Microstructure, Optical and Electrochromic Properties of Sol-gel Nanoporous Tungsten Oxide Films PDF Download
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Author: Y. Djaoued
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Author: Y. Djaoued
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Author: P. Judeinstein
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ISBN:
Category :
Languages : en
Pages : 8
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Amorphous tungsten oxide layers are deposited via the sol-gel route. Aqueous solutions of tungstate salts (Na2WO4) or chloroalkoxides (WOC12(OPri)2) provide cheap and suitable precursors for the synthesis of W03, nH20 colloidal solutions. Layers of large area can be deposited by spray or dip-coating. They exhibit electrochromic properties and could be used for making display devices or smart windows. Their electrochromic properties depend on the structure of the oxide network and the amount of water of the W03, nH20 layers. Switching time and stability decrease when n increases due to faster ion diffusion. Optical absorption arising from electron delocalization varies with the crystalline structure of the oxide network. Both the structure and the hydration state of the layers depend on the experimental procedure. It is therefore possible to optimize the electrochromic properties of sol-gel derived layers.
Author: Douglas John Taylor
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Category :
Languages : en
Pages : 0
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Author: Michael Walter Russell
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Category :
Languages : en
Pages : 382
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Author: Geoffrey Momanyi
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Category : Semiconductors
Languages : en
Pages : 0
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Metal oxide semiconductor materials such as tungsten oxide are promising candidates for use as photoanodes in solar water splitting. Tungsten oxide is an n-type semiconductor that was prepared on stainless steel 304 substrate and subsequently studied for water-splitting applications. This study investigated the effect of the annealing temperature and substrate cleaning reagents on the photoelectrochemical (PEC) properties of tungsten oxide thin films. The main method of synthesis employed was the sol-gel method. Tungsten oxide thin films were deposited from a precursor solution of peroxotungstic acid by doctor blading. The as-deposited amorphous WO3 films were further subjected to heat treatment at various annealing temperatures (200 °C, 300 °C, 400 °C, and 500 °C) to transform the amorphous material into polycrystalline WO3 nanostructures. Surface morphology, the crystallinity of the film, the thickness of the film, and photoelectrochemical properties were investigated using scanning electron microscopy, (SEM), X-ray diffractometry (XRD), stylus profilometry, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The optimal WO3 film, at a thickness of 5 μm and annealed at 400 °C, achieved a photocurrent density of 98.0 μA/cm2 at an applied voltage of 0.53 V vs Ag/AgCl. It is essential to treat the substrate with HNO3 to passivate the surface of the stainless-steel substrate with the Cr2O3 layer.
Author: Shona Margaret Christie
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ISBN:
Category :
Languages : en
Pages : 166
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Author:
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Category :
Languages : en
Pages :
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Xiv, 114 leaves : ill. ; 30 cm.
Author: Youssef Mosaddeghian Golestani
Publisher:
ISBN:
Category :
Languages : en
Pages : 101
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Electrochromic tungsten oxide nanostructures were prepared from tungsten oxide nanoparticles for the first time by the filtration and transfer technique. This novel and facile method for film preparation presents many advantages that include the possibility to obtain nanoparticle films with various porosities and compositions. The films obtained in the present work exhibited indeed porous structures and were generally composed of a mixture of nanoparticles. When the amount of the nanoparticles in the suspensions increased, we observed thicker films with higher coverage densities. Films prepared at room temperature exhibited very good electrochromic properties. It was found that annealing at 500oC increases the film stability and life time. Using cyclic voltammetry, fast diffusion behaviour (D of the order of 10-6 cm2s-1) for proton insertion/extraction has been observed. Moreover, fast switching response time (less than a second) during the bleaching process due to the rapid decay of the anodic current during chronoamperometry was also noted. The coloration efficiency for such devices was about 20 cm2C-1. The coloration of the films is associated with the number of color centers and depends on the number of inserted charges. However, we have shown that good optical reversibility does not necessarily need fast electrochemical kinetics. Finally, the effect of high applied potentials on the films was investigated, followed by an analysis of the electronic properties of the films.
Author:
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Category : Chemistry
Languages : en
Pages : 2540
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Author: Michael Schmitt
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Category :
Languages : en
Pages :
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