Abradable durable type composite anti-drag surface

Abstract

The invention relates to the technical field of ocean engineering underwater equipment and advanced manufacturing, in particular to an abradable durable composite drag reduction surface which comprises an abrasion-resistant framework, array electrodes and an isolation layer. The wear-resistant framework is of a porous framework structure and is used as an anode; the array electrode is arranged below the wear-resistant framework and serves as a cathode, and microbubbles are generated through an electrolytic reaction; the isolation layer is arranged between the array electrode and the wear-resistant framework and is used for performing electric insulation isolation on the cathode and the anode; the wear-resistant framework, the array electrode and the isolating layer are of a three-dimensional composite structure in the direction perpendicular to the surface, and the surface of the three-dimensional composite structure is coated with a super-hydrophobic coating. According to the technical scheme, the continuous drag reduction effect under the abradable condition is achieved, and the durability of the drag reduction surface in the underwater service environment is remarkably improved.

Description

Technical Field

[0001] This invention relates to the technical field of marine engineering underwater equipment and advanced manufacturing, and in particular to a wear-resistant and durable composite drag-reducing surface. Background Technology

[0002] The magnitude of drag on underwater equipment directly determines its maneuverability, combat effectiveness, and energy consumption. Therefore, drag reduction and efficiency improvement are crucial factors that must be considered in the design and manufacturing of underwater equipment. The total drag of an underwater vehicle during navigation mainly consists of frictional drag and form drag. Form drag is primarily related to the vehicle's shape and can be optimized by improving the body lines design; however, due to constraints such as overall layout, the potential for improvement is relatively limited. Frictional drag is mainly determined by the wetted surface area of ​​the hull, surface roughness, the surrounding fluid medium, and its flow characteristics. It accounts for a large proportion at low speeds, generally reaching 70%–80% of the total drag; at high speeds, frictional drag accounts for approximately 40% of the total drag.

[0003] Superhydrophobic surfaces have significant applications in underwater drag reduction, corrosion prevention, and antifouling. Superhydrophobic surfaces are typically created by constructing micro / nano structures on the material surface using micro / nano fabrication or chemical etching methods, followed by treatment with low surface energy materials to achieve the superhydrophobic effect. During underwater immersion, the microstructures and residual gases within them prevent water from entering the microstructures, reducing the actual contact area between the water and the surface, thus achieving drag reduction. However, in actual service conditions, water pressure and flow velocity can cause water to enter the microstructures, leading to the transition from the Cassie state to the Wenzel state, increasing the contact area between the water and the surface, and resulting in the loss of superhydrophobic properties. Furthermore, mechanical actions such as impacts and scratches can damage the low surface energy materials and microstructures, causing the superhydrophobic surface to fail. Currently, superhydrophobic materials generally suffer from low mechanical strength, poor wear resistance, and insufficient stability, making them easily damaged during actual service and limiting their practical applications.

[0004] Chinese patent CN202310784088.X discloses a microstructure of a drag-reducing functional surface and its forming method. This technical solution includes a substrate, a microbubble generating component disposed on the substrate, and a hydrophobic layer. The microbubble generating component generates microbubbles through electrolysis of water using electrodes. The hydrophobic layer is a micro / nano structure, a hydrophobic coating, or a combination of both. This technical solution combines trench microstructures, superhydrophobic micro / nano structures, and microbubble drag reduction technology. It generates continuous microbubbles through in-situ electrolysis of seawater using an electrode array, and utilizes the microgrooves and superhydrophobic micro / nano structures to trap the microbubbles, extending their residence time and thus achieving drag reduction. However, in this technical solution, the superhydrophobic layer is only disposed on the outer surface of the substrate. When the surface wears down, the superhydrophobic functional layer is quickly removed, leading to a significant decrease in surface drag reduction performance and making it difficult to meet the durability requirements for long-term service. Summary of the Invention

