Functionalized bionic super-hydrophilic anti-drag ceramic membrane and preparation method thereof

Abstract

The invention discloses a functionalized bionic super-hydrophilic anti-drag ceramic membrane and a preparation method thereof, and belongs to the technical field of surface engineering and functional materials. Through a five-component synergistic system (calcium acetate, EDTA disodium, monopotassium phosphate, graphite powder and lauryl sodium sulfate), in-situ codeposition of hydroxyapatite (a hydrophilic phase) and graphite (a drag reduction phase) is realized. According to the invention, the problem of single-function electrolyte (such as a corrosion-resistant system only containing phosphorus salt and a hole sealing system only containing alkali) is solved, a hydrophilic-drag reduction function phase is prepared, and the prepared ceramic membrane has wide application in the fields of drag reduction, self-cleaning, antifouling, antifogging, oil-water separation and the like due to excellent hydrophilic and oleophobic properties.

Description

Technical Field

[0001] This invention discloses a functionalized biomimetic superhydrophilic drag-reducing ceramic membrane and its preparation method, belonging to the field of surface engineering and functional materials technology. Background Technology

[0002] In recent years, plasma electrolytic oxidation technology has attracted increasing attention in the field of surface treatment of metal materials such as aluminum, magnesium, and titanium. Researchers have conducted extensive research on electrolyte system optimization, process parameter control, coating formation mechanism, and performance improvement. For example, in terms of electrolyte systems, research has progressed from traditional silicate and phosphate single-component systems to multi-component composite systems and modified systems with the addition of rare earth elements and nanoparticles.

[0003] In nature, the dermal scutes of shark skin and the mucus on fish surfaces have been observed to provide excellent drag reduction underwater. Research has revealed that this is primarily due to the construction of micro / nano structures and the regulation of surface wettability, both working together to create a superhydrophilic surface. This results in a dense water film on the surface, thus achieving drag reduction. However, most existing research on coatings focuses only on drag reduction or superhydrophilicity as a single function, lacking research on the synergistic mechanism. Furthermore, biomimetic microstructures are susceptible to mechanical wear and chemical corrosion, leading to a significantly reduced lifespan. Therefore, finding a simple method to prepare biomimetic superhydrophilic composite functional coatings for efficient and durable underwater drag reduction is particularly urgent. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a functionalized biomimetic superhydrophilic drag-reducing micro-arc oxidation ceramic membrane. Through biomimetic electrolyte formulation design, plasma electrolytic oxidation process parameter optimization and post-treatment enhancement, a ceramic membrane with a micro-nano porous structure containing hydrophilic and drag-reducing functional phases is formed on the surface of a metal substrate, thereby achieving a synergistic improvement in superhydrophilic performance and drag-reducing performance. Moreover, the membrane layer is firmly bonded to the substrate and has strong stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A functionalized biomimetic superhydrophilic drag-reducing ceramic membrane and its preparation method, comprising the following steps: 1. Matrix pretreatment Select titanium alloy, aluminum alloy, or magnesium alloy as the metal matrix and cut the sample to a predetermined size. Drill holes on the edge of the sample for suspension. Dry grind the sample surface stepwise with sandpaper of 240 grit, 400 grit, 600 grit, 800 grit, and 1200 grit until there are no obvious scratches and the roughness Ra ≤ 0.8 μm. Place the ground sample in anhydrous ethanol and ultrasonically degrease it for 20-25 min in an ultrasonic cleaner. Remove the degreased sample and place it in a sodium hydroxide solution with a concentration of 0.6-1.2 g / L. Alkali wash it at 30-50℃ for 10-20 min. Rinse the sample repeatedly with deionized water until there is no residual agent on the surface. Dry it at 50-80℃ for 10-30 min and set aside. 2. Preparation of biomimetic electrolyte Using deionized water as a solvent, add the following components sequentially and stir until completely dissolved / dispersed: calcium electrolyte 0.1-0.2 mol / L calcium acetate; complexing agent 0.01-0.05 mol / L disodium EDTA; phosphorus electrolyte 0.01-0.05 mol / L potassium dihydrogen phosphate; drag-reducing functional phase 2-10 g / graphite powder; surfactant 0.5-1.0 g / L sodium dodecyl sulfate; after preparation, place the electrolyte in an ultrasonic oscillator and vibrate for 10-30 min to ensure uniform suspension of graphite powder, and control the pH of the electrolyte to 6-8; 3. Plasma electrolytic oxidation treatment Using the pretreated metal sample as the anode and the stainless steel plate as the cathode, the two electrodes are placed parallel to each other in the electrolyte bath, ensuring the sample is completely submerged. The circulating cooling system is started to control the electrolyte temperature at 25-50℃. Plasma electrolytic oxidation is performed using a pulsed DC power supply, with the following process parameters set: voltage: 300-480V; duty cycle: 35%-45%; frequency: 500-800Hz; current density: 0.02-0.06A / cm²; oxidation time: 30-45min. During the oxidation process, the electrolyte is continuously stirred at a stirring rate of 150-200r / min to ensure uniform electrolyte composition and avoid excessively high local concentrations. 4. Post-processing After plasma electrolytic oxidation, the sample is immediately removed and rinsed with flowing deionized water to remove residual electrolyte until the rinsing solution is neutral. The sample is then placed in an autoclave, and deionized water is added as the hydrothermal medium. The temperature inside the autoclave is controlled at 100-150℃, and the hydrothermal treatment time is 1-5 hours. After the hydrothermal treatment is completed, the sample is removed and dried at 50-110℃ for 30-60 minutes to obtain a functionalized biomimetic superhydrophilic drag-reducing ceramic membrane.

