Rozprawy doktorskie na temat „Oxide/oxide composite”

De manière générale, les composites oxyde/oxyde sont la plupart du temps élaborés par frittage, par voie sol-gel ou par infiltration en phase gazeuse, CVI (« Chemical vapor infiltration »). Ces techniques d’élaboration comportent de nombreuses étapes engendrant un temps long d’élaboration ce qui peut entraîner une détérioration des propriétés du composite. Cette thèse s’intéresse à un procédé original et rapide de densification de préformes fibreuses développé par le Commissariat à l’Energie Atomique et aux énergies alternatives (CEA) : la caléfaction. Ce procédé est connu pour élaborer des composites C/C ou C/SiC à partir d’un précurseur liquide. Cependant, la possibilité d’élaborer des composites oxyde/oxyde n’a jamais été testée. L’objectif de ce travail est d’étudier la réalisation de composites oxydes/oxydes par ce procédé. Plusieurs matrices ont été réalisées telles que la silice, l’alumine et le système ternaire aluminosilicate de baryum, BaSi2Al2O8. Plusieurs paramètres expérimentaux ont été étudiés tels que la température d’élaboration, le temps de manipulation et la composition du précurseur. Des caractérisations microstructurales et physico-chimiques ont permis de caractériser les matériaux élaborés. Plusieurs modifications ont été apportées au montage expérimental afin de permettre une meilleure reproductibilité des essais et un meilleur suivi thermique lors de l’élaboration de matrice oxyde
Nowadays, oxide/oxide composites are most of the time developed by sintering, sol-gel process or CVI (Chemical Vapor Infiltration). These techniques include many steps of synthesis leading to a long time of synthesis and possible deteriorations of the properties of the composite. This thesis focuses on an original and rapid process developed by French Alternative Energies and Atomic Energy Commission (CEA): the film boiling chemical vapor infiltration. This technique is already used to synthesize C/C and C/SiC composites but works have never focused on oxide/oxide composites. The main goal of this thesis is to synthesize oxide/oxide composites by film boiling chemical vapor infiltration. Works were focused on alumina, silica and barium aluminosilicate matrices. Several experimental parameters were studied: temperature, time and liquid precursor. Microstructural and physicochemical characterizations were done on composites. Several modifications of the experimental setup have been made in order to allow a better reproducibility of the tests and a better thermal monitoring

The introduction of ceramic matrix composites (CMCs) for structural applications in the hot section of a gas turbine provides many potential benefits over conventional alloy materials, including facilitating elevated operating temperatures. The development of an oxide-oxide CMC composed of commercially available Nextel 720 (3M) fibres within a porous alumina matrix was presented. A simple, low cost processing method involving slurry impregnation and subsequent consolidation and densification was developed, facilitating the production of dried pre-impregnated fabric (‘pre-preg’) that can be stored in ambient conditions. Detailed investigation into the effect of three types of PVA binder, the effect of 0-20wt% additions of an alumina precursor (ACH), the influence of a bimodal particle distribution and the effect of sintering at temperatures between 1100 and 1300°C on processing and mechanical properties was completed in order to optimise the material. The optimised composite material, composed of Nextel 720 fibres within a submicron alumina particle matrix with 10wt% ACH sintered at 1200°C, exhibited mean flexural strength >205MPa, short beam shear strength >12MPa and tensile strength >146MPa. These results were comparable to similar oxide CMCs previously reported, validating this material.

Les composites oxyde-carbonate pourraient constituer des électrolytes pour les SOFC fonctionnant entre 400-600°C car ils attendent une conductivité de 0,1 S/cm à 600°C. Une meilleure compréhension de l'origine de leurs performances est à ce jour nécessaire. Pour y parvenir, une approche combinée théorique et expérimentale a été développée. La conductivité, mesurée à travers la SIE, a été étudiée en fonction de la phase oxyde ou carbonate et de l'atmosphère de travail. Les résultats sur les composite de CeO2 ou YSZ ont montré que seule l'interface peut expliquer des observations surprenantes. De la réactivité a été observée dans le cas des composites à base de TiO2. On a donc proposé une stratégie computationnelle qui utilise des calculs DFT périodiques: la structure du bulk de chaque phase a d'abord été étudiée afin de trouver un bon protocole computationnel, qui a été ensuite utilisé pour identifier un modèle pour la surface la plus stable des deux phases. Ces modèles de surfaces ont donc été combinés pour obtenir un modèle de l'interface oxyde-carbonate, utilisable comme structure de départ pour des calculs DFT et de DM. Cette stratégie a permis d'obtenir des informations sur structure, stabilité et propriétés électroniques des composites. YSZ-LiKCO3 a été utilisé pour mieux comprendre l'effet des interfaces sur le transport de différentes espèces, tandis que le modèle de l'interface entre TiO2 et LiKCO3 a été utilisé pour étudier la réactivité entre ces deux matériaux. Finalement, ces résultats ouvrent la voie vers une plus grande compréhension des principes de fonctionnement des SOFC basées sur les électrolytes composites oxyde-carbonate
Oxide-carbonate composites are promising electrolytes for LT-SOFC, thanks to their high conductivity (0.1-1 S/cm at 600°C). A deeper understanding on the origins of their improved performances is still necessary. For this purpose, a combined theoretical and experimental approach was developed. We first studied systematically the conductivity of the material, measured through EIS, as a function of different oxide or carbonate phases and of the operating atmosphere. Results on YSZ- and CeO2-based materials indicate that by only taking into account the interfaces it is possible to rationalize some surprising observations, while reactivity issues have been observed for TiO2-carbonate composites. We then proposed a computational strategy based on periodic DFT calculations: we first studied the bulk structure of each phase so as to select an adequate computational protocol, which has then been used to identify a suitable model of the most stable surface for each phase. These surface models have thus been combined to obtain a model of the oxide-carbonate interface that through static DFT and MD provides a deeper insight on the interface at the atomic level. This strategy was applied to provide information on the structure, stability and electronic properties of the interface. YSZ-LiKCO3 was used as a case study to investigate the conduction mechanisms of different species. Results showed a strong influence of the interfaces on the transport properties. The TiO2-LiKCO3 model was, instead, used to investigate the reactivity of these materials. Overall, these results pave the way toward a deeper understanding of the basic operating principles of SOFC based on these materials

Dans l’industrie de l’aéronautique et de la défense, les applications thermostructurales nécessitent des matériaux toujours plus performants, alliant résistance mécanique, réfractarité et légèreté. Pour répondre à ces exigences, les matériaux composites à matrice céramique tout oxyde (OCMC) sont prometteurs. Parmi les matrices de ces OCMC, l'aluminosilicate de baryum (BAS) se distingue par ses propriétés physiques intéressantes, notamment en tant que matériau pour radômes. Cependant, pour rendre ce matériau fonctionnel à haute température, proche de sa température de fusion (1750°C), il est essentiel de le renforcer avec un matériau thermochimiquement stable et doté d'une architecture adaptée. Plusieurs thèses antérieures ont permis de maîtriser la phase hexagonale du BAS. La nature chimique du renfort présentant la stabilité souhaitée avec le BAS a été identifiée et des OCMC Al2O3/BAS à renfort fibreux 1D, 2D ont commencé à être élaborés. Toutefois, pour obtenir des matériaux ayant des propriétés accrues pour des conditions thermostructurales sévères, il est nécessaire de réaliser ces OCMC avec une architecture « 3D » du renfort. Le sujet présenté porte sur la réalisation d'un tel composite avec une architecture complexe (3D) du renfort fibreux et sur l'évaluation de ses propriétés. Pour répondre à cet objectif, ces travaux de recherche incluent : l'étude du frittage du BAS-H afin d’anticiper son comportement en tant que matrice, l'amélioration de son comportement rhéologique en suspension afin de favoriser son infiltration dans une préforme de renforts fibreux, et la mise en place d'un procédé d'imprégnation adapté aux renforts 3D. À la suite de ces études, la fabrication d'OCMC Al2O3/BAS a été réalisée, mettant en évidence des caractéristiques prometteuses en lien avec l'application
In the aerospace and defense industry, thermostructural applications require increasingly high-performance materials, combining mechanical strength, refractoriness, and lightness. To meet these demands, all-oxide ceramic matrix composites (OCMC) are considered promising candidates. Among the matrices for these OCMCs, barium aluminosilicate (BAS) stands out due to its advantageous physical properties, particularly as a material for radomes. However, to make this material functional at high temperatures, close to its melting point (1750°C), it is essential to reinforce it with a thermochemically stable material that has an appropriate architecture. Previous theses have successfully mastered the hexagonal phase of BAS. The chemical nature of the reinforcement, which offers the desired stability with BAS, has been identified, and OCMC Al2O3/BAS composites with 1D and 2D fibrous reinforcements have been developed. However, to achieve materials with enhanced properties under severe thermostructural conditions, these OCMCs need to be produced with a "3D" reinforcement architecture. This work focuses on the development of such a composite with a complex (3D) fiber reinforcement architecture and the evaluation of its properties. To achieve this, the research involves studying the sintering of BAS-H to predict its behavior as a matrix, improving its rheological behavior in suspension to facilitate infiltration into the fibrous reinforcement preform, and implementing an impregnation process suitable for 3D reinforcements. Following these studies, the fabrication of OCMC Al2O3/BAS was completed, demonstrating promising characteristics for the intended application

