Pure Titania Research Articles

Effect of mechanical surface treatments on the high temperature oxidation of pure titanium: the role of nitrogen

The mechanically treated high temperature (700°C) oxidation of commercially pure titanium was studied for long exposures (3000 h). The treatments studied here are the shot-peening and the laser-shock peening. The mass gain was measured by discontinued weighing. SEM and Raman imaging revealed strong differences between laser-shock peened, shot-peened and untreated oxidized samples. The laser treatment leads to thin compact and protective oxide layer while the shot-peened and untreated samples exhibit cracked oxide layers. The distribution of light elements like carbon, oxygen and nitrogen was revealed by Ion Beam Analysis. The presence of nitrogen located at the interface between the oxide scale and the metal was revealed on laser-shock peened samples. It is supposed the nitrogen slows-down the oxygen diffusion into the metal. The extent of the oxygen-enriched metal is also smaller on LSP samples, which improves the ductility of titanium.

Photoelectric Properties of a Nanocomposite Derived from Reduced Graphene Oxide and TiO2

The properties of a nanocomposite derived from reduced graphene oxide and TiO2 obtained by hydrothermal synthesis were investigated. Nanocomposite formation was confirmed by SEM as well as Raman and IR spectroscopy. The introduction of 10% rGO into the nanocomposite leads to considerably lower resistance than found for TiO2 itself. The combination of enhanced electrotransport, optical, and adsorption parameters of these nanocomposites leads to better photoelectrochemical characteristics than for pure titanium dioxide.

Влияние наночастиц серебра на фотодетектирующие свойства нанокомпозита TiO-=SUB=-2-=/SUB=-/оксид графена

The effect of silver nanoparticles on the optoelectronic and photoelectric properties of a nanocomposite material based on graphene oxide (GO) and TiO2 was studied. The data of electron microscopy and Raman spectroscopy have shown that, the formation of a TiO2-GO nanocomposite material occurs during hydrothermal synthesis. The absorption spectrum of the nanocomposite is shifted to the long-wavelength region relative to the absorption of TiO2. The current–voltage characteristics of photodetector based on TiO2-GO nanocomposite films were increased by 2 and 7.5 times relative to pure titanium dioxide without and with the addition of Ag nanoparticles, respectively. The optoelectronic parameters of the devices were also increased, which is associated with growth in the mobility of charge carriers in nanocomposite films.

In Ukrainian

The spatial and electronic structures of cluster (Ti13ZrH22O39, Ti13ZrN2H22O37, Ti13ZrN2H22O36 ) which model pure titanium dioxide (anatase modification) and that with zirconium impurities as well as pure zirconium composition (ZrO2 content), are considered. The theoretically calculated infrared, electron and X-ray spectra of these clusters are analyzed. The spectra of small particles of zirconium are shown to be highly characteristic of the spectral transition energies and uniquely correspond to their spatial structures. It is shown that in the photoelectron spectra the energy level of Zr 3p is characteristic and its intensity in the RF spectra and position on the energy scale is slightly dependent on the chemical environment of the zirconium atom. The calculated oscillation frequency in the IR spectra of the considered clusters was determined to be “breathing” vibrations of Zr – O bonds (538 cm– 1) and stretching vibrations of Zr = O bonds (955 cm– 1). It is determined that the search for an approximate solution by imposing symmetry on a real object is appropriate, because the symmetry of the cluster corresponds to the real symmetry of the crystal. The results of the studies are compared with the properties of molecular models for the bulk and surface phases of titanium dioxide, calculated by the method of electron density functional theory (DFT). It is found that the results of spectral studies of the properties of samples of titanium dioxide can clearly indicate the presence of zirconium impurities in them, or their absence.

