, delaying the wear of the coating on the top of the large-scale ribs and delaying the failure of drag reduction. As Figure 13As shown, for the effect verification, referring to the experimental results of sandpaper polishing, within the initial polishing distance of 100 cm, the hydrophobicity of the grooved superhydrophobic surface remains almost unchanged.

[0052] To ensure that the prepared surface has practical significance, the above-prepared multi-scale wear-resistant superhydrophobic drag-reducing surface is subjected to drag reduction tests, underwater durability tests, and mechanical wear tests to examine its surface performance. The test procedures are as follows:

[0053] 1. Drag reduction experiment: Samples of the multi-scale wear-resistant superhydrophobic drag-reducing surface with dimensions of 10 cm × 10 cm × 1 mm and control samples of smooth aluminum plates are respectively placed on the drag reduction device for testing, and the resistance values of the surfaces are tested at a water flow impact speed of 2 - 5 m / s.

[0054] 2. A sample of the multi-scale wear-resistant superhydrophobic drag-reducing surface with dimensions of 3 cm × 3 cm × 1 mm is placed at the bottom of a beaker with a water depth of 10 cm, and the contact angle and sliding angle of the surface are recorded every 24 h to characterize the change in surface wettability.

[0055] 3. A sample of the multi-scale wear-resistant superhydrophobic drag-reducing surface with dimensions of 3 cm × 3 cm × 1 mm is fixed at the bottom of a 100 g weight and pulled uniformly on 1000-mesh sandpaper. Each 20 cm pull is counted as one wear cycle, and the change in the contact angle and sliding angle of the surface is tested once to characterize the surface wettability.

[0056] Example 1:

[0057] 1. Preparation of small ribs, large ribs, and grooves: Place the aluminum plate on the laser workbench, and process the substrate according to the pattern 16 times at a processing speed of 500 mm / s and a processing path line density of 0.025 mm with a pulsed laser having a laser frequency of 30 kHz and a pulse width of 1 μs according to the dimensions of groove spacing - groove width - groove depth: 300 - 160 - 120 μm. After processing, clean it in an ultrasonic cleaner for 10 min.

[0058] 2. Preparation of superhydrophobic coating emulsion: Sequentially load 1 mL of octadecyltrichlorosilane (OTS), 80 μl of deionized water, and 50 mg of silica nanoparticles into a glass bottle, mix them on a vortex mixer at a rotation speed of 3000 r / min for 10 s, and then let it stand for 2 h to wait for the reaction to complete.

[0059] 3. Preparation of superhydrophobic coating spraying liquid: Add the completely reacted emulsion obtained in step 2 to 20 mL of n-hexane for dilution, and then ultrasonically disperse it in an ultrasonic cleaner for 20 min.

[0060] 4. Preparation of multi-scale wear-resistant superhydrophobic drag-reducing surface: Spray the coating spraying liquid obtained in Step 3 onto the surfaces of the small ribs, large ribs, and grooves obtained in Step 1 evenly at a pressure of 25 Mpa and a distance of 10 cm from the sample using a spray gun, and dry the sprayed aluminum sheet at room temperature for 24 h to obtain a multi-scale wear-resistant superhydrophobic drag-reducing surface.

[0061] Example 2:

[0062] 1. Preparation of small ribs, large ribs, and grooves: Place the aluminum plate on the laser workbench, and process the substrate according to the pattern 16 times at a processing speed of 500 mm / s and a processing path line density of 0.025 mm with a pulsed laser having a laser frequency of 30 kHz and a pulse width of 1 μs according to the dimensions of groove spacing - groove width - groove depth: 300 - 200 - 120 μm. The processed sample is cleaned in an ultrasonic cleaner for 10 min.

[0063] 2. Preparation of superhydrophobic coating emulsion: Sequentially load 1 mL of octadecyltrichlorosilane (OTS), 80 μl of deionized water, and 50 mg of silica nanoparticles into a glass bottle, mix them on a vortex mixer at a rotation speed of 3000 r / min for 10 s, and then let it stand for 2 h until the reaction is completed.

