Large Surface Area Titanium Oxide Nanotube Arrays Anodized in KH{sub}2PO{sub}4/NH{sub}4F/Citric Acid Electrolytes by Multi Step Voltage Method

摘要

We present titanium oxide nanotube arrays for solar cell, gas sensor, ultra filter, and biomaterials. To make titanium oxide nanotubes, potassium phosphate monobasic (KH{sub}2PO{sub}4) 1M aqueous electrolytes containing fluorine 0.15M and citric acid 0.2M were firstly prepared and 99.7% pure titanium was anodized. Titanium oxide nanotube arrays were fabricated at anodization potential range from 20V to 28V and 4.64pH. Citric acid was very useful to control the pH of the 1M KH{sub}2PO{sub}4 water electrolyte solution within 3 to 5 [1]. Nanotube length of 2μm was independent on anodization time at 20V for anodization time from 5 to 23 hrs which was observed by FESEM. Pore diameter and length of titanium oxide nanotube were increased with anodization voltage of 20 to 28V. The pore diameter and length of titanium oxide nanotube, as shown in Fig. 1 and 3, were 100 to 150nm and 2.0 to 3.0μm, respectively. At higher anodization voltages than 25V, porous layer was made and titanium oxide nanotube could not be made.