Дисертації з теми "Solution Combustion Synthesi"

Este trabalho teve por objetivo investigar a obtenção de espinélio MgAl2O4 nanoestruturado através da síntese contínua por combustão em solução e sua caracterização por diferentes técnicas. Incluso neste estudo a influência do tipo de combustível e a razão combustível-oxidante no tamanho do cristalito. As partículas de espinélio MgAl2O4 foram sintetizadas utilizando-se os precursores químicos nitrato de alumínio e nitrato de magnésio como fonte dos cátions metálicos. Uréia, glicina e sacarose foram empregadas como agentes redutores, com diferentes valores da razão combustível-oxidante para a sacarose. Estes parâmetros foram relacionados com sua influência no tamanho de cristalito, tamanho de partícula e área superficial. Na caracterização do pó obtido, foram utilizadas técnicas como análise termodiferencial (ATD) e termogravimétrica (ATG), granulometria por difração de laser (GDL), análise de área superficial (BET), análise cristalográfica por difração de raios X (DRX), morfologia por microscopia eletrônica de varredura (MEV). As reações químicas da síntese contínua por combustão em solução resultaram na formação in situ de fases cristalinas para reações estequiométricas de uréia, glicina e sacarose e as deficientes de sacarose. Preponderância de fase amorfa ocorreu nas reações com excesso de sacarose para o pó como-sintetizado. A totalidade de fase cristalina foi obtida após um tratamento térmico a 900°C do pó como-sintetizado. Os pós de espinélio MgAl2O4 obtidos apresentaram-se como constituídos de cristalitos nanométricos, dispostos na forma de agregados de tamanho micrométrico. O tamanho de cristalito médio, calculado pelo método Single Line, a partir de dados de análises por DRX, foi de 13 nm. A área superficial média dos pós calcinados medida pelo método BET foi de 54 g/m2 Por análise granulométrica constatou-se um Tamanho de partícula médio de 17 μm para o pó como-sintetizado e 17,1 μm para o calcinado a 900ºC. As análises por MEV confirmaram a agregação das partículas do pó sintetizado, a partir de partículas preponderantemente esféricas e algumas com morfologia irregular.
This study has investigated a continuous solution combustion synthesis technique to obtain the nanostructured MgAl2O4 spinel powder and their characterize them by different tecniques. This study has also included the investigation of the influence of different kinds of fuel and fuel-to-oxidant ratio on crystallite size. The MgAl2O4 spinel powder was performed using aluminum nitrate and magnesium nitrate to obtain the metallic ions. Urea, glycine and sucrose were used like fuel, with several fuel-to-oxidant ratio. These parameters were correlating with powders characteristics, like crystallite size, particle size and superficial area. The techniques used for powder characterization included differential thermal analyzer (DTA), thermogravimetric analyzer (TGA), particles size analyzer (PSA), surface area by BET analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The chemical reactions of solution combustion resulted on crystalline phase to the reactions with urea, glycine and sucrose (to desabilites on fuel and stoichiometric) and amorphous phase formation of MgAl2O4 in situ for as-synthesized powder. The crystalline phase formation of spinel MgAl2O4 was only succeeded obtained after a thermal treatment of as-synthesized powder under 900°C.The spinel MgAl2O4 powders obtained were composed of nano-size crystallites, but in micrometer-sized aggregates. The mean particle size calculated, via Single Line method, using XRD was 13 nm. PSA indicated that the synthesized powders contain a mean aggregates size with a tri mode distribution of around 17.1 μm. SEM analyses confirmed that the as-synthesized powders are composed of particles aggregation. They have an irregular morphology and nano-size crystallites.

The main goal of this thesis work is the production and characterization of Tin oxide thin film deposited via Solution Combustion Synthesis (SCS). Different precursors are used in order to study the effect of the chemical nature of the reagent on the structural, morphological and electrical properties of the thin films. Tin oxide was chosen because is one of the most promising candidates for p-type oxide. In fact, the semiconductor oxides reported in the literature are mostly limited to n-type and there is a need for solution processed p-type oxide semiconductors to achieve Complementary Metal Oxide Semiconductors (CMOS) using all oxide materials. Anyway, the production window of solution processed for p-type SnO is narrow and Silver doping will be used to enhance the probability to get it. If production of p-type Tin oxide will not be achieved, the work will be focused on n-type SnO2 and on the optimisation of devices made with this material, either Thin Film Transistors (TFTs) or Transparent Conductive Oxides (TCOs). Samples made in this work show good optical properties, like transmittance over 80% and energy gap values around 3.79 eV, but none of them turned out to be a p-type oxide or a good TFT. Samples annealed at higher temperatures have good electrical conductivity properties, which could lead to a future study in order to optimise these materials for TCO purposes.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Visible light accounts for the biggest fraction of the solar irradiance. One of the strategies for achieving higher photovoltaic power conversion efficiency is the application of low band-gap materials (Eg ideal≈1.4 eV) capable of absorbing this fraction of the solar spectrum. Ferroelectric semiconductors have been studied in this field due to the above-bandgap generated photovoltages and their ferroelectric polarization-driven carrier separation. Ferroelectric oxides usually present wide bandgaps which allow the absorption of only 8-20% of the solar spectrum. However, the development of new ferroelectric materials, particularly KBNNO [KNbO3]0,9[BaNi0,5Nb0,5O3-δ ]0,1 (Eg = 1.39 eV) and KBiFe2O5 (Eg=1,60 eV), has encouraged the use of such materials in solar cells. Simple synthesis routes, with short steps, time and temperatures are essential for the future progress of the application of such ferroelectric oxides in solar cells. KBNNO and KBiFe2O5 require high crystallization temperatures, which reduce the number of potential substrates and electrode materials that could be used in devices, as polymer-based flexible ones. Obtaining this oxides in a high surface-area powder form might be a strategy to further incorporation in solar cells composed of low-temperature processing materials. This work reports for the first time synthesis of KBNNO and KBiFe2O5 by solution combustion (SCS). Characterization by WAXD, SEM, EDS, TG/DSC and Diffuse Reflectance UV-Vis Spectroscopy and dielectric constants indicates the success of the synthesis. The optical properties show the visible-light absorption contribution and band-gaps closer to the ideal magnitude for solar applications compared to the non doped materials. The SCS was shown as an effective route to obtaining the phase. Furthermore, it is possible to improve it in order to produce powders with smaller particle size and absent of secondary phases.
A luz visível representa a fração mais relevante da radiação solar. Desta maneira, busca-se empregar nas camadas ativas das células solares materiais com baixos band-gaps (Eg ideal ≈1,4 eV), capazes de absorver fótons nessa região do espectro. Semicondutores ferroelétricos com estrutura da perovskita ou estruturas relacionadas têm sido estudados nesse campo devido ao potencial de obtenção de voltagens superiores à magnitude de seus band-gaps e à contribuição na separação de portadores de cargas decorrente da polarização intrínseca presente nesses materiais. Óxidos ferroelétricos geralmente possuem Eg elevados (2,7-4 eV), permitindo o aproveitamento de somente 8-20% do espectro solar. No entanto, o desenvolvimento de novos semicondutores ferroelétricos, particularmente a KBNNO [KNbO3]0,9[BaNi0,5Nb0,5O3-δ ]0,1 (Eg=1,39 eV) e KBiFe2O5 (Eg=1,60 eV), tem encorajado a aplicação desses materiais em células solares. Rotas de síntese simples, com etapas, tempos e temperaturas reduzidas são essenciais para o progresso futuro da aplicação de tais óxidos ferroelétricos em células solares. A KBNNO e KBiFe2O5 cristalizam em temperaturas mais elevadas do que perovskitas orgânico-inorgânicas, o que reduz a possibilidade de fabricação de dispositivos na presença de substratos e eletrodos sensíveis à temperatura, como substratos poliméricos flexíveis. Assim, a obtenção desses óxidos na forma de pós de elevada área superficial pode ser uma estratégia para posterior incorporação em dispositivos contendo materiais processados a baixas temperaturas. Neste trabalho, reporta-se pela primeira vez a síntese da KBNNO e KBiFe2O5 por combustão em solução. Caracterizações por DRX, MEV, EDS, TG/DSC, Espectroscopia UV-Vis e constantes dielétricas indicam a obtenção das fases com sucesso. As propriedades ópticas confirmam contribuição na absorção da luz visível com respeito aos materiais não dopados, KNbO3 e BiFeO3. A síntese por combustão em solução se mostra efetiva para obtenção das fases, mas passível de melhorias para produção de pós com menor tamanho de partícula e sem a presença de fases secundárias.
CNPq: 155305/2014-0

