Made available in DSpace on 2014-10-09T12:25:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:54Z (GMT). No. of bitstreams: 1 06875.pdf: 3426497 bytes, checksum: f67e7359c8137f84a2c63219a3f4ce7a (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:52Z (GMT). No. of bitstreams: 0 / Eletrólitos sólidos cerâmicos de ZrO2:8% mol Y2O3 foram preparados com pós de três origens: pó comercial fabricado pela Nissan (Japão), pó obtido por coprecipitação dos hidróxidos no IPEN e pó obtido por mistura de óxidos (utilizando-se ZrO2 produzido na Usina de Zircônio do IPEN e Y2O3 (USA) de pureza superior a 99,9%). Esses materiais de partida foram analisados pelas seguintes técnicas: fluorescência de raios X para a determinação dos teores de ítrio, difração de raios X para a determinação das fases, sedimentação para a determinação da distribuição do tamanho de partículas, adsorsão gasosa (BET) para a determinação da área de superfície específica e microscopia eletrônica de transmissão para a determinação do tamanho médio de partícula. Amostras compactadas foram analisadas por dilatometria para avaliar os estágios de sinterização. As amostras sinterizadas foram caracterizadas por difração de raios X para análise de fases e microscopia eletrônica de varredura para análise da morfologia dos grãos. Análises por espectroscopia de impedância foram feitas para acompanhar o envelhecimento térmico dos eletrólitos sólidos de zircônia-ítria a 600 ºC, temperatura de trabalho do sensor permanente de oxigênio, e para estudar a sua cinética de sinterização. Os principais resultados mostram que o envelhecimento térmico a 600 ºC diminui a resposta (fem) do sensor nas primeiras 100 h até um valor estável. Além disso, os estudos de sinterização por espectroscopia de impedância permitiram encontrar correlações entre parâmetros elétricos, a cinética de sinterização e os mecanismos de crescimento de grão. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:41:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:03Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Estudou-se neste trabalho a preparação de LiLa(WO4)2:TR3+ (LLW:TR) nas formas de fibras monocristalinas (micro-pulling-down) e de microcristais pó cerâmico (método dos precursores poliméricos). No que se refere às fibras: a taxa de puxamento no crescimento de LiLa(1-x)Eux(WO4)2 para 0≤x≤1 é influenciada pela diferença de raio iônico do Li e das TR; a estrutura tetragonal da scheelita descreve as composições 0≤x≤1; a incorporação do Eu gera distorções na estrutura sem reduzir a simetria local do íon; uma queda de luminescência para x>0,20 é observada; e as estruturas para 0≤x≤1 foram modeladas através de simulação atomística com bastante precisão. No que se refere aos microcristais: o efeito do controle de pH na preparação de LLW:Nd 1,0 mol% foi avaliado; obteve-se aglomerados de morfologia irregular e com tamanhos médios entre 22-48 μm, cujo aumento é maior em função da temperatura do que do tempo de calcinação. No que se refere à construção experimental do diagrama de fases do sistema xLi2W2O7-(1-x)La2W2O9: confirmou-se que o LLW (formado numa região de homogeneidade de 0,48≤x≤0,55) se decompõe peritéticamente a 1000°C; a dopagem por TR influencia sua fusão; dados do crescimento, de DTA e de DRX de fibras de LLW, crescidas com composições baseadas neste diagrama, corroboram o mesmo. O processo de obtenção de fibras foi otimizado, com um excesso mínimo de 1,5 mol% de Li2W2O7. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:08/10721-9

Made available in DSpace on 2014-10-09T12:44:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:04Z (GMT). No. of bitstreams: 1 06911.pdf: 3789732 bytes, checksum: ccb970480652c70864b607ddb074f167 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:53:27Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:34Z (GMT). No. of bitstreams: 0 / Este trabalho teve por objetivo o estudo dos efeitos da radiação ionizante nas propriedades de compósitos de pó de madeira em matriz de polipropileno, utilizando o titanato de bário como agente de acoplagem e o monômero reativo diacrilato de tripropileno glicol (TPDGA). Foi utilizado como fonte de radiação o acelerador de elétrons. Foram investigadas as propriedades físicas dos compostos virgens, bem como do compósito polipropileno/pó de madeira, com e sem a adição de titanato de bário e do monômero TPDGA. Os compósitos desenvolvidos foram preparados a partir do tratamento da carga, incorporando os aditivos ao reforço pó de madeira, seguindo-se a fusão do polipropileno e a mistura dos materiais do compósito na calandra. Posteriormente foram moldados corposde- prova por injeção para serem irradiados e utilizados nos ensaios mecânicos e térmicos. Foram determinadas as propriedades