[0064] 3. Preparation of superhydrophobic coating spraying liquid: Add 20 mL of n-hexane to dilute the emulsion that has completed the reaction obtained in Step 2, and then ultrasonically disperse it in an ultrasonic cleaner for 20 min.

[0065] 4. Preparation of multi-scale wear-resistant superhydrophobic drag-reducing surface: Spray the coating spraying liquid obtained in Step 3 onto the surfaces of the small ribs, large ribs, and grooves obtained in Step 1 evenly at a pressure of 25 Mpa and a distance of 10 cm from the sample using a spray gun, and dry the sprayed aluminum sheet at room temperature for 24 h to obtain a multi-scale wear-resistant superhydrophobic drag-reducing surface.

[0066] Example 3:

[0067] 1. Preparation of small ribs, large ribs, and grooves: Place the aluminum plate on the laser workbench, and process the substrate according to the pattern 16 times at a processing speed of 500 mm / s and a processing path line density of 0.025 mm with a pulsed laser having a laser frequency of 30 kHz and a pulse width of 1 μs according to the dimensions of groove spacing - groove width - groove depth: 300 - 240 - 120 μm. The processed sample is cleaned in an ultrasonic cleaner for 10 min.

[0068] 2. Preparation of superhydrophobic coating emulsion: Sequentially load 1 mL of octadecyltrichlorosilane (OTS), 80 μl of deionized water, and 50 mg of silica nanoparticles into a glass bottle, mix them on a vortex mixer at a rotation speed of 3000 r / min for 10 s, and then let it stand for 2 h until the reaction is completed.

[0069] 3. Preparation of superhydrophobic coating spraying liquid: Add 20 mL of n-hexane to dilute the emulsion with complete reaction obtained in Step 2, and then ultrasonically disperse it in an ultrasonic cleaner for 20 min.

[0070] 4. Preparation of multi-scale wear-resistant superhydrophobic and drag-reducing surface: Spray the coating spraying liquid obtained in Step 3 evenly onto the surfaces of small ribs, large ribs and grooves obtained in Step 1 through a spray gun at a pressure of 25 Mpa and a distance of 10 cm from the sample. After drying the sprayed aluminum sheet at room temperature for 24 h, a multi-scale wear-resistant superhydrophobic and drag-reducing surface is obtained.

[0071] Example 4:

[0072] 1. Preparation of small ribs, large ribs and grooves: Place the aluminum plate on the laser workbench. According to the dimensions of groove spacing - groove width - groove depth: 240 - 200 - 120 μm, use a pulsed laser with a laser frequency of 30 kHz and a pulse width of 1 μs to process the substrate 16 times at a processing speed of 500 mm / s and a processing path line density of 0.025 mm according to the pattern. The processed sample is cleaned in an ultrasonic cleaner for 10 min.

[0073] 2. Preparation of superhydrophobic coating emulsion: Sequentially load 1 mL of octadecyltrichlorosilane (OTS), 80 μl of deionized water and 50 mg of silica nanoparticles into a glass bottle, mix them on a vortex mixer at a rotation speed of 3000 r / min for 10 s, and then let it stand for 2 h until the reaction is complete.

[0074] 3. Preparation of superhydrophobic coating spraying liquid: Add 20 mL of n-hexane to dilute the emulsion with complete reaction obtained in Step 2, and then ultrasonically disperse it in an ultrasonic cleaner for 20 min.

[0075] 4. Preparation of multi-scale wear-resistant superhydrophobic and drag-reducing surface: Spray the coating spraying liquid obtained in Step 3 evenly onto the surfaces of small ribs, large ribs and grooves obtained in Step 1 through a spray gun at a pressure of 25 Mpa and a distance of 10 cm from the sample. After drying the sprayed aluminum sheet at room temperature for 24 h, a multi-scale wear-resistant superhydrophobic and drag-reducing surface is obtained.

