This thesis describes a novel microfluidic platform to control the macromolecular concentrations and their applications in constructing the phase diagram of polymer aqueous solutions and in the high-throughput screening of protein crystallization conditions at the nanoliter scale. The microfluidic platform was fabricated using the soft-lithography method and based on poly(dimethylsiloxane) (PDMS) material, which is widely used in microfluidic device. PDMS is gas and water permeable elastomer. By exploiting the permeability of the gas and water in PDMS, we developed the degassed-PDMS nanoliter liquid dispensing system, the controlled microevaporation method in constructing the phase diagram of polymer aqueous solution, and the screening platform of protein crystallization conditions. / This thesis describes two types of degassed-PDMS nanoliter liquid dispensing system. One is dispensing without the microvalve, in which various liquids are dispensed through the degassed PDMS microchannel. It involves two steps: in the first step, the PDMS microchannel patch (or the entire microchip) is placed in a vacuum chamber for a certain time; in the second step, the target liquid is deposited at the inlet of the PDMS channel and dispensed into the PDMS microchamber. The other method is dispensing with the aid of PDMS microvalve. This method combines the valve control and degassed PDMS pumping source, which provides more control over on the liquid dispensing, such as isolating, mixing, etc. / Zhou, Xuechang. / Adviser: Bo Zheng. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 53-56). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

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. / Investigations of the binary systems LiF-BiF3 and NaF-BiF3 were performed with the objective of clarifying the thermal behavior and phase equilibria of these systems and their intermediary phases, an important requisite for high-quality crystal growth. Several samples in the entire range of compositions (0 to 100 mol% BiF3) of both systems were subjected to experiments of differential thermal analysis (DTA) and thermogravimetry (TG), and also of differential scanning calorimetry (DSC). A few specific compositions were selected for X-ray diffraction to supplement the experimental data. Due to the high vulnerability of BiF3 to oxygen contamination, its volatility and propensity to destroy metal parts upon heating, it was necessary to determine the optimal conditions for thermal analysis before investigating the systems themselves. Phase relations in the system LiF-BiF3 were completely clarified and a phase diagram was calculated and evaluated via the commercial software Factsage. The diagram itself consists in a simple peritectic system in which the only intermediary compound, LiBiF4, decomposes into LiF and a liquid phase. The NaF-BiF3 system could not be completely elucidated and the phase relations in the NaF poor side (> 50% BiF3) are still unknown. In the NaF rich side, however, the possible peritectoid decomposition of the compound NaBiF4 was identified. In both systems X-ray diffraction yielded crystal structures discrepant with the literature for the intermediary phases, LiBiF4, NaBiF4 and a solid solution of NaF and BiF3 called I. The observed structures remain unknown and explanations for the discrepancies were proposed.

Due to the aluminum industry demands, a large effort has recently been devoted to the development of special alloys to be used as inert anodes for a newly designed aluminum reduction cell. The implementation of this new technology aims at the replacement of the graphite anodes that have been used for over 100 years in aluminum smelting, which would reduce fossil carbon consumption, and eliminate the emission of carbon dioxide and of perfluorocarbons. Ternary alloys containing copper, nickel, and iron have been the subject of the research activities. The present research focused on the stability of the Cu-Ni-Fe alloys at high temperatures in oxidizing and fluoridating environments. The experimental methods included thermodynamic calculations of the phase diagram ('Thermocalc'), optical microscopy and microprobe microstructural and chemical investigations (EMIPA-WDS), small-angle neutron scattering (SANS), differential thermal analysis (DTA), and air-oxidation studies. The results have led to the optimization of the Cu-Ni-Fe ternary phase diagram and to an extensive study of the thermodynamics and kinetics of the spinodal decomposition and discontinuous reactions occurring during ageing as a function of alloy composition. The oxidizing reactions occurring in air at high temperatures at the surface of the alloys have been also discussed in terms of thermodynamic and kinetic laws. The phase formation in a fluorine containing environment as encountered in an aluminum electrolytic cell is predicted using principles of physical chemistry. / Graduation date: 2004 / Best scan available. Figures in original document are very dark and have a moray pattern.

Graduation date: 1997

In the present study, dilute alloys in the Mg-rich corner of the Mg-Ce-In ternary system in the composition range 0 to 3% In and 0 to 1.5% Ce were synthesized. Cooling curve analysis was used to determine the liquidus points in order to construct the liquidus surface of the ternary phase diagram in the Mg corner. Energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), and x-ray diffraction (XRD) techniques were used to examine phases present at the compositions studied. A thermal arrest presumed to represent a eutectic transformation was discovered at 580°C. Two new intermetallic compounds, designated tau and theta, were found. Trace silicon present in the alloys was found to concentrate in one of the intermetallic compounds. / To further investigate these compounds, an induction furnace was used to synthesize alloys containing the concentrations of Ce and In seen in electron probe micro-analysis (EPMA) examinations of these compounds. The alloys were examined using the cooling curve technique and XRD, and proved to contain the compounds already observed with some variation in dissolved indium content. In addition, differential scanning calorimetry (DSC) was used to confirm the liquidus and solidus values determined using cooling curve analysis. / A diffusion couple with terminal compositions of pure Ce and a Mg-In alloy was prepared in order to determine the equilibrium phases present in the system between these two compositions at 390°C. EPMA was used to identify the zones obtained, and confirmed the presence of several Mg-Ce compounds with 1 at% dissolved indium, as well as a ternary compound corresponding to the theta compound found in the dilute alloys. / Finally, literature values and experimental data were used to calculate a preliminary ternary phase diagram using FACTSage, in collaboration with the CTRC at Ecole Polytechnique, in order to affirm the validity of the experimentally determined values as well as to project the diagram beyond the studied composition range.

By extending the diagrams of materials science, the field is broadened in a natural way. For example, binary phase diagrams are like black boxes, used in the design and simulation of microstructures. They explore a balance of two chemical species, but real alloys have several chemical species, and merit a higher dimensional space. The n-dimensional extension is simplified by dividing the problem into discrete and continuous components. / "Discrete" is the identification of behavioural regimes, and their interactions, in a network graph. "Continuous" includes the curvature of boundaries, and the motion through the space. In thermochemical phase spaces, a homogenous alloy is mapped to a particle, whose motion represents the evolution of the alloy. Likewise, non-homogeneous alloys evolve as multidimensional continua. / The classical diagrams may also be hybridized. For example, TTT-curves may be treated as extra dimensions of a thermochemical phase space; the resulting hybrid synthesizes microstructural thermodynamics and kinetics.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 65-70).

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