Engineering Commons^™

Zirconium Diboride, Hexagonal Boron Nitride, And Amorphous Alumina Thin Films For High Temperature Applications, David Murdock Stewart

Electronic Theses and Dissertations

The use of microelectronic sensors and actuators in harsh, high temperature environments, such as power plants, turbine engines, and industrial manufacturing, could greatly improve the safety, reliability, and energy efficiency of these processes. The primary challenge in implementing this technology is the breakdown and degradation of thin films used in fabricating these devices when exposed to high temperatures >800 °C and oxidizing atmospheres. Zirconium diboride, hexagonal boron nitride, and amorphous alumina are candidate materials for use as thin film sensor components due to their high melting temperatures and stable phases. Zirconium diboride thin films have metallic-like electrical conductivity and remain …

Scatterometry Of 50 Nm Half Pitch Features, Ruichao Zhu

Optical Science and Engineering ETDs

Metrology technologies are an essential adjunct to Integrated Circuit (I.C.) Semiconductor manufacturing. Scatterometry, an optical metrology, was chosen to measure 50 nm half pitch feature structures. A bread-board scatterometry system has been assembled to provide a non-contact, non-destructive, accurate and flexible measurement. A real-time, on-line scatterometry system has also been demonstrated and proven to provide a high throughput measurement.

Three different types of samples have been measured using the scatterometry setup. The wire-grid polarizer (WGP) sample has been made by Jet and Flash Nanoimprint Lithography with ~100 nm pitch and ~50 nm wide ~200 nm tall Al gratings on fused …

Beta-Delayed Neutron Data And Models For Scale, Kemper Dyar Talley

Doctoral Dissertations

Recent advancements in experimental and theoretical nuclear physics have yielded new data and models that more accurately describe the decay of fission products compared to historical data currently used for many applications. This work examines the effect of the adopting the Effective Density Model theory for beta-delayed neutron emission probability on calculations of delayed-neutron production and fission product nuclide concentrations after fission bursts as well as the total delayed neutron fraction in comparison with the Keepin 6-group model. We use ORIGEN within the SCALE code package for these calculations. We show quantitative changes to the isotopic concentrations for fallout nuclides …

Large Scale Brownian Dynamics Simulation Of Dilute And Semidilute Polymeric Solutions, Amir Saadat

Doctoral Dissertations

Excluded Volume (EV) and Hydrodynamic Interactions (HI) play a central role in static and dynamic properties of macromolecules in solution under equilibrium and nonequilibrium settings. The computational cost of incorporating HI in mesoscale Brownian dynamics (BD) simulations, particularly in the semidilute regime has motivated significant research aimed at development of high-fidelity and efficient techniques.

In this study, I have developed several algorithms for the mesoscale bead-spring representation of a macromolecular solution in dilute and semidilute regimes. The Krylov subspace method enables fast calculation of single chain dynamics with simulation time scaling of O(N_b²) [order N …

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 …

Gravity-Assist Trajectories To Venus, Mars, And The Ice Giants: Mission Design With Human And Robotic Applications, Kyle M. Hughes

Open Access Dissertations

Gravity-assist trajectories to Uranus and Neptune are found (with the allowance of impulsive maneuvers using chemical propulsion) for launch dates ranging from 2024 to 2038 for Uranus and 2020 to 2070 for Neptune. Solutions are found using a patched conic model with analytical ephemeris via the Satellite Tour Design Program (STOUR), originally developed at the Jet Propulsion Laboratory (JPL). Delivered payload mass is computed for all solutions for select launch vehicles, and attractive solutions are identified as those that deliver a specified amount of payload mass into orbit at the target body in minimum time. The best cases for each …

Plasmonic Devices Based On Transparent Conducting Oxides For Near Infrared Applications, Kim Jongbum

Open Access Dissertations

In the past decade, there have been many breakthroughs in the field of plasmonics and nanophotonics that have enabled optical devices with unprecedented functionalities. Even though remarkable demonstration of at photonic devices has been reported, constituent materials are limited to the noble metals such as gold (Au) and silver (Ag) due to their abundance of free electrons which enable the support of plasmon resonances in the visible range. With the strong demand for extension of the optical range of plasmonic applications, it is now a necessity to explore and develop alternative materials which can overcome intrinsic issues of noble metals …

Dynamic Holography In Semiconductors And Biomedical Optics, Hao Sun

Open Access Dissertations

Three-dimensional scanning and display are rapidly-advancing new technologies with important commercial drivers such as 3D printing and remote imaging for big data applications. Holography is a natural approach to recording and displaