Papers by Keyword: TiO₂ Film

Abstract: This work is focused on the study of photosensitive structures based on porous Si and film TiO₂, which are promising for solar energy. For numerical simulation of the transportation and accumulation of charge carriers in the considered heterostructure, the drift-diffusion approximation of the semiclassical approach was proposed. A device scheme of a solar cell model based on TiO₂/porous-Si/Si heterostructures is proposed. Production of photoconverters of solar cells based on the TiO₂/porous-Si/Si heterostructure can be carried out according to the standard method supplemented by additional technological operations. Ohmic contacts are formed in the upper and lower parts of the structure above the TiO₂ and Si layers. The strip system of contacts is a contact grid, with hatching, the surface coefficient should not exceed 5%. The thickness of the applied layer of photoresist should be 1 μm. Using the PC1D program, the light characteristics of the fabricated structure were calculated (open circuit voltage V_OC, short circuit current I_SC, fill factor FF and efficiency η), and current-voltage characteristics were plotted. The influence of the thickness and doping level N_d and N_a of porous Si and TiO₂ layers on the productivity of a heterojunction solar cell TiO₂/porous-Si/Si was studied in order to obtain a device with a good conversion efficiency. It was found that the energy conversion efficiency of a TiO₂/porous-Si/Si solar cell can reach 22.5 %. Based on the optimized simulation conditions, it was found that the maximum solar cell efficiency is achieved at thicknesses of 100 and 200 nm and donor concentration of N_d=1∙10¹⁷ cm^-3 and acceptor concentration of N_a=1∙10¹⁸ cm^-3 for TiO₂ and porous Si buffer layer, accordingly.

Abstract: Brookite is the least known titanium dioxide (TiO₂) crystallographic phases compare to anatase and rutile. In a sol-gel process, very few works are devoted on synthesizing pure brookite as a thin film coating and usually brookite co-exist with anatase and rutile as a byproduct. This study is performed as an attempt to produce brookite thin film coating via sol-gel dipping method. In this study, the influence of catalyst type on TiO₂ phases, morphology and grain size were investigated. Hydrochloric acid (HCl) is used for an acid catalyst and sodium hydroxide (NaOH) is used as base catalyst. All of the TiO₂ films were deposited on a glass substrate and heated at four different temperatures of 400°C, 450°C, 500°C and 550°C for 3 hours. X-ray diffraction (XRD) is employed to analyze the phases and the grain size acquired. Images on the surface morphology are obtained with Scanning Electron Microscope (SEM). Results showed that brookite phase exist only for base catalyst with a grain size of 27.40 nm for all of the selected temperatures except at 550°C. SEM results revealed that the surface morphology of the deposited TiO₂ film with base catalyst comprised of agglomerated particle networks. In contrast, the surface morphology of the deposited TiO₂ film with acid catalyst seems more compact and uniform with an XRD pattern of amorphous-like characteristic having grain size of less than 3 nm.

Abstract: A dense TiO₂ film was fabricated on the titanium surface using the anodization technique. Surface morphology and phase structure of anodic TiO₂ film were investigated before and after the hydrothermal exposure at 160 °C for 24 h. The hydrothermal solution was 3.5 wt% NaCl solution and the films were either immersed in NaCl solution or exposed to water vapor during the exposure. It was found that the as-prepared anodic TiO₂ film consisted primarily of amorphous oxides and exhibited a relatively smooth surface. After the hydrothermal exposure, lots of rod-like crystals were formed on the solution-immersed film, while aggregated fine nanoparticles emerged on the vapor-exposed one. Thin film X-ray diffraction analysis indicated that the hydrothermal exposure transformed amorphous oxides into crystalline anatase. The corrosion behavior investigation showed that the structural transition of anodic TiO₂ film during the exposure reduced the corrosion resistance of anodized titanium greatly.

Abstract: Abstract: The Co²⁺ doped TiO₂ film(Co-TiO₂) was prepared by in-situ growing on the pure Ti plate substrate in the electrolyte solution of Na₃PO₄ containing CoSO₄·7H₂O by micro-arc oxidation (MAO) process. The effect of the amount of CoSO₄·7H₂O adding into the electrolyte solution on structure of Co-TiO₂ and its activity of photo-catalytic hydrogen production had been studied. It was found that the characteristic peak(101) of anatase phase and the characteristic peak(002) of rutile phase appeared and the red shift of absorption edge occurred for Co-TiO₂ films when adding CoSO₄ into the electrolyte solution. It was shown from experimental results that the highest hydrogen production rate was 0.33 μmol/ h·cm² over the above-prepared Co-TiO₂ in CoSO₄·7H₂O content of 8.7 g/L.