mecânicas dos compostos desenvolvidos (tração, dureza, impacto e índice de fluidez), bem como as propriedades térmicas (HDT e Vicat). As composições investigadas foram polipropileno/pó de madeira, polipropileno/pó de madeira com titanato de bário, polipropileno/pó de madeira com titanato de bário e TPDGA, utilizando concentrações de 10%, 15% e 20% de pó de madeira no polipropileno. As amostras foram separadas em grupos para serem irradiadas com doses de 10kGy e 20kGy nas amostras do ensaio de tração além dessas doses foram utilizadas doses de 15kGy e 25kGy para ser observado o comportamento da amostra frente ao aumento da radiação. Estas doses foram escolhidas para mostrar que com baixas doses o material compósito apresenta reticulação, o que representa uma opção viável comercialmente. Houve uma redução do índice de fluidez para os compostos contendo pó de madeira, sendo esta redução mais efetiva na presença de TiBa. O tratamento superficial utilizando o monômero TPDGA influenciou nas amostras dos compósitos, pois este agiu como plastificante tornando as amostras mais fáceis de processar aumentando a mobilidade entre as macromoléculas, diminuindo assim a viscosidade e aumentando o índice de fluidez tanto nas amostras irradiadas como as não irradiadas. Os resultados obtidos para ensaio de resistência à tração indicam um acréscimo da propriedade, o aumento ocorreu tanto nas amostras WF/PP quanto nas amostras com TiBa e TPDGA, devido à formação de ligações cruzadas (reticulação) em decorrência da radiação. A incorporação de pó de madeira no polipropileno resultou na diminuição da resistência ao impacto. O decréscimo desta propriedade pode ter acontecido devido à presença de reforço pó de madeira que pode atuar como concentrador de tensão e como conseqüência a redução de resistência ao impacto. Houve um acréscimo na dureza dos compósitos contendo pó de madeira. O acréscimo na dureza foi significativo nos compósitos WF/PP que não foram irradiados. O acréscimo se deu principalmente nas composições de 20%WF/PP, isso porque quanto maior a quantidade de carga maior o módulo de dureza. Nas amostras irradiadas a dureza aumentou devido à oxidação da madeira frente à radiação. Observou-se que em alguns casos o aumento na dose de radiação não influenciou significativamente na variação da temperatura de deflexão térmica dos compósitos indicando que houve reticulação entre as moléculas promovido pelo TPDGA, e uma melhoria na adesão entre interfaces promovido pelo titanato. No ensaio de temperatura de amolecimento Vicat os resultados apresentados foram muito próximos ao PP puro, como os resultados não mostraram diferenças significativas, pode-se considerar a temperatura dos compósitos a mesma do PP puro. A radiação ionizante interagiu no material compósito reticulando o PP e oxidando a madeira, observando-se assim um acréscimo em algumas propriedades e o decréscimo em outras. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Três métodos de obtenção de pó de U3O8 de alta densidade foram estudados: trituração de pastilhas sInterizadas de U3O8; sinterização de grânulos de U3O8 calcinado; e sinterização de grânulos de diuranato de amônio (DUA). Testes foram conduzidos variando-se a temperatura e o tempo de calcinação do DUA, bem como o tempo de sinterização, resultando em dez lotes de U3O8. Os processos foram comparados em termos de características dos pós obtidos, rendimento granulométríco e número de etapas. O teor de impurezas, a área de superfície específica, a estequiometria, a morfologia, a densidade, a distribuição de porosidade e a identificação de fases foram considerados como parametros de caracterização dos pós. As principais conclusões mostraram que o segundo método (no qual o DUA foi calcinado a 600°C por 3h) forneceu os melhores resultados. Além disso, o terceiro método também produziu bons resultados, porém com dificuldades de manuseio do DUA. / Three preparation methods of high-density U3O8 powder have been studied: grinding of sintered U3O8 pellets, sintering of calcined U3O8 granules; and sintering of ammonium diuranate (ADU) granules. Experiments have been carried out varying ADU calcination time and temperature as well as sintering time, yielding ten U3O8 batches. Powder characteristics, granulometric yield, and number of process steps have been taken into account for comparison purposes. Impurity content, specific surface area, stoichiometry, morphology, density, porosity distribution and phase identification have been considered as parameters for powder characterization. The main conclusions show that the second method (following a 6000C/3h ADU calcination) gives the best results. Moreover, the third method gives also good results, but there were some difficulties with ADU handling.