Com o aumento do uso do método de síntese por combustão em solução para obtenção de pós cerâmicos, há uma crescente percepção da necessidade de se entender as características únicas deste processo. Esta tese apresenta uma investigação baseada na obtenção de diferentes pós nanoestruturados: Al2O3-α (alumina), Cr2O3 (crômia), Fe2O3-α (hematita), Fe3O4 (magnetita), NiO (bunsenita) e CoO, Co3O4 (óxidos de cobalto), como opção para futuras aplicações. Estes foram caracterizados via ATD, BET, DRX, MET, MEV, VSM, XPS e FTIR. O foco particular deste trabalho é o estudo da razão combustível-oxidante e sua influência nas características dos materiais resultantes. Outros parâmetros de combustão foram identificados e também devidamente avaliados, tais como: tipo de chama, temperatura, gases gerados e composição química dos reagentes precursores. O cálculo termodinâmico da reação de combustão em solução mostrou que, quando a razão combustível-oxidante aumenta, obtêm-se uma elevação da temperatura de chama adiabática e da quantidade de gás produzida, definindo características do particulado como morfologia, tamanho de cristalito, área superficial e nível de agregação. A formação dos óxidos e metais seguiu um comportamento termodinâmico esperado, conforme energia livre de Gibbs. Menores tamanhos de cristalito foram obtidos sempre na condição deficiente em combustível para todos os sistemas estudados. Já a temperatura foi o principal parâmetro de reação que governou a taxa de crescimento e concorreu com a geração de gases para a formação dos cristalitos em certas condições redutoras. Os resultados deste trabalho melhoraram significativamente o entendimento do efeito da razão combustível-oxidante no comportamento das características físicas dos pós. Esta correlação foi avaliada com intuito de fornecer base de conhecimento para possível aplicação desta tecnologia na otimização ou desenvolvimento de novos sistemas de pós.
With the increasing use of solution combustion synthesis method for powder obtaining, there is a growing realization of the need to understand the unique characteristics of this process. This thesis presents the novel investigation of this technique specifically based upon some nanostructured powders such as α - Al2O3 (alumina), Cr2O3 (eskolite), α - Fe2O3 (hematite), Fe3O4 (magnetite), NiO (bunsenite), and CoO, Co3O4 (cobalt oxides) as a core option for future applications. These were characterized via DTA, BET, XRD, TEM, SEM, VSM, XPS, and FTIR. The particular focus of this work is based on the study of the fuel-to-oxidant ratio influence to the characteristics of the resulting materials. Other combustion parameters were identified and also proper appraised as flame type, temperature, gas generation, and chemical composition of precursor reagents. The thermodynamic calculation of the combustion reaction shows that as fuel-tooxidant ratio increases the amount of gas produced, and adiabatic flame temperature also increases. Powder characteristics as morphology, crystallite size, surface area and aggregation degree are mainly governed by the flame temperature, and generation of gases. The oxide and metals formation followed a thermodynamic behavior as expected, conform to Gibbs free energy. Lower crystallite sizes were always obtained by fuel-lean condition for all studied systems. The temperature was the main reaction parameter controlling the growth rate, while it competed with generation of gases to form crystallites under certain reducing conditions. The outcomes of this work have significantly improved the understanding of the fuelto- oxidant ratio effects on the behavior of the physical characteristics of powders. This correlation has been drawn in order to provide a knowledge basis for possible application of this technology to optimize or develop new powder systems.

Le domaine de composition Ca(ZrxTi1-x)O3 a été étudié afin de mieux apprécier ses propriétés diélectriques ; dans le but d'applications pour condensateurs céramiques multicouches à armatures en métaux non nobles. La synthèse de tout ce domaine est mal connue, que ce soit par voie solide, ou par flash combustion. L’étude et l’optimisation (mélangeage/broyage, température de chamottage) de la synthèse par voie solide a permis la synthèse d’échantillons monophasés de la phase pérovskite tout le long du domaine de composition. L’étude de la synthèse par flash combustion a d’abord déterminé que le combustible le plus efficace pour la synthèse était la glycine, puis que l’apport de titane permettant la formation de la phase la plus performante est le nitrate de Titane (TiO(NO3)2) synthétisé à partir du butoxyde de titane.La densification des poudres obtenues par ces deux méthodes a été étudiée et comparée. Ces essais ont permis de comparer plusieurs paramètres sur la densification des échantillons. Ces paramètres sont le mode d’élaboration, le ratio Zr/Ti, ainsi que l’atmosphère de frittage. Des ajouts de frittages seront également testés sur deux compositions : CaZrO3 et Ca(Zr0,8Ti0,2)O3. Ces compositions ont été choisies car elles sont pauvres en titane, ce qui évite la réduction de cet élément qui transformerait le condensateur en semi-conducteur lors d’un frittage sous atmosphère réductrice. Cette étude comparative de ces différents paramètres porte également sur les propriétés diélectriques des échantillons ainsi produits
The compositional domain Ca(ZrxTi1-x)O3 has been studied in order to understand the formation of solid solution between CaTiO3 and CaZrO3. The aim of this study is the application of such formulations for multilayer ceramic capacitors with non-nobles metal armatures. The synthesis on the line CaTiO3/CaZrO3 is poorly known, either by solid state or by flash-combustion. The study and optimization (mixing/grinding, temperature of calcination) of the solid-state synthesis has allowed the synthesis of single-phase samples made of the perovskite phase along the whole compositional range. The study of the solution-combustion synthesis first determined that the most efficient fuel for the synthesis was glycine, then the fact that the titanium input allowing the formation of the purest phase is TiO(NO3)2, synthesized from titanium butoxide.The densification of the powders obtained by these two methods was studied and compared. These tests allowed to compare several parameters on the densification of the samples. These parameters are the powders’ method of elaboration, the Zr/Ti ratio and the sintering atmosphere. Sintering adds were also be tested on two compositions: CaZrO3 and Ca(Zr0.8Ti0.2)O3. These compositions have been chosen because they are weak in titanium, which avoids reduction and appearance of semi-conduction of Ti that would transform the capacitor into a p-semiconductor during sintering in a reducing atmosphere. This comparative study of these different parameters also deals with the dielectric properties of the samples thus produced

Le marché de l'éclairage est un marché de masse à diffusion large en pleine mutation face aux nouvelles contraintes environnementales. Il s'inscrit dans une démarche de préservation de l'environnement avec une volonté européenne de voir sa consommation énergétique réduite de 20% d'ici 2020. Les luminophores jouent un rôle prépondérant dans les performances des systèmes d'éclairage utilisant comme sources d'excitations des LEDs bleues ou UV, ou encore un plasma (Xe-Ne), où ils permettent de convertir les photons incidents (VUV, UV ou bleus) en lumière visible. Dans le cadre de cette thèse, nous nous sommes intéressés à la production de lumière blanche. Pour obtenir une couleur la plus proche du blanc idéal et répondant aux mieux au cahier des charges de l'éclairage domestique, une amélioration des performances des luminophores utilisés classiquement est nécessaire. Au cours de ces travaux nous avons porté notre attention sur deux aluminates de formulations Y3Al5O12 dopé Ce3+ (YAG :Ce) et BaMgAl10O17 dopé Eu2+ (BAM :Eu). L'aspect novateur repose d'une part sur la synthèse de ces luminophores sous forme de nanoparticules par des voies de synthèse originales (la voie solvothermale et la combustion assistée par micro-ondes respectivement) et d'autre part sur leur mise en forme (revêtements composites " luminophores/polymère "). Plusieurs techniques expérimentales (DRX, IR, Mössbauer, aimantation, MEB, MET,...) ont été utilisées afin de caractériser leurs propriétés structurales et morphologiques. L'étude des performances optiques de ces luminophores enregistrées sous excitations bleue, UV et/ou VUV nous a permis de mettre en évidence leur utilisation potentielle dans les nouveaux dispositifs d'éclairage : associés à d'autres luminophores (rouge pour le YAG :Ce; rouge et vert pour le BAM :Eu) en proportions adéquates, il est possible de générer de la lumière blanche présentant les propriétés escomptées.

