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Full-Text Articles in Engineering
Interdiffusion And Impurity Diffusion In Magnesium Solid Solutions, Catherine Kammerer
Interdiffusion And Impurity Diffusion In Magnesium Solid Solutions, Catherine Kammerer
Electronic Theses and Dissertations
Magnesium, being lightweight, offers potential to be developed into extensive structural applications. The transportation segment has particular interest in Mg and Mg alloy for applications where reduced vehicle weight is proportional to increased fuel efficiency. Aluminum and zinc are two of the most common alloying elements in commercial Mg alloys. They improve the physical properties of Mg through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of and microstructural development during solidification and heat treatment. However, there is limited diffusion data available for Mg and Mg alloys. In particular, because Al is monoisotopic, tracer …
Interdiffusion Reaction Between Uranium-Zirconium And Iron, Young Joo Park
Interdiffusion Reaction Between Uranium-Zirconium And Iron, Young Joo Park
Electronic Theses and Dissertations
U-Zr metallic fuels cladded in Fe-alloys are being considered for application in an advanced Sodium-Cooled Fast Reactor (SFR) that can recycle the U-Zr fuels and minimize the long-lived actinide waste. To understand the complex fuel-cladding chemical interaction of the U-Zr metallic fuel with Fe-alloys, a systematic multicomponent diffusion study was carried out using solid-to-solid diffusion couples. The U-10 wt.% Zr vs. pure Fe diffusion couples were assembled and annealed at temperatures, 630, 650 and 680°C for 96 hours. Development of microstructure, phase constituents, and compositions developed during the thermal anneals were examined by scanning electron microscopy, transmission electron microscopy and …
Design And Characterization Of High Temperature Packaging For Wide-Bandgap Semiconductor Devices, Brian Grummel
Design And Characterization Of High Temperature Packaging For Wide-Bandgap Semiconductor Devices, Brian Grummel
Electronic Theses and Dissertations
Advances in wide-bandgap semiconductor devices have increased the allowable operating temperature of power electronic systems. High-temperature devices can benefit applications such as renewable energy, electric vehicles, and space-based power electronics that currently require bulky cooling systems for silicon power devices. Cooling systems can typically be reduced in size or removed by adopting wide-bandgap semiconductor devices, such as silicon carbide. However, to do this, semiconductor device packaging with high reliability at high temperatures is necessary. Transient liquid phase (TLP) die-attach has shown in literature to be a promising bonding technique for this packaging need. In this work TLP has been comprehensively …
Characterization, Morphology, Oxidation, And Recession Of Silicon Nanowires Grown By Electroless Process, Robert G. Mertens
Characterization, Morphology, Oxidation, And Recession Of Silicon Nanowires Grown By Electroless Process, Robert G. Mertens
Electronic Theses and Dissertations
This dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping. In here is presented work derived from a long-term study of SiNWs. Several important aspects of SiNWs were investigated and the results published in journals and conference papers. The recession of SiNWs was heretofore unreported by other research groups. In our investigations, …
Diffusion And Reaction In Selected Uranium Alloy System, Ke Huang
Diffusion And Reaction In Selected Uranium Alloy System, Ke Huang
Electronic Theses and Dissertations
U-Mo metallic fuels with Al alloys as the matrix/cladding are being developed as low enriched uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) program. Significant interactions have been observed to occur between the U-Mo fuel and the Al alloy during fuel processing and irradiation. U-Zr metallic fuels with stainless steel claddings have been developed for the generation IV sodium fast reactor (SFR). The fuel cladding chemical interaction (FCCI) induced by the interdiffusion of components was also observed. These interactions induce deleterious effects on the fuel system, such as thinning of the cladding layer, formation of phases …
Impurity And Interdiffusion In The Magnesium-Aluminum System, Sarah Tiffany Brennan
Impurity And Interdiffusion In The Magnesium-Aluminum System, Sarah Tiffany Brennan
Electronic Theses and Dissertations
Magnesium alloys offer a base of lightweight engineering materials for electronic, military and transportation applications where weight reduction is crucial for higher efficiency. Understanding fundamental diffusion behavior in Mg alloys elicits better materials properties through the optimization of processing techniques and heat treatments, whose material responses are affected by diffusion. The main objective of this study is to provide a clear, comprehensive description of the diffusion behavior in the technically important magnesium-aluminum binary metallic system. In this study, diffusion in the Mg-Al system was observed through solid diffusion couples and thin film specimens in the temperature range of 673-523K. The …
Interdiffusion Behavior Of U-Mo Alloys In Contact With Al And Al-Si Alloys, Emmanuel Perez
Interdiffusion Behavior Of U-Mo Alloys In Contact With Al And Al-Si Alloys, Emmanuel Perez
Electronic Theses and Dissertations
http://purl.fcla.edu/fcla/etd/CFE0003747
On The Nature Of The Flow In A Separated Annular Diffuser, Jason Dunn
On The Nature Of The Flow In A Separated Annular Diffuser, Jason Dunn
