Dissertations / Theses on the topic 'WO3-x'

The influence of changes in the conditions of sol-gel method on the thermal characteristics and the structure electrochromic (EC) а-WO3 films. DSC data showed greater sensitivity of the structure to the pe-culiarities of the drying of the product poliperoxo-tungstic acid. The Films were transparent over a wide range (Eg  2,5 eV). All compositions were amorphous as measured by X-rays diffraction. Based on the IR and Raman spectroscopy dates was concluded the presence in the structure of amorphous transparent glassy semiconductor a-WO3 predominantly tetrahedral [WO4] groups. The precursor product and EC-films are glass material, obtained by the sol-gel process, with the composition WO3*  H2O. Synthesis peculiari-ties of mesoporous a-WO3. affects both the pore structure, which determines the concentration of the aqueous components and the ratio of the bridging W-O-W and unbridged W  O bonds, defining characte-ristics of the electrochromic materials. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35386

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
InO1.5-stabilized zirconia (InSZ) is a potential hot corrosion resistant thermal barrier coating (TBC). However, the thermal instability prevents real applications of InSZ-based TBC. This thesis investigates the hypothesis of co-doping using the charge compensation to improve the phase stability of InSZ. Four co-doping systems were synthesized by coprecipitation and studied: (ZrO2)1-(x+y)(InO1.5)x(MOz)y with MOz = TaO2.5, NbO2.5, MoO3, or WO3. After synthesis, 9 mol% of InO1.5 plus the charge-compensating oxides was sufficient to stabilize the tetragonal phase. Specific surface area up to 106.1 m2.g-1 and crystallite size ~11 nm were achieved using ethanol washing followed by azeotropic distillation as dehydration technique in the precipitates. In these powders, initial thermal stability analysis indicated instability of the tetragonal phase, with extension of the t→m transformation less detrimental in the InMoSZ system. Further increase in the concentration of InO1.5:MoO3 results in monophasic samples with retention of cubic phase in the InMoSZ. Cubic InMoSZ exhibited hardness and thermal expansion coefficient of 13.5% and 9% higher than those of InSZ, respectively. However, thermal treatments at T ≥ 1200 °C showed that the InMoSZ is also passive to destabilization of the high temperature cubic polymorph. Although the cubic InMoSZ was the most promising system found in this thesis, the stability results do not support its application as TBC for temperatures ≥ 1000 ºC. A deep evaluation of the phase transformations between 1000 to 1200 °C indicated that the instability of the proposed systems is due to a progressive c→t→m destabilization of the polymorphs. This c→t→m transformation is directly associated with the reduction of the InO1.5 stabilizer in solid solution by volatilization as In2O during heat treatment. At temperatures ≤ 800 ºC, the c→t phase transformation do not occurs, then, InSZ-based TBC is stable in these conditions.
A zircônia estabilizada com InO1,5 (InSZ) é um material com potencial aplicação como revestimentos para barreira térmica (TBC) resistentes à corrosão. Contudo, a instabilidade de fases impede aplicações industriais da InSZ. Esta tese investiga a ação da co-dopagem por compensação de cargas como uma estratégia para aumentar a estabilidade de fases da InSZ. Quatro sistemas de co-dopagem foram sintetizados por co-precipitação e estudados: (ZrO2)1-(x+y)(InO1,5)x(MOz)y com MOz = TaO2,5, NbO2,5, MoO3 ou WO3. Após a síntese, 9 %mol de InO1,5 somado a concentração de óxidos compensadores de carga foi suficiente para estabilização da fase tetragonal. Área superficial específica de até 106,1 m2.g‒1 e tamanho de cristalitos de ~11 nm foram obtidos utilizando a lavagem com etanol seguida por destilação azeotrópica como técnica de desidratação dos precipitados. Para estes pós, testes de estabilidade térmica indicaram instabilidade da fase tetragonal, com extensão de transformação t→m menos detrimental no sistema InMoSZ. Aumentando gradativamente a concentração de InO1,5-MoO3 na InMoSZ resulta em amostras monofásicas com retenção da fase cúbica. A InMoSZ cúbica exibiu dureza e coeficiente de expansão térmica até 13,5% e 9% superiores aos valores da InSZ, respectivamente. No entanto, tratamentos em temperaturas ≥ 1200 ºC indicaram que a InMoSZ é também suscetível a desestabilização da fase cúbica. Embora a InMoSZ cúbica tenha sido o sistema mais promissor obtido nesta tese, os resultados de estabilidade indicam que sua aplicação como TBC não é possível em temperaturas ≥ 1000 ºC. Uma avaliação detalhada das fases formadas após os tratamentos entre 1000 a 1200 ºC demonstrou que a instabilidade dos sistemas estudados é decorrente de uma transformação progressiva tipo c→t→m. A origem da transformação c→t→m é associada a redução da concentração do estabilizador InO1,5 em solução sólida por volatilização como In2O durante os testes de estabilidade térmica. Em temperaturas ≤ 800 ºC, a transformação c→m não ocorre, neste caso, TBCs baseadas em InSZ são estáveis termicamente para aplicações industriais.

