Este trabalho apresenta o estudo de vidros e vitro-cerâmicas oxifluoretos de composição PbGeO3 CdF2 PbF2 (Fluorgermanatos de cádmio e chumbo) e de blendas poliméricas formadas entre o eletrólito polimérico PEO:LiC104 (Poli-óxido de eltileno com perclorato de lítio) e o polímero condutor POMA (Poli-orto metoxianilina). Foram utilizadas as técnicas de ressonância magnética nuclear (RMN), ressonância paramagnética eletrônica (RPE), calorimetria exploratória diferencial (DSC) e impedância complexa. Dentre várias aplicações, estes materiais são importantes devido ao grande potencial como eletrólitos sólidos. Este estudo tem como principal objetivo esclarecer os mecanismos de transporte iônico do flúor e do lítio. Os resultados mostraram que os mecanismos da condução iônica nos vítreos oxifluoretos são caracterizados diferentemente em cada região de temperatura estudada. Em baixas temperaturas (T<300K), o processo de relaxação foi atribuído às excitações de baixas-frequências dos modos desordenados. Acima de 300K, porém abaixo da temperatura de transição vítrea, os movimentos do flúor modulam as interações dipolares F-F. As vitro-cerâmicas, obtidas através de tratamentos térmicos dos vidros de oxifluoretos, são materiais compósitos onde nano ou micro-cristais estão dispersos na matriz vítrea. Os resultados de RMN mostraram no intervalo 100 800K, pelo menos três processos de relaxação, que foram associados com (i) movimentos difusionais dos íons de flúor nos cristais de β-PbF2, (ii) mobilidade iônica na matriz vítrea e (iii) íons de flúor de baixa mobilidade (provavelmente PbGeO3-xFx). Os resultados de RMN 1H mostraram que os tempos de correlação associados aos movimentos das macromoléculas nas blendas poliméricas xii são comparáveis aos encontrados na literatura para o PEO/PMMA. A fim de se garantir resultados reprodutíveis, um cuidadoso método de preparação deve ser seguido, assegurando a estabilidade química e a homogeneidade da blenda / This work reports the study of oxifluorides glasses and glass-ceramics of composition PbGeO3 CdF2 PbF2 (Lead cadmium fluorgermanate) and blends formed by the polymer electrolyte PEO:LiC104 (poly etilene oxide and lithium perclorate) and the conducting polymer POMA (poly ortho methox aniline). Nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and complex impedance techniques were used. Among several applications, these materiais are important as solid electrolytes. The main objective of this work is to study the fluor or lithium ionic transport mechanisms. Results show that the ionic conduction mechanism in oxifluoride glass systems is characteristic of each temperature region. In low temperatures (T < 300K), the relaxation processes were attributed to low-frequency excitations of disorder modes intrinsic to the glassy state of mater. Above 300 K and below of the glass transition temperature the fluorine motions modulate the dipolar F-F interactions. The glasscerarnics, produced form their respective glasses, are composite materiais where nano- or micro-crystals are dispersed on the glassy matrix. The NMR results, in the range 100-800 K, evidenced three separate relaxation process: (i) diffusional motions of fluorine ions in β-PbF2 crystals; (ii) fluorine mobility in the glass matrix and (iii) fluorine ions of low mobility (probably PbGeO3-xFx). The i ll NMR results shown that the correlation time values, associated to the polymeric chains motion in polymer blends, are comparable to those found for PEO/PMMA. In order to get reproducible results, a careful sample preparation process must be undertaken to ensure chemical stability and blend homogeneity.