Electronic Theses and Dissertations
The combustor-diffuser system remains one of the most studied sections of the turbomachine. Most of these investigations are due to the fact that quite a bit of flow diffusion is required in this section as the high speed flow exits the compressor and must be slowed down to enter the combustor. Like any diffusion process there is the chance for the development of an unfavorable adverse pressure gradient that can lead to flow separation; a cause of drastic losses within a turbine. There are two diffusion processes in the combustor-diffuser system: The flow first exits the compressor into a pre-diffuser, …
Laser Enhanced Doping For Silicon Carbide White Light Emitting Diodes, Sachin Bet
Laser Enhanced Doping For Silicon Carbide White Light Emitting Diodes, Sachin Bet
Electronic Theses and Dissertations
This work establishes a solid foundation for the use of indirect band gap semiconductors for light emitting application and presents the work on development of white light emitting diodes (LEDs) in silicon carbide (SiC). Novel laser doping has been utilized to fabricate white light emitting diodes in 6H-SiC (n-type N) and 4H-SiC (p-type Al) wafers. The emission of different colors to ultimately generate white light is tailored on the basis of donor acceptor pair (DAP) recombination mechanism for luminescence. A Q-switched Nd:YAG pulse laser (1064 nm wavelength) was used to carry out the doping experiments. The p and n regions …
On The Use Of Variable Coherence In Inverse Scattering Problems, Erwan Baleine
On The Use Of Variable Coherence In Inverse Scattering Problems, Erwan Baleine
Electronic Theses and Dissertations
Even though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only by bulky short pulse measurements. The spatial counterpart of temporal coherence, however, has barely been exploited in sensing applications. This dissertation examines, in different scattering regimes, a variety …
Probing Random Media With Singular Waves, Chaim Schwartz
Probing Random Media With Singular Waves, Chaim Schwartz
Electronic Theses and Dissertations
In recent years a resurgence of interest in wave singularities (of which optical vortices are a prominent example), light angular momentum and the relations between them has occurred. Many applications in various areas of linear and non-linear optics have been based on studying effects related to angular momentum and optical vortices. This dissertation examines the use of such wave singularities for studying the light propagation in highly inhomogeneous media and the relationship to angular momentum transfer. Angular momentum carried by light can be, in many cases, divided in two terms. The first one relates to the polarization of light and …
Study Of Discharge Coefficient And Trends In Film Cooling Effectiveness Of Conical Holes With Increasing Diffusion Angles, Humberto Zuniga,
Study Of Discharge Coefficient And Trends In Film Cooling Effectiveness Of Conical Holes With Increasing Diffusion Angles, Humberto Zuniga,
Electronic Theses and Dissertations
Previous studies indicate that increasing the diffusion angle in conical film-cooling holes leads to an improvement in their film cooling effectiveness. Discharge coefficient and film cooling effectiveness measurements are conducted to characterize this behavior. Part of the focus of this investigation is to find out how this trend develops and attempt to ascertain the optimum cone angle, if possible. Six test plates, each with one row of eight conical-shaped cooling holes of equal diffusion angles of 0, 1, 2, 3, 6, or 8 [degrees], with respect to the hole axis are used in this study. The ratios of the hole …
Interdiffusion Analysis For Nicocraly And Nial Vs. Various Superalloys, Emmanuel Perez
Interdiffusion Analysis For Nicocraly And Nial Vs. Various Superalloys, Emmanuel Perez
Electronic Theses and Dissertations
Hot section components in gas turbines can be NiCoCrAlY-coated to provide the component with an Al reservoir that maintains a protective oxide layer on its surface. Over the service life of the component, the coatings degrade by composition and phase changes due to oxidation/hot-corrosion, and multicomponent interdiffusion from and into the superalloy substrate. In this study, the rate of Al interdiffusion into selected Ni-base superalloys using various diffusion couples of two-phase NiCoCrAlY (beta + gamma) and single beta-phase NiAl with the selected alloys is measured. The diffusion couples were examined with an emphasis on the composition-dependence of Al interdiffusion. Microstructural …
Phenomenology And Experimental Observations In High Temperature Ternary Interdiffusion, Abby Lee Elliott
Phenomenology And Experimental Observations In High Temperature Ternary Interdiffusion, Abby Lee Elliott
Electronic Theses and Dissertations
A new method to extract composition dependent ternary interdiffusion coefficients from a single diffusion couple experiment is presented. The calculations involve direct determination of interdiffusion fluxes from experimental concentration profiles and local integration and differentiation of Onsager's formalism. This new technique was applied to concentration profiles obtained from selected semi-infinite, single-phase diffusion couple experiments in the Cu-Ni-Zn, Fe-Ni-Al, and Ni-Cr-Al systems. These couples exhibit features such as uphill diffusion and zero flux planes. The interdiffusion coefficients from the new technique along with coefficients reported from other methods are graphed as functions of composition. The coefficients calculated from the new technique …