Presence Of Titania Research Articles

Photocatalytic Conversion of Lignin in the Presence of Titania and Iron Titanate Films

Photocatalytic Conversion of Lignin in the Presence of Titania and Iron Titanate Films

Superhydrophilic surface on Ti6Al4V with good HA-inducing ability prepared via an eco-friendly two-step method

Micro-nanomesh structures were successfully constructed on Ti6Al4V substrate by sandblasting and hydrothermal treatment. The resultant surface exhibited strong adhesion to water and simulated body fluid (SBF) with the contact angles (CA) of 0.7° and 0.6° respectively. This highly adhesive surface still retained its superhydrophilicity after exposing to air for more than 2 weeks. Furthermore, the obtained surface was proved to be capable of rapidly depositing hydroxyapatite (HA), on which a thick and homogeneous HA layer formed within 3 days of SBF soaking. The mechanism of rapid HA deposition in vitro was explicated from three aspects: the rough hierarchical structures, the durable superhydrophilicity and the presence of titania (TiO2) layer.

Carbon dioxide reduction under visible light: a comparison of cadmium sulfide and titania photocatalysts

Photocatalysts based on titania and solid solutions of cadmium and zinc sulfides with deposited metals (Pt, Ag) were compared in CO2 reduction under visible light. In the presence of titania- and cadmium sulfide-based photocatalysts, the dominant reduction products were CH4 and CO, respectively, due to different positions of the conduction band level for these semiconductors. The deposition of metals on the surface of both TiO2- and CdS-based samples increased the molar concentration of methane in the reaction products.

UV–Vis spectroscopy and desorption/ionization mass spectrometry as the tools for investigation of adsorbed dye photodegradation

The photodegradation of the cationic dyes methylene blue, acridine yellow and acridine orange adsorbed on TiO2, TiO2/SiO2, SiO2 and Ag/SiO2 mesoporous films has been studied by electronic spectroscopy and laser desorption/ionization mass-spectrometry methods. Qualitative difference of peak intensity distribution for cation M+ and its reduced forms [M + H]+· and [M + 2H]+ has been detected in the laser desorption/ionization mass spectra of the dye adsorbed on the three film types. The results point out the sensitivity of the laser desorption/ionization mass spectra parameters to specific features of the dye cation adsorption on films of different compositions and photocatalytic activity. Characteristic dependencies of mass spectra intensities upon the duration of UV irradiation have been obtained for dyes adsorbed on the catalytically active films. Some products of the dye photo-destruction have been identified, and it has been shown that photo-catalytic activity decreased in the order TiO2 > SiO2/TiO2 > SiO2. In the presence of titania, photobleaching of adsorbed dyes occurs faster in comparison with this process in the presence of SiO2 and leads to the full discoloration and degradation of adsorbed dye molecules. Efficient photodegradation of acridine dyes occurs through the following steps: 1-N-demethylation (deamination for AY); 2-photodimerization; 3-photodegradation. It is shown that both the rise of Ag nanoparticle concentration on the surface of mesoporous silica films and the enlargement of the nanoparticles’ size from 3 to 6–12 nm intensified methylene blue desorption/ionization. The efficiency of mesoporous nanosized TiO2, SiO2/TiO2, SiO2 and Ag/SiO2 films as substrates for laser desorption/ionization mass-spectrometry method has been demonstrated.

Photoelectrochemical Behavior of Silver Nanoparticles inside Mesoporous Titania: Plasmon-Induced Charge Separation Effect.

The self-assembly block copolymer method was used to synthesize mesoporous titania films and silver nanoparticles (NPs) were grown inside the films. Such silver NPs-titania films are known for their multicolor photochromic properties due to a photo-oxidation reaction of silver in the presence of titania under light excitation which is attributed to a plasmon induced charge separation. Here, the photoelectrochemical properties of these composite films have been investigated at different light wavelengths and chemical environment in order to characterize the light-induced redox reactivity modifications. Cyclic voltammetry study shows that the Ag+ electro-reduction peak potential varies depending on the light irradiation, which determines the state of the silver nanoparticles complexed or not by titania.

Synthesis and characterization of pure and titania doped hydroxyapatite

Abstract Hydroxyapatite (HAp) is highly biocompatible and osteoconductive bioceramic material which is found in bone and teeth. The mechanical property of synthetic HAp is very poor so it cannot be used as load bearing implants. One approach to improve its mechanical properties is use of dopant ions. The aim of this study is to synthesize titania doped HAp and to compare doped HAp structure with pure HAp. Here, pure and titania doped HAp was synthesized using wet chemical method and characterized by XRD, FTIR, SEM and EDAX. It was observed that, the lattice parameter, crystallinity of doped HAp was decreased than the pure HAp due to distortion in the structure. The presence of titania in the doped HAp was confirmed by EDAX analysis.

