Study On Surface Wettability Of Anodic Aluminum Oxide Film With Ordered Nanopore Arrays

This dissertation firstly summarized several basic theoretical models aboutwettability of solid surface, commented their characteristics and difficult problemsbased on the previous investigation in wettability of anodic aluminum oxide (AAO)film with ordered nanopore arrays, in order to emphasize the significance of AAOfilm in the research of wetting regime and special wettability. Further, it aimed at thegeometrical fabrication and chemical modification for studying the physicalmechanism of variation of wettability induced by surface nanostructure and surfacechemical component. Finally, the dissertation titled "Study on Surface Wettabilityof Anodic Aluminum Oxide Film with Ordered Nanopore Arrays" systematicallysummed up the author’s research works and results as following:1. Firstly, a model about intermediate wetting state was developed after a dropletdeposited on the surface with ordered nanopore arrays. Subsequently, the wettabilityof homogeneous-AAO films with ordered nanopore arrays prepared by using anelectrochemical two-step anodization method was measured via employing bidistilledwater as testing liquid. It was found that theoretical simulations were consistent withexperimental measurements:1) with the increase of nanopore depth (or nanopordiameter), water contact angle are increased gradually;2) water contact angle isirrelevant with the volume of water droplet. Further, the physical mechanism ofvariation in contact angle induced by surface geometric parameters (nanopore depthor nanopore diameter) was clarified. The results indicated that the water into thenanopores and the air trapped inside the nanopores play an important role indetermining to modulate the systematical interfacial free energy density of awater-air-AAO system. It controls the adjustment of behavior of the three contactlines, resulting in achieving different contact angles. This is the main reason ofvariation in contact angle induced by nanostructures.2. Firstly, AAO films with ordered nanopore arrays were prepared by using anelectrochemical two-step anodization method. Subsequently, the wettability of thesestructured and heterogeneous surfaces was measured via employing bidistilled water and1,2-dichloroethane as testing liquid. It was found that, with increase of nanoporediameter, contact angles of the two kinds of liquid were increased gradually. Furtherusing Owens’s and Yang’s methods, the composition of solid surface energy for AAOfilm was analysed. It was found that the contributions of surface nanostructure andsurface chemical component are about90%and10%respectively. Obviously, theincreased nanopore diameter leads to change surface energy, further obtains thevariation in wettability. The results indicated that AAO’s surface energy controls theadjustment of behavior of three contact lines, resulting in achieving different contactangles. This is the basic reason of variation in contact angle induced bynanostructures.