[0005] In view of this, the present invention proposes a wearable and durable composite drag-reducing surface to solve the technical problem that the surface functional layer of the superhydrophobic drag-reducing surface fails rapidly and the drag-reducing performance degrades due to mechanical wear during long-term service in the prior art.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a wear-resistant and durable composite drag-reducing surface, the composite drag-reducing surface comprising a wear-resistant skeleton, an array electrode and an isolation layer; The wear-resistant skeleton has a porous skeleton structure and serves as the anode. The array electrode is disposed below the wear-resistant skeleton and serves as the cathode, generating microbubbles through an electrolytic reaction. The isolation layer is disposed between the array electrode and the wear-resistant skeleton to provide electrical insulation and isolation between the cathode and the anode; The wear-resistant skeleton, array electrodes, and isolation layer form a three-dimensional composite structure in the direction perpendicular to the surface, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0007] This invention achieves a synergistic effect of microbubble drag reduction and superhydrophobic drag reduction by constructing a three-dimensional composite structure of a wear-resistant skeleton, an array electrode, and an isolation layer, and coating the surface with a superhydrophobic coating. The wear-resistant skeleton uses a porous titanium alloy structure as the anode, possessing high strength and wear resistance, effectively protecting the internal structure. The array electrode, acting as the cathode, is positioned below the skeleton and continuously generates microbubbles through an electrolytic reaction. These microbubbles rise to the surface through the porous skeleton, interacting with the superhydrophobic coating to form a stable gas film layer, reducing the actual contact area between the water and the surface, thereby significantly reducing frictional resistance. The isolation layer provides electrical insulation between the cathode and anode, preventing short circuits and ensuring the stable conduct of the electrolytic reaction. Because the components form a three-dimensional composite structure in the vertical direction, when the surface wears, the newly exposed cross-section retains the same structural composition and functional configuration, allowing the worn surface to still possess superhydrophobic properties and electrolytic gas generation capability. This achieves continuous drag reduction under wear-prone conditions, solving the technical problem of rapid failure of traditional superhydrophobic drag-reducing surfaces due to mechanical wear during underwater service, and significantly improving the durability and reliability of drag-reducing surfaces under actual working conditions.

[0008] Based on the above technical solutions, preferably, the wear-resistant skeleton is a titanium alloy, the array electrode is a copper electrode, the isolation layer is an insulating material, and the superhydrophobic filler is a modified nano-silica composite PDMS filler.

[0009] More preferably, the wear-resistant skeleton and array electrodes can be fabricated using 3D printing or additive manufacturing methods. Based on the above technical solutions, preferably, the wear-resistant skeleton surface is deposited with a ruthenium-iridium coating.

[0010] Based on the above technical solutions, preferably, the isolation layer is polyimide or polytetrafluoroethylene.

[0011] Based on the above technical solutions, preferably, the method for preparing the superhydrophobic coating includes: S1. Mix nano-silica and mercaptosilane coupling agent in anhydrous toluene and react at 80-100℃ for 6-8 hours to obtain mercaptosilica. S2. Disperse mercapto-modified silica in an aqueous ethanol solution, add 3-mercaptopropionic acid, adjust the pH of the solution to 8-9, add an aqueous hydrogen peroxide solution under nitrogen protection, and react for 4-6 hours to obtain composite silica. S3. Disperse the composite silica in anhydrous DMF, add EDC and NHS, activate at 25-27℃ for 0.5-1h, add perfluorodecylamine, and react at 30-40℃ for 12-24h to obtain modified nano silica. S4. Disperse the modified nano-silica in the PDMS prepolymer, add crosslinking agent and catalyst, mix thoroughly and coat it on the surface of the superhydrophobic coating, and cure at 80-120℃ for 2-4 hours to form a superhydrophobic coating.