Este trabalho apresenta um estudo dos mecanismos de transporte iônico nos vidros fluorsilicatos de cádmio e chumbo de composição 40SiO2 40PbF2 20CdF2, e nos vidros boratos contendo LiF de composição 50B2O3 10PbO 40LiF. Estes materiais são importantes pela sua potencial utilização em dispositivos ópticos e eletrólitos sólidos. No vidro borato 50B2O3 10PbO 40LiF o estudo da forma de linha do 7Li mostrou que esta é influenciada tanto por interações dipolares quanto por quadrupolares. O estudo de RMN revelou que há dois F- presentes neste vidro, um deles em vizinhaças de Pb (F- incorporados à rede vítrea substituindo o oxigênio do grupo PbO), e o outro em vizinhanças de Li. A forma de linha de RMN dependente da temperatura para o lítio e para o flúor, e seus tempos de relaxação, exibem as características qualitativas associadas com a alta mobilidade do 7Li e do 19F neste sistema. Este estudo também mostrou que, neste vidro, tanto o Li+ como o F- contribuem para a condutividade medida, sendo que o 7Li é móvel a temperaturas mais baixas (a partir de 250 K), e o 19F começa a se mover em temperaturas mais altas (a partir de 400 K). No vidro 40SiO2 40PbF2 20CdF2, os resultados de RMN mostraram a alta mobilidade do flúor e evidenciaram duas dinâmicas diferentes dos íons flúor. Os dados da relaxação do flúor revelaram um máximo da taxa de relaxação spin-rede abaixo da temperatura de transição vítrea (Tg), indicando que a mobilidade do flúor, neste vidro, é comparável àquelas encontradas em condutores iônicos rápidos / This work presents a study of the ionic transport mechanisms in lead-cadmium fluorosilicate glasses, of composition 40SiO2 40PbF2 20CdF2, and in borate glasses containing LiF, of composition 50B2O3 10PbO 40LiF. These materiais are important due to theirs high potential applicability in optic devices and in solid electrolytes. In the borate glass 50B2O3 10PbO 40LiF, the line shape study of 7Li shows an influence of the dipolar and quadrupolar interactions. The NMR results showed that there are two kinds of F- ions in this glass, one in the Pb vicinity (F- in the glass lattice, in substitution of the PbO oxygen), and the other in the Li vicinity. The NMR line shape depends on the temperature for the 7Li and 19F atoms, and their relaxation times reflect qualitative features related to the high mobility of there nuclei. Also, this study shows that, in this glass, both, 7Li and 19F, play an important role in the electric conductivity. The 7Li is mobile for low temperatures (from 250 K), while the 19F is mobile for high temperatures (from 400 K). In the 40SiO2 40PbF2 20CdF2 glass, the NMR results showed the high mobility of the fluorine ions, indicating two different dynamics of those nuclei. The relaxation data of the 19F presented a spin-lattice relaxation rate maximum below the glass transition temperature (Tg, indicating that the 19F mobility in this glass is comparable to that of rapid ionic conducting glasses

Este trabalho apresenta o estudo de vidros e vitro-cerâmicas oxifluoretos de composição PbGeO3 CdF2 PbF2 (Fluorgermanatos de cádmio e chumbo) e de blendas poliméricas formadas entre o eletrólito polimérico PEO:LiC104 (Poli-óxido de eltileno com perclorato de lítio) e o polímero condutor POMA (Poli-orto metoxianilina). Foram utilizadas as técnicas de ressonância magnética nuclear (RMN), ressonância paramagnética eletrônica (RPE), calorimetria exploratória diferencial (DSC) e impedância complexa. Dentre várias aplicações, estes materiais são importantes devido ao grande potencial como eletrólitos sólidos. Este estudo tem como principal objetivo esclarecer os mecanismos de transporte iônico do flúor e do lítio. Os resultados mostraram que os mecanismos da condução iônica nos vítreos oxifluoretos são caracterizados diferentemente em cada região de temperatura estudada. Em baixas temperaturas (T<300K), o processo de relaxação foi atribuído às excitações de baixas-frequências dos modos desordenados. Acima de 300K, porém abaixo da temperatura de transição vítrea, os movimentos do flúor modulam as interações dipolares F-F. As vitro-cerâmicas, obtidas através de tratamentos térmicos dos vidros de oxifluoretos, são materiais compósitos onde nano ou micro-cristais estão dispersos na matriz vítrea. Os resultados de RMN mostraram no intervalo 100 800K, pelo menos três processos de relaxação, que foram associados com (i) movimentos difusionais dos íons de flúor nos cristais de β-PbF2, (ii) mobilidade iônica na matriz vítrea e (iii) íons de flúor de baixa mobilidade (provavelmente PbGeO3-xFx). Os resultados de RMN 1H mostraram que os tempos de correlação associados aos movimentos das macromoléculas nas blendas poliméricas xii são comparáveis aos encontrados na literatura para o PEO/PMMA. A fim de se garantir resultados reprodutíveis, um cuidadoso método de preparação deve ser seguido, assegurando a estabilidade química e a homogeneidade da blenda / This work reports the study of oxifluorides glasses and glass-ceramics of composition PbGeO3 CdF2 PbF2 (Lead cadmium fluorgermanate) and blends formed by the polymer electrolyte PEO:LiC104 (poly etilene oxide and lithium perclorate) and the conducting polymer POMA (poly ortho methox aniline). Nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and complex impedance techniques were used. Among several applications, these materiais are important as solid electrolytes. The main objective of this work is to study the fluor or lithium ionic transport mechanisms. Results show that the ionic conduction mechanism in oxifluoride glass systems is characteristic of each temperature region. In low temperatures (T < 300K), the relaxation processes were attributed to low-frequency excitations of disorder modes intrinsic to the glassy state of mater. Above 300 K and below of the glass transition temperature the fluorine motions modulate the dipolar F-F interactions. The glasscerarnics, produced form their respective glasses, are composite materiais where nano- or micro-crystals are dispersed on the glassy matrix. The NMR results, in the range 100-800 K, evidenced three separate relaxation process: (i) diffusional motions of fluorine ions in β-PbF2 crystals; (ii) fluorine mobility in the glass matrix and (iii) fluorine ions of low mobility (probably PbGeO3-xFx). The i ll NMR results shown that the correlation time values, associated to the polymeric chains motion in polymer blends, are comparable to those found for PEO/PMMA. In order to get reproducible results, a careful sample preparation process must be undertaken to ensure chemical stability and blend homogeneity.

