Reparation of palladium membrane over anodic TiO<Subscript>2</Subscript> nanotube arrays on porous titanium

Pure palladium membrane has been successfully fabricated by photocatalytic deposition in fluoride electrolysis bath on TiO₂ nanotube arrays which was in situ grown by anodic oxidation on the surface of asymmetric home-made compressed porous titanium foils. Results of SEM, XRD and XPS show that the completed membrane is homogeneous and its thickness is about 0.5 μm. After 8 times thermal shock test, no shedding or crack is observed on this composite material, which shows the excellent hot crisp resistance.     

Electrical and optical properties of TiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript>:Fe thin films

TiO₂ and TiO₂:Fe thin films have been grown by electron beam evaporation and the influence of doping and heat treatment on their electrical and optical properties has been studied.     

Synthesis and characterization of polythiophene-modified TiO<Subscript>2</Subscript> nanotube arrays

The highly ordered and uniform TiO₂ nanotube arrays were fabricated by anodic oxidation method and PTh(polythiophene)/TiO₂ nanotube arrays electrode were obtained by electrochemical polymerization. X-ray powder diffraction (XRD) analysis confirmed the formation of TiO₂ phase. The morphologies and optical characteristics of the TiO₂ nanotube arrays were studied by scanning electron microscope (SEM), UV-Vis absorption spectra and Raman spectra. The results demonstrate that the PTh/TiO₂ electrode could enlarge the visible light absorption region and increase the photocurrent in visible region. The modified TiO₂ electrode with light-to-electric energy conversion efficiency of 1·46%, the short-circuit current density of 4·52 mAcm^− 2, open-circuit voltage of 0·74 V and fill factor of 0·44, were obtained.     

Preparation and photoelectrochemical characterization of WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> nanotube array electrode

WO₃/TiO₂ nanotube array electrode was fabricated by incorporating WO₃ with TiO₂ nanotube array via a wet impregnation method using ammonium tungstate as the precursor. TiO₂ and WO₃/TiO₂ nanotube arrays were characterized by field emission scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis. In order to characterize the photoelectrochemical properties of WO₃/TiO₂ electrode, electrochemical impedance spectroscopy, and steady-state photocurrent (i _ss) measurement at a controlled potential were performed in the supporting electrolyte containing different concentrations of glucose. The photoelectrochemical characterization results reveal that WO₃/TiO₂ nanotube array electrode possesses a much higher separation efficiency of the photogenerated electron–hole pairs and could generate more photoholes on the electrode surface compared with the pure TiO₂ nanotube array electrode. The i _ss for glucose oxidation at WO₃/TiO₂ nanotube array electrode is much higher than that at the pure TiO₂ nanotube array electrode.     

Preparation of K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript>/TiO<Subscript>2</Subscript> bio-ceramic on titanium substrate by micro-arc oxidation

K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings are prepared successfully by micro-arc oxidation on titanium substrate in pure KOH electrolyte solution. The coating is prepared at various applied current density (150–500 mA/cm²) and in KOH electrolyte with different concentrations (0.5–1.2 mol/L). The composition and surface morphologies of coatings are strongly dependent on the applied current density and the electrolyte concentration. On the condition of lower current density and electrolyte concentration, K₂Ti₆O₁₃ phase almost cannot be formed. The phase is mainly composed of rutile and K₂Ti₆O₁₃ with increasing current density and electrolyte concentration. The surface morphologies are composed of whiskers and porous structures. The ability of K₂Ti₆O₁₃/TiO₂ bio-ceramic films inducing apatite deposition is evaluated by soaking it in biological model fluids. The results show the K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings possess excellent capability of inducing bone-like apatite to deposit.     

TiO<Subscript>2</Subscript> nanotube arrays: hydrothermal fabrication and photocatalytic activities

Titanium dioxide nanotube arrays (TiO₂ NTAs) with rutile phase have been fabricated successfully via a two-step hydrothermal method. TiO₂ nanorod arrays (TiO₂ NRAs) are first hydrothermally grown on FTO substrate. Then the TiO₂ NTAs can be obtained by controlling the HCl concentration of the hydrothermal etching process. The TiO₂ NTAs have been characterized by X-ray diffractometer, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible spectroscope. Evolution of TiO₂ nanoarrays are accompanied by enhanced of the surface area and optical properties. Compared with TiO₂ NRAs, the prepared TiO₂ NTAs is more efficient in the photodegradation of methyl orange. These results reveal that the hydrothermal chemical etching provide a flexible and straightforward route for design and preparation of TiO₂ NTAs, promising for new opportunities in photocatalysts and other fields.     

Synthesis and characterization of nanocrystalline TiO<Subscript>2</Subscript> thin films

Nanocrystalline thin films of TiO₂ have been synthesized by sol gel spin coating technique Thin films of TiO₂ annealed at 700 °C were characterized by X-ray diffraction(XRD), Atomic Force Microscopy, High resolution TEM and Scanning Electron Microscopy (SEM), The XRD shows formation of tetragonal anatase and rutile phases with lattice parameters a = 3.7837 Å and c = 9.5087 Å. The surface morphology of the TiO₂ films showed that the nanoparticles are fine with an average grain size of about 60 nm. Optical studies revealed a high absorption coefficient (10⁴ cm^?1) with a direct band gap of 3.24 eV. The films are of the n type conduction with room temperature electrical conductivity of 10^?6 (Ω cm)^?1.     