[0012] Specifically, in step S1, thiol groups are introduced onto the surface of nano-silica via silane coupling reaction, which enhances the surface activity of the nanoparticles and provides reaction sites for subsequent modification. In step S2, thiolized silica and 3-mercaptopropionic acid are linked by hydrogen peroxide under alkaline conditions to form disulfide bonds (-SS-), constructing a reversible and flexible molecular bridge. At the same time, carboxyl groups (-COOH) are introduced onto the surface of the nanoparticles. This disulfide bond structure can undergo reversible breakage and recombination under mechanical stress, improving the toughness and self-healing potential of the coating. In step S3, long-chain perfluoroalkyl groups are grafted onto the surface of the nanoparticles using an amidation reaction, which significantly reduces the surface energy and endows the coating with excellent hydrophobic and oleophobic properties. In step S4, the modified nano-silica is uniformly dispersed in PDMS prepolymer and cured into a film through the action of crosslinking agents and catalysts. The modified nanoparticles not only act as reinforcing fillers to improve the mechanical strength and wear resistance of the coating, but also construct a micro-nano rough structure on the surface, which works synergistically with the low surface energy fluorinated chains to form a stable superhydrophobic surface. The above technical solution significantly improves the dispersibility and interfacial compatibility of nanofillers in the PDMS matrix through surface chemical modification, enhances the mechanical properties and superhydrophobic stability of the coating, and enables the coating to maintain good drag reduction performance during wear.

[0013] Based on the above technical solutions, preferably, in step S1, the mass ratio of nano-silica to mercaptosilane coupling agent is 1:0.15-0.3, and the mercaptosilane coupling agent is 3-mercaptopropyltrimethoxysilane or 3-mercaptopropyltriethoxysilane.

[0014] Based on the above technical solution, preferably, in step S2, the mass ratio of mercaptosilica, 3-mercaptopropionic acid and hydrogen peroxide aqueous solution is 1:(0.2-0.5):(0.3-0.8), and the mass percentage of hydrogen peroxide aqueous solution is 25-35%.

[0015] Based on the above technical solutions, preferably, in step S3, the mass ratio of composite silica to EDC is 1:(0.15-0.3), the mass ratio of NHS to EDC is 1:1-1.2, and the mass ratio of perfluorodecylamine to composite silica is 1:(0.15-0.25).

[0016] Based on the above technical solution, preferably, in step S4, the mass ratio of modified nano-silica to PDMS prepolymer is 1:2-5, the amount of crosslinking agent added is 3-10% of the mass of PDMS prepolymer, the amount of catalyst added is 1-2% of the mass of crosslinking agent, the crosslinking agent is tetraethyl orthosilicate, and the catalyst is dibutyltin dilaurate. The PDMS prepolymer is preferably hydroxyl-terminated polydimethylsiloxane.

[0017] Based on the above technical solutions, preferably, the wear-resistant skeleton, array electrode and isolation layer are formed by interlayer interface bonding or insertion.

[0018] In this invention, the wear-resistant skeleton, array electrodes, and isolation layer are bonded together at the interlayer interface or inserted into a three-dimensional composite structure, which realizes the rapid assembly and stable connection of each functional layer. This assembly method facilitates the independent preparation and modular production of each functional layer, significantly reducing manufacturing difficulty and cost. At the same time, it allows for layer-by-layer replacement and maintenance when the structure is damaged or the performance degrades, improving the practicality and economy of the composite drag-reducing surface.

[0019] The wear-resistant and durable composite drag-reducing surface of the present invention has the following advantages over the prior art: (1) This invention constructs a three-dimensional composite structure in the vertical direction by constructing a wear-resistant skeleton, an array electrode, and an isolation layer, and coats the surface with a superhydrophobic coating, thereby achieving the synergistic effect of electrolytic gas generation drag reduction and superhydrophobic drag reduction. When the surface wears, since each functional layer penetrates the entire thickness of the structure in the vertical direction, the newly exposed cross section still maintains the same composition configuration and functional characteristics, so that the worn surface still has the ability to generate gas through electrolysis and superhydrophobic properties. This solves the technical problem of rapid failure of traditional superhydrophobic drag reduction surfaces due to surface wear, achieves continuous drag reduction effect under wearable conditions, and significantly improves the durability of drag reduction surfaces in underwater service environments.

