Abstract
Preparation of long, straight nanopore structures using the anodization process is relatively simple, low cost, and easy to mass-produce as compared to other processes. In addition, application properties of the nanopore structures such as size and uniformity can be easily adjusted by varying relevant operating parameters. The most popular and well-known application of the anodization process is the preparation of aluminum oxide membranes. For the past five years, researchers began to study the preparation of titanium dioxide nanotubes through Ti anodization. Titanium dioxide nanotubes have excellent photocatlytic and self-cleaning properties. They can be applied to water degradation processes because of their excellent electrocatalytic property. Such property allows them to be used in methanol oxidation process. Titanium dioxide nanotubes can also be used in a wide range of areas such as dye-sensitized solar cell and hydrogen sensing. Experimental results obtained from this research include the following. (1) Nanoporous structures with pore size of 20~30nm were successfully prepared with addition of a deep eutectic solvent (DES), and the growth rate of the titianium dioxide nanotubes can be as high as 9.79μm/min. Pore size of the nanostructure prepared can be increased from 50nm to 80~100nm by combining DES and glycerol as the solvent system. (2) Non-tubular nanostructures were successfully prepared through control of the composition of the electrolyte and reaction mechanism. Electrolyte composed mainly of succinic acid was used to prepare nanorod arrays with heights of 20~100nm. (3) Reaction mechanisms and applications of the titanium nanotubes prepared were studied. Comparison was made for titanium dioxide nanotubes of two different lengths, 50 and 100nm. (4) A modified nanotube growth mechanism was proposed to explain the high growth rate achieved in this work made possible by addition of the DES. (5) Field emission characteristics of the titania nanotubes of 20-30 nm with various heat treatment were studied. The turn-on field was 1.5V/μm (defined at current density of 1μA/cm2) when the vacuum gap was 300μm. The current density reached 1 mA/cm2 at the applied field of 2.2V/μm. (6) The relationship between the field enhancement factor (β) and vacuum gap was studied. The resulting absolute field enhancement factor, β0, was determined for the titanium dioxide nanotube arrays to be 11,111, which is larger than that of the carbon nanotubes grown on silicaon wafers.