Tungsten oxide studies

The four doped tungsten oxide catalysts (noted above) were synthesized and used in this study. The catalysts were analyzed by scanning electron microscopy (SEM), x-ray difBaction (XRD), and electron... 

The properties of a tungsten oxide monolayer on 0.18 pm silica particles were studied by Leland and Bard The material was prepared by a controlled WCI hydrolysis technique. These particles differ from the colloidal Q-particles that they are small in only one dimension thus these layers are related to the semiconductor... 

Other materials such as gold (< = 4.9 eV), aluminum (< = 4.2 eV), indium-doped zinc oxide, magnesium indium oxide, nickel tungsten oxide, or other transparent conductive oxide materials, have been studied as anodes in OLEDs. Furthermore, the WF of ITO can be varied by surface treatments such as application of a very thin layer of Au, Pt, Pd, or C, acid or base treatments, self-assembly of active surface molecules, or plasma treatment. 

Apart from titanium oxide, two other carbon-modified semiconductors were studied in water photoelectrolysis due to their low band gap energy, namely iron (Fe203) and tungsten oxide (W03) [70,90]. Carbon-modified iron oxide demonstrated promising photoconversion efficiency, 4 % and 7 % for modified oxides synthesized in oven and by thermal oxidation respectively [90]. Also, carbon-modified tungsten oxide (C-W03) photocatalysts exhibited a 2 % photoconversion efficiency [70],... 

Vapor deposition techniques have been extensively studied for the fabrication of metal and metal oxide structures. Indeed, the first reported tungsten oxide nanorods were essentially grown by this method. This groundbreaking synthesis of W02.72 leaves room for improvement, however, as it requires a reaction temperature of 1600°C in an argon atmosphere. Additionally, the researchers found the reaction product to be commingling WO2.72 nanorods and WO3 platelets rather than pure nanorods. Later,... 

Though they utilized a novel hollow-sphere form of WO3 rather than WO2 72 nanorods, the work of Li s group in researching tungsten oxide as gas sensors can be applied to thenanorodform. Li sporous, hollow spheres were substituted for tungsten oxide polycrystalline films used in the previous studies by Galatsis et al. and Choi et Thus, they overcome the sensitivity and selectivity problems caused by the... 

Because of their electronic properties, particularly their visible-ultraviolet band gap, tungsten oxides have been the focus of a number of catalysis studies. Kohler and Gopel examined the electrocatalytic properties of W02.72 using spectroscopic surface... 

The effect of electron transfer between tungsten oxide and titanium oxide is also important in photochromatic applications. In an excellent study of aqueous sols. He et al. analyze the electronic structure of the tungsten oxide-titanium oxide system, finding that titanium oxide can catalyze the generation of W+. This state is a colored state and can be generated from WO3 WH2O by the following reactions ... 

T. Lindgren, Photo Induced Oxidation of Water at Thin Film Electrodes A study of Tungsten Oxide, Herruitite, Indium Nitride and Tin Nitride, in Department of Physical Chemistry. 2001, Uppsala... 

Iron oxide (Fe Oj) and tungsten oxide (WO ) films have been studied and developed as candidate semiconductor materials for the PEC junction (photoanode). High-temperature synthesis methods, as reported for some high-performance metal oxides, have been found incompatible with multijunction device fabricatioa A low-temperature reactive sputtering process has been developed instead. In the parameter space investigated so far, the optoelectronic properties of WO3 films were superior to those of Fe Oj films, which showed high recombination of photogenerated carriers (Miller et al., 2004). 

Application of Raman spectroscopy to a study of catalyst surfaces is increasing. Until recently, this technique had been limited to observing distortions in adsorbed organic molecules by the appearance of forbidden Raman bands and giant Raman effects of silver surfaces with chemisorbed species. However, the development of laser Raman instrumentation and modern computerization techniques for control and data reduction have expanded these applications to studies of acid sites and oxide structures. For example The oxidation-reduction cycle occurring in bismuth molybdate catalysts for oxidation of ammonia and propylene to acrylonitrile has been studied in situ by this technique. And new and valuable information on the interaction of oxides, such as tungsten oxide and cerium oxide, with the surface of an alumina support, has been obtained. 

There are no indications that the molybdenum oxides considered exhibit variations of lattice dimensions which would indicate extended homogeneity ranges. They form well developed crystals which give excellent x-ray photographs and they are stable in air up to about 200° C. The crystal structures of all of them have now been studied. They often possess a basic structure, which provides a basis for classification. Such a classification is illustrated in Table II here the known tungsten and mixed molybdenum-tungsten oxides have also been listed, since they fit naturally into such a scheme. 

XPS and Electrochemical Studies on Tungsten-Oxidizer Interaction in Chemical Mechanical Polishing... 

Electrochemical interaction between the oxidizer and the metal is believed to play a key role in material removal in tungsten CMP. In this study, we use X-ray Photoelectron Spectroscopy (XPS) in conjunction with electrochemical measurements in both in-situ polishing conditions as well as in static solutions, to identify the passivation and dissolution modes of tungsten. Dissolution of tungsten oxides was found to be the primary non-mechanical tungsten removal mechanism in CMP. 

In an earlier study we had reported the XPS analysis of tungsten oxides formed during anodic polarization experiments. It was determined that even at high applied potentials, the oxide thickness values are less than the mean free path of electrons in the oxides (generally assumed to be between 30 to 50 A ). Clearly the oxide growth in tungsten is a slow process. However, despite the relatively small thickness vsilues, the steady state current density during anodic polarization is restricted to a few tens of microamperes. 

Nozaki F, Ohki K (1972) A study of catalysis by uranium oxide and its mixed catalysis, 3. Comparison of uranium oxide catalysts with vanadium oxide, molybdenum oxide and tungsten oxide catalysts for catalytic oxidation of carbon monoxide. Bull Chem Soc Jap 45 9473... 

Transition Metal Salts and Oxides on Alumina. Transition metal salts, particularly chlorides and nitrates, are frequently used as starting materials for the preparation of supported transition metal oxides or supported precursors for supported metal catalysts. Also, many catalytic materials, particularly supported molybdenum and tungsten oxide and sulfide catalysts, contain transition metal ions, namely Co, Ni , and Fe " as promoters. Thus, it is interesting to study the spreading and wetting behavior of salts of these transition metals and of their oxides. This is of particular importance for promoted catalyst materials, since in practice the incorporation of the active phase and the promoter should be possible in one step for economic reasons. 

Further support for these structural inferences came from a detailed XAS study by Hilbrig et al. The pre-edge, XANES and EXAFS features of the samples also used for Raman spectroscopy were consistent with a highly dispersed tungsten-oxide phase consisting of a two-dimensional network of comer-linked WO5 and WO4 units, the... 

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