Search results for "Titani"
showing 10 items of 931 documents
Thermodynamics of titanium and vanadium reduction in non-aqueous environment calculated at various levels of theory.
2012
Reduction of titanium and vanadium compounds is a process accompanying the activation of coordinative olefin polymerization catalysts. Four density functional theory (DFT) functionals, coupled cluster with single, double, and perturbative triple excitations method CCSD(T) as well as complete active-space second-order perturbation theory method CASPT2 with a complete active-space self-consistent field CASSCF reference wave function were applied to investigate the thermodynamics of titanium and vanadium reduction. The performance of these theoretical methods was assessed and compared with experimental values. The calculations indicate that vanadium(IV) chloride is more easily reduced by trime…
Ti(iv)-amino triphenolate complexes as effective catalysts for sulfoxidation
2010
C 3 -symmetric Ti (IV) amino triphenolate complexes efficiently catalyze, without previous activation and in excellent yields, the oxidation of sulfides at room temperature, using both CHP and the more environment friendly aqueous hydrogen peroxide as terminal oxidants, with catalyst loadings down to 0.01%. The Ti(IV) catalysts and the intermediate Ti(IV)-peroxo complexes have been characterized in solution by 1H NMR and ESI-MS techniques and via density functional studies.
Superficial defects induced by argon and oxygen bombardments on (110) TiO2 surfaces
1998
Abstract Compositional and chemical changes of titanium dioxide monocrystalline surfaces induced by bombardment with 4 keV argon and oxygen ions have been studied by AES, XPS and AFM. Argon ion bombardment induced strong changes in the composition and chemical state of the surface: loss of oxygen due to preferential sputtering occurred, and, related to this, Ti4+ species were reduced to Ti3+ and Ti2+. During oxygen bombardment, competition between preferential sputtering of oxygen ions of the oxide surface and oxygen implantation was observed. This phenomenon was found to be strongly dependent upon the incidence angle of the oxygen ions. Moreover, an oxygen bombardment with normal incidence…
Development of Eco-Friendly and Self-Cleaning Lime-Pozzolan Plasters for Bio-Construction and Cultural Heritage
2020
Summarization: Nowadays, the design and use of multi-functional mortars has increased significantly, with interesting applications in the green building and cultural heritage conservation sectors. A key point for a correct adoption of these innovative materials is their behavior along time and their resistance to the weathering. The objective of this project was to define the performance and durability of innovative mortars, in order to use them correctly and to avoid irreparable damage over time. For the development of this project, lime–metakaolin and hydraulic lime–metakaolin based mortars (hereinafter called A, B), as well as A and B with the addition of nano-TiO2 and perlite (hereinaft…
In vitro assessment of a novel additive manufactured titanium implant abutment
2021
Background Dental implant temporization remains a clinical challenge. A novel abutment simplifying the procedure was developed, but conventional fabrication was costly and unpredictable. A workflow was developed to fabricate the novel abutment using additive manufacturing. This in vitro investigation assessed the additive manufactured (AM) novel abutments to conventionally manufactured (CM) abutments. Material and methods The AM abutments were fabricated in dental-grade titanium (Ti-6Al-4V) using Selective Laser Melting and were post-processed. The CM abutments were milled and subsequently laser welded manually. Pin strength of the abutments was assessed using a universal loading machine. T…
Iron deposition on TiO2(110): effect of the surface stoichiometry and roughness
1999
Abstract Characterizations of ultra-thin iron films deposited on TiO 2 (110) surfaces with different stoichiometries, roughnesses and crystallinities have been carried out by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). For a high initial roughness of the substrate, a 2D growth mode is observed up to three monolayers. But, if the initial roughness is low, clusters grow on the TiO 2 surface. Whatever the initial surface stoichiometry, electronic exchanges occur between titanium and iron leading to a reduction of titanium and an oxidation of iron. This interaction between iron and titanium dioxide surface takes place only at the interface between the metal and…
Fabrication of layered nanostructures by successive electron beam induced deposition with two precursors: protective capping of metallic iron structu…
2011
We report on the stepwise generation of layered nanostructures via electron beam induced deposition (EBID) using organometallic precursor molecules in ultra-high vacuum (UHV). In a first step a metallic iron line structure was produced using iron pentacarbonyl; in a second step this nanostructure was then locally capped with a 2-3 nm thin titanium oxide-containing film fabricated from titanium tetraisopropoxide. The chemical composition of the deposited layers was analyzed by spatially resolved Auger electron spectroscopy. With spatially resolved x-ray absorption spectroscopy at the Fe L₃ edge, it was demonstrated that the thin capping layer prevents the iron structure from oxidation upon e…
Multi-doped Brookite-Prevalent TiO2 Photocatalyst with Enhanced Activity in the Visible Light
2018
© 2018 Springer Science+Business Media, LLC, part of Springer Nature Abstract: Enabling solar and/or visible light-driven photocatalysis is a crucial step to access innovative applications in environmental science and sustainable energy. Titanium dioxide is the most used photocatalyst because of its low cost and toxicity, however it is also limitedly active under visible light irradiation due to its wide band gap. Among its polymorphs, brookite holds promising optoelectronic properties for visible light photocatalysis, which have to the best of our knowledge been limitedly exploited. Here, a C,S,N-doped brookite-based TiO2has been prepared via a rapid one-pot sol–gel synthesis. Besides subs…
Electron Transfer from Organic Aminophenyl Acid Sensitizers to Titanium Dioxide Nanoparticle Films
2009
Electron transfer from three conjugated amino-phenyl acid dyes to titanium and aluminum oxide nanocrystalline films was studied by using transient absorption spectroscopy with sub 20 fs time-resolution over the visible spectral region. All the dyes attached to TiO2 showed long-lived ground state bleach signals indicative of formation of new species. Global analysis of the transient kinetics of the dyes on TiO2 revealed stimulated emission decays of about 40 fs and less than 300 fs assigned to electron injection. The same dyes on Al2O3 substrates displayed long stimulated emission decays (ns) suggesting that electron transfer is blocked in this high band gap semiconductor. For two of the dye…
Photocatalytic oxidation mechanism of benzonitrile in aqueous suspensions of titanium dioxide
2007
Abstract The photocatalytic oxidation of benzonitrile was carried out in aqueous suspensions (pH 11) of commercial polycrystalline TiO 2 (Merck and Degussa P25) irradiated by ultraviolet light. The rate of decomposition was dependent on the concentration of benzonitrile and followed a pseudo-first order kinetics. The complete mineralization of a 0.70 mM benzonitrile solution was achieved in ca. 8 h by using TiO 2 Degussa P25, whereas the substrate was only partially mineralized even after 14 h of irradiation in the presence of TiO 2 Merck. The final oxidation products were carbonate and nitrate. The appearance and the evolution of organic and inorganic intermediate species were also investi…