Made available in DSpace on 2014-10-09T12:26:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:00Z (GMT). No. of bitstreams: 0 / Relatório realizado pela CETESB em 2006 mostrou que 80% dos 645 municípios são total ou parcialmente abastecidos por água subterrânea e que em 13 bacias hidrográficas do Estado de São Paulo a água subterrânea é a fonte prioritária de abastecimento. O uso da água subterrânea em diversos setores reforça a sua importância e gera preocupações quanto a sua proteção e qualidade. A região noroeste do Estado de São Paulo, abastecida principalmente por captação de água subterrânea do aqüífero Guarani por meio de poços tubulares, apresenta ocorrência de Selênio. Assim, no presente trabalho procurou-se avaliar a contribuição de selênio em águas subterrâneas. Foram coletadas amostras de água subterrânea de quatro poços tubulares profundos captadas do aqüífero Guarani na região noroeste do Estado de São Paulo e foram realizadas medidas do elemento selênio, utilizando a espectrometria de absorção atômica com atomização eletrotérmica (GFAAS) e geração de hidretos (HGAAS). Além do selênio também foram analisados outros metais (B, Al, V, Cr, Mn, Ni, Cu, Zn, Mo, Sn, Li, Be, Mg, P, Ca, Fe, Ba, Co, Na, Si, K, Ag, Cd, Pb, Sb, Hg e As) por ICP OES em todas as amostras. A caracterização do selênio foi realizada com uma periodicidade de amostragem trimestral, no período de Março de 2006 a Março de 2007, totalizando cinco campanhas. O metal analisado neste estudo foi selecionado atendendo-se as exigências da legislação que avalia a qualidade da água para abastecimento publico, estabelecendo limites máximos permissíveis para concentração de metais: Portaria 518/2004 MS (VPM para Se: 0,010 mg/L), referente à potabilidade. As análises realizadas mostraram que as concentrações de Se estão acima do limite máximo permissível e que as técnicas atomização eletrotérmica (GFAAS) e geração de hidretos (HGAAS) demonstraram equivalência nos resultados. As análises demonstraram que a presença de Se parece estar associada a fatores mineralógicos (formação geológica da região) e as metodologias apresentaram-se eficientes com respostas similares diferenciando-se em fatores operacionais e de custo. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Hydrogen can be an unlimited source of clean energy for future because of its very high energy density compared to the conventional fuels like gasoline. An efficient and safer way of storing hydrogen is in metals and alloys as hydrides. Light metal hydrides, alanates and borohydrides have very good hydrogen storage capacity, but high operation temperatures hinder their application. Improvement of thermodynamic properties of these hydrides is important for their commercial use as a source of energy. Application of pressure on materials can have influence on their properties favoring hydrogen storage. Hydrogen desorption in many complex hydrides occurs above the transition temperature. Therefore, it is important to study the physical properties of the hydride compounds at ambient and high pressure and/or high temperature conditions, which can assist in the design of suitable storage materials with desired thermodynamic properties. The high pressure-temperature phase diagram, thermal expansion and compressibility have only been evaluated for a limited number of hydrides so far. This situation serves as a main motivation for studying such properties of a number of technologically important hydrides. Focus of this dissertation was on X-ray diffraction and Raman spectroscopy studies of Mg2FeH6, Ca(BH4)2, Mg(BH4)2, NaBH4, NaAlH4, LiAlH4, LiNH2BH3 and mixture of MgH2 with AlH3 or Si, at different conditions of pressure and temperature, to obtain their bulk modulus and thermal expansion coefficient. These data are potential source of information regarding inter-atomic forces and also serve as a basis for developing theoretical models. Some high pressure phases were identified for the complex hydrides in this study which may have better hydrogen storage properties than the ambient phase. The results showed that the highly compressible B-H or Al-H bonds and the associated bond disordering under pressure is responsible for phase transitions observed in brorohydrides or alanates. Complex hydrides exhibited very high compressibility suggesting possibility to destabilize them with pressure. With high capacity and favorable thermodynamics, complex hydrides are suitable for reversible storage. Further studies are required to overcome the kinetic barriers in complex hydrides by catalytic addition. A comparative study of the hydride properties with that of the constituting metal, and their inter relationships were carried out with many interesting features.