Este trabalho apresenta um estudo dos mecanismos de transporte iônico nos vidros fluorsilicatos de cádmio e chumbo de composição 40SiO2 40PbF2 20CdF2, e nos vidros boratos contendo LiF de composição 50B2O3 10PbO 40LiF. Estes materiais são importantes pela sua potencial utilização em dispositivos ópticos e eletrólitos sólidos. No vidro borato 50B2O3 10PbO 40LiF o estudo da forma de linha do 7Li mostrou que esta é influenciada tanto por interações dipolares quanto por quadrupolares. O estudo de RMN revelou que há dois F- presentes neste vidro, um deles em vizinhaças de Pb (F- incorporados à rede vítrea substituindo o oxigênio do grupo PbO), e o outro em vizinhanças de Li. A forma de linha de RMN dependente da temperatura para o lítio e para o flúor, e seus tempos de relaxação, exibem as características qualitativas associadas com a alta mobilidade do 7Li e do 19F neste sistema. Este estudo também mostrou que, neste vidro, tanto o Li+ como o F- contribuem para a condutividade medida, sendo que o 7Li é móvel a temperaturas mais baixas (a partir de 250 K), e o 19F começa a se mover em temperaturas mais altas (a partir de 400 K). No vidro 40SiO2 40PbF2 20CdF2, os resultados de RMN mostraram a alta mobilidade do flúor e evidenciaram duas dinâmicas diferentes dos íons flúor. Os dados da relaxação do flúor revelaram um máximo da taxa de relaxação spin-rede abaixo da temperatura de transição vítrea (Tg), indicando que a mobilidade do flúor, neste vidro, é comparável àquelas encontradas em condutores iônicos rápidos / This work presents a study of the ionic transport mechanisms in lead-cadmium fluorosilicate glasses, of composition 40SiO2 40PbF2 20CdF2, and in borate glasses containing LiF, of composition 50B2O3 10PbO 40LiF. These materiais are important due to theirs high potential applicability in optic devices and in solid electrolytes. In the borate glass 50B2O3 10PbO 40LiF, the line shape study of 7Li shows an influence of the dipolar and quadrupolar interactions. The NMR results showed that there are two kinds of F- ions in this glass, one in the Pb vicinity (F- in the glass lattice, in substitution of the PbO oxygen), and the other in the Li vicinity. The NMR line shape depends on the temperature for the 7Li and 19F atoms, and their relaxation times reflect qualitative features related to the high mobility of there nuclei. Also, this study shows that, in this glass, both, 7Li and 19F, play an important role in the electric conductivity. The 7Li is mobile for low temperatures (from 250 K), while the 19F is mobile for high temperatures (from 400 K). In the 40SiO2 40PbF2 20CdF2 glass, the NMR results showed the high mobility of the fluorine ions, indicating two different dynamics of those nuclei. The relaxation data of the 19F presented a spin-lattice relaxation rate maximum below the glass transition temperature (Tg, indicating that the 19F mobility in this glass is comparable to that of rapid ionic conducting glasses

No description available.