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The drive to produce low cost and efficient solar cells to replace solid state silicon cells has led to the rapid growth of nanotechnology in the PV sector. The extremely thin absorber (ETA) layer solar cell is a device that relies on the use of nanostructured anodes. The very high surface area of the metal oxides enhances the efficiency of the devices by increasing light harvesting in the cell. TiO2 has been the most common material of choice in these cells. However, alternative materials such as composite electrodes ZnO/TiO2, ZnO/SnO2, ZnO/Al2O3 have been considered. These systems also have the ability to improve charge carrier separation and broaden their photoresponse region. In addition to selecting materials with the correct energetics, the morphology of the metal oxide particles plays an important role in these devices. The ability to manipulate the shape, size, and surface to volume ratio of these oxides is critical in influencing the materials chemical, electronic and optical properties. In this thesis the fabrication of composite (ZnO,SnO2) electrodes by aerosol assisted chemical vapor deposition (AACVD) was investigated. By simply varying the Zn:Sn ratio in the precursor solution, a range of (ZnO,SnO2) composite materials along with single phase ZnO and SnO2 has been fabricated. It has been found that the morphology of the deposited electrodes is highly dependent on the Zn content with electrodes with morphologies ranging from nanoplates, to nanocolumns, to highly compact structures have been deposited. The dependence of the Zn content in the deposition solution on the photoelectrochemical (PEC), optoelectronic, photon to electron conversion efficiency (APCE) and photovoltaic characterization was investigated. ETA solar cells with FTO/(ZnO,SnO2)/In2S3/PbS/PEDOT:PSS/Cgraphite/FTO structures were successfully fabricated to demonstrate the suitability of (ZnO,SnO2) anodes in these devices. This work has shown that AACVD is a useful technique for engineering the properties of semiconducting electrodes for PV applications.

Los materiales llamados semiconductores (muchos de ellos óxidos metálicos) son capaces de generar portadores de carga (huecos y electrones) cuando se iluminan con luz suficientemente energética. Estos portadores son capaces de sostener reacciones redox. Los electrones de la banda de conducción (BC) y los huecos de la banda de valencia (BV) pueden reducir y oxidar, respectivamente, especies que estén en contacto directo con el semiconductor. Además, los electrones y huecos fotogenerados pueden eliminarse en el proceso que se conoce como recombinación. El grado en que se producen estas reacciones redox depende de la eficiencia en la separación de las cargas fotogeneradas. Una separación de los portadores efectiva da lugar a aplicaciones. En esta tesis se abordan detalladamente los procesos de foto(electro)cromismo y foto(electro)catálisis. La separación de los portadores de carga en un material puede verse favorecida por: - La creación de heterouniones entre dos semiconductores (óxidos) distintos. - El diseño adecuado de la nanoestructura de los óxidos: estructuras ordenadas y/o estructuras con mucha superficie interfacial. - La modificación de la superficie o del seno de los óxidos semiconductores (dopado). En las aplicaciones prácticas se pretende que haya una transferencia de carga capaz de impulsar el proceso de interés. Por lo tanto, el control de los procesos de transferencia de carga del semiconductor a través de sus interfases es fundamental en el diseño de materiales para una determinada aplicación. Teniendo todo esto en cuenta, los objetivos establecidos para esta tesis han sido: I. Preparar estructuras ordenadas de nanobarras de α-Fe2O3 (hematita) sobre vidrio conductor e investigar sus propiedades catalíticas para fotooxidar agua. Optimizar el proceso de fotooxidación del agua sobre electrodos de hematita aplicando un pretratamiento electroquímico. Estudiar el efecto del pretratamiento sobre la composición, morfología y estructura electrónica de la hematita. II. Modificar los electrodos de hematita con Ti de dos maneras distintas, una que afecte principalmente a todo el material y otra que afecte a la superficie de la hematita, con el fin de mejorar sus propiedades catalíticas para fotooxidar agua. Aplicar y estudiar el pretratamiento reductivo para los electrodos de hematita tras ser modificados con Ti. III. Modificar la superficie de las nanobarras de hematita con trimetilaluminio (TMA) mediante depósito de capa atómica (Atomic layer deposition - ALD) desde fase gas o por adsorción en fase líquida, con el fin de mejorar sus propiedades fotoelectroquímicas para oxidar agua. Investigar los cambios en las propiedades electrónicas y electroquímicas de los electrodos de hematita tras ser modificados. IV. Preparar electrodos nanoporosos de Ni(OH)2 sobre vidrio conductor (SnO2:F - FTO) e investigar sus propiedades catalíticas para oxidar agua en medio alcalino en función de la cantidad depositada y de la morfología del hidróxido. V. Preparar electrodos nanoporosos basados en capas mixtas TiO2/Ni(OH)2 sobre vidrio conductor e investigar la separación de carga en los mismos con el fin de estudiar su posible utilización en dispositivos fotoelectrocrómicos. Estudiar las cinéticas de los procesos de la coloración y decoloración a través de medidas (foto)(espectro)electroquímicas. Las siguientes cinco conclusiones generales resumen los resultados más importantes en relación con los cinco objetivos previamente mencionados. I. En este estudio se ha conseguido sintetizar barras de hematita nanoestructuradas y con orientación (110) depositadas sobre vidrio conductor a través de un método de baño químico. Estas capas se han utilizado para estudiar el proceso de fotoxidación del agua. Para mejorar las propiedades fotocatalíticas de estas capas se ha empleado un pretratamiento electroquímico simple y altamente controlable que consiste en la aplicación de potenciales negativos por un tiempo muy corto (en el rango de segundos). Este pretratamiento da lugar a una mejora de la fotocorriente de hasta ocho veces asociada a la oxidación del agua, junto con un desplazamiento negativo de 20 mV del potencial de inicio de la fotocorriente. Este pretratamiento también induce cambios en la morfología de los electrodos, capacidad electrocatalítica y en su estructura electrónica. Por lo tanto, el dopado electroquímico no puede considerarse simplemente como un dopado tipo-n capaz de aumentar la fotoactividad de las capas debido a una mejora en el transporte de electrones. En realidad, los resultados obtenidos muestran claramente que se producen cambios mucho más profundos en la estructura electrónica y la composición de las capas que mejoran significativamente las propiedades tanto electro- como foto-electrocatalíticas. De hecho, ambas propiedades siguen una tendencia general similar con el potencial del pretratamiento empleado. Dentro de un marco más general, el pretratamiento reductivo puede ser utilizado también para la mejora de estructuras de hematita previamente modificadas o dopadas. Desde una perspectiva práctica, el dopaje electroquímico tiene la limitación de no ser permanente, lo que significa que debe aplicarse periódicamente. Esto no es un inconveniente serio en un dispositivo práctico, siempre y cuando la mejora inducida por el pretratamiento compense claramente esta limitación. II. Se han diseñado dos estrategias de modificación de hematita económicas utilizando una disolución con un mismo precursor de Ti. En un procedimiento el Ti se introduce en la estructura de hematita, mientras que en la otra, se forma una capa de TiO2 ultra-delgada que cubre por completo la superficie de hematita. Ambas modificaciones inducen un aumento significativo en la fotocorriente para la oxidación de agua (4 - 6 veces). La razón principal de la mejora en las capas modificadas con Ti es la disminución significativa del proceso de recombinación. El freno de la recombinación en las muestras modificadas con una sobre-capa de TiO2 se atribuye principalmente al bloqueo de estados superficiales, mientras que en el caso de las muestras modificadas con Ti intercalado en la estructura se relaciona principalmente con el aumento del área interfacial junto con un aumento de la conductividad electrónica. III. Se han preparado electrodos basados en nanobarras de hematita modificadas con TMA empleando una estrategia simple de impregnación a partir de una disolución de hexano. Los resultados se han comparado con los obtenidos modificando los electrodos de hematita con TMA por ALD. Los electrodos modificados muestran una importante mejora, aumentando tres veces la fotocorriente de oxidación de agua. Por un lado, el TMA bloquea los estados superficiales de hematita y por otro, induce un enriquecimiento electrónico. Tal conclusión fue confirmada cualitativamente en el caso de muestras modificadas con TMA utilizando la técnica de ALD. A pesar de que la modificación en fase líquida ha dado una foto-actividad menor en términos de la magnitud de la fotocorriente que la de ALD, representa una alternativa mucho más económica. Además, el método de impregnación a partir de una disolución es industrialmente escalable. Dentro de un marco más general, la modificación con TMA es potencialmente aplicable a otros semiconductores tipo n. Por lo tanto, podría constituir una estrategia relevante para mejorar la eficiencia de la fotooxidación de agua utilizando otros materiales tales como TiO2, BiVO4, WO3, entre otros. IV. Este estudio muestra que, a través de un procedimiento simple y potencialmente escalable como el baño químico, se pueden producir capas nanoestructuradas ultra-finas de Ni(OH)2 sobre FTO. Estas películas se caracterizan por una gran actividad electrocatalítica. Son capaces de oxidar el agua desarrollando corrientes iguales o superiores a las de películas mucho más gruesas. Esto último está relacionado con el hecho de que la reacción de generación de oxígeno depende de la formación de níquel (IV) que puede verse limitada por la baja conductividad eléctrica de Ni(OH)2. Por tanto, el proceso se favorece en capas finas donde la distancia al substrato conductor es menor. Esta noción es muy importante de cara a su aplicación. No solo se minimiza la cantidad de Ni(OH)2 necesaria sino se producen también ánodos altamente eficientes transparentes y prácticamente incoloros. V. Este trabajo ha mostrado que una capa nanoporosa mixta y delgada de TiO2/Ni(OH)2 depositada sobre vidrio conductor y sometida a un potencial catódico constante puede colorearse al ser iluminada con luz ultravioleta, mientras que se decolora completamente cuando se interrumpe la iluminación. Este fenómeno se ha denominado “fotoelectrocromismo reversible potenciostatico”. El valor del potencial empleado permite seleccionar tanto el contraste en la coloración como la cinética de la decoloración. Este fenómeno es posible debido a la existencia de un área interfacial extendida de contacto TiO2/Ni(OH)2 debido a la estructura nanoporosa que permite un contacto íntimo entre ambos componentes. Desde un punto de vista práctico, estos resultados podrían facilitar el desarrollo de ventanas inteligentes con una nueva funcionalidad porque, además del convencional efecto electrocrómico, trabajarían en un segundo modo, en el que, la coloración respondería a la intensidad de la luz incidente (a un potencial constante).

