Alumina nanotube array and its formation mechanism

Abstract

Recently, porous anodic alumina (PAA) has attracted much attention in fabrication of nanomaterials and nanostructures because of its application of template and self-organized mechanism although it is discovered in 1950’s. Since the observation of individual alumina nanotubes, in present work, formation mechanism of alumina nanotubes and their array anodized under a pulse voltage was analyzed on the basis of voids in both anodic porous alumina membrane and the tube walls of alumina nanotubes by transmission electron microscope (TEM) observations. Circular, crack-like, and wheel-like voids were observed and considered to be responsible for the formation of alumina nanotubes and their array. Based on microstructural observation of individual alumina nanotubes, the morphology of the tube wall filled with the voids was experimentally determined, which will help to understand the formation mechanism of alumina nanotubes. Our observations and analyses give further information on self-organized mechanism of anodic porous alumina membrane.