Ti Atomic Ratio Research Articles

Self-Assembly of Large Scale CdS/TiO<sub>2</sub> Film Photocatalyst

CdS/TiO2 composite films with different Cd:Ti atomic ratio were prepared by a new straightforward particulate layer-by-layer method. Titanium dihydroxide and thiourea were used as precursors. Raman and X-ray photoelectron spectroscopy analysis for the composite films revealed that the TiO2 formed from titanium precursor retarded the crystal growth of CdS. Luminescence and UV–vis absorption spectra investigation showed that emission and absorption band of CdS/TiO2 blue shifted as crystal size of CdS decreased. Furthermore, hydrogen formation curves revealed that hydroxyl of CdS/TiO2 films plays an important role in water splitting reaction under both UV and visible light irradiations.

FTIR studies on photocatalytic activity of Ti(IV)-doped calcium hydroxyapatite particles

The photocatalytic activity of Ti(IV)-doped calcium hydroxyapatite (TiHap) particles with atomic ratio of Ti/(Ti+Ca) [XTi] from 0 to 0.20 prepared by a coprecipitation method, called as original particles, were examined by in situ Fourier-Transform IR (FTIR) measurement. The heat treated TiHap particles were also used after treated original particles at 650°C for 1h, called as heat treated particles. All the original particles were made up by rod-like particles with irregular size, while the heat treated particles were rounded by sintering and their sizes were enlarged in each XTi system. The TiHap particles were cation deficient particles with (Ca+Ti)/P atomic ratio ranging between 1.54 and 1.64. The XTi values of TiHap particles assayed showed approximately the dosage of Ti(IV) ions in each system. All the TiHap particles employed exhibited UV absorption below ca. 370nm, though the UV absorption characteristics did not vary by the heat treatment. However, the pure calcium hydroxyapatite with XTi=0 had no UV absorption. The IR spectra of the particles with XTi≥0.05 exhibited a new large peak at 3428cm−1 close to the peak at 3570cm−1 of OH− ions together with the bands at 3654–3682 or 3673 (surface POH groups) and 3737cm−1 (surface TiOH groups). The deuteration method revealed that the new band at 3428cm−1 could be assigned to the dislocated OH− ions by substituting Ti(IV) ions. The expansion of crystal structure along with c direction by the heat treatment was identified by the unit-cell dimension obtained from the XRD patterns. It was concluded therefore that the produced dislocated OH− ions by the heat treatment induce the photocatalytic activity of TiHap particles. The strong photocatalytic activity of TiHap particles was attributed to the dislocated OH− ions because they can produce OH radicals in the particles without water molecules by UV irradiation. Furthermore, FTIR and XRD measurements elucidated that the optimum temperature for inducing photocatalytic activity of TiHap is ca. 600°C.

Photocatalytic Activity of Ag<sup>+</sup>-Doped TiO<sub>2</sub> Thin Films Prepared by Sol-Gel Method

TiO2and Ag+-doped TiO2thin films were successfully obtained on microscope glass slides by means of sol-gel method. Then the photocatalytic activity of the TiO2and Ag+-doped TiO2thin films was evaluated by the degradation of rhodamine B dye solution. The effects of both annealing temperatures and Ag+contents on the photocatalytic activity of TiO2thin films were examined. The results indicated that the TiO2thin films with an atomic ratio of Ti:Ag=10:1 annealed at 300°C had a higher photocatalytic activity.

Mechanical properties of multilayer TiAlN/CrN coatings deposited by cathodic arc evaporation

The results of the investigations of multilayer TiAlN/CrN coatings deposited using cathodic arc evaporation applying TiAl (50∶50 at-%) and elemental Cr cathodes are presented. The bilayer TiAlN+CrN thickness was ∼250 nm with the thickness ratio of TiAlN/CrN layers of approximately 1∶1. The atomic ratio of Ti/(Al+Ti) in the coating was 0·60. As the reference, the monolayer TiAlN and multilayer TiAlN/TiN coatings were selected. All the coatings were deposited on CrN sublayer to reduce their stress and improve their adhesion. The investigated coatings show good adhesion in the range 80–90 N. The TiAlN/CrN coating shows a lower friction coefficient and a significantly lower wear rate than those of reference coatings (more than 10 times).