The effects of SiO2 and TiO2 on the two-phase burning behavior of aqueous HAN propellant

Silica and titania nanoparticles were included at mass loadings of 1% and 3% in aqueous HAN propellants to evaluate their effects on liquid- and gas-phase decomposition and combustion. Both the liquid-phase and overall burning rates of propellant formulations were indirectly measured in a constant-volume strand burner filled with Argon from pressures of 3–22 MPa using a novel, pressure-based method developed by the authors in recent work. This approach provides overall burn times for propellants such as aqueous HAN which continue to burn beyond the disappearance of the liquid, making it superior to methods based solely on visual observation which only monitor the liquid surface regression. The presence of silica nanoparticles increased the liquid-phase burning rate in the low- and medium-pressure regimes (<10 MPa) and increased the overall burning rate at all pressures evaluated. The maximum amount of burning rate enhancement was realized at the lowest evaluated pressure (3 MPa) which corresponded to 80% and 670% increases in the liquid-phase and overall burning rates, respectively, for a silica loading of 1%, and 160% and 830% increases in the liquid-phase and overall burning rates, respectively, for a silica loading of 3%. The presence of titania did not measurably affect the liquid-phase burning rate, but it did increase the overall burning rate in the low-pressure regime (<5.7 MPa). This low-pressure overall burning rate enhancement was not amplified by further titania loading from 1% to 3% and was maximized at the lowest evaluated pressure (3 MPa) which corresponded to a 500% increase in the overall burning rate. The observed enhancements of the propellant's liquid-phase and overall burning rates were attributed to the presence of catalytic processes which diminish at higher pressures. This work represents the first time nanoparticle additives have been utilized to tailor the combustion of liquid HAN-based monopropellants.

Enhancement of reaction-sintering of alumina-excess magnesium aluminate spinel in presence of titania

Alumina-excess magnesium aluminate spinel finds use in different high temperature applications including steel ladles. Alumina-excess spinel was prepared by solid oxide reaction using magnesia (MgO=10 wt%) and calcined alumina (Al2O3 = 90 wt%), in the sintering temperature range of 1500–1700 °C. The role of titania on the densification, spinelisation, evolution of microstructure and phase assemblage was investigated in this MgO-Al2O3 system. Titania addition increased the rate of densification 20x compared to undoped composition at 1500 °C under dynamic heating condition. However, under static firing, the beneficial effect of titania on densification could only be discerned at lower temperatures. The microstructure of titania doped sintered alumina-excess spinel compacts contain magnesium aluminium titanate phase in the grain boundary of corundum and spinel grains. The beneficial effect of titania on densification is attributed to magnesium aluminium titanate phase (MgxAl2(1-x)Ti(1+x)O5) development and also by incorporation of Ti4+ into the spinel structure.

Effect of a titania covering on CNTS as support for the Ru catalysed selective CO methanation

One of the major set-backs in the selective CO methanation process, as the final clean-up step in removing residual CO from reformate gas feed, is the reverse water gas shift (RWGS) reaction. This reaction is an undesired reaction because, it runs parallel with the selective CO methanation reaction. This increases the CO outlet concentration. The catalytic performance of ruthenium supported on carbon nanotubes (CNTs), nitrogen doped carbon nanotubes (NCNTs), titania coated carbon nanotubes (NCNT-TiO2 and CNTs-TiO2) and TiO2 anatase (TiO2-A) for selective CO methanation was investigated. The feed composition relevant to reformate gas was used but in the absence of steam. The experiments were conducted within a temperature range of 100 °C and 360 °C. It was observed that carbon dioxide methanation was suppressed until CO methanation attained a maximum conversion for all the catalysts studied. The Ru/NCNT showed higher activity than Ru/CNT at all temperatures examined due to the nitrogen incorporation in the carbon domains. Both Ru/CNT and Ru/NCNT however promoted the RWGS reaction at temperatures above 250 °C. The Ru/CNT-TiO2 catalyst recorded the highest activity for both the CO and selective CO methanation followed by Ru/TiO2-A. The presence of titania on the carbon nanotubes significantly retarded the RWGS reaction from about −120% CO conversion to about 80% CO conversion, while selectivity towards methane increased in all catalysts with increasing temperature.

