Search results for "Tungsten oxide"
showing 7 items of 7 documents
Solvothermal Synthesis of Molybdenum–Tungsten Oxides and Their Application for Photoelectrochemical Water Splitting
2018
Molybdenum and tungsten oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystalli...
Evidence of hexagonal WO3 structure stabilization on mica substrate
2009
International audience; WO3 nanorods are grown by a simple vapor deposition method on a mica substrate and characterized by Selected Area Electron Diffraction and Energy Dispersive X-rays Spectroscopy. Experimental results show the clear evidence of an unexpected WO3 hexagonal structure as well as an epitaxial growth on the mica substrate. Besides, potassium is evidenced inside the nanorods. It is thus deduced that a metastable WO3 hexagonal phase is stabilized by epitaxy through a tungsten bronze interlayer having same hexagonal structure.
Structure and composition of sputter-deposited nickel-tungsten oxide films
2011
Films of mixed nickel-tungsten oxide, denoted NixW1-x oxide, were prepared by reactive DC magnetron co-sputtering from metallic targets and were characterized by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy, X-ray diffractometry and Raman spectroscopy. A consistent picture of the structure and composition emerged, and at x<0.50 the films comprised a mixture of amorphous WO3 and nanosized NiWO4, at x = 0.50 the nanosized NiWO4 phase was dominating, and at x>0.50 the films contained nanosized NiO and NiWO4.
Phase Composition and Morphology of Tungsten Oxide Nanoparticles Produced via a Pyrolytic Process
2018
The chemical synthesis is a leading route for the purposeful design of nanomaterials, whereas the tungsten oxides are employed in a variety of special applications. The production of nanomaterials by traditional synthetic methods is still a cumbersome multistep procedure. Here we propose an improved method to produce tungsten oxide nanoparticles via a pyrolytic process. A tungsten-containing precursor was prepared by liquid extraction using n-trioctylamine (C8H17)3N solution in toluene. We have shown that the conditions of thermal treatment of the W-based precursor determine the crystalline structure and nanomorphology of the final product. Monoclinic WO3 nanocrystallites are produced condu…
Structure et croissance de nanophases supportées d'oxyde de tungstène
2010
Tungsten trioxide nanorods can be elaborated on muscovite mica substrate through simple vapor deposition method. Growth of rods seems to follow a Stranski-Krastanov model. Their crystallography was investigated by TEM and reveals the presence of hexagonal phase. Such a metastable structure occurs from an interfacial hexagonal tungsten bronze which grows epitaxially on the substrate. This bronze phase contains potassium atoms coming from mica. Concerning the thickest rods, a monoclinic phase grows on the top of the hexagonal one. The hexagonal structure is thermally very stable: after annealing at 600°C, this phase is still detected whereas the rod morphology is destroyed. This point seems t…
Ab initio study of tungsten trioxide WO3 in volume and surface area
2012
The structure and stability of different crystallographic phases of tungstentrioxide and the effect of potassium doping have been studied using ab initiocalcuations, both in the bulk and at the surface. The study was motivatedby experimental works on the growth of WO3 nanorods on a mica substrate.The nanorods adopt a hexagonal phase, which is metastable in bulk WO3.The first part of the manuscript reports the study of bulk WO3. For thehexagonal and monoclinique phase, the atomic structure is deterimined andcompared with different models that have been proposed in the experimentalliterature. The relative stability of the two phases is calculated as a functionof potassium doping. From this an…
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.