[0006] Compared with the prior art, the present invention has the following advantages: 1. The biomimetic electrolyte of this invention innovatively combines calcium-phosphorus electrolyte with graphite powder and surfactant. During the plasma electrolytic oxidation process, the calcium-phosphorus component generates hydroxyapatite in situ. The graphite powder is incorporated into the film layer as a drag-reducing component. The surfactant promotes the dispersion of each component and optimizes the morphology of the film layer, thus realizing the synergistic design of "hydrophilic functional phase - drag-reducing functional phase - biomimetic structure". 2. The prepared ceramic membrane has a micro-nano porous structure with a porosity of 15%-30% and a surface contact angle ≤20°. It has superhydrophilic properties, and the porous structure can store water to form a "water film lubrication layer". Combined with the friction-reducing effect of the graphite phase, the friction coefficient of the membrane layer is reduced to below 0.2, and the drag reduction effect is significant. 3. The entire preparation process does not require high-temperature sintering or toxic reagents. The electrolyte can be recycled, making it green and environmentally friendly. The process steps are simple and highly controllable, making it suitable for industrial mass production. Attached Figure Description

[0007] Figure 1 Scanning electron microscope image of a titanium alloy-based functionalized biomimetic superhydrophilic drag-reducing ceramic membrane. Detailed Implementation

[0008] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0009] Example 1: Preparation of Functionalized Biomimetic Superhydrophilic Drag-Reducing Ceramic Membranes on Titanium Alloy Substrates 1. Matrix pretreatment: TC4 titanium alloy was selected as the matrix, and the sample was cut into 20mm×20mm×2mm pieces with holes drilled at the edges; it was then dry-ground with 240-grit, 400-grit, 600-grit, 800-grit, and 1200-grit sandpaper until the surface was free of scratches (Ra=0.8μm); it was then ultrasonically degreased in anhydrous ethanol for 25 min; it was then placed in a 1.2g / L sodium hydroxide solution and alkaline washed at 45℃ for 15 min; after rinsing with deionized water, it was dried at 80℃ for 25 min. 2. Preparation of biomimetic electrolyte: Using deionized water as solvent, add 0.15 mol / L calcium acetate, 0.02 mol / L potassium dihydrogen phosphate, 0.03 mol / L disodium EDTA, 6 g / L graphite powder, and 0.8 g / L sodium dodecyl sulfate. After stirring and dissolving, sonicate for 20 min. The pH is 6.5. 3. Plasma electrolytic oxidation treatment: The anode is a TC4 titanium alloy sample, and the cathode is a stainless steel plate; the electrolyte temperature is controlled at 35℃ by circulating cooling; the pulsed DC power supply parameters are: voltage 400V, duty cycle 35%, frequency 600Hz, current density 0.02A / cm², oxidation time 30min; the electrolyte is stirred at 150r / min during the oxidation process. 4. Post-treatment enhancement: Rinse the sample with deionized water until the rinsing solution is neutral; place it in an autoclave and perform hydrothermal treatment at 150°C for 2 hours; dry at 90°C for 30 minutes to obtain a ceramic membrane.

[0010] Performance testing The performance of the ceramic membrane prepared in Example 1 was tested: Surface contact angle: Tested using a contact angle meter, the contact angle is 20°, exhibiting superhydrophilic properties; Friction coefficient: Tested using a ball-and-disc friction and wear tester, the friction coefficient is 0.15; like Figure 1 As shown, isotropic sheet-like supramolecular structures are distributed on the surface of the ceramic film, and the isotropic sheet-like supramolecular structures are uniformly distributed.

