Letteratura scientifica selezionata sul tema "Tungsten oxide gel"
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Articoli di riviste sul tema "Tungsten oxide gel":
1
Zhang, Zeng Hai, Guang Ming Wu, Guo Hua Gao, Wei Feng, Xiao Bo Jin e Jun Shen. "Structural Study of WO3 and MoO3 Compound Films in H2 Gasochromism". Key Engineering Materials 537 (gennaio 2013): 184–88. http://dx.doi.org/10.4028/www.scientific.net/kem.537.184.
Abstract (sommario):
Sol-gel tequnique was used to prepare disordered tungsten oxide and molybdenum oxide sols. A series ratio of W:Mo compound sols were obtained via mettalic powder co-peroxided by H2O2 as precursors in ethonal. Compound films were achieved by dip-coating method. Fourier Transform Infrared Spectroscopy, Raman Spectroscopy were taken to characterize the structure of these compound films. Uv-visible Spectroscopy was used to test the gasochromic property. The results showed that the gasochromics property was much different from that of pure tungsten oxide and molybdenum oxide sol-gel thin films. The effect was origined from the structrue alteration, which was not due to the spectrum superposition but the co-reaction of W and Mo.
2
Kim, Chang Yeoul, Seong Geun Cho, Seok Park, Tae Yeoung Lim e Duck Kyun Choi. "Electrochemical and Optical Properties of WO3 Prepared by Sol-Gel Coating". Materials Science Forum 544-545 (maggio 2007): 1081–84. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.1081.
Abstract (sommario):
Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by a sol-gel dip coating method. The thermal analysis was conducted by DSC/TG method. A DSC/TG analysis and the XRD patterns showed that a tungsten oxide crystal phase was formed at 400oC. WO3 thin film when heat-treated at 300oC was amorphous and had a better electrochemical property than that of the crystalline phase. Crystallization of tungsten oxide decreased active sites of ion intercalation so that the current density decreased with heat-treatment temperature.
3
Mushtaq, Khizar, Pui May Chou e Chin Wei Lai. "Review on the Synthesis Methods of Nano-Tungsten Oxide Dihydrate Colloid". MATEC Web of Conferences 335 (2021): 03008. http://dx.doi.org/10.1051/matecconf/202133503008.
Abstract (sommario):
Tungsten being a transition element, forms oxide compounds of various oxidation states that enables it to form nanocolloids of tungsten oxide dihydrate. Multiple methods have been used in recent years to synthesize nano tungsten oxide dihydrate, including sol-gel synthesis, electrochemical deposition, hydrothermal synthesis and anodization. However, a universally accepted synthesis method for this material is not offered. The most appropriate method and its corresponding processing parameters for the synthesis of nano tungsten oxide dihydrate colloids were presented in the present study. The objective of the present study was to investigate the effect of processing parameters, i.e. applied voltage, temperature and anodizing duration on the particle size of nanocolloids. It is found that anodization is the easiest, efficient, and cost-effective method to synthesize the colloidal solution of nano tungsten oxide dihydrate. Conducting the synthesis at room temperature at a voltage of 50 V for 60 minutes yields the product with particle size of 40 – 60 nm, which can be used in wide array of applications. This paper also highlights the research gaps for future work and gives recommendations to extend this study particularly for the industrial application of tungsten oxide.
4
Özkan, E., e F. Z. Tepehan. "Optical and structural characteristics of sol–gel-deposited tungsten oxide and vanadium-doped tungsten oxide films". Solar Energy Materials and Solar Cells 68, n. 3-4 (giugno 2001): 265–77. http://dx.doi.org/10.1016/s0927-0248(00)00361-5.
5
Santos Garcia, Irene Teresinha, e Diego Soares de Moura. "Sodium tetratungstate/tungsten oxide films prepared with dodecyltrimethylammonium chloride as structuring agent". Revista Eletrônica Científica da UERGS 8, n. 3 (23 dicembre 2022): 218–27. http://dx.doi.org/10.21674/2448-0479.83.218-227.
