Investigation Of Fabrication, Characterization And Performance Of The TiO₂ Nanofilms On Al Substrate

TiO₂ is a very important wide bandgap semiconductor, which mainly include three crystal structures. Anatase and rutile are tetragonal. Brookite is orthorhombic. From 1972 years, the first water splitting was reported using a TiO₂ photoanode, TiO₂ with photocatalysis and photoinduce hydrophilic properties has attracted much attention in terms of organic contaminants and self-cleaning applications. The TiO₂ films with many interesting properties, such as easy to reuse, non-toxicity, low cost, excellent efficiency, sterilization, deodorization, anti-corruption, which have a wide applied field of air cleaning, waste water purification, self-cleaning and anti-fogging.TiO₂ nano-crystalline and Al substrate are combined together by author, and the TiO₂ thin films on Al substrate were prepared in the condition of no changing the properties of Al, which has obtained photocatalytic and self-cleaning cermet composite materials. However, most traditional method require processing temperatures higher than 400℃for the crystallization of TiO₂ particles, which is high cost and have a limit the use of other substrates. As Al substrate is easy to melt, it is significant to the fields of waste water purification and air cleaning that lucubrate TiO₂ thin films on Al substrate at lower temperatures.The main goal and motivation of the present work focused on the preparation of TiO₂ thin films on Al substrate at low temperatures. Nanocrystalline TiO₂ thin films were deposited on Al substrates at low temperatures by Sol–gel method, peroxo-titanic acid method and hydrothermal method, respectively. The synthesized thin films were characterized by canning electron microscopy (SEM), UV-Visible Spectrophotometer (UV-Vis), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR Spectroscopy (FT-IR) and Raman spectroscopy (Raman). Photocatalytic and hydrophilic properties of TiO₂ thin films fabricated by the those methods were investigated each other, which provide a theory base of industrialization for depositing TiO₂ thin films on Al substrates. The main results and progresses of this thesis are outlined as following:1. TiO₂ thin films prepared directly by Sol-gel method were amorphism; Anatase-type TiO₂ took place at calcination temperature 450℃. It was found that different substrates showed some difference of photocatalytic activities. Elements of different depths in the thin films were measured by XPS, which received the law of interface diffusion of different substrates. The interface diffusion between TiO₂ and substrates led to the difference of photocatalytic activities and the results was explained by the theory of crystal and electron transfer. In addition, as the number of layers increased the photocatalytic efficiency improving. Photocatalytic efficiency attained to maximum when the number of layers more than 6 layers.2. The anatase-type TiO₂ Sol was synthesized less than 100℃by peroxo-titanic acid method and hydrothermal method, respectively. Low-temperature dipping coating of anatase films on Al substrate and the morphologies and structure for the TiO₂ films were investigated. The photodegradation activity of methylene blue (MB) solutions under UV irradiation was studied. Photocatalytic efficiency attained to maximum when the number of layers more than 4 layers and the photoinduced hydrophilic properties were also investigated.3. The three methods were compared each others. TiO₂ films on Al substrate were prepared by Sol-gel method showed good adhesion mainly due to interface diffusion, excellent photocatalytic activities and photoinduced hydrophilic properties. But the disadvantage was heat treatment above 400℃, which led to high cost; TiO₂ films on Al substrate were synthesized by peroxo-titanic acid method show little adhesion, some photocatalytic activities and photoinduced hydrophilic properties, in addition, the process was complicated and wasted of abundant water; TiO₂ films on Al substrate were prepared by hydrothermal method showed least adhesion, least photocatalytic activities and photoinduced hydrophilic properties. But hydrothermal method is simple, no heat treatment was required to obtain nano-sized crystals of TiO₂...