[0076] Example 5:

[0077] 1. Preparation of small ribs, large ribs and grooves: Place the aluminum plate on the laser workbench. According to the dimensions of groove spacing - groove width - groove depth: 360 - 200 - 120 μm, use a pulsed laser with a laser frequency of 30 kHz and a pulse width of 1 μs to process the substrate 16 times at a processing speed of 500 mm / s and a processing path line density of 0.025 mm according to the pattern. The processed sample is cleaned in an ultrasonic cleaner for 10 min.

[0078] 2. Preparation of superhydrophobic coating emulsion: 1 mL of octadecyltrichlorosilane (OTS), 80 μL of deionized water, and 50 mg of silica nanoparticles were successively loaded into a glass bottle, mixed, and then mixed on a vortex mixer at a speed of 3000 r / min for 10 s, and then left standing for 2 h to wait for the reaction to complete.

[0079] 3. Preparation of superhydrophobic coating spraying solution: The emulsion with complete reaction obtained in step 2 was added with 20 mL of n-hexane for dilution, and then ultrasonically dispersed in an ultrasonic cleaner for 20 min.

[0080] 4. Preparation of multi-scale wear-resistant superhydrophobic drag reduction surface: The coating spraying solution obtained in step 3 was evenly sprayed onto the surfaces of small ribs, large ribs, and grooves obtained in step 1 through a spray gun at a pressure of 25 Mpa and a distance of 10 cm from the sample. The sprayed aluminum sheet was dried at room temperature for 24 h to obtain a multi-scale wear-resistant superhydrophobic drag reduction surface.

[0081] Example 6:

[0082] 1. Preparation of superhydrophobic coating emulsion: 1 mL of octadecyltrichlorosilane (OTS), 80 μL of deionized water, and 50 mg of silica nanoparticles were successively loaded into a glass bottle, mixed, and then mixed on a vortex mixer at a speed of 3000 r / min for 10 s, and then left standing for 2 h to wait for the reaction to complete.

[0083] 2. Preparation of superhydrophobic coating spraying solution: The emulsion with complete reaction obtained in step 2 was added with 20 mL of n-hexane for dilution, and then ultrasonically dispersed in an ultrasonic cleaner for 20 min.

[0084] 3. Preparation of multi-scale wear-resistant superhydrophobic drag reduction surface: The coating spraying solution obtained in step 3 was evenly sprayed onto a smooth aluminum plate through a spray gun at a pressure of 25 Mpa and a distance of 10 cm from the sample. The sprayed aluminum plate was dried at room temperature for 24 h to obtain a multi-scale wear-resistant superhydrophobic drag reduction surface.

[0085] The multi-scale wear-resistant superhydrophobic drag reduction surfaces and smooth aluminum plates prepared in Examples 1, 2, 3, 4, 5, and 6 were respectively placed on Figure 8 the shown drag reduction device for testing, and the drag resistance value of the surface was tested at a water flow impact speed of 2 - 5 m / s. From Figure 9 the test results, it can be seen that the multi-scale wear-resistant superhydrophobic drag reduction surface with dimensions of 300 - 200 - 120 μm has the highest drag reduction efficiency. The drag reduction rate can reach 70% under the low-speed flow state of 2 m / s, and the drag reduction rate can reach 66% under the high-speed flow state of 5 m / s.

[0086] The multi-scale wear-resistant superhydrophobic drag reduction surfaces prepared in Examples 1 and 6 were used to test the underwater durability of the surface by using Figure 10 the shown device. From Figure 11From the experimental results, it can be seen that this surface can maintain superhydrophobicity underwater for more than 50 h.

[0087] Take the multi-scale wear-resistant superhydrophobic drag-reducing surfaces prepared in Examples 1 and 6, and use the Figure 12 device shown to test the mechanical wear resistance of the surface. From Figure 13 the experimental results, it can be seen that the superhydrophobicity of the ordinary coating surface is lost after being polished with 240 cm sandpaper, while the superhydrophobic groove structure can withstand the polishing of 520 cm sandpaper.

