Comparative Study Of Laser Etching And Laser Shock Imprinting For The Preparation Of Hydrophobic Titanium Foil Surfaces

The booming development of modern bionics has driven the rapid development of material surface functionalization.Among them,superhydrophobic surfaces inspired by the special wettability of animal and plant surfaces have shown promising applications in the fields of self-cleaning,corrosion resistance,water harvesting,anti-icing,drag reduction,and droplet sorting,which have attracted the close attention of many scholars.However,at present,these artificially prepared surfaces generally suffer from a lack of durability and are severely tested in practical applications.In this dissertation,TA1 pure titanium,which is widely used in aerospace,chemical and medical fields,is the object of study.Using the thermal and force effects of laser,the groove-like micro-nano textures with hydrophobic properties was simply and efficiently prepared on the surface of titanium foil with a thickness of 20μm using laser etching and laser shock imprinting processes,respectively.It is found that the surface prepared by laser impact imprinting has better durability than that by laser etching,so this study can be helpful for the preparation and improvement of the surface micro-nano textures.In the experiments of laser etching and laser shock imprinting for the preparation of grooved micro-nano fabrics,the process parameters in the laser etching process were first investigated and optimized.The etching depth of the grooves was found to be positively correlated with the power,pulse width,and pulse frequency,and negatively correlated with the scanning speed.From the overall trend,the hydrophobicity of the surface becomes stronger as the array grooves on the surface of the titanium foil are etched to a greater depth,and the hydrophobicity of the surface stabilizes after the depth is greater than 8.9μm,with a maximum contact angle of150°.According to the effect of etching depth on surface wettability,the same groove structure was etched on the surface of 1 mm thick titanium plate with laser power of4.4 W,pulse width of 20 ns,pulse frequency of 100 k Hz,scanning speed of 1000mm/s,and scanning times of 4 times as process parameters to provide a mold for the subsequent impact embossing process.In the experiments of laser shock imprinting for the preparation of surface micro-nano textures,the forming depth of the grooves was positively correlated with the number of pulses and the power density.Among them,the first three impacts have a greater impact on the degree of deformation of the workpiece,and the surface structure of the mold can be completely replicated when the power density reaches 1.461×109 W/cm²,at which the surface contact angle is126°.Based on the above-mentioned two processes prepared surface unfolding aging and durability studies,and to explore the main reasons for the differences.In the ageing study,the surfaces of both processes were stored in air,and the laser-etched surfaces showed a superhydrophilic state within 12 hours,and reached a superhydrophobic state and stabilized after 30 days.In contrast,no significant aging phenomenon was found on the surface of the laser shock imprinting samples.In the durability study,the same test conditions were used to compare the durability of the surfaces of both processes.The results showed that the surface prepared by laser impact imprinting had better wear resistance,impact resistance,and UV resistance.Laser shock imprinting has the effect of refining the grain size and increasing the surface hardness of the material,which can improve the mechanical stability of the micro-nano textures,and has almost no oxidation effect on the surface of the workpiece,so there is no obvious Ti O₂photocatalytic reaction,thus improving the UV resistance of the surface.