Fabrication Of Micro/nanostructure Arrays On Filmed Metal Surface By Femtosecond Laser And Thermal Oxidation

In the past decades,surfaces with hierarchical micro/nanostructures have been widely studied and fabricated for their extensive applications in self-cleaning,anti-reflection,anti-corrosion and oil-water separation.The superhydrophobicity,self-cleaning and anti-reflection are the focuses of the researches of hierarchical micro/nanostructures.The superhydrophobic surface is defined as a surface with a water contact angle greater than150°and a sliding angle less than 10°.It was found that these hierarchical micro/nanostructures with superhydrophobic and self-cleaning performance is mainly due to“lotus effect”.“Lotus effect”mains that the lotus leaf surface with micro/nanostructures can achieve self-cleaning effect.When water drop on the lotus leaves,the water can absorb the dust on the leaves and slide out.Inspired by nature,researchers study many hierarchical micro/nanostructures that are similar to lotus leaf,to achieve a fabricated superhydrophobic and self-cleaning surface.Many studies have shown that the roughness,the free energy and the morphology of micro/nanostructures affect the wettability of such surfaces.Femtosecond laser is an important tool for fabricating micro/nanostructures.Femtosecond laser ablation can achieve selectively controlled processing of patterned micro/nanostructures.The traditional chemical methods have the advantages of simplicity,high efficiency and low cost.In this thesis,we combined the femtosecond laser and the chemical thermal oxidation and fabricated some hierarchical micro/nanostructures with superhydrophobicity,self-cleaning and anti-reflection.The main work and innovation of this thesis are as follows:(1)The femtosecond laser ablation and the thermal oxidation growth are combined to fabricate the hierarchical micro/nanostructures.The femtosecond laser can realize high precision machining,more importantly,it can achieve a wide variety of patterned fabrication.In this thesis,we have fabricated three kinds of large-area array patterns by femtosecond laser.They are dot array,line array and grid array.All the arrays have been synthesized of micro/nanostructures through thermal oxidation.Without femtosecond laser ablation,only thermal oxidation has difficult to control the morphology of micro/nanostructures.By combining femtosecond laser and thermal oxidation,the patterned surface of array structures can be synthesized.(2)The surfaces of the line array have shown the best performance of superhydrophobicity,self-cleaning and antireflection.At laser fluence of 0.6 J/cm~2,the line array surface has the maximum contact angle of 152°,exhibited superhydrophobicity without chemical modification.After silanization,the contact angle was further increased to160.5°and the roll angle was less than 1.7°,showing a self-cleaning effect.In addition,antireflection properties with a minimum reflectance of less than 1%at wavelength range of700-800 nm can be achieved and the total reflectance can be steadily below 6%over a broad wavelength range of 600-1150 nm.