Search results for "GST"
showing 10 items of 874 documents
Scanning tunneling microscopy investigation of tricycloquinazoline liquid crystals on gold
2000
Self-assembled monolayers (SAMs) of hexaalkylthioether derivatives of tricycloquinazoline (TCQ) on Au(111) and tungsten diselenide (WSe2) were investigated by scanning tunneling microscopy (STM). The Au(111) surfaces were found to be etched by the thioether containing solutions. Corroded surfaces which are similar to gold surfaces that were coated with SAMs of thiols or disulfides were revealed by STM. Atomic adsorption spectroscopy proved that an amount of gold that corresponds to ca. 30% of a monolayer was dissolved in the assembly solutions. On gold, the aromatic cores of the molecules were found to be in face-on orientation. The alkyl substituents were in most cases folded upwards and s…
Evaporation of tungsten oxides: A mass-spectrometric study of the vapour contents
1995
Abstract The evaporation of bulk oxides of WO2 and WO3 and oxidised tungsten surfaces (metallic tungsten heated in an oxygen atmosphere) have been studied by the means of mass-spectrometry. The principal constituents of the vapour are found to be molecules of WO2, WO3, W2O6 and W3O9. These results differ from earlier reports, where the presence of molecules smaller than W3O9 in the mass-spectrum was interpreted as an artifact due to electron impact dissociation of larger polymers.
Photocatalytic oxidation of trans-ferulic acid to vanillin on TiO2 and WO3-loaded TiO2 catalysts
2015
Abstract The photocatalytic oxidation of trans-ferulic acid to vanillin in water has been studied by using various TiO2 and WO3-loaded TiO2 samples as catalysts. Different values of selectivity were obtained depending on the physico-chemical properties of the single samples and a vanillin selectivity of 10% was reached in the presence of the commercial TiO2 Merck. Higher selectivity values were obtained by impregnation of TiO2 with H2WO4 followed by calcination. The increased production of vanillin exhibited by the obtained WO3-loaded TiO2 powders was attributed to a reduced further oxidation of the aldehyde caused by the presence of the practically inactive tungsten trioxide hydrate on the…
Properties of Multi Phase Interfaces on the Tungsten Trioxide Particles in the Thin Films
2000
A wide spectrum of physical and chemical properties of thin films of tungsten trioxide compounds depend on composition, constitution and structure of the film, interaction with environment, and the type of external influences/excitations. The reason is the non-stoichiometric nature of transition metal oxides and properties of d-electrons. The short range order of non-stoichiometric compounds or phases of WO3 has a strong perovskite arrangement of tungsten and oxygen ions [1, 2]. The smallest crystalline clusters of perovskite short range order consist 6÷9 of [WO6]-octahedrons. One of the structural peculiarities-features of tungsten trioxide, related to non-stoichiometry, is a variety of [W…
ChemInform Abstract: Electrical Breakdown and Pitting in Anodic Films on Tungsten in Halogen Ion-Containing Solutions.
1988
Abstract The systematic investigation of the anodic behaviour of W in halogen ion-containing solutions reveals noticeable differences in the presence of different anions. Strong generalized dissolution is observed in fluoride solutions, the oxide growth being hindered at low anodizing current densities. Sparking phenomena occur in the presence of Br− and I− anions as in nitrate and sulphate solutions. Only in Cl− containing solutions is the growth of the anodic films limited by the occurrence of pitting phenomena at a critical thickness of the oxide. The laws of dependence of the phenomenon on the experimental parameters and the influence of ferrous ions on the voltage at which pitting occu…
Complexes of tungsten (VI) with tartaric acid. Comparative study of the various schemes of formation
1981
The complex formation occurring between tungstic acid and tartaric acid has been investigated in order to explain the optical activity of tartaric acid in the presence of constant amounts of tungstic acid. A new scheme of formation that includes three different complexes is presented, which explains the experimental results found in the literature.
IR Spectroscopy of Monoclinic Tungsten Oxide
2000
Stoichiometric tungsten trioxide WO3 has several polimorphous crystal phases [1] in the temperature region from 4 up to 1200K. These WO3 phases have more or less distorted ReO3 — type crystal structures, and ReO3 lattice topology is identical to topology of the BO3 sublattice of perovskite ABO3.
From Single Molecules to Nanoscopically Structured Functional Materials
2006
AbstractThe synthesis of MS2 (M = Mo, W) onion-like nanoparticles by means of a high temperature MOCVD process starting from W(CO)6 and elemental sulfur is reported. The reaction can also be carried out in two steps where the intermediate amorphous WS2 nanoparticles formed through the high temperature reaction of tungsten and sulfur in the initial phase of the reaction are isolated and converted in a separate annealing step to onion-type WS2 nanoparticles. Based on a study of the temperature dependence of the reaction a set of conditions could be derived where onion-like structures were formed in a one-step reaction. Onion-like structures obtained in the single-step process were filled, whe…
Preparation and Characterization of Tungsten Chalcogenide Photocatalysts
1997
Tungsten chalcogenides powders have been prepared by sulfidation of WO3 with gaseous H2S. Different mixed WS2/WO3 systems have been obtained by varying the amount of initial WO3 powder, the time, o...
ChemInform Abstract: Preparation and Characterization of Tungsten Chalcogenide Photocatalysts.
2010
Tungsten chalcogenides powders have been prepared by sulfidation of WO3 with gaseous H2S. Different mixed WS2/WO3 systems have been obtained by varying the amount of initial WO3 powder, the time, o...