Effect of deposition time on morphology, corrosion resistance and mechanical properties of Ti-containing conversion coatings on zinc

Ti-containing conversion coatings were obtained on zinc electroplated steel. The influence of deposition time on the coatings morphology, chemical composition, corrosion resistance and mechanical properties were studied. Their chemical composition strongly depends on deposition time. As the time increases from 5 s to 300 s, the Ti content decreases and the Si content increases. For the deposition time of 5 s the Si:Ti atomic ratio in the conversion coating is 0.32 and after 300 s it increases to 9.1, which is accompanied by reduction in corrosion resistance. As deposition time increases, the microhardness of the coatings and their wear resistance deteriorate. Corrosion test results show that the coatings can be applied to protect zinc against corrosion.

Photocatalytic Activities of Ce<sup>3+</sup>-Doped TiO<sub>2</sub> Thin Films Prepared by Sol-Gel Method

A series of TiO2 thin films with and without Ce3+ doping were successfully obtained on microscope glass slides by sol-gel method. The photocatalytic activities of the pure TiO2 and Ce3+-doped TiO2 thin films were evaluated by the degradation of rhodamine B solution. The effects of both Ce3+ contents and annealing temperatures on the photocatalytic activities of the samples were examined. The results indicated that the TiO2 thin film with an atomic ratio of Ti:Ce=5:1 annealed at 300°C had a higher photocatalytic activity among the samples.

Photocatalytic Activities of Fe<sup>3+</sup>-Doped TiO<sub>2</sub> Thin Films Prepared by Sol-Gel Method

TiO2 and different contents Fe3+-doped TiO2 thin films were successfully obtained on microscope glass slides by Sol-Gel method. Then the photocatalytic activities of the samples were evaluated by the degradation of Rhodamine B dye solution. The effects of both annealing temperatures and Fe3+ contents on the photocatalytic activities of TiO2 thin films were examined. The results indicated that the sample with an atomic ratio of Ti:Fe=7:3 annealed at 500°C had a higher photocatalytic activity.

Reactive DC magnetron sputter deposited Ti–Cu–N nano-composite thin films at nitrogen ambient

Ti–Cu–N thin films have been grown on Si(111), KBr (potassium bromide), quartz and glass slide substrates using a TiCu (13:87 at. %) single multi-component target by reactive DC magnetron sputtering at nitrogen ambient. This study provides insight into the importance of nitrogen pressure on the characteristic of Ti–Cu–N thin films. Crystalline phases of these films are identified by X-ray diffraction (XRD) technique. The titanium atoms were inserted into the Cu 3N unit cell. The results from XRD show that the observed phases are nano-crystallite cubic anti-Rhenium oxide (anti-ReO 3) structure of Ti doped Cu 3N (Ti:Cu 3N) and nano-crystallite face centre cubic (fcc) structure of Cu. Formation of copper vacancies in Cu 3N cell substituted by titanium atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion and optical energy gap widening. Surface morphology of the films studied by scanning electron microscope (SEM) indicates agglomeration of grains. Ti:Cu atomic ratio of Ti–Cu–N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of the original TiCu single multi-component target and nearly independent of nitrogen pressure. Optical study is performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance using a reverse engineering method. Absorption coefficient indicates that the nitrided films are direct semiconductor. The films electrically show quasi-metallic behavior. The effect of sputtering pressure on deposition rate is investigated. Compared with the Ti free Cu 3N film, the Ti:Cu 3N films possesses fine thermal stability in vacuum.