One-Pot Synthesis of Mesoporous Ni-Ti-Al Ternary Oxides: Highly Active and Selective Catalysts for Steam Reforming of Ethanol.

One-pot synthesis of nanostructured ternary oxides of Ni, Al, and Ti was designed and performed via evaporation induced self-assembly (EISA). For the purpose of comparison, analogous oxides were also prepared by the impregnation method. The resulting materials were applied in two catalytic reactions: steam reforming of ethanol (SRE) for H2 production (subjected to prior activation with H2) and ethanol dehydration (ED; used without prior activation), to in situ analyze carbon accumulation by ethylene depletion when ethanol interacts with acidic sites present on the support. Modification of Ni-Al mixed oxides with titania was shown to have several benefits. CO2, NH3, and propylamine sorption data indicate a decrease in the strength of acidic and basic sites after addition of titania, which in turn slowed down the carbon accumulation during the ED reaction. These changes in interactions between ethanol and byproducts with the support led to different reaction pathways in SRE, indicating that the catalysts obtained by EISA with titania addition showed higher ethylene selectivity and CO2/CO ratios. The opposite was observed for the impregnated catalysts, which were less coke-stable during ED reactions and showed no ethylene selectivity in SRE. Carbon formed during ED reactions was shown to be thermodynamically less favorable and easier to decompose in the presence of titania. All catalysts studied displayed similar and high selectivities (∼80%) and yields (∼5.3 molH2/molethanol) toward H2, which place them among the most active and selective catalysts for SRE. These results indicate the importance of tailoring the support surface acidity to achieve high reforming performance and higher selectivity toward SRE, one of the key processes to produce cleaner and efficient fuels. For an efficient reforming process, the yield of byproducts is low but still they affect the catalyst stability in the long-run, thus this work may impact future studies toward development of near-zero coke catalysts.

Mechanical properties of sol–gel prepared nanocomposite coatings in the presence of titania and alumina-derived nanoparticles

ABSTRACTHybrid nanocomposite coatings were prepared by sol–gel method using silica, titania and alumina nanoparticles derived from their alkoxides precursors; in the presence of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA) on 1050 aluminium alloy substrate. The effect of type and ratio of nanoparticles on mechanical behaviour of the coatings were investigated by dynamic mechanical thermal analysis (DMA) and nanoindentation experiments. DMA results demonstrated that the values of the glass transition temperature (Tg) and the temperature at maximum tan (δ), (Tt) as well as the storage modulus of the hybrid samples depend mainly on the silane content and titania to alumina molar ratio of nanoparticles in the coating composition. In addition, nanoindentaion experiments were performed to study the mechanical properties such as hardness, elastic modulus and E/H ratio for the nanocomposite hybrid coatings. Nanoindentation results indicate that the homogenous reinforced structure was formed in the surface of nanocomposite coating with incorporation of titania and alumina-derived nanoparticles. The incorporation of TiO2 in comparison with AlOOH nanoparticles in the GPTMS-based coatings showed an improving effect on E/H ratio.

WO&lt;sub&gt;3&lt;/sub&gt;:TiO&lt;sub&gt;2&lt;/sub&gt; Particle Characterization Obtained by High Energy Milling for Application in Photocatalysis

Effective ways to treat textile industrial effluents have been studied in attempt to find alternatives to reduce the imminent risk of water resources contamination. The heterogeneous photocatalysis stands out in this scenario working in the organic waste mineralization, such as dyes. The objectives of this study were to investigate the obtaining of fine powders of the WO3:TiO2 (the investigated proportions in this work were 0: 100; 30:70; 50:50; 70:30; 100:0) using the high energy milling technique and to evaluate the photocatalytic efficiency of the Rhodamine B dye in this system. The oxides precursors were characterized by X-ray diffraction, BET and Helium pycnometry. After dry milling for 4 hours, the obtained powders were characterized by X-ray diffraction and tested to the photocatalysis in UV-C. The results indicate that the milling process has a direct influence on the photocatalytic properties of the investigated systems, and that the greater presence of titania in the mixture leads to a greater catalytic effect.

