Generation And Characterization Of Several Engineering Material Surfaces With Special Wettabilities

Wettability of a solid surface is an important property governed by the surfaceenergy and the geometric structure. In point of surface energy, it is known that wettingbehavior of a solid surface is determined by its outermost molecular-level structure,which is one way for controlling the wettability of a surface. Another way to tune thewettability is to fabricate micro-and/or nano-structures on the surface. In recent years,much research effort has been devoted to generating various special wettabilities bycombining the fabrication of geometric structure and the chemical modification.In this work, we have designed and fabricated several functional coatings withspecial wettability that include superhydrophilic antifogging coatings,superhydrophobic coatings with high contact angle and low sliding angle. The mainworks are listed as follows:1. Silica nanoparticles were self-assembled on3-aminopropyl triethoxysilane(3-APTES) modified onto glass substrates through an electrostatic interaction, leadingto a surface with microscale roughness morphology. Then smaller grain size of silicananoparticles with a mean size of50nm were further assembled on as-prepared roughsurfaces by a Layer-by-Layer electrostatic method to fabricate micro/nanoscalecomposite structures. Atomic force microscope(AFM) and scanning electronmicroscopy(SEM) were employed to characterize the topography of silica films. Asuperhydrophilic surface with water contact angle about0°was obtained due to thesynergistic effect of superhydrophilic silica nanopartilcers and a specific surfacemicro/nanoscale roughness. A good antifogging performance was further acquired forlittle light scattering. Subsequent modification with octadecyl triethoxysilane to thesurface made the prepared transparent superhydophobic coatings to have goodstability and abrasive resistance.2. Superhydrophobic film on zinc surface with micro/nanometric compositestructure was successfully prepared through a simple immersion process ofpentadecfluorooctanoic acid solution in ethanol, and the influences of the temperatureand the reaction time on surface wettability are studied. The surface morphology and chemical composition of the superhydrophobic film were characterized by SEM, XPSand FTIR spectra respectively. And the surface wettability is explained and analyzedusing Cassie theory.The prepared superhydrophobic surface showed perfectenvironmental stability and durability for some common solvents and NaCl solution.3. By a simple one-step solution-immersion process, we directly fabricated thepetallike structures similar to that of a lotus leaf on aluminum substrate. Afterchemical modification with octadecyl triethoxysilane, the wettability of theas-prepared surface was changed from superhydrophilicity to superhydrophobicity.Through changing temperature and time, the static contact angles (CAs) for waterdroplet reached as high as163°and the rolling angles were less than5°. The specialhierarchical structure of all films, element composition, formation mechnism of thesuperhydrophobic coating, the wetting behavior and the stability of thesuperhydrophobic surfaces in the corrosive liquids with a wide pH range were alldiscussed.