Effect of high-temperature annealing on solid-state reactions in hydroxyapatite/TiO<Subscript>2</Subscript> films on titanium substrates

Hydroxyapatite (HA) films 0.5 and 1 μm thick with a 0.2-μm TiO₂ underlayer have been grown on titanium by rf magnetron sputtering. After annealing in an argon atmosphere at 900, 950, and 1000°C for 30 and 60 min, the phase composition, elemental composition, and surface morphology of the films have been determined by scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. The surface microstructure of the films is shown to depend on annealing temperature. X-ray microanalysis results indicate that, at HA layer thicknesses of both 1 and 0.5 μm, the Ca/P ratio increases with annealing temperature. In addition, the Ca/P ratio in the films produced under identical conditions depends on the film thickness. X-ray diffraction data indicate the presence of reaction intermediates. A TiO₂ interlayer in the HA/Ti system inhibits titanium oxidation, and the reaction intermediates forming during heat treatment improve the adhesion between the titanium and HA.     

Fabrication of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> double layer thin films with self-cleaning and photocatalytic properties

Transparent antireflective SiO₂/TiO₂ double layer thin films were prepared using a sol–gel method and deposited on glass substrate by spin coating technique. Thin films were characterized using XRD, FE-SEM, AFM, UV–Vis spectroscopy and water contact angle measurements. XRD analysis reveals that the existence of pure anatase phase TiO₂ crystallites in the thin films. FE-SEM analysis confirms the homogeneous dispersion of TiO₂ on SiO₂ layer. Water contact angle on the thin films was measured by a contact angle analyzer under UV light irradiation. The photocatalytic performance of the TiO₂ and SiO₂/TiO₂ thin films was studied by the degradation of methylene blue under UV irradiation. The effect of an intermediate SiO₂ layer on the photocatalytic performance of TiO₂ thin films was examined. SiO₂/TiO₂ double layer thin films showed enhanced photocatalytic activity towards methylene blue dye.     

SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> fibers from titanium-modified polycarbosilane

We developed a process for preparing SiO₂/TiO₂ fibers by means of precursor transformation method. After mixing PCS and titanium alkoxide, continuous SiO₂/TiO₂ fibers were fabricated by the thermal decomposition of titanium-modified PCS (PTC) precursor. The tensile strength and diameter of SiO₂/TiO₂ fibers are 2.0 GPa, 13 μm, respectively. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) measurements, the microstructure of the SiO₂/TiO₂ fibers is described as anatase–TiO₂ nanocrystallites with the mean size of ~10 nm embedded in an amorphous silica continuous phase.     

Dye-sensitized solar cells using TiO<Subscript>2</Subscript> nanoparticles transformed from nanotube arrays

Dye-sensitized solar cells (DSSCs) were fabricated using TiO₂ mesoporous layers obtained by very simple method—transformation of TiO₂ nanotube (NT) films grown by electrochemical oxidation to nanoparticle (NP) films. This transformation is based on thermal annealing of TiO₂ NT arrays formed by anodization of titanium foil in fluorine ambient. Performance of DSSCs fabricated with different size NPs was studied in the range from 35 to 350 nm. Highest nominal efficiency (9.05%) was achieved for DSSC with NP size 65 nm while the lowest nominal efficiency (1.48%) was observed for DSSCs with NP size 350 nm. The dependence of the solar cell parameters with NP size is discussed.     

Facile synthesis of blue anatase TiO<Subscript>2</Subscript> films by solvent evaporation method

With arousing interest in the preparation of defect rich TiO₂ films for several green energy applications, various methods have emerged in recent days. Herein, we report the properties of blue anatase TiO₂ films obtained by combined solvent evaporation and subsequent calcination. The X-ray diffraction and Raman studies indicated the formation of anatase TiO₂ films, while the field emission scanning electron microscopic images confirmed the distribution of spherical particles. X-ray photoelectron spectroscopic data revealed the presence of surplus Ti³⁺ ions and the associated oxygen vacancies. These defect related informations are further evident from the photoluminescence study. The optical study confirmed the extended absorption in the visible region of the blue TiO₂ films. These intrinsic defects play a major role in effective charge carrier separation and in tailoring the band gap absorption properties.     

Preparation of La<Subscript>2</Subscript>NiMnO<Subscript>6</Subscript> thin films on Pt/TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si substrates by pulsed laser deposition

Double perovskite La₂NiMnO₆ thin films were prepared on Pt/TiO₂/SiO₂/Si substrates by the pulsed laser deposition process, and the crystal structure and microstructures were investigated. The temperature and the oxygen pressure played the primary roles dominating the crystallization behavior and the morphology of La₂NiMnO₆ thin films. The well crystallized La₂NiMnO₆ thin films could be obtained at 873 and 923 K under all oxygen pressures investigated here, and the fine morphology was obtained under the oxygen pressures equal to or higher than 50 and 100 Pa, respectively, while phase constitution was significantly affected by the oxygen pressure for La₂NiMnO₆ thin films prepared at 1,023 K where the higher oxygen pressure led to the appearance of some secondary phase.     

