Tesi sul tema "Tungsten oxide gel"

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 formulations
acetylated 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.

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.

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.

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.

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 formation
This 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

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

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.

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 ℃.

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.

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).

碩士
逢甲大學
化學工程學所
94
Gasochromism is a novel technique that was developed from electrochromism. Electrochromic films were coloured when a potential applied, while gasochromic films applied by an appropriate gas. The state-of-the-art of gasochromic films applications are smart window and gas sensor. No matter in electrochromism or gasochromism, the tungsten oxide of inorganic materials attracted considerable attention, cause of the tungsten oxide has a good coloring efficiency. In this study, the combined process of sol-gel and electroless method was carried out to make the gasochromic film. For the detailed process, WO3 films prepared firstly by the sol-gel and then deposited by spin-coating on ITO glass. The WO3 film was overlaid by a thin layer of Pd, which worked out by an electroless method with thermal treatment. From the SEM photos the WO3 films had little destruction after the electroless procedure. The WO3 films characterized by XRD revealed amorphous structure. FTIR spectroscopy revealed the shift of both bounding, terminal ν (W=O) and bridge ν (W-O-W), by coloration. UV spectroscopy showed the infrared region had bigger transmittance difference than the visible one. From the experimental results, we found that the combined process has a good surface quality, low cost and easy to use for commercial applications.

碩士
國立臺南大學
材料科學系碩士班
105
With the increasing concern on environmental protection issues, many researchers devoted to the study of energy saving., including the development of electrochromic devices. Many materials can be used in the electrochromic devices, and many studies have been focused on the morphology and electrochemical characteristics of the electrochromic material. Since the electrochromic devices are composed of multiple layers, the function of the electrolyte also affects the performance of electrochromic devices. In this study we will focus on the effect of gel electrolyte layer on the properties of the electrochromic devices. In the study, we used the radio frequency sputtering with appropriate reaction parameters to prepare the tungsten oxide thin films on the FTO substrate. We also use the hydrothermal method to fabricate the W18O49 nanowire arrays on the FTO substrate in order to understand the dimension of tungsten oxide on the device performance. Then non-aqueous gel electrolytes with different compositions were sandwiched in-between the FTO glasses. Finally, the electrochromic performance in dynamic mode was evaluated with CHI DC power supply and UV-vis spectrometer. The results and discussion in this thesis can be into two parts. The first part is to study the morphology and electrical characteristics of electrochromic materials (tungsten oxide films and W18O49 nanowires) on the electrochromic performance of the devices. The second part is to discuss the effect of ion species and their concentration in the electrolyte on the electrochromic performance of the device. The ion types included the lithium ion and the aluminum ion. In addition, different concentrations of ferrocene were added in the system of lithium ion electrolyte in order to investigate their special electrochromic characteristics. We observed that the device has a maximum contrast (~50%) at 0.75M Li ion concentration in the assembled system and the device has a maximum contrast (~59%) at 0.25M Al ion concentration in the assembled system, respectively. The optical contrast and reaction response time of the devices using aluminum ion electrolyte are better than the system based on lithium ion electrolyte. Finally, a slight amount of ferrocene was added in the lithium ion electrolyte system, and the device has a good electrochromic performance even at low applied voltages.

碩士
逢甲大學
材料科學所
98
In this study, tungsten oxide films were prepared by sol-gel technique. Tungsten oxide and tungsten oxide/MWCNTs films were prepared with different concentrations (1.0, 2.0, 2.5, 3.0, 3.5, 4.0M) and thickness (100nm, 200nm, 300nm, 500nm) of H2O2 and different ratios of MWCNTs (0.01, 0.05, 0.1, 0.2, 0.3, 0.5wt %) by spin-coating. Then the films were examined with the basic feature and structure by thermogravimetric analysis, X-ray diffraction analysis, X-ray photoelectron spectroscopy and scanning electron microscopy analysis. In addition, the films were electrochemical analysis used potentiostat and optical properties analysis used UV - visible spectra. The results showed that tungsten oxide films adopted different proportion of H2O2 and MWCNTs are amorphous structures. The films with parameter controls (the concentration and thickness of H2O2 and the addition amount of MWCNTs) which exhibited the best electric current of colored and bleached states (-29.40mA and 50.19mA), the shortest response time of colored and bleached states (8 seconds and 1 second), the best penetration variation (69.0%) and optical density (0.83), and coloration efficiency (29.9cm2/C) in electrochemical and optical properties when adopted 3M H2O2, 0.1wt% MWCNTs and thickness of 300nm. Furthermore, after 200 cycle tests of colored and bleached states, the variation of penetration was reduced from the maximum 69% to 55.6% gradually.

