There has been an increase in the interest in fluoride materials over the last decade. This interest has focused on multiferroic materials and kagome lattices, to name but a few areas. This thesis focuses on the synthesis and crystallographic characterisation of selected transition metal fluorides and oxyfluorides. Work is presented on the tetragonal tungsten bronze solid solutions of KₓFeF₃, where x = 0.58 and x ≈ 0.5, and the copper analogue, K₃Cu₃Fe₂F₁₅; the kagome structure of Cs₂ZrCu₃F₁₂; and hydrothermal reactions using vanadium, manganese, or molybdenum as the transition metals in the formation of new fluorides and oxyfluorides. The tetragonal tungsten bronze compounds KₓFeF₃ (x = 0.58 and x ≈ 0.5) are both tetragonal at 500 K. In the variant with the lower K-content, there is a clear phase separation into two tetragonal phases even at this temperature. The K₀.₅₈FeF₃ sample separates into two distinct phases below 340 K to possess one tetragonal and one orthorhombic phase. Then at roughly 300 K, both samples undergo a phase transition where the tetragonal phase in the P4/mbm space group in K₀.₅₈FeF₃ changes to an orthorhombic phase with a larger unit cell; and the tetragonal phase in P4₂bc for the K₀.₅FeF₃ sample changes to the same orthorhombic model, whilst the P4/mbm model remains unchanged. The evolution of the lattice parameters and phase fractions is studied in detail using synchrotron powder X-ray diffraction (sPXRD). The kagome structure investigated, Cs₂ZrCu₃F₁₂, possesses the “ideal” kagome lattice at room temperature, but previous work has suggested that there is a phase transition at 225 K. The two structures are determined by single crystal X-ray diffraction at 300 K and 125 K. Variable temperature sPXRD studies are performed between these two temperature ranges to determine the phase evolution as a function of temperature. The structure changes from a rhombohedral to a monoclinic phase at low temperature. This is the result of the buckling of the kagome layers at the phase transition. The Zr⁴⁺ ion changes from 6 to 7 coordinate and this is seen as the main driving force for the distortion of the kagome layer from its “ideal” planar arrangement. ii The phase transition is first-order as seen from the electrical impedance measurements. The hydrothermal reactions presented reveal seven new materials and their crystal structures. Sr₂V₂F₁₀·H₂O is new and found to be isostructural to Sr₂Fe₂F₁₀·H₂O. BaVO₂F₃ is a cubic material that is potentially piezoelectric. Two hybrid organic inorganic manganese compounds are reported. The ladder structure (C₃N₂H₅)[Mn₂F₆(H₂O)₂] crystallises in a polar space group and shows promise as a candidate for multiferroic studies. The second hybrid material, (C₇NH₁₆)₂[MnF₅(H₂O)]·2H₂O, crystallises in a centrosymmetric space group. The Mo hybrid materials are all centrosymmetric and possess isolated molybdenum-centred monomeric or dimeric octahedral units.

Made available in DSpace on 2014-10-09T12:41:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:16Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:44:29Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:22Z (GMT). No. of bitstreams: 1 07114.pdf: 5950239 bytes, checksum: a45c843d71dddc5fe0b565d5be615211 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:41:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:16Z (GMT). No. of bitstreams: 0 / Investigações dos sistemas binários LiF-BiF3 e NaF-BiF3 foram realizadas com o objetivo de esclarecer o comportamento térmico e os equilíbrios de fase destes sistemas e das suas fases intermediárias, um requisito importante para a obtenção de cristais de alta qualidade. Amostras de toda a faixa de composições (0 a 100 mol% BiF3) de ambos os sistemas foram analisadas em ensaios de análise térmica diferencial (DTA) e termogravimetria (TG), e também de calorimetria exploratória diferencial (DSC). Algumas composições específicas foram selecionadas para difração de raios-X para complementação dos dados experimentais. Devido à grande vulnerabilidade do BiF3 à contaminação por oxigênio, sua volatilidade e propensão a danificar peças de metal quando aquecido, foi necessário determinar as condições ótimas para os ensaios de análise térmica antes de investigar os sistemas em si. As relações de fase no sistema LiF-BiF3 foram completamente elucidadas e um diagrama de fases foi proposto e avaliado teoricamente mediante o software comercial Factsage. O diagrama em si consiste em um sistema peritético simples, no qual o único composto interno, o LiBiF4 se decompõe em LiF mais uma fase líquida. O sistema NaF-BiF3 não pôde ser completamente elucidado, sendo que as relações de fase do lado pobre em NaF (> 50% BiF3) ainda não são conhecidas. No lado rico em NaF, entretanto, identificou-se a possível decomposição peritectóide do composto NaBiF4. Em ambos os sistemas, foram observadas estruturas cristalográficas discrepantes daquelas da literatura para os compostos mistos, LiBiF4 , NaBiF4 e uma solução sólida de NaF e BiF3 chamada de fase I. As estruturas observadas experimentalmente permanecem desconhecidas e explicações para as discrepâncias foram propostas. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:44:29Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:22Z (GMT). No. of bitstreams: 1 07114.pdf: 5950239 bytes, checksum: a45c843d71dddc5fe0b565d5be615211 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Periodontology / Master / Master of Philosophy