Promoting Photocatalytic Cleaning Efficiency of Textile Finishing Solutions with Nanoboron as a p‐Type Dopant

AbstractBoron is a commonly used p‐type dopant for semiconductor and photonic applications. In this study, standard photocatalytic titanium dioxide (TiO2) particles were doped with nanosized boron particles and coated on textiles to bring the photocatalytic light intensity closer to the visible light range. Boron/titania nanoparticle composites were initially prepared in DI water solutions and studied for their photocatalytic response through a statistical central composite design. To determine the most effective titania and nanoboron particle blend for photocatalytic textile coating, absorbance and stain bleach analyses were performed by UV light exposure. The performance of the composite particles at the optimal concentration has also been evaluated in the finishing solution and compared with the performances of the pure titania particles. It was found that the textiles coated with 0.08 wt% anatase doped with 0.16 wt% nanoboron as a p‐type dopant provided improvement in self‐cleaning ability under the visible light range in the DI water environment. Energy band gap calculations further verified the nanoboron‐doped titania blend to have a lower energy barrier as compared with the 0.1 wt% anatase in agreement with the photocatalytic activity improvements. Nanoboron is shown to be a strong candidate as a p‐type dopant to titania for photocatalytic textile coatings.

The influence of nanoporous anodic aluminum oxide on the initial adhesion of Streptococcus mitis and mutans.

The use of nanoscale surface modifications offers a possibility to regulate the bacterial adherence behavior. The aim of this study was to evaluate the influence of nanoporous anodic aluminum oxide of different pore diameters on the bacterial species Streptococcus mitis and Streptococcus mutans. Nanoporous anodic aluminum oxide (AAO) surfaces with an average pore diameter of 15 and 40 nm, polished pure titanium and compact aluminum oxide (alumina) samples as reference material were investigated. S. mitis and mutans were evaluated for initial adhesion and viability after an incubation period of 30 and 120 min. After 30 min a significantly reduced growth of S. mitis and mutans on 15 nm samples compared to specimens with 40 nm pore diameter, alumina and titanium surfaces could be observed (p < .001). Even after 120 min incubation there was a significant difference between the surfaces with 15 nm pore diameter and the remaining samples (p < .001). AAO surfaces with a small pore diameter have an inhibitory effect on the initial adhesion of S. mitis and mutans. The use of such pore dimensions in the area of the implant shoulder represents a possibility to reduce the adhesion behavior of these bacterial species.

Effects of water-to-methanol ratio on the structural, optical and photocatalytic properties of titanium dioxide thin films prepared by mist chemical vapor deposition

The mist chemical vapor deposition method was used to synthesize pure anatase phase titanium dioxide thin films on glass substrates. The effects of water-to-methanol ratio on the structural, optical and photocatalytic properties of titanium dioxide thin films were investigated. Titanium dioxide films deposited by mist chemical vapor deposition were always anatase phase independent of the various water-to-methanol ratios investigated. From the GIXRD results, it was found that with the decrease of the water-to-methanol ratio, the growth of {001} facets was enhanced. The uniformity of the synthesized titanium dioxide thin films was characterized by field emission scanning electron microscopy and atomic force microscope. The highest surface roughness and surface area was obtained with a water-to-methanol of 0 %, corresponding to undiluted 100 % methanol. The transmittance of all anatase titanium dioxide films was higher than 70 % in the visible region. By decreasing the water-to-methanol ratio, the photocatalytic efficiency of the anatase titanium dioxide films exhibited an increasing trend. Due to the highest ratio of {001} facets and maximized surface area, the titanium dioxide films deposited with a water-to-methanol of 0 % have the optimum photocatalytic efficiency, with a high potential for photocatalyst applications.

Synthesis of pure and C/S/N co-doped Titania on Al mesh and their photocatalytic usage in Benzene degradation

Pure and co-doped Titania thin films were prepared on aluminum substrates through the sol-gel method. The co-doped sample showed higher photocatalytic activity on benzene degradation compared to pure TiO2 under visible light illumination. XRD results showed the anatase phase for both TiO2 and co-doped TiO2 lattices with an average crystalline size of 12.9 and 10.4 nm, respectively. According to the UV-visible absorption spectra results, co-doped Titania showed higher visible light absorption compared to pure Titania. The synergistic effect of dopants caused a redshift to visible light absorption and also the lifetime of the photogenerated electron-hole were increased by induced electron levels in Titania lattice. The novelty of this study is the reactor’s specific design. We employed Al mesh as thin film substrate for 3 main reasons, first, the large surface area of the Al mesh causes to increase specific surface area of the photocatalysts, also it is a formable substrate which can be engineered geometrically to decrease the shadow spots so the thin films will receive the highest light irradiation. Also, the Al mesh flexibility facilitates the procedure of reactor design to reach a minimum pressure drop of airflow while it is installed in the air conditioners or HVAC systems.

