Fabrication And Properties Of Bio-inspired Superhydrophobic Surfaces On Aluminum Substrates

Marine environmental corrosion and biofouling are ubiquitous and detrimental problems of metals and alloys,restricting their widely applications in vessels,machinery manufacturing,aerospace etc.Wettability is one of the fundamental properties of solid surfaces.Recent years,learning from nature,bio-inspired superhydrophobic materials have become a burgeoning research area and arouse much attention result from their potential applications in self-cleaning,oil/water separation,drag reduction,anti-fog,anti-icing,fog-harvest and so on.With unique surface water-repellent property,superhydrophobic surfaces on metallic substrates provide a very intriguing possibility for anti-corrosion and anti-biofouling applications.In this thesis,we developed two efficient fabrication methods,viz,high-voltage hard anodisation and one-step fatty acid electrodeposition techniques,successfully designing and fabricating superhydrophobic surfaces on aluminum substrates.Meanwhile,we investigated the performance of self-cleaning,marine anti-corrosion and anti-biofouling,chemical stability,mechanical stability,thermal stability etc.in details and revealed the corresponding anti-corrosion and anti-biofouling mechanisms.We developed a high-voltage hard anodisation method to fabricate bio-inspired superhydrophobic surfaces on aluminum substrates.Self-congregated Dianthus caryophyllus-like superhydrophilic/superhydrophobic surfaces were produced,which has not been achieved and reported so far.The dynamic morphology evolution model was enriched,depicting the morphology changes versus anodisation time as nanotubes structure with small diameter,nanotubes structure with large diameter,nanowires,Pyramid-like structure and Dianthus caryophyllus-like structure.Moreover,the electrochemical and biological adhesion experimental results demonstrate that the fabricated Dianthus caryophyllus-like superhydrophobic surface exhibits potential applications in marine anti-corrosion and anti-biofouling.Self-cleaning and chemical stability tests suggest that the as-prepared superhydrophobic surfaces exhibit excellent thermal stability and self-cleaning ability.The water droplets with higher temperature and lower surface tension can still retain its Cassie contact upon the surface,improving the possibility of the fabricated superhydrophobic surface serving under high temperature environmentsWe developed an efficient fatty-acid-based one-step electrodeposition technique to fabricate bio-inspired superhydrophobic surfaces on aluminum substrates.This is a simple,fast,low-cost,environmental friendly and versatile method,achieving lotus leaf-like micro-nano hierarchical structure and low surface energy simultaneously during the electrodeposition process.Compared with traditional methods,the one step electrodeposition technique has distinct superiority with great potential.In this thesis,we carried out the one step electrodeposition research work in three reaction systems,including stearic-acid-system,palmitic-acid-system and myristic-acid-system,obtaining superhydrophobic surfaces with static water contact angle of 169.7°,167.4° and 162.1° respectively.Further property characterizations reveal that the superhydrophobic surfaces fabricated through one-step electrodeposition strategy exhibit excellent marine anti-corrosion and anti-biofouling performance.Simultaneously,these superhydrophobic surfaces possess good chemical stability,durability,mechanical stability,self-cleaning capability,etc.expanding the application areas of this kind of superhydrophobic surfaces.The research works in this thesis also reveal the anti-corrosion and anti-biofouling mechanisms of bio-inspired superhydrophobic surfaces.The typical micro-nano hierarchical structure of superhydrophobic surface can entrap large amount of air between the structural gaps and spaces,forming “air cushion”,reducing contact area of corrosion medium and substrate.The Cassie contact mode hinder the corrosion media infiltrating and diffusing to the substrate.What’s more,the extremely low surface energy and surface adhesion make it hard for biological organisms to settle,mitigating the happening of biofouling.All experimental results in this thesis demonstrate that bio-inspired superhydrophobic surface on metallic or alloy substrates can provide an efficient solution strategy for marine environmental corrosion and biofouling problems,which is a promising protection technology.