Une appréhension avec les outils cristallographiques permet de mettre en évidence les relations structures-propriétés si nécessaires à la compréhension des propriétés de conduction des matériaux. C’est avec ce double objectif que mes travaux de thèse ont été menés : investigations structurales et études des propriétés de conduction ionique des composés définis de structure inconnue au sein du diagramme de phase La2O3-WO3. Les structures et les microstructures de ces composés, obtenus principalement par voie de synthèse solidesolide, ont été étudiés par diffraction des rayons X, des neutrons et des électrons (Microscopie Electronique en Transmission et à Balayage) sur poudre, par analyse thermique différentielle et gravimétrique, ainsi que par résonance magnétique nucléaire du 139La. Les propriétés de conduction ionique ont été caractérisées par spectroscopie d’impédance. Le composé ß-La2WO6 (1:1), forme basse température a vu sa structure résolue de manière ab-initio. Il s’agissait du dernier membre des composés Ln2WO6 (Ln = lanthanide + Yttrium) de structure inconnue, celui-ci ne présente aucune parenté cristallographique avec les composés de même formulation. Malgré des tests d’hyper-trempe, la variété haute température n’a pu être complètement isolée. Suite à la résolution structurale ab-initio du composé La14W8O45 (53,3%mol. WO3), nous avons dû reformuler ce composé vers La18W10O57 (52,6%mol. WO3). Ce composé cristallise dans une maille hexagonale de grand volume, avec un paramètre c six fois multiple du paramètre de la maille fluorine. Les trois variétés allotropiques du composé La6W2O15 (3:2) ont été étudiées. Lors de ce travail, nous avons mis en évidence une relation de parenté structurale entre ces trois formes. Les structures des formes haute température (a > 930°C) et moyenne température (630°C < ß < 930°C) sont résolues. Lors de cette étude, nous avons mis en évidence un nouveau composé défini qui se situe à 42%mol. WO3. Ce nouveau composé présente une structure modulée (1D) très proche de la forme haute température de la phase La6W2O15. On constate l’insertion d’un oxygène supplémentaire. Enfin, le composé La10W2O21 (5:2) a également été l’objet d’une longue étude car celui-ci présente une propriété de conduction par ions O2- intéressante, à 700°C, une conductivité de l’ordre de 6×10-4 S. Cm-1 a été mise en évidence. La résolution structurale a mis en évidence une structure lacunaire à la fois dans le sousréseau anionique et dans le sous-réseau cationique
The aim of this work deals with the structural exploration of the La2O3-WO3 phase diagram. Indeed, like many phase diagrams, La2O3-WO3 was built in the 70s, but definite compounds structures were not determined and are still unknown. This thesis focus on La2WO6, La18W10O57, La6W2O15 and La10W2O21. These compounds are synthesized as powder by solid state reaction and characterized by X-ray, neutron powder diffraction, gravimetric and differential thermal analysis, T. E. M. And 139La N. M. R. . The structure of the low temperature form named ß-La2WO6 has been determined from laboratory X-ray diffractometer, neutron (T. O. F) and electronic diffraction data. This tungstate crystallizes in a non-centrosymetric orthorhombic space group (n°19) P212121 Z = 8, a = 7,5196(1) Å, b = 10,3476(1) Å, c = 12,7944(2) Å. La18W10O57 which presents 52. 65 WO3 mol% in the binary system La2O3-WO3 in place of the previous reported compound: La14W8O45 53. 3 WO3 mol%. The structure has been determined from synchrotron and laboratory X-ray, neutron, and electron diffraction data. This tungstate crystallizes in the non-centrosymmetric hexagonal space group (n°190) P-62c , with Z = 2, a = 9. 0448(1)Å, c= 32. 6846(3)Å. This compound presents a sub cell c’=c/6= 5. 45Å. Polytypism have been observed concerning this compound by transmission electronic microscopy, ionic conductivity and thermal expansion have been explored. For the 3 allotropic La6W2O15 forms, a structural relation have been established. The a and ß form are solved. The crystal structure of La10W2O21, which has to be reformulated (La5. 667W0. 333)LaWO14??2, is best described, on average, by a 2 x 2 x 2 anion-deficient fluorite-related superstructure cubic cell, space group F 4 3m, Z = 4, a = 11. 17932(6) Å. The La/W mixed site is nicely confirmed by 139La NMR. This compound exibits an interesting fast oxide-ion conducting properties, comparable with LAMOX at low temperature. Different from many ionics conductors, we don’t notice any temperature structural transition. Its conductivity is about 6. 4×10-4 S. Cm-1 at 700°C