Studies on nuclear technology have been ongoing since nuclear power became uniquely important to meet climate change goals while phasing out fossil fuels. Research on the fluoride salt cooled high temperature reactor (FHR), which is funded by the United States Department of Energy (DOE), has developed smoothly with the ultimate goal of a 2030 deployment. One challenge presented by FHR is that the primary coolant salt can acquire contamination from fuel failure and moisture leaking into the system. If contamination happens, it will result in a low concentration of fission products, fuel, transuranic materials and oxide impurities in the coolant. These impurities will then affect the properties of the molten salt in the long term and need to be removed without introducing new impurities. Most of the research conducted recently has focused on impurity separation in chloride molten salts. More research urgently needs to be conducted to study the impurity separation method for the fluoride molten salts. In this study, the La₂O₃-LiF-NaF-KF (La₂O₃-FLiNaK) system is used to demonstrate impurity separation in molten fluoride salt. Since lanthanum oxide needs to be dissolved in the fluoride molten salt and studies in this field are still not complete, the solubility of lanthanum oxide in FLiNaK have been measured at different temperatures to obtain the temperature-dependent solubility and understand the corresponding dissolution mechanisms first. In the solubility related experiments, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is utilized to analyze the concentration of lanthanum ions in the molten FLiNaK salt, while X-ray powder diffraction (XRD) was applied to determine the phase patterns of molten salt. Second, electrochemical experiments with tungsten and graphite as working electrodes were conducted individually to demonstrate the separation of the dissolved oxide from the salt. When the tungsten working electrode was applied, the lanthanum ions were reduced to lanthanum metal at the tungsten cathode, while the fluorine ions reacted with the tungsten anode to form tungsten fluoride. In the experiments, the production of tungsten fluoride could lead to increasing current in the cell, even overload. Moreover, theoretically, tungsten fluoride WF4 is soluble in the fluoride salt thus introducing new impurities. All these issues make tungsten not the best choice when applied to the separation of oxygen ions. Therefore, another common working electrode graphite is used. It not only has all the advantages of tungsten, but also has good performance on separation of oxygen ions. When the graphite electrode was applied, the lanthanum ions were separated in the form of lanthanum carbide (LaC₂), while the oxygen ions can be removed in the form of carbon dioxide (CO₂) or carbon monoxide (CO). In addition, only graphite was consumed during the whole separation process, which is why the graphite anode electrode is called the “sacrificial electrode”. Third, First Principle Molecular Dynamics (FPMD) simulations with Vienne Ab initio Simulation Package (VASP) was conducted to study the properties of the fluoride molten salt. In this study, the structure information and enthalpy of formation were obtained. Generally, the simulation process can be divided into four steps: (1) the simulation systems are prepared by packing ions randomly via Packmol package in the simulation cell; (2) an equilibrium calculation is performed to pre-equilibrate the systems; (3) FPMD simulations in an NVT ensemble are implemented in VASP; (4) based on the FPMD simulations results, the first peak radius and the first-shell coordination number were evaluated with partial radial distribution function (PRDF) analysis to determine the statistics of molten salt structure information, while the transport properties, e.g., the self-diffusion coefficient was calculated according to the function of mean square displacement (MSD) of time generated by the Einstein-Smoluchowshi equation. The viscosity and ionic conductivity were obtained by combining the self-distribution coefficient with the Einstein-Stokes formula and Nernst-Einstein equation. / Master of Science / With the fast development of modern society and economy, more and more energy is urgently needed to meet the growth of industry. Since the traditional energy, such as nature gas, coal, has limited storage and not sustainable, nuclear energy has attracted much attention in the past few decades. Although lots of study has been conducted by thousands of researchers which has attributed to application of nuclear power, there are still some concerns in this field, among which, impurities removal is the most difficult part. Fluoride salt cooled high temperature reactor (FHR) is one of the most promising Gen IV reactor types. As the name indicates, molten salt is the coolant to serve as the heat exchanger intermedium. In addition, it’s inevitable that fission products, i.e. lanthanum, moisture, would leak into the coolant pipe, thus affect the molten salt properties, even degrade reactor performance, therefore, those impurities must be removed without introducing new impurities. In this study, the La₂O₃-LiF-NaF-KF (La₂O₃-FLiNaK) system is used to demonstrate impurity separation into molten fluoride salt. First, solubility of lanthanum oxide in FLiNaK has been measured at different temperatures to understand its dissolution mechanisms. Then, electrochemical experiments with tungsten and graphite as working electrodes were conducted individually to demonstrate the separation of the dissolved oxide from the salt. It has been concluded that tungsten performed well to separate La3+, while failed in the separation of O2-. However, graphite working electrode has succeeded in the removal of La³⁺ and O²⁻. Finally, molecular dynamic simulation with first principle was also conducted to further understand the local structure and heat of formation in the molten FLiNaK and La₂O₃-FLiNaK salt.