[0020] (2) The present invention uses porous titanium alloy as wear-resistant skeleton. This material has high strength, high wear resistance and corrosion resistance, and can effectively resist water flow erosion and sand collision, reducing the wear rate of superhydrophobic coating. At the same time, the porous structure provides an upward channel for microbubbles generated by array electrodes. After the microbubbles reach the surface through the porous skeleton, they interact with the superhydrophobic coating to form a stable gas film layer, which enhances the stability of the underwater superhydrophobic state, delays the transformation of Cassie state to Wenzel state, and ensures the long-term effectiveness of drag-reducing surface under high water pressure and dynamic flow field environment.

[0021] (3) The superhydrophobic coating of the present invention is prepared by a multi-step chemical modification method. Through thiolization, carboxylation and fluorination modification, thiol groups, disulfide bonds, carboxyl groups and perfluoroalkyl chains are sequentially introduced on the surface of nano-silica, which significantly improves the interfacial compatibility and dispersibility between the nanofiller and the PDMS matrix. The introduction of disulfide bonds endows the coating with a certain degree of flexibility and self-adaptation, and improves the toughness of the coating under stress conditions; the grafting of perfluoroalkyl chains greatly reduces the surface energy and enhances the hydrophobic and oleophobic properties; the modified nanofiller, as a reinforcing phase, improves the mechanical strength and wear resistance of the coating, so that the superhydrophobic coating can still maintain a good surface micro-nano structure and low surface energy characteristics during wear, thus extending the service life of the coating.

[0022] (4) The present invention uses interlayer interface bonding or insertion combination to assemble each functional layer. This method is simple to operate, does not require complex process equipment, facilitates the independent preparation and modular production of each functional layer, and reduces manufacturing costs and maintenance difficulty. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the wear-resistant and durable composite drag-reducing surface array electrode layer in an embodiment of the present invention; Figure 2 This is a schematic diagram of a wear-resistant and durable composite drag-reducing surface isolation layer in an embodiment of the present invention; Figure 3 This is a schematic diagram of the wear-resistant skeleton of the wear-resistant composite drag-reducing surface in an embodiment of the present invention; Figure 4 This is a schematic diagram of a wear-resistant, durable composite drag-reducing superhydrophobic coating for a surface in an embodiment of the present invention. Figure 5 This is a schematic diagram of the wear-resistant and durable composite drag-reducing surface installation in an embodiment of the present invention; Figure 6 This is a schematic diagram of a wear-resistant and durable composite drag-reducing surface in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that in this embodiment, the particle size of the nano-silica is 20 nm, the PDMS prepolymer is hydroxyl-terminated polydimethylsiloxane with a molecular weight of 15,000-25,000 g / mol and a hydroxyl content of 0.08-0.12 mmol / g.

[0027] Example 1 like Figures 1-6 As shown, this embodiment discloses a wear-resistant and durable composite drag-reducing surface, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, array electrode, and isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0028] Methods for preparing superhydrophobic coatings include: S1. Mix 100g of nano-silica and 22g of 3-mercaptopropyltrimethoxysilane in 500ml of anhydrous toluene. Under nitrogen protection, react at 90℃ for 7h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), and dry it under vacuum with anhydrous toluene and anhydrous ethanol in sequence to obtain mercaptolated silica. S2. Disperse 100g of mercapto-modified silica in 800ml of ethanol-water solution (ethanol to water volume ratio of 1:1), sonicate, add 35g of 3-mercaptopropionic acid, adjust the pH of the solution to 8.5, add 55g of 30% hydrogen peroxide aqueous solution under nitrogen protection, and react at 23℃ for 5h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with deionized water until neutral, then wash with anhydrous ethanol, and vacuum dry to obtain composite silica. S3. 100g of composite silica was dispersed in 600ml of anhydrous DMF and ultrasonically dispersed. 22g of EDC and 20g of NHS were added and activated at 23℃ for 0.8h. 20g of perfluorodecylamine was added and reacted at 35℃ for 18h. After the reaction was completed, the mixture was centrifuged (8000rpm, 10min), washed successively with anhydrous DMF and anhydrous ethanol, and vacuum dried to obtain modified nano silica. S4. Disperse 100g of modified nano-silica in 350g of PDMS prepolymer, ultrasonically disperse, add 28g of tetraethyl orthosilicate and 6g of dibutyltin dilaurate, mix thoroughly, degas under vacuum for 20min to remove air bubbles, and uniformly coat the mixture onto the surface of the three-dimensional composite structure by spraying, with a coating thickness of about 200μm. Cure at 100℃ for 3h to form a superhydrophobic coating.