Dans cette étude, la synthèse en milieu polyol est utilisée afin d’obtenir des oxydes de tungstène nanostructurés et présentant une légère sous-stœchiométrie en oxygène (WO3 x). Les particules obtenues sont de couleur bleue, et possèdent des propriétés optiques intéressantes du fait de la présence d’ions W5+. Les traitements thermiques de ces particules à différentes températures ou sous différentes atmosphères permettent de contrôler la sous-stœchiométrie en oxygène et donc leurs propriétés optiques (et leur couleur) ; leur teinte allant du jaune pâle pour les composés recuits sous une atmosphère oxydante et ne possédant plus que des ions W6+, au noir pour des particules recuite sous une atmosphère réductrice créatrice d’électrons libres. Les propriétés électrochromes et photochromes ont été caractérisées après dépôt de films épais ou minces. Ainsi, les films épais de particules bleues, noires et jaunes montrent des électroactivités différentes lors de l’application d’un courant électrique. L’étude des films minces de WO3-x et de film « sandwich » de WO3-x + Ta2O5 révèle quant à elle une étonnante capacité de nos films à absorber dans le domaine du proche infrarouge lors de la photoréduction des ions W6+ en ions W5+ sous irradiation UV. Un traitement des données permet de montrer que, le photochromisme est associé à trois phénomènes d’absorption, d’énergies différentes, pour le film de WO3-x seul et à deux phénomènes pour le film « sandwich ». L’étude sur la réversibilité du phénomène a de plus montré une très bonne aptitude de nos films à se réoxyder (se décolorer) à l’air ambiant sans avoir recours à un traitement thermique ou chimique
In this study, polyol synthesis is used in order to obtain nanostructured tungsten oxides with a slight oxygen sub-stoichiometry (WO3-x). The particles obtained are blue and have interesting optical properties due to the presence of W5+ ions. The heat treatments of these particles at different temperatures or under different atmospheres allow the modification of their chemical composition and so their optical properties, therefore their color; their hue is ranging from pale yellow for compounds annealed under an oxidizing atmosphere and having only W6+ ions, to black for particles annealed under a reducing atmosphere creating free electrons. Electrochromic and photochromic properties have been characterized on thick or thin films. Thus, the thick films of blue, black and yellow particles show different electroactivities when an electric current is applied. The study of the thin films of WO3-x and “sandwich” film of WO3-x + Ta2O5 reveals an astonishing capacity of our films to absorb in the near infrared range during the photoreduction of the W6+ ions into W5+ ions under UV irradiation. The absorption curves show that photochromism is associated with three absorption phenomena of different energies for the WO3-x film and two phenomena for the “sandwich” film. The study on the reversibility of the phenomenon has also shown a very good ability of our films to reoxidize (discolour) in the ambient air without any thermal or chemical treatment