Master of Science / Food Science Institute / Jayendra K. Amamcharla / Milk protein concentrate (MPC) powders are high-protein dairy ingredients obtained from membrane filtration processes and subsequent spray drying. MPC powders have extensive applications due to their nutritional, functional, and sensory properties. However, their flow properties, rehydration behavior, and morphological characteristics are affected by various factors such as processing, storage, particle size, and composition of the powder. Literature has shown that knowledge about the powder flowability characteristics is critical in their handling, processing, and subsequent storage. For this study, FT4 powder rheometer (FT4, Freeman Technologies, UK) was used to characterize the flowability of MPC powders during storage. This study investigated the flowability and morphological characteristics of commercial MPC powders with three different protein contents (70, 80, and 90%, w/w) after storage at 25ºC and 40ºC for 12 weeks. Powder flow properties (basic flowability energy (BFE), flow rate index (FRI), permeability, etc.) and shear properties (cohesion, flow function, etc.) were evaluated. After 12 weeks of storage at 40ºC, the BFE and FRI values significantly increased (P < 0.05) as the protein content increased from 70 to 90% (w/w). Dynamic flow tests indicated that MPC powders with high protein contents displayed higher permeability. Shear tests confirmed that samples stored at 40ºC were relatively less flowable than samples stored at 25ºC. Also, the lower protein content samples showed better shear flow behavior. The results indicated that MPC powders stored at 40ºC had more cohesiveness and poor flow characteristics than MPC powders stored at 25ºC. The circle equivalent diameter, circularity, and elongation of MPC powders increased as protein content and storage temperature increased, while the convexity decreased as protein content and storage temperature increased. Overall, the MPC powders evidently showed different flow properties and morphological characteristics due to their difference in composition and storage temperature. Literature has shown various methods for determining the solubility of dairy powders, but it requires expensive instruments and skilled technicians. The front-face fluorescence spectroscopy (FFFS) coupled with chemometrics could be used as an efficient alternative, which is commonly used as fingerprints of the various food products. To evaluate FFFS as a useful tool for the non-destructive measurement of solubility in the MPC powders, commercially procured MPC powders were stored at two temperatures (25 and 40ºC) for 1, 2, 4, 8, and 12 weeks to produce powders with different rehydration properties, which subsequently influenced their fluorescence spectra. The spectra of tryptophan and Maillard products were recorded and analyzed with principal components analysis. The solubility index and the relative dissolution index (RDI) obtained from focused beam reflectance measurement was used to predict solubility and dissolution changes using fluorescence spectra of tryptophan and Maillard products. The solubility index and RDI showed that the MPC powders had decreased solubility as the storage time and temperature increased. The results suggest that FFFS has the potential to provide rapid, nondestructive, and accurate measurements of rehydration behavior in MPC powders. Overall, the results indicated that solubility and dissolution behavior of MPC powders were related to protein content and storage conditions that could be measured using FFFS.

A method has been developed to produce grain sizes as low as 5µm in β-CuAlNi alloys and the effect of grain size on mechanical and strain-memory properties was studied. The thermomechanical treatment procedure involved two. sequential warm working and recrystallization steps at 600° C and 800° C respectively on eutectoid alloys. Three different eutectoid alloys, two with Ms temperature of around 0°C and one with Ms = 220° C were used for the present studies. Even at fine grain sizes, the specimens produced were of single β- phase type without any second phases. Two-stage characteristic stress-strain curves were obtained for most of the specimens in both the strain memory and pseudoelastic states. It was found that the ultimate tensile strength and strain to failure increased with decreasing grain size according to a Hall-Petch relationship down to a grain size of 5µm with the exception of one alloy. Fracture strengths of 1,200 MPa and fracture strains of 10% could be obtained. It was found that the major recovery mode, whether pseudoelastic or strain memory, did not have any significant effect on the total recovery obtained. Recovery properties were not affected significantly by decreasing grain size. Approximately 86% recovery could be obtained for an initial applied strain of 5% at a grain size of around 10µm. Grain refinement increased the fatigue life considerably, possibly due to high ultimate fracture strength and ductile fracture mode. Fatigue life of 275,000 cycles could be obtained for an applied stress of 330 MPa and a steady state strain of 0.6%. Most of the fractures are due to intergranular-type brittle fracture. At fine grain sizes, transgranular-type brittle fracture and microvoid coalescence-type ductile fracture dominated the fracture mode. Oxygen segregation at grain boundaries is the possible explanation for the different mechanical properties shown by different alloys in the present work by being a major factor in causing intergranular-type fracture. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis (Ph. D. (Physics)) -- University of Limpopo, 2016. / Single and double doped nanometric powders of Single and double doped nanometric powders of titanium dioxide (TiO2) were synthesised by the sol-gel process using titanium isopropoxide (TTIP) as the precursor. For comparison, an undoped sample was also prepared. The metal dopants, Ag and Cu, were used at doping levels of 5% molar weight. The samples were dried at 100°C in air and post annealing was done at 300°C, 600°C, 900°C and 1100°C. Structural characterisation of the samples was carried out by X-ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Energy dispersive X-ray Spectrometry (EDS) techniques. Most samples annealed at the 300°C temperature (and lower) revealed the predominantly-anatase phase, while those annealed at 900°C and above were rutile-only. The double-doped powder that was annealed at 300°C was found to be constituted by anatase and brookite phases (with the dopants incorporated into the TiO2 matrix), and the one annealed at 600°C was a mixture of brookite and rutile. The results suggest that multiple doping of titania may favour a two-phase structure at lower temperatures than singly-doped powders. The co-existence of brookite with anatase is believed to be responsible for the enhancement of anatase to rutile transformation in the double-doped sample. UV-visible (UV-vis) and Photoluminescence (PL) measurements were also carried out to study the optical properties of the TiO2 nanoparticles. This revealed the active PL band at around 440 nm. By narrowing the band gap, the double-doped powders that exhibited the brookite phase, again showed improved visible light photo absorption over the other samples, with a significant shift of the absorption edge to shorter wavelengths. Further, PL spectra revealed a change in PL intensity with phase change, as well as the presence of exciton energy levels at the base of the conduction band. The changes in the electrical conductivities of representative anatase and rutile TiO2 nanopowders upon exposure to water-vapour, ammonia (NH3) and hydrogen (H2) were also investigated. Sensing measurements for water-vapour was done at room temperature for various humidity levels ranging from 5.4% RH to 88.4% RH. The detection of NH3 and H2 gases were carried out at temperatures extending from room temperature to 350°C and over concentration ranges of 25 sccm to 500 sccm and 15 v sccm to 200 sccm respectively. The gas-sensing results show that the sol-gel fabricated TiO2 nanoparticles (particularly in anatase form), has excellent fast and stable dynamic responses to humidity, NH3 and H2. They feature good sensitivities, even at a low operating temperatures. However, acceptor behaviour, for which there was a conductivity switch from n-type to p-type, was recorded for the Ag-doped rutile powders at operating temperatures of 300ºC and 350ºC. Overall, the double-doped sample annealed at 300ºC was deemed the most promising candidate for gassensing. (TiO2) were synthesised by the sol-gel process using titanium isopropoxide (TTIP) as the precursor. For comparison, an undoped sample was also prepared. The metal dopants, Ag and Cu, were used at doping levels of 5% molar weight. The samples were dried at 100°C in air and post annealing was done at 300°C, 600°C, 900°C and 1100°C. Structural characterisation of the samples was carried out by X-ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Energy dispersive X-ray Spectrometry (EDS) techniques. Most samples annealed at the 300°C temperature (and lower) revealed the predominantly-anatase phase, while those annealed at 900°C and above were rutile-only. The double-doped powder that was annealed at 300°C was found to be constituted by anatase and brookite phases (with the dopants incorporated into the TiO2 matrix), and the one annealed at 600°C was a mixture of brookite and rutile. The results suggest that multiple doping of titania may favour a two-phase structure at lower temperatures than singly-doped powders. The co-existence of brookite with anatase is believed to be responsible for the enhancement of anatase to rutile transformation in the double-doped sample. UV-visible (UV-vis) and Photoluminescence (PL) measurements were also carried out to study the optical properties of the TiO2 nanoparticles. This revealed the active PL band at around 440 nm. By narrowing the band gap, the double-doped powders that exhibited the brookite phase, again showed improved visible light photo absorption over the other samples, with a significant shift of the absorption edge to shorter wavelengths. Further, PL spectra revealed a change in PL intensity with phase change, as well as the presence of exciton energy levels at the base of the conduction band. The changes in the electrical conductivities of representative anatase and rutile TiO2 nanopowders upon exposure to water-vapour, ammonia (NH3) and hydrogen (H2) were also investigated. Sensing measurements for water-vapour was done at room temperature for various humidity levels ranging from 5.4% RH to 88.4% RH. The detection of NH3 and H2 gases were carried out at temperatures extending from room temperature to 350°C and over concentration ranges of 25 sccm to 500 sccm and 15 v sccm to 200 sccm respectively. The gas-sensing results show that the sol-gel fabricated TiO2 nanoparticles (particularly in anatase form), has excellent fast and stable dynamic responses to humidity, NH3 and H2. They feature good sensitivities, even at a low operating temperatures. However, acceptor behaviour, for which there was a conductivity switch from n-type to p-type, was recorded for the Ag-doped rutile powders at operating temperatures of 300ºC and 350ºC. Overall, the double-doped sample annealed at 300ºC was deemed the most promising candidate for gassensing.

