Search results for "element"
showing 10 items of 13601 documents
Stabilizing nanostructured lithium insertion materials via organic hybridization: A step forward towards high-power batteries
2014
Abstract Herein, we present the electrochemical characterization of carbon-coated TiO 2 nanorods, obtained by carbonizing RAFT (reversible addition fragmentation chain transfer) polymerization derived block copolymers anchored on anatase TiO 2 nanorods. These carbon-coated TiO 2 nanorods show an improved electrochemical performance in terms of first cycle reversibility, specific capacity, cycling stability, and high rate capability. More importantly, however, the structural disordering observed in the uncoated TiO 2 nanorods by means of galvanostatic and potentiodynamic cycling as well as ex situ XRD analysis, does not occur for the carbon-coated material. Preventing this structural disorde…
TiO2 anatase films obtained by direct liquid injection atomic layer deposition at low temperature
2014
International audience; TiO2 thin films were grown by direct liquid injection atomic layer deposition (DLI-ALD) with infrared rapid thermal heating using titanium tetraisopropoxide and water as precursors. This titanium tetraisopropoxide/water process exhibited a growth rate of 0.018 nm/cycle in a self-limited ALD growth mode at 280 degrees C. Scanning electron microscopy and atomic force microscopy analyses have shown a smooth surface with a low roughness. XPS results demonstrated that the films were pure and close to the TiO2 stoichiometric composition in depth. Raman spectroscopy revealed that the films were crystallized to the anatase structure in the as-deposited state at low temperatu…
Study of the structural changes induced by air oxidation in Ti–Si–N hard coatings.
2008
International audience; 3-μm thick Ti–Si–N coatings were deposited on polished X38CrMoV5 substrates by sputtering a composite Ti–Si target in Ar–N2 reactive mixture. Oxidation tests were performed in air at 700 °C during 2 h. Whatever the silicon content in the range 0–4 at.%, no silicon containing compound was detected by XRD before air oxidation and only the TiN phase was evidenced. The mean grain size estimated from the full width at half maximum of the TiN (111) diffraction peak was close to 10 nm. As commonly reported for Ti–Si–N films, the hardness showed a maximum at 51 GPa versus the Si content. After oxidation of the TiN film, XRD and micro-Raman analyses revealed the occurrence of…
Preparation and photoactivity of samarium loaded anatase, brookite and rutile catalysts
2011
Abstract Pure and samarium loaded anatase, brookite and rutile nanopowders were synthesized by thermohydrolysis of TiCl 4 . The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination, UV–vis diffuse reflectance spectroscopy (DRS), atomic force microscopy (AFM), contact angle (CA) measurements and photoluminescence (PL) spectroscopy. The photocatalytic activity of pure and Sm-loaded TiO 2 polymorphs was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid-solid system. Loading with Sm resulted in an improvement of the photoreactivity of the three TiO 2 polymorphs. The benefi…
Structural Studies of Titanium Oxide Multilayers
2005
Multilayers of titanium oxide on conductive glasses (silica, covered with indium/tin and tin oxides) were obtained by different methods (from suspension, by sol–gel, by vacuum sputtering). X-ray diffraction and positron annihilation depth-resolved characterization of these samples are presented. The data allow us to determine optimal deposition parameters, in order to obtain the anatase phase, important in practical applications in photoelectrochemical cells.
Effect of Reynolds number and lithium cation insertion on titanium anodization
2016
This work studies the influence of using hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during Ti anodization and Li+ intercalation on anatase TiO2 nanotubes. The synthesized photocatalysts were characterized by using Field Emission Scanning Electron Microscope (FE-SEM), Raman Confocal Laser Microscopy, Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky analysis (M-S), photoelectrochemical hydrogen production and resistance to photocorrosion tests. The obtained results showed that the conductivity of the NTs increases with Li+ intercalation and Re. The latter is due to the fact that the hydrodynamic conditions eliminate part of the initiation layer formed over the tu…
Removal of Surface Oxygen Vacancies Increases Conductance Through TiO(2) Thin Films for Perovskite Solar Cells
2019
[Image: see text] We report that UV–ozone treatment of TiO(2) anatase thin films is an efficient method to increase the conductance through the film by more than 2 orders of magnitude. The increase in conductance is quantified via conductive scanning force microscopy on freshly annealed and UV–ozone-treated TiO(2) anatase thin films on fluorine-doped tin oxide substrates. The increased conductance of TiO(2) anatase thin films results in a 2% increase of the average power conversion efficiency (PCE) of methylammonium lead iodide-based perovskite solar cells. PCE values up to 19.5% for mesoporous solar cells are realized. The additional UV–ozone treatment results in a reduced number of oxygen…
TiO2 nanostructures prepared by ferrocene/cobalt catalyst agents
2008
We present the growth and characterization of TiO2 nanocrystals. Nanostructured growth is obtained in a low-pressure CVD system by using an organometallic precursor Ti(OC3H7)4 as both the Ti and O source catalyzed by both ferrocene (an organometallic precursor) and cobalt metallic clusters prepared by the microwave-assisted polyol method. Two kinds of TiO2 structures were obtained in the cobalt clusters: a) pine-tree like (with short-leaf structure) and b) long-leaf structures as large as a few micrometers in size and both under 10 nm in thickness. Long-leaf TiO2 structures were grown at cobalt grain boundaries. For the growth conditions utilized, the TiO2 structures are composed of both an…
Highly stable defective TiO2-x with tuned exposed facets induced by fluorine: Impact of surface and bulk properties on selective UV/visible alcohol p…
2020
Abstract Titanium dioxide samples were prepared in the presence of different amounts of fluorine via hydrothermal method. It has been found that the presence of fluoride influenced the physico-chemical properties of TiO2 in various ways as polymorphic form stability, surface hydroxylation, generation of hydroxyl radicals under irradiation and formation of Ti3+ centers and oxygen vacancies. The generation rate of OH radicals was investigated by the photoluminescence technique in the presence of terephthalic acid. X-ray diffractometry indicated that fluorine stabilized the anatase TiO2. X-Ray photoelectron spectroscopy (XPS) revealed the presence of fluorine on the surface and the shift of th…
Electrochemical Investigation of Lithium Intercalation in MOCVD Derived Nanostructured Anatase/Rutile TiO2
2011
In this paper we report on the lithium reversible storage in titanium dioxide (TiO2) prepared by metal-organic chemical vapor deposition (MOCVD). Electrochemical properties in terms of lithium reversible insertion depend on the deposited microstructure. For thick films deposited on silicon wafer electrochemical activity of the anatase type of TiO2 is registered in the potential range 1.8-2.1 V vs. Li. For thinner films the intercalation reaction takes place in two potential ranges: 1.8-2.1 V vs. Li and below 1.4 V vs. Li. The second electroactivity range is attributed to lithium insertion into rutile. We found that the decrease of the lower potential limit (0.5 V instead of commonly used 1 …