Synthesis of Titanium Disilicide by the “Chemical Oven” Self-Propagating Combustion Method

TiSi2 (Titanium disilicide) has attracted great research interest due to its large silicon content, remarkably low electrical resistivity (about13–16μΩcm), good photocatalytic property, high temperature stability, and good corrosion resistance. It is an excellent electronic material and potential photocatalyst and high temperature structure material. In this work, TiSi2 was prepared by using the “chemical oven” enhanced self-propagating combustion method from the elemental powder compact. The mixture of Si and Ti (atomic ratio 3:5) were ignited as chemical oven. The composition of product was detected by XRD. Result shows the product is a single phase titanium disilicide with trace impurities. The maximum combustion temperature of Ti+2Si compact was up to 1472°C, which exceeds the lowest eutectic point (1330°C) of the Ti-Si binary mixture. Thus it can be predicted the formation of TiSi2 is primarily dominated by the solid-liquid mechanism, which includes dissolving solid reactants and precipitating silicide product. It could also be convinced by SEM photos of the combustion product and reacting zone of the compact.

C, S & N-Doped TiO<sub>2</sub> Photocatalyst Prepared by the Reverse-Microemulsion Method

After TiO2/SPAN (Sulfonated Polyaniline) complex prepared by the reverse-microemulsion method was calcinated, C, S & N-doped TiO2 was successfully synthesized with C/S/N/Ti atomic ratio of 12.5/12.2/1.3/100 and formaldehyde-degradation ratio of 58.5%. Its excited wavelength was red-shifted to 433.5 nm and its band gap was degraded to 2.87 eV. XPS analysis proved that C, S & N was doped into TiO2 lattice to form TiC, Ti(CO)n, Ti(CO3)2, Ti(SO3)2, TiS2, TiN and Ti(NO2)n.

Fabrication of High‐Purity Ti3SiC2Powders by an In Situ Reaction of Polycarbosilane and Metal Titanium

High‐purity titanium silicon carbide powders were fabricated by anin situreaction of polycarbosilane and metal titanium. The effects of the starting reagents and the pyrolysis temperature on the fabrication of high‐purity Ti3SiC2were studied. The results showed that high‐purity Ti3SiC2could be obtained when the atomic ratio of Ti:Si was 3:1.5 and the effect of the temperature of pyrolysis on the purity of the powders was insignificant. The atomic ratio of Ti:Si was calculated on the basis of the empirical formula of SiC2.5H7.

Synthesis, characterization, and activities of visible light-driven Bi 2O 3–TiO 2 composite photocatalysts

A series of Bi 2O 3–TiO 2 composite photocatalysts were prepared with a facile nonaqueous sol–gel method through varying the Bi–Ti atomic ratio and calcination temperature. The catalyst structures had been extensively characterized by using X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–vis DRS). The characterization results revealed that all of the Bi 2O 3–TiO 2 composites exhibited smaller crystallite size, higher thermal stability and stronger absorbance in visible light range than pure TiO 2. The photocatalytic activities of as-prepared catalysts were evaluated by the degradation of methyl orange (MO). The results showed that the Bi–Ti atomic ratio of 0.0175 was an optimum in the photocatalytic activities under visible light irradiation and the calcination temperature affected both the physicochemical properties and photocatalytic activities of the catalysts. XPS and XRD were further used to characterize the stability of the photocatalyst, which maintained a high activity without obvious deactivation after five recycles of the degradation.

Effect of Titanium Addition on Composite L1<sub>2</sub> Precipitates in Aluminum-Zirconium Alloy

The particle morphology and composition of nanometer-scale Al3(Zr1-xTix) precipitates formed after aging at 450 °C for 1 h in Al-0.3mol%Zr-0.5mol%Ti alloy were investigated using high resolution electron microscopy (HREM) and three dimensional atom probe tomography (3D-APT). The alloy exhibits an inhomogeneous distribution of solute atoms after casting. After aging, Al3(Zr1-xTix) precipitates with a metastable L12 structure formed within solute-enriched dendrites. The Al3(Zr1-xTix) precipitate particles were spherical with diameters between 3 and 5 nm. The Al3(Zr1-xTix) precipitates were found to be coherent with matrix using HREM. Interfacial segregation of Ti at the matrix/precipitates was also observed in the composite Al3(Zr1-xTix) precipitates. The Zr:Ti atomic ratio in the Al3(Zr1-xTix) precipitates measured by 3D-APT was approximately 7 (x=0.125).