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Os vidros fosfatos contendo óxido de tungstênio apresentam grande interesse tecnológico devido às suas propriedades térmicas, mecânicas, ópticas e elétricas obtidas pela inserção de átomos de tungstênio dentro da rede vítrea. Neste trabalho foram preparadas amostras vítreas do sistema binário pelo método convencional fusão-resfriamento, variando x = 0, 10, 30 e 60. Os materiais inicialmente em pó foram misturados e aquecidos à temperatura de 400°C por 1h para a remoção de água e gases adsorvidos. Então, foram fundidos à temperatura de 1100°C, o líquido resultante foi mantido a esta temperatura por 1 h para garantir a homogeneização e finalmente o material fundido foi rapidamente resfriado em um molde de latão pré-aquecido abaixo da temperatura de transição vítrea. O recozimento foi realizado nesta temperatura por 1 h para minimizar as tensões mecânicas. As propriedades dielétricas e a dependência da condutividade com a composição química, temperatura e freqüência foram avaliadas pela espectroscopia de impedância (IS). Um mecanismo de condução iônico foi observado para composições de WO3 < 30 %mol. Uma mistura entre os mecanismos de condução iônica e eletrônica foi observada para WO3 > 30 %mol. Aglomerados das unidades de WO6 foram observados nas amostras contendo grandes quantidades de WO3 sugerindo uma possível conexão entre estes aglomerados e os mecanismos de condução. As técnicas espectroscopia no infravermelho com transformada de Fourier (FT-IR) e difração de raios-X foram usadas para a caracterização no presente trabalho.
Tungsten oxide containing-phosphate glasses present interesting technological because of the specific thermal, mechanical, optical and electrical properties obtained by insertion of tungsten atoms inside the glass network. Vitreous samples of binary system (100 – x) NaPO3 – (x) WO3 were prepared by conventional melt-quenching, varying x = 0, 10, 30 and 60. The powdered starting materials were mixed and heated at 400°C for 1 h to remove water and adsorbed gases. Then, they were melted at temperature around 1100°C, the resulting liquid was keep at that temperature for 1 h to ensure homogenization and finally the melt was rapidly cooled in a brass mold preheated below the glass transition temperature. Annealing was implemented at this temperature for 1 h to minimize mechanical stress. Dielectrics properties and the dependence of the conductivity with chemical composition, temperature and frequency have been evaluated by impedance spectroscopy (IS). An ionic conduction mechanism was observed for composition of WO3 < 30 mol%. A mixed electronic and ionic conductivity mechanism was observed for WO3 > 30 mol%. Clusters of WO6 units were observed in samples with high WO3 content and a possible connection between these clusters and the conduction mechanism has been suggested. In the present work the techniques Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XDR) was used for characterization.

Orientador: Marco Antonio Utrera Martines
Banca: Cláudio Luiz Carvalho
Banca: Silvio Cesar de Oliveira
Resumo: Os vidros fosfatos contendo óxido de tungstênio apresentam grande interesse tecnológico devido às suas propriedades térmicas, mecânicas, ópticas e elétricas obtidas pela inserção de átomos de tungstênio dentro da rede vítrea. Neste trabalho foram preparadas amostras vítreas do sistema binário pelo método convencional fusão-resfriamento, variando x = 0, 10, 30 e 60. Os materiais inicialmente em pó foram misturados e aquecidos à temperatura de 400°C por 1h para a remoção de água e gases adsorvidos. Então, foram fundidos à temperatura de 1100°C, o líquido resultante foi mantido a esta temperatura por 1 h para garantir a homogeneização e finalmente o material fundido foi rapidamente resfriado em um molde de latão pré-aquecido abaixo da temperatura de transição vítrea. O recozimento foi realizado nesta temperatura por 1 h para minimizar as tensões mecânicas. As propriedades dielétricas e a dependência da condutividade com a composição química, temperatura e freqüência foram avaliadas pela espectroscopia de impedância (IS). Um mecanismo de condução iônico foi observado para composições de WO3 < 30 %mol. Uma mistura entre os mecanismos de condução iônica e eletrônica foi observada para WO3 > 30 %mol. Aglomerados das unidades de WO6 foram observados nas amostras contendo grandes quantidades de WO3 sugerindo uma possível conexão entre estes aglomerados e os mecanismos de condução. As técnicas espectroscopia no infravermelho com transformada de Fourier (FT-IR) e difração de raios-X foram usadas para a caracterização no presente trabalho.
Abstract: Tungsten oxide containing-phosphate glasses present interesting technological because of the specific thermal, mechanical, optical and electrical properties obtained by insertion of tungsten atoms inside the glass network. Vitreous samples of binary system (100 - x) NaPO3 - (x) WO3 were prepared by conventional melt-quenching, varying x = 0, 10, 30 and 60. The powdered starting materials were mixed and heated at 400°C for 1 h to remove water and adsorbed gases. Then, they were melted at temperature around 1100°C, the resulting liquid was keep at that temperature for 1 h to ensure homogenization and finally the melt was rapidly cooled in a brass mold preheated below the glass transition temperature. Annealing was implemented at this temperature for 1 h to minimize mechanical stress. Dielectrics properties and the dependence of the conductivity with chemical composition, temperature and frequency have been evaluated by impedance spectroscopy (IS). An ionic conduction mechanism was observed for composition of WO3 < 30 mol%. A mixed electronic and ionic conductivity mechanism was observed for WO3 > 30 mol%. Clusters of WO6 units were observed in samples with high WO3 content and a possible connection between these clusters and the conduction mechanism has been suggested. In the present work the techniques Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XDR) was used for characterization.
Mestre