Electrochromic and photoelectrochromic properties of sol–gel derived tungsten trioxide/titania composite thin films

Tungsten trixoide/titania (WO3-titania) composite thin films with W/Ti molar ratios of 100/0, 98/2, 96/4, 94/6 92/8 and 90/10 were prepared on fluorine-doped tin oxide conducting glass, and their electrochromic (EC) and photoelectrochromic (PEC) performances were investigated in this study. The composite thin films were synthesized by sol–gel process using peroxotungstic acid and titanium (IV) n-butoxide as the precursors. The surface morphology and composition of the composite thin films were characterized using scanning electron microscope with energy dispersive spectrometer. Electrochemical experiments with in situ spectroscopic measurement were employed to study the EC properties of the composite thin films. It was found that the presence of titania in the WO3 matrix might slightly decreases its EC performance. PEC cells using the composite thin films as the working electrode and a sputtered semitransparent platinum thin film on ITO as the counter electrode were fabricated and their PEC performances were investigated. The device using composite thin film prepared from sol solution with a W/Ti molar ratio of 96/4 exhibited the best PEC performance.

Facile preparation of extremely photoactive boron-doped TiO 2 nanotubes arrays

Doping of TiO2 nanotube arrays with boron was realized via electrochemical treatment of as-anodized titania immersed in electrolyte containing boric acid. The photoactivity of doped and pure titania was examined by means of photoelectrochemical and photocatalytic response under UV–vis irradiation. The results showed that photocurrent density of B-TNTs is remarkably higher (7.5 times) than density of pure TiO2 nanotube arrays. Furthermore, the usage of doped samples as a catalytic material leads to a significant improvement in decomposition efficiency of methylene blue and in the efficient formation of hydroxyl radicals than is the case in the presence of titania.

HDS performance of NiMo catalysts supported on nanostructured materials containing titania

In the present work, NiMo catalysts supported on titania-containing materials of the SBA family (Ti-SBA-15 and Ti-SBA-16) and on titania nanotubes of different pore diameters were prepared with the aim of selecting the most promising catalysts for deep hydrodesulfurization (HDS) of gas oil. Supports and catalysts were characterized by nitrogen physisorption, XRD, temperature programmed reduction, ammonia TPD, UV–vis DRS and scanning electron microscopy (SEM-EDX). Sulfided catalysts were characterized by HRTEM and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). For comparison purposes, a conventional NiMo/γ-Al2O3 catalyst was used. In HDS of DBT, all catalysts supported on titania-containing nanostructured materials showed similar activity as the NiMo/γ-Al2O3 reference, but in HDS of 4,6-DMDBT their activities were about twice higher than that of NiMo/γ-Al2O3. Regarding selectivity, for DBT HDS, the presence of titania in the supports resulted in an increase in the proportion of CHB product, whereas for 4,6-DMDBT different behavior was observed. Thus, NiMo catalysts supported on Ti-SBA-15 and Ti-SBA-16 showed similar selectivity as the NiMo/γ-Al2O3. On the contrary, the catalysts supported on titania nanotubes allowed reaching high conversions of 4,6-DMDBT with a much lower proportion of hydrogenated products, which is an interesting result not observed by us previously.

The effect of anatase and rutile crystallites isolated from titania P25 photocatalyst on growth of selected mould fungi

Antifungal properties of anatase and rutile crystallites isolated from commercial titania P25 photocatalyst were investigated by mycelium growth in the dark and under indoor light. Investigated fungi, i.e., Pseudallescheria boydii, Scedosporium apiospermum, Pseudallescheria ellipsoidea, Scedosporium aurantiacum, Aspergillus versicolor, Aspergillus flavus, Stachybotrys chartarum, Penicillium chrysogenum, Aspergillus melleus, were isolated from air and from moisture condensed on walls. Anatase and rutile were isolated from homogenized P25 (homo-P25) by chemical dissolution, and then purified by washing and thermal treatment. For comparison, homo-P25 was also thermally treated at 200°C and 500°C. Titania samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and scanning transmission electron microscopy (STEM). It was found that properties of titania, i.e., band-gap energy, impurities adsorbed on the surface, nanoparticle aggregation, and kind of fungal structure, highly influenced resultant antifungal activities. It is proposed that some fungi could uptake necessary water and nutrient from titania surface. It was also found that even when differences in mycelium growth were not significant, the sporulation and mycotoxin generation were highly inhibited by light and presence of titania.