Solid oxide fuel cells (SOFCs) are considered as one of the most promising powergeneration technologies due to their high energy conversion efficiency, fuel flexibilityand reduced pollution. The current SOFCs with yttria-stabilized zirconia (YSZ)electrolyte require high operation temperature (800-1000 °C), which not only hinderstheir broad commercialization due to associated high cost and technologicalcomplications. Therefore, there is a broad interest in reducing the operating temperatureof SOFCs. The key to development of low-temperature SOFCs (LTSOFCs) is to explorenew electrolyte materials with high ionic conductivity at such low temperature (300-600 °C).Recently, ceria-based composite electrolyte, consisting of doped cerium oxide mixedwith a second phase (e.g. Na2CO3), has been investigated as a promising electrolyte forLTSOFCs. The ceria-based composite electrolyte has shown a high ionic conductivityand improved fuel cell performance below 600 °C. However, at present the developmentof composite electrolyte materials and their application in LTSOFCs are still at an initialstage. This thesis aims at exploring new composite systems for LTSOFCs with superiorproperties, and investigates conductivity behavior of the electrolyte. Two compositesystems for SOFCs have been studied in the thesis.In the first system, a novel concept of non-ceria-salt-composites electrolyte, LiAlO2-carbonate (Li2CO3-Na2CO3) composite electrolyte, was investigated for SOFCs. TheLiAlO2-carbonate electrolyte exhibited good conductivity and excellent fuel cellperformances below 650 oC. The ion transport mechanism of the LiAlO2-carbonatecomposite electrolyte was studied. The results indicated that the high ionic conductivityrelates to the interface effect between oxide and carbonate.In the second system, we reported a novel core-shell samarium-doped ceria(SDC)/Na2CO3 nanocomposite which is proposed for the first time, since the interface isdominant in the nanostructured composite materials. The core-shell nanocompositeparticles are smaller than 100 nm with amorphous Na2CO3 shell. The nanocompositeelectrolyte was applied in LTSOFCs and showed excellent performance. Theconductivity behavior and charge carriers have been studied. The results indicated that H+conductivity in SDC/Na₂CO₃ nanocomposite is predominant over O2- conductivity with1-2 orders of magnitude in the temperature range of 200-600 °C. It is suggested that theinterface in composite electrolyte supplies high conductive path for proton, while oxygenions are most probably transported by the SDC nano grain interiors. Finally, a tentativemodel “swing mechanism” was proposed for explanation of superior proton conduction.

QC 20100930

Membrane structure modification is a common approach to enhance membrane properties and performance. For example, the addition of dopants to the membrane casting solution has been observed to increase hydrophilicity, alter surface and internal pore structure, increase thermal and mechanical resistance, and impart anti-fouling properties. In this study, it was evaluated how the addition of individual and simultaneous nanoclay and polyethylene oxide (PEO) dopants affected the structure and performance of polysulfone (PSU) ultrafiltration membranes. Membrane performance was evaluated in the cross-flow configuration. The pure water permeability of the neat PSU membrane was 15 L/m².h.bar and at the optimal dosage of the individually doped membranes was 1.5% weight nanoclay to PSU and 5% weight PEO to PSU resulting in permeability of 56 and 237 L/m².h.bar, respectively. Simultaneous doping using the optimal individual weight percentages had a lower effect resulting in a permeability of 192 L/m².h.bar, in contrast the simultaneous addition of 4.5% nanoclay and 5% PEO had a higher effect resulting in a permeability of 319 L/m².h.bar. The control membrane was compared to the referred membranes and with the 4.5% nanoclay membrane (best permeability only when combined with PEO). These membranes were further examined to determine dopant effects on pore microstructure, superficial charge, separation performance, and fouling susceptibility. In general, doping with nanoclay improved membrane thermal/mechanical resistance and permeability with minimal loss in rejection. Doping with PEO resulted in a greater permeability as compared to nanoclay; however, PEO doping decreased rejection, mechanical resistance, and increased irreversible fouling. Thus, both advantageous and disadvantageous effects should be considered when selecting a dopant to optimize membrane performance.
A modificação da estrutura de membranas é uma abordagem utilizada para melhorar as propriedades de membranas e desempenho de um sistema. Por exemplo, a adição de dopantes na solução de síntese da membrana permite aumentar a hidrofilicidade, alterar a estrutura de poros superficiais e internos e conferir propriedades anti-depósitos. Neste estudo, foi avaliada como a adição de óxido de polietileno e de nano-argila afetam a estrutura e desempenho de membranas de ultrafiltração de polisulfona (PSU). O desempenho da membrana foi avaliado na configuração de fluxo paralelo (cross-flow). A permeabilidade média à água pura da membrana de PSU pura foi de 15 L/m2.h.bar. As dosagem ótimas das membranas dopadas individualmente foram de 1,5% em massa de PSU para nano-argila e 5% em massa de PSU para PEO, resultando em permeabilidades médias de 56 e 237 L/m2.h.bar, respectivamente. A dopagem simultânea usando ambas as percentagens individuais ótimas teve um efeito menor do que o esperado, resultando em uma permeabilidade média de 192 L/m2.h.bar. Em contraste, verificou-se que a adição simultânea de 4,5% de nano-argila combinada com 5% de PEO teve um efeito maior do que o uso isolado dos aditivos, resultando em uma permeabilidade média de 319 L/m2.h.bar. Desta forma, a membrana de controle foi comparada com as referidas membranas e com membranas compostas somente por nano-argila a 4,5. Estas membranas foram ainda examinadas em detalhes para determinar os efeitos dos dopantes na microestrutura dos poros, cargas superficiais, desempenho da separação, sensibilidade à formação de depósitos, rugosidade superficial e propriedades térmicas e mecânicas. Verificou-se que a dopagem com nano-argila melhora a resistência térmica e mecânica e a permeabilidade das membranas, com uma perda mínima na rejeição. A dopagem com PEO resultou em um aumento notável de permeabilidade em comparação com a adição individual de nano-argila. No entanto, a capacidade de rejeição e resistência térmica e mecânica destas membranas diminuem e a formação de depósitos irreversíveis aumenta. Desta forma, avalia-se que para a utilização de mais de um tipo de dopante os efeitos vantajosos e desvantajosos devem ser considerados individualmente e em conjunto no esforço de se otimizar o desempenho de sistemas de membranas.