[0011] Example 2: Preparation of functional biomimetic superhydrophilic drag-reducing ceramic membranes on aluminum alloy substrates 1. Substrate pretreatment: 2A12 aluminum alloy was selected as the substrate, with dimensions of 20mm×20mm×2mm; it was dry-ground sequentially with 240-grit, 400-grit, 600-grit, 800-grit, and 1200-grit sandpaper until the surface was free of scratches (Ra=0.7μm); it was then ultrasonically degreased in anhydrous ethanol for 25 minutes; it was then placed in a 1.0g / L sodium hydroxide solution and alkaline washed at 50℃ for 20 minutes; after rinsing with deionized water, it was dried at 60℃ for 30 minutes. 2. Preparation of biomimetic electrolyte: 0.18 mol / L calcium acetate, 0.05 mol / L potassium dihydrogen phosphate, 0.05 mol / L disodium EDTA, 7 g / L graphite powder, 1.0 g / L sodium dodecyl sulfate, ultrasonically vibrated for 25 min, pH=8; 3. Plasma electrolytic oxidation treatment: voltage 480V, duty cycle 40%, frequency 700Hz, current density 0.05A / cm², oxidation time 55min; electrolyte temperature 30℃, stirring rate 200r / min; 4. Post-treatment strengthening: hydrothermal treatment at 150℃ for 5 hours; drying at 100℃ for 25 minutes to obtain ceramic membrane.

[0012] Performance testing The performance of the ceramic membrane prepared in Example 1 was tested: Surface contact angle: Tested using a contact angle meter, the contact angle is 18°, exhibiting superhydrophilic properties; Friction coefficient: Tested using a ball-and-disc friction and wear tester, the friction coefficient is 0.17.

Claims

1. A functionalized biomimetic superhydrophilic drag-reducing ceramic membrane and its preparation method, comprising the following steps: (1) Substrate pretreatment: The metal substrate is mechanically polished, alkaline degreasing, alkaline activation, and deionized water rinsing in sequence to obtain a clean and activated substrate surface; (2) Preparation of biomimetic electrolyte: Using deionized water as solvent, add the following components in sequence and stir until completely dissolved / dispersed: calcium electrolyte 0.1-0.2 mol / L calcium acetate; complexing agent 0.01-0.05 mol / L disodium EDTA; phosphorus electrolyte 0.01-0.05 mol / L potassium dihydrogen phosphate; drag-reducing functional phase 2-10 g / graphite powder; surfactant 0.5-1.0 g / L sodium dodecyl sulfate; after preparation, place the electrolyte in an ultrasonic oscillator and oscillate for 10-30 min to ensure that the graphite powder is uniformly suspended, and control the pH value of the electrolyte to 6-8; (3) Plasma electrolytic oxidation treatment: The pretreated metal sample is used as the anode and the stainless steel plate is used as the cathode. The two electrodes are placed in parallel in the electrolyte tank to ensure that the sample is completely immersed. The circulating cooling system is started to control the electrolyte temperature at 25-50℃. The plasma electrolytic oxidation is carried out using a pulsed DC power supply. The process parameters are set as follows: voltage: 300-480V. Duty cycle: 35%-45%; Frequency: 500-800Hz; Current density: 0.02-0.06A / cm²; Oxidation time: 30-45min; During the oxidation process, the electrolyte is continuously stirred at a stirring rate of 150-200r / min to ensure uniform electrolyte composition and avoid excessively high local concentrations. (4) After the post-treatment plasma electrolytic oxidation is completed, the sample is taken out immediately and the surface residual electrolyte is rinsed with flowing deionized water until the rinsing solution is neutral. The sample is placed in an autoclave, and deionized water is added as a hydrothermal medium. The temperature inside the autoclave is controlled at 100-150℃ and the hydrothermal treatment time is 1-5h. After the hydrothermal treatment is completed, the sample is taken out and dried at 50-110℃ for 30-60min to obtain a functionalized biomimetic superhydrophilic drag-reducing ceramic membrane.

2. The preparation method according to claim 1, characterized in that, In step (1): Select titanium alloy, aluminum alloy or magnesium alloy as the metal matrix, cut the sample to the preset size, and drill holes on the edge of the sample for suspension; use 240 mesh, 400 mesh, 600 mesh, 800 mesh and 1200 mesh sandpaper to dry grind the sample surface step by step until there are no obvious scratches on the surface and the roughness Ra≤0.8μm; put the ground sample into anhydrous ethanol and ultrasonically degrease it in an ultrasonic cleaner for 20-25min; take out the degreased sample and put it into a sodium hydroxide solution with a concentration of 0.6-1.2g / L, and alkaline wash it at 30-50℃ for 10-20min; rinse the sample repeatedly with deionized water until there is no residual agent on the surface, and dry it at 50-80℃ for 10-30min for later use.

3. The process parameters according to claim 1, characterized in that, Voltage 380-460V; duty cycle 35%-45%; frequency 600-800Hz; current density 0.02-0.04A / cm²; oxidation time 35-55min.

4. The functionalized biomimetic superhydrophilic drag-reducing ceramic membrane according to claim 1, characterized in that, The ceramic membrane has a micro-nano porous structure with a porosity of 15%-30% and a surface contact angle of ≤20°. It has superhydrophilic properties, and the porous structure can store water to form a "water film lubrication layer". Combined with the friction-reducing effect of the graphite phase, the coefficient of friction of the ceramic membrane layer is ≤0.2, and the drag reduction effect is significant.

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