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High burnup nuclear fuels have the potential to improve the economics of nuclear power, increase proliferation resistance and reduce waste generation. One technical challenge of increasing burnup is understanding the impact of the pellet-clad bond layer (PCBL) on heat transfer through the fuel. This thesis combines molecular dynamics simulations with experiments to investigate the thermal expansion, heat capacity and thermal conductivity of the PCBL. The PCBL was simulated as a (U,Zr)O2 solid solution. (U,Zr)O2 samples were synthesised using external gelation. It was found the using external gelation did not increase the solubility of ZrO2 relative to powder mixing methods and that to produce high density pellets (> 90 % theoretical density) of (U,Zr)O2 required hyperstoichiometry, with an O:M ratio > 2.10, and sintering temperatures exceeding 1500 C. Molecular dynamics (MD) simulations were performed on (U,Zr)O2 between 300 - 3000 K. The thermal expansion and heat capacity of all tested compositions was very similar up to 1400 K and consistent with the experimentally derived thermal expansion. Thermal conductivity was decreased for compositions containing ZrO2 at temperatures between 300--500~K, greater temperatures showed no discernible difference. The coefficient of thermal expansion, \(\alpha\), was measured experimentally for (U,Z)O2, with y = 0, 0.13 and 0.18, using in-situ XRD and was found to be 11-12 x10^-6 K^-1, for all three samples, at temperatures 300-600 K. No statistically significant difference in thermal expansion of the three samples was found, which matched results from the MD simulations. Phonon density of states (PDOS) measured using inelastic neutron scattering revealed that addition of ZrO2 caused a softening of phonons at 20~meV and a new phonon peak to appear at 23 meV. Additional simulations were performed on (U,Pu,Zr)O2. The addition of PuO2 causes a reduction in lattice parameter, albeit not as significant as with ZrO2 addition. PuO2 addition has little effect on the thermal expansion and heat capacity. PuO2 content caused an increase in thermal conductivity, although not enough to negate the impact of ZrO2. Further simulations on (U,Ce,Zr)O2 shows CeO2 to be a good surrogate for PuO2 with similar lattice parameter, heat capacity, thermal expansion and thermal conductivity.

Abstract: To enable scalable MOSFET technology in III-V semiconductor platforms, high quality semiconductor-oxide interfaces are essential. In this work, the role of surface reactions in the oxide deposition process is examined, with the objective of optimizing the thermodynamics of the semiconductor-oxide interface. A novel low-temperature plasma-enhanced atomic layer deposition (PEALD) technique was applied to deposit nanoscale high-k dielectrics on several III-V substrates, including InP, GaAs, InAs, and GaN. Approximately 7 nm of ZrO2 was grown and patterned to form MOSCAP structures, which were subsequently analyzed through electrical characterization to evaluate dielectric and interface quality. The oxide films fabricated were found to have interface trap densities ranging from 1010-1013 eV-1cm-2, and showed high capacitance densities (~2.5 μF/cm2). GaN and InP MOSCAPs with ZrO2 dielectric layers were found to have gate currents in line with direct tunneling phenomena and MOS mobilities approaching that of doped bulk semiconductors. Scaled InP MOSFET devices using these experimental oxide results were also simulated using improved device structures, with the aim of demonstrating optimal parameters for effective reduction of short-channel effects. These devices demonstrated high performance for various scaled gate lengths, with FinFET structures showing excellent frequency response at the 7 nm process node.

Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures, they would be excellent solid lubricants for a wide range of conditions. Atomic layer deposition (ALD) is a growth technique capable of depositing highly uniform and conformal films in challenging applications that have buried surfaces and high-aspect-ratio features such as microelectromechanical (MEMS) devices where the need for robust solid lubricants is sometimes necessary. This dissertation investigates the surface and subsurface characteristics of ALD-grown ZnO/Al2O3 nanolaminates and ZrO2 monofilms before and after sliding at room temperature. Significant enhancement in friction and wear performance was observed for some films. HRSEM/FIB, HRTEM and ancillary techniques (i.e. SAED, EELS) were used to determine the mechanisms responsible for this enhancement. Contributory characteristics and energy dissipation modes were identified that promote low-temperature lubricity in both material systems.

The environmental applications of oxidation catalysis were examined as part of a two-stage strategy for the reduction of nitrogen oxides (NOx) and also for the removal of carbon monoxide from hydrogen streams. Cobalt-based catalysts were examined. Reduction of NOx, Co/TiO2 and Co/ZrO2 were studied for the oxidation of NO to NO2 in excess oxygen. NO oxidation was studied as the first step in a two-step catalytic scheme where NO is oxidized to NO2 and, in turn, NO2 is reduced with CH4 to N2 under lean conditions. Catalysts were prepared by sol-gel and incipient-wetness impregnation techniques. It was found that increasing the calcination temperature had an adverse effect on the activity of the IWI catalysts. Catalyst characterization showed higher activity for NO oxidation on Co/ZrO2 than on Co/TiO2 which was observed to correlate with the formation of the Co3O4 phase. For the preferential oxidation of CO, cobalt on several metal oxide supports were investigated and showed the highest activity on Co/ZrO2. A variety of reaction experiments were performed to examine the effects of reactant concentrations, residence time, and temperature on the CO conversion and O2 selectivity to CO2.