Research On Durability Of Hydrophobic Copper Surfaces Prepared By Laser Shock Imprinting

Hydrophobic surfaces have many excellent properties,so they have always attracted extensive interest and attention in the industry.However,before the hydrophobic surface can be practically applied on a large scale,how to efficiently and cost-effectively fabricate a well-hydrophobic workpiece surface and how to solve the problems of the durability of the hydrophobic surface to meet the daily application standards are still important challenges.In this paper,the surface of hydrophobic copper foil with multi-level groove microtexture was prepared by laser shock imprinting technology.First,a micro-mold with multi-level groove features is prepared by laser marking,and then the multi-level groove micro-texture on the micro-mold is copied to the workpiece surface by laser shock imprinting technology.The durability of the hydrophobic copper surface was systematically studied from the perspectives of the workpiece microtexture and surface element composition.The main research work and results can be obtained as follows:(1)The basic theory of laser shock imprinting process was studied in depth,the experimental platform of laser shock imprinting was constructed,and the experimental equipment and characterization methods were introduced.The experimental methods for testing the surface wettability and durability of workpieces are mainly introduced.The preparation of the sample and the design and manufacture of the micro-mold are introduced,and the forming process and surface micro-morphology of the micro-mold surface under the action of laser marking are emphatically described.The results show that the micro-texture forming effect of the grooves on the surface of the micro-mold is remarkable.(2)The surface of hydrophobic copper foil with multi-level groove microtexture was prepared by laser shock imprinting process.The effects of impact times,laser energy,soft film thickness,workpiece thickness and ablation thickness on the surface morphology and contact angle of the hydrophobic surface were studied.The results show that when the number of impacts increases from 1 to 7,the laser energy increases from 565 mJ to 1690 mJ,the soft film thickness decreases from 300 μm to100 μm,and the workpiece thickness decreases from 150 μm to 80 μm.The degree of replicating microtexture on the surface of the workpiece gradually increases,the forming depth of the workpiece increases,and the forming effect becomes better.At the same time,after the workpiece is imprinted by laser shock,the groove micro-texture produces a large number of secondary fine-grained micro-texture,so that the contact area between the solid surface and the air increases in the total area ratio,the surface contact angle increases,and the groove micro-texture surface change from hydrophilic to hydrophobic.When the thickness of the pure aluminum foil ablation layer is 40 μm,no breakdown occurs,indicating that the process has certain reliability.In addition,the workpiece can well replicate the micro-features of the micro-mold groove,and the surface forming effect of the workpiece is remarkable.It reflects the advantages of laser shock imprinting process.(3)The durability of the hydrophobic copper surface prepared by the laser shock imprinting process was systematically studied by observing the micro-textured surface morphology of the workpiece and measuring the element composition.In the research of wear resistance,solid particle impact resistance and peeling resistance,the micro-scale groove micro-protrusions have a protective effect on the tiny particles and flocs attached to the groove micro-structure,which makes the groove micro-woven The degree of structural damage was limited,and the surface remained hydrophobic after 9 cycles of abrasion,15 min of solid particle impact,and 100 cycles of tape peeling.The hydrophobic surface of the workpiece has good wear resistance,solid particle impact resistance and peeling resistance.The hydrophobic surface prepared by this process has excellent durability.(4)In the research of water drop impact resistance,aging properties,acid resistance and alkali resistance,it was found that the micro-texture of the grooves on the surface of the workpiece was damaged.Because the surface of the workpiece was imprinted by laser shock,the grains were refined and the mechanical properties were improved.The ability to resist corrosion damage is improved,so its hydrophobicity is reduced but the effect is limited.Therefore,after the hydrophobic surface was placed in the water droplet impact environment for 60 h,the surface was still hydrophobic after 21 days in air,water and 3.5% NaCl solution,and 24 h in pH=2 HCl solution and pH=12 NaOH solution.In the fluorination modification experiment,it was found that while reducing the surface energy of the workpiece,stable molecular films(SAMs)were formed on the surface,that is,there were coral-like or leaf-like protruding micro-textures on the groove surface,which enhanced the rough structure of the surface.Enhanced surface hydrophobicity.At the same time,the molecular film itself is chemically inert,which can protect the micro-textured surface of the groove and enhance its resistance to corrosion damage,so the final surface is still hydrophobic.It shows that the hydrophobic surface prepared by this process has good durability.