The thesis first introduces the topic of nuclear energy and provides a brief section on plant familiarisation, after which zirconium nuclear fuel cladding is explained, and an in-depth literature review is presented on the in-service degradation of this component from hydriding. The concept of synchrotron X-ray diffraction is elucidated, and examples of its use are given, relevant to the topic of this work. The experimental section discusses an initial quantification of the Zircaloy-4 material used throughout the present work, and documents in minutia the process of collecting and analysing in-situ synchrotron X-ray diffraction data. The experimental campaign discussed within involved a series of consecutive thermal cycles designed to investigate the redistribution of hydrogen as a function of thermal and concentration gradients; the kinetics of precipitation during isothermal dwells at reactor relevant temperatures; and the evolution of strain in the matrix and hydride during these dwells. As an alternative style thesis, these three topics are separated into three independent proposed manuscripts, produced in a format ready for publication. The diffusion and redistribution paper observes localised enrichment and depletion that occurs as a function of time and temperature, investigating the flux of hydrogen that results from concentration and thermal gradients, and introduces the concept of hydrogen trapping. The second manuscript documents evidence of the rate limiting kinetics for hydride precipitation seen at elevated temperatures, and describes a model for nucleation, developed to support the experimentally produced results. The final manuscript investigates the nature of the strains that evolve in the matrix and hydride phases during precipitation and growth, highlighting slow-strain rate relaxation in both phases and examining the constraining effect that the matrix has on the hydride precipitates. Lastly, the themes from each of the three manuscripts are drawn together in a final conclusion, after which further experimental analysis that is to be performed as part of this experimental campaign is outlined.

The advent of laser cooling and optical manipulation for atomic samples revolutionized atomic physics in 1990’s, allowing the creation of new phases of matter, more accurate atomic clocks, and enabling leading candidates for the first functional quantum computer. This could not have been predicted at the time, and is a testament to the value of fundamental research for its own sake. These same laser cooling techniques are now being applied to simple molecular systems with the same revolutionary potential. In this thesis, I will present a range of experiments exploring these schemes in a new class of molecules, the diatomic alkaline earth hydrides. We present the creation and characterization of a bright beam of cold barium hydride molecules, high precision spectroscopy of these samples, as well as optical deflection and transverse cooling. This represents the first laser cooling of a Hydride molecule. This is a crucial step towards the creation of new cold molecular samples for a variety of scientific applications. In the final chapter, I will change gears, and introduce new ideas for the detection of scalar field dark matter. While this variety of dark matter is typically searched for using atomic clocks, I will show that the same coupling also leads to anomalous acceleration of test masses. This acceleration would be detectable using both a network of precision acceleration sensors known as the IGETS network, and by the LIGO observatory. This new technique will compliment existing search strategies, and has higher sensitivity for a wide region of parameter space.

Hydrogenation products of the Zintl phases AeTt (Ae = alkaline earth; Tt = tetrel) exhibit hydride anions on interstitial sites as well as hydrogen covalently bound to Tt which leads to a reversible hydrogenation at mild conditions. In situ thermal analysis, synchrotron and neutron powder diffraction under hydrogen (deuterium for neutrons) pressure was applied to BaTt (Tt=Ge, Sn). BaTtHy (1<y<1.67, γ-phases) were formed at 5 MPa hydrogen pressure and elevated temperatures (400–450 K). Further heating (500–550 K) leads to a hydrogen release forming the new phases β-BaGeH0.5 (Pnma, a=1319.5(2) pm, b=421.46(2) pm, c=991.54(7) pm) and α-BaSnH0.19 (Cmcm, a=522.72(6) pm, b=1293.6(2) pm, c=463.97(6) pm). Upon cooling the hydrogen rich phases are reformed. Thermal decomposition of γ-BaGeHy under vacuum leads to β-BaGeH0.5 and α-BaGeH0.13 [Cmcm, a=503.09(3) pm, b=1221.5(2) pm, c=427.38(4) pm]. At 500 K the reversible reaction α-BaGeH0.23 (vacuum)⇄β-BaGeH0.5 (0.2 MPa deuterium pressure) is fast and was observed with 10 s time resolution by in situ neutron diffraction. The phases α-BaTtHy show a pronounced phase width (at least 0.09<y<0.36). β-BaGeH0.5 and the γ-phases appear to be line phases. The hydrogen poor (α- and β-) phases show a partial occupation of Ba4 tetrahedra by hydride anions leading to a partial oxidation of polyanions and shortening of Tt–Tt bonds.

Polyhedral Oligomeric Silsesquioxane (POSS) cages are investigated in terms of their potential to enclose small metal hydrides, with the objective of defining conditions that maximize the number of encapsulated hydrogen atoms. Systems of the form MH2n@Tm, where n = 1-3, m = 8, 10, and M comprises metal atom species of the groups IV, VI, VIII, X, and XII, are studied by methods of ab initio and density functional theory (DFT). The resulting composites are categorized with respect to their structural and energetic features. For MH2@T8, it is found in all cases considered that including MH2 into the POSS cage is an endothermic process. For MH2@T10 and M = Ti, Ru, Os, Pt, inclusion of the MH2 guest into the cage turns out to be exothermic, and also leaves the cage intact. For MH4@Tm, this behavior is only observed for one system, OsH4@T10.

