Tungsten oxides: general characterization

2005 ◽  
pp. 1-4
Author(s):  
Keyword(s):  
Tungsten Oxides ◽  
General Characterization

Síntesis sencilla de óxido de tungsteno(VI) a partir del filamento de un foco

2011 ◽  
Vol 19 (4) ◽  
pp. 341
Author(s):  
Joel Díaz Reyes ◽  
Aarón Pérez-Benítez ◽  
Valentín Dorantes
Keyword(s):  
Infrared Spectroscopy ◽  
High Temperatures ◽  
Power Supply ◽  
Light Bulb ◽  
Electrochromic Devices ◽  
Tungsten Filament ◽  
Tungsten Oxides ◽  
Ac Power

<span>Tungsten(VI) oxide can be easily synthesized starting from a standard light bulb. The reaction consists in the oxidation at high temperatures (T ≈ 2000 – 3000° C) of a tungsten filament in presence of air; conditions which can be easily achieved by connecting a broken light bulb (but with its intact filament) to an AC-power supply of 110 volts. The vapor of WO3 is condensed into a beaker in a quantity enough to be characterized by infrared spectroscopy. The experiment is very funny, inexpensive and allows to the teacher to link several topics in current chemistry and physics of the tungsten oxides, such as their nomenclature and technological applications (i.e. electrochromic devices, gasochromic sensors, superalloys or as it is used in home: As a “simple” emisor of light!).</span>

Why Does Rationality Matter?

2017 ◽  
Author(s):  
Ralph Wedgwood
Keyword(s):  
Mental States ◽  
External World ◽  
Dutch Book ◽  
Strong Sense ◽  
General Characterization ◽  
Internal Rationality

Internalism implies that rationality requires nothing more than what in the broadest sense counts as ‘coherence’. The earlier chapters of this book argue that rationality is in a strong sense normative. But why does coherence matter? The interpretation of this question is clarified. An answer to the question would involve a general characterization of rationality that makes it intuitively less puzzling why rationality is in this strong sense normative. Various approaches to this question are explored: a deflationary approach, the appeal to ‘Dutch book’ theorems, the idea that rationality is constitutive of the nature of mental states. It is argued that none of these approaches solves the problem. An adequate solution will have to appeal to some value that depends partly on how things are in the external world—in effect, an external goal—and some normatively significant connection between internal rationality and this external goal.

scholarly journals Influence of the Reduction Temperature and the Nature of the Support on the Performance of Zirconia and Alumina-Supported Pt Catalysts for n-Dodecane Hydroisomerization

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 88
Author(s):  
Diana García-Pérez ◽  
Maria Consuelo Alvarez-Galvan ◽  
Jose M. Campos-Martin ◽  
Jose L. G. Fierro
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Catalytic Properties ◽  
Catalytic Performance ◽  
Major Influence ◽  
Pt Catalysts ◽  
Reduction Temperature ◽  
Metal Dispersion ◽  
Tungsten Oxides ◽  
Supported Pt Catalysts

Catalysts based on zirconia- and alumina-supported tungsten oxides (15 wt % W) with a small loading of platinum (0.3 wt % Pt) were selected to study the influence of the reduction temperature and the nature of the support on the hydroisomerization of n-dodecane. The reduction temperature has a major influence on metal dispersion, which impacts the catalytic activity. In addition, alumina and zirconia supports show different catalytic properties (mainly acid site strength and surface area), which play an important role in the conversion. The NH3-TPD profiles indicate that the acidity in alumina-based catalysts is clearly higher than that in their zirconia counterparts; this acidity can be attributed to a stronger interaction of the WOx species with alumina. The PtW/Al catalyst was found to exhibit the best catalytic performance for the hydroisomerization of n-dodecane based on its higher acidity, which was ascribed to its larger surface area relative to that of its zirconia counterparts. The selectivity for different hydrocarbons (C7–10, C11 and i-C12) was very similar for all the catalysts studied, with branched C12 hydrocarbons being the main products obtained (~80%). The temperature of 350 °C was clearly the best reduction temperature for all the catalysts studied in a trickled-bed-mode reactor.

Highly stable electrochromic cells based on amorphous tungsten oxides prepared using a solution‐annealing process

2021 ◽  
Author(s):  
Tuan Van Nguyen ◽  
Kim Anh Huynh ◽  
Quyet Van Le ◽  
Hayeong Kim ◽  
Sang Hyun Ahn ◽  
...  
Keyword(s):  
Annealing Process ◽  
Solution Annealing ◽  
Tungsten Oxides

Strong coloration of nanoporous tungsten oxides by in-vacuo lithiation for all-solid-state electrochromic devices

2021 ◽  
pp. 138700
Author(s):  
Olivia Bouvard ◽  
Maxime Lagier ◽  
Luc Burnier ◽  
Anna Krammer ◽  
Andreas Schüler
Keyword(s):  
Solid State ◽  
Electrochromic Devices ◽  
Tungsten Oxides

Intergrowth of niobium tungsten oxides of the tetragonal tungsten bronze type

2020 ◽  
Vol 75 (11) ◽  
pp. 913-919
Author(s):  
Frank Krumeich
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tungsten Bronze ◽  
Structural Complexity ◽  
Dark Field ◽  
Tetragonal Tungsten Bronze ◽  
Tungsten Oxides ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractSince the 1970s, high-resolution transmission electron microscopy (HRTEM) is well established as the most appropriate method to explore the structural complexity of niobium tungsten oxides. Today, scanning transmission electron microscopy (STEM) represents an important alternative for performing the structural characterization of such oxides. STEM images recorded with a high-angle annular dark field (HAADF) detector provide not only information about the cation positions but also about the distribution of niobium and tungsten as the intensity is directly correlated to the local scattering potential. The applicability of this method is demonstrated here for the characterization of the real structure of Nb7W10O47.5. This sample contains well-ordered domains of Nb8W9O47 and Nb4W7O31 besides little ordered areas according to HRTEM results. Structural models for Nb4W7O31 and twinning occurring in this phase have been derived from the interpretation of HAADF-STEM images. A remarkable grain boundary between well-ordered domains of Nb4W7O31 and Nb8W9O47 has been found that contains one-dimensionally periodic features. Furthermore, short-range order observed in less ordered areas could be attributed to an intimate intergrowth of small sections of different tetragonal tungsten bronze (TTB) based structures.

Production of hydrogen by ethanol steam reforming using Ni–Co-ex-hydrotalcite catalysts stabilized with tungsten oxides

2020 ◽  
Author(s):  
José L. Contreras ◽  
Anabel Figueroa ◽  
Beatriz Zeifert ◽  
José Salmones ◽  
Gustavo A. Fuentes ◽  
...  
Keyword(s):  
Steam Reforming ◽  
Ethanol Steam Reforming ◽  
Tungsten Oxides ◽  
Production Of Hydrogen ◽  
Ethanol Steam
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