Preparation of highly visible-light active N-doped TiO2 photocatalyst

A series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol–water reaction system. The effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO2. It was found that the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N : Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti 3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (O u � ) and hydroxyl radicals (OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO2.

Photocatalytic performances of mesoporous TiO2 films doped with gold clusters

We report on the single-pot fabrication of ordered mesoporous crystallized titania films doped with gold. Au is incorporated in TiO2 films by adding to the coating solution precursors such as AuCl3 or monodisperse Au113+ nanoclusters, and Au nanoparticles are formed by calcination. A systematic study is performed to correlate structure, Au doping and photocatalytic activity of such films. Two-dimensional small angle X-ray scattering (2D-SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM) and porosimetry–ellipsometry show that the films retain their mesoporous order even for doping levels as high as 1% Au : Ti atomic ratio. Wide angle X-ray scattering (WAXS), and cyclovoltammetry (CV) show that Au113+ nanoclusters promote the formation of the TiO2 (B) phase in competition with the anatase phase. AuCl3 stabilizes instead only the anatase phase. The highest photocatalytic activity is exhibited by films where Au113+ is employed as a precursor, which we attribute to the combination of the mixed anatase/TiO2 (B) phase, of Au nanoparticle doping and of a well-ordered mesoporous TiO2 matrix.

Water-based sol–gel nanocrystalline barium titanate: controlling the crystal structure and phase transformation by Ba:Ti atomic ratio

Highly stable, water-based barium titanate (BaTiO3) sols were developed by a low cost and straightforward sol–gel process. Nanocrystalline barium titanate thin films and powders with various Ba:Ti atomic ratios were produced from the aqueous sols. The prepared sols had a narrow particle size distribution in the range 21–23 nm and they were stable over 5 months. X-ray diffraction pattern revealed that powders contained mixture of hexagonal- or perovskite-BaTiO3 as well as a trace of Ba2Ti13O22 and Ba4Ti2O27 phases, depending on annealing temperature and Ba:Ti atomic ratio. Highly pure barium titanate with cubic perovskite structure achieved with Ba:Ti = 50:50 atomic ratio at the high temperature of 800 °C, whereas pure barium titanate with hexagonal structure obtained for the same atomic ratio at the low temperature of 500 °C. Transmission electron microscope revealed that the crystallite size of both hexagonal- and perovskite-BaTiO3 phases reduced with increasing the Ba:Ti atomic ratio, being in the range 2–3 nm. Scanning electron microscope analysis revealed that the average grain size of barium titanate thin films decreased with an increase in the Ba:Ti atomic ratio, being in the range 28–35 nm. Moreover, based on atomic force microscope images, BaTiO3 thin films had a columnar-like morphology with high roughness. One of the highest specific surface area reported in the literature was obtained for annealed powders at 550 °C in the range 257–353 m2g−1.

Phase determination of filtered vacuum arc deposited TiO 2 thin films by optical modeling

Thin films of TiO 2 were produced using filtered vacuum arc deposition. Arc currents were 275, 300, 325 A, and the oxygen pressure during deposition was 0.93 Pa. The substrates were glass microscope slides, at temperatures of 25 °C (RT), 200 °C, and 400 °C. Film thickness was in the range 100 to 250 nm, depending on the deposition conditions. Film structure and chemical composition were determined using XRD and XPS analyses, respectively. As-deposited films were amorphous, except to two samples that were found to be crystalline (deposited with 300 A, 325 A at 400 °C), and the crystalline phase was close to that of anatase. All of the films were partially crystallized by annealing in air at 450 °C for 1 h. The O:Ti atomic concentration ratio was in the range 1.6:1–2:1, independent of deposition conditions. The optical parameters, refractive index and the extinction coefficient of the films were determined using variable angle spectroscopic ellipsometry. In addition, the optical transmission of the films were determined in the UV–VIS and IR regions. The average optical transmission in the VIS spectrum was 70–85%, affected by the interference in the film with 90% maxima and 60% minima. The refractive index at λ = 550 nm was in the range 2.4 to 2.7, depending on the deposition conditions and annealing. Using the semi-empirical model of Wemple and DiDomenico for the dielectric function below the interband absorption edge of ionic and covalent solids, the dispersion energy parameters of TiO 2 ( E o, E d) were calculated. The underlying structural order of the amorphous films was inferred by comparing the dispersion energy parameters of the amorphous films with those of crystalline TiO 2. As expected, the refractive index of the amorphous films depended on the underlying phase of the film. The optical analyses indicated that the underlying phase of the amorphous films deposited on RT substrates was close to anatase, whereas the underlying phase of the amorphous films deposited on 400 °C substrates and annealed at 450 °C for 1 h consisted of both anatase and rutile. Thus, although the XRD analyses could not indicate the underlying phase of the amorphous films, it could be determined by the optical analyses.