Abstract (sommario):
Abstract
The multiple forms of structuring transition metal anions in solution are important aspects to be taken into account in obtaining oxides of these metals by the sol-gel method. The formation of polyanions in aqueous media can produce a variety of structures in the solid state. Films were obtained through sol-gel method with sodium tungstate as precursor and dodecyltrimethylammonium chloride (DTAC) as structuring agent, after calcined at 700 °C in air. The films, structured as nanospheres, were composed mainly of triclinic sodium tetratungstate and monoclinic tungsten oxide. The cationic surfactant interacts in aqueous media with the precursor, affecting the obtained films' final morphology, without affecting their crystal structure. Their photocatalytic properties were also evaluated.
Keywords: Colloidal synthesis; sol-gel; photocatalysis.
Resumo
Filmes de tetratungstato de sódio/óxido de tungstênio preparados com cloreto de dodeciltrimetilamônio como agente estruturante
As múltiplas formas de estruturação de ânions de metais de transição em solução revelam aspectos importantes a ser levados em consideração na obtenção de seus óxidos pelo método sol-gel. Um desses aspectos é a formação de poliânions em meio aquoso, que pode produzir uma variedade de estruturas no estado sólido. Desta feita, foram obtidos filmes através do método sol-gel utilizando-se, como precursor, de tungstato de sódio e, como agente estruturante, cloreto de dodeciltrimetil amônio, que foram posteriormente calcinados a 700 ºC em ar. Observou-se que os filmes, estruturados como nano esferas, eram compostos principalmente de tetratungstato de sódio triclínico e óxido de tungstênio monoclínico. Por sua vez, conclui-se que o surfactante catiônico interage em meio aquoso com o precursor e afeta a morfologia final dos filmes obtidos, no entanto tem pouca influência nas suas estruturas cristalinas. Faz-se importante destacar que as propriedades fotocatalíticas foram também avaliadas na presente pesquisa.
Palavras-chave: Síntese coloidal; sol-gel; fotocatálise.
Resumen
Películas de tetratungstato de sodio/óxido de tungsteno preparadas con cloruro de dodeciltrimetilamonio como agente estructurante
Las múltiples formas de estructurar los aniones de metales de transición en solución son aspectos importantes a tener en cuenta a la hora de obtener sus óxidos por el método sol-gel. La formación de polianiones en medios acuosos puede producir una variedad de estructuras en estado sólido. Se produjeron películas por medio del método sol-gel utilizando tungstato de sodio como precursor y cloruro de dodeciltrimetilamonio como agente estructurante, luego calcinadas a 700 ºC en aire. Las películas, estructuradas como nanoesferas, estaban compuestas principalmente de tetratungstato de sodio triclínico y óxido de tungsteno monoclínico. El tensioactivo catiónico interactúa en medio acuoso con el precursor, afectando la morfología final de las películas obtenidas, pero tiene poca influencia sobre su estructura cristalina. Fueron evaluadas también las propiedades fotocatalíticas.
Palabras clave: Síntesis coloidal; sol-gel; fotocatálisis.
6
Chai, Y., F. Y. Ha, F. K. Yam e Z. Hassan. "Fabrication of Tungsten Oxide Nanostructure by Sol-Gel Method". Procedia Chemistry 19 (2016): 113–18. http://dx.doi.org/10.1016/j.proche.2016.03.123.
7
Vidmar, Tjaša, Marko Topič, Petr Dzik e Urša Opara Krašovec. "Inkjet printing of sol–gel derived tungsten oxide inks". Solar Energy Materials and Solar Cells 125 (giugno 2014): 87–95. http://dx.doi.org/10.1016/j.solmat.2014.02.023.
8
Baker, A. P., S. N. B. Hodgson e M. J. Edirisinghe. "Production of tungsten oxide coatings, via sol–gel processing of tungsten anion solutions". Surface and Coatings Technology 153, n. 2-3 (aprile 2002): 184–93. http://dx.doi.org/10.1016/s0257-8972(01)01673-5.
9
Dulgerbaki, Cigdem, Aliihsan Komur e Aysegul Uygun Oksuz. "Tungsten Oxide Nanofibers for Electrochromic Device Application". Academic Perspective Procedia 1, n. 1 (9 novembre 2018): 902–10. http://dx.doi.org/10.33793/acperpro.01.01.152.
