| Through the preparation of micro-nano scale structures on the surface of materials,various extraordinary surface properties can be obtained,which greatly promotes the development of technology and people’s production.In this study,femtosecond laser micro-nano processing technology was used to induce and scan the surface of metal materials to prepare micro-nano scale structures with different morphologies.The corresponding relationship between laser processing parameters and structure morphology were explored,and the formation mechanism of different structures was analyzed.At the same time,Zn O crystal nanostructures were grown on the micronanostructured surface of 304 stainless steel by hydrothermal method,and a multi-scale composite micro-nano structure surface was obtained.The properties of the surface were studied by various ways,it was confirmed that the surface has good anti-reflection,superhydrophobic,anti-icing and antibacterial properties.Finally,the formation reasons and theoretical mechanisms of the special properties of the surface are analyzed.The main research progress of this thesis is as follows:1.Preparation of surface micro-nano structures by physical and chemical methods(1)Using femtosecond laser as the processing light source,by changing the processing parameters such as laser fluence,laser induced periodic surface structures(LIPSS)and a series of morphology ablated microstructures,such as porous structures,groove structures,and columnar structures,etc.were prepared on the surface of 304 stainless steel and Ti6Al4 V alloy,respectively.The surface micro-nano structures prepared by laser processing were characterized and analyzed by scanning electron microscope(SEM).It is found that the surface structures and morphologies of the two alloy-type materials are highly similar and have almost the same variation law.(2)Using the 304 stainless steel target with laser ablation groove structure as the substrate,Zn O crystals were grown on the surface by the hydrothermal method,and Zn O crystal nanorods and micro-scale crystal clusters were successfully prepared,and finally multi-scale composite micro-nano structured surface were obtained.In addition,based on the physical mechanism and experimental results of the interaction between femtosecond laser and solid materials,the theory of surface two-plasmon resonance is used to analyze the formation mechanism of surface structures with different scales.2.Analysis of special properties of multi-scale composite surface structures(1)Spectroscopic measurements were performed on structured surfaces with different morphologies using an ultraviolet-visible-near infrared spectrophotometer to explore the variation trend of their reflectance spectra,and obtained the corresponding relationship between the surface micro-nano structure parameters and reflectance spectra.The results show that with the increase of the laser fluence and the size of the surface micro-nano structure,the reflectivity of the sample surface in the 250～2500 nm light band gradually decreases,and the average reflectivity of the 304 stainless steel sample with ablated micro-grooves on the surface decreased to 2%,and the surface property of the prepared Zn O composite structure did not change significantly,showing good anti-reflection property.(2)By measuring the surface contact angle at different times,the change trend of the hydrophilicity and hydrophobicity of the femtosecond laser-structured metal surface was monitored,and the rules were summarized according to the measurement results.The hydrophobicity of 304 stainless steel surface before and after the preparation of micro-nano structures were mainly studied.The samples with composite micro-nano structures were placed in the air for 100 days and then measured.The surface contact angle was 152.84° and the sliding angle was about 8°,indicating that the surface has superhydrophobic property.(3)To monitor the freezing speed of water droplets on the structured surface in a low temperature environment,and thereby analyze the influence of surface micro-nano structures on the anti-icing properties of materials.The research results show that under the same conditions,the freezing speed of the sample surface with composite micronano structure is significantly slower than that of other sample surfaces,and the freezing delay time can reach 480 s at-10 °C,indicating that the sample surface has obvious anti-icing property.(4)Using metal sheet with structured surfaces as the culture substrates,the growth of Escherichia coli on each substrate was observed and compared to explore the antibacterial properties of the surface.The experimental results show that nano-Zn O crystal has significant antibacterial effect.Compared with the unstructured surface,the surface of the sample with composite micro-nano structure exhibits a certain degree of antibacterial property with the assistance of nano-Zn O.In addition,relevant theories such as interference/diffraction effects of light,Wenzel / Cassie model are used to analyze the causes of surface properties such as antireflection and superhydrophobicity.In summary,by using a variety of ways to construct the micro-nano structure on the surface of metal materials,a multi-scale composite micro-nano structure surface with good anti-reflection,superhydrophobicity,and obvious anti-icing and antibacterial properties was obtained.The results of this study provide a new idea for the research and development of multifunctional material surface to a certain extent. |
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