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

The synthesis and characterisation of Ti–Zr mixed oxides containing 1 to 10 wt.% of Zr is herein reported. In addition, the samples were tested as photocatalysts in the generation of hydrogen from aqueous methanol solutions. The solids were prepared by sol-gel and then characterised by X-ray diffraction, high resolution electron microscopy, X-ray photoelectron spectroscopy, physisorption of nitrogen, scanning electron microscopy, UV-vis and Raman spectroscopies. The results show the presence of anatase as a predominant structure and the oxides present larger specific surface areas than that of pure titania. A maximum value of 168 m2/g was determined for the sample with 5 wt.% of zirconium. The calculated band gap energies varied from 3.05 to 3.15 eV. It was observed that the greater the zirconium content in the solid, the higher the generation rate of hydrogen when testing the Ti–Zr solids as photocatalysts. Under our experimental conditions, the best catalyst, Ti–Zr oxide with 10 wt. % Zr, showed a production rate of 2100 μmol of H2/h which was about tenfold higher than that observed for pure titania.

One-pot hydrothermal synthesis and characterization of magnetic nanocomposite of titania-deposited copper ferrite/ferrite oxide for photocatalytic decomposition of methylene blue dye

The pure titania (TiO2) and the heterogeneous ternary magnetic nanocomposite of copper ferrite/ferrite oxide (CuFe2O4/Fe2O3) deposited by titanium dioxide (TiO2) were fabricated using a facile one-pot hydrothermal synthesis for the photocatalytic decomposition of methylene blue (MB) dye, under visible light. The nanocomposite was encoded as TCF in this work, where T stands for TiO2, C for CuFe2O4 and F for Fe2O3. Various techniques such as powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, diffuse reflectance spectroscopy, nitrogen physisorption, and vibrational sample magnetometry (VSM) were used to characterize the prepared samples. The PXRD data showed that the samples had pure anatase structure and the average crystal size of anatase TiO2 in the pure titania and ternary nanocomposite were calculated 147 Å and 135 Å, respectively. The nitrogen physisorption analysis data showed that the pore diameter was increased from 10.6 nm in pure titania to 16.0 nm in TCF. The pore volume was also increased from 0.316 in titania to 0.383 cm3/g in TCF sample. It also increased the typical magnitude of the mesopores’ diameter and volume per weight but it reduced the specific surface area of the samples. The VSM analysis of the ternary nanocomposite showed a considerable magnetic property of the sample (1.99 emu/g), qualifying it as a paramagnetic material. The photocatalytic decomposition efficiency of MB reached 77% and 68% in the presence of pure titania and TCF ternary nanocomposite, after 240-min exposure by the visible light. Active species trapping experiments showed that the major active species responsible for the photodecomposition of MB in the presence of TCF are {text{O}}_{2}^{ cdot - } radicals and holes (h+).

Spectrally extended, near-surface refractive index determination: atomic layer deposited TiO2 on Si.

The optical performance of very thin films has always been difficult to measure, and it has been a gray area due to interface and coating imperfections. Atomic layer deposition has produced pinhole-free, continuous, and extremely pure Titania films, with precise control at monolayer level, on native oxide/Si substrates, whose atomic force microscopy imaged nano-topology is approximately followed. For interface probing, the Abelès method is extended to the visible spectrum, and Cauchy dispersion curves are fitted to the refractive index experimental data, showing excellent compatibility with ellipsometric analysis. This is possible with decreasing optical thickness until ∼1/10 quarterwave is reached, which sets a limit for the usual optical film behavior.

