Fabrication and characterization of sputtered titanium dioxide films

TiO₂ thin films were prepared under various conditions by using a reactive RF sputtering technique. The structural, optical and electrical characteristics of the films have been investigated. All as-deposited films were amorphous. After annealing at T > 673 K, the crystallinity of the observed tetragonal anatase phase appeared improved. The optical band gap, determined by using Tauc plot, has been found to amount to 3.38 ± 0.03 and 3.21 ± 0.03 eV for the direct and indirect transition, respectively. Also the complex optical constants for the wavelength range 300-2500 nm are reported. Using the two-point probe technique, the dark resistivity has been measured as a function of the film thickness, d. The resistivity, ρ, of the samples has been found to decrease markedly with increasing thickness, but only for d < 100 nm. The behaviour of ρd versus d was found to fit properly with the Fuchs and Sondheimer relation with parameters ρ_o = 4.95 × 10⁶ Ω cm and mean free path, l = 310 ± 2 nm. The log ρ versus 1/T curves show three distinct regions with values for the activation energy of 0.03 ± 0.01, 0.17 ± 0.01 and 0.50 ± 0.02 eV, respectively.     

X-ray photoelectron spectroscopy characterization of composite TiO2–poly(vinylidenefluoride) films synthesised for applications in pesticide photocatalytic degradation

X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide–poly(vinylidenefluoride) (TiO₂–PVDF) films developed for applications in the photocatalytic degradation of pollutants.

The composites were deposited on glass substrates by casting or spin coating from TiO₂–PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO₂–PVDF surface composition were used to optimize preparation conditions (composition of the TiO₂/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability.

The use of spin-coating deposition and the increase of TiO₂ amount in the DMF suspensions were found to improve the titanium surface content, although high TiO₂/PVDF ratios led to film instability. PVDF–TiO₂ films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO₂ and the role played by the PVDF film during the degradation process.     

Reaction of silyl ketene acetals with epoxides: a new method for the synthesis of γ-butanolides

Titanium tetrachloride promoted reaction of silyl ketene acetals with epoxides, followed by acidic work-up, affords butanolides in moderate/good yields. With epihalohydrins the reaction is regioselective and occurs at the less substituted end of the epoxide; the γ-haloalkyl-γ-butanolides thus obtained can be further transformed into various products.     

Growth process of TiC clusters from Ti nanoparticles with evaporated carbon layer

Titanium carbide formation by the solid–solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 nm it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles.     

How I Do It: Miniplate Reconstruction of the Lateral Thyroid Lamina: One-Stage Restoration of Voice After Teflon Granuloma Resection

This case report describes a one-stage technique for long-term voice restoration and laryngeal reconstruction in the treatment of Teflon (Dupont, Wilmington, Delaware) granuloma. A patient who presented with severe dysphonia underwent resection of a Teflon granuloma via a lateral laryngotomy. A pedicled strap muscle flap was used to reconstruct the paraglottic space. The muscle flap was positioned through the lateral laryngotomy with direct endoscopic visualization of the endolarynx to ensure correct vertical positioning and medialization of the vocal fold. The muscle flap was secured in this position with suture fixation. The trapdoor piece of cartilage that was elevated to create the window in the lateral thyroid lamina was repositioned over the pedicled muscle flap and reinforced with a titanium miniplate, which was secured to the remaining thyroid cartilage. The patient had excellent voice results and has not required revision or augmentation. Reinforcement of the lateral thyroid lamina using titanium miniplate fixation helps to stabilize the muscle pedicle flap and the position of the vocal fold, in this case resulting in good long-term voice results after a single-stage reconstruction.     

Shape-controlled synthesis of nanocrystalline titania at low temperature

The interesting shape (shuttle-like, sphere with needles, uniform particles) rutile titania were prepared by the hydrolysis of TiCl₄ in high acidic aqueous solution in the absence or presence of PEG-1000. PEG-1000 acted as dispersant, which could control the shape and size of the precipitate of titania. As a result, shuttle-like nanocrystalline appeared and the aggregation was improved with the increase of the amount of acid and the decrease of the concentration of TiCl₄ in the absence of PEG-1000. Uniform nanoparticles were obtained in the presence of PEG-1000 and the diameter of the particles decreased with increasing the amount of PEG-1000. This process simplification will lower production cost and make continuous process possible. The products were analyzed using X-ray diffractometer, transmission electron microscopy.     

WOx/TiO2光催化剂的可见光催化活性机理探讨

采用磁控溅射技术在用浸渍提拉法制得的TiO2薄膜上，溅射氧化钨层,通过气相反应中光催化降解二甲苯的实验表明，WOx/TiO2薄膜具有可见光活性.通过UV-Vis吸收光谱、X射线光电子能谱（XPS）等方法对其可见光活性的机理进行探索.UV-Vis吸收光谱表明WOx,TiO2对可见光响应的范围有一定的扩展,吸收强度增加.XPS表明WOx/TiO2薄膜表面形成了明显的W杂质能级和Ti缺陷能级,这是WOx/TiO2在可见光范围有一吸收的主要原因,也是光催化剂具有可见光活性的必要条件之一，同时杂质能级的存在使半导体费米能级上移,载流子增加,光催化效率提高.     

钛铁矿中钛的测定

利用钛铁矿能显著吸收微波的介电特性，采用家用微波炉，在微波辐照下，用浓磷酸消解矿样，并用氧化还原滴定法测定钛的含量，试验结果表明，该方法能快速分解矿样，测定结果准确，与传统分析方法比较，该法具有简便、快速、低耗、适应大批量样品分析等优点。还对钛铁矿的结构作了X-射线衍射分析。     

The relative reactivities of various unsaturated compounds towards diisopropyloxy(η-cyclopentene)titanium

Competition experiments were performed by adding pre-formed solutions of diisopropyloxy(η²-cyclopentene)titanium in diethyl ether to various mixtures of unsaturated compounds at low temperature, establishing the following reactivity scale: aldehyde > nitrile > ketone > terminal alkyne > internal alkyne > terminal alkene > ester, carbonate.     

Ein Beitrag über Oxide vom Typ AMO4 (A = Ti3+, Cr3+; M = Nb5+, Ta5+)

A Contribution on Ternary Oxides of the AMO₄-Type (A = Ti³⁺, Cr³⁺; M = Nb⁵⁺, Ta⁵⁺ ) CrNbO₄, CrTaO₄, TiNbO₄, and TiTaO₄ were prepared by CO₂-laser technique. X-ray single crystal investigations show a random distribution of the metal ions in Rutil type structure, space group D–P4₂/mnm. Calculations of the free energy of reaction between Ti₂O₃ and Nb₂O₅ show higher stability of TiO₂ beside NbO₂. In TiNbO₄ both metals exhibit the oxidation state +4.