Os cimentos de fosfato de cálcio apresentam uma série de vantagens de utilização em ortopedia e traumatologia, sendo as mais destacadas a sua biocompatibilidade e bioatividade, as quais permitem a osteocondução dos tecidos ósseos e o endurecimento “in situ”, permitindo maior facilidade de manipulação. Entretanto; através dos métodos convencionais de reação no estado sólido há uma grande dificuldade em se obter a fase α- fosfato tricálcico pura. Com o desenvolvimento deste trabalho foi possível sintetizar a fase α-fosfato tricálcico nanoestruturado com elevado grau de pureza, utilizando-se o método de síntese de combustão em solução. Após os estudos da influência do pH, da natureza do combustível (uréia ou glicina) e dos teores estequiométricos de combustível (0,75; 1,0; 1,5 e 2,0) foi possível definir os melhores parâmetros de síntese (pH 1,5 e combustível uréia em teor duas vezes maior do que o estequiométrico). Com a definição dos parâmetros ótimos de reação, estudou-se a viabilidade de sua utilização como cimento de fosfato de cálcio. Nesta etapa verificou-se a influência do tamanho de partícula através do tempo de moagem. Para tempo de moagem de 180 minutos foram obtidos valores de resistência mecânica à compressão de até 30,4 MPa. Porém após a imersão em solução de plasma sanguineo simulado (SBF) em tempos crescentes de até 28 dias, ocorreu a diminuição desta propriedade o que é indicativo da alta solubilidade dos pós de α-fosfato tricálcico obtidos via síntese de combustão em solução. O ensaio de citotoxicidade In Vitro demonstrou que o CFC sintetizado neste trabalho não apresentou efeito tóxico para as células. Na sequência do trabalho, investigou-se a viabilidade da aplicação do CFC como substituto ósseo e como carga cerâmica em criogéis poliméricos para utilização em engenharia de tecidos. Inicialmente utilizou-se o sistema dimetilaminoetil metacrilato (DMAEMA) com a adição de 5% de um ácido acrílico (ácido acrílico ou ácido metacrílico), porém tal sistema se mostrou muito instável e apresentou baixa reprodutibilidade. Dessa forma, substituiu-se o ácido acrílico pelo monômero hidroxietil metacrilato (HEMA), pelo fato de o último possuir maior estabilidade química e melhores propriedades mecânicas. Com o uso deste sistema foram obtidos arcabouços porosos através do método de criopolimerização com porosidade de até 75% e poros de até 1 milímetro de diâmetro. A adição de α-fosfato tricálcico às estruturas porosas pouco influenciou nas propriedades físicas da rede polimérica e nas propriedades mecânicas dos arcabouços porosos, porém aumentou significativamente a biocompatibilidade destes, permitindo a adesão e a proliferação de células tronco mesenquimais. A presença de colágeno do tipo I e de fosfatase alcalina são bons indicativos de que as células tronco mesenquimais estão se diferenciando em tecido ósseo e demonstram o potencial destes materiais para o seu uso como biomaterial e mais especificamente como substitutos ósseos.
The calcium phosphate cements have a large number of advantages regarding its use in orthopedics and traumatology, being the most prominent its biocompatibility and bioactivity, which allows the osteoconductive of bone tissue and in situ hardening, allowing greater ease of handling. However, the use of conventionals synthesis methods, e.g. solid state reactions, brings great difficulty to the obtainment of highly pure α- tricalcium phosphate phase. In this thesis, the use of the solution combustion synthesis method allowed to synthesize nanostructured α-tricalcium phosphate with high purity. Further studies on pHs influence, fuel natures (urea or glycine) and fuel ratio (0.75, 1.0, 1.5 and 2.0) allowed to define the best synthesis parameters (pH 1.5 and urea fuel content in two times higher than the stoichiometric). After choosing the best paramaters to the obtainment of higly pure α-tricalcium phosphate, we studied the feasibility of their use as calcium phosphate cement (CFC) by studing the influence of particle size by increasing the milling time from 30 to 180 minutes. The better results were found for the milling time of 180 minutes. Compressives strength of up to 30.4 Mpa were obtained for this formulation. However, after soaking the calcium phosphate cements in simulated blood plasma (SBF) in growing times up to 28 days, a decrease in the compressive strenght was noticed, which is an indicative of the high solubility of the α-tricalcium phosphate powders obtained by solution combustion synthesis. After the obtainment of the calcium phosphate cements, its application as bone substitute and as ceramic load in polymeric cryogels for use in tissue engineering were studied. Initially, the system dimethylaminoethyl methacrylate (DMAEMA) with 5% of an acrylic acid (acrylic acid or methacrylic acid) was used, but due its great instability and lack of reproductbility this system was abandoned. Since it has greater chemical stability and good mechanical properties, the monomer hydroxyethyl methacrylate (HEMA) was chosen as pair to the DMAEMA monomer. With the use of this polymeric system, porous scaffolds with porosity of up to 75% and pores up to 1 mm in diameter were obtained by the method of cryopolymerization. The addition of α-tricalcium phosphate to the porous scaffolds did not showed a significant influence on physical properties of the polymer network nether on mechanical properties of porous structures. However, it increased significantly the biocompatibility of the scaffolds, allowing the adhesion and proliferation of mesenchymal stem cells. The presence of type I collagen and alkaline phosphatase are good indicators that mesenchymal stem cells are differentiating into bone tissue and demonstrate the potential application of these materials as biomaterials, more specifically as bone substitutes.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Doutoramento em Nanociências e Nanotecnologia
The strong progress evidenced in photonic and optoelectronic areas, accompanied by an exponential development in the nanoscience and nanotechnology, gave rise to an increasing demand for efficient luminescent materials with more and more exigent characteristics. In this field, wide band gap hosts doped with lanthanide ions represent a class of luminescent materials with a strong technological importance. Within wide band gap material, zirconia owns a combination of physical and chemical properties that potentiate it as an excellent host for the aforementioned ions, envisaging its use in different areas, including in lighting and optical sensors applications, such as pressure sensors and biosensors. Following the demand for outstanding luminescent materials, there is also a request for fast, economic and an easy scale-up process for their production. Regarding these demands, laser floating zone, solution combustion synthesis and pulsed laser ablation in liquid techniques are explored in this thesis for the production of single crystals, nanopowders and nanoparticles of lanthanides doped zirconia based hosts. Simultaneously, a detailed study of the morphological, structural and optical properties of the produced materials is made. The luminescent characteristics of zirconia and yttria stabilized zirconia (YSZ) doped with different lanthanide ions (Ce3+ (4f1), Pr3+ (4f2), Sm3+ (4f5), Eu3+ (4f6), Tb3+ (4f8), Dy3+ (4f9), Er3+ (4f11), Tm3+ (4f12), Yb3+ (4f13)) and co-doped with Er3+,Yb3+ and Tm3+,Yb3+ are analysed. Besides the Stokes luminescence, the anti- Stokes emission upon infrared excitation (upconversion and black body radiation) is also analysed and discussed. The comparison of the luminescence characteristics in materials with different dimensions allowed to analyse the effect of size in the luminescent properties of the dopant lanthanide ions. The potentialities of application of the produced luminescent materials in solid state light, biosensors and pressure sensors are explored taking into account their studied characteristics.
O progresso observado nas últimas décadas na área da fotónica e optoelectrónica, acompanhado de um desenvolvimento exponencial nas áreas da nanociência e nanotecnologia, resulta numa constante procura por materiais luminescentes eficientes com características cada vez mais exigentes. Matrizes de largo hiato energético dopadas com iões lantanídeos assumem-se, atualmente, como uma classe de materiais luminescentes de elevada importância tecnológica. Dentro destas, a zircónia apresenta uma combinação de propriedades químicas e físicas que a potenciam como matriz para a incorporação dos iões mencionados, tendo em vista o seu uso em diversas áreas, destacando-se as aplicações em iluminação e sensores óticos, entre os quais sensores de pressão e biossensores. Associada à necessidade de materiais luminescentes com características superiores, encontra-se a necessidade de técnicas de produção rápidas, económicas e com potencial para produção em larga escala. Tendo em conta estas necessidades, técnicas como a fusão de zona com laser, combustão em solução e ablação laser em meio líquido são exploradas neste trabalho para a produção de monocristais, nanopós e nanopartículas de matrizes à base de zircónia intencionalmente dopadas com lantanídeos. Em simultâneo, é realizado um estudo detalhado das propriedades morfológicas, estruturais e óticas dos materiais produzidos. São estudadas as características luminescentes de matrizes de zircónia (ZrO2) e zircónia estabilizada com ítrio (YSZ) dopadas com vários iões lantanídeos (Ce3+ (4f1), Pr3+ (4f2), Sm3+ (4f5), Eu3+ (4f6), Tb3+ (4f8), Dy3+ (4f9), Er3+ (4f11), Tm3+ (4f12), Yb3+ (4f13)) e co-dopadas com Er3+,Yb3+ e Tm3+,Yb3+. Para além da luminescência de Stokes, foi avaliada e discutida a emissão anti-Stokes (upconversion e radiação de corpo negro) sob excitação no infravermelho. A comparação da luminescência em materiais com diferentes dimensões permitiu analisar o efeito do tamanho nas propriedades luminescentes dos iões dopantes. A discussão do trabalho é acompanhada por uma integração dos resultados visando as aplicações destes materiais luminescentes em emissores do estado sólido, biossensores e sensores de pressão.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas
A S?ntese Cont?nua por Combust?o em Solu??o (SCCS) foi empregada na obten??o de p?s de di?xido de estanho nanoestruturados. Basicamente, uma solu??o precursora ? preparada, sendo posteriormente atomizada e aspergida na chama, onde ocorre a combust?o, levando ? forma??o das part?culas. A t?cnica apresenta um grande potencial na produ??o de nanopart?culas, principalmente pelo baixo custo de insumos e equipamentos. O di?xido de estanho (SnO2) nanoestruturado tem sido amplamente utilizado em diversas aplica??es, principalmente como sensores de g?s e varistores. No caso dos sensores ? base de cer?micas semicondutoras, em que as rea??es de superf?cies s?o respons?veis pela detec??o dos gases, a import?ncia da ?rea superficial e do tamanho de part?culas ? ainda maior. A prefer?ncia por um material nanoestruturado deve-se ao fato de que essas entidades apresentam alguns pontos fundamentais tais como, o aumento significativo da ?rea superficial comparados aos p?s microcristalinos convencionais e o reduzido tamanho de part?cula, que pode beneficiar certas propriedades como alta condutividade el?trica, alta estabilidade t?rmica, mec?nica e qu?mica. Neste trabalho, foram empregados como solu??o precursora cloreto de estanho dihidratado dilu?dos em ?lcool et?lico anidro. Foi utilizada a raz?o molar cloreto/solvente de 0,75 no intuito de investigar sua influ?ncia na microestrutura do material obtido. O fluxo da solu??o precursora foi de 3 mL/min. A an?lise por difra??o de raios X da solu??o precursora com raz?o molar cloreto/solvente de 0,75 indicou a obten??o de um p? cristalino e monof?sico e todos os picos s?o atribu?dos a fase SnO2. Par?metros de s?ntese como dist?ncia da chama com o atomizador, dist?ncia do sistema de capta??o com a chama piloto, raz?o molar e fluxo da solu??o precursora n?o afetaram a fase di?xido de estanho no material obtido. Na caracteriza??o do p? obtido, foram utilizadas t?cnicas como an?lises termogravim?tricas (ATG) e termodiferenciais (ATD), granulometria por difra??o de laser (GDL), an?lise cristalogr?fica por difra??o de raios X (DRX), morfologia por microscopia eletr?nica de varredura (MEV), microscopia eletr?nica de transmiss?o (MET), medida de ?rea superficial espec?fica (BET) e ensaio de condutividade el?trica. O conjunto de t?cnicas revelaram que o SnO2 apresenta comportamento de um material semicondutor, sendo um material potencialmente promissor ? aplica??o como varistor e em sistemas de sensores ? gases

