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Full-Text Articles in Engineering Science and Materials

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook Dec 2016

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook

Electronic Theses and Dissertations

This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared …


Direct Band Gap Gallium Antimonide Phosphide (Gasbxp1-X) For Solar Fuels., Harry Benjamin Russell May 2016

Direct Band Gap Gallium Antimonide Phosphide (Gasbxp1-X) For Solar Fuels., Harry Benjamin Russell

Electronic Theses and Dissertations

Photoelectrochemical water splitting has been identified as a promising route for achieving sustainable energy future. However, semiconductor materials with the appropriate optical, electrical and electrochemical properties have yet to be discovered. In search of an appropriate semiconductor to fill this gap, GaSbP, a semiconductor never tested for PEC performance is proposed here and investigated. Density functional theory (DFT+U) techniques were utilized to predict band gap and band edge energetics for GaSbP alloys with low amount of antimony. The overall objective of this dissertation is to understand the suitability of GaSbxP1-x alloys for photoelectrochemical water splitting application. Specifically, …


Quantification Of The Effect Of Degassing On The Microstructure, Chemistry And Estimated Strength Of Nanocrystalline Aa5083 Powder, Clara Hofmeister Jan 2016

Quantification Of The Effect Of Degassing On The Microstructure, Chemistry And Estimated Strength Of Nanocrystalline Aa5083 Powder, Clara Hofmeister

Electronic Theses and Dissertations

Degassing is a critical heat treatment process in aluminum powder metallurgy, where powders are subjected to high temperature in vacuum to remove volatile gaseous species absorbed in and adsorbed on powders. For cryomilled aluminum alloy powders with nanoscale features, degassing can cause accelerated microstructural and chemical changes including removal of volatiles, grain growth, dislocation annihilation, and formation of dispersoids. These changes can significantly alter the mechanical behavior of consolidated components based on their contributions to strength. In this study, cryomilled AA5083 (0.4 wt.% Mn; 4.5 wt.% Mg; minor Si, Fe, Cu, Cr, Zn, Ti; balance Al) powders were degassed at …


Development Of Enzyme-Free Hydrogen Peroxide Biosensor Using Cerium Oxide And Mechanistic Study Using In-Situ Spectro-Electrochemistry, Shashank Saraf Jan 2016

Development Of Enzyme-Free Hydrogen Peroxide Biosensor Using Cerium Oxide And Mechanistic Study Using In-Situ Spectro-Electrochemistry, Shashank Saraf

Electronic Theses and Dissertations

During recent development, it has been demonstrated that cerium oxide nanoparticles (CNPs) have exhibited catalytic activity which mimics naturally existing enzymes such as superoxide dismutase (SOD) and catalase. The underlying mechanism is attributed to the modulation of oxygen vacancies on CNPs lattice by dynamic switching of the oxidation states between Ce3+ and Ce4+ due to the electron transfer resulting from the redox reaction between CNPs and reactive oxygen species such as hydrogen peroxide (H2O2). Thereby the redox potential of CNPs is dependent on the surface chemistry i.e. the surface concentration of Ce3+ and Ce4+ Currently, the ratio of Ce3+/ Ce4+ …


Advanced Metrology And Diagnostic Loss Analytics For Crystalline Silicon Photovoltaics., Eric Schneller Jan 2016

Advanced Metrology And Diagnostic Loss Analytics For Crystalline Silicon Photovoltaics., Eric Schneller

Electronic Theses and Dissertations

Characterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line applications for research and development, and module/system level applications to evaluate long-term reliability. A frame work was developed to assess the cost and potential value of metrology within a manufacturing line. This framework has been published to an …


Design Of Surface Chemical Reactivity And Optical Properties In Glasses, Antoine Lepicard Jan 2016

Design Of Surface Chemical Reactivity And Optical Properties In Glasses, Antoine Lepicard

Electronic Theses and Dissertations

Thermal poling is a technique which involves the application of a strong DC electric field to a glass substrate heated below its glass transition temperature (Tg). Following the treatment, a static electric field is frozen inside the glass matrix, effectively breaking its centrosymmetry. Historically, this treatment has been used as a way to gain access to second order non-linear optical properties in glasses. However, recent efforts have shown that the treatment was responsible for structural changes as well as surface property modifications. Our study was focused on using this technique to tailor surface properties in oxide (borosilicate and niobium borophosphate) …


Improved Interpolation In Sph In Cases Of Less Smooth Flow, Oddny Brun Jan 2016

Improved Interpolation In Sph In Cases Of Less Smooth Flow, Oddny Brun

Electronic Theses and Dissertations

We introduced a method presented in Information Field Theory (IFT) [Abramovich et al., 2007] to improve interpolation in Smoothed Particle Hydrodynamics (SPH) in cases of less smooth flow. The method makes use of wavelet theory combined with B-splines for interpolation. The idea is to identify any jumps a function may have and then reconstruct the smoother segments between the jumps. The results of our work demonstrated superior capability when compared to a particular challenging SPH application, to better conserve jumps and more accurately interpolate the smoother segments of the function. The results of our work also demonstrated increased computational efficiency …


Urea Pre-Treatment Of N2-Annealed Transition Metal Oxides For Low Cost And Efficient Counter Electrodes In Dye-Sensitized Solar Cell, Hytham Elbohy Jan 2016

Urea Pre-Treatment Of N2-Annealed Transition Metal Oxides For Low Cost And Efficient Counter Electrodes In Dye-Sensitized Solar Cell, Hytham Elbohy

Electronic Theses and Dissertations

Photovoltaic cells have shown great promise as an alternative to fossil fuel-based energy sources. Dye-sensitized solar cells (DSSCs) have shown potential as low-cost replacement to silicon solar cells owing to their reduced material costs and simple fabrication techniques. Platinum (Pt) was used as a catalyst in the counter electrode for DSSCs. Metal oxides have been used as an alternative material to Pt. The introduction of oxygen vacancies inside metal oxides helps to facilitate electron transport to the electrolyte to enhance the reduction process of triiodide ions. Annealing n-type metal oxides under a reducing agent gas such as hydrogen (H2) at …