Fabrication And Performance Of Extreme Wettability Surfaces On Titanium Alloy Substrates

The extreme wettability surfaces,which can be also divided into superhydrophobic,superhydrophilic,superoleophobic and superoleophilic surfaces,have exhibited promising prospects in self-cleaning,drag reduction,anti-fogging,anti-icing,liquid transportation and oil/water separation.The research of extreme wettability surfaces helps to explore the relationship between surface wettability and microstructures deeply,and promotes the development of surface science.Titanium and its alloys possess distinct properties such as high specific strength,excellent heat resistance and anti-corrosion performance,with wide applications in aviation,shipbuilding,biomedicine and oil industries.Thus,preparing extreme wettability surfaces on titanium alloy substrates will provide potential values in fundamental research and development.This thesis mainly studies the preparation of superhydrophobic,superamphiphobic and underwater superoleophobic surfaces on titanium alloy substrates.Firstly,we fabricated superhydrophobic Pb-coated titanium alloy surfaces by means of immersion method in Pb(CH3COO)2 aqueous solution and the deposited hierarchical rough micro-structures own features similar to the upper sides of lotus leaves.The wettability,micro-morphologies and corresponding chemical compositions of as-prepared specimens were characterized by Contact angle measurements,Scanning electron microscopy,Contact probe surface profiler,Energy-dispersive spectroscopy and X-ray diffraction system,respectively.The variations in morphologies,static and dynamic water contact angles,and surface roughness over immersion time were studied in detail.The self-cleaning test was conducted on superhydrophobic surfaces and the force analysis of the dust particle that interacts with water droplet was carried out as well.Secondly,superamphiphobic surfaces overcome the weakness of superhydrophobic surfaces,whose poor oleophobicities gradually emerged in practice.Inspired by the formation of titania nanotubes,we proposed that superamphiphobic surfaces on titanium alloy substrates were prepared through one-step anodization method.Micro-morphologies with re-entrant structures were generated on titanium alloy surfaces and superamphiphobicity was obtained after modification of low surface energy,showing that the prepared surfaces repel both water and oils extremely.The reaction mechanism was analyzed.The stability and friction tests were performed to evaluate durability,corrosion resistance and abrasion resistance.Most superoleophobic surfaces can only keep their superoleophobicity valid when exposed to air.O nce immersed in water,superoleophobic surfaces usually lose their capability of repelling oils.In this thesis,the electrochemical etching technique was applied to fabricate durable underwater superoleophobic surfaces on titanium alloy substrates.The prepared surfaces displayed superhydrophilicity in air and exhibited superoleophobicity when immersed in water.The adhesive behaviors between oil droplets and the titanium alloy surfaces was characterized in water qualitatively and the wettability conversion was analyzed as well.The underwater superoleophobic surfaces can adapt to harsh conditions and be used for self-cleaning,anti-fouling and anti-corrosion in water.