Abstract (sommario):
The tungsten oxide (WO3) nanofibers were grown directly onto an ITO-coated glass via an electrospinning method for electrochromic applications. The electrochromic properties of WO3 nanofibers were investigated in the presence of different electrolytes including a series of ionic liquids and classic LiClO4-PC system. A significant optical modulation of 20.82% at 760 nm, reversible coloration with efficiency of 64.58 cm2/C and excellent cycling stability were achieved for the nanofiber electrochromic device (ECD) with ionic liquid based gel electrolyte.
10
Passerini, Stefano, Bruno Scrosati, Vincent Hermann, CarolAnn Holmblad e Terese Bartlett. "Laminated Electrochromic Windows Based on Nickel Oxide, Tungsten Oxide, and Gel Electrolytes". Journal of The Electrochemical Society 141, n. 4 (1 aprile 1994): 1025–28. http://dx.doi.org/10.1149/1.2054835.
Tesi sul tema "Tungsten oxide gel":
1
Isik, Dilek. "Sol-gel Derived Tungsten Oxide Based Electrochromic Coatings". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609686/index.pdf.
Abstract (sommario):
The microstructural, electrochemical and optical properties of sol-gel derived tungsten oxide electrochromic coatings have been investigated. Coatings were formed by spinning of tungsten metal based aqueous sol on glass with native ITO
layer. Three sol formulationsacetylated peroxotungstic acid (APTA), peroxotungstic acid (PTA) and titanium-doped peroxotungstic acid (Ti-PTA) were employed to obtain 200-300 nm thick multi-layered coatings. Material and electrochromic characterization of the coatings have been performed by DSC, XRD, SEM, cyclic voltammetry and UV-Vis spectroscopy. The electrochromic performance of the WO3 coatings was influenced by calcination temperature, by sol chemistry and by the adsorbed water content. For all sol formulations the coatings calcined at 250 °
C were amorphous and have shown better performance compared to crystalline counterparts calcined at 400 °
C. High calcination temperature also leads to formation of WO3 nanocrystals for APTA and PTA derived coatings, titanium doping retards crystallization. Presence of acetic acid as in APTA sol improved the electrochromic and electrochemical performance. This was related to removal of organics- acetic acid and peroxo ligands- during calcination, which results in an open W-O network providing more ion insertion sites. The water adsorption affected the electrochromic performance in different ways for the coatings calcined at 250 °
C and 400 º
C. The amorphous coatings with limited structural water removal and excessive hydroxyl groups tend to crystallize by condensation of W-OH groups upon storage in open atmosphere, therefore exhibiting degrading electrochromic activity with aging. Conversely, hydroxyl groups enhanced Li+ ion insertion for the stable crystalline coatings calcined at 400 °
C.
2
Taylor, Douglas John. "Structure and properties of laser-fired, sol-gel derived tungsten oxide films". Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187173.
Abstract (sommario):
This investigation focuses on the use of laser radiation to fire sol-gel derived oxide films. The main emphasis of this work was to make high quality tungsten oxide films with good electrochromic properties. Laser firing was done with a carbon dioxide laser operated in continuous mode. The laser-fired tungsten oxide films were measured for density, composition, crystallinity and electrochromic behavior. Analytical tools included multi-angle ellipsometry, FTIR, TEM, XRD, spectrophotometry and electrochemistry. The effect of process variables (laser power, spot size and translation speed) on the extent of film densification and microstructural evolution was investigated. Thermal modeling of laser-heated sol-gel films was studied to further understand the laser firing process and to estimate firing temperatures. Temperature calculations were based on laser parameters, sample geometry and target materials. Properties characteristic of firing temperature were used to verify the thermal modeling. For laser-fired films, the properties at the calculated temperatures agreed well with the properties of similar furnace-fired films. The modeling also provided the thermal profiles seen by the laser heated materials. Laser firing was shown to be a feasible technique to make good quality electrochromic films. By precisely controlling the irradiation, the microstructure of tungsten oxide films was tailored to produce the desired electrochromic properties. Transmission electron microscopy showed film microstructures that varied from completely amorphous to fully crystalline. Corresponding optoelectrochemical measurements indicated a decrease in electrochromism with increasing crystallinity. The effects of density/porosity and coating composition are also discussed. It is proposed that laser firing of sol-gel derived films can be used for optics, sensors, graded index materials, and electrochromic windows. The ability to heat localized regions afforded by laser firing is advantageous for writing lines and patterns in these films. Windows with graded electrochromic properties can be made by dynamically changing the laser firing conditions as the beam rasters through a workpiece. Similarly, electrochromic signs can be written into a window--after the pattern is written by laser densification, the remaining film is etched away, leaving the pattern.
