Physical Sciences and Mathematics Commons^™

Characterization Of The Corrosion And Oxide Film Properties Of Alloy 600 And Alloy 800, Melissa Faichuk

Electronic Thesis and Dissertation Repository

The passive film properties of Alloy 600 and Alloy 800, both of which are used as steam generator tubing in CANDU reactors, have been studied using techniques such as polarization scans, electrochemical impedance spectroscopy and X-ray photoelectron and Auger spectroscopies. The composition of the oxides formed in a 0.1 M Na₂S₂O₃ solution have been characterized over a wide range of potentials from the pre-passive, through the passive to the transpassive regions. These changes have been correlated to the electrochemical behaviour. A second set of experiments was performed to determine the effectiveness of the surface mechanical …

Investigating The Effects Of Radiation On Phosphonium-Based Ionic Liquids, Susan Howett

Electronic Thesis and Dissertation Repository

This thesis presents work on the understanding of the effects of ionizing radiation on phosphonium-based ionic liquids (ILs). The capability of ILs to dissolve a wide range of molecules, and the potential of ILs to be highly resilient in energy-intensive environments makes them particularly promising media for the separation and sequestration of metal ion contaminants from radioactive waste effluents in nuclear fuel cycles. For this application, a water/IL system will be exposed to a continuous stream of ionizing radiation. The radiation environment will strongly influence the chemical state of the water phase in the system and the chemical parameters affecting …

Optical Properties, Electronic Structures And High Pressure Study Of Nanostructured One Dimensional Titanium Dioxide By Synchrotron Radiation And Spectroscopy, Ankang Zhao

Electronic Thesis and Dissertation Repository

One dimensional (1D) titanium dioxide (TiO₂) nanomaterials have been extensively studied in recent years due to their superior electrical, optical mechanical and chemical properties compared with their bulk counterparts. Two different kinds of 1D TiO₂ nanomaterials, TiO₂ nanowires (TiO₂ NW) and TiO₂ nanotubes (TiO₂ NT), are studied in this thesis by using various techniques.

In one study, TiO₂ NW synthesized by hydrothermal method and a series of calcinated TiO₂ NW were investigated by using absorption near edge structures (XANES), X-ray diffraction (XRD) and X-ray excited optical luminescence (XEOL). It is found …

In Situ High-Pressure Studies Of Energetic Materials By Vibrational Spectroscopy And X-Ray Diffraction, Liang Zhou

Electronic Thesis and Dissertation Repository

Nitrogen-rich materials have been considered as the most promising replacement of traditional energetic materials due to the large energy gap between the different nitrogen allotropes as well as the generation of environmental friendly nitrogen gas as the end-product. As a result, methods of synthesizing the nitrogen-rich materials have received increasing attention. Apart from the traditional chemical synthesis, high-pressure technique had been proved an effective tool to create such kinds of materials. However, several issues still existed concerning the high-pressure synthesis of energetic materials. Therefore, searching for precursors is of great interest. Here we report studies of four promising precursors, 5-aminotetrazole, …

Approximation Of Exchange-Correlation Potentials For Orbital-Dependent Functionals, Alexei Kananenka

Electronic Thesis and Dissertation Repository

Density-functional theory (DFT) is the most widely used method of modern computational chemistry. All practical implementations of DFT rely on approximations to the unknown exchange-correlation functional. These approximations may be devised in terms of energy functionals or effective potentials. In this thesis, several approximations of the latter type are presented.

Given a set of canonical Kohn–Sham orbitals, orbital energies, and an external potential for a many-electron system, one can invert the Kohn–Sham equations in a single step to obtain the corresponding exchange-correlation potential, vXC(r). We show that for orbitals and orbital energies that are solutions of the Kohn–Sham equations with …

Electrochemical Evaluation Of Ionic Liquids For Biphasic Extraction Of Metal Ions Common To Spent Nuclear Fuel, Thomas J. Stockmann