Revisiting the preparation of titanium dioxide: aerosol-assisted production of photocatalyst with higher catalytic activity than P25

This research revisited the preparation of the pure titanium dioxide. Through the aerosol-assisted technology and our self-made setup, a kind of titanium dioxide with higher activity than commercial product P25 was successfully fabricated, while this aerosol-assisted process takes only about 10 s. By adjusting the operation temperature, the obtained titanium dioxide nanoparticles have different crystalline sizes and phase compositions, which are two major factors determining the catalytic activity of the materials. The results show that the optimum temperature was 600 °C, and the AST-600 particle prepared under this condition has the rate constant at 1.49 in the removal of methyl orange, which is 2.36 times that of Degussa P25. Although the AST-600 particle could only be activated by UV light similar to P25, the efficiency of AST-600/g-C3N4 is higher than that of P25/g-C3N4 under the visible condition. Meanwhile, the as-prepared titanium dioxide particles have been thoroughly characterized by TEM, SEM, XRD, PL, XPS, DRS, Raman and nitrogen adsorption in the study. Hence, we prepared a pure titanium dioxide with higher catalytic activity than P25, but the process is still very convenient, low cost and easy to scale up, holding great potential as an alternative to commercial product P25.

Structural, optical properties and photocatalytic activity of Fe3+ doped TiO2 thin films deposited by sol-gel spin coating

Nanocrystalline TiO2: Fe3+ films were deposited using a simple spin coating technique. The effect of Fe3+ on spectroscopic features and photocatalytic activity of films were studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), high-resolution transmission electron microscope (HR-TEM), Raman spectrometer, UV–Vis and fluorescence spectrophotometer. The XRD of all the TiO2: Fe3+ films exhibits a decrease in the crystallite size with an increase in Fe3+ concentration. The Fe3+ doped TiO2 nanocrystals exhibited a high specific surface area. The HR-TEM images of 1% and 7% Fe doped TiO2 thin films confirmed the average particle size is about 14 and 8 nm respectively. The Raman modes of vibrations present in the TiO2:Fe3+ films also confirms the formation of the anatase phase. The optical bandgap energy of titania decreases from 3.32 to 2.57 eV. The luminescent emission intensity of TiO2: Fe3+ films decreased compare to pure titania film. Moreover, the photocatalytic activity (PCA) of TiO2:x%Fe3+ (x = 0, 1, 3, 5, 7 and 10) catalysts were determined by the decomposition of methylene blue (MB) under irradiation of visible light. The observed results revealed that the optimized Fe3+ doped TiO2 film displayed high PCA. The enhancement of PCA of the films is due to the effect of Fe doping.

Firmness and bandgap engineered anatase TiO2 nanoparticles for enhanced visible light photocatalytic activity

Titanium dioxide is a standard semiconductor material plays a vital role in environmental and energy research. Anatase to rutile phase transformation in pure TiO2 nanoparticles usually occurs in the temperature range 600 °C–700 °C with it only absorbs UV light, owing to its large bandgap of 3.2 eV. Till date, researchers and industrialists have been trying to synthesize TiO2 nanoparticles with increased anatase phase stability with reducing the bandgap of pure anatase phase to the visible region, used dopant or H2O2 precursor modification, but the long time has taken photocatalytic activity under sunlight. Here, using a novel Photon Induce Method (PIM) has reported extending the anatase to a rutile transformation temperature, which in turn reflects on the stability of the material. PIM prepared oxygen-rich TiO2 nanoparticles exhibit enhanced temperature stable anatase phase, i.e. the sample remained as pure anatase phase even after calcinating at 1000 °C with a reduced bandgap of less than 2.91 eV, stretching towards the red region of the sunlight, whereas the standard Degussa P25-TiO2 and Others are reported to exist as 100% rutile at this temperature. By tuning the oxygen vacancy preparation conditions, we can reversibly improve oxygen-rich Titania via PIM. The absence of dopant or H2O2 of pure Titania anatase nanoparticles is high chemical reactivity has important implications for antibacterial, cancer cells kill, photocatalysis and solar energy conversion.

