Papers by Keyword: Tungsten Oxide

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Authors: Ying Ming Xu, Xiao Li Cheng, Li Hua Huo, Hui Zhao, Shan Gao, Xiao Hui Bai, Jian Ding, Zhi Wang
Abstract: The fiber shaped monoclinic tungsten oxides with high preferential orientation has been synthesized by dialysis and aging treatment at room temperature, of the white precipitates prepared from HCl acidified (NH4)10W12O41 solution. The microstructure evolution of the above tungsten oxide was studied by SEM. The morphology of the powder changed from irregularity to shuttle plate-like during short time dialysis in pure water, and the butterfly shape was obtained after long time treatment. It was found that the nano-particles were rearranged to form nano-fibers on the surface of the butterfly shaped oxide as a function of aging time when the butterfly powder was kept in the original mother liquor. Compared to butterfly oxide, the morphology of fibers exhibited much improved thermal stability. The photochromic property of the tungsten oxide with different morphology was studied. The response time in color change after irradiated by the UV output of a 30 W mercury lamp is 20 s in inert atmosphere and the recovery time in bleach is about 2 months.
Authors: Claes Goran Granqvist, E. Avendaño, A. Azens
Authors: Z. Ling, Colin Leach, Robert Freer
Authors: Prvan Kumar Katiyar, Navneet Singh Randhawa, Jhumki Hait, Ranajit Kumar Jana, K.K. Singh, T.R. Mankhand
Abstract: In the present paper, potentiodynamic studies of WC scrap have been carried out as these studies give better idea about the anodic dissolution behaviour of the scrap material to recover the metal values. However, it has been seen that anodic passivation retards the dissolution of the scrap and adversely affects the recovery of metals. To minimize the passivity and to increase the anodic dissolution, some chemicals are often used as additives. Two different electrolytes namely hydrochloric acid and aqueous ammonia at varying concentrations had been employed for the above studies. The additives citric acid and oxalic acid were added to the acidic electrolyte whereas ammonium chloride, ammonium carbonate and ammonium sulphate were added in different concentration to the ammoniacal electrolyte. The studies revealed that 2% citric acid in 1N HCl was the optimum to achieve maximum anodic dissolution (current) of WC scrap. On the other hand, 5% NH4Cl was found suitable to obtain maximum anodic dissolution (current) in the ammoniacal (150 g/L) medium. The potentiodynamic studies were followed by the actual electrodissolution experiments in an electrolytic cell with the help of a rectifier. The W and Co recoveries were encouraging.
Authors: Claes Goran Granqvist
Abstract: Chromogenic materials and devices allow the construction of glazings whose throughput of visible light and solar energy can be varied depending on the application of an electrical voltage or temperature. These glazings are of much interest for energy efficient buildings and are able to create energy efficiency along with indoor comfort. This paper outlines the basics of electrochromic and thermochromic technologies with foci on functional principles, materials, device and manufacturing technology, and selected results from research and development.
Authors: O. Goiz, F. Chávez, C. Felipe, R. Peña-Sierra, N. Morales
Abstract: The growth of tungsten oxide nanowires on silicon substrates without using any catalyst is demonstrated by means of close-spaced vapor transport (CSVT) technique at atmospheric pressure. The source was formerly prepared from a tungsten foil to produce a tungsten oxide film. CSVT array is completed with silicon substrates located at a distance of ~350 m over the tungsten oxide source at moderate temperatures (~750°C). Two distinct kinds of nanostructures were produced; a uniform distribution of free standing tungsten oxide wires of several micrometers in length with diameters less than 150 nm; and wires assembled to form nanowire bundle. The X-ray diffraction characterizations show that the phases of WO2.7 and WO2.9 are present.
Authors: F.C. Cheong, Y.W. Zhu, B. Varghese, Chwee Teck Lim, C.H. Sow
Abstract: A simple technique to synthesis crystalline Tungsten Oxide nanowires is presented. Using a standard thermal hotplate, a pure 99.9% tungsten foil is annealed to 484 ± 5 oC under ambient condition to generate vapor deposition of the heated materials on a piece of 150μm thick glass cover slide pressing on the tungsten foil. Tungsten oxide nanowires are found to deposit on the cover slide facing the heated tungsten foil. These tungsten oxide nanowires were characterized with SEM, TEM, EDX, micro-Raman and XRD. The crystalline nanowires were found to be straight and clean with a diameter of 10-300nm and a length of a few tens of micrometers.
Authors: Dan Ni Qu, Hai Feng Cheng, Yong Jiang Zhou, Xin Xing, Dong Qing Liu
Abstract: The mesoporous tungsten oxide (WO3) films were derived from the peroxotungstic acid (PTA) sol with templates through sol-gel method. Polyethylene glycol (PEG) 400 and tri-block polymer P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H) were chosen as templates. The structural, morphological, optical and electrochromic properties of the WO3 thin films derived from different sols were studied. The composition and crystal phase of the films change at different annealing temperatures. The films derived from the sols containing templates have higher crystallization temperature than those without templates. And the morphologies are distinctly different from different sols. The addition of the templates can improve the electrochromic properties of the WO3 films, and those prepared from the 3% of P123 sol show the best electrochromic properties. The highest transmittance modulation is near 60%, and the largest ion inserted and deinserted diffusion coefficient can reach 5.706×10-12 cm2/s and 1.271×10-11 cm2/s, respectively.
Authors: Bo Liu, Ben Xue Zou
Abstract: A porous copper/tungsten oxide (WO3)/polyaniline (PANI) composite modified electrode CuWP was fabricated by electrochemical deposition of copper nanosheets on WO3/PANI composite. The CuWP exhibited higher electrocatalytic activity for nitrate reduction than the similarly prepared copper modified electrode due to the larger surface area of CuWP and the synergistic catalytic effect of copper and WO3/PANI. The linear scan voltammetry results showed a good linear relationship between nitrate reduction current and concentration of nitrate from 40 to 276 μM, with a sensitivity of 4.5 μA/μM and detection limit (S/N=3) of 1.2 μM. The CuWP modified electrode was tried to be employed in determination of nitrate in drinking water.
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