Widespread use of solid oxide fuel cells is hindered by a lack of long-term durability of seals between metallic and ceramic components caused by thermal expansion mismatch induced cracking. A novel gas seal design incorporating an engineered thermal expansion gradient in a SrO-La2O3-Al2O3-B2O3-SiO2 glass matrix with a TiNiHf shape memory alloy mesh for active stress relief and crack healing is being developed. Coefficient of thermal expansion (CTE) measurements of the seal and fuel cell components shows the possibility for a thermal expansion gradient. Differential scanning calorimetry and microscopy have shown that the TiNiHf alloy has a shape memory transition in the desired range of 200-250ºC. The oxide glass partially crystallizes during thermal cycling which has been observed through X-ray diffraction and dilatometry. The CTE decreases from 9.3à 10-6/°C to 6.6à 10-6/°C after thermal cycling. Neutron diffraction data from TiNiHf /glass composite samples reveals that the TiNiHf alloy has the ability of absorbing residual stresses from a glass matrix during martensitic phase transition. There is evidence from microscopy that the glass composition is important in determining if reaction will occur with the TiNiHf alloy. The TiNiHf alloy mesh structures can be created using the 3D printing process. This process has been adapted to allow for printing of very thin wire mesh structures of Ni and NiTi powders with a more suitable binder solution. A bi-layer test fixture has been developed which will be useful for assessing leak rate through seal materials.
Master of Science

This master thesis report evaluatesthe lubricating effect of graphene (G)and graphene oxide (GO). Thesematerials have been added, in particlecondition, in Ag-based slidingcontacts and lubricating greases. Thework focuses on the tribologicalevaluation of these materials,especially friction, wear and contactresistance analyses. The friction andwear behaviors of Ag-based contactscontaining of a wide concentrationrange of graphene and graphene oxideare tested against pure silver using atest load of 2 and 10 N at a constantspeed of 5 cm/s. It was revealed thatsmall amounts of G and GO are able tosignificantly reduce the frictioncoefficient and wear rate. Contactresistance measurements revealed thatresults similar to pure Ag can beachieved with G content up to 10vol%.Possible mechanisms, which maycontribute to this tribologicalbehavior are the Ag-C interactions andthe lubricating nature of graphene.Friction tests with G and GOcontaining lubricating greases showinconsistent results, and both greasesand corresponding test methods forevaluation require furtheroptimization. The overall, promising,tribological behavior of G and GOholds for the implementation invarious industrial applications. Thereis no doubt that these kinds ofmaterials can play an important rolein ABBs future work. This masterthesis report shows yet anotherapplication area for theseextraordinary materials.

Solid oxide fuel cells (SOFCs) are considered as one of the most promising power generation technologies due to their high energy conversion efficiency, fuel flexibility and reduced pollution. There is a broad interest in reducing the operating temperature of SOFCs. The key issue to develop low-temperature (300~600 °C) SOFCs (LTSOFCs) is to explore new electrolyte materials. Recently, ceria-based composite electrolytes have been developed as capable alternative electrolyte for LTSOFCs. The ceria-based composite electrolyte has displayed high ionic conductivity and excellent fuel cell performance below 600 °C, which has opened up a new horizon in the LTSOFCs field. In this thesis, we are aiming at exploring nanostructured composite materials for LTSOFCs with superior properties, investigating the detailed conduction mechanism for their enhanced ionic conductivity, and extending more suitable composite system and nanostructure materials.In the first part, core-shell samarium doped ceria-carbonate nanocomposite (SDC/Na2CO3) was synthesized for the first time. The core-shell nanocomposite was composed of SDC particles smaller than 100 nm coated with amorphous Na2CO3 shell. The nanocomposite has been applied in LTSOFCs with excellent performance. A freeze dry method was used to prepare the SDC/Na2CO3 nanocomposites, aiming to further enhance its phase homogeneity. The ionic conduction behavior of the SDC/Na2CO3 nanocomposite has been studied. The results indicated that H+ conductivity in the nanocomposite is predominant over O2- conductivity with 1-2 orders of magnitude in the temperature range of 200-600 °C, indicating the proton conduction in the nanocomposite mainly accounts for the enhanced total ionic conductivity. The influence of Na2CO3 content to the proton and oxygen ion conductivity in the nanocomposite was studied as well.In the second part, both the proton and oxygen ion conduction mechanisms have been studied. It is suggested that the interface in the nanocomposite electrolyte supplies high conductive path for the proton, while oxygen ions are probably transported by the SDC grain interiors. An empirical “Swing Model” has been proposed as a possible mechanism of superior proton conduction, while oxygen ion conduction is attributed to oxygen vacancies through SDC grain in nanocomposite electrolyte.In the final part, a novel concept of non-ceria-salt-composites electrolyte, LiAlO2-carbonate composite electrolyte, has been investigated for LTSOFCs. The LiAlO2-carbonate electrolyte exhibits good conductivity and excellent fuel cell performances below 650 °C. The work not only developed a more stable composite material, but also strongly demonstrated that the high ionic conductivity is mainly related to interface effect between oxide and carbonate. As a potential candidate for nanocomposite, uniform quasi-octahedral CeO2 mesocrystals was synthesized in this thesis work as well. The CeO2 mesocrystals shows excellent thermal stability, and display potential for fuel cell applications.

QC 20120529

Trois types des ETLs ont été développés et étudiés dans cette travaille comme une photoélectrode dans la cellule solaire à colorant (DSSC). Ils sont composés de (1) deux types de nanoparticules de TiO2-brookite, (2) le composite d'anatase et graphène et (3) la nanoparticule de ZnO qui a nanobâtonnet structure, respectivement. Toutes photoélectrodes sont préparées par le technique « doctor blade ». La morphologie des photoélectrodes ont été caractérisées par microscopie électronique à transmission (MET) et microscopie électronique à balayage (MEB). Les épaisseurs de couche sont mesurées en utilisant la profilométrie. Pour les films caractérisations structurelles, une haute résolution diffractomètre à rayons X a été utilisée. La spectroscopie infrarouge à transformée de Fourier (FTIR) et micro-Raman ont été effectués pour vérifier la préparation composite TiO2_Gr. Les propriétés des films optiques ont été enregistrées avec un spectrophotomètre équipé d'une sphère d'intégration de techniques. Les performances de cellules ont été obtenues en mesurant les courbes IV des cellules sous illumination calibré. Pour atteindre une compréhension profonde du fonctionnement de la cellule, la spectroscopie d'impédance (IS) technique a été étudiée sur une grande gamme de potentiel appliquée. En faisant est l'étude, la structure électronique, porteurs de charge à vie (tn), le transport / heure de collecte (ttr) et les paramètres de transport d'électrons des couches ont été déterminées. L'étude soin de leurs propriétés a révélé non seulement leurs avantages mais aussi leur limitation. Cette information sera bénéfique comme une considération pour les travaux futurs
Three kinds of ETL have been developed and studied in this present work as a photoelectrode in DSSC. Those composed of (1) two kinds of TiO2-brookite nanoparticles, (TiO2_B1 and TiO2_B2), (2) the composite of anatase and graphene (TiO2_Gr) and (3) the nanorods like ZnO nanoparticles (ZnO_NR), respectively. All photoelectrode are prepared by doctor blading technique. The morphology of photoelectrodes have been characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The layer thicknesses were measured using profilometry. For the film structural characterizations, a high-resolution X-ray diffractometer was used. The Fourier transform infrared (FTIR) and micro Raman measurement have been carried out to verify the TiO2_Gr composite preparation. The optical film properties (total transmission and total reflection) were recorded with a spectrophotometer equipped with an integrating sphere techniques. The cell performances were obtained by measuring the I-V curves of the cells under calibrated illumination. To achieve an in-deep understanding of the cell functioning, the impedance spectroscopy (IS) technique has been studied over a large applied potential range. By doing IS study, the electronic structure, charge carrier lifetime (tn), transport/collection time (ttr) and electron transport parameters of the layers have been determined. The carefully study of their properties has revealed not only their advantages but also their limitation. This information will be beneficial as a consideration for the future work

