Key Engineering Materials Vols. 336-338

Abstract: Nano anatase TiO2 thin films on glass slide substrates were prepared via a dip-coating method using refluxed sols (RS) as precursors, then dried under infrared light and calcined at 500°C for 30min. The RS sols and TiO2 films were characterized by FT-IR, XRD, TEM, UV-Vis and SEM. The photocatalytic activities of the film samples were tested by the degradation of methyl orange solution with a concentration of 10mg/L under UV light irradiation. The results reveal that the RS sols are flavescent, alkalescent and contain needle-like anatase crystals. The TiO2 films are uniform, compact and transparent, their maximal light transmittance exceed 80% under visible light region. The degradation of methyl orange results illustrate that the RS-6 TiO2 thin films show the best photocatalytic activities, the decoloration rate of the methyl orange solution with RS-6 TiO2 thin films reachs 99% after irradiated 160min under UV light.

Abstract: TiO2 nanocrystalline films were prepared by electrophoretic deposition (EPD) under a pulseperiodic electric field. The EPD behavior of TiO2 nanocrystalline suspension was investigated. The uniform 9.2-μm-thick TiO2 film was obtained by reasonably controlling the EPD condition. A dye-sensitized solar cell, with the EPD TiO2 film as the photoanode, obtained about 4.1% of photon-to-electron conversion efficiency (η). Its Jsc, Voc and fill factor (ff) are 11.6 mA/cm2, 0.65 V and 0.55, respectively. The effect of TiCl4 modification on the photovoltaic property of the solar cell was also discussed.

Abstract: Anodic aluminum oxide (AAO) is commonly used as a starting template for fabrication of several kinds of functional nanoscale devices due to its homogeneous nanohole structure with high aspect ratio. In this paper, high density and uniform titanium dioxide nanotube array films were prepared via liquid phase deposition method by immersing the AAO templates in an aqueous ammonium hexafluorotitanate solution. The phase and microstructure of the nanotube array films were characterized by X-ray diffraction and field-emission scanning electron microscopy. It was found that the mean inner diameters of nanotube are 40-100 nm, mainly depended on different templates and post treatment condition; the phase of as-deposited TiO2 array film was amorphous, while it became anatase at above 400°C.

Abstract: TiO2 is one kind of semiconductor-based photocatalyst. TiO2 shows relatively high reactivity and chemical stability under ultraviolet (UV) light. However TiO2 is a poor absorber of photons in visible light. In order to improve the absorption efficiency, the coatings of TiO2/WO3, WO3 and TiO2 on ITO were prepared by liquid phase deposition (LPD) and dip coating method, their microstructure, surface properties, photoelectrochemical properties are investigated in this paper. XRD results showed that the phases on the composite coatings are mainly anatase, rutile and WO3 respectively, the SEM results showed that the coatings of TiO2 and TiO2/WO3 are distributed evenly on the materials surface. The electrochemical experiment results showed that open circuit potential of TiO2 and TiO2/WO3 with presence of the UV light illumination were about -343 mV and –650 mV respectively, comparatively the rest potential of 304 stainless steel is about 48 mV, which means that the TiO2 or TiO2/WO3 coatings can protect 304 stainless steel from corrosion, and TiO2/WO3 coatings retained for a while anticorrosion even absence of UV light.

Abstract: To improve its visible light response capability, a new narrow bandgap zinc ferrite semiconductor was in-situ introduced into the matrix of titanium dioxide nano film. ZnFe2O4 doped TiO2 composite films have been successfully formed on glass and stainless steel substrates from aqueous solution through equilibrium reaction between iron (III)-titanium (IV)-fluoric complex and boric acid, followed by in-situ hydrothermal conversion and crystallization in the Zn2+-contained basic environment. The obtained films were densely packed and had no visible cracks; clear photovoltaic responses were observed in the anodic direction, and they were much larger in the presence of ferrite dopant. It is suggested that the shift of the corrosion potential was ascribed to photo-induced charge separation between the conduction band of ZnFe2O4 and its counterpart TiO2 nano-particles.

Abstract: Highly conductive IrO2 thin films were prepared on Si (100) substrates by pulsed laser deposition technique from an iridium metal target in an oxygen ambient atmosphere. The effect of substrate temperature on the structure and electrical properties of IrO2 films was investigated. The deposited films at substrate temperatures ranging from 250 to 500°C under an oxygen pressure of 20Pa were pure polycrystalline tetragonal IrO2 and the preferential growth orientation changed with the substrate temperature. IrO2 films were well solidified with the fairly homogeneous thickness and exhibited a good adhesion with the substrate. The room-temperature resistivity of IrO2 films decreased with the increase of substrate temperature and the minimum resistivity of (42±6) μ-·cm was deposited at 500°C.

Abstract: The nanocomposite coatings were prepared on the surface of PVC substrate using spinning technique with attempts of introducing nanosized iron oxide particles with different morphology into the organic-inorganic hybrid matrices. The hybrid matrices were derived from 3-glycidoxypropyltrimethoxysilane (GLYMO) and tetraethoxysilane (TEOS) with a process of hydrolyzing and condensation. Nanosized iron oxide particles were synthesized by hydrolysis of FeCl3 solution at different pH value and different temperature. The effects of different additions on nanomechanical properties of the nanocomposite coatings were investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and MTS Nano Indenter XP system. It was found that the acicular α-FeOOH and spherical α-Fe2O3 particles were synthesized, both of them dispersed homogeneously. Nanoindentation and nanoscratch behaviors of the nanoindenter system showed that both of the nanocomposite coatings reinforced the nanomechanical properties of the PVC obviously. Especially, the contribution of acicular α-FeOOH was more remarkable than the spherical α-Fe2O3.

Abstract: Zinc oxide films have been deposited on ITO/glass substrate by a two-step electrodeposition method from zinc nitrate aqueous solution. The two-step electrodeposition process included a potentiostatic pre-deposition and a galvanostatic deposition. Obtained ZnO film possesses high c-axis preferential orientation, smooth and compact morphology, high transmittance in the visible band, and optical band gap of 3.43eV. Compared with the film prepared by direct galvanostatic deposition, the crystalline quality and optical properties of ZnO films were significantly improved.