Papers by Keyword: Titanium Oxide

Abstract: Among the researches on preparation and test of nanostructured materials, titanium dioxide and zinc oxide have been the most frequent studied oxides. In order to extend their properties, composites have been prepared using three different methods: Polyol Method, Sol-gel Process and a combination of the two processes (hybrid process). Recent research showed best properties in composite materials than in pure oxides. In this work is presented the preparation and the structural characterization of ZnO-TiO₂ composite nanostructures to be tested for their performance in electrocatalysis and in further trial on photovoltaic cells.

Abstract: This study aims to investigate the microstructure and mechanical properties of Ti-ZrO₂ composites and ZrO₂/Ti functionally graded materials (FGMs) fabricated by spark plasma sintering (SPS). SPS has been conducted in a vacuum at 1400 oC under the uniaxial pressure of 30 MPa. Mechanical properties such as hardness and elastic modulus of Ti-ZrO₂ composites have been systematically investigated using micro-Vickers and nanoindentation. The experimental results demonstrate that the mechanical properties of Ti are dramatically improved by an addition of small amount of ZrO₂. There is almost no effect from the presence of Y₂O₃ in ZrO₂ on the hardness of Ti-ZrO₂ composites. ZrO₂/Ti FGMs have been successfully fabricated, and mechanical properties of the FGMs have been examined.

Abstract: Because bromic acid ion generated by the ozone processing of drinking water for sterilization is strong carcinogenic, there is a high possibility in persons health hazard. The titanium dioxide was reduced at 900-degree Centigrade by the gas atmosphere (CO or H₂). It was found that the concentration of the bromic acid ion in water was decreased at time when the reduced titanium oxide was added to water including the bromic acid ion. The bromic acid ion in water could be adsorbed by the titanium oxide reduced. In addition, it was suggested that the bromic acid ion could be decomposed into the bromide ion with low carcinogenic by using the photocatalitic function of titanium oxide under UV irradiation.

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 dioxide thin films have been prepared from tetrabutyl-orthotitanate solution and methanol as a solvent by sol-gel dip coating technique. The thermal properties of TiO2 gel were analyzed by thermogravimetry and differential thermal analysis (TG-DTA). Structural properties of TiO2 thin films at different heat treatment temperatures were analyzed by X-ray diffraction (XRD), Infrared Raman spectroscopy and scanning electron microscopy (SEM). The results show that the TiO2 thin films crystallize in anatase phase at 400 °C and the crystallinity of anatase phase was improved with increasing temperature. The TiO2 thin films crystallize into the anatase-rutile phase at 600 °C and further into the rutile phase at 800 °C. The photocatalytic performance of TiO2 film was tested for the degradation of 2×10-5 mol/L Rhodamine B. The degradation of Rhodamine B solutions reached 0.9×10-5 mol/L after irradiated for 8 h under UV light. The TiO2 thin film exhibited relatively high photocatalytic activity towards degrading Rhodamine B.

Abstract: We report on an experimental study on transparent nanoporous titanium oxide films on glass substrates using an anodization process. Ti thin films of 50-90 nm have been deposited on glass substrate by dc sputtering (1.8210-3 Pa, 100 W) followed by a thermal treatment of 500°C for 30 min. in order to improve the adhesion to the glass substrate. Then an anodization process was applied in order to obtain TiO2 thin nanoporous layers using a cell consisted of three electrodes and aqueous electrolyte solution of 1% NH4F concentration, monoethyleneglycol and DI water. After anodization the samples were annealed at 450°C for 45 min using nitrogen gas. The layers have a nanoporous structure with pore dimensions in the range of 50-80 nm. FTIR and micro-Raman spectroscopy were used to identify the crystalline phase of the TiO2 layers. Raman scattering spectra clearly identify the anatase phase on the basis of Eg modes at ~ 146 cm-1 of the TiO2. The FTIR spectrum showed only the peak at 614 cm−1 which can be associated with the characteristic vibrational mode of TiO2 anatase. The optical properties of TiO2 thin films have been determined by ellipsometric measurements in the spectral range (0.2-0.8 μm) and a value of 2.41-2.45 was obtain for refractive index at 632 nm. Spectrophotometric measurements showed a transmittance over 70% and an optical band gap of 3.3-3.5 eV was determined.