Influence of TiO2- and ZrO2-addition on the interaction of alumina castable with molten coal and gasifier slag

Gasification is a key process of chemical and energy industry. In order to improve the economic feasibility of gasifiers, new refractory lining materials with a long service life have to be developed, which can substitute the currently used high chromia bricks. TiO2 and ZrO2 were added to an Al2O3-refractory in order to improve its thermal shock and corrosion resistance against molten slags. Next to the investigation of material properties and structure, cup tests with holding time of 3 and 150h at 1450°C in different gasification-similar reducing atmospheres have been performed and the corrosion mechanism identified by analysing the slag–refractory interface in SEM. During sintering, the addition of 2.5wt.% TiO2 causes the formation of needle-shaped Na2Al2Ti6O16 crystals, which essentially influence the microstructure and provide excellent thermal shock resistance. In addition, in contact with coal slag, the presence of titania and zirconia promotes the formation of a protective MgAl2O4-layer, which stops slag infiltration and dissolution.

Photocatalytic ozonation of clopyralid, picloram and triclopyr. Kinetics, toxicity and influence of operational parameters

AbstractBACKGROUNDPhotolysis, photocatalysis, ozonation and photocatalytic ozonation in the presence of titania have been applied to the elimination of three pyridine carboxylic acids herbicides (clopyralid, picloram and triclopyr) in water.RESULTSPhotocatalytic ozonation led to the best results in terms of herbicide elimination rate and mineralization. The herbicides were relatively recalcitrant to direct ozonation (rate constants: 20 M−1 min−1 for clopyralid and triclopyr, and 105 M−1 min−1 in the case of picloram). Herbicides degradation proceeds by hydroxyl radicals attack (rate constants: 0.73, 3.80 and 1.73 × 109 M−1 s−1 for clopyralid, picloram and triclopyr, respectively). Monitoring of chloride and nitrates suggests dechlorination as the primary stage in the process. Further ring opening led to the accumulation of nitrates and the appearance of some low weight carboxylic acids. Toxicity decreased at the end of the process.CONCLUSIONTested herbicides slowly react with ozone. Photocatalytic ozonation shows different degrees of synergism, leading to 80% mineralization in less than 1 h. Small amounts of TiO2 (i.e. 0.005 g L−1) maintains the efficiency of the photocatalytic ozonation. Quantitative free chloride and nitrates rapidly appear in the O3/UVA/TiO2 system. First intermediates in the photocatalytic ozonation of clopyralid show higher toxicity than the parent compound. © 2014 Society of Chemical Industry

Sintering and mechanical properties of the alumina–tricalcium phosphate–titania composites

The objective of this study was to determine the effect of the content of titania and the sintering process on the transformation phase, the densification, the rupture strength and the microstructures of the alumina–10wt.% tricalcium phosphate composites. After the sintering process, the samples were examined by using 31P and 27Al magic angle scanning nuclear magnetic resonance, X-ray powder diffraction and scanning electron microscopy analysis. The Brazilian test was used to measure the rupture strength of the samples. The present results provide new information about solid-state reactivity in the ternary system α-alumina-β-tricalcium phosphate–anatase–titania. The differential thermal analysis of the α-alumina-β-tricalcium phosphate–titania composites shows two endothermic peaks, at 1360°C and at 1405°C, which are caused by the reactions between titania/alumina and titania/tricalcium phosphate, respectively. Thus, the presence of titania in the alumina–10wt.% tricalcium phosphate leads to the formation of β-Al2TiO5 at 1360°C. At 1600°C, the alumina–10wt.% tricalcium phosphate–5wt.% titania composites displayed the highest rupture strength (74MPa), compared to the alumina–10wt.% tricalcium phosphate composites (13.5MPa). Accordingly, the increase of the rupture strength is due to the formation of the new β-Al2TiO5 phase.

Preparation and characterization of electrochromic tungsten oxide–titania composite thin films with different tungsten/titanium ratios

Tungsten oxide–titania composite thin films with different W/Ti atomic ratios were prepared and characterized in this study. Surface morphology, composition and structure of the composite thin films were investigated by scanning electron microscope with an energy dispersive spectrometer, X-ray diffraction and atomic force microscope analyses. Electrochromic properties including transmittance modulation ability, coloration efficiency and coloring/bleaching response time of these thin films were examined using cyclic voltammetry and double-potential-step experiment with in-situ ultraviolet–visible spectroscopy measurement. The presence of titania in the composite thin film could inhibit the crystal growth of tungsten oxide, which enhances the transmittance modulation ability and coloration efficiency but prolongs the coloring/bleaching response time of the composite thin film. The tungsten oxide–titania composite thin film (WTi-30) with a W/Ti atomic ratio of 78/22 exhibited better transmittance modulation ability (57.5%) and coloration efficiency (49.2cm2/C) than a pristine tungsten trioxide thin film (53.6%, 36.2cm2/C).