En los últimos años, las capas delgadas ópticamente activas han adquirido una gran importancia, debido a sus aplicaciones en dispositivos ópticos integrados y dispositivos láser. Un láser de capa delgada requiere capas con una elevada concentración de ión activo y, que a su vez, tengan una elevada sección eficaz de absorción y emisión. Este tipo de láseres presentan como ventajas una mejor refrigeración axial del medio evitándose así problemas como el efecto lente.
Los cristales monoclínicos de KRE(WO4)2 con RE=Y, Lu, son materiales utilizados como matrices láser de estado sólido debido a que permiten la substitución parcial o total de uno de los iones de su estructura, por otros iones activos en la emisión láser. Además, presentan una elevada estabilidad química. El objetivo de esta tesis ha sido la obtención de capas de Yb:KYW/KYW y Yb:KLuW/KLuW, de elevada calidad para la posterior realización de experimentos láser. El proceso de crecimiento ha sido optimizado con el principal objetivo de conseguir la máxima concentración de ión activo en las capas epitaxiales. Éstas han sido caracterizadas estructural y espectroscópicamente, mostrando resultados prometedores para la emisión láser.
La última parte de esta tesis se ha dedicado al estudio de los experimentos láser, en los que hemos conseguido obtener radiación láser con una longitud de onda alrededor de los 1030 nm con una elevada pendiente de eficiencia, la cual en algunos casos ha excedido las publicadas previamente para los correspondientes monocristales dopados con iterbio.
Keywords: Top Seeded Solution Growth, Liquid Phase Epitaxy, KRE(WO4)2, Materiales láser.
In the past few years, optically active thin layers have attracted much attention due to the possibility of using it in the integrated optics as well as thin disk laser technology. The thin disk laser concept need layers hundreds of microns thick highly doped with active ions and high absorption and emission cross section. The lasers based on thin films have the advantage of high beam quality with high efficiency, making possible to obtain high power with low thermal lensing.
The crystals of the monoclinic tungstates, such as KRE(WO4)2 with RE=Y, Lu, are attractive materials to be used as solid state host doped with lanthanide ions as ytterbium due to the possibility of obtaining highly doped active media.
The aim of this thesis is to investigate how to obtain thin layers of Yb:KYW/KYW and Yb:KLuW/KLuW, with quality enough for laser experiments. The growth process has been optimized in order to obtain crystalline layers with high ytterbium concentration. Structural and spectroscopic properties of these layers have been studied, suggesting that laser emission can be achieved.
The last part of thesis is dedicated to study the laser experiments. We have achieved laser emission around 1030 nm with high slope efficiency, which in some cases exceeded the reported for the ytterbium doped bulk crystals
Keywords: Top Seeded Solution Growth, Liquid Phase Epitaxy, KRE(WO4)2, Laser materials

The aim of this study is to analyse how pornography is used in the American comics X-Men, published by Marvel under the authorship of Chris Claremont.

I have applied Butler and MacKinnons theories about pornography as a performative speech, to this special art form. I have also investigated how censorship has influenced the comics evolution and whether it has affected the way women and sexual and ethnical minorities are represented. To corroborate how these theories apply, I have analysed three main female fig-ures in The X-Men comics - Storm, Phoenix and Shadowcat - and I have tried to identify how they relate to existing stereotypes.

The conclusion of this essay is that the women characters in X-Men break the existing stereo-types and create new implications. This reinforces Butler’s theory about the possibility to re-verse hate speech and diminishes MacKinnons perspective of pornography as an imperative.

