Graduate Theses & Dissertations

Supercritical Water Chemistry
Supercritical water (SCW) exhibits unique properties that differentiates it from its low temperature behaviour. Hydrogen bonding is dramatically reduced, there is no phase boundary between liquid and gaseous states, heat capacity increases, and there is a drastic reduction of the dielectric constant. Efforts are underway for researchers to harness these properties in the applications of power generation and hazardous waste destruction. However, the extreme environment created by the high temperatures, pressures and oxidizing capabilities pose unique challenges in terms of corrosion not present in subcritical water systems. Molecular Dynamics (MD) simulations have been used to obtain mass transport, hydration numbers and the influence on water structure of molecular oxygen, chloride, ammonia and iron (II) cations in corrosion crevices in an iron (II) hydroxide passivation layer. Solvation regimes marking the transitions of solvation based versus charge meditated processes were explored by locating the percolation thresholds of both physically and hydrogen bonded water clusters. A SCW flow through reactor was used to study hydrogen evolution rates over metal oxide surfaces, metal release rates and the kinetics for the oxidation of hydrogen gas by oxygen in SCW. Insights into corrosion phenomena are provided from the MD results as well as the experimental determination of flow reactor water and hydrogen chemistry. Author Keywords: Flow Studies, Molecular Dynamics, Supercritical Water
Novel Aliphatic Lipid-Based Diesters for use in Lubricant Formulations
Structure-property relationships are increasingly valued for the identification of specifically engineered materials with properties optimized for targeted application(s). In this work, linear and branched diesters for use in lubricant formulations are prepared from lipid-based oleochemicals and their structure-property relationships reported. It is shown that the branched diesters possess exceptional physical property profiles, including suppression of crystallization, and are superior alternatives for use in lubricant formulations. For the linear aliphatic diesters, both high and low temperature properties were predictable functions of total chain length, and both were differently influenced by the fatty acid versus diol chain length. Symmetry did not influence either, although thermal stability decreased and thermal transition temperatures increased with increasing saturation. All of the linear diesters demonstrated Newtonian flow behaviour. Viscosity was also predictable as a function of total chain length; any microstructural features due to structural effects were superseded by mass effects. Author Keywords: Crystallization, Phase behaviour, Rheology, Structure-Function, Thermogravimetric analysis, Vegetable Oils

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