碩士
國立中央大學
化學工程與材料工程研究所
92
This dissertation covers the synthesis and lithium-intercalating properties of LiMn2O4 prepared by a combustion process with ammonium nitrate as a porogenic agent and Hexamethylenetetraamine (HMTA) as a fuel. The synthesis parameters, temperature and duration of calcination and lithium stoichiometry, as well as metal ion：fuel mole ratio, were optimized in order to obtain products with the best electrochemical activity. The phase transitions of the products were investigated by thermogravimetric and differential thermal analyses, Structural properties of the products were investigated by X-ray diffraction, surface morphology by scanning electron microscopy and transmission electron microscopy, and surface area by the BET method. Lithium intercalation properties were studied by galvanostatic charge-discharge studies for different rate windows. The various redox regions and phase changes occurring during the charge-discharge processes were studied by cyclic voltammetry. The precursors for the synthesis of LiMn2O4 were metal nitrates dissolved in an aqueous solution of ammonium nitrate and HMTA in various mole ratios of total metal ion to fuel and the products were obtained by calcination at different temperatures and times. The optimal synthesis conditions were found to be 10h calcination at 700°C with lithium stoichiometry and mole ratio of total metal ion to fuel at 1.00. At a 0.1 C rate between 3.0 and 4.3 V, the product gave a first-cycle discharge capacity of 113 mAh/g, which faded to 88 mAh/g in the 200th cycle, with charge retention of 80%. The weight loss that occurs in the range from room temperature to about 120°C is ascribed to superficial water loss, as well as water loss from the hydration of manganese nitrate tetrahydrate, which begins to decompose at temperatures above 100°C. The sharp endotherm at 255°C is due to the melting of LiNO3. The main decomposition and product formation begin around 300°C. All the diffractograms show patterns corresponding to the cubic spinel structure in the Fd3m space group, suggesting that LiMn2O4 was formed during the initial decomposition of the mixture at 500°C itself. The particles were crystalline and had an average particle size of 10 ~ 40 nm, and a BET surface area of about 3.0361 m2/g. The good electrochemical behavior of the product was attributed to the nanocrystalline LiMn2O4 cathode particles by a modified solution combustion process.

碩士
國立成功大學
化學工程學系碩博士班
94
Microwave heating technique is a high efficient heating way, and there are many advantages such as capable of achieving high temperature, rapid, and uniform heating, therefore, it has been used widely recently. In this thesis, the microwave-assisted the solution combustion method was used to prepare Zn2SiO4:Mn, Y2O3:Eu, Y3Al5O11:Ce, BaMgAl10O17:Eu phosphors which can emit different colors, respectively. The experimental parameters such as active ion concentration, firing temperature, the origin of reactant, fuel, firing atmosphere, the type of firing, will be discussed to find the essential factor and to research better phosphor and high efficient phosphors could be obtained. For Zn2SiO4:Mn, the results show that the highest luminescent intensity could be achieved after calcining at 1200℃(under nitrogen atmosphere) with 3 mol% Mn doped. For YAG, the highest luminescent intensity was at 1600℃ with 3.5% Ce doped. For Y2O3, the highest luminescent intensity was at 1200℃ with 15% Eu doped. As shown in XRD patterns, a high purity of BAM structure could be obtained when calcined at 1400℃and the crystalline increases with increasing temperature and reaches its maximum at 1650℃ under reducing atmosphere (5% H2 + 95% N2) with 6% Eu doped.

碩士
國立成功大學
電機工程學系
102
Great electric insulation, high thermal conductivity, low dielectric constant, and low thermal expansion coefficient make AlN a very promising material for electric applications. Due to the high cost of the material, it is hard to be popular. In the study, we sintered the precursor-coated AlN powder at 800°C、900°C and 1000°C by SHS in order to obtain carbon-coated AlN powder for lower-cost synthesis use and further applications. We add sucrose in the 70% nitric acid solution first, wait until it was fully dissolved, then add AlN powder in the solution. After two steps of drying, it was sintered under Ar atmosphere for 2 hours. At last, we studied the density, grain, microstructure, dielectric properties and thermal conductivity with the product. We found that although the density and shrinkage rate increase as the sintered temperature increases, but it was not apparent. The X-ray patterns showed as we add more carbon precursor, the more carbon atom will substitute the “N” atom in the AlN crystal structure during the whole combustion process which will result in peak shift. The SEM also showed pores and defects from breaking plane of the product. For dielectric properties, we found as we increased the carbon precursor concentration, the dielectric properties didn’t get improved. We obtained the best dielectric constant 13.17 and dielectric loss 0.314 with 25wt% precursor concentration sintered at 800°C. At last, we obtained the thermal conductivity 1.048 W/m•K from the sample synthesized at 800°C. with 35wt% precursor added.

碩士
國立成功大學
化學工程學系碩博士班
101
Aluminum nitride (AlN) has many superior properties, but in practical application has not been growth rapidly as expected, one of the main reasons is the application problems has not resolved. The key point of the application problems is that AlN is easy to react with water for hydrolysis and deliquescence. The lattice structure, density and atomic size of AlN and silicon carbide (SiC) are very similar that they can form solid solutions in under certain conditions. This thesis wants to improve the hydrolyzed resistance and moisture resistance of AlN by solid solutions of AlN-SiC. Combustion synthesis AlN-SiC solid solutions at low nitrogen pressure region: properties decide by the ratio of Al and Si, the nitrogen pressure has poor correlation with properties. The flaky aluminum is unsuitable to synthesis solid solutions Due to the physical factors of shape. The experiment results show that AlN-SiC solid solutions synthesis by combustion synthesis has better hydrolyzed resistance and moisture resistance, reduce the forming rate of aluminium hydroxide (Al(OH)3) obviously. At high temperature (110℃) surrounding, the hydrolyzed resistance of AlN-SiC solid solutions even better than the phosphoric acid (H3PO4) surface treatment of AlN. The composition of AlN increase, the property of AlN-SiC solid solutions trend to AlN, but only solid solution trace amounts of SiC (5 mol%) can extend the time of forming Al(OH)3 obviously. Although combustion synthesis of AlN-SiC solid solutions has unreacted agent, the composites with epoxy has high thermal conductivity above half of AlN’s composites.

碩士
逢甲大學
航太與系統工程所
99
Formation of the solid solutions of ternary carbides (Ti,Nb)2AlC, (Cr,V)2AlC, and Ti3(Al,Si)C2, was conducted by self-propagating high-temperature synthesis (SHS). For the preparation of (Ti,Nb)2AlC, three reactant mixtures composed of Ti-Nb-Al-C, Ti-Nb2O5-Al-C, and Ti-Nb2O5-Al-Al4C3 were adopted. The solid solution of (Cr,V)2AlC was synthesized from the powder compacts of Cr2O3-V2O5-Al-C and Cr2O3-V2O5-Al-C-VC. The TiC-, SiC-, and Al4C3-added samples were used to produce Ti3(Al,Si)C2. The effect of sample stoichiometry was studied on the product composition and morphology, combustion wave velocity, and reaction temperature. The combustion process proceeded with a self-sustaining reaction front. For the reactant compacts of Ti-Nb-Al-C and Ti-Nb2O5-Al-C, the increase of Ti content in (Ti,Nb)2AlC increased the combustion velocity. Although the reversed trend was observed for the samples composed of Ti-Nb2O5-Al-Al4C3, the combustion velocity and temperature of the Ti-Nb2O5-Al-Al4C3 sample were higher than those of the Ti-Nb-Al-C and Ti-Nb2O5-Al-C powder compacts. The reaction front velocity was almost independent of the initial composition of the Cr2O3-V2O5-Al-C samples. With the addition of VC, the combustion velocity decreased with Cr content in the product (Cr,V)2AlC. On account of the variation of reaction exothermicity with sample stoichiometry, it was found that with an increase in the Al content of as-synthesized Ti3(Al,Si)C2 the combustion temperature and reaction front velocity decreased moderately for the TiC-added sample but substantially for the sample adopting Al4C3. However, a significant increase in both combustion wave temperature and velocity was observed for the SiC-added sample. The XRD analysis indicates that in addition to the dominant phase (Ti,Nb)2AlC, there are secondary phases TiC, NbC, NbAl3, and Nb2Al. The optimal product was obtained from the Ti-Nb-Al-C sample. For the formation of (Cr,V)2AlC, the binary carbide Cr7C3 was detected as the minor phase and the optimal composition of the product was obtained from the sample without addition of VC. On the synthesis of Ti3(Al,Si)C2, the final products contain TiC as a second phase and some other minor species like SiC and Ti3Al. For the Al4C3-added samples, however, the resulting products are dominated by TiC. According to the experimental evidence, the TiC-containing sample is the most favorable for the preparation of Ti3(Si,Al)C2 through the SHS process.