Removal of indigo dye by photocatalysis process using Taguchi experimental design

The major concern of the present research is degradation of hazardous and stable Indigo dye used in industrial denim dying process. For this purpose, a heterogeneous photocatalysis process was carried out to treat aqueous solution of Indigo dye using pure titanium dioxide (TiO2) in a batch reactor system under ultraviolet A (UVA) light for 210 min. In the study, individual and synergistic effects of factors such as TiO2 dosage, pH, and initial dye concentration were scrutinized. Moreover, Taguchi statistical method was performed to optimize influential parameters. The results obtained from the study that TiO2 concentration had the most effective factor on the Indigo dye degradation. The optimal conditions for dye removal were A (pH) at level 2 (4), B (initial dye concentration) at level 1 (10 mg/L) and C (TiO2 concentration) at level 4 (1.5 g/L). The results presented that the theoretically predicted value for degradation efficiency (100%) was confirmed by the experimental value (100%).

Transparent thin films of pure anatase Titania nanoparticles with low surface roughness prepared by electron beam deposition method

In this research, electron beam deposition method was used to synthesize Titanium dioxide (TiO2, Titania) thin films on quartz substrates at different oxygen partial pressures followed by thermal annealing. The samples were characterized by x-ray diffraction (XRD), UV-visible spectrophotometry, four-point probe and atomic force microscopy (AFM) techniques. A detailed study on the effects of deposition conditions on structural, optical, electrical and morphological properties of TiO2 films was systematically considered. The results reveal that all films possessed the anatase structure after heat treatment. The thermal annealing resulted in a gradual increase in crystallite size and optical transmittance while the corresponding refractive index decreased. The optical band gap, Eg, of TiO2 films increased from 3.76 eV to 3.83 eV. It is also found that electrical resistivity, ρ, decreased from 3.45 × 105 Ω cm to 1.25 × 104 Ω cm. Furthermore, the AFM micrographs revealed that the annealed film deposited at lower oxygen partial pressure produce a fine surface roughness suitable for many practical applications such as hydrophilic properties of thin films, for instance.

Preparation of coral-like Ag2MoO4–TiO2 heterostructure and its photocatalytic properties

In this work, TiO2 nanofibers were prepared by combining electrospinning with an impregnation calcination technique. Ag2MoO4 nanoparticles at various concentrations were successfully deposited onto the surface of the nanofibers by hydrothermal synthesis method. Photocatalytic activities of samples for methyl orange degradation were investigated. The results indicate that Ag2MoO4–TiO2 nanofibers could efficiently degrade methyl orange upon the irradiation with UV-light, showing a greater photocatalytic activity than the pure titanium dioxide.

A sintered graphene/titania material as a synthetic keratoprosthesis skirt for end-stage corneal disorders