[0029] Example 2 This embodiment discloses a wear-resistant and durable composite drag-reducing surface, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, array electrode, and isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0030] Methods for preparing superhydrophobic coatings include: S1. Mix 100g of nano-silica and 15g of 3-mercaptopropyltrimethoxysilane in 500ml of anhydrous toluene. Under nitrogen protection, react at 80℃ for 8h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), and dry it under vacuum with anhydrous toluene and anhydrous ethanol in sequence to obtain mercaptolated silica. S2. Disperse 100g of mercapto-modified silica in 800ml of ethanol-water solution (ethanol to water volume ratio of 1:1), ultrasonically disperse, add 20g of 3-mercaptopropionic acid, adjust the pH of the solution to 8, add 30g of 30% hydrogen peroxide aqueous solution under nitrogen protection, and react at 20℃ for 6h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with deionized water until neutral, then wash with anhydrous ethanol, and vacuum dry to obtain composite silica. S3. Disperse 100g of composite silica in 600ml of anhydrous DMF, sonicate, add 15g of EDC and 15g of NHS, activate at 20℃ for 1h, add 15g of perfluorodecylamine, react at 30℃ for 24h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with anhydrous DMF and anhydrous ethanol in sequence, and vacuum dry to obtain modified nano silica. S4. Disperse 100g of modified nano-silica in 200g of PDMS prepolymer, ultrasonically disperse, add 6g of tetraethyl orthosilicate and 1g of dibutyltin dilaurate, mix thoroughly, degas under vacuum for 20min to remove air bubbles, and uniformly coat the mixture onto the surface of the three-dimensional composite structure by spraying, with a coating thickness of about 200μm. Cure at 80℃ for 4h to form a superhydrophobic coating.

[0031] Example 3 This embodiment discloses a wear-resistant and durable composite drag-reducing surface, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, array electrode, and isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0032] Methods for preparing superhydrophobic coatings include: S1. Mix 100g of nano-silica and 30g of 3-mercaptopropyltrimethoxysilane in 500ml of anhydrous toluene. Under nitrogen protection, react at 100℃ for 6h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), and dry it under vacuum with anhydrous toluene and anhydrous ethanol in sequence to obtain mercaptolated silica. S2. Disperse 100g of mercapto-modified silica in 800ml of ethanol-water solution (ethanol to water volume ratio of 1:1), sonicate, add 50g of 3-mercaptopropionic acid, adjust the pH of the solution to 9, add 80g of 30% hydrogen peroxide aqueous solution under nitrogen protection, and react at 25℃ for 4h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with deionized water until neutral, then wash with anhydrous ethanol, and vacuum dry to obtain composite silica. S3. Disperse 100g of composite silica in 600ml of anhydrous DMF, sonicate, add 30g of EDC and 25g of NHS, activate at 25℃ for 0.5h, add 25g of perfluorodecylamine, react at 40℃ for 12h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with anhydrous DMF and anhydrous ethanol in sequence, and vacuum dry to obtain modified nano silica. S4. Disperse 100g of modified nano-silica in 500g of PDMS prepolymer, ultrasonically disperse, add 50g of tetraethyl orthosilicate and 10g of dibutyltin dilaurate, mix thoroughly, degas under vacuum for 20min to remove air bubbles, and uniformly coat the mixture onto the surface of the three-dimensional composite structure using a spraying method. The coating thickness is about 200μm. Cure at 120℃ for 2h to form a superhydrophobic coating.