One step room temperature photodeposition of Cu/TiO 2 composite films and its conversion to CuO/TiO 2

Cu/TiO 2 composite films were prepared at low temperature on glass substrates by a photodeposition method. Films were deposited by irradiating the substrate while in contact with an aqueous TiO 2 suspension containing copper(II) nitrate and ethanol. Cu/TiO 2 composite films of 500 nm in thickness were deposited at room temperature after a short irradiation time (15 min) with a 125 W mercury vapour lamp. According to scanning electron microscopy observations, the obtained films were homogeneous and porous. Energy dispersive X-ray spectroscopy analysis revealed a 3:1 Cu:Ti atomic ratio. Grazing angle X-ray diffraction analysis showed that the films contained Cu and TiO 2 as major components and Cu 2O as a minor component. Heat treatment at 400 °C in air for a period of 3 h transformed the initial material into a CuO/TiO 2 composite, improved the adhesion to the substrate and favoured a more regular distribution of copper oxide according to backscattering micrographs.

Formation of Photocatalytic Novel Oxide Crystallites with Al:Ti = 1: 1 in Al<SUB>2</SUB>O<SUB>3</SUB>-TiO<SUB>2</SUB> Gels by Mechanochemical Treatment

Al2O3-TiO2 bulk gels prepared from aluminum tri-sec-butoxide and titanium tetra-n-butoxide were mechanochemically treated using a planetary, high-energy ball mill. The initial state of the gels was amorphous and a novel crystalline material with a composition of approximately the same atomic ratio of Ti and Al was formed in the gel matrix at around room temperature during the milling. The size of the crystallites was several tens nanometers and their structure probably has a polytypic character with a high density of stacking disorder. The specimen containing the new crystallites showed a high photocatalytic property. Mechanochemical treatment of the sol-gel-derived multicomponent gels is a promising way to prepare novel composite materials that are not obtained by conventional heat treatments of the gels.

One-pot fabrication and magnetic studies of Mn-dopedTiO2 nanocrystals with an encapsulating carbon layer

Mn-doped TiO2 nanocrystals encapsulated in a carbon layer(Ti1−xMnxO2@C) were synthesized by the one-pot RAPET (reaction under autogenic pressure at elevatedtemperature) technique. Manganese was doped into the body-centered tetragonalTiO2 anatase phase to give a Mn:Ti atomic ratio of 1%, 5% and 10%. The surface modification by carbonwas achieved in order to make the cubic/tetragonal nanocrystals non-toxic and biocompatible.Electron paramagnetic resonance (EPR) studies revealed a broad resonance (centered atg = 1.9977 due to the interacting spins in the oxide matrix) with increased dopantconcentration and the resonance due to carbon. Manganese is mainly present as+II or+III oxidation states. The magnetic behavior was found to be very dependent on the manganeseconcentration with a ferromagnetic behavior of the 1% doped sample due to the couplingbetween carriers and manganese spins. A predominant paramagnetic behavior was observedfor the higher Mn-doped samples. This study opens up a new dimension for the carbonencapsulation of room-temperature ferromagnetic diluted magnetic semiconductor (DMS)nanomaterials.