碩士
義守大學
生物技術與化學工程研究所碩士班
94
NO is easy to combine with hemoglobin of blood and become nitro-hemoglobin. When exposed in high NO concentration environment for a long period of time, our central nerve will be inhibited, so the objective of this work is to invent nanocrystalline tin-tungsten oxide thin film to detect the NO concentration in atmosphere. Also, an increasing of NO concentration exhaled from human can be an indication of important symptom of pneumonia or asthma. Expensive, long detecting time and heavy sensors are no longer used in recent years. Instead of thick film and thin film sensor technologies, nanocrystalline thin film gas sensors are widely considered in these few year because of its fast detect, small size and low energy consumption. In this research, SnCl4 and WCl6 were utilized as precursor to synthesis SnO2 and WO3 sol for sensing materials of gas sensor by sol-gel method. Tin oxide was used as the based material because of its high mechanism properties, stable in high temperature and bad environment. Doped WO3 ,which has high sensitivity to NOx, and doped CuO ,which can enhance ability of oxidization, were both utilized to compare the relationship between these few condition. Electrophoresis method was adopted to make sensing films with the help of liquid crystal template method and adjusted surface potential of sol solution to pH=10. After calcination one hour at several different temperatures, a high surface area nanocrystalline tin-tungsten oxide thin film with interdigitate electrode by electrophroesis was produced. XRD, SEM and ESCA were utilized to define the different parameters of its crystal and chemical structure, its surface morphology and component. It is observed that both tin oxide and tungsten oxide have sensing ability to nitric oxide but didn’t have any selectivity to distinguish between NO and NO2 ；By adding a hint of copper sulphate, the selectivity of sensor was enhanced, when molar concentration of mixed solution is Sn : W : Cu = 1 : 1 : 0.0125%, NO sensor can detect NO from 0.1 ~ 25 ppm at operating temperature 200 ℃, at the same operating temperature, however it didn’t work when it contacted to NO2. Consequently, a highly selective nanocrytalline copper doped NO sensor was developed in this study.

碩士
國立臺灣科技大學
光電工程研究所
99
In this thesis, the effects of different annealed temperatures and gases environments on the performance of W18O49-based metal-semiconductor- metal (MSM) photodetectors (PDs) were thoroughly studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmittance, and photoluminescence (PL) spectra revealed that the sol-gel prepared W18O49 film became more porous and more crystallization as annealed temperature ncreased. The PD of W18O49 film annealed at 600oC (PD_600) possessed the better performance with photo-to-dark current contrast ratio and rejection ratio of 6.5×102 and 407.8, respectively. PD_600 was further studied versus different gases environments, pure O2, air, vacuum, O2-Air-O2 (OAO), and O2-Vacuum- O2 (OVO). Ultraviolet (UV) light was used as the source for measuring the photocurrent. It was observed that in O2 gases environment, the adsorption of O2 molecules may capture electrons in the bulk W18O49 film surface and reduced both of the dark and photocurrent. Similar phenomenon was observed in other conditions. The maximum photo-response of PD_600 measured in air, vacuum, OAO, and OVO were 45.7, 75.2, 28.0, and 82.9 respectively. Finally, PDs with different annealed temperature treatment were inspected in various gases environments. In air environment, PD with W18O49 annealed at 600oC performed the highest photocurrent properties. The photo-responses among the different environmental tests suggested that the W18O49-based PD with 600oC-annealed film was promising for the application on light sensing.