碩士
逢甲大學
航太與系統工程學系
101
Formation of (Ti,V)2AlC, (Cr,V)2AlC and (Ti,Cr)2AlC ternary solid solutions was conducted by self-propagating high-temperature synthesis (SHS). Effects of starting materials and sample stoichiometries were studied on the combustion temperature, flame-front velocity, and product composition and microstructure. In this study, TiO2 or Ti, Cr2O3 or Cr, and V2O5 were adopted as the sources of Ti, Cr, and V. Carbon was supplied by using Al4C3, TiC and carbon black powders. For the synthesis of (Ti,V)2AlC, experimental results indicated that with an increase of the Ti content, the combustion propagation changed from a planar to spinning mode and the extent of the sample melting was reduced. Flame-front velocity increased with increasing V2O5 content, but no obvious change in combustion velocity was found for the samples containing TiC. The synthesized products were composed mainly of (Ti,V)2AlC and Al2O3, and were characterized by a laminated microstructure. The fraction of Ti at the solution site was ranged from 0.1 to 0.6 for the samples using TiO2 and V2O5, and the Ti proportion was extended to 0.9 for the samples adopting Ti in place of TiO2. The combustion propagation phenomena associated with formation of (Cr,V)2AlC were similar to those of (Ti,V)2AlC. Due to substantial melting of the samples, the composition dependence of the flame velocity was not very apparent. For the samples containing Cr and V2O5, the flame velocity decreased as the content of V2O5 was reduced. The fraction of Cr at the solution site ranged 0.25~0.9 and 0.25~0.6 for the powder compacts adopting Cr2O3-V2O5 and Cr-V2O5, respectively. For the formation of (Ti,Cr)2AlC, the SHS processes exhibited different types of the combustion propagation including the planar front, pulsating motion, and spiral wave with multiple hot spots. The shape of the sample remained almost unchanged after combustion. Among samples of different starting materials, the samples with TiO2 and Cr2O3 had the highest flame velocity. The combustion velocities of the samples with Ti and Cr2O3 were relatively consistent. The use of carbon black accelerated the combustion wave. Instead of forming (Ti,Cr)2AlC, the solid sate combustion yielded Cr2AlC, TiC, and Al2O3.

碩士
逢甲大學
航太與系統工程學系
102
In this research, Self-Propagating High-Temperature Synthesis (SHS) was applied to synthesize MAX ternary solid solutions. The target products to be studied included Ti2Al(C,N), Ti2(Al,Sn)C, Ti3(Al,Sn)C2, and (Ti,Ta)2AlC. Effects of the sample stoichiometry on the flame-front velocity, combustion temperature, phase composition and microstructure of the product were investigated. The first part of this study focused on the X-site solid solution, Ti2Al(C,N). Nitride compounds, TiN, AlN, BN, and Si3N4, were adopted as the solid sources of nitrogen to mix with Ti, Al, and C powders for the production of Ti2Al(C,N). Experimental results showed that combustion velocity and temperature decreased with increasing TiN and AlN. When BN and Si3N4 were used, a broad range of the N substitution from Ti2Al(C0.8N0.2) to Ti2Al(C0.2N0.8) was achieved. Due to reduced reaction exothermicity, the degree of element substitution was restricted between Ti2Al(C0.8N0.2) and Ti2Al(C0.5N0.5) for the TiN- and AlN-added samples. The second part was to study the A-site solid solutions, Ti2(Al,Sn)C and Ti3(Al,Sn)C2, from the powder mixtures of Ti, Al, Sn, and carbon black powders with addition of TiC or Al4C3 as the other source of carbon. A better degree of the product formation was obtained for Ti2(Al,Sn)C than Ti3(Al,Sn)C2. In particular, the samples adopting TiC were more favorable than those with Al4C3 for the synthesis of Ti2(Al,Sn)C. The third part of this study was to fabricate the M-site solid solution, (Ti,Ta)2AlC, from elemental powder compacts of Ti, Ta, Al, and carbon black. With an increase in the Ta content, the flame-front velocity was reduced but reaction temperature was slightly changed. Formation of (Ti,Ta)2AlC was confirmed by the XRD pattern of the product. Based upon the SEM observations, the plate-like microstructure typical of the MAX ternary compound was found. In addition, two MAX solid solutions featuring double substitution locations were studied and they were the MX- and AX-site carbonitrides, (Ti,Nb)2Al(C,N) and Ti2(Al,Sn)(C,N). Finally, this research examined the relationship between formation of MAX solid solutions and the radius of substitution atoms. It was found that two atoms at substitution sites with a radius difference less than 10% facilitated the formation of MAX solid solutions by SHS.

Solution processed amorphous metal oxides have been showing competitive electronic performance to the ones produced by vacuum-based techniques, reducing the associated cost. These metal oxides are compatible with a variety of upscaling printing techniques, however, is crucial the optimization of the printing process to obtain stable, reproducible, and high-performance devices. Furthermore, it is important to find alternatives to some of the elements often used (gallium and indium) due to their toxicity and scarcity as well as finding safer solvents to those used in industry. The compatibility with inkjet printing (IJP) of solution processed aluminum oxide (AlOx) (2-methoxyethanol as solvent) and zinc tin oxide (ZTO) using different solvents: ethanol, ethanol (50%).H2O (50%), 1-methoxy-2-propanol (1-MP) and 2 methoxyethanol (2-ME) was performed. Spin-coated ZTO thin film transistors (TFTs) based on ethanol did not show promising results. Spin-coated devices using 1-MP as solvent had decent performance with IOn/IOff ratios of 105 and low subthreshold swing (SS) of 0.66 V.dec-1, however the ink is not compatible with inkjet printing. IJP of 2-ME based ZTO and AlOx thin films was optimized by changing the ultraviolet pre-treatment time, the drops per inch (DPIs), post annealing time, printing speed and number of layers. IJP printed metal-insulator-semiconductor (MIS) capacitors with AlOx based on 2-ME as solvents were printed with one- and two-layers showing breakdown voltages above 1 MV.cm-1. Lastly IJP ZTO/AlOx TFTs based on 2-ME as solvent were achieved with competitive performance showing a mobility of 2.2 cm2.V-1.s-1, a SS of 0.49 V.dec-1 and a IOn/IOff current ratio of 103 on the best devices. The results are the first fully IJP TFTs at CENIMAT/CEMOP and are in accordance with the values typically reported in literature for solution processed ZTO and AlOx, with performance matching devices produced by spin-coating.
Óxidos metálicos amorfos processados por solução apresentam desempenho eletrónico competitivo para aplicações que requerem transparência e flexibilidade. Estes óxidos são compatíveis com variadas técnicas de impressão mas a otimização destes processos é crucial para se obter dispositivos estáveis, reprodutiveis e de alto desempenho. É também importante encontrar alternativas a elementos usados frequentemente como o gálio e indio mas que são raros e/ou apresentam toxicidade, bem como descobrir solventes alternativos mais seguros do que os que são habituais nesta indústria. A compatibilidade com inkjet printing (IJP) de óxido de alumínio (AlOx) (2-methoxyethanol como solvente) e óxido de estanho e zinco (ZTO) usando vários solventes: etanol, etanol (50%).H2O (50%), 1-methoxy-2-propanol (1-MP) e 2-methoxyethanol (2-ME) foi testada. ZTO baseado em etanol depositado por spin-coating não mostrou resultados promissores para aplicação em dispositivos e embora transistores baseados em 1-MP como solvente tenham obtido bons resultados por spin-coating, IOn/IOff ratios de 105 e baixo subthreshold swing de 0.66V.dec-1, a tinta nao mostrou qualquer indicação de ser compatível com inkjet. IJP de ZTO e AlOx baseados em 2-ME como solvente foi otimizado com variação do tempo de tratamentos UV, drops-per-inch (DPI), tratamentos de post annealing, velocidade de impressão e número de camadas. IJP de condensadores MIS (metal-isolante-semicondutor) com AlOx com 2-ME como solvente foram produzidos com uma e duas camadas demonstrando tensões de breakdown suiperiores a 1MV.cm-1. Por último TFTs de ZTO/AlOx produzidos por IJP e baseados em 2-ME como solvente exibiram desempenho copetitivo com mobilidades de 2.2 cm2.V-1.s-1, SS de 0.49 V.dec-1 e currente IOn/IOff de 103 nos melhores dispositivos. Estes são os primeiros TFTs produzidos totalmente por IJP no CENIMAT/CEMOP exibindo valores competitivos com os reportados na literatura para TFTs de ZTO/AlOx de spin-coating processados por solução.

Solution processing of amorphous metal oxides has been used as an option to implement in flexible electronics, allowing to reduce the associated costs, when compared with vacuum processes. Recent research has been more focused on the semiconductor layer; however, the dielectric layer is equally important since its responsible for the stability and electric performance of the device. This work aims to evaluate hybrid dielectric thin films, using aluminium oxide and different types of polyvinylpyrrolidone (PVP), both obtained by solution process using solution combustion synthesis (SCS), to study the influence of the amount of organic material used in the insulator layer, as well as to study the influence of the hybrid insulator obtained in oxide thin film transistors (TFTs) using indium-gallium-zinc-oxide (IGZO) and zinc-tin-oxide (ZTO) as semiconductor layer. The insulator layer was obtained using aluminium nitrate nonahydrate and polyvinylpyrrolidone (PVP) with different molecular weights (10000 and 40000) and different percentages as precursor solutions, using urea as fuel and 2-methoxyethanol as solvent. The best hybrid dielectric was obtained with 0.8 % PVP 40000 (weight per volume), showing a breakdown voltage of 1.1 MV/cm, low density leakage current of 9.6 × 10-5 A/cm2, capacitance per area of 123 nF/cm2, thickness of 49.35 nm, annealed at 200 °C for 30 minutes. Moreover, the roughness study obtained using atomic force microscopy showed highly smooth surface, resulting in improvement dielectric-semiconductor interface, while still maintaining an amorphous nature. These characteristics allowed this hybrid dielectric, lead to enhanced TFTs electrical properties. The best performing thin films were applied in IGZO TFTs as hybrid dielectrics. The optimized TFTs show good reproducibility with an average mobility of 40.24 ± 1.1 cm2∙V-1∙s-1, subthreshold slope of 0.169 ± 0.012 V∙dec-1, a turn-on voltage of 0.078 ± 0.004 V and a low operating voltage (maximum 2 V).

