| In nature,a large number of biological surfaces show special wettability.At present,the functional surfaces prepared by bionics have been applied to the fields of self-cleaning,anti-oil and anti-fouling,anti-fog,anti-icing,droplet directional movement and so on.The preparation of superhydrophobic functional micro-nano structures on the metal surface can make the liquid with low surface energy(surface energy is less than water's 72.5 m N m-1)difficult to adhere to the metal surface,so the corrosion resistance of the liquid can be significantly improved.Therefore,the research is getting more and more attention from researchers.The re-entrant structure and low surface energy play an important role in the formation of superamphiphobic surfaces on inherently hydrophilic metallic materials.This study introduced a"top-down"and"bottom-up"strategy of combining the design train of thought,contains a picosecond laser ablation process,electrochemical polishing process and electrochemical deposition process.Firstly,laser ablated orderly micron grade cone structure on the metal substrate,and then the orderly micron cone combined with the layered nanometer nickel pyramid structure to form3D re-entrant micro/nano hierarchical structure.Finally,the surface modificated with low surface energy shows excellent superamphiphobicity.The wettability stability and functionality of the metal are also discussed.The main studies were as follows:(1)Analyzing the existed two process strategies for preparing re-entrant structure,summarizing the advantages and disadvantages of the two processes,putting forward a design strategy that combines"top-down"and"bottom-up"process strategies,and putting forward a combined process of picosecond laser ablation,electropolishing and electrodeposition to prepare re-entrant structure.(2)The orthogonal experiment of three factors and five levels was designed to determine the influence degree of laser processing parameters.The surface multi-level micro-nano re-entrant structure was tri-produced in accordance with the design strategy and the wettability was tested.The differences of wettability of metal surface prepared by a single process and combined process were analyzed and compared to explore the influence of single micron structure,single nanometer structure and micro-nano structure on the formation of re-entrant structure.Both of single process of laser ablation fabricate micron copper cones structures on the surface and a single electrodeposition process preparation of nano-sized nickel pyramid structures did not achieve superamphiphobic properties,only a combined laser-electrochemistry process prepared micro/nano composite structure showing good superamphiphobic properties,which contact Angle of water droplets and oil droplets reached 161°±4°and 151°±4°,rolling contact Angle to 2°and 10°respectively.(3)The influence of laser parameters(energy,scanning times,scanning speed,scanning interval)on the morphology,size and surface wettability of micro and nano structures was studied by analyzing the surface morphology,three-dimensional morphology and profile.Results show that when the laser energy is 6 w,scanning interval is 20?m,scanning velocity is 200 mm/s,scanning times is 20 times,the surface appear orderly,neat and has a certain height of copper cones structures.After the subsequent combined process,the surface showing good superamphiphobic properties.(4)By adding the steps of electrodeposition process,the surface nanostructure morphology and surface wettability performance after no electrodeposition treatment,one-step electrodeposition treatment and two-step electrodeposition treatment were analyzed and compared,and the influence of electrodeposition treatment steps on the formation of nanometer re-entrant structure was explored.The results show that the nanoscale structures in the second step of electrodeposition grow on the submicron structures formed in the first step of electrodeposition due to the tip effect,and the multi-level composite structures are formed between the cracks.After two electrodeposition processes,the contact angles of water droplets and oil droplets reached 161°±4°and 151°±4°,respectively,and the surface showed good superamphiphobicity.(5)Measurement of the hydrophobicity of samples prepared by different processes under temperature changes:the hydrophobicity of the surface of two kinds of samples in low temperature environment is worse than that in normal temperature environment.Droplet bouncing tests show that when the laser scanning interval is approximately equal to the laser spot diameter,the droplets falling from high points can experience two complete bouncing processes on the surface of the sample,which proves that the Cassie state of the droplet does not change to Wenzel state,and the stable Cassie state is related to the abundant multi-level micro-nano composite structure.The explanation of droplet moving upward along the slope against gravity shows that the metal surface prepared by the combined process shows excellent superamphiphobicity.This paper provides a creative process to fabricate hierarchical micro/nano 3D re-entrant structure on the metal,which play an important role to achieve superamphiphobic performance.Meanwhile,studying the influence of a combined process parameters on the micro/nano composite structure and the stability of the surface wettability provides a new thought and method for the potential applications of the automotive,aerospace and marine sectors. |
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