Small drinking water systems, often financially and resource-limited, face unprecedented challenges due to the current diversity and ubiquity of water pollutants. Well-characterized inorganic legacy pollutants, including arsenic, copper, hexavalent chromium, and lead, remain persistent in drinking water systems. In addition, emerging organic contaminants, like endocrine disrupting compounds and pharmaceuticals, are largely uncharacterized but prevalent in the environment and water supplies, calling into question what levels of these relatively new contaminants are truly safe in drinking water. Point-of-use (POU) and point-of-entry (POE) water treatment devices, installed at a specific tap or at the water entry point to a single facility, respectively, are necessary to ensure safe drinking water in contexts where centralized water treatment is not available or cannot adapt to meet new regulatory standards. While existing POU and POE technologies, including reverse osmosis and packed bed media filters, are effective for removing contaminants, installation costs, energy demands, and spatial footprints of these systems can inhibit their implementation. There is a need for new POU and POE technologies that remove a diversity of water contaminants while maintaining a small application footprint. Nanotechnology, referring to technology using material with at least one dimension or feature less than 100 nm in length, is ideal for meeting this need in drinking water treatment. With high surface area-to-volume ratios, nano-enabled treatment technologies exhibit enhanced reactivity with less material, keeping overall footprint relatively small. Specifically, electrospinning, a process in which a polymer precursor solution is electrified to produce a cohesive sheet of nanofibers, can be used to easily synthesize chemically active nanofiber filters for water treatment applications. In this study, we develop electrospun nanofiber filters that harness nano-scaled hematite (Fe2O3) for sorption of inorganic contaminants (e.g., As, Pb) and nano-scaled titanium dioxide (TiO2) for use with ultraviolet (UV) and visible light as an advanced oxidation process (AOP) for removal of emerging organic contaminants (e.g., benzotriazole, carbamazepine, DEET). Most importantly, we strive to optimize both reactivity and material strength to develop cohesive, durable filtration platforms that overcome barriers to use of nanomaterials in water treatment (e.g., concerns over leaching of nanoparticles deployed as suspensions). Herein, we first demonstrate reactivity optimization of pure (though brittle) TiO2 nanofiber photocatalysts by noble metal catalyst (Au) surface loading. Additionally, we optimize polymer-Fe2O3 composite nanofibers for reactivity while maintaining material flexibility by coating the doped polymer with additional Fe2O3 surfaces available for metal/metalloid uptake. Finally, we apply reactivity optimization and strategies to maintain material strength in the development of carbon/TiO2 nanofiber composites used for (photo)chemical filtration of water containing emerging organic contaminants. Ultimately, we find that nanofiber composites exhibit substantial reactivity and structural integrity in water treatment platforms. Outcomes of this work contribute to making nanomaterials, which have been studied for decades but have yet to be commercially employed for water treatment, practical for chemically active water filtration.

碩士
國立成功大學
材料科學及工程學系碩博士班
94
Increasing the interface area between Ni/YSZ (anode) and YSZ (electrolyte) is an effective way to enhance the performance of solid oxide fuel cells. Patterning on the surface of NiO/YSZ was proposed as a novel method to increase the surface area of NiO/YSZ. Patterned PDMS mold was first fabricated by replicating various SU8 patterns on Si wafers from photo-lithography technique. Patterned NiO-YSZ substrate was obtained after fabricating NiO-YSZ green tape from the PDMS mold. The pattern transfer of PDMS mold from SU8 patterns was successful. A fracture-free pattern with the maximum aspect ratio of 2.77 was obtained. However, after pattern transferring from PDMS mold, the patterns with aspect of 1.57 were significantly distorted. The patterns with aspect ratio of 2.19 were mostly damaged. These deformed and incomplete patterns were mainly caused by the friction between PDMS mold and ceramic green body during the mold releasing process. When the aspect ratio of the pattern reduced to below 0.91, patterns of PDMS could be completely transferred to the surface of NiO/YSZ. After firing at 1200℃, the shape of patterns on NiO/YSZ surface remained unchanged. Compared to the flat surface of un-patterned NiO/YSZ, 146％ increased surface area was observed in the patterns with aspect ratio of 1.57. Furthermore, a 17μm thick dense YSZ film was deposited on these patterned NiO/YSZ surface. A well-adhered YSZ film without any de-lamination was observed. In order to reduce NiO/YSZ to Ni/YSZ cermet, patterned NiO/YSZ samples were exposed to H2 at 800℃. Finally, desired electrolyte/electrode interface with a dense YSZ film covered on a patterned Ni/YSZ anode was obtained. It’s expected that the performance of SOFC would be enhanced when such a patterned structure is applied.

碩士
國立臺北科技大學
資源工程研究所
105
Due to the large specific surface area, high conductivity and good chemical stability, Reduced Graphene Oxide(rGO) has been widely applied in various fields. NiO material has similar characteristics with RuO2. Due to the low price, NiO can be produced in large-scale production. Recently, the NiO capacitor has found practical application in life. In this study, the linear NiO/rGO is synthesized by hydrothermal method to form an anode material with superior properties. There are three parts in the thesis: (1) the effect of preparation parameters on the structure and morphology of oxidized graphene and NiC2O4 Precursor, (2) the effects of amount of GO and Ni(NO3)2 on rGO/NiO Composites, (3) the application of rGO / NiO electrode. In this study, rGO / NiO composite is prepared by hydrothermal method with NiC2O4 as precursor. PEG is used as a molecular template to ensure the formation of NiO with a linear morphology. The average length and average width of NiO in the rGO/NiO composite were observed by SEM. The crystal phase of rGO/NiO composites was observed by XRD. FTIR observed effect of reduction on rGO formation. The electric performance of rGO/NiO composites is investigated by cyclic voltammetry. The experimental results indicate that linear NiO can improve the capacitance of rGO / NiO composite. With initial concentration of Ni(NO3)2 of 0.418M, calcination temperature of 300 ℃, the rGO / NiO composite material can have good stability, and charge and charge-discharge efficiency. The specific capacitance value can reach 177.7F/g

碩士
國立臺灣科技大學
光電工程研究所
101
The purpose of this research is to combine the titanium oxide material with tungsten oxide material, and we analyze its characteristic of electrochromism and photocatalysis. In this work, the tungsten films were deposited on ITO substrate and prepared in reactive DC magnetron sputtering system. The as-deposited samples were subsequently subjected to thermal annealing in quartz tube furnace with a 2-step heat treatment. The tungsten oxide nanowires were synthesized self-catalytically on ITO substrate. Then the titanium films were deposited on the tungsten oxide nanowires. After that the as-deposited samples were subsequently subjected to thermal annealing in quartz tube furnace with a 2-step heat treatment. The TiO2/WO3 core-shell structure was synthesized finally. The electrochemical analysis shows the TiO2/WO3 core-shell structure have a high diffusion coefficient (8.6×10-10 cm2/s), fast electrochromic response time (coloration time 2.9s, bleaching time 0.8s), tremendous transmittance difference (36.57%), and beneficial ability of photodegradation. Furthermore, the tungsten films were deposited on ITO substrate and prepared in reactive DC magnetron sputtering system. Then the titanium films were deposited on the as-deposited samples. The TiO2/WO3 composite structure was finally synthesized by annealing the Ti/W films. The electrochemical analysis shows the TiO2/WO3 composite structure have a high diffusion coefficient (1.8×10-9 cm2/s), fast electrochromic response time (coloration time 5.1s, bleaching time 2.6s), tremendous transmittance difference (48.5%), and beneficial ability of photodegradation. . Therefore, the electrochromic device with the combination of titanium oxide and tungsten oxide will be suit for the development of energy-saving smart windows.

