Papers by Keyword: Titania (TiO₂)

Abstract: Recently, zirconia has been considered as a suitable material for surface coating nanosized TiO2 for use as an electrode in a solar cell application. In this study, the TiO2 (P-25) coated ZrO2 was synthesized from P-25 TiO2 and coated with zirconium n-propoxide in the range of 2.5-50 wt.%. The surface of the TiO2 coated with ZrO2 were examined by X-ray diffraction (XRD) analysis, high resolution transmission electron microscope (HRTEM), which showed zirconia could coat onto the P-25 TiO2 surface. Any excess of zirconia has been deposited as separated particles. Peaks for tetragonal zirconia were observed from the XRD patterns in zirconia-coated P-25 containing more than 20 wt. % of zirconia after calcinations at 500 °C, 800 °C and 1300 °C. In addition, peaks of anatase could be observed from XRD patterns of the samples after calcination at 1300°C. The results show that coating zirconia onto the TiO2 grain surfaces may act to retard the phase transformation from anatase to rutile.

Abstract: To meet the need of optical fiber photoreactor designed by mechanism of TiO2 photocatalysis, nanometer TiO2 was coated on the surface of optical fiber by dipping nude fibers into an Al(H2PO4)3-contained TiO2 slurry. Effects of slurry conditions, including content of TiO2 and addition of Al(H2PO4)3 adhesive, on coating thickness and quality were determined. Coating process, especially the effect of coating times, was also concerned. Based on the experimental results, fitting slurry conditions and process parameters were suggested for obtaining high-quality TiO2 coating on optical fiber surface.

Abstract: TiO2 is one kind of semiconductor-based photocatalyst. TiO2 shows relatively high reactivity and chemical stability under ultraviolet (UV) light. However TiO2 is poor absorber of photons in the solar spectrum. In order to improve the absorption efficiency, the coatings of TiO2/ZnFe2O4, ZnFe2O4and TiO2 on ITO were prepared by dip coating method, their microstructure, surface properties, photocurrent and photo absorption are investigated in this paper. XRD results show that the phases on the composite coatings are mainly TiO2 and ZnFe2O4 and the main phase on ZnFe2O4 and TiO2 coatings is ZnFe2O4 and TiO2 respectively, the SEM results show that the coatings of TiO2 and TiO2/ZnFe2O4 are distributed evenly on the materials surface and the AFM results show that the grain size is about 20nm. The experimental results also show that the absorption wavelength of composite coatings of TiO2/ZnFe2O4 is 454nm, which is larger than that of TiO2 coatings (370nm). Under the irradiation of Xe lamp light, a photocurrent of 27µA/cm2 on the materials surface could be obtained.

Abstract: In order to meet a need of application of photocatalyst, a slurry dipping method was adopted for nano-TiO2 coating on optical fiber. Three slurry states were designed and their effects on coating quality were investigated. Experimental results showed that paste state may lead to surface cracks in coating. Both flocculent and dispersive slurry states can form high quality coatings whose coating microstructures are different, the former resulted in a loose and thicker coating and the later resulted in a dense and thinner coating, which supplied a basis for further study on effect of photocatalytic reaction and design of photocatalyst reactor.

Abstract: LiNO3-doped TiO2 thin films on glass-ceramics were prepared by sol-gel dip coating. The influence of LiNO3 addition on the phase transformation temperature was studied. The transformation temperatures of non-crystalline to anatase and anatase to rutile are originally 520°C and 880°C without the addition of LiNO3. By adding 5%LiNO3 the two transformation temperatures decrease to 440°C and 580°C, respectively. The average size of the particles was found to be around 40nm for the LiNO3- doped TiO2 film annealed at 600°C.

