Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 10 of 10
Full-Text Articles in Entire DC Network
Synthesis And Characterization Of Stable And Metastable Phases In Ni- And Fe-Based Alloy Systems By Mechanical Alloying, Ahmed Al-Joubori
Synthesis And Characterization Of Stable And Metastable Phases In Ni- And Fe-Based Alloy Systems By Mechanical Alloying, Ahmed Al-Joubori
Electronic Theses and Dissertations
Mechanical Alloying (MA) is a process that involves repeated cold welding, fracturing and rewelding of powder particles in a high-energy ball mill and has been used extensively to synthesize both stable (equilibrium) and metastable phases in a number of alloy systems. This is due to its ability to achieve many effects simultaneously, viz., reduction in grain size, introduction of a variety of crystal defects, disordering of the lattice, and modifying the crystal structures of materials; all these allowing alloying and phase transformations to occur in powders. In this Dissertation, we have synthesized a number of different alloy phases in Ni- …
Phase Transformation And Growth Kinetics In Reaction Zone Between Uranium Alloy And Zirconium Diffusion Barrier, Young Joo Park
Phase Transformation And Growth Kinetics In Reaction Zone Between Uranium Alloy And Zirconium Diffusion Barrier, Young Joo Park
Electronic Theses and Dissertations
U-10wt.%Mo (U10Mo) alloy as a part of monolithic fuel system is being developed under Material Management and Minimization Reactor Conversion (MMMRC) program, tasked with replacing high-enriched uranium (HEU) fuel with low-enriched uranium (LEU) fuel in civilian research and test reactors. Use of U10Mo fuel alloy entails a Zr diffusion barrier to avoid the undesirable interdiffusion and reactions between the U10Mo and Al-alloy cladding. To better understand the interaction between these fuel system constituents, microstructural development and diffusion kinetics in U-Mo-Zr, U-Zr and fuel plate assembly processed by co-rolling and hot isostatic pressing (HIP) were investigated using a variety of analytical …
A Study Of Crystallization Behavior In Phase Separated Chalcogenide Glasses, Andrew Buff
A Study Of Crystallization Behavior In Phase Separated Chalcogenide Glasses, Andrew Buff
Electronic Theses and Dissertations
Chalcogenide glasses (ChG) are known for their wide transmission ranges in the infrared and for their high refractive indices. However, applications for ChG are often limited by their poor thermal/mechanical properties. Precipitating a secondary crystalline phase in the glass matrix can improve these properties, but too much crystallization and/or large or multiple phase crystallites can lead to a loss in infrared (IR) transmission. Controlled crystallization can be used to tune the properties of these glasses. This work examines the crystallization behavior in phase separated chalcogenide glasses in the GeSe2-As2Se3-PbSe glass system. Specifically, the research presented in this thesis work has …
Fabrication And Investigation Of An Enzyme-Free, Nanoparticle-Based Biosensor For Hydrogen Peroxide Determination, Craig Neal
Electronic Theses and Dissertations
Electrochemical biosensors often employ enzymes as detection elements. These sensors are highly selective towards target analytes, however the scope of their application is limited by the poor stability of the enzyme. In this study, multi-valent inorganic cerium oxide nanoparticles were used as detection elements for the analysis of hydrogen peroxide. The electrochemical response of the cerium oxide towards hydrogen peroxide analyte is defined through cyclic voltammetry and chronoamperometry. This response was found to be dependent on nanoparticle Ce3+:Ce4+ redox state ratio and this property is exploited to fabricate a biosensor. As produced, the biosensor demonstrated sensitivity at picomolar analyte concentrations. …
Stress-Induced Phase Change Sintering: A Novel Approach To The Fabrication Of Barium Chloride Transparent Ceramic Scintillators, William Shoulders
Stress-Induced Phase Change Sintering: A Novel Approach To The Fabrication Of Barium Chloride Transparent Ceramic Scintillators, William Shoulders
Electronic Theses and Dissertations