碩士
國立臺灣師範大學
機電科技研究所
99
This study combines sol-gel method and screen-printing technology to fabricate tungsten oxide film which applied to electrochromic element.My study can be divided into three parts.First is fabricating APTA powder and then measure its properties.The APTA powder has exothermic peak at 430℃ by DSC analysis.We learned that exothermic peak is caused crystallization behaviors from WO3 film by XRD analysis.WO3 film is amorphous phase when temperature is lower than 250℃,then turns into monoclinc phase at 450℃. Secondly, a sol–gel derived APTA solution encompassing 0wt.% and 4 wt.% of oxalic acid dihydrate (OAD) has been employed for the deposition of tungsten oxide films by spin-coating technology. The transmittance modulation is 39% for films annealed at 100 ℃ and decreases to 36% and 10% for 250℃ and 450℃ annealing temperature for WO3 film with 0 wt.% OAD.Grain will aggregate with higher annealing temperature,and leads to dreasing of electrochromic properties. By adding 4wt.% OAD can efficiently keep grain from aggregate.Their transmittance modulation are 53%、34% and 32% for 100℃、250℃ and 450℃annealing temperature. The past prepared using Powder :EtOH formulations of 3:7、4:6 and 5:5,then adding 4wt.% ethyl cellulose and OAD. Their transmittance modulation are 53%、34% and 32% .The paste with a 4:6 ratio showed better electrochromic properties.

博士
國立成功大學
材料科學及工程學系
102
Electrochromic device have the ability to change the transmittance to block the solar radiation by controlling the applied voltage and have the application for energy-saving windows. State-of-the art, the challenges of the device are nanostructured electrodes and large-scale fabricating. In this research, porous tungsten oxide is synthesized by the surfactant-assisted sol-gel method. Porous structure, crystallinity, and composition can be modified by the concentration of surfactant, annealing temperature, and curing condition. The effects of different morphology and structure are studied by chronoampermetry and cyclic voltammetry. Transmittance modulation and coloration efficiencies are 67.6 % and ~60 cm2C-1. It needs less than 10 s to switch from colored state to beach state. All solid electrochromic devices are fabricated by all-solution method. Thermal shielding ability is measured by UV-Vis-IR spectroscopy and illuminating meter. Visible light transmittances and solar heat transmittances are 55.2/35.9 % and 38.2/20.1 % in colored/bleach state respectively. The transmitted illumination can be modulated from 36 % to 16 %. The transmittance in visible light region is higher than 50 % and the ability of blocking infrared is enough to use as energy-saving smart window.

碩士
逢甲大學
纖維與複合材料學系
106
In this study, tungsten oxide nanoparticles with different oxygen ratios and crystallinity were synthesized by using sol-gel method and calcination. The microstructure of nanoparticles were investigated to reveal the influences of oxidant and calcination on the microstructure and radiation absorption properties of obtained tungsten oxide. These various tungsten oxide nanoparticles were composited into a polyurethane matrix as a function additives to produce the thermal radiation shielding WO3-x / DPU films. First, tungsten oxide nanoparticles with different oxygen ratios were synthesized by adjusting the amount of oxidant for sol-gel process. Half of synthesized nanoparticles were calcined. The XRD and TEM analysis shows that increasing the concentration of oxidants enhances the crystallinity of nanoparticles. The XPS analysis results shows that the oxygen ratio affects the fractions of W6+, W5+, and W4+ configurations in tungsten oxide powder and causes the apparent color difference. The increase of oxidant concentration gradually shifts the particle color from dark blue to yellowish green. The average particle size of D95 of WO3-x (3M) was 269.93 nm. In the second part, tungsten oxide powders were composed into polyurethane. The composite films were sliding formed. The FTIR spectra evident the powder and matrix are physically mixed. The apparent color of composite films also reflects the powder colors. Through the UV-Vis-NIR transmittance spectra, it was found that the tungsten oxide contained composite film show excellent near-infrared shielding ratio. The sample of CWO3-x(0.5M)/DPU-5wt%, exhibits a maximum shielding ratio 95.06% for 940 nm wavelength. It also perform a maximum temperature rise 33 ̊C under the halogen lamp illumination, and a maximum temperature rise 59.1 ̊C under the near-infrared lamp illumination. The measured thermal conductivity coefficient per unit thickness value was found to be 162.0 mWm-1K-1, the thermal diffusion value was 0.105 mm2/s, the thermal absorption value was 1530.6 Ws1/2/m2K, and the thermal resistance value was 26.6 m2mK/W. The tungsten oxide composite film prepared in this study exhibits a photothermalysis and visible-near-IR shielding properties. These reveals its potential to be applied to solar receivers to improve their reception efficiency and used as an infrared ray absorbing material, heat-insulating affixing material, glass affixing material for automobiles or buildings, military, indoor, industrial, transportation, and other functional textiles or related products.