Abstract: The aim of the present study is to investigate the physical properties and antibacterial performances of Ag+-doped TiO2 film on stainless steel and effects of surface oxidization. In the experiment, the surface of stainless steel was been oxidized by heat treatment (550°C, 1 hour) before the Ag+-doped TiO2 (anatase) film being formed by sol-gel method. Sample A (filmed after surface oxidization), B (filmed without surface oxidization), C (only surface oxidization) and D (neither oxidized nor filmed) were respectively tested for corrosive resistance, abrasive resistance and adhesiveness, and the samples with different content of argentine was tested for antibacterial performance. Results: 1) Corrosion rates of sample A, B, C and D in 10% FeCl3 solution are respectively 1.65%, 1.87%, 2.02% and 3.28%, suggesting that the film has protected the stainless steel from the corrosion; 2) Scratching using a loaded (150 g) pin makes no crack on surface of sample A, while it results a slight scuffing on surface of sample B, suggesting that the surface oxidization has enhanced the abrasive resistance and adhesiveness of the TiO2 film, which may be due to the bridge-like function of the oxidation film; 3)Antibacterial performance is enhanced as the content of doping argentine increases, exceeding 90% when the argentine reached 3%, and the TiO2 film on the oxidized stainless steel performs better in antibacterial test than untreated one.

Abstract: The influence of La2O3 and CeO2 on a new class of polystalline ceramics with electrical properties based on TiO2 was investigated. The content of added La and Ce is in 1 at%, while that of the other addition is always maintained at a constant value. The disks were sintered at 13800C for 4 hours. La2O3 was found to precipitate at the grain boundaries, probably inducing electronic interface states that can trap charges at the TiO2-TiO2 interface and lead to significantly increase the nonlinear behavior. The values for α (» 4.2) and V1mA(» 26 V) support that finding. It was found CeO2 that as a dopant did not strongly influence the nonlinear values of the systems as did La2O3, indicating that it could have formed a solid-state solution with TiO2 in the grains, but did not segregate sufficiently at the grain boundaries. In present work, impedance analyzer, X-ray spectrometer, and scanning electron microscope (SEM) were used.

Abstract: Slim titanate naotubes was prepared from industrial coarse TiO2 powder by simple sonochemical-hydrothermal processing. The influences of ultrasonic irradiation on TiO2 precursors were investigated. The morphology and crystal structure of the products were characterized by TEM and X-ray diffraction, respectively. The typical products are long nanotubes around 8-10nm in out diameter. Both anatase and rutile TiO2 precursors can be transferred into titanate nanotubes in this sonochemical & hydrothermal processing.

Abstract: The three-dimensional (3D) photonic band gap material is a material that there exists a full photonic band gap in which waves are forbidden to propagate whatever the polarization or the direction of propagation. In order to obtain photonic bandgap in lower range, we focus on the fabrication of PBG materials of diamond structure with TiO2 powder mixed with SiO2. The inverse epoxy structure with periodic diamond lattices in millimeter order has been fabricated by stereolithographic rapid prototyping. TiO2 slurry was filled into the epoxy structure and then cold isostatic pressing was applied. After sintering at 700K for 5hrs, the epoxy was burnt out and the designed structure was maintained perfectly. The calculated band diagram shows that there exists an absolute photonic band gap for all wave vectors. The measurement of transmission from 10 to 20 GHz in <100> direction shows that a complete band gap is formed at about 14.7-18.5 GHz. The magnitude of the maximum attenuation is as large as 30 dB at 17 GHz.

Abstract: In the present in vitro study, osteoblasts proliferation, vitality and ultrastructure were investigated when cultured in the presence of silver-hydroxyapatite/titania nanoparticles (nAg_HA/TiO2) compared to HA nanoparticles (nHA) at various concentrations and cell culture without nanoparticles for up to 120 hours. Results confirmed the detrimental influences of both nAg_HA/TiO2 and nHA on osteoblast growth.Cell vitality was slightly higher during the earlier 24h, but after that was inhibited. Both cell proliferation and vitality by addition of nanoparticles were restricted with concentrations of nanoparticles increasing. However, the respiration rates by addition of nanoparticles were showed higher than that of the cell culture without nanoparticles. No remarkable ultrastructure changes were showed in the osteoblasts exposed nanoparticles. The difference in cell proliferation, vitality and ultrastructure between nAg_HA/TiO2 and nHA were insignificant. It was demonstrated that biocompatibility of nAg_HA/TiO2 is almost the same as nHA.