3
Moura, Diego Soares de. "Obtenção de filmes de óxido de tungstênio tendo como agente estruturante o surfactante catiônico cloreto de dodeciltrimetilamônio". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/108370.
Abstract (sommario):
Neste trabalho foram obtidos filmes de óxido de tungstênio pelo método sol-gel modificado, tendo como precursor o tungstato de sódio dihidratado (Na2WO4.2H2O) e como agente estruturante o surfactante cloreto de dodeciltrimetilamônio (DTAC). O comportamento dos sistemas em meio aquoso foi avaliado por medidas de pH, condutividade e viscosidade. Foram avaliadas duas metodologias de obtenção dos filmes de óxido de tungstênio: a primeira consistiu na obtenção de filmes de tungstato de sódio, através de sistemas contendo 10 mmol.L-1 de Na2WO4.2H2O em diferentes concentrações de DTAC, por casting, e conversão do tungstato de sódio a óxido de tungstênio pela acidificação dos filmes; a segunda metodologia consistiu na conversão dos sistemas aquosos contendo 20 mmol.L-1 de Na2WO4.2H2O, em diferentes concentrações de DTAC, em ácido tungstico, obtenção dos filmes por spin coating e, calcinação em presença de ar. Os filmes foram obtidos em substratos de silício (100) recobertos com dióxido de silício e avaliados por Difração de Raios-X, Espectrometria de retroespalhamento Rutherford, Espectroscopia Raman, Microscopia Eletrônica de Varredura e ensaios fotocatalíticos. As alterações na concentração precursor e agente estruturante não afetaram significativamente o pH e a viscosidade dos sistemas precursores. A determinação da concentração micelar crítica (cmc) do DTAC, obtida através da condutividade, foi de 13 mmol.L-1 e 9,88 mmol.L-1 para os sistemas contendo 10 e 20 mmol.L-1 de Na2WO4.2H2O, respectivamente. Em ambas metodologias o produto final foi o óxido de tungstênio em forma de disco e placas. As espessuras dos filmes obtidos na primeira metodologia variaram de 4 a 5 μm e as estruturas tiveram diâmetros médios de 4,37 μm e 114 nm. Na segunda metodologia as espessuras foram de 0,5-1,0 μm e as estruturas obtidas tiveram diâmetros médios em torno de 95-103 nm. Os filmes obtidos apresentaram atividade fotocatalítica, uma vez que duplicaram a velocidade da reação de degradação do corante alaranjado de metila em relação ao sistema sem o filme.In this work tungsten oxide films have been obtained bymodified sol-gel method, with sodium tungstate dehydrate (Na2WO4.2H2O) as the precursor and the cationic surfactant dodecyltrimethylammonium chloride (DTAC) as structuring agent.The behavior in aqueous media of precursor/structuring agent systems was characterized by pH, conductivity and viscosity measurements. Two methods for obtaining tungsten oxide films were evaluated: the first consisted in obtaining sodium tungstate films from the systems containing 10 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations, by casting, converting the sodium tungstate to tungsten oxide; the second method consisted in the conversion of the aqueous systems containing 20 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations to tungstic acid, obtaining the films by spin coating and, posteriorly, calcination in the presence of air. The films were obtained on silicon substrate (100) with a 50 nm layer of silicon dioxide and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, Scanning Electron Microscopy and photocatalytic tests. The precursor concentration and structuring agent do not affect significantly the pH and the viscosity of the precursor systems in aqueous media.The values of critical micelle concentration (CMC) of DTAC, obtained by the conductivity, were of13 mmol.L-1 and 9,88 mmol.L-1, for the systems containing 10 and 20 mmol.L-1 de Na2WO4.2H2O, respectively.In both adopted methods the final product is the tungsten oxide, with nano and micrometric structures in the form of discs and plates. The thickness of the films obtained in the first method varied from 4 to 5 μm and the structures presented an average diameter around 4,37 μm and 114 nm. The thickness of the films obtained with the second methodvariedfrom0,5to 1 μm and the structures presented an average diameter from 95 to103 nm.The obtained tungsten oxide films presented photocatalytic activity, since doubled the reaction rate of methyl orange dye degradation with respect to the system without the film.