碩士
中原大學
化學工程研究所
102
To the best of our knowledge, there are two methods to increase ionic conductivity of solid oxide fuel cells ( SOFCs ) electrolyte. One is the decrease in the thickness of electrolyte and the other is the electrolyte is doped by foreign materials. In this work, indium oxide (In2O3) is doped into electrolyte to improve the ionic conductivity of electrolyte. Yttria-stabilized zirconia(YSZ) and indium hydroxide (In(OH)3) are synthesized by hydrothermal method. The YSZ powder is about 90 nm. Various In(OH)3 morphology can be controlled by different concentration of InCl3. In2O3 is obtained after the calcination of In(OH)3 at 500℃. The In2O3/YSZ film is obtained by doping different In2O3 structures into YSZ films. The electrolyte of doped various In2O3 structures, nanoparticle (NP), nano/micro cube (NMC), micro cube (MC) are discussed at first, so the ratio of doped In2O3 is fixed at XIn2O3=0.06, about 12.7 w%. In2O3 NP /YSZ films have better ionic conductivity than In2O3 MC/YSZ films and In2O3 NMC /YSZ at 900℃. Then ratio of doped In2O3 are changed to find better ionic conductivity and In2O3 structures is fixed In2O3 NP to dope into films. The value of ratio are XIn2O3=0.01, about 2.3w%、XIn2O3=0.005, about 1.1w%、XIn2O3=0.001, about 0.2w%. In2O3 NP /YSZ films with XIn2O3=0.005 have better ionic conductivity (0.084Ω-1 cm-1)than other ratio at 900℃. In reference, ZnO and MgO have been doped into YSZ, their values are 0.029 and 0.035Ω-1 cm-1 at 800℃. In2O3/YSZ films with XIn2O3=0.005 are their values 1.7 times and 1.4 times.

碩士
國立勤益科技大學
化工與材料工程系
107
Supercapacitors is energy storage components that have emerged in recent years, it have higher power density than chemical batteries, and energy density are superior to capacitor , it also have fast charge and discharge, and longer cycle life. It can be used in various fields, such as electronic equipment, backup energy, hybrid vehicle energy, etc. In addition to the physical adsorption/desorption of the electrolyte ions of a typical electric double-layer capacitor, the large capacitance provided by the Faraday redox reaction of the metal oxide on the surface of the material in the pseudo-capacitor also Very popular. There are many differences about the type of the supercapacitor, such as the most primitive symmetric supercapacitors, asymmetric supercapacitors that increase energy density, flexible capacitors designed to develop wearable products, and solid electrolyte supercapacitors with better safety. In the past studies, common electrode active materials include activated carbon and mesoporous carbon , which having a large specific surface area. On the other hand , graphene and carbon nanotubes research have risen in recent years. Among them, graphene has excellent electrical conductivity, Thermal conductivity, large specific surface area and excellent mechanical properties. However, due to the graphene will restore back to graphite and loses advantage of large specific surface area. Therefore, find the material doping to block graphene self-stacking has become a hot topic in recent years. On the other hand , in order to improve the energy density, researchers usually use transition metal oxides, due to its high theoretical capacitance, easy to manufacture, a variety of appearances and low cost.Common metal oxides such as Co3O4 and Mn3O4. However, the poor conductivity of metal oxides, low cycle stability, and high resistance of components are still one of the focuses of researchers. In this study, we added Graphene, CNT and Co3O4 precursors in the electrophoresis batch replication process, and created the electrode material with multi-porosity structure by using the interlayer to create the spatial effect, which greatly increased the application potential of the electrophoretic coating method. Further, MnO2 was added to the process to increase the Faraday capacitance. The results show that the study successfully obtained the EPD coating with hole type and effectively improved the power density; the excellent quality transmission structure enables the performance of the pseudo capacitor to be exerted.

Copper oxide and graphene oxide composite have been prepared successfully. The prepared composite have been characterized by XRD, SEM and UV-Vis. Band gap calculation using formula Eg= hʋ from UV-Vis shows a decrease in band gap. The electrical transport is also expected to increase but yet to be analysed.

This research study describes the gas separation performance of different sets of Polyethyleneoxide-block-Polysulfone-block-Polyethyleneoxide/poly(ether-block-amide) (PEO-b-PSU-b-PEO/Pebax) composite membranes for CO2 separation from N2 and CH4. Gas permeation properties of the membranes prepared were studied at ambient temperature (21oC) and 8bar. The dependence of gas flux and selectivity on pressure was explored for different pressures from 2.5 bar up to 19 bar also at ambient temperature. Pebax/PAN composite membranes have a range of CO2 permeance of 4467±274 GPU, 365±64 GPU for CH4 and 152±17 GPU for N2 with CO2/N2 and CO2/CH4selectivities ranges of 30 and 13 respectively. Improved CO2/N2 and CO2/CH4 selectivities coupled with flux reduction were obtained from the introduction of PEO-b-PSU-b-PEO films on Pebax/PAN composite membranes. The gas flux reduced to about one-tenth of Pebax/PAN membrane’s while the selectivities obtained for all the PEO-b-PSU-b- PEO/Pebax/PAN membrane range from 33 to 60 for CO2/N2 and 17 to 33 for CO2/CH4 as the thickness of PEO-b-PSU-b-PEO top layer increases.

碩士
國立成功大學
奈米積體電路工程碩士學位學程
104
In this study, the high performances room temperature nitrogen dioxide (NO2) gas sensors were fabricated using zinc oxide-reduced graphene oxide (ZnO-rGO) composite films as sensing materials. The ZnO-rGO composite films were synthesized by annealing the zinc oxide-graphene oxide (ZnO-GO) composite films in Ar flow at 300℃ for 1 h which were prepared by spin-coating. Moreover, the ZnO-rGO composite films possessed several advantages, including easy fabrication and low cost. By varying the doping amount of ZnO, the response of gas sensors would be enhanced. According to the experimental results, the gas sensors using ZnO-rGO composite films which the weight ratio (ZnO/GO) was 0.08 as sensing materials exhibited the better NO2 sensing response at room temperature. The ZnO-rGO gas sensors (ZnO/GO=0.08) exhibited the sensing response of 45% under 100 ppm NO2 gas. Moreover, the ZnO-rGO gas sensors (ZnO/GO=0.08) which annealed in Ar flow at 300℃ for 2 h and 3 h possessed the gas response of 48% and 42% under 100 ppm NO2. The performances of the ZnO-rGO gas sensors (ZnO/GO=0.08) sensing different concentration of NO2 at room temperature not only had good linearly curve but also exhibited other advantages such as good response time, recovery time, and selectivity.

碩士
逢甲大學
材料科學所
100
In the present study, bismuth oxide (Bi2O3) powders were prepared from bismuth nitrate (BiNH) by spray pyrolysis (SP) and hydrothermal (HT) processes. The influences of both processes on the characteristics and photoreactive behaviors of the resulting powders were investigated. Subsequently the Bi2O3 powder was doped with various amounts (0, 5, 10 and 20 at%) of zinc (Zn) to modify its characteristics, photoreactive and catalytic properties. The powders were then deposited onto a diffusor of UV-LED (ultraviolet light-emitting diode) to inhibit the UV light emitted from the LED. The UV light inhibition, color rendering index and transmittance as well as the degradation of air pollution of the powders were discussed. The experimental results indicated that the SP-derived Bi2O3 powder possessed smaller particle size, lower cost and better photoractive and UV-resistance properties comparing to the HT-derived powder. The microstructural observation suggested that the SP Bi2O3 particles exhibited solid, hollow and bowl-like structures no matter Zn was doped or not. Furthermore, small amounts of Zn addition may cause the increase in crystallite size of Bi2O3. When the addition excesses a certain value, the immiscible secondary phase may precipitate to inhibit the grain growth of Bi2O3, causing the increase in specific surface area of the Bi2O3 with increasing the Zn addition. Zn addition can enhance the photoreactive performance of the Bi2O3 powder. No obvious influence on the catalytic properties of Bi2O3 can be found from the evaluations of lattice parameter, crystallite size and surface area when Zn was doped. The SP powders were then mixed with optical paste and screen-printed onto the diffusor of UV-LED for evaluation of UV inhibition. The UV inhibition of the undoped SP Bi2O3 powder was increased and then saturated gradually with the increase of Bi2O3 solid content. The Bi2O3 powder pyrolyzed at 600 and 700°C (denoted as SP600 and SP700 powders) exhibited better UV inhibition efficiencies of 70% and 89%, respectively, in this system. The UV inhibitions of SP600 powder were 70%, 68%, 72% and 72% when Zn additions were 0, 5, 10 and 20 at%, respectively. Whereas, the UV inhibitions of SP700 powder were 89%, 65%, 69% and 73% when Zn additions were 0, 5, 10 and 20 at%, respectively.