[0033] Comparative Example 1 This comparative example discloses a composite drag-reducing surface, comprising an array electrode, an isolation layer, a wear-resistant substrate, and a superhydrophobic coating. The array electrode is made of copper, the isolation layer is made of polyimide, and the wear-resistant substrate is a dense titanium alloy plate (non-porous structure) with a ruthenium-iridium coating deposited on its surface. Each layer is bonded at an interlayer interface to form a planar stacked structure, and the outermost surface is coated with a superhydrophobic coating. The preparation method of the superhydrophobic coating is the same as in Example 1.

[0034] Comparative Example 2 This comparative example discloses a composite drag-reducing surface, whose three-dimensional composite structure is the same as that of Example 1, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, the array electrode, and the isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0035] The preparation method of the superhydrophobic coating is as follows: 100g of nano-silica is directly dispersed in 350g of PDMS prepolymer and ultrasonically dispersed. 28g of tetraethyl orthosilicate and 6g of dibutyltin dilaurate are added and mixed thoroughly. Vacuum degassing is performed for 20min to remove air bubbles. The mixture is then uniformly coated onto the surface of the three-dimensional composite structure by spraying. The coating thickness is about 200μm. The coating is cured at 100℃ for 3h to form a superhydrophobic coating.

[0036] Comparative Example 3 This comparative example discloses a composite drag-reducing surface, whose three-dimensional composite structure is the same as that of Example 1, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, the array electrode, and the isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0037] Methods for preparing superhydrophobic coatings include: S1. Mix 100g of nano-silica and 22g of 3-mercaptopropyltrimethoxysilane in 500ml of anhydrous toluene. Under nitrogen protection, react at 90℃ for 7h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash it with anhydrous toluene and anhydrous ethanol in sequence, and dry it under vacuum to obtain mercapto-modified silica. S2. 100g of mercapto-modified silica was dispersed in 600ml of anhydrous DMF and ultrasonically dispersed. 22g of EDC and 20g of NHS were added and activated at 23℃ for 0.8h. 20g of perfluorodecylamine was added and reacted at 35℃ for 18h. After the reaction was completed, the mixture was centrifuged (8000rpm, 10min), washed successively with anhydrous DMF and anhydrous ethanol, and vacuum dried to obtain modified nano silica. S3. Disperse 100g of modified nano-silica in 350g of PDMS prepolymer, ultrasonically disperse, add 28g of tetraethyl orthosilicate and 6g of dibutyltin dilaurate, mix thoroughly, degas under vacuum for 20min to remove air bubbles, and uniformly coat the mixture onto the surface of the three-dimensional composite structure by spraying, with a coating thickness of about 200μm. Cure at 100℃ for 3h to form a superhydrophobic coating.

[0038] Comparative Example 4 This comparative example discloses a composite drag-reducing surface, whose three-dimensional composite structure is the same as that of Example 1, including a wear-resistant skeleton, an array electrode, and an isolation layer. The wear-resistant skeleton is a porous skeleton structure made of titanium alloy with a ruthenium-iridium coating deposited on the surface. The array electrode is made of copper, and the isolation layer is made of polyimide. The wear-resistant skeleton, the array electrode, and the isolation layer are connected to form a three-dimensional composite structure, and the surface of the three-dimensional composite structure is coated with a superhydrophobic coating.

