Stress-affected and stress-affecting instabilities during the growth of anodic oxide films

Recent Advances in Nanoporous Anodic Alumina: Principles, Engineering, and Applications

The development of aluminum anodization technology features many stages. With the story stretching for almost a century, rather straightforward-from current perspective-technology, raised into an iconic nanofabrication technique. The intrinsic properties of alumina porous structures constitute the vast utility in distinct fields. Nanoporous anodic alumina can be a starting point for: Templates, photonic structures, membranes, drug delivery platforms or nanoparticles, and more. Current state of the art would not be possible without decades of consecutive findings, during which, step by step, the technique was more understood. This review aims at providing an update regarding recent discoveries-improvements in the fabrication technology, a deeper understanding of the process, and a practical application of the material-providing a narrative supported with a proper background.

Improved growth rate of anodized TiO2 nanotube arrays under reduced pressure field and light illumination

The one-dimensional titanium oxide (TiO₂) nanotubes (TONT) can be rationally fabricated in the fluoride-containing electrolyte by electrochemical anodization. The high-speed growth of TONT for elongated nanotubes is highly desirable because the undesirable chemical etching will induce "nanograss" on the top of nanotubes and restrain the continued elongation of nanotubes. Herein, the external fields were employed to accelerate the growth of TONTs and obtain the elongated TONT arrays. A growth rate up to 18μm/h was achieved under the presence of reduced pressure (0.07MPa) and UV light (365nm) stimulation. The generation of longer nanotube arrays could be attributed to the applied fields, which facilitate timely gas pumping out and induce chemical equilibrium shift forward. The TONT films obtained under different parameters were subsequently employed as anodes for photoelectrochemical (PEC) water splitting. The photocurrent (at 0V vs Ag/AgCl) of TONT electrode obtained under external fields represented a 50% enhancement compared with the photoanode produced by the conventional method.