Abstract: In this study, anodizing of Ti in the various concentration of H₃PO₄ aqueous solutions gave TiO₂ films, and the osteoconductivity was examined using in vivo testing. In the anodizing treatment, anodizing potential of < 200 V was applied to the Ti substrate in H₃PO₄ aqueous solutions with the concentration of 0.1 to 14 M at 298 K. The coatings were evaluated using SEM, XRD, FT-IR and XPS. In in vivo testing, the coated samples were implanted in the rats’ tibia for 14 d to evaluate the osteoconductivity. In H₃PO₄ aqueous solutions with any concentration, anatase-type TiO₂ films were obtained on the Ti substrate by anodizing. The crystallinity of anodized TiO₂ films depended on the concentration of H₃PO₄ and sparking. In less than 2 M H₃PO₄, anatase with high crystallinity was formed. On the other hand, anodizing with sparking in more than 4 M H₃PO₄, gave low crystallinity anatase film. In in vivo testing, osteoconductivity of the coatings with low crystallinity anatase was much higher than that with high crystallinity.

Abstract: Using resistive heated method, Ti films of different thickness ranging from 10 to 200 nm were deposited and post-annealed at a temperature of 473K with a flow of oxygen. The optical properties were measured by transmission spectroscopy in spectral range of 200-2500 nm. The optical functions were obtained from the Kramers-Kronig analysis of the reflectivity curves. The effective medium approximation analysis was employed to establish the relationship between the nano-structure and Effective-Media Approximation (EMA) predictions.It was found the temperature of deposition and thefilm thickness play important roles in the nano-structure of the film and cause significant variations in the optical behaviour of thin Titanium oxide films.

Abstract: Novel phthalocyanine derivative and azo derivative have been synthesized as photosensitizers for the dye-sensitized solar cells (DSSCs). We used sol-gel method to prepare the titanium oxide (TiO2) membrane electrode of the DSSCs. The crystalline phase and surface morphology of TiO2 were characterized by using X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) to investigate the effects of processing parameters on the films characteristic, microstructure and thickness. The performance of DSSCs was characterized by using electrochemical impedance spectroscopy (EIS) and current-voltage curve analysis. The sensitizing properties of phthalocyanine derivative, azo derivative and mixed dyes were studied, and it was found that the cell consisted of mixed dyes generated the highest power conversion efficiency () of 2.3 %, short circuit photocurrent density (Jsc) of 13.6 mA cm-2, open circuit photovoltage (Voc) of 0.46 V and fill factor (FF) of 0.37 under simulated AM 1.5 irradiation (100 mW cm-2) with a active area of 0.25 cm2.

Abstract: In this work, the resistance to scratch and wear (pin-on-flat) tests of five different porous TiO₂ films were compared. Such tribological tests were carried out under dry conditions. The coatings were electrodeposited on commercially pure-Ti by anodic oxidation method in different electrolyte solutions at constant voltages. The scratch tests were conducted by applying increasing normal loads up to 400 mN. The coefficient of friction (COF) varied from 0.2 up to 0.5, and increased at larger penetrations depths. When the electrolyte concentration was changed from 0.5 into 1.0M H₂SO₄, the COF slightly decreased. Scanning electron microscopy indicated that the coatings produced in H₂SO₄/150V and Na₂SO₄/100V did not have their substrates revealed. In addition, the samples anodized in H₂SO₄/150V had the highest elastic recoveries. Therefore, such coatings seem to be more resistant to scratch tests than the others. The wear tests were carried out with Berkovich tip as counter-face under constant normal loads of 10 mN in 10 forward-backward cycles. The coatings deposited in H₂SO₄/150V had the lowest wear volume rates. The findings suggest that the porous Ti oxide coatings electrodeposited above their rupture voltages are more suitable to both scratch- and wear-resistance compared to those prepared at the lowest voltage (H₂SO₄/100V).