Key Engineering Materials Vols. 512-515

Abstract: In the present work, we demonstrated a facile process to prepare an open-ended high aspect-ratio TiO2 nanotube films through separating the anodic TNT array from the Ti substrate by a small reverse bias and opening the tube bottom by a chemical etching. The possible mechanisms of film detachment and pore opening processes have been briefly discussed. Such a process allows controlling the open-ended morphology by the straightforward chemical etching, which shows great potential in many applications, such as flow-through photocatalytic reactions, biofiltration, and diffusion controlling, and so on. An example using the open-ended TNT films is finally given as a flow-through photocatalytic reactor. The photocatalytic film has been shown to have multiple functions such as physical separation of contaminants, filtration, and decomposition of organic pollutants during diffusion.

Abstract: Titanium substrate was etched by oxalic acid and hydrochloric acid respectively. Then the anodes of RuO₂-IrO₂-TiO₂/Ti were prepared by Pechini method. The surface morphology of anodes was studied with SEM, EDX and XRD. The electrocatalytic capability of anodes was studied by polarization curve and cyclic voltammetry curve. The effect of Acid etching process on anode life was studied by accelerated life test. The results show that there was an obvious effect of acid etching on surface morphology of the anodes. The result indicates that the anode with hydrochloric acid etching have the better electrocatalytic capability and accelerated life.

Abstract: The anodes of RuO₂-IrO₂-TiO₂/Ti were prepared by Pechini method. The surface morphology and electrocatalytic capability of anodes were studied by SEM, EDX, XRD, polarization curve, cyclic voltammetry curve and accelerated life test. It has been shown that the anodes have uniform surface composition, and the surface density of the anodes were increased as the sintering temperature increased, some active elements were crystallization grains at the surface of the anode when sintering temperature ≥500°C. The chlorine evolution capability of anode had a tendency to increase firstly then fall down afterwards as the sintering temperature increased. But the electrocatalytic capability of anodes showed an opposite tendency. The RuO₂-IrO₂-TiO₂/Ti anode prepared at 500°C presents the longest service life.

Abstract: A sol-gel processing technology was employed to synthesize fine SrTiO₃ powder by using strontium nitrate (Sr(NO₃)₂) , butyl titanate (Ti(OC₄H₉)₄) as precursors, citric acid (C₆H₈O₆) as complexing agent and (ethylene) glycol (C₂H₆O₂) as stabilizer. Prepared the precursors in liquid phase and then calcined the precursors to achieve nano-sized SrTiO₃ powders. The microstructure and composition of the as-synthesized samples were characterized by X-ray diffraction (XRD), Scan Electron Microscopy (SEM), and the photocatalytic activity was studied. The results showed that all the SrTiO₃ particles were identified as perovskite phase. The pH values, the content of the acetic acid, the heat treat temperature play important roles on the synthesis of the SrTiO₃ photocatalyst. When the pH=1, n(Sr(NO₃)₂ ) : n(Ti(OC₄H₉)₄) = 1 : 1, n(Sr(NO₃)₂ ) : n(C₆H₈O₆)=1:1.7, the product has better rate of photodegradation for the Methylene Blue under the ultraviolet condition.

Abstract: A facile route was demonstrated to obtain an efficient graphene-hybridized TiO2 photocatalyst. The photodegradation results of Methylene Blue over graphene hybridized with TiO2 showed that the photocatalytic activity could be significantly enhanced under UV light irradiation. The structure between TiO2 and graphene as well as its effect on the photocatalytic activity were systematically investigated. The mechanism of the enhanced photocatalytic activity is based to the high migration efficiency and the inhibition of recombination of photoinduced electron-hole pairs. The graphene hydridization is proven to be a promising approach to develop highly efficient and stable photocatalysts under UV light irradiation.

Abstract: Nanocrystalline TiO₂ films were deposited on polymethylmethacrylate (PMMA) substrates by dip–coating process from colloidal anatase aqueous solutions. Microwave–hydrothermal process treating TiO₂ colloidal solutions was applied to enhance crystallization under a mild condition and avoid post–treatment. The as–prepared TiO₂ films were characterized and analysed by X–ray diffraction (XRD), UV–visible spectroscopy and atomic force microscopy (AFM). The photocatalytic degradation of Rhodamine B (RhB) under ultraviolet radiation was explored. Results show that pure anatase TiO₂ is achieved rapidly using microwave hydrothermal process. The TiO₂ suspension becomes uniformly disperse, stable and deposit-free after ultrasonic dispersion. The thin films deposited on unmodified PMMA substrates from the dispersive TiO₂ colloidal solution are dense, homogeneous, crack–free, without visible agglomerates and show high photocatalytic activity without post-treatment. Rhodamine B has been degraded over 99 % after 180 minutes under UV irradiation.

Abstract: In this paper, porous carbon has been used to carry TiO2 and TiO2-N by a sol-gel process. The effect of soaking time, heat treatment temperature, and heat treatment time on the carrying efficiency have been studied. XRD experiments indicated that TiO2 and TiO2-N crystallized in anatase and rutile with the ratio of 3∶2. SEM images showed that island-like TiO2 and TiO2-N particles with diameters in the range of 1-5um, the biggest size is about 10um, were evenly coated on the surface of the porous carbon.

Abstract: Formation mechanism of pores in undoped TiO₂ ceramics was investigated through defects chemistry and materials testing methods. The undoped TiO₂ ceramics samples were prepared from anatase TiO₂ powders by a traditional solid-state sintering method. Microstructure, chemistry composition and ionic valence of undoped TiO₂ ceramics were by SEM, EDS and XPS. Formation mechanism of pores was discussed by combination defect chemistry with materials structure measurement. The results show that there exist trivalence Titanium ion (Ti ³⁺) and grain boundaries absorbed oxygen in undoped TiO₂ ceramics samples. Both content of absorbed oxygen in grain boundaries and Ti ³⁺ concentration increase with sintering temperature increasing. There are much gas pores in grains and grain boundarties of undoped TiO₂ ceramics samples. The gas pores are mainly originated from lattice oxygen volatilization and oxygen vacancies segregation during high-temperature sintering.

Abstract: LBL (layer by layer) fabrication was based on the electrostatic attraction between the nanosheets host partial with electric charges and external object with opposite charges. By changing the property of the object, level defects can also be introduced, so that the nano-films with remarkable physica-chemical properties can be prepared. Tantalum oxide and cobalt oxide nano-films materials were made via LBL self-assembly technology in this work

Abstract: The self-cleaning glasses can be realized by coating the photoinduced super-hydrophilic Lu³⁺-doped TiO₂ thin films via innovative ultrasonic-sol-gel route. The composition, structure and performance of the as-obtained material were characterized by XRD, SEM, FT-IR and UV-vis. The super-hydrophilicity is assessed by contact angle measurement. Photocatalytic properties of these films are evaluated by degradation of methyl orange under UV irradiation. The results indicate that the crystalline phase composition of Lu³⁺ doped TiO² films is anatase, and the particle size is from 6 to 15 nm. In addition, Lu³⁺ doping can bring the red shift of the optical absorption edge of TiO². The films exhibit excellent super-hydrophilicity and photocatalytic properties after UV radiation and the hydrophilicity can maintain for a long time in the dark place, which favors greatly the self-cleaning function of the films.