4
Yin, Zhewen. "Non-precious Metal Catalysts for Oxygen Reduction Reaction in Alkaline Solutions". Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7250.
Abstract (sommario):
Mesoporous WO3 powders were prepared via sol-gel processing synthesis using nonionic surfactant Pluronic (P-123) as the template. The influences of heating temperature on the pore structure and properties of WO3 powders were investigated. Three kinds of modifications were compared and evaluated after finding out the best heating condition. Different amount of lanthanum was doped into mesoporous WO3 to improve its Oxygen Reduction Reaction (ORR) activity. Several factors contributing to the increase of catalytic performance were discussed. Vulcan carbon powder was also used as a support to increase the catalysts’ electrical conductivity as well as dispersity. The component, microstructure and specific surface area of samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and N2 adsorption-desorption analysis. A three-electrode system with a rotating disk electrode (RDE) was used to detect samples’ electrochemical performance towards ORR in alkaline solutions. The as-prepared mesoporous La/WO3 powder with a ratio of La: W = 1: 10, calcined at 550℃ and supported by 25 wt% Vulcan carbon powder, exhibited highest ORR catalytic activity.
5
Sidhoum, Charles. "In-situ study of hybrid nanomaterial formation : a multiscale approach combining electron microscopy and spectroscopic techniques". Electronic Thesis or Diss., Strasbourg, 2023. http://www.theses.fr/2023STRAE041.
Abstract (sommario):
Cette thèse explore la nucléation et la croissance de deux systèmes chimiques distincts en utilisant la microscopie électronique à transmission (MET) in-situ comme outil principal. Le premier système implique la croissance de pérovskites hybrides, synthétisées par une méthode de précipitation utilisant deux solvants de polarités différentes. Le second système étudie la croissance de gel d'oxyde de tungstène, obtenu par voie sol-gel. Ces approches par « Chimie-Douce » conduisent souvent à des phases cinétiques métastables, ou intermédiaire. L'objectif principal de cette thèse est d'exploiter les techniques in situ pour suivre ces processus en temps réel, fournissant des informations sur l’évolution structurale et chimiques de ces systèmes. Les données MET in-situ sont corrélées à d'autres techniques, telles que la diffraction des rayons X, la diffusion des rayons X aux petits angles, la résonance magnétique nucléaire, etc. Cette approche combinée vise à combler un manque concernant les études dynamiques in-situ à l'échelle du nanomètre, en se concentrant sur les études corrélatives afin d'obtenir une vue d'ensemble des mécanismes de formationThis thesis explores the nucleation and growth of two distinct chemical systems using in-situ Transmission Electron Microscopy (TEM) as a main tool. The first system involves hybrid perovskites, synthesized through a precipitation method using two solvents with different polarities. The second system investigates the growth of a more covalent structure, the tungsten oxide gel, using a sol-gel approach. These “Chimie-Douce” approaches often leads to metastable kinetic phases that slowly transition to a more stable thermodynamic phase. The primary goal of this thesis is to leverage in-situ techniques to monitor these processes in real-time, providing insights into the kinetics and chemical transformations.The in-situ TEM data are complemented by other techniques, such as X-ray diffraction, Small Angle X-ray Scattering, Nuclear Magnetic Resonance, and others. This combined approach seeks to fill a gap in the dynamic in-situ studies at the nanometer scale, focusing on correlative studies to obtain a comprehensive view of the formation mechanisms
6
Michalak, Franck. "Étude d'électrodes composites polymères/oxydes colloidaux : application aux systèmes électrochromes sur supports souples". Grenoble INPG, 1995. http://www.theses.fr/1995INPG0091.