[0088] In summary, the preparation method of the present invention is simple, easy to implement and has good effects. The types and amounts of reagents for preparing the superhydrophobic coating are few, and the reagents can be simply mixed and reacted, and the preparation process is simple. The preparation of the multi-scale wear-resistant superhydrophobic drag-reducing surface is simple and the processing speed is relatively fast. As Figure 7 shown, the contact angle reaches 157°, the sliding angle <1°, and the superhydrophobic performance is good. And a high drag reduction efficiency can be achieved under various flow states. The drag reduction rate of the water drag reduction surface prepared by this method can reach 70% under the low-speed flow state of 2 m / s, which is 7% higher than that of the simple coating surface in terms of drag reduction efficiency. Under the high-speed water impact speed of 5 m / s, a high drag reduction rate of 66% is achieved compared with the smooth aluminum plate. The drag reduction efficiency is 20% higher than that of the simple coating surface.

[0089] The multi-scale wear-resistant superhydrophobic drag-reducing surface prepared by the method of the present invention has good mechanical wear resistance. The superhydrophobicity of the ordinary coating surface is lost after being polished with 240 cm sandpaper, while the multi-scale groove structure can withstand the polishing of 520 cm sandpaper. It has good underwater durability. This surface can maintain superhydrophobicity underwater for more than 50 h.

[0090] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A multi-scale wear-resistant superhydrophobic drag-reducing surface, characterized in that: Comprising: A substrate having a drag-reducing surface; the drag-reducing surface includes large ribs (1) with a trapezoidal cross-section and grooves (4) arranged at intervals; small ribs (2) with a rectangular cross-section are provided on both sides of the upper end surface of the large ribs (1); a superhydrophobic coating (3) coated on the surfaces of the small ribs (2), large ribs (1) and grooves (4); the multi-scale wear-resistant superhydrophobic drag-reducing surface is prepared according to the following method: Step 1: Preparation of small ribs (2), large ribs (1) and grooves (4): The substrate is processed 16 times according to the pattern by using pulsed laser with a laser frequency of 30 kHz, a pulse width of 1 μs, a processing speed of 500 mm / s, and a processing path line density of 0.025 mm; the processed substrate is cleaned; Step 2: Preparation of the superhydrophobic coating (3) emulsion: Octadecyltrichlorosilane and silica nanoparticles in a ratio of 1 mL:50 mg are mixed evenly and fully reacted; Step 3: Preparation of the superhydrophobic coating (3) spraying liquid: The superhydrophobic coating (3) emulsion obtained in Step 2 is diluted and then ultrasonically dispersed; Step 4: Preparation of the multi-scale wear-resistant superhydrophobic drag-reducing surface: The superhydrophobic coating (3) spraying liquid obtained in Step 3 is evenly sprayed onto the surfaces of the small ribs (2), large ribs (1) and grooves (4) obtained in Step 1, and then dried at room temperature to obtain the multi-scale wear-resistant superhydrophobic drag-reducing surface.

2. The multi-scale wear-resistant superhydrophobic drag-reducing surface according to claim 1, characterized in that: The grooves (4) have a spacing of 240 - 360 μm, a groove (4) width of 160 - 240 μm, and a groove (4) depth of 120 μm.

3. The multi-scale wear-resistant superhydrophobic drag-reducing surface according to claim 2, characterized in that: The bottom of the groove (4) has a porous shrub-like structure.

4. The multi-scale wear-resistant superhydrophobic drag reduction surface according to claim 1, wherein: The ultrasonic frequency in Step 3 is 40 kHz.

5. A multi-scale wear-resistant superhydrophobic drag-reducing surface according to claim 1, characterized in that: In Step 4, the spraying is carried out by using a spray gun; the spray gun orifice diameter is 0.3 mm, the spraying distance is 10 cm, the spraying time is 1 s, and the drying time is 24 h.

6. The multi-scale wear-resistant superhydrophobic drag reduction surface according to claim 1, characterized in that: The substrate is a metal material.

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