A method for preparing a laser-induced extreme wettability pattern on a magnesium alloy surface

Abstract

The application discloses a kind of based on laser induction's magnesium alloy surface extreme wettability pattern preparation method, the method is as follows: (1) magnesium alloy sample is polished, ultrasonic cleaning and drying;(2) nanosecond laser processing system is used, and grid-shaped microgroove structure is prepared on magnesium alloy surface;(3) the sample after laser etching is immersed in stearic acid ethanol solution, and is sealed in hydrothermal reaction kettle together and is carried out modification reaction;(4) after modification reaction is completed, sample is removed and is washed with anhydrous ethanol sufficiently to remove surface residual reagent, then dry;(5) again using nanosecond laser processing system, in magnesium alloy surface not etched remaining part or pre-set hydrophilic pattern area carries out the etching of secondary grid-shaped microgroove structure.This method uses "laser direct writing-whole chemical modification-laser secondary ablation" mask-free processing strategy, can realize high stability, high contrast extreme wettability pattern customization on magnesium alloy surface.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering and relates to a method for preparing heterogeneous wettability patterns, specifically a method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser-induced wettability patterns. Background Technology

[0002] Magnesium alloys, due to their low density, high specific strength, and excellent electromagnetic shielding performance, have shown great application potential in high-end outdoor equipment such as 5G communication base station housings. However, magnesium alloys are chemically reactive and prone to electrochemical corrosion, and easily accumulate moisture and ice in complex outdoor environments, severely limiting their service life and reliability. In recent years, constructing superhydrophobic surfaces through surface engineering technology has become an effective way to improve their corrosion and ice resistance. However, with the upgrading of industrial demands, a single superhydrophobic surface is no longer sufficient to meet the multifunctional coupling requirements of complex scenarios. In cutting-edge applications such as localized heat dissipation and corrosion protection synergy, microfluidic directional manipulation, and water collection, it is often required that the material surface possess regional extreme wettability differences (i.e., the coexistence of superhydrophobic and superhydrophilic patterns). Currently, traditional methods for preparing heterogeneous wettability patterns mostly rely on photolithography, mask etching, or complex multi-step chemical deposition, which have drawbacks such as cumbersome processes, high costs, and poor flexibility, making it difficult to achieve efficient and high-precision pattern customization on reactive magnesium alloy substrates. Therefore, there is an urgent need to develop a flexible, controllable processing technology with a short preparation cycle to rapidly construct high-quality extreme wettability contrast surfaces on magnesium alloy surfaces. Summary of the Invention

[0003] To overcome the shortcomings of existing heterogeneous wettability pattern preparation technologies, such as cumbersome processes, high costs, and poor flexibility, this invention provides a laser-induced method for preparing extreme wettability patterns on magnesium alloy surfaces. This method employs a maskless processing strategy of "laser direct writing - overall chemical modification - laser secondary ablation," which can efficiently and flexibly construct extreme wettability contrast surfaces on magnesium alloy surfaces with precise coexistence of superhydrophobic and superhydrophilic regions, achieving highly stable and high-contrast customized extreme wettability patterns.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser-induced methods includes the following steps:

[0006] Step (1) Grind, ultrasonically clean and dry the magnesium alloy sample;

[0007] Step (2) A nanosecond laser processing system is used to prepare a grid-like microgroove structure on the pre-designed patterned geometric area on the magnesium alloy surface. The laser scanning parameters are: laser power 15~20W, scanning speed 100~150mm / s, number of scans 130~160, and scanning spacing 60~100μm.

[0008] Step (3) Stearic acid is used as a low surface energy modifier. It is added to anhydrous ethanol to prepare a stearic acid ethanol solution with a concentration of 0.5~1.5 mol / L. The laser-etched sample is immersed in the solution and sealed in a hydrothermal reactor for modification reaction. The reaction temperature is controlled at 60~80℃ and the time is 5~8 hours.

[0009] After the modification reaction in step (4) is completed, the sample is taken out and rinsed thoroughly with anhydrous ethanol to remove residual reagents on the surface. Then it is placed in a vacuum drying oven to dry, thus completing the construction of the overall superhydrophobic surface. The drying temperature is controlled at 80~100℃ and the time is 0.5~1.5 hours.

[0010] Step (5) Again, the nanosecond laser processing system is used to perform secondary mesh-like microgroove etching on the remaining part of the magnesium alloy surface that has not been etched in step (2) or the preset hydrophilic pattern area. While the high-energy laser beam ablates the micro-morphology, it removes the stearic acid low surface energy modification layer on the surface of the area, exposing the fresh magnesium alloy substrate with extremely hydrophilic properties, thus forming a strong extreme wettability contrast with the surrounding superhydrophobic areas.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] (1) It abandons the traditional process that relies heavily on complex photomasks and uses nanosecond laser technology to design and quickly switch pattern shapes and sizes on magnesium alloy surfaces with high precision.