Abstract (sommario):
Au cours de ce travail, nous avons etudie des electrodes composites polymeres/oxydes colloidaux en vue d'application aux systemes electrochromes sur supports souples. Ces composites sont constitues d'un materiau electrochrome colloidal (wo#3, iro#2) et d'un polymere ionique (nafion) ou neutre (polyacrylamide, polymethylmetacrylate, polyvinylbutyral). Nous avons etudie la synthese de ces oxydes dans le but d'obtenir un materiau colloidal stable de taille inferieure a 100 nm. Nous avons obtenu des sols de wo#3 stables contenant des particules ayant un diametre moyen de 10 nm. Les composites wo#3 - polymere contiennent jusqu'a 90% en poids de wo#3 et restent transparents. Ils constituent l'electrode electrochrome de nos systemes. Les particules d'iro#2 obtenues sont trop grosses pour les applications visees (100nm). Nous avons alors utilise la polyaniline comme materiau de contre electrode. La polyaniline a ete deposee sous forme d'un film mince par polymerisation galvanostatique sur un substrat en polyethylene terephtalate recouvert d'une fine couche d'or. Le systeme electrochrome complet comprenant l'electrode composite wo#3/polymethylmetacrylate, la contre electrode en polyaniline et l'electrolyte polymere (bpei-1. 5 h#3po#4) a un contraste de 35% a 700 nm
7
Chen, Rei-Lin, e 陳瑞琳. "Preparing Electrochromic material Tungsten Oxide by Sol-Gel method". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/64645832319371835409.
Abstract (sommario):
碩士逢甲大學
化學工程學所
92
Electrochromism is currently attracting more attentions from the academia and industries. There are many commercial applications for the electrochromic devices, such as sunroof window in a car, smart windows in order to balance the lighting in a house, antiglare mirror and electrochromic displays. Electrochromic materials include two types that are inorganic and organic ones. Especially for the inorganic type it can tolerate the dramatic environmentally changes, the typical materials are ITO, WO3 and NiOx, etc. The WO3 is the most investigated inorganic material, cause of its high transmittance difference. In this study sol-gel method is main concerned for the preparations of the tungsten oxide. The method has some advantages, which are low cost, easy to scale up to the large surface area and even the different aspect. At first, the solutions of sol-gel were prepared by using different precursor and catalyst (precursor : WOCl4 , WCl6), and spin-coating process used to deposit tungsten oxide film on the ITO glass, then conducted with the IR heat treatment. The deposited films were characterized by X-ray diffraction, scanning electronic microscopy and α-step film thickness. Several tungsten precursors were investigated in this study. The acid and base sol-gel solutions are also tested to observe the coloration of electrochromical films. From the CV/UV-VIS spectra we found that the sol-gal method is promising and WCl6 precursor is the better one.
8
Li, Ming Cong, e 李明聰. "Synthesis of Mesoporous Tungsten Oxide by Sol-gel Method". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/33204086395658895278.
Abstract (sommario):
碩士國立屏東科技大學
機械工程系所
95
Nanomaterials have unique properties in comparison with powder materials. Mesostructured materials with tailored pore structures and high surface areas in order to improve sensitivity have gathered increasing attention in recent years. In this study, mesoporous WO3 was prepared by sol-gel process and the synthesis was accomplished by using block copolymer as the template, and tungsten chloride as the inorganic precursor. We investigated the effects of synthesis variables on the structure of mesoporous WO3, such as the concentration of triblock copolymer, hydrolysis reaction, and the calcination temperatures. Thermo-gravimetric analysis, X-ray diffraction, transmission electron microscopy and N2 adsorption-desorption isotherms were used to characterize the microstructure of the samples. Mesoporous WO3 have been synthesized by using triblock copolymer F108 as a template and monoclinic structure were obtained after calcined at 300~400°C. The mesoporous WO3 is shown to have a high specific surface area of 129.5 m2/g as calcined at 300°C, and mesoporous structure was stable up to 350 °C. The addition of block copolymer can affect the structure of mesoporous. The addition of block copolymer increased from 0.1 to 1.0 g, and the specific surface area increased from 67.5 to 124.7 m2/g after calcined at 300°C. The microstructure of mesoporous WO3 is determined by the calcination temperature. From 300 to 400 ℃, the grain size increased from 6 to 12 nm, it can be seen that by increasing the calcined temperature a larger crystallite size is favored. Additionally, the crystallinity of mesoporous WO3 is controlled by the water content of the reaction system. From XRD results, the mesoporous WO3 with the better crystallinity are obtained with the increasing of the water content. Replaced with water from 0 to 50 %, the BET surface area decreased from 124.7 to 48.12 m2/g, but the average pore size increased from 7.79 to 14.098 nm after calcined at 300 ℃.
