Master of Science
J. Clara Wren
This thesis presents work on the effects of ionizing radiation on phosphonium-based ionic liquids (ILs). Ionic liquids are known for their tunable properties which make them attractive options for applications for the separation and sequestration of metal ions from spent nuclear fuels, and candidate lubricants for systems under severe conditions. The high radiation environment found in spent fuel processing may decompose the solvents (ILs) used in the process and affect their separation efficiency. The radiolytic decomposition products can also alter the physical and chemical properties of an IL in ways which can affect the potential corrosion of metal alloys in contact with the IL.
This thesis focusses on the study of phosphonium-based ILs, a class of ILs which has not been extensively investigated, but which holds promise for future applications. The first part of the thesis contains a quantum chemical calculation of the molecular properties of several phosphonium-based ILs using density functional theory. Correlations between the molecular properties (e.g., dipole moment) and physical properties (e.g., viscosity) are explored. The second part of the thesis presents work on the irradiation of these ILs alone or in contact with carbon steel. Pure IL samples were exposed to gamma radiation for up to 192 h and the liquid and gas phases were analyzed using spectroscopic, electrochemical and chromatographic techniques. The results show that the ILs are relatively resistant of radiolytic degradation, but there are measurable quantities of small organic species created from fragmentation of the alkyl ligands of the IL cation. Corrosion of carbon steel in the IL [P14666] [Br] was studied with the IL in contact with an inert (Ar) or oxidizing (air) cover gas in the presence and absence of gamma radiation. Significant corrosion was observed and the extent of the corrosion appeared greater for the tests performed in the absence of gamma radiation. The corrosion is attributed to the presence of impurity H2O and O2 dissolved in the IL, and a corrosion mechanism is presented to explain the results.
Morco, Ryan P., "Effect of Gamma Radiation on the Interfacial Reactions and Transfer Processes of Phosphonium-based Ionic Liquids with Carbon Steel" (2014). Electronic Thesis and Dissertation Repository. 2442.