Construction And Properties Of Durable Aluminum-based Superhydrophobic Surfaces

As one of the important structural materials,aluminum alloy is widely used in automobile,construction industries and daily life because of small specific gravity and high strength.In addition,it is also one of the main metal materials used in the defense industry,such as used in submarines,aircraft,and warships.However,the aluminum alloys can be corroded in practical applications and which can cause the decrease of the mechanical strength and mechanical properties of aluminum alloy.Moreover,the corrosion can result in environmental pollution and resource loss.Natural superhydrophobic phenomenon provides new ideas for aluminum alloy protection.Researchers have developed a variety of preparation methods by studying superhydrophobic surfaces in nature.They have prepared superhydrophobic surfaces on aluminum alloy substrates successfully and which has greatly improved the corrosion resistance of aluminum alloy.However,some problems exist in the artificial aluminum-based superhydrophobic surfaces,and the main problem in practical application of superhydrophobic aluminum alloy surfaces is poor durability.Thus,how to improve the durability of aluminum-based superhydrophobic surfaces is a research hotspot all around the world.In this study,aluminum alloy superhydrophobic surfaces with excellent hydrophobic properties were prepared by two methods: silane modification and nanocapsule deposition.The best preparation process was explored,and the performance of the prepared aluminum-based superhydrophobic surface was characterized and analyzed.The main research work of this dissertation is as follows:(1)Preparation of aluminum-based superhydrophobic surface by silane modification method: Rough structure on the aluminum alloy surface was formed by boiling water etching and then modified by hexadecyltrimethoxysilane.Consequently,a superhydrophobic surface with a contact angle of 156.9° and a sliding angle of 3° was prepared.The micro-nano grid structure of the superhydrophobic aluminum alloy surface was observed by scanning electron microscopy.The FT-IR has confirmed that hexadecyltrimethoxysilane was successfully grafted onto the surface of aluminum alloy.Combining SEM with FT-IR,the hydrophobic mechanism of the superhydrophobic surface was explained.(2)Properties of aluminum-based superhydrophobic surface prepared by silane modification method: The excellent durability of the prepared aluminum-based superhydrophobic surface was characterized by room temperature placement,UV irradiation,and different pH droplets.The high contact angles with different aqueous solutions indicated that the superhydrophobic surface has hydrophobic diversity.The corrosion resistance is obviously improved which was investigated by electrochemical measurement.(3)Preparation of self-healing aluminum-based superhydrophobic surface by nanocapsule deposition method: Firstly,PDA@HDTMS nanocapsule emulsion was prepared by coating hexadecyltrimethoxysilane with polydopamine(PDA)in a Tris-buffer solution while polydopamine was formed by the oxidative polymerization of dopamine.The aluminum alloy superhydrophobic surface with a contact angle of 155.3° and a sliding angle of 3° was prepared via deposition method by using the adhesion of polydopamine.The size of the nanocapsules was about 200 nm which was observed by transmission electron microscopy.The microcavities and nanopapillary structures on the surface were observed by scanning electron microscopy while the existence of PDA and HDTMS on the surface was confirmed by FT-IR.The surface sediments were PDA@HDTMS nanocapsules,and which was certified by combining the chemical composition with the micromorphology.(4)Study on the performance of self-healing aluminum-based superhydrophobic surface: The good durability of self-healing aluminum-based superhydrophobic surface was investigated via room temperature placement,high temperature environment placement,ultraviolet irradiation,and different pH droplets.The obtained aluminum alloy also exhibited hydrophobic diversity and which was demonstrated by the high contact angles on different substance with various aqueous solutions.The superhydrophobic aluminum alloy had excellent self-cleaning performance and which was approved by water droplets could take away simulated pollutants(such as chalk ash)easily.Compared with the untreated aluminum alloys,the corrosion resistance of the superhydrophobic aluminum alloy is obviously improved which was investigated by electrochemical measurement.While,the superhydrophobic surface treated by plasma treatment can restore its superhydrophobic property after heating for 10 min,indicating that the superhydrophobic surface has self-healing function.Finally,the corrosion resistance mechanism and self-healing mechanism were explained by the mechanism diagrams.