碩士
國立清華大學
化學工程學系
98
Manganese oxide aerogels were successfully synthesized with an epoxide addition procedure by using MnCl2‧4H2O as the precursor. The as-prepared aerogels possessed the crystalline phase of hausmannite of Mn3O4 and a BET specific surface area of 79m2/g. After heat treatment at 300 oC, the aerogels gave specific capacitances (SC) of up to 122F/g in 0.5M Na2SO4 solution, at a scan rate of 25mV/s, and within the window of 0.1~0.9V vs. Ag/AgCl. The resulting cyclic voltammetry (CV) loops appeared rectangular, implying high reversibility. After 2000 cycles of CV scans, the aerogels showed excellent cycle stability, retaining at least 96% of the maximum SC value. In order to improve on the issue of low electrical conductivity of manganese oxides, tin oxide aerogels (317m2/g) and carbon aerogels (577m2/g) of high specific surface areas and better electrical conductivities were used as the porous template to accommodate the functioning manganese oxides. Manganese oxides were electrodeposited into the aerogel templates with a simple 2-electrode potentiostatic procedure operated at different potentials. These composite electrodes, possessing high electrical conductivity backbone and rich redox reactions of transition metal oxides were found promising for supercapacitors. The SC of the manganese oxide (deposited at 2V)/tin oxide aerogel composite electrode was 253F/g, a significant enhancement over that of the plain manganese oxide aerogel, mainly because of the enlarged specific surface area provided by the tin oxide aerogel template. To seek further improvement, carbon aerogels of high conductivity (0.00148Ω/□) and high surface area were used as the template for manganese oxides. The SC value of this MnOx/CA, with MnOx deposited at 1.5 V, was as high as 503F/g, and retained 99% of the maximum SC value after 6000 cycles of CV scans, indicating the further boost in SC and excellent cycle stability. The SC value of this composite electrode remained high at 243F/g even at a very high scan rate of 500mV/s, retaining 62.8% of the SC values obtained at a scan rate of 25mV/s, and achieving a high specific energy density of 21.6Wh/kg and a high specific power density of 48.5kW/kg. This work demonstrates the advantages of using composite electrodes for the next-generation supercapacitors.

碩士
國防大學理工學院
應用化學碩士班
97
A nickel-lanthanum composite oxide, U-LaNiOx, with 1:1 molar ratio was prepared by the co-precipitation-oxidation method (PO) and assisted with ultrasonic irradiation (240 W). The as-prepared sample was further calcined at 300, 500 and 700 ℃ for 2 h (assigned as U-C300, U-C500 and U-C700, respectively). All samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET and temperature programmed reduction (TPR). Catalytic activities toward the steam reforming of ethanol (SRE) were tested in the temperature (300-450℃) in a self-designed fixed-bed reactor.The results of Characterization test confirmed that the U-LaNiOx has a nanotube structure and LaNiOx has a nanorods structure, We believe that formation of nanotubes can be attributed to the assisted with ultrasonic irradiation. Both as-prepared sample was calcined at 700 ℃ for 2 h that became perovskite structure (LaNiOx).This study focused on the comparison of activated as-prepared sample (U-LaNiOx) with the non-assisted with ultrasonic irradiation (240 W)as-prepared sample (LaNiOx). The results indicated that the ethanol conversion approached complete around 325 ℃ for U-LaNiOx sample while required 425 ℃ for LaNiOx sample to complete conversion. The yield of hydrogen (YH2) arrived 5.0 around 350 ℃ for U-LaNiOx sample.U-LaNiOx catalyst compared with LaNiOx catalyst, U-LaNiOx catalyst was highly active and stable for steam reforming of ethanol. The improvement was attributed to the effective highly dispersed LaOx particles through the strong interaction between LaOx and NiOx.

博士
國立清華大學
材料科學工程學系
104
A high-performance supercapacitor based on Ni(OH)2 nanoflakes modified ZnO nanowires (NWs) was developed. The well-aligned ZnO NWs were synthesized by chemical bath deposition, followed by pulse electrodeposition of Ni(OH)2 nanoflakes on the surface of ZnO NWs. The effects of the pulse electrodeposition conditions were systematically investigated. Both the current-on time and current-off time were found to affect the size and interspacing of the nanoflakes, while the deposition cycle number determines the thickness of the Ni(OH)2 nanoflake shell. The ZnO/Ni(OH)2 nanocomposite electrode fabricated under the optimal pulse electrodeposition conditions has exhibited a large specific capacitance of 1830 F/g, a high energy density of 51.5 Wh/kg, a high power density of 9 kW/kg, and ~80 % specific capacitance retention after 1000 cycles. To improve the specific capacitance retention, Mn precursor was added into the deposition solution. The optimal amount of Mn precursor and the pulse electrodeposition conditions were discussed. The resultant ZnO/(Ni, Mn) oxide or hydroxide nanocomposite electrode fabricated under the optimal conditions has exhibited a specific capacitance of 1642 F/g, an energy density of 42.2 Wh/kg, a power density of 9 kW/kg, and 94.7 % specific capacitance retention after 3000 cycles. The high supercapacitor performance combined with using of the low-cost and environmentally friendly materials will make the ZnO/(Ni, Mn) oxide or hydroxide nanocomposite electrode desirable for supercapacitor applications.

碩士
國立交通大學
材料科學與工程系所
97
A 35–300 nm amorphous ruthenium oxide and ruthenium composite film has been deposited by electroless plating on a Cu substrate. The plating solution contained compounds of K2RuCl5•xH2O, NaNO2, NaOH, and NaClO. Variables including different mixing steps, concentrations of NaNO2(aq), and plating time were investigated. The reaction steps for the electroless plating were indentified. Stability of the plating solution was confirmed by UV-Vis absorption spectra with narrow maximum wavelength distribution. EDX, SEM, AFM, XPS, and Raman spectroscopy were employed to characterize the as-deposited films. It was concluded that the plating solution with 0.06 M NaNO2(aq) delivered the desirable film qualities. A crystalline Ru film was obtained by H2 reduction for the as-deposited film at 200℃ for 2 hr. In addition, we were able to produce a crystalline RuO2 and Ru composite film by Ar annealing of the as-deposited film at 400℃ for 2 hr.

碩士
國立清華大學
化學工程學系
100
Tungsten trioxide, a low cost and an environmentally friendly supercapacitive material, is deposited as a thin nanostructure of nanocrystals into carbon aerogels, a mesoporous host template of high specific surface areas and high electric conductivities, with a wet chemistry process. This tungsten trioxide/carbon aerogel composite shows ultrahigh specific capacitances(tungsten trioxide based) of around 700 F/g at a scan rate of 25 mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. The composite also possesses an excellent high rate capability manifested by maintaining specific capacitances above 480 F/g at a high scan rate of 500 mV/s, and an outstanding cycling stability demonstrated by a negligible 5% decay in specific capacitances after 4000 cycles. The success is attributable to the fuller utilization of tungsten trioxide for supercapacitance generation, made possible by the composite structure enabling largely and well exposed tungsten trioxide to the electrolyte and easy transport of charge carriers, ions and electrons, within the composite electrode. Plain tungsten trioxide electrodes are also investigated. The as-prepared tungsten trioxide nanoparticles are synthesized with a sol-gel process, followed by calcination at 400 oC. The specific capacitances of plain tungsten trioxide electrodes are 53.7F/g at a scan rate of 25mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. When the scan rate is increased to 500mV/s, the specific capacitances of the plain tungsten trioxide electrode decrease by 60%. Symmetric capacitors composed of two tungsten trioxide/carbon aerogel composite electrodes are studied. The specific energy and specific power of this device equal 2Wh/kg and 6.2kW/kg, respectively. The products have been characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),X-ray spectroscopy (XPS), wide angle X-ray scattering (WAXS), surface area and pore size analyses (BET), and cyclic voltammetry (CV).