9
Lin, Hung-Bin, e 林弘斌. "Gas Sensing Properties of Tungsten Oxide / Titanium Oxide Films Prepared by Sol-gel Technique". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96733043277716671619.
Abstract (sommario):
碩士逢甲大學
材料科學所
96
Abstract In this study, tungsten oxide/titanium oxide (5, 7.5, 10, 15, and 20%, respectively) composite powders were prepared by sol-gel technique. The as-prepared powders were examined by X-ray diffraction, scanning electron microscope, Fourier-transform infrared spectroscopy, and UV-visible spectroscopy. The composite powders were then deposited onto the alumina substrate and gas sensing properties were investigatd. Experimental results showed that the structure of the tungsten oxide/titanium oxide (10% addition) powders exhibited monoclinic WO3 phase at low temperature and gradually transformed into triclinic WO3 phase after heating at 300 oC. The sensors prepared by tungsten oxide/titanium oxide (10% addition) powders also exhibited the best gas sensing performance. Under an environment of 3 ppm NO2 gas, the sensitivity was 29.9 and 86.1 when tested at 200 and 150 oC, respectively. In addition, the sensitivity was 79.4 (only 8% degradation) after 20 repetitive gas adsorption-and-desorption cycles when tested under 3 ppm NO2 at at 150 oC. Meanwhile, when tested by reductive CO gas, a decrease in resistance can be observed and showed an opposite variation with respect to NO2 gas.
10
Chao, Ching-Wen, e 趙靜雯. "Preparation of Gasochromism Tungsten Oxide Thin Film by Sol-gel Method". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/37435056437432111691.
Abstract (sommario):
碩士逢甲大學
材料與製造工程所
95
Gasochromism, a technology similar to electrochromism, is able to change color without external electric source. The principle is that the gasochromic layer is colored by accepting electrons from hydrogen. Therefore, the gasochromism technology has broad applications such as smart windows as well as hydrogen sensor. In this study, the material of gasochromism was prepared by sol-gel process, which has the advantages of low cost, friendly operation, and easy to scale up to the large surface area. The gasochromic material of WO3 could be created by the steps hereinafter. Firstly, WO3 was prepared by sol-gel process and then deposited on the ITO glass by spin-coating. Secondly, thermal treatment was provided. Finally, catalytic layer was formed by electroless plating process. We used nitric acid as catalyst, hydrogen peroxide as oxidizer, and isopropyl alcohol as solvent to analyze the influence of their concentrations to the ability of color changing and the surface structure of WO3 film to acquire the best process condition. Next, the deposited films were characterized by scanning electronic microscopy (SEM) and SEM / EDS, surface mapping microscope and X-ray diffraction. Further, UV-VIS spectrometer was employed to detect the transmission rate of light for both colored and bleached WO3 films. Finally, FTIR was employed to verify the spectrum of WO3 film. From the experimental results, we concluded that during the preparation of the material of gasochromism by sol-gel process, adding little quality HNO3 and H2O2 aqueous could reduce the time of hydrolysis, accelerate reaction. So we acquire the amorphous structure nano WO3 film with high coloring ability (DT550nm =37.58%), good surface quality (Ra <10nm), and uniform grain size (23~28nm).
