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No description available.

Primitive, mantle-derived magmas provide important clues about the formation and equilibration conditions of magmas at depth. In subduction zones, it is uncommon for primitive magmas to ascend through the shallow mantle and crust without undergoing chemical modification. Instead, magmas commonly differentiate through fractional crystallization, crustal assimilation, or magma mixing. Those rare primitive lavas that do erupt along a volcanic arc are useful for elucidating subduction-related processes within the mantle wedge (~30–80 km depth) and are the focus of this research. I used piston-cylinder apparatuses to investigate the high-pressure, high-temperature, H2O-undersaturated phase equilibria for several primitive compositions that have erupted at volcanic arcs. I aimed to reveal the permissible residual mantle mineralogy, as well as the P-T- H2O conditions over which the putative mantle melts last equilibrated before erupting. My work focuses on the Trans-Mexican Volcanic Belt (TMVB), where primitive compositions span a range of SiO2, total alkalies (K2O+Na2O), magmatic H2O, and incompatible trace element enrichments. Variations among these components are presumed to result from melting heterogeneous mantle that has been affected, to varying degrees, by a subduction component. Chapter III focuses on the phase equilibria of a Mexican basaltic andesite and an Aleutian basalt. Results show that hydrous basaltic andesite equilibrated with harzburgite in the shallow mantle, whereas the basalt equilibrated with lherzolite. The former appears more common in continental arcs and the latter in intraoceanic arcs. Chapter IV focuses on two alkaline lavas of varying K2O content from the TMVB that are transitional between potassic, hydrous minette and H2O-poor intraplate alkali basalt. Experimental phase relations and trace element modeling reveals that melting and/or mixing of peridotite and clinopyroxene-rich veins are likely involved in producing these transitional lava types. These experimental data are integrated with other petrologic and geophysical data to provide an along-arc perspective of mantle-melt equilibration in the TMVB. Primitive melts appear to commonly equilibrate with chemically heterogeneous mantle at depths above the "hot nose" of the mantle wedge. It is apparent that the shallow mantle wedge is a key component for understanding the geochemical complexities of subduction zone magmas. This dissertation includes previously published and unpublished co-authored material.

Solvent selection is an important factor in chemical process efficiency, profitability, and environmental impact. Prediction of solvent phase behavior will allow for the identification of novel solvent systems that could offer some economic or environmental advantage. A modified cohesive energy density model is used to predict the solid-liquid-equilibria for multifunctional solids in pure and mixed solvents for rapid identification of process solvents for design of crystallization processes. Some solubility data at several temperatures are also measured to further test the general applicability of the model. Gas-expanded liquids have potential environmentally advantageous applications as pressure tunable solvents for homogeneous and heterogeneous catalytic reactions and as novel solvent media for anti-solvent crystallizations. The phase behavior of some carbon dioxide/organic binary systems is measured to provide basic process design information. Solvent selection is also an important factor in the anti-solvent precipitation of solid compounds. The influence of organic solvent on the solid-liquid equilibria for two solid pharmaceutical compounds in several carbon dioxide expanded solvents is explored. A novel solvent system is also developed that allows for homogeneous catalytic reaction and subsequent catalyst sequestration by using carbon dioxide as a miscibility switch. The fundamental biphasic solution behavior of some polar organics with water and carbon dioxide are investigated.

The present dissertation investigates the relationship between the structure and thermoelectric properties of ZnO based materials, with a focus on trivalent element doping on engineering the microstructure and altering the electrical and thermal transport properties. Within the solubility range, the addition of trivalent elements, such as In3+, Fe3+ and Ga3+, is observed to increase the electrical conductivity of ZnO and decrease the thermal conductivity. / Engineering and Applied Sciences

Developing environmentally sustainable processes are essential to improving the quality of life for future generations. In addition to reducing our impact on the environment, we must design processes to be both economical and safe. A large component of any chemical process is the solvents used to dissolve the reactants and extract the products. The research presented here focuses on coupling efficient homogeneous reactions with simple heterogeneous separations using propane-organic-aqueous tunable solvent systems. Our tunable solvents undergo a phase separation upon application of propane pressure to a fully miscible mixture of water and an organic solvent. The propane based tunable systems detailed here eliminate carbonic acid formation and reduce productphase contamination when compared with the equivalent CO2 based solvent systems previously studied. Additionally, we eliminate the need to use buffers and thus solids handling equipment is not needed.

This thesis is concerned with aspects of the surface and colloid chemistry of various microemulsion systems stabilised by pure nonionic surfactants and alcohol as well as mixtures of nonionic and anionic surfactants. Phase equilibria and interfacial characteristics of the systems are studied with a view to their potential usefulness for enhanced oil recovery, in which salinity and temperature are important parameters. The equilibrium microemulsion phases are scanned at different temperatures and salinities and thus interfacial boundaries can be determined and optimum salinity scans can be performed accurately using a modified spectrophotometer. Several analytical techniques (e.g., high performance liquid chromatography, gas chromatography, ion-exchange chromatography, mass spectrometry, viscometry, electrical conductivity, photon correlation spectroscopy, UV-spectrophotometry, thermogravimetric analysis, transmission electron microscopy, surface and interfacial tension techniques) have been used to characterise and understand the microchemistry of the microemulsion systems. Ultra-low interfacial tensions (>0.1 µN/m) can be achieved in the microemulsion systems. Surfactant transfer between phases, and phase inversion of micro emulsions are shown to occur around the condition which produces minimum interfacial tension. Adsorption of the surfactants from aqueous and nonaqueous solutions has been investigated and the results show that the extent of adsorption can be reduced significantly in the presence of alcohols (co-solvent). The extent of adsorption increases with increasing temperature and salinity; however, it decreases with an increase in the hydrophilic head group of the surfactant. Adsorption of nonionic surfactants on quartz from the nonaqueous solution (decane) is much greater than from aqueous solution. In microemulsion applications, droplet combustion of w/o microemulsions is also studied for different surfaces (i.e. silica, oxidised Fecralloy and catalyst coated Fecralloy) in the temperature range of 313-573K. Formaldehyde and acetaldehyde are formed as intermediate combustion products. Thus the microemulsion combustion can lead to new oxygenate products. The w/o microemulsion route is used to synthesize colloidal silica of controlled particle size and morphology. The particle size can be varied by changing the molar ratio of water to TEOS using a water pH of 10.5.