Esta tesis presenta un conjunto original de procedimientos para la síntesis de nanoestructuras de TiO2 y ZnO por biomimetización de membranas de cáscara de huevo obteniendo materiales valiosos para fotovoltaica como se muestra en su evaluación de rendimiento como ánodo en células solares sensibilizadas por colorante. "El manuscrito está dividido en 7 capítulos. En el primer capítulo, titulado Introducción, se presentan las bases teóricas para la comprensión de los procesos de biomimetización, membranas de cáscara de huevo, síntesis de ZnO y TiO2, y células solares sensibilizadas por colorantes (DSSC). Después del capítulo introductorio, el Capítulo 2 revela los objetivos generales y específicos de esta investigación. Posteriormente, el Capítulo 3 describe el procedimiento experimental utilizado para las síntesis y caracterizaciones de ZnO y TiO2, así como el procedimiento utilizado en el ensamblaje y la caracterización de las células fotovoltaicas. En el capítulo 4 se presentan y discuten los resultados obtenidos con las síntesis y la aplicación de los polvos como fotodoles en DSSC. En este capítulo, hemos decidido subdividirlo en secciones específicas para explicar cuestiones científicas específicas sobre el tema. En el capítulo 5 se presentan las conclusiones del estudio en vista de los diferentes aspectos: obtención de TiO2 biomimético y ZnO, diferencias entre los polvos sintetizados por biomimetización de las membranas de cáscara de huevo, y la caracterización de las células construidas con los polvos biomiméticos. / Esta tesi presenta un conjunt original de procediments per a la síntesi de nanoestructuras de TiO2 i ZnO per biomimetización de membranes de corfa d'ou obtenint materials valuosos per a fotovoltaica com es mostra en la seua avaluació de rendiment com a ànode en cèl·lules solars sensibilitzades per colorant. &#34;El manuscrit està dividit en 7 capítols. En el primer capítol, titulat Introducció, es presenten les bases teòriques per a la comprensió dels processos de biomimetización, membranes de corfa d'ou, síntesi de ZnO i TiO2, i cèl·lules solars sensibilitzades per colorants (DSSC) . Després del capítol introductori, el Capítol 2 revela els objectius generals i específics d'esta investigació. Posteriorment, el Capítol 3 descriu el procediment experimental utilitzat per a les síntesis i caracteritzacions de ZnO i TiO2, així com el procediment utilitzat en l'acoblament i la caracterització de les cèl·lules fotovoltaiques. En el capítol 4 es presenten i discutixen els resultats obtinguts amb les síntesis i l'aplicació de les pols com fotodoles en DSSC. En este capítol, hem decidit subdividir-ho en seccions específiques per a explicar qüestions científiques específiques sobre el tema. En el capítol 5 es presenten les conclusions de l'estudi en vista dels diferents aspectes: obtenció de TiO2 biomimético i ZnO, diferències entre les pols sintetitzats per biomimetización de les membranes de corfa d'ou, i la caracterització de les cèl·lules construïdes amb les pols biomiméticos. / This thesis introduces an original set of procedures for the Synthesis of ZnO and TiO2 nanostructures by biomimetization of eggshell membranes obtaining valuable materiales for photovoltaic as shown on their performance evaluation as anode in Dye-Sensitized Solar Cells". The manuscript is divided into 7 chapters. In the first chapter, entitled Introduction, it is presented the theoretical bases for the understanding of the biomimetization processes, eggshell membranes, ZnO and TiO2 syntheses, and dye-sensitized solar cells (DSSC). After the introductory chapter, Chapter 2 reveals the general and specific objectives of this research. Subsequently, Chapter 3 describes the experimental procedure used for the syntheses and characterizations of ZnO and TiO2 as well as the procedure used in the assembly and characterization of the photovoltaic cells. In chapter 4 are presented and discussed the results obtained with the syntheses and application of the powders as photoanodes in DSSC. In this chapter, we have chosen to subdivide it into specific sections to explain specific scientific issues on the subject. In chapter 5 the conclusions of the study are presented in view of the different aspects: obtaining ZnO and biomimetic TiO2, differences between the powders synthesized by biomimetization of eggshell membranes, and the characterization of the cells constructed with the biomimetic powders. / Camaratta, R. (2018). Synthesis Of ZnO and TiO2 By Biomimetization Of Eggshell Membranes And Its Evaluation As Anode In Dye-Sensitized Solar Cells [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113416 / TESIS