Polyhedral Oligomeric Silsesquioxane (POSS) cages are investigated in terms of their potential to enclose small metal hydrides, with the objective of defining conditions that maximize the number of encapsulated hydrogen atoms. Systems of the form MH2n@Tm, where n = 1-3, m = 8, 10, and M comprises metal atom species of the groups IV, VI, VIII, X, and XII, are studied by methods of ab initio and density functional theory (DFT). The resulting composites are categorized with respect to their structural and energetic features. For MH2@T8, it is found in all cases considered that including MH2 into the POSS cage is an endothermic process. For MH2@T10 and M = Ti, Ru, Os, Pt, inclusion of the MH2 guest into the cage turns out to be exothermic, and also leaves the cage intact. For MH4@Tm, this behavior is only observed for one system, OsH4@T10.

The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, that metal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differing reactivities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungstenhydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydrides on KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.

Récemment, sous des pressions de plusieurs gigapascals, de nouveaux hydrures ont été synthétisés avec des propriétés étonnantes potentiellement porteuses de ruptures technologiques pour le stockage de l’hydrogène ou la supraconductivité. Plusieurs superhydrures sont étudiés expérimentalement et simulés par DFT dans cette thèse. Les diagrammes de phases en pression de LiBH4 et NaBH4, deux composés d’intérêt pour le stockage de l’hydrogène, sont explorés par diffraction de rayons X, spectroscopie Raman et infrarouge jusqu’à des pressions de 300 GPa sans observer de décomposition. L’insertion d’hydrogène dans NaBH4 donne le super-hydrure NaBH4(H2)0.5. Pour éclaircir l’interprétation de la supraconductivité record à 200 K trouvée dans H2S sous pression, le super-hydrure H3S a été synthétisé à partir des éléments S et H. Les résultats de diffraction semblent en désaccord avec l’interprétation communément admise qu’H3S en phase Im-3m est responsable de cette supraconductivité et laisse la porte ouverte à d’autres interprétations. Enfin, les super-hydrures CrHx avec x=1, 1.5 et 2 ont également été synthétisés à partir des éléments et caractérisés par diffraction de rayons X. Si ces hydrures correspondent bien àceux qui avaient été prédits numériquement, l’absence des stoechiométries plus élevées est discutée. Pour mesurer les températures de supraconductivité calculées dans les superhydrures MHx, une cellule à enclumes de diamant miniature permettant une détection de l’effet Meissner a été développée. / Recently, under pressures of several gigapascals, new hydrides have been synthesised with striking properties that may herald technological breakthroughs for hydrogen storage and superconductivity. In this PhD thesis, several superhydrides have been studied experimentally and simulated by DFT. The pressure phase diagrams of LiBH4 and NaBH4, two compounds of interest for hydrogen storage, have been explored thanks to X-ray diffraction and Raman and infrared spectroscopy up to pressures of 300 GPa without observing any decomposition. The insertion of hydrogen inside NaBH4 generates the superhydride NaBH4(H2)0.5. To refine the interpretation of the record superconductivity found in H2S under pressure at 200 K, the superhydride H3S has been synthesised from S and H elements. The results of the diffraction study seem to be at odds with the commonly accepted interpretation that Im-3m H3S is responsible for the superconductivity observed and leaves the door open to other interpretations. Finally, CrHx hydrides with x = 1, 1.5 and 2 have also been synthesised from the elements and characterised by X-ray diffraction. Although these hydrides do correspond to the ones that had been numerically predicted, the absence of the expected higher stoichiometries is discussed. To measure the superconductivity temperatures calculated for MHx hydrides, a miniature diamond anvil cell which allows the detection of a Meissner effect has been developed.

The oxidative addition of both monosubstituted and disubstituted a.-amino acids to [Ir(COD)(PMe3)3]Cl (COD = cyclooctadiene) was studied and the reactivity of the resulting complexes was examined. The reaction of [Ir(COD)(PMe3)3]CI with the disubstituted amino acids, diphenylglycine and methyl phenyl alanine, led to an almost exclusive facial product. Monosubstituted amino acid complexes were observed to be mixtures of the meridional and facial isomers with the meridional isomer largely predominating. The meridional isomer was found to convert to the facial isomer when heated for several days at 100°C. In fact, a predominantly meridional mixture was found to convert to a predominantly facial mixture upon heating. The facial isomer was therefore shown to be the thermodynamic product from the mixture. Small amounts of other isomers were observed in the hydride region of the proton NMR spectrum. One resonance at -23.75 ppm disappeared upon heating t-butyl acetylene with the amino acid complex. The disappearance of this hydride resonance may indicate the insertion of the unsaturate into the Ir-H bond, or alternatively, the conversion of this isomer to a more thermodynamically stable isomer. Reactions of these complexes with methylpropiolate and acrylamide were attempted but evidence of an insertion product was not found. / Master of Science