碩士
國立臺北科技大學
資源工程研究所
97
BaySr1-yCoxFe1-xO3-δ is considered to be one of the best cathode materials for IT-SOFC. The material, however, has also been found to carry with it several disadvantages, notably high thermal expansion coefficient, low conductivity, and high cost. The study accordingly uses copper to replace cobalt to develop a new cathode material Ba0.5Sr0.5CuxFe1-xO3-δ for IT-SOFC. The objective of the study is two-fold: 1.Synthesis of pure Ba0.5Sr0.5CuxFe1-xO3-δ perovskite; and 2. Discussion of the material’s chemical and physical properties. Ba0.5Sr0.5CuxFe1-xO3-δ perovskite was synthesized by solution combustion. As indicated by the results, glycine-nitrate-process (GNP) was able to shorten the time of synthesis and reduce the calcination temperature. Pure cubic perovskite products were observed in X-ray diffraction (XRD) measurement with Cu-dopping at X = 0.1 to 0.3. And the composition of the products was confirmed using ICP-AES. It was also observed that, as the G/M ratio rose, three different combustion modes occurred respectively: volumetric combustion, self-propagating combustion, and smothering combustion. The situation at G/M=2 and pH=2 was identified to be the best condition for synthesizing Ba0.5Sr0.5CuxFe1-xO3-δ. Moreover, the study also adopted EDTA-glycine combustion method to prepare Ba0.5Sr0.5CuxFe1-xO3-δ - BaCeO3 perovskite. This method boasts an extensive synthesis range, so Ba0.5Sr0.5CuxFe1-xO3-δ - BaCeO3 could be synthesized at pH from 4 to 11. Moreover, adding NH3NO2 was found to be good for combustion reaction. In this study, chemical stability with electrolyte, conductivity, and sintering behavior were examined. Cu-doping appeared to decrease the melting point of the synthesized material. Of the three common electrolytes (GDC, SDC, and YSZ), GDC was found to work best with Ba0.5Sr0.5CuxFe1-xO3-δ in achieving high chemical stability. The best conductivity of 127.46 S/cm was achieved when the temperature was 346℃ and X=0.2. Copper would diffuse to the surface when the sintering temperature rose above the melting point of the synthesized material. The study finds Ba0.5Sr0.5CuxFe1-xO3-δ compounds capable of sustaining high conductivity at low temperature. Its ability to reduce synthesis temperature and material cost makes Ba0.5Sr0.5CuxFe1-xO3-δ a promising new cathode material for IT-SOFC.

Solution combustion synthesis (SCS) with its origin at IPC department of IISc has been widely practiced for synthesis of oxide materials. It is simple and low cost process, with energy and time savings that can be used to produce homogeneous, high purity, uniformly doped, nano crystalline ceramic powders. The powders characteristics such as crystallite size and surface area are primarily governed by enthalpy, flame temperature of combustion, fuel and fuel to oxidizer ratio ( F/O). In the present work an attempt has been made to investigate the process in order to exercise a control over the phase formation and nature of the product. Initial part of the work deals with the effect of fuel to oxidizer ratio on the powder properties of binary oxides with urea as fuel. The variation of adiabatic flame temperatures are calculated theoretically for different F/O ratios according to thermodynamic concept and correlated with the observed flame temperatures. Difference in the measured flame temperature and theoretical flame temperature in the fuel rich region is explained on the basis of incomplete combustion model. The effect of decomposition temperature difference of fuel and oxidizer, solubility of reactants on exothermicity of combustion reaction taking aluminiumnitrate system for various fuels is investigated. The effect of mixed fuel approach is studied by using the urea-glycine mixed fuel system using aluminium nitrate as oxidizer and employed for successful synthesis of the gamma alumina. Further Compaction behavior of SCS nano ceramic powders is studied by using Universal testing machine and the effect of F/O ratio, on agglomeration strength, aggregation strength of powder is investigated. Very few reports can be found on usage of SCS ceramic powder for biomaterial applications. By using these investigations a pyroxene series Diopside (CaMgSi2O6) silicate material is synthesized by SCS. Effect of different fuels on Diopside (DP) phase formation is investigated. Finally the DP and DP-ZnO composites, made by using Uniaxial hot pressing are investigated for their antibacterial, cytocompatibility properties. Antibacterial activity of E.Coli bacterium of Diopside powders was dose dependent type. Results of the bioactivity investigations shown flattened MC3T3 mouse osteoblast cells and MC C2C12 Myoblast cells and linkage bridges formed between them on Diopside and DP-ZnO surfaces show cyto compatibility and MTT results showed that percentage of ZnO needs to be tailored between 0-10 in order to achieve maximum cytocompatibility coupled with antibacterial property.

博士
國立成功大學
化學工程學系碩博士班
101
Titanium dioxide (TiO2) has demonstrated several potential applications, including photocatalysts, dye-sensitized solar cell (DSSC), pigment, and electronic data storage memory, etc. In this thesis, TiO2 powders were synthesized by a solution combustion synthesis method in which glycine, urea and thiourea were used as the fuel and titanyl nitrate was used as the oxidizer. Various fuel-to-oxidizer ratios were studied for their effects on the combustion phenomena and the properties of the synthesized TiO2. The fuel-to-oxidizer ratio was found to determine the maximum combustion temperature, which in turn affects the specific surface area, crystallite size, and weight fraction of anatase phase of the synthesized TiO2. The synthesized TiO2 all contain carbonaceous species and are either pure anatase or anatase–rutile mixed phase in crystalline structure. The photocatalytic activity of the TiO2 was found to correlate to a certain degree with the specific surface area, crystallitesize, weight fraction of anatase phase, and visible and IR absorbances. The mixed phase TiO2 shows a higher photocatalytic activity than the pure anatase phase TiO2 when containing a small fraction (＜~25 wt%) of rutile phase but a lower phoyocatalytic activity when containing a large fraction (＞~25 wt%) of rutile phase. The synthesized TiO2 all show higher photocatalytic activity than Degussa P25 TiO2. The enhanced photocatalytic activity was attributed mainly to sensitization by the carbonaceous species and larger amounts of hydroxyl group adsorbed on the TiO2 surface. These TiO2 nano powders were used to fabricate photoelectrodes for the DSSC and their performance was compared to that of the DSSC fabricated with Degussa P25 TiO2. The results showed that the TiO2 could work well as photoelectrode for DSSC. The solution combustion synthesis TiO2 contained impurities of C and/or S, thus exhibiting visible light absorption and reduced band gap. The open circuit voltage and the fill factor both varied little among the various TiO2 and thus both had little effect on the photoelectrical conversion efficiency (η). However, the variation of η was seen to be in quite a good agreement with that of the short circuit current (Isc), suggesting that η was dominated by Isc. Isc was found to be enhanced by light scattering effect due to the presence of large particles but reduced by high impurity content due to an increase in electron transfer resistance. In addition, the specific surface area of the powders was found to be an important factor affecting the Isc and thus the η.

碩士
國立臺北科技大學
材料科學與工程研究所
99
This study aimed to prepare MAl2O4（M = Ca, Sr, Ba）by solution combustion method. The impact of the doping concentration of Eu on the luminescence and lattice structure was examined. The 4f65d1 → 4f7 spectrum of Eu2+ fired in reduced atmosphere was continuous and broad. Depending on host lattices, various colors, intensity and characteristic of emission spectrum were recognized. Analyzing instruments like X-ray diffractometer (XRD), fluorescence spectrometer, and scanning electron microscope (SEM) were utilized to analyze the crystallinity, the phosphorescence characteristic, and the surface structure, respectively. Furthermore, with help of differential thermal (DTA) / thermogravimetry analyzer (TGA), conditions for firing process were explained. 　　It was experimentally confirmed the reaction time could be effectively reduced by adopting solution combustion method. The product showed high purity and homogeneous distribution of particle size. As the Glycine/Metal nitrate(G/M) ratio increased, three different combustion modes - volumetric, self-propagating, and smothering combustion - occurred respectively. An appropriate G/M ratio resulted in SHS phenomenon, so that it was identified as the optimized synthesis condition. MAl2O4:Eu2+(M = Ca, Sr, Ba) phosphors showed a 6P7/2→ 8S7/2 transition with bluish 450 nm, greenish 520 nm and 500 nm emission. This phenomenon resulted from the covalence and crystal field splitting effects of the host lattice. In contrast, the emission peaks of MAl2O4:Eu3+(M = Ca, Sr) phosphors were originated from 5D0→ 7FJ(J=1,2,3,4) transition, which showed an orange-red color. Variation of host lattices did not play a critical role in this process. 　　According to excitation spectra, the main excitation peaks of MAl2O4:Eu2+(M = Ca, Sr, Ba) and MAl2O4:Eu3+(M = Ca, Sr) phosphors are located at ultraviolet region. Stimulated by UV-LED, both of them could absorb the UV wave band red, green, and the blue three kind of phosphor way blending with white light. The white light generated by such conversion covered a wavelength range closer to that of the natural light. Owing to higher color rendering property, higher light color uniformity, and absence of color deviation, these phosphors have high application potential for the white light LED industry.