BaSIC, which stands for Bioclastic and Shape-preserving Inorganic Conversion, is shape-preserving chemical conversion process of biological (or man-made) silica structures for producing complex 3-D microscale structures. This dissertation reports the BaSIC reaction of halide gases (i.e., TiF4, ZrF4, and ZrCl4) with 3-D silica structures, (i.e., diatom frustules, silicified direct-write assembly scaffolds, and Stöber silica spheres) to produce titania and zirconia replicas of the original 3-D structures. The kinetics of reaction of silica with titanium tetrafluoride gas is analyzed by using a novel HTXRD reaction chamber, nitrogen adsorption, and transmission electron microscope (TEM). The crystal structure and the temperature-induced phase transformation (from the room temperature hexagonal R-3c structure to the higher temperature cubic Pm3m structure) of polycrystalline TiOF2 that was synthesized through metathetic reaction of silica with TiF4(g) is reported. Additionally, potential applications of the converted titania diatom frustules (i.e., as a fast micron-sized ethanol sensor, and as a pesticide hydrolyzing agent) are also demonstrated in this work.

In der vorliegenden Arbeit wurden unter Anwendung unterschiedlicher Präparationstechniken vanadiumdotierte Metalloxide bzw. –oxofluoride synthetisiert, umfassend charakterisiert und in katalytischen, selektiven Oxidationsreaktionen (ODH von Propan und Methanoloxidation) getestet. Die Festkörper- und oberflächenchemischen Eigenschaften wurden generell mittels CHN-Analyse, ICP-OES, XRD, Raman-, FTIR-, MAS-NMR- und ESR-Spektroskopie, Py-PAS, TPD und Tieftemperatur-Stickstoffadsorption untersucht. Ergänzend kamen an ausgewählten Proben der temperaturprogrammierte Sauerstoffisotopenaustausch und Adsorptionsuntersuchungen von Methanol zum Einsatz. Als katalytische Testreaktionen dienten die oxidative Dehydrierung von Propan und die selektive Methanoloxidation. Unabhängig von der angewendeten Synthesemethode zeigte sich, dass die Festkörpereigenschaften sowohl durch den Vanadiumgehalt, als auch wesentlich durch die Art des Wirtsgitters beeinflusst werden. Es konnte nachgewiesen werden, dass eine hohe Sauerstoffaustauschaktivität und das Vorhandensein Brønsted-saurer Zentren auf den Katalysatoroberflächen die Aktivierung der Edukte in den hier untersuchten katalytischen Reaktionen begünstigen. In Bezug auf die Selektivität zu den Zielprodukten Propen bzw. Formaldehyd sind diese Eigenschaften allerdings nachteilig, da an derartigen Zentren immer die Produkte der Totaloxidation (CO und CO2) gebildet werden. Besonders bemerkenswert ist das Verhalten der vanadiumdotierten Aluminiumoxofluoride. Diese Phasen wurden mit einer neuen Methode synthetisiert und enthalten fast ausschließlich Lewis-saure Zentren. Die Matrix wird zudem maßgeblich durch die Fluoridionen bestimmt, sodass die Sauerstoffmobilität und –austauschaktivität sehr gering sind. Dadurch reagieren sie, trotz einer relativ hohen katalytischen Aktivität, außerordentlich selektiv in den hier untersuchten selektiven Oxidationsreaktionen. / In this thesis, vanadium containing metal oxides and oxyfluorides were prepared, thoroughly characterised and tested as catalysts in selective oxidation reactions. Bulk and surface properties of all samples were studied by means of CHN-analysis, ICP-OES, XRD, Raman-, FTIR-, MAS-NMR- und ESR-spectroscopy, Py-PAS, TPD and BET-adsorption. Moreover, the oxygen isotope exchange behaviour and the methanol adsorption properties of selected samples were analysed in order to correlate the surface properties with the catalytic behaviour of the materials. Irrespective of the preparation technique applied, the properties of the solids strongly depend on the host lattice as well as on the vanadium content. It has been clearly revealed that a high oxygen exchange activity and the presence of Brønsted acid sites on the catalyst surface promote the activation of the educts in selective oxidation reactions. The enhanced activity, however, is generally accompanied by a low selectivity towards the desired products propylene and formaldehyde, respectively. The low selectivity is caused by the high concentration of catalytically active sites leading to the formation of carbon oxides as total oxidation products of propane and methanol. A very promising catalytic behaviour was observed with vanadium-doped aluminium oxyfluorides. The oxyfluorides were prepared by a new method and contain almost exclusively Lewis-acid sites. The matrix is mainly determined by the fluoride anions resulting in a reduced oxygen mobility and exchange activity. Hence, the vanadium-doped aluminium oxyfluorides exhibit a relatively high catalytic activity accompanied by an excellent selectivity in the oxidation reaction of propane and methanol.

科学研究費補助金 研究種目:基盤研究(C)(2) 課題番号:09650806 研究代表者:藤澤 敏治 研究期間:1997-1998年度