Electronic Thesis and Dissertation Repository

Over the past 30 years electrochemistry at a liquid|liquid interface has been used to observe and quantify simple ion transfer (IT) as well as ligand assisted, or facilitated ion transfer (FIT) reactions. Liquid|liquid electrochemistry has developed to where valuable thermodynamic constants – for example, the metal ion to ligand stoichiometry and overall complexation constant, β, in FIT - can be evaluated using cyclic voltammetry (CV). Recently, ionic liquids (ILs) have shown greater metal ion extraction efficiencies in water-IL biphasic separations relative to conventional molecular organic solvents. In this way, they are of interest to the nuclear industry for applications …

In Situ High-Pressure Studies Of Ammonia Borane Derivatives By Vibrational Spectroscopy, Zhihao Yu

Electronic Thesis and Dissertation Repository

Hydrogen has been regarded as a promising candidate to replace the conventional fossil fuel, and thus attracted enormous research efforts. However, hydrogen storage remains to be a big challenge to its practical applications. Consequently, the investigation of suitable hydrogen storage materials has become a highly active research field. Here we reported the first high pressure studies of three promising hydrogen storage materials, N(CH₃)₃BH₃, NH(CH₃)₂BH₃ and NaNH₂BH₃ by Raman and IR spectroscopy.

First, N(CH₃)₃BH₃ was studied at room temperature and pressures up …

Carbon Nitride And Conjugated Polymer Composite Materials, Josh Byers

Electronic Thesis and Dissertation Repository

The semiconductor and photovoltaic properties of carbon nitride (CNx) thin films prepared using a reactive magnetron sputtering technique were investigated both individually and as composites with the organic conjugated polymers polybithiophene (PBT) and poly(3-hextlthiophene) (P3HT). At low nitrogen content, the film structure was dominated by graphitic sp² percolation networks, whereas at higher nitrogen contents CNx films started to demonstrate semiconductor properties, as evidenced by the occurrence of photoconductivity and the development of a space charge region. When CNx was deposited onto a PBT substrate, it was found to function as an acceptor material improving the photocurrent generation both in …

X-Ray Absorption Fine Structure And X-Ray Excited Optical Luminescence Studies Of Gallium Nitride - Zinc Oxide Solid Solution Nanostructures, Matthew J. Ward

Electronic Thesis and Dissertation Repository

Gallium nitride – zinc oxide (GaN-ZnO) solid solutions have been realized as potential photocatalysts for overall water splitting due to a narrowing of the band-gap into the visible region of the solar spectrum. Although there has been much experimental and theoretical work on this novel class of semiconductors many questions about the nature of their electronic and chemical properties remain unanswered. In particular the mechanism of band-gap reduction in these materials is not clearly understood. It is also unclear what the local chemical environment of gallium, zinc, nitrogen, and oxygen is in both the surface and bulk of these solid …

A Study Of Gamma Radiation Induced Carbon Steel Corrosion, Kevin Daub

Electronic Thesis and Dissertation Repository

This thesis presents work on the development of a mechanistic understanding of the effect of ionizing radiation on the aqueous corrosion kinetics of carbon steel. Exposed to ionizing radiation, water decomposes into a range of oxidizing (O₂, •OH, HO₂•, H₂O₂) to reducing (•e_aq^–, •O₂^–, •H) species. The production of the redox active species by radiolysis can have a significant effect on the corrosion behaviour of a metal. Of particular interest is the effect of radiolysis on corrosion when the solution environment, such as temperature, pH, and …

Theory Of Model Kohn-Sham Potentials And Its Applications, Alex P. Gaiduk

Electronic Thesis and Dissertation Repository

The purpose of Kohn-Sham density functional theory is to develop increasingly accurate approximations to the exchange-correlation functional or to the corresponding potential. When one chooses to approximate the potential, the resulting model must be integrable, that is, a functional derivative of some density functional. Non-integrable potentials produce unphysical results such as energies that are not translationally or rotationally invariant. The thesis introduces methods for constructing integrable model potentials, developing properly invariant energy functionals from model potentials, and designing model potentials that yield accurate electronic excitation energies. Integrable potentials can be constructed using powerful analytic integrability conditions derived in this work. …