碩士
國立成功大學
化學工程學系碩博士班
97
A commercial and potential method to synthesis nitrides or oxynitrides currently is reducing oxides at nitrogen atmosphere. Our laboratory has already successfully product silicon nitride and aluminum nitride from silicon oxide and aluminum oxide. This study used previous technical basis that our laboratory established to synthesis an advanced oxynitride material, SiAlONs which include silicon, aluminum, oxygen and nitrogen atom in its structure. Solution combustion synthesis we used that could help nitridation reaction precursors mix very well and close to nano-scale particle size. We could obtain α-SiAlON which was mainly phase in the product after precursors underwent carbothermal reduction nitridation and doped activator made the host have luminescent property. The study mainly focused on 1. carbon ratio, 2. reaction temperature, 3. seeds effects, 4. activator concentrations, 5. the effects of morphology of the precursors. The analytic instruments included XRD, PL, SEM and the best result achieved in this study when carbon was 4 times theoretical value, reaction temperature was 1500℃, Eu2+ was doped 0.5 and seed was doped 50 mol﹪.According to the SEM, we observed particle size distribution was from submicron to micron.

Solution-based memristors have shown a great potential to fulfill several requirements of the Internet of Things (IoT) such as, high density and ultra-low power devices by using low-cost and simple fabrication methods. In this work, solution-processed indium-gallium-zinc oxide (IGZO) thin films are produced using a combustion synthesis process. To improve their performance in memristor devices different parameters are studied: the variation of molar proportion, number of deposited layers and annealing temperature. Memristors with higher number of layers and annealing temperatures show low operating voltage, good endurance, great yield, and retention up to 105 s in air environment conditions. The best condition reached was IGZO (1:3:1) memristor with 7 deposited layers annealed at 300 ºC. These devices can be programmed in a multi-level cell operation mode, up to 8 different resistive states. Furthermore, the same devices show promising features for neuromorphic computing applications since they can emulate the plasticity of a synaptic junction by replicating potentiation and depression. The results achieved are quite promising and even in some cases surpass the current state of the art.
Memristores baseados em processos de solução têm demonstrado um grande potencial para cumprir requisitos da Internet das Coisas (IoT), como dispositivos de elevada densidade e ultrabaixo consumo de energia aliado a métodos de fabrico simples e de baixo custo. Neste trabalho, filmes finos de óxido de índio-gálio-zinco (IGZO) são produzidos através do processo de síntese por combustão. Para melhorar o desempenho dos filmes de IGZO em memristores, são estudados diferentes parâmetros: a variação da proporção molar, o número de camadas depositadas e a temperatura de recozimento. Os memristores com maior número de camadas recozidas à temperatura mais elevada apresentam baixa tensão de operação, boa resistência, ótimo rendimento e retenção de até 105 s à temperatura ambiente. A melhor condição alcançada foi um memristor IGZO (1:3:1) com 7 camadas depositadas recozidas a 300 ºC. Estes dispositivos podem ser programados num em modo de operação multinível até 8 estados resistivos diferentes. Além disso, os mesmos dispositivos apresentam características promissoras para aplicações de computação neuromórfica, uma vez que conseguem emular a plasticidade de uma junção sináptica, ao replicar a potenciação e depressão de uma sinapse. Os resultados alcançados são bastante promissores e mesmo em alguns casos superam o atual estado da arte.

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná
During the past decade, researchers have shown an increased interest in multifunctional nanomaterials. Magnetic Nanoparticles (MNP) have been one of the most attractive types of nanomaterials used in different fields, as in environmental protection and biomedical applications. These applications include drug delivery, magnetic resonance imaging, magnetic hyperthermia, among others. MNPs have been synthesized by various methods. Amongst the most common may be referred: thermal decomposition, microemulsion, coprecipitation, solution combustion and sonochemical synthesis. The main objective of this MSc thesis is the development of biocompatible MNPs with high potential for the controlled release of drugs. For this purpose, a magnetic core based on magnetite is developed by two different approaches of Solution Combustion Synthesis. In the first approach, the synthesis of MNPs is obtained by reduction of Fe (III) using citric acid, and the in second approach, the MNPs are synthesized using tangerine peel extract for the reduction of Fe (III). However, the material produced with the extract was not magnetic, and it was decided to not continue the methodology with it. Then, the magnetic core, produced with citric acid, is coated with a resin prepared from formaldehyde, resorcinol and TEOS, which is later carbonized by pyrolysis at 600 ºC. Subsequently, the silica generated from TEOS is removed by etching with NaOH in order to create a void inside the particle, which take the known yolk-shell shape. Finally, the materials are functionalized with nitric acid and subsequent pluronic F-127, for its biocompatibility and dispersibility. These materials are then assessed in the controlled release of two different drugs to test the potential of the developed magnetic nanostructures for drug delivery applications: Doxorubicin (DOX) and Omeprazole (OME). Drug Loading Capacity and Efficiency of 0.936 μg·μg -1 and 93.6% for DOX and 0.335 μg·μg-1 and 33.5% for OME are obtained at pH 7.4, respectively. Finally, the drug release is tested at the pH of the normal tissue (pH 7.4) and at the pH of the extracellular environment of the tumor (pH < 6.5), simulating different circumstances of the human body.
Durante a última década, os pesquisadores tem mostrado um interesse crescente em nanomateriais multifuncionais. As nanopartículas magnéticas (MNPs) tem surgido assim como um dos tipos de nanomateriais mais promissores para diversos fins, podendo ser utilizado, por exemplo, em proteção ambiental e em aplicações biomédicas. De entre estas aplicações podemos citar a libertação controlada de fármacos, a ressonância magnética, o tratamento hipertermia magnética, entre outros. As MNPs podem ser sintetizadas das mais diversas maneiras, entre as quais as mais comuns são: decomposição térmica, microemulsão, coprecipitação, síntese por combustão de solução e síntese sonoquimica. O principal objetivo desta tese é desenvolver MNPs biocompatíveis com grande potencial para a libertação controlada de fármacos. Para isso, será produzido um núcleo magnético, feito de magnetite, considerando duas abordagem de síntese de combustão de solução. Na primeira abordagem, as MNPs são produzidas reduzindo o Fe (III) com ácido cítrico. Na segunda abordagem, o agente responsável pela redução dos iões de Fe (III) é um extrato de tangerina, porém utilizando esse agente o material produzido não era magnético, e optou-se por não continuar a metodologia com ele. Em seguida, o núcleo magnético, produzido com o ácido cítrico, é revestido com uma resina preparada a partir de formaldeído, resorcinol e TEOS, que posteriormente é carbonizada por pirólise a 600 ºC. Após a carbonização, a sílica gerada a partir de TEOS é removida com NaOH, a fim de criar um vazio no interior do material, que assume a forma conhecida como casca de gema. Finalmente, os materiais são funcionalizados com ácido nítrico e subsequente plurônico F-127, para obter características de biocompatibilidade e dispersibilidade. Os materiais sintetizados são então avaliados na libertação controlada de dois fármacos, para testar o potencial das nanoestruturas magnéticas nessa aplicação biomédica: Doxorrubicina (DOX) e Omeprazol (OME). Obteve-se uma capacidade de carga dos fármacos e uma eficiência de 0,936 μg·μg-1 e 93,6% para DOX e 0,335 μg·μg -1 e 33,5% para OME, respetivamente, obtidas a pH 7,4. Finalmente, a libertação do fármaco é testada no pH do tecido normal (pH 7,4) e no pH do ambiente extracelular do tumor (pH < 6,5), simulando diferentes circunstâncias do corpo humano.
Also, I gratefully appreciate for the financial support of Project “RTChip4Theranostics - Real time Liver-on-a-chip platform with integrated micro(bio)sensors for preclinical validation of graphene-based magnetic nanocarriers towards cancer theranostics”, with the reference NORTE-01-0145-FEDER-029394, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); and CIMO - UIDB/00690/2020 - funded by Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020

Indium oxide (In2O3) has been widely used and studied as transparent conducting oxide (TCO). However, some of the more promising dopants for this oxide have not received much attention and even fewer explored by solution processes. This work focuses on developing solution processed doped (Hf, Mo, and Zr) In2O3 thin films and evaluating various annealing parameters on TCOs properties. Different processing syntheses, metallic cations molar ratio, and the number of deposited layers were studied, concluding that 0.2 M concentration and 8 layers deposition by spin coating using solution combustion synthesis (SCS) were the most favorable parameters. Optimized doped TCOs were obtained for 0.5 M % Hf-doped In2O3 when produced at 400 ˚C, showing high transparency in the visible range of the spectrum, a bulk resistivity of 5.73 × 10-2 Ω.cm, mobility of 6.65 cm2 /Vs and a carrier concentration of 1.72 × 1019 cm 3 . Finally, 0.5 M % Hf-doped In2O3 thin films were annealed in rapid thermal annealing (RTA) for 10 min at 600 ˚C, obtaining better results than before achieving a bulk resistivity of 3.95 × 10-3 Ω.cm, mobility of 21 cm2 /Vs and carrier concentration of 7.98 × 1019 cm-3.
O óxido de índio (In2O3) tem sido amplamente utilizado e investigado como óxido condutor transparente (TCO). No entanto, alguns dos dopantes mais promissores para este óxido foram pouco estudados e ainda menos explorados por processos de solução. Este trabalho foca no desenvolvimento de filmes finos dopados (Hf, Mo e Zr) In2O3 processados por solução e na avaliação de vários parâmetros de recozimento nas propriedades do TCO. Diferentes sínteses de processamento, razão molar de catiões metálicos e número de camadas depositadas foram estudadas, concluindo que a concentração de 0,2 M e a deposição de 8 camadas por spin coating usando síntese de solução por combustão (SCS) foram os parâmetros mais favoráveis. TCOs dopados otimizados foram obtidos para In2O3 dopado com 0,5 M% Hf quando produzido a 400 ˚C, mostrando alta transparência na região visível do espectro, uma resistividade em volume de 5,73 × 10-2 Ω.cm, mobilidade de 6,65 cm2 / Vs e uma concentração de portadores de 1,72 × 1019 cm-3 . Finalmente, filmes finos de In2O3 dopados com 0,5 M% de Hf foram recozidos em recozimento térmico rápido (RTA) por 10 min a 600 ˚C, obtendo resultados melhores do que os anteriores, atingindo uma resistividade em volume de 3,95 × 10-3 Ω.cm, mobilidade de 21 cm2 /Vs e concentração de portadores de 7,98 × 1019 cm-3.