碩士
逢甲大學
材料科學所
100
Abstract In this study, the sol-gel method was used to prepare ZnO / carbonfelt (ZnO/C) composite photocatalyst material. The process impregnated carbonfelt in zinc acetate sol-gel solution at different concentration (0.1 M, 0.01 M, 0.001 M). Then dried in oven 24 hr at 70oC, and then heated at different temperature (200oC, 300oC, 400oC) fot 1 to 30min. The zinc ions would reduced to zinc oxide particles in carbonfelt fiber surface after heated. The carbon composite zinc oxide felt would been test by photodegradation experiment. In this experiment, methylene blue was simulation as the default pollutants. The result will show carbon composite zinc oxide felt''s performance in photodegradation. The ZnO particle''s dispersion and surface morphology in carbonfelt been observed by field emission scanning electron microscopy (FESEM). And used X-ray scattering techniques (XRD), energy dispersive spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) to obtain ZnO crystal structure, weight percent and chemical composition. Used inductively coupled plasma spectrometers (ICP) to quantify the concentration of zinc ion of zinc oxide in carbonfelt. Photoluminescence (PL) would determination of photocatalytic performance and the specific surface area of carbonfelt and ZnO/C will measure by surface area and porosity analyzer to observe the surface area and photocatalytic properties. Finally, degradation of methylene blue to verify the photocatalyst performance of the carbon composite zinc oxide felt with ultraviolet light. The experimental results showed that 0.1 M carbon fiber composite zinc oxide felt heat 200 oC''s specific surface area4.17 m2 / g was 417 times then carbonfelt 0.01 m2 / g. But heat to 300 oC and 400 oC have small surface area decreased to 2.05 m2 / g and 1.47 m2 / g. Photodegradation experiments test was used methylene blue (10 ppm) and placed test sample size 25 cm2 in photodegradation reactor, then irradiation by 100W UV light for 30 minutes. Result show 0.1 M carbon composite zinc oxide felt to heat treatment of 200 °C have well photodegradation performance, the concentration of methylene blue from the original 100 % to 5 %, have the best photodegradation efficiency of 95 %. This study found that carbonfelt coated with zinc oxide material''s photo- degradation performance was proportional to it''s specific surface area value. The carbon fiber mat impregnated with 0.1 M oxidation of zinc by the sol-gel solution, and after heat treatment 200 oC, have the well degradation efficiency of methylene blue. Key word : carbon fiber、ZnO、photocatalyst、methylene blue.

碩士
國立臺灣科技大學
電子工程系
107
In this study, we report UV photodetectors (PDs) based on the combination of ZnO nanorods (ZNR), reduced graphene oxide (rGO) and nickel oxide (NiO) via a simple solution process. More briefly, we divide this study into four parts. The first part is about ZNR growth using different seed layer spin speed based UV PDs. The second part comprises the UV PDs based on rGO-ZNR with different seed layer spin speed and the third part explains UV PDs based on NiO-ZNR with different seed layer spin speed. The fourth part describes the UV PDs with the combinations of NiO-rGO-ZNR. From the overall studies, it was revealed that the as-prepared NiO-rGO-ZNR based PDs exhibit highly enhanced switch (IPhoto/IDark) ratio of 31,116.6 compared to those of NiO-ZNR (5776.02), rGO-ZNR (1880.73) and ZNR (517.95) based PDs. In addition, photo-responsivity (R), quantum efficiency (Q.E) and UV/Visible rejection ratio were also calculated using the responsivity vs wavelength curves. Obviously, the NiO-rGO-ZNR PDs shows the enhanced R (0.072 A/W), Q.E (24.38 %) and UV/Vis rejection ratio (4.49) compared to those of other PDs.

博士
國立臺北科技大學
材料科學與工程研究所
103
There are two different approaches in this thesis. One approach is to synthesize spinel-type oxides as a precursor preparing Cu or Ni catalysts for steam reforming of methanol (SRM). The other approach focuses on preparation of Au or Pt catalysts from intemetallic compounds or amorphous alloys to perform CO oxidation reaction. These approaches in terms of the ellingham diagram which is usually used to evaluate the ease of reduction of metal oxides or oxidation of metal. Firstly, various Cu-based spinel compounds, i.e., CuFe2O4, CuMn2O4, CuAl2O4 and CuLa2O4 were fabricated by a solid-state reaction method. H2-TPR results indicated that reducibility of Cu-based spinel compounds was strongly dependent on the B-site component where the CuFe2O4 catalyst revealed the lowest reduction temperature (190°C), followed by CuAl2O4 (267°C), CuMn2O4 (270°C) and CuLa2O4 (326°C). The reduced CuAl2O4 catalyst revealed the best performance in terms of catalytic activity. Based on the SEM and XRD results, pulverization of the CuAl2O4 particles due to gas evolution and a high density of nanosized Cu particles (50.9 nm) precipitated on the surfaces of the Al2O3 support were observed after reduction at 360°C in H2. Reduction of Cu-based spinel compounds appear to be a potential synthesis route for preparing a catalyst with high catalytic activity and thermal stability. The catalytic performance of these copper-oxides composites was superior to those of conventional copper catalysts. Secondly, Fe3O4-supported Cu and Ni catalysts are prepared through reduction of Cu-Ni (Ni1-xCuxFe2O4) ferrites. All ferrites are characterized with granular morphology and a smooth particle surface before reduction. Reduction temperature for the CuFe2O4, Ni0.5Cu0.5Fe2O4 and NiFe2O4 ferrites were 240, 300, and 400°C, respectively, in which nanosized Cu and/or Ni particles (5-32 nm) and mesopores (5-30 nm) are distributed and adhered on the surfaces of Fe3O4 supports. After the reduction treatment at temperature higher than 500°C for NiFe2O4 ferrite, the Ni particles and mesopores disappear from the Fe3O4 surfaces, which is due to the formation of a Fe-Ni alloy covered on the Fe3O4 surfaces. The CuFe2O4 ferrite after H2 reduction at 240°C exhibits the highest activity quoted with H2 production rate of 149 ml STP/min．g-cat at 360°C. The existence of Ni in the Cu-Ni ferrites enhances the reverse water gas shift reaction, raises the CO selectivity and reduces the CO2 selectivity. Formation of the Fe-Ni alloy exaggerates the trend and poisons the H2 production rate. Finally, in order to develop a process for preparation of a new form of catalyst where Au, Pt fine particles supported on metal oxides (ZrO2, Fe2O3), Au or Pt–contained Zr2Fe-based intermetallic compounds and amorphous alloys were used as precursors for oxidation treatment. The catalytic properties of Au, Pt/metal oxides catalysts prepared by crystallization or oxidation have been investigated with CO oxidation reaction (CO+1/2O2→CO2). Zr67Fe33, Zr67Fe30Au3 and Zr67Fe30Pt3 alloys were prepared by arc-melting in Ar atmosphere. Amorphous phase was further fabricated by single-roller melt spinning in an Ar atmosphere. The catalysts were obtained by annealing amorphous ribbons at elevated temperatures. After the oxidation process, metal-oxide composite catalysts of Au, Pt/ZrO2-Fe2O3 were obtained. The changes in the intermetallic compounds and amorphous alloy ribbons before and after the oxidation treatment were analyzed, and the effects of the oxidation features and mechanisms on the catalytic activity of the catalyst was investigated. On the other hand, the metal/oxide complex catalyst (Au, Pt/CeO2-NiO) was successfully synthesized using the cerium-based intermetallic compound Ce50Ni50 as a precursor and replacing Ni with a small quantity of Au or Pt. The catalytic properties of CeO2-NiO supported Au and Pt catalysts for the CO oxidation reaction were investigated. The catalysts were obtained by oxidation treatment at elevated temperatures. The cerium metal in the intermetallic compound was easily oxidized to CeO2 during the oxidation process, in which Au or Pt particles precipitated on the surface and promoted the overall catalytic activity. This was especially clear when intermetallic Ce50Ni45Au5 was tested in the reaction bed directly; Au and Ni particles precipitated to the surface of the CeO2 support and were evenly distributed after five cycles of a heating and cooling test.

碩士
國立成功大學
化學工程學系
107
Abstract This thesis concerns the preparation and catalytic application of cobalt tungstate/cesium tungsten oxide (CoWO4/CsxWO3-H) composite nanoparticles, which could be synthesized successfully via two-step solvothermal process and the followed calcination in H2/Ar (5/95) atmosphere at 600oC. Because they possessed the excellent NIR photothermal conversion property of cesium tungsten oxide and the catalytic properties of cobalt tungstate, the resulting CoWO4/CsxWO3-H composite nanoparticles were utilized as the catalyst with near-infrared (NIR) and sunlight photothermally enhanced performance for the catalytic reduction of 4-nitrophenol (4-NP) with sodium borohydride in this study. From the investigations on the effects of 4-NP concentration, catalyst amount, and reaction temperature, it was found that the corresponding pseudo-first-order rate constant increased with the increase of temperature and catalyst amount while decreased as the concentration of 4-NP increased. This revealed that the reaction had an activation energy of 23.9 kJ/mol and was diffusion-controlled. Furthermore, under NIR or sunlight irradiation, the reaction rate could be enhanced significantly owing to the increase of solution temperature. This revealed that the resulting catalyst possessed good photothermal conversion capability and its performance could be enhanced by the irradiation of sunlight. It was demonstrated to have great potential in practical application.