Study of TiO<Subscript>2</Subscript> nanoparticle coatings by the sol-gel method for corrosion protection

We describe an economical method of deposition of TiO₂ coatings. The sol composition used for the deposition of nanocoatings is optimized, and the relationship between its pH value, water content, and the time of structurization is established. The potentiodynamic polarization, optical microscopy, and scanning electron microscopy are used for the evaluation of the corrosion resistance of specimens with coatings. The best protective properties are exhibited by the coatings obtained for a dip-coating rate of the specimen of 9 mm/sec, a period of drying of 3 h, and a rate of heating in the process of thermal treatment of 1°C/min, as well as after three consecutive procedures of dip coating. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 2, pp. 71–81, March–April, 2008.     

Fabrication and properties of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> composites

Composites in the form of precipitated powders, hybrid xerogels, and SiO₂ core/TiO₂ shell particles have been produced via hydrolysis of precursors (alkoxides and inorganic derivatives of titanium and silicon) and have been characterized by differential thermal analysis, X-ray diffraction, adsorption measurements, and macroelectrophoresis. The results demonstrate that heat treatment of the composites leads to crystallization of the titanium-containing component and, accordingly, reduces their specific surface area. Hydrothermal treatment enables the fabrication of materials in which TiO₂ nanocrystals are evenly distributed over an amorphous SiO₂ matrix.     

Photoinduced properties of nanocrystalline TiO<Subscript>2</Subscript> sol-gel derived thin films

In this paper, nanostructure TiO₂ thin films were deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction and Fourier transform infrared spectroscopy were used to determine film behaviour. The super-hydrophilicity was assessed by contact angle measurement. Photocatalytic properties of these films were evaluated by degradation of methylene blue under UV irradiation. The XRD pattern of TiO₂ powder samples confirmed the presence of polycrystalline anatase phase with a crystal size of 17 nm. The results indicated that UV light irradiation had significant effect on super-hydrophilic and photocatalytic properties of TiO₂ thin films.     

Hydrothermal synthesis of TiO<Subscript>2</Subscript> nano-particles using novel water-soluble titanium complexes

Hydrothermal treatment of a series of water-soluble titanium complexes resulted in the formation of TiO₂. Rutile, anatase or a mixture of both can be synthesized by varying the ligands. The titania obtained was composed of nano-sized particles with large specific surface areas. These TiO₂ powders exhibited high photocatalytic activity for NO _x decomposition. In particular, they demonstrated higher activity than P25 (Degussa) under visible-light irradiation.     

IR protection property and color performance of TiO<Subscript>2</Subscript>/Cu/TiO<Subscript>2</Subscript> coated polyester fabrics

Both humans and objects can emit infrared (IR) wavelengths which generate thermal emissions that can be detected with an IR camera. Therefore, highly IR reflective materials have been the subject of interest recently, for example, in achieving IR stealth. In this work, IR reflective coatings on polyester fabric in the form of a titanium dioxide/copper/titanium dioxide (TiO₂/Cu/TiO₂; TCT) sandwich-like structure are fabricated by using magnetron sputtering. The coated fabric samples are then examined by using an energy dispersive X-ray detector, a scanning electron microscope and an X-ray diffractometer. The reflection of IR wavelengths which range from 8 to 14 µm of the TCT coated fabric is evaluated. The bending stiffness, and mechanical and adhesion strengths of the coated fabric samples are also investigated. The results show that the TCT sandwich-like structure on the polyester fabric sputtered for 30 min with Cu which results in a Cu film of 200 nm in thickness is observed to have the maximum reflection of IR wavelengths. The color of the TCT coated polyester fabric samples sputtered for 5, 10, 20, and 30 min with Cu is green, yellow, brown and purple, respectively. The TCT coated fabric therefore has potential applications as IR protection textiles for military purposes.     

Enhancement of photoelectrochemical performance of CdSe sensitized seeded TiO<Subscript>2</Subscript> films

In this work, we highlight the effect of TiO₂ seed layer (SL) on the photoelectrochemical performances of CdSe/TiO₂ photoanodes (PAs). TiO₂ thin films were prepared by spin coating starting from a sol gel solution containing TiO₂ nanopowder, then sensitized with electrodeposited CdSe nanoparticles. Structural, optical and photoelectrochemical properties of the CdSe/TiO₂ PAs with and without the SL were investigated. Charge accumulation processes and charge transfer characteristics were identified by electrochemical impedance spectroscopy. The introduction of the compact TiO₂ SL was found to significantly increase the electron transport. The photocurrent density produced by the CdSe/TiO₂/SL PA reached 0.95 mA/cm², about two times higher than that performed by the CdSe/TiO₂ PAs. This enhancement might be attributed to a substantial decrease of the leakage current induced by a better crystallization of TiO₂ thin films as well as a higher sensitizing effect of the CdSe nanoparticles.