[0039] Methods for preparing superhydrophobic coatings include: S1. Mix 100g of nano-silica and 22g of 3-mercaptopropyltrimethoxysilane in 500ml of anhydrous toluene. Under nitrogen protection, react at 90℃ for 7h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash it with anhydrous toluene and anhydrous ethanol in sequence, and dry it under vacuum to obtain mercapto-modified silica. S2. Disperse 100g of mercapto-modified silica in 800ml of ethanol-water solution (ethanol to water volume ratio of 1:1), sonicate, add 35g of 3-mercaptopropionic acid, adjust the pH of the solution to 8.5, add 55g of 30% hydrogen peroxide aqueous solution under nitrogen protection, and react at 23℃ for 5h. After the reaction is complete, centrifuge the mixture (8000rpm, 10min), wash with deionized water until neutral, then wash with anhydrous ethanol, and vacuum dry to obtain composite silica. S3. Disperse 100g of composite silica directly in 350g of PDMS prepolymer, ultrasonically disperse, add 28g of tetraethyl orthosilicate and 6g of dibutyltin dilaurate, mix thoroughly, degas under vacuum for 20min to remove air bubbles, and uniformly coat the mixture onto the surface of the three-dimensional composite structure using a spraying method. The coating thickness is about 200μm. Cure at 100℃ for 3h to form a superhydrophobic coating.

[0040] Performance testing The composite drag-reducing surface samples prepared in the examples and comparative examples were used to measure the static contact angle and roll-off angle of the sample surface using a contact angle measuring instrument (JC2000D). The samples were placed in a high-pressure water environment simulation device with water pressures set to 0.5MPa, 1.0MPa, 1.5MPa and 2.0MPa, respectively. After maintaining each pressure condition for 2 hours, the samples were taken out and the contact angle change was measured to evaluate the durability.

[0041] The sand-containing water flow impact wear test was carried out on the samples at various impact angles using a multiphase flow erosion corrosion tester. The impact angle settings in the multiphase flow erosion corrosion tester included 0°, 30°, 45°, 60° and 90°. After the test, the mass loss rate of each sample was measured by weighing method, and the average value was taken. The wear resistance of the samples was evaluated by the mass loss rate.

[0042] The drag reduction performance of the samples was evaluated using a rotating disk drag reduction test device. The sample (100mm in diameter) was fixed on the surface of the rotating disk and immersed in a sealed water tank (500mm × 500mm × 600mm, water depth 500mm, water temperature controlled at 25±2℃). The torque T required for disk rotation at different speeds was measured using a torque sensor. A polished aluminum alloy disk was used as the reference sample. The drag reduction rate was calculated using the following formula:

[0043] DR(%) = (T0-T1) / T0 × 100% Where DR is the drag reduction ratio, T0 is the torque of the reference sample, and T1 is the torque of the test sample. Each sample was tested three times at each rotational speed, and the average value was taken. The test results are shown in Table 1.

[0044] Table 1 As shown in Table 1, the composite drag-reducing surface prepared by the technical solution of the present invention has good superhydrophobic properties, drag reduction effect, and wear resistance. Comparative Example 1, lacking a three-dimensional composite structure, only exposes a dense titanium alloy matrix after wear, lacking the functional configuration of array electrodes, isolation layer, and porous channels. It cannot continue to generate microbubbles, and after losing the superhydrophobic coating, the surface becomes hydrophilic, resulting in increased mass loss and a significant decrease in drag reduction after wear. Comparative Example 2, with its unmodified nano-silica surface containing abundant silanol groups, is hydrophilic and easily aggregates in the hydrophobic PDMS matrix, exhibiting poor interfacial compatibility and uneven dispersion. This leads to a significant reduction in the hydrophobicity, durability, wear resistance, and drag reduction performance of the composite drag-reducing surface. Comparative Example 3 lacks carboxyl groups as activation grafting points, significantly reducing the grafting rate between perfluorodecylamine and the filler surface, resulting in insufficient hydrophobic modification. Furthermore, the lack of the flexibility and self-adaptive ability provided by the disulfide bond structure reduces the coating toughness, making it prone to cracking under stress, thus lowering various properties. In Comparative Example 4, the lack of fluorination modification resulted in insufficient reduction of surface energy. At the same time, the insufficient hydrophobicity made it difficult for microbubbles to adhere stably to the surface and form an effective gas film layer. The combined effect of electrolytic gas generation and superhydrophobic drag reduction was significantly weakened.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An abradable, durable, composite drag-reducing surface, characterized by: The composite drag reduction surface comprises a wear-resistant framework, an array electrode and an isolation layer; The wear-resistant framework is a porous framework structure and serves as an anode; The array electrode is arranged below the wear-resistant framework and serves as a cathode to generate micro-bubbles through electrolytic reaction; The isolation layer is arranged between the array electrode and the wear-resistant framework to electrically insulate the cathode and the anode; The wear-resistant framework, the array electrode and the isolation layer form a three-dimensional composite structure in a direction perpendicular to the surface, and the surface of the three-dimensional composite structure is coated with a super-hydrophobic coating.