This dissertation presents the results of laboratory experiments in which essential aspects of the movement of F- in saturated media have been addressed. The interactions between F-solutions and quartz, vermiculite, and kaolinite were studied through batch and column experiments. Quartz was found to react slightly with F⁻ , giving data described by a quasi-linear isotherm. Vermiculite adsorbed only minute amounts of F. A large uptake of F⁻ by kaolinite was measured. Ion exchange F⁻ by 0H⁻. may not have been the exclusive mechanism operating under the experimental conditions. The kinetics of the dissolution of fluorite (CaF₂) were investigated by means of batch and column tests. There appears to be a relationship between the dissolution rate and the mean flow velocity. Solution pHs greater than 5-6 may accelerate the dissolution process. For temperatures between 15 and 30°C, the dissolution is characterized by an activation energy of about 7 Kcal/mole, which would indicate that both surface reaction and transport are the rate-limiting step. The percolation of columns containing quartz, vermiculite, and kaolinite with multi-component solutions (including F⁻) resulted in a late breakthrough of F⁻ when compared with that of the other species. Circulation of distilled water led to an almost complete recovery of the F⁻ injected, which exited the column with relative concentrations greater than 1. When the packing included fluorite and distilled water was flushed through the column for 2 days, a concentration of F⁻ of about 1.3 pprn was rapidly reached and remained constant throughout the run. Multivariate analysis techniques (factor and correspondence analyses) were applied to data from two aquifers known to carry high F-waters. Although helpful in discriminating major and minor associations of species, none of those techniques could help unravel the behavior of F⁻ in the study aquifers. It is suggested that laboratory and field studies be continued and that, for the successful modeling of the movement and distribution of F⁻ in aquifers, non-linear source/sink terms should be included in the pertinent differential equation governing the transport of solutes.

Orientador: Juliano Pelim Pessan / Coorientador: Alberto Carlos Botazzo Delbem / Banca: Robson Frederico Cunha / Banca: Marines Nobre dos Santos Uchôa / Resumo: O dentifrício fluoretado se constitui na forma mais amplamente difundida de uso de fluoretos (F), sendo considerado sua melhor forma de utilização, uma vez que combina a remoção mecânica do biofilme com os efeitos terapêuticos do flúor. No entanto, as evidências quanto às recomendações do uso deste produto em crianças ainda são inconsistentes, considerando o balanço entre cárie e fluorose dentária. Sendo assim, o presente estudo teve o objetivo de avaliar as concentrações de flúor na saliva de crianças após escovação com dentifrícios contendo diferentes concentrações de flúor, aplicados em diferentes quantidades, bem como avaliar a ingestão de flúor a partir escovação. Para isso, crianças (n=18, 2-3 anos de idade) foram aleatoriamente distribuídas em seis grupos experimentais, de acordo com possíveis combinações de dentifrícios (0/550/1100 ppm F, como NaF) e quantidade aplicada na escova (0,04/0,16/0,32 g, correspondendo a um grão de arroz, grão de ervilha e técnica transversal, respectivamente). Os voluntários fizeram uso de um dentifrício placebo durante uma semana. No sétimo dia, amostras salivares foram coletadas antes (baseline) e 5, 15, 30 e 60 minutos após a escovação com uma das possíveis combinações de tratamentos. Todo dentifrício expectorado após a escovação foi coletado. As concentrações de flúor foram determinadas após tamponamento com TISAB III (saliva) e por microdifusão facilitada por hexametildisiloxano (conteúdo expectorado). Os dados foram submetidos a ANOV... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of fluoridated dentifrices is regarded as the best vehicle of fluoride (F) use, since it combines the mechanical removal of biofilms with the therapeutic effects of F. Nevertheless, the evidence for recommending such products to children are still inconsistent, given the balance between dental caries and fluorosis. Thus, the aim of the present study was to evaluate F concentrations in saliva of toddlers after brushing with dentifrices containing different F concentrations, applied in different quantities, as well as to estimate F intake from toothbrushing. Toddlers (n=18, 2-3 years old) were randomly assigned into six experimental groups, according to the possible combinations of dentifrices (0/550/1100 ppm F, as NaF) and amount applied on the toothbrush (0.04/0.16/0.32 g, corresponding to rice grain, pea-size and using the transverse technique, respectively). Volunteers used a placebo dentifrice during one week. On the 7th day, saliva samples were collected before (baseline), and at 5, 15, 30 and 60 minutes after toothbrushing with one of the possible treatment combinations. All toothpaste expectorated after brushing was collected. F concentrations were determined after buffering with TISAB III (saliva) and hexamethyldisiloxane-facilitated diffusion (expectorate). Data were submitted to ANOVA or Kruskal-Wallis test, followed by Fisher's LSD or Student-Newman-Keuls' tests, respectively (p<0.05). Brushing with the 550 ppm F toothpaste (pea-size or transversal technique... (Complete abstract click electronic access below) / Mestre