Research Of Preparation And Application Of Titanium Oxide Nanotubes

Titanium dioxide（TiO₂） nanotube is a typical n-type wide band gap semiconductor oxide and shows many excellent performances in optical, electrical, photochemical and biology. Due to the large specific surface area and excellent properties of high electron mobility, TiO₂ nanotube, as one of the hot research materials, has attracted widely study to many scholars at home and abroad, and have been widely used in photo-catalytic degradation, dye-sensitized solar cells, and gas sensors.In this paper, TiO₂ nanotubes were fabricated by anodic oxidation method on the Ti foil in the hydrofluoric acid（HF） aqueous solution and ammonium fluoride（NH4F）/glycol（（CH2OH）2） organic aqueous solution, respectively. The study showed that the sample with clear surface structure, highly ordered and uniform distribution was fabricated in ammonium fluoride NH4F/（CH2OH）2 organic aqueous solution. Effect of anodic oxidation reaction time on the formation of nanotubes was studied. SEM images showed that the coverings on the top of TiO₂ nanotube arrays were gradually reduced and the nanotubes tend to clear orifices with the prolonging of the time of anodic oxidation. When the anodic oxidation reaction continues 120 min, the surface of the nanotubes is completely exposed and the diameter of the nanotubes is gradually uniform.In addition, the Ti film was deposited on the FTO conductive glass substrate by magnetron sputtering. TiO₂ arrays with ordered morphology controllable structure were successfully prepared on FTO conductive glass in 0.25wt% NH4 F + 10wt% DI water（CH2OH）2 organic aqueous solution. The effects of anodic oxidation time, F- ion concentration, high temperature annealing on the preparation of TiO₂ nanotube arrays on FTO conductive glass substrates were also investigated.Furthermore, a “quasi-isolated” Pd nanodots/TiO₂ nanotubes composite structure was presented and prepared on the Ti foil in this paper. Analyzation and discussion were carried out about the influence of the nanotube diameter and the amount of Pd nanoclusters on the composite structure. The results show that an ideal composite structure could be obtained with the nanotube arrays prepared at 40 V anodic oxidation voltage and 30 nm-thickness Pd nanoclusters, however, the oxide voltage and the deposition of Pd nanoclusters have no effect on the composition of the crystalline structure.In application, this paper focuses on the application of “quasi-isolated ” Pd nanodots/TiO₂ nanotubes composite structure in hydrogen sensors. The experiment demonstrated that the performance of the hydrogen sensor based on the composite structure is better when the diameter of the nanotubes is about 90 nm and the thickness of Pd nanoclusters is about 30 nm. The response time and recovery time at 0.5%hydrogen volume concentration is 21 s, 23 s respectively, at room temperature. The related chemical reactions were analyzed in detail in this paper, and a physical model of the composite structure was proposed and established to analyze the mechanism of hydrogen sensitivity.