Ce travail vise a demonter le role de reactif que peut jouer le support oxyde lors de la synthese de catalyseurs heterogenes. Le support est generalement considere comme inerte chimiquement au cours des premieres etapes de preparation d'un catalyseur, et on considere que son role se limite a disperser la phase active. Nous montrons i) qu'il est necessaire de prendre en compte la reactivite du support oxyde et ii) que cette prise en compte beneficie des concepts et methodes etablis en geochimie. Ainsi, nous montrons que l'alumine n'est pas thermodynamiquement stable en solution. Sa mise en suspension conduit a la formation d'un hydroxyde al(oh) 3 par un mecanisme de dissolution/precipitation. La formation de cette phase est inhibee par la presence d'anions (moo 2 4, wo 2 4) en solution. En presence de cations (pt(nh 3) 2 + 4), cette formation depend de la methode de preparation. Cette phase influence le comportement du catalyseur final puisqu'elle controle la quantite d'hydrogene spillover formee pendant la reduction. Dans le cas de la preparation de catalyseurs moo x/al 2o 3 par adsorption a l'equilibre, nous montrons qu'il se forme en solution un heteropolyanion al(oh) 6mo 6o 3 1 8 par simple mise en contact d'une suspension d'alumine et d'une solution d'heptamolybdate et que cette espece est deposee en surface du support. La formation de ce compose mixte augmente thermodynamiquement la solubilite du support. Dans le cas d'une preparation par impregnation a sec, ce compose mixte precipite sous forme d'un sel en surface du support ce qui conduit, apres calcination, a la formation d'oxyde moo 3. La formation de ce sel est evitee en lyophilisant le catalyseur ce qui limite la dissolution du support et inhibe la formation ulterieure d'oxyde. Ces conclusions sont etendues a la preparation de catalyseurs wo x/al 2o 3 ou l'on met en evidence la formation d'aluminotungstates en solution et leur depot en surface du support.

Les bronzes monophosphates de tungstene a tunnels pentagonaux (mptb p), de formule (po 2) 4(wo 3) 2 m, sont des materiaux de basse dimensionnalite, qui presentent des instabilites electroniques du type onde de densite de charge (odc). Les temperatures de peierls dependent du parametre m qui caracterise l'epaisseur des couches conductrices de type wo 3. Dans ce travail, cinq nouvelles structures ont ete resolues par diffraction des rayons x sur monocristal, a temperature ambiante. Quatre d'entre elles (2m = 5 + 5, m = 7, m = 9 and m = 12) correspondent a la forme basse temperature tandis que le compose m = 10 se trouve, a temperature ambiante, dans la forme haute temperature qui est modulee. La structure a ete resolue en utilisant le formalisme 4d. La modulation est displacive, commensurable, et porte uniquement sur la atomes de tungstene. Une revue de tous les termes connus jusqu'a maintenant (2 m 14) nous a conduit a proposer une loi structurale basee sur le principe d'enchainement des octaedres wo 6 dans les couches de type wo 3, expliquant ainsi les differentes symetries observees en fonction de la parite de m. Le caractere bidimensionnel des composes a ete confirme a l'aide de la theorie des valences formelles. Les bronzes de tungstene a x(po 2) 4(wo 3) 2 m (a = k, na, pb) ont egalement ete etudies. On montre qu'il est possible d'inserer des cations de la taille de na + dans les cages pentagonales. Les relations structurales existantes entre les differents bronzes phosphates de tungstene (mptb p, mptb h, dptb p, dptb h) sont analysees. Une transition de type peierls a ete caracterisee dans k xp 4w 8o 3 2 (m = 4mptbh), la temperature de transition dependant du taux de potassium x. Les structures des bronzes mptb h k xp 4w 1 2o 4 4 (m = 6) et pb xp 4w 1 4o 5 0 (m = 7) ont ete resolues et comparees aux autres membres de la famille. Les diverses symetries rencontrees sont expliquees sur la base des differents modes de basculement des octaedres wo 6.