2. A durable abradable composite drag reducing surface as in claim 1 wherein: The wear-resistant framework is made of titanium alloy, the array electrode is a copper electrode, the isolation layer is made of insulating material, and the super-hydrophobic filler is a modified nano-silica composite PDMS filler.

3. A durable abradable composite drag reducing surface as claimed in claim 2 wherein: The surface of the wear-resistant framework is deposited with a ruthenium-iridium coating.

4. A durable abradable composite drag reducing surface as defined in claim 2, wherein: The isolation layer is made of polyimide or polytetrafluoroethylene.

5. A durable abradable composite drag reducing surface as defined in claim 2, wherein: The preparation method of the super-hydrophobic coating comprises: S1. Mixing nano-silica and mercapto silane coupling agent in anhydrous toluene, and reacting at 80-100°C for 6-8h to obtain mercapto-silica; S2. Dispersing the mercapto-silica in an ethanol aqueous solution, adding 3-mercaptopropionic acid, adjusting the pH of the solution to 8-9, adding hydrogen peroxide aqueous solution under nitrogen protection, and reacting for 4-6h to obtain composite silica; S3. Dispersing the composite silica in anhydrous DMF, adding EDC and NHS, activating at 25-27°C for 0.5-1h, adding perfluorodecylamine, and reacting at 30-40°C for 12-24h to obtain modified nano-silica; S4. Dispersing the modified nano-silica in a PDMS prepolymer, adding a crosslinking agent and a catalyst, mixing thoroughly, coating on the surface of the super-hydrophobic coating, and curing at 80-120°C for 2-4h to form a super-hydrophobic coating.

6. A durable abradable composite drag reducing surface as claimed in claim 5 wherein: In step S1, the mass ratio of nano-silica to mercapto silane coupling agent is 1:0.15-0.

3.

7. An abradable, durable, composite drag reducing surface as defined in claim 5, wherein: In step S2, the mass ratio of mercapto-silica, 3-mercaptopropionic acid and hydrogen peroxide aqueous solution is 1:(0.2-0.5):(0.3-0.8), and the mass percentage of hydrogen peroxide aqueous solution is 25-35%.

8. A durable abradable composite drag reducing surface as defined in claim 5, wherein: In step S3, the mass ratio of composite silica to EDC is 1:(0.15-0.3), the mass ratio of NHS to EDC is 1:1-1.2, and the mass ratio of perfluorodecylamine to composite silica is 1:(0.15-0.25).

9. An abradable, durable, composite drag-reducing surface as defined in claim 5, wherein: In step S4, the mass ratio of modified nano-silica to PDMS prepolymer is 1:2-5, the amount of crosslinking agent added is 3-10% of the mass of PDMS, the amount of catalyst added is 1-2% of the mass of the crosslinking agent, the crosslinking agent is tetraethyl orthosilicate, and the catalyst is dibutyltin dilaurate.

10. An abradable, durable, composite drag reducing surface as in claim 1, wherein: The wear-resistant framework, the array electrode and the isolation layer are formed by interlayer interface bonding or plug-in combination.

Images