An artificial cornea or keratoprosthesis requires high mechanical strength, good biocompatibility, and sufficient wear and corrosion resistance to withstand the hostile environment. We report a reduced graphene oxide-reinforced titania-based composite for this application. Graphene oxide nanoparticles (GO) and liquid crystalline graphene oxide (LCGO) were the graphene precursors and mixed with titanium dioxide (TiO2) powder. The composites reinforced with reduced GO or LCGO were produced through spark plasma sintering (SPS). The mechanical properties (Young’s modulus and hardness), wear behaviour and corrosion resistance were studied using nanoindentation, anoidic polarization, long-term corrosion assay in artificial tear fluid and tribology assay in corroboration with atomic force microscopy and scanning electron microscopy. Biocompatibility was assessed by human corneal stromal cell attachment, survival and proliferation, and DNA damages. Sintered composites were implanted into rabbit corneas to assess for in vivo stability and host tissue responses. We showed that reduced graphene/TiO2 hybrids were safe and biocompatible. In particular, the 1% reduced LCGO/TiO2 (1rLCGO/TiO2) composite was mechanically strong, chemically stable, and showed better wear and corrosion resistance than pure titania and other combinations of graphene-reinforced titania. Hence the 1rLCGO/ TiO2 bioceramics can be a potential skirt biomaterial for keratoprosthesis to treat end-stage corneal blindness. Statement of SignificanceThe osteo-odonto-keratoprosthesis (OOKP) is an artificial cornea procedure used to restore vision in end-stage corneal diseases, however it is contraindicated in young subjects, patients with advanced imflammatory diseases and posterior segment complications. Hence, there is a need of an improved keratoprosthesisskirt material with high mechanical and chemical stability, wear resistance and tissue integration ability. Our study characterized a reduced graphene oxide-reinforced titania-based biomaterial, which demonstrated strong mechanical strength, wear and corrosion resistance, and was safe and biocompatible to human corneal stromal cells. In vivo implantation to rabbit corneas did not cause any immune and inflammation outcomes. In conclusion, this invention is a potential keratoprosthesis skirt biomaterial to withstand the hostile environment in treating end-stage corneal blindness.

Water-Based Sol–Gel Synthesis of Ce-Doped TiO2 Nanoparticles

Pure titanium dioxide (TiO2) and Ce-doped TiO2 nanoparticles (NPs) were synthesized with the different dopant percentages of 2%, 4%, 6%, 8%, and 10% by using titanium tetrachloride (TiCl4) and cerium chloride (CeCl3) precursors, pure water as a solvent, and hydrochloric acid (HCl) as the hydrolysis reactor in the presence of ethylene glycol (C4H10O3) stabilizer through the sol–gel method. The morphological, structural, optical and electronic properties of the NPs were investigated via x-ray diffraction (XRD) analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). From the XRD analysis, it was found that the structure of the Ce-TiO2 NPs remained unchanged in the tetragonal state and anatase phase by increasing dopant, while the size of the nanocrystals (29 nm) in the pure state decreased down to 25 nm by increasing dopant up to 6%. The apparent pseudo-spherical shape and diameter of about 26 nm were obtained for the impure NPs through TEM. The UV-DRS analysis indicated the wide-band gap formation of the NPs through the water-based sol–gel method. As Ce increased, the band gap was enhanced from 5.02 eV for the pure TiO2 NPs up to 5.46 eV for the NPs of 10% dopant. The wide band gap created in these NPs allowed them to be used with an optimum absorption in the ultraviolet (UV) light applications. The results of FTIR analysis showed that the absorption peak of 508 cm−1 was related to the vibrational bond of Ti-O-Ce in the pure state, which changed towards the frequencies of 498 cm−1, 513 cm−1, 490 cm−1, 492 cm−1 and 469 cm−1 for the Ce dopant concentrations of 2%, 4%, 6%, 8%, and 10% entering into the TiO2 matrix, respectively. Finally, the results of the PL analysis revealed that the maximum energy-band interaction of TiO2 with Ce was created at 426 nm with a dopant of 6%.

Comparative study of photocatalytic deactivation of pure and black titania thin films

Thin film black titania (H-TiO2-x) was obtained in hydrogen plasma in an MPCVD system. The photocurrent and the methylene blue (MB) photodegradation rate of the black titania increased drastically compared to the pure anatase sample. A major difference between pristine and black titania films in photocatalytic deactivation by MB was found. Pristine TiO2 thin films were not deactivated after a series of MB degradation measurements followed by rinsing with DI-water, while the photocatalytic activity of H-TiO2-x dropped by 50%. It was shown that the deactivated sample can be regenerated with a process that consists of exposure of the deactivated sample to UV-VIS light in DI-water. It was found that due to the presence of hydroxyl groups on the surface, as well as an upward band bending on the surface of the black photocatalyst, the products of MB degradation during the photocatalytic reaction are being chemically bonded to the surface of H-TiO2-x, but not pristine TiO2. Based on the new results, a new description of thin film black titania is provided.