碩士
逢甲大學
材料科學所
99
In the present study, tungsten oxide, titania, and tungsten oxide-titania nanotube (NT) or nanorod (NR) were fabricated on anodic aluminum oxide (AAO) template by sol-gel technique. Experimental results shows that commercial aluminum sheet can be prepared into AAO template using oxalic acid and phosphorous acid solution. After pore-widening with various time, the pore size by anodizing in oxalic and phosphorous acid solutions were ranged from 47 to 103 nm and 110 to 250 nm, respectively. The porosity were in the range of 6.2 ~ 43.3 % and 10.0 ~ 60.9 %, respectively. By both methods, the pores can arrange uniformly. After pore widening in phosphorous acid solution for 60 minutes, the pore size is 175 ± 30 nm with a porosity of 36.4 % and pore density of 4.23 x 1014 cm-2, and is suitable to be used as templates to grow nanorod or nanotube. Tungsten oxide NT and NR were successfully grown on AAO template by sol-gel process. The results showed that tungsten oxide NT and NR are amorphous after heat treating at 200 or 300 oC and exhibit monoclinic WO3 phase after heat treating at 400 and 550 oC. Meanwhile, titania NT and NR exhibit anatase phase after heat treating at a temperature ranged from 200 to 550 oC. Preparation of tungsten oxide-titania composite NR were attempted by using various kinds of precursors including tungsten hexachloride, sodium tungstate dihydrate, ammonium tungsten oxide, titanium(IV) tetrafluoride, and titanium(IV) n-butoxide. A combination of titanium(IV) tetrafluoride and sodium tungstate dihydrate precursors can fabricate successfully composite NR where oxygen, titanium, and tungsten elements are distributed homogeneously.

碩士
國立成功大學
材料科學及工程學系
106
In our study, oxygen-vacancy-rich tungsten oxide nanowires were synthesized on Si via grain-by-grain thermal evaporation method without any catalyst; also, WO3-x nanowires were grown on W foil as comparison on their physical properties and growth mechanism. In the SEM cross-section images, we have clearly found that there is no thin film formation in the growth mechanism of tungsten oxide grown on Si. It shows that this process is a new grain-by-grain thermal evaporation method which nanowires grown from the previously deposited tiny nanoparticles. Surprisingly, the oxygen-vacancy-rich tungsten oxide nanowires grown on Si were found to have unusual W5+ dominated energy bond and the ratio of tungsten to oxygen was about 5:13 based on XPS analysis. TEM studies show that the lattice arrays of oxygen-vacancy-rich tungsten oxide nanowires grown on Si were crystalline, while those of WO3-x nanowires grown on W foil were improved in terms of crystallization with increase of growth temperature. We demonstrated this result with XRD analysis as well. For physical property measurements, the oxygen-vacancy-rich nanowire grown on Si had a very low resistivity of 7.03 x 10-4 Ω ‧ cm, while the resistivity of WO3-x nanowires grown on W decreased as the growth temperature rises. Additionally, we found that WO3-x nanowires exhibit different magnetic properties depending on the valence state of tungsten. Notably, the oxygen-vacancy-rich tungsten oxide nanowires grown on Si possessed special antiferromagnetic properties. For visible light photocatalytic applications, the WO3-x nanowires grown on W at the lowest temperature have the best degradation efficiency to methylene blue solution.

碩士
義守大學
材料科學與工程學系碩士班
96
Electrochromic (EC) materials are able to change their optical properties by the application of an electrical voltage. When the applied voltage has become reverse bias, the optical properties induced reversibly. This kind of coloration was called “Electrochromism”. Recently, the performance of devices has been improved through deposition of multilayers. This allows the property of the devices can be enhanced or complementary. This work is aimed at the fabrication of such an all solid state EC device with complementary structure by using WO3-x film (colouring under charge insertion, electrochromic film), NiOZ film (colouring under charge extraction, sub-electrochromic film), and (LiBO2:LiF) film (as the ion conductor). All films used for the construction of an EC device were prepared with different O2/Ar ratio by RF magnetron sputtering. We also focus on the effect of LiF doping on the property of electrochromic devices, and will discuss the relations between the microstructure, coloration efficiency of the EC device and the concentration of Li+. Experimental results indicated that the tungsten oxide films showed good reversibility. At the O2/Ar ratio of 2.5, the transmission change between colored and bleached states at a wavelength of 550 nm was more than 36 %.

This research intends to examine if there were significant differences on the brand engagement and on the electronic word of mouth (e-WOM)1 referral intention through Facebook between Generation X and Generation Y (also called millennials). Also, this study intends to examine if there are differences in the motivations that drive these generations to interact with brands through Facebook. Results indicated that Generation Y members consumed more content on Facebook brands’ pages than Generation X. Also, they were more likely to have an e-WOM referral intention as well as being more driven by brand affiliation and opportunity seeking. Finally, currently employed individuals were found to contribute with more content than students. This study fills the gap in the literature by addressing how marketing professionals should market their brand and interact and engage with their customers, based on customers’ generational cohort.