[0013] (2) Using cheap and non-toxic stearic acid to replace traditional expensive and potentially toxic fluorinated modifiers, combined with conventional hydrothermal reactions, significantly reduces raw material costs and conforms to the trend of green manufacturing.

[0014] (3) An innovative three-step method of “local etching - overall modification - secondary local etching” is adopted. The secondary laser processing simultaneously realizes the induction of superhydrophilic micro-nano structures and the peeling off of the modification layer, eliminating the cumbersome shielding steps and greatly shortening the preparation cycle. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of laser induction.

[0016] Figure 2 Flowchart for the preparation of patterns with extreme wettability;

[0017] Figure 3 It is an extremely wettable pattern. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0019] This invention provides a method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser-induced methods, such as... Figure 1 and Figure 2 As shown, the specific implementation steps are as follows:

[0020] Step (1) Grind, ultrasonically clean and dry the magnesium alloy sample.

[0021] Step (2) employs a nanosecond laser processing system to fabricate a mesh-like microgroove structure in a specific region on the magnesium alloy surface. This specific region is a pre-designed patterned geometric area based on actual application requirements. The laser scanning parameters were determined using a machine learning optimization method, and the optimized parameters were: laser power 17.03W, scanning speed 134.15mm / s, number of scans 148, and scanning spacing 80μm. The mesh-like microgroove structure etched in this step provides a micro-nano rough structure, which, combined with subsequent low surface energy modification, constitutes the superhydrophobic background region in the final wettability pattern.

[0022] Step (3) After inducing the surface micro / nano structure, stearic acid was used as a low surface energy modifier. Stearic acid powder was added to anhydrous ethanol and stirred continuously under heating using a magnetic stirrer to prepare a stearic acid-ethanol solution with a concentration of 0.5 mol / L. The laser-etched sample was immersed in this solution and sealed together in a hydrothermal reactor, then placed in an oven and heated at 70°C for 6 hours.

[0023] After the modification reaction in step (4) is completed, the sample is taken out and rinsed thoroughly with anhydrous ethanol to remove residual reagents on the surface. Then it is placed in a vacuum drying oven and dried at 80°C for 1 hour to complete the construction of the overall superhydrophobic surface.

[0024] Step (5) again uses a nanosecond laser processing system to perform secondary mesh-like microgroove etching on the remaining parts of the magnesium alloy surface that were not etched in step (2) (or the pre-defined hydrophilic pattern area). While ablates the micro-morphology, the high-energy laser beam removes the stearic acid low surface energy modification layer on the surface of this area, exposing a fresh substrate with extremely high hydrophilicity. This creates a strong contrast in extreme wettability with the surrounding superhydrophobic areas, forming the superhydrophilic background area in the final wettability pattern.

[0025] The surface of the prepared sample is as follows Figure 3 As shown.

Claims

1. A method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser-induced methods, characterized in that... The method includes the following steps: Step (1) Grind, ultrasonically clean and dry the magnesium alloy sample; Step (2) A nanosecond laser processing system is used to prepare a grid-like microgroove structure on a pre-designed patterned geometric region on the surface of the magnesium alloy; Step (3) Stearic acid is used as a low surface energy modifier. It is added to anhydrous ethanol to prepare a stearic acid ethanol solution. The laser-etched sample is immersed in the solution and sealed in a hydrothermal reactor for modification reaction. After the modification reaction in step (4) is completed, the sample is taken out and rinsed thoroughly with anhydrous ethanol to remove residual reagents on the surface. Then it is placed in a vacuum drying oven to dry, thus completing the construction of the overall superhydrophobic surface. Step (5) Again, using the nanosecond laser processing system, a secondary mesh-like microgroove structure is etched on the remaining part of the magnesium alloy surface that has not been etched in step (2) or the preset hydrophilic pattern area.

2. The method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser induction according to claim 1, characterized in that... In step (2), the laser scanning parameters are: laser power 15~20W, scanning speed 100~150mm / s, number of scans 130~160, and scanning interval 60~100μm.

3. The method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser induction according to claim 1, characterized in that... In step (3), the concentration of stearic acid ethanol solution is 0.5~1.5 mol / L.

4. The method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser induction according to claim 1, characterized in that... In step (3), the temperature of the modification reaction is 60~80℃ and the time is 5~8 hours.

5. The method for preparing extreme wettability patterns on magnesium alloy surfaces based on laser-induced methods according to claim 1, characterized in that... In step (4), the drying temperature is 80~100℃ and the time is 0.5~1.5 hours.

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