Abstract:
Surfaces of alumina with different morphologies have been fabricated by etching the porous anodic aluminum oxide (AAO) membrane with NaOH solution under proper conditions.And then,the etched surfaces were modified with fluoroalkylsilane (FAS).The water contact angles of the modified surfaces were detected by contact angle method,and the surface composition and morphologies were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).The results showed that the thin part of the pore walls in the porous surface layer and the porous bulk layer of AAO film was first dissolved in the process of etching AAO film with NaOH solution,and micron sized narrow cracks were formed under the action of the surface tension of water.Alumina nanowires were formed when most of the pore walls of AAO films were dissolved.The alumina nanowires accumulated into micron-scale clusters under the action of the gravity and surface tension of water during the process of drying,resulting in the formation of the honeycomb-like micron-and nano-composite double-scale hierarchical structures.The static water contact angle of the FAS-modified honeycomb-like structured surface (151.7 °) was much higher than that of the FAS-modified nanoporous surface (138.3 °) and the smooth surface (101 °).