The master's thesis is devoted to establish optimal parameters produced composites of iron oxide and carbon (FeOx/C) through the physicochemical study of the samples obtained for further use as anode materials of lithium-ion batteries (LIA). This interdisciplinary work was made in the laboratory of chemistry of compounds of rare-earth elements of the The Institute of Solid State Chemistry of the Ural Branch of the Russian Academy of Sciences as well as with the use of the equipment of the Ural Center for Shared Use «Modern nanotechnologies» of Ural Federal University named after the first President of Russia B. N. Yeltsin.
Магистерская диссертация посвящена установлению оптимальных параметров получения композитов из оксида железа и углерода (FeOx/C) посредством физико-химического исследования полученных образцов для дальнейшего использования в качестве анодных материалов литий-ионных аккумуляторов (ЛИА). Данная работа носит междисциплинарный характер и была выполнена в лаборатории химии соединений редкоземельных элементов ИХТТ УрО РАН, а также с использованием оборудования УЦКП «Современные нанотехнологии» УрФУ им. Б. Н. Ельцина.

Vanadium oxides are being used as the thermal sensing layer because of their applications in infrared detectors. They have high temperature coefficient of resistance, favorable electrical resistance and compatibility with the MEMS technology. Of all oxides of vanadium, only vanadium dioxide (VO2)has been highly investigated as it shows first order transition (semiconducting to metal transition-SMT)at 68 oC. First order transition is understood as the sharp change in the electrical resistance. The change in resistivity in this case is of the order of 105 over a temperature change of 0.1 oC at 68 oC in a single crystal. Doping vanadium oxides with elements like Mo and W reduce the transition temperature. This is very important for room temperature electrical and optical detection. Though most of the research groups subscribe to PLD, cost-effective methods with large area deposition are major focus of this research. Hence for synthesizing VO2 in bulk and thin films, Solution Combustion Synthesis (SCS), Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM) Chemical vapour deposition (CVD)and microwave are explored. Synthesis of doped VO2 films in CVD has not been done extensively to yield optical quality thin films. Chapter I surveys the use of phase transition in oxides system for a variety of practical applications. In particular, Vanadium dioxide (VO2) is chosen as it is found to be very useful for infrared and metamaterials based applications. VO2 is known for its first-order semiconducting to metallic transition (SMT). This chapter attempts to explain the influence of processing, doping, annealing, etc on the SMT characteristics. Important aspects such as the idea of hysteresis in VO2 and similarity to martensitic transformation are discussed. The scope and objectives of the thesis are discussed here. Chapter II explains in detail the materials and methods used to synthesize VO2 both in bulk and in thin lm form and methods used to study their characteristics. Brief description on the principle and the working of the home-built experimental set up needed for this study is elicited. In chapter III, attempts were made to understand the phase stability of VO2 and the evolution of crystal structures during the phase transition. VO2 crystallizes in P21/c space group at room temperatures with lattice parameters a=5.752 Ab=4.526 Ac=5.382 Aα=90 β=122.60 γ=90 . Precise control of synthesis parameters is required in stabilizing pure phase in bulk as well as thin lm form. This study focuses on the novel large scale two step synthesis of VO2 using Solution Combustion Synthesis. This involves synthesis of product utilizing redox reaction between metal nitrate and suitable fuel. Generally the products are nanocrystalline in nature due to self-propagation of the exothermic combustion reaction. First step involved the synthesis of V2O5 by combustion reaction between Vanadyl nitrate and urea. In the second step, the as-synthesized V2O5 has been reduced by a novel reduction technique to form monophasic VO2. The presence of competing phases like M1, M2, M3 and R are investigated by XRD, Raman spectroscopy, DSC, Optical and high temperature X-ray diffraction. Chapter IV deals with the reduction in phase transition temperature by doping the SCS synthesized VO2 with W and Mo. Effect of doping on the transition temperature was studied using differential scanning calorimetry (DSC) in both W and Mo. Electrical characteristics of Mo doped VO2 and Optical characteristics of the W-doped VO2 were also studied using four probe resistivity measurements and UV-VIS Spectroscopy respectively. W addition was found to be more effective in reducing the phase transition temperature. To understand further more on the W addition, X-ray photo-electron spectroscopy measurements were performed. W-addition alters the V4+-V4+ bonding and with W addition it is observed that V was present in V3+state. W was present in W6+ state. The addition of W to VO2 introduces more electrons to the systems and disturbs the V4+-V4+ thus reducing the phase transition temperature of VO2. Chapter V describes the large scale, large area deposition of thin films of VO2 by a cost effective method. A novel technique to deposit vanadium dioxide thin films namely, UNSPACM is developed. This simple two-step process involves synthesis of a V2O5 lm on an LaAlO3(LAO) substrate followed by a controlled reduction to form single phase VO2. The formation of M1 phase (P21/c) is confirmed by Raman spectroscopic studies. A thermally activated metal{insulator transition (MIT) was observed at 61 oC, where the resistivity changes by four orders of magnitude. The infrared spectra also show a dramatic change in reflectance from 13% to over 90% in the wavelength range of 7-15 m. This indicates the suitability of the films for optical switching applications at infrared frequencies. A trilayer metamaterial absorber, composed of a metal structure/dielectric spacer/vanadium dioxide (VO2) ground plane, is shown to switch reversibly between reflective and absorptive states as a function of temperature. The VO2 lm, which changes its conductivity by four orders of magnitude across an insulator{metal transition, enables the switching by forming a resonant absorptive structure at high temperatures while being inactive at low temperatures. The fabricated metamaterial shows a modulation of the reflectivity levels of 58% at a frequency of 22.5 THz and 57% at a frequency of 34.5 THz. Chapter VI explains the W doped VO2 thin films synthesized by UN-SPACM. Morphology of the thin films was found to be consisting of globular and porous nanoparticles having size 20 nm. Transition temperature decreased with the addition of W. 1.8 at. %W doping in VO2 transition temperature has reduced upto 25 oC. It is noted that W-doping in the pro-cess of reducing the transition temperature, alters the local structure and also increases room temperature carrier concentration. The presence of W, as was seen in Chapter IV, altered V4+-V4+ bonds and introduced V3+. W was found to be in W6+ state suggesting W addition increased the carrier concentration. Hall Effect measurements suggested the increased carrier con-centration. The roughness of the synthesized films were very high for them to be of de-vice quality, despite encouraging results obtained by electrical measurements. Hence in order to further improve the smoothness and thereby the optical quality of thin films, Chemical Vapour Deposition (CVD) is employed. Chapter VII outlines the effect of processing parameters and post pro-cessing annealing on the semiconductor-metallic transition of VO2. Here in this chapter, the influence of substrate temperature on the SMT properties of VO2 is explored. At different substrate temperatures, the percentage of phase fraction of V in V3+, 4+ and V5+ differed. Besides, the morphology also varied with substrate temperatures. Similarly it is observed that with annealing the VO2 film deposited on glass substrates, SMT properties enhanced which was attributed to filling out of oxygen vacancies. Si based substrates and non-Si based substrates were used for depositing VO2 thin films by CVD. Their temperature coefficient of resistance and SMT properties were studied in order to understand their potential in bolometer and thermal to optical valve based applications. Chapter VIII involves the study of VO2 thin films for thermal to optical valves. ITO coated glass substrates were used for the purpose. Thin films were deposited by both UNSPACM and CVD. It was observed that the reflectivity pro les of the films synthesized by the above said methods were very different. Hence in the process of understanding the huge difference in the reflectivity pro les, classical harmonic oscillator, Lorentzian model was employed to t the experimental data at room temperature whereas Drude-Lorentzian model was used to t the data at higher temperature (at 100 oC- after transition). With this fitting plasma frequencies of the CVD films were calculated. It was observed that defect chemistry of films synthesized by these methods were different. In order to further improve the smoothness of the films, microwave method was proposed in Chapter IX. The preliminary results showed the presence of uniform spheres and 3 D hierarchical structures of VO2 consisting of nanorods. This was extended to deposit VO2 thin films on ITO. DSC and Infrared reflectance pro le of VO2 nanopowder suggested the phase transition. Chapter X summarizes the work done for the thesis and provides insights to the applications and to the future work. The work reported in this thesis has been carried out by the candidate as part of the Ph.D.program. She hopes that this would constitute a worth-while contribution towards development of VO2 thin film technology and its challenges for reliable infrared device applications.