Abstract: Nitrogen-doped nanoTiO₂ sol was prepared by sol-gel method. The obtained sol was coated onto glass substrates by spin coating method, followed by drying at low temperature and calcined at high temperature. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible spectra (UV-Vis) . The XRD spectra showed that the crystal type of N-doped TiO₂ films was anatase. The SEM images showed that the surface of films were flat without obvious crack and average diameter was about 20 nm. The UV-Vis spectra showed that the absorbance of N-doped TiO₂ films at ultraviolet region increased. N-doping caused photocatalysis response wavelength to turn longer. The photocatalytic activity of N-doped TiO₂ films was researched through the degradation experiment of methyl orange under ultraviolet light. Higher photocatalytic degradation efficiency was exhibited compared to the pure TiO₂ films.

Abstract: TiO₂ films were prepared on glass and 316L stainless steel (316L SS) using hydrothermal method. The microstructures of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It indicated that the films crystallized as anatase phase with mirror-like surface morphology. The optical properties of the TiO₂ film were studied by Ultraviolet Visible Spectroscopy (UV-Vis). The results showed that the film was transparent in visible range. The cut-off point of the sample was red-shifted after annealed treatment. The corrosion resistance of the film was evaluated by using Tafel polarization curve in simulated body solution. The corrosion current density was decreased from 8.556 μA/cm² (316L SS) to 1.421 μA/cm² (TiO₂ film/316L SS). While, the corrosion potential was increased from-0.402 V (316L SS) to-0.325 V (TiO₂ film/316L SS). The 316L SS with TiO₂ film has better corrosion resistance.

Abstract: The Ni²⁺ doped TiO₂ film (Ni-TiO₂) was produced in-situ on the pure Ti plate substrate in the electrolyte solution of Na₃PO₄ containing of Ni (Ac)₂ by micro-arc oxidation process (MAO). The effect of Ni (Ac)₂ content on structure and H₂ production activity of Ni-TiO₂ had been investigated. It was found that the characteristic peak (101) of anatase phase for Ni-TiO₂ decreased gradually without the peak of Ni and the red shift of its absorption edge appeared with the increase of Ni (Ac)₂ content. It was showed from experimental results that the highest H₂ production rate was 0.31 μmol/ h·cm² over the above-prepared Ni-TiO₂ at Ni (Ac)₂ content of 5 g/L.

Abstract: TiO₂ sol was doped with SiO₂ and modified by adding PEG. Using the sol the self-cleaning antireflective films were prepared with dip-pulling method. Field emission scanning electron microscope (FESEM) test results showed that the TiO₂-SiO₂ film surface distributed a large number of pores and grooves. The visible spectrophotometer testing found that the transmittance showed a decreasing trend with the increase of TBTT: TEOS ratio. Meanwhile, the photo-catalytic efficiency showed an increase firstly and then decreased with the TBTT: TEOS ratio increasing. When the ratio of TBTT: TEOS was 1:5, the films transmittance and the photo-catalytic efficiency can reach up to 97.1% and 13.5% respectively. The mechanisms on the transmittance and photo-catalytic activity of PEG-modified TiO₂-SiO₂ films were studied. It was found that PEG-modified TiO₂-SiO₂ films have higher porosity, transmittance and hydrophilicity than pure TiO₂ film. Furthermore, photo-catalytic activity of the TiO₂-SiO₂ film was enhanced.

Abstract: The titanium sol was prepared by depositing the organic titanium on glassy carbon electrode surface. Electrophoresis time and the applied voltage as well can markedly influence the electrochemical behavior of the nanoTiO₂ film. In contrast with bare glassy carbon electrode, the nanoTiO₂ film on glassy carbon electrode had a good electrocatalytic activity to dopamine (DA) and uric acid (UA) in PBS solution. The result showed that there was a linear relationship between the oxidation peak currents and the concentration of DA from 8.0×10^-6 to 4.0×10^-4 mol·L^-1 by differential pulse voltammetry (DPV) and there was a linear relationship between the oxidation peak currents and the concentration of UA from 8×10^-6 to 1.0×10^-3 mol·L^-1. This modified electrode was quite effective to detect DA and UA in simultaneous determination of these species in a mixture.

Abstract: Homogeneous and transparent lanthanum La-doped TiO2 nanocrystalline thin films were deposited on pure titanium substrates by sol gel dip coating method. The surface structures, morphologies and electrocatalytic activities of the prepared nano-TiO2 film electrodes were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Cyclic voltammetry (CV). The results demonstrated that the optimum molar proportion of La was 0.5%. This optimum La-nanoTiO2 electrode (Ti/0.5%La nano-TiO2) showed a higher electrocatalytic activity than the undoped nano-TiO2 electrode (Ti/nano-TiO2)