Atti di convegni sul tema "Tungsten oxide gel":
1
Ozkan, Esra, Se-Hee Lee, Ping Liu, C. Ed Tracy, Fatma Z. Tepehan, J. Roland Pitts e Satyen K. Deb. "Optical and electrochromic properties of sol-gel-deposited tungsten oxide films". In International Symposium on Optical Science and Technology, a cura di Carl M. Lampert, Claes-Goran Granqvist e Keith L. Lewis. SPIE, 2001. http://dx.doi.org/10.1117/12.448247.
2
Lee, W. J., Y. K. Fang, Daoyang Huang e Fang C. Ho. "Sputter-Deposited Electrochromic Films of Tungsten Oxide: A Study of the Effects of Varying the Target-Substrate Distance". In Optical Interference Coatings. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/oic.1998.thc.3.
Abstract (sommario):
Electrochromic properties of transition metal oxides have been extensively studied in recent years due to their potential application as " smart " optical-switching window materials.1,2,3,4 In particular, tungsten oxide outperforms most of other transition metal oxide films and thus draws most attention from researchers.5 Tungsten oxide film can be prepared by many methods, including electron-beam evaporation, thermal vacuum evaporation,2 chemical vapor deposition, sol-gel deposition, and sputter deposition. Among these methods reactive sputtering is most suitable for large area applications such as automobile glass and architecture building glass.
3
Green, David C., John M. Bell e Geoffrey B. Smith. "Microstructure and stoichiometry effects in electrochromic sol-gel deposited tungsten oxide films". In Optical Materials Technology for Energy Efficiency and Solar Energy, a cura di Anne Hugot-Le Goff, Claes-Goeran Granqvist e Carl M. Lampert. SPIE, 1992. http://dx.doi.org/10.1117/12.130545.
4
Cremonesi, Alessandro, Danilo Bersani, Pier Paolo Lottici, Gianluca Calestani, P. M. Champion e L. D. Ziegler. "Raman And SEM Characterization Of Sol-Gel Derived Nanofibers Of Tungsten Oxide". In XXII INTERNATIONAL CONFERENCE ON RAMAN SPECTROSCOPY. AIP, 2010. http://dx.doi.org/10.1063/1.3482695.
5
Djaoued, Yahia, P. V. Ashrit, S. Badilescu e R. Bruning. "Microstructure, optical, and electrochromic properties of sol-gel nanoporous tungsten oxide films". In SPIE Proceedings, a cura di Janis Spigulis, Janis Teteris, Maris Ozolinsh e Andrejs Lusis. SPIE, 2003. http://dx.doi.org/10.1117/12.517023.
6
Hou, Changjun, Jiale Dong, Yan Xu, Danqun Huo, Yike Tang e Jun Yang. "Preparation and Characterization of Pt/WO3 Nano-Film and Its Hydrogen-Sensing Properties". In 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70010.
Abstract (sommario):
Tungsten trioxide is an n-type semiconductor, which has been extensively used for the development of metal oxide semiconductor gas sensors. The hydrogen gas sensing performance of platinum (Pt) catalyst activated WO3 thin films were investigated here. All of the Pt/WO3 films membranes are sensitive to hydrogen gas and the sample by sol-gel and DC reactive magnetron sputtering methods. X-ray diffraction results indicate that the tungsten trioxide is cubic crystal, and the AFM analysis shows molecular structures of the samples are tetrahedron. It means the four consecutive quadrilateral forms we observed in the 9nmx9nm molecular structure are scattergram of tungsten-ions and oxide-ions on 106 sides in WO2.9 structure cell, and the lost one oxide-ion resulted in the transition of WO3 to WO2.9. With anneal temperature rising, the membranous poriness decreasing. The higher crystal degree is, the lower gasochromic efficiency is. The change of combining environment and content of O−2 ions in colorized / decolorized state WOx films was observed in XPS analysis of Pt/WO3 film, the peak shape had changed greatly. As a result, the explanation to this phenomenon is available here according to XPS chemical shift of electric potential model theory.
Rapporti di organizzazioni sul tema "Tungsten oxide gel":
1
Cervantes, O. Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites. Office of Scientific and Technical Information (OSTI), giugno 2010. http://dx.doi.org/10.2172/1129990.