Search results for "Tungsten"

The reduction of tris-dithiolene complexes of molybdenum(vi) and tungsten(vi) by hydroxide ion: kinetics and mechanism

2004

The kinetic study of the spontaneous reduction of some neutral tris-dithiolene complexes [ML3] of molybdenum(VI) and tungsten(VI), (L = S2C6H42−, S2C6H3CH32− and S2C2(CH3)22−; M = Mo or W) by tetrabutylammonium hydroxide in tetrahydrofuran-water solutions demonstrates that OH− is an effective reductant. Their reduction is fast, clean and quantitative. Depending upon both the molar ratio in which the reagents are mixed and the amount of water present, one- or two-electron reductions of these tris-dithiolene complexes were observed. If Bu4NOH is present in low concentration or/and at high concentrations of water, the total transformation of the neutral M(VI) complex into the monoanionic M(V) …

CCDC 183766: Experimental Crystal Structure Determination

2002

Related Article: M.M.Kubicki, C.Barre, C.Moise|2002|Acta Crystallogr.,Sect.E:Struct.Rep.Online|58|m152|doi:10.1107/S1600536802004865

Improving the high temperature oxidation resistance of pure titanium by shot-peening treatments

2017

International audience; Shot-peening (SP) treatments have shown their capacity to improve the oxidation resistance of titanium and zirconium thanks to the large compressive stresses and the surface hardening induced by this mechanical process. However, shot-peening treatments can produce a surface chemical deposit, which can modify the high temperature oxidation resistance. Here, we study pure titanium samples shot-peened with different type of balls: tungsten carbide, alumina or glass. The oxidation behavior was studied at 700 °C in dry air by thermo gravimetric analysis for short isotherm oxidation periods up to 100 h. Also, long oxidation tests (3000 h) at 700 °C were performed with an i…

High-nuclearity Ni-substituted polyoxometalates: a series of poly(polyoxotungstate)s containing 20–22 nickel centers.

2011

Three high-nuclearity Ni-substituted polyoxotungstates (POTs)--[Ni(enMe)2(H2O)2]2[Ni(H2O)6]2[Ni(enMe)2][Ni(H2O)2]1.5[HNi20X4W34(OH)4O136(H2O)6(enMe)8]·11 H2O (3), [Ni(en)2(H2O)]2[H8Ni21X4W34(OH)4O136(en)10(H2O)5]·22 H2O (4), and [Ni(enMe)2]2[H6Ni22X4W34(OH)4O136(H2O)6(enMe)10]·18 H2O (5), in which en = ethylenediamine, enMe = 1,2-diaminopropane, X = 0.5 P+0.5 Ge--were made under hydrothermal conditions and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The structures of 3–5 can be viewed as novel derivatives of [H6Ni20P4W34(OH)4O136(enMe)8(H2O)6]·12 H 2O (1) and [Ni(en)2(H2O)]2[H8Ni20P4W34(OH)…

Efficient H2 production by photocatalytic water splitting under UV or solar light over variously modified TiO2-based catalysts

2019

Abstract This paper focused for the first time on the comparison between three different approach to modify the chemico-physical properties of TiO2-based photocatalysts and their effect in the H2 production by photocatalytic water splitting both under UV and solar light irradiation, under the same experimental conditions. The application of pulsed laser irradiation to aqueous TiO2 suspensions (first approach) induced structural transformations both on the bulk and on the surface of TiO2, boosting the H2 production, under UV light irradiation, of almost three times (20.9 mmol/gcat·h) compared to bare TiO2 (7.7 mmol/gcat·h). The second strategy was based on a templating method to obtain TiO2 …

Tungsten-titanium mixed oxide bronzes: Synthesis, characterization and catalytic behavior in methanol transformation

2019

[EN] Tungsten oxide bronze-based materials show extremely adaptive structural and compositional features that make them suitable for functional properties modulation. Herein we report the preparation of a series of Ti-containing tungsten oxide catalysts presenting a hexagonal tungsten bronze-type structure. The insertion of Ti4+ within the structure (likely in the octahedral framework of the hexagonal tungsten bronze) leads to an increase in the number of strong acid sites, and the disappearance of W5+ surface species found in the undoped tungsten oxide. With the aim of studying the acid-redox properties of the titled catalysts, the catalytic transformation of methanol has been carried out …

Growth of metal/oxide periodic multilayer : relation between structure and electrical behaviour in systems based on titanium and tungsten

2014

Periodic multilayers have found many applications in the fields of optics, mechanics or electronics. However, few studies focus on the electrical responses of the metal/oxide periodic structures versus temperature. The interest of this work was focused on the characterization of the multilayers and their electrical properties versus temperature. In TiO/Ti/TiO/TiO2 and WO/W/WO/WO3 systems produced by the reactive gas pulsing process, sample structures were established by transmission electron microscopy for sublayers thicknesses between 1.3 and 50.8 nm. Then, this study highlights a modification of conventional electrical behavior versus temperature. An empirical relationship was established…

Dioxomolybdenum(VI) and -tungsten(VI) complexes with tetradentate aminobis(phenol)s

2006

Abstract Aminobis(phenol) ligands (H2Ln) carrying either a dimethylamino, a pyridyl or a methoxy sidearm donor were used in the preparation of new tungsten and molybdenum complexes. Treatment of [W(eg)3] (eg = 1,2-ethanediolate dianion) with H2Ln under hydrolytic conditions in a CHCl3–MeOH mixture gave the cis-dioxotungsten(VI) complexes [WO2(Ln)] in good yields. The corresponding molybdenum complexes [MoO2(Ln)] were prepared from [MoO2(acac)2] and respective ligands. The solid-state structures of two molybdenum and one tungsten compounds were determined by single crystal X-ray diffraction, which revealed that the dianionic aminobis(phenolate) backbones of the ligands have coordinated to th…

On the choice of tool material in friction stir welding of titanium alloys

2012

Surface Defects as a Tool to Solubilize and Functionalize WS 2 Nanotubes

2017

Layered transition metal dichalcogenides contain a number of crystal defects which significantly change their properties may be beneficial or detrimental for a specific application. We have prepared defect-rich multiwalled WS2 nanotubes by reductive sulfidization of W18O49 nanowires that were obtained solvothermally from tungsten chloride in different alcohols. The synthesis of the W18O49 nanowires was monitored and their morphological characteristics (e. g. length, rigidity and aspect ratio) are described in detail. The effect of morphology of the nanowires on the synthesis of WS2 nanotubes was investigated in order to obtain WS2 nanotubes that are highly solvent dispersible. Dispersions o…