Search results for "Titan"

Photocatalytic oxidation of acetonitrile in aqueous suspension of titanium dioxide irradiated by sunlight

2004

The photocatalytic oxidation of acetonitrile (CH3CN) was carried out in aqueous suspensions of polycrystalline TiO2 P25 Degussa irradiated by sunlight. A plug flow photoreactor in a total recycle loop was used for carrying out reactivity experiments in which the concentrations of acetonitrile, of its intermediate oxidation products and of not-purgeable organic carbon (NPOC) were monitored. The influence of the presence of strong oxidant species (H2O2, S2O82−, ClO−) on the process rate was studied. The dependence of acetonitrile photo-oxidation rate on the substrate concentration and on the catalyst amount was also investigated. The photodegradation rate of substrate and NPOC followed first …

A Straightforward Route to Homoallyl-Homocrotylamines Promoted by a Titanium Complex

2012

I�-Allyltitanium complexes, generated in situ from 1,3-dienes and Cp2TiH, react with benzotriazole derivatives to give homoallylic amines in good yields. Under similar conditions, triple cascade reactions (allyltitanation followed by cationic 2-aza-Cope rearrangement followed by a second allyltitanation) occur from bis(benzotriazolyl) compounds affording a straightforward route to homoallyl-(E)-homocrotylamines. A theoretical study provides further insight into the factors that govern the selectivity of this sequence of reactions. The titanium-promoted reductive coupling of 1,3-dienes with bis(benzotriazolyl) compounds as substrates led selectively to homoallyl-homocrotylamines through a tr…

Redox properties of titanocene-pyrrole derivative and its electropolymerization

2001

A new titanocene dichloride derivative in which one cyclopentadienyl ligand (Cp) is functionalized with a pyrrolyl ring, Tc3Py (Cl2TiCpC5H4(CH2)3NC4H4), has been synthesized and characterized with NMR. Its redox properties have been studied by CV in acetonitrile (AN), tetrahydrofurane (THF) and dichloromethane (DCM), in comparison with unsubstituted titanocene dichloride (Tc) and pyrrole. Ti(IV/III) transition observed within the negative potential range is a quasi-reversible reaction in THF and DCM (but without a complete recuperation of the initial reagent in the back scan) while the reoxidation peak in AN is strongly shifted in the positive direction. These results are interpreted within…

Photoinduced Charge Separation of Self-Organized Semiconducting Superstructures Composed of a Functional Polymer-TiO2 Hybrid

2013

Some Aspects of the Influence of Particle Size on Properties and Behaviour of a Dielectric Material : Example of Barium Titanate

1989

Anybody agrees with the idea that particle size plays an important role in the behaviour of a polycrystalline material but very few studies are giving precise information about this role. In this paper some experimental results are presented succintly to illustrate the importance of this physico-chemical factor. They are related to barium titanate, the main component of the dielectric material in the type II ceramic capacitors.

Electronics and Electromagnetism

2007

Oxidation of Titanium, Zirconium and their Alloys, Texture of their Oxide Scales

1994

Synthesis of Lead Zirconate Antiferroelectric Thin Films by Sol-Gel Processing

2000

A modified methoxyethanol sol-gel process was used for the production of PbZrO3 thin films. The new route uses lead oxide [PbO] instead of lead acetate [Pb(OAc)2]. Through the use of this method it is possible to prepare single-phase perovskite materials with improved properties. Examples are given for PbZrO3 thin layers deposited by the spin coating process on TiO2/Pt/TiO2/SiO2/Si substrates from various sols where lead acetate or lead oxide are used as the starting lead compound. The preferred orientation and the perovskite phase content of the films were studied using X-ray diffraction analysis (XRD). Scanning electron microscopy (SEM) was used for microstructural characterization of the…

Mechanism of redox transformation of titanocene dichloride centers immobilized inside a polypyrrole matrix—EQCM and XPS evidences

2005

Abstract We report electrochemical quartz crystal microbalance (EQCM) results for electrodeposition of titanocene derivatized polypyrrole p(Tc3Py) films and redox transformation of polypyrrole matrix and titanocene centers immobilized in the film. Films of p(Tc3Py), Tc3Py = Tc(CH 2 ) 3 NC 4 H 4 (Tc = Cl 2 TiCpCp′, Cp = C 5 H 5 , Cp′ = C 5 H 4 ) were obtained from acetonitrile solutions of monomer on a Pt disc or thin Au layer evaporated on 10 MHz quartz crystals. Polymerization efficiency, derived from the slope of the change of resonant frequency as a function of the deposition charge ranged from 54% to 75%. A gradual loss of redox activity of Tc centers during consecutive redox cycles of …

The Photocatalytic Activity of Novel, Substituted Porphyrin/TiO2-Based Composites

2010

Four novel porphyrins, 5-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,15-di-[3-(3-phenoxy)-propoxy] phenyl porphyrin, 5,10,15-tri-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,10,15,20-tetra-[3-(3-phenoxy)- propoxy]phenyl porphyrin, and their corresponding Cu(II) porphyrins, were synthesized and characterized spectroscopically. The photodegradation of 4-nitrophenol in aq. suspension was used to determine the photocatalytic activity of polycrystalline TiO2 samples which had been impregnated with the Cu(II) porphyrins, as sensitizers. The photocatalytic activity of the composite depends mainly on the amount of sensitizer on the TiO2 surface rather than the nature of the substituted porphyrins.