For the precise in-field identification of dangerous radioisotopes, the desire for higher resolution, cheaper, and more rugged gamma-ray scintillator detectors has pushed the materials science community to investigate new compounds and processing techniques. One particular solution is Eu:BaCl2 transparent ceramics processed by the novel phase-change sintering technique. Typically, optical transparency in BaCl2 would be limited by birefringence scattering at grain boundaries due to mismatch in refractive index. Traditional ceramic processing routes would also predispose this volatile and hygroscopic material to the formation of defects, which interrupt the energy transfer in the scintillation process. Literature shows that these challenges have prevented …
Nanoengineered Energy Harvesting And Storage Devices, Chao Li
Nanoengineered Energy Harvesting And Storage Devices, Chao Li
Electronic Theses and Dissertations
Organic and perovskite solar cells have recently attracted significant attention due to its flexibility, ease of fabrication and excellent performance. In order to realize even better performance for organic and perovskite solar cells, rejuvenated effort towards developing nanostructured electrodes and high quality active layer is necessary. In this dissertation, several strategic directions of enhancing the performance of organic and perovskite solar cells are investigated. An introduction and background of organic and perovskite solar cells, which includes motivation, classification and working principles, nanostructured electrode materials and solvent effect on active materials, and devices fabrication, are presented. A facile method, called Spin-on …
Interdiffusion, Crystallography And Mechanical Properties Of Nickel Manganese Gallium Alloys, Le Zhou
Interdiffusion, Crystallography And Mechanical Properties Of Nickel Manganese Gallium Alloys, Le Zhou
Electronic Theses and Dissertations
NiMnGa Heusler alloys, functioning as either ferromagnetic shape memory alloys or mangetocaloric materials, have both practical applications and fundamental research value. The functional properties of NiMnGa alloys are closely related to the martensitic transformation from high temperature austenitic phase to low temperature martensitic phase. Alloys can be used for room temperature or high temperature applications, depending on the martensitic transformation temperature, which is compositional sensitive. The microstructure and crystallography of the martensites can be very complex but are crucial to the optimization of the material performance. In this study, for the first time, a combinatorial study by combining solid-to-solid diffusion …
Electrical Properties Of Polymer-Derived Silicoaluminum Carboxide Ceramics (Sialco) And Their Applications In Micro-Sensors, Yejie Cao
Electronic Theses and Dissertations
Polymer-derived ceramic (PDC) is a new kind of material which is directly synthesized by the thermal decomposition of polymer precursors. Due to their unique structure, which consists of the amorphous matrix phase and free-carbon phase, PDCs exhibit many distinguished properties even at high-temperature environment such as oxidation and creep resistance, amorphous semiconducting behavior as well as piezoresistive behavior. These outstanding properties make PDCs become promising candidates for various applications especially for high-temperature microsensors. However, most common used PDCs in the market now are SiC, SiCN and Si(M)CN ceramics, the high price and toxicity of their raw materials as well as …
Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov
Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov
Honors Undergraduate Theses
Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of …
A Parametric Study Of Meso-Scale Patterns For Auxetic Mechanical Behavior Optimization, Matthew C. Schuler
A Parametric Study Of Meso-Scale Patterns For Auxetic Mechanical Behavior Optimization, Matthew C. Schuler
Honors Undergraduate Theses
This thesis focuses on the development, parameterization and optimization of a novel meso-scale pattern used to induce auxetic behavior, i.e., negative Poisson's ratio, at the bulk scale. Currently, the majority of auxetic structures are too porous to be utilized in conventional load-bearing applications. For others, manufacturing methods have yet to realize the meso-scale pattern. Consequently, new auxetic structures must be developed in order to confer superior thermo-mechanical responses to structures at high temperature. Additionally, patterns that take into account manufacturing limitations, while maintaining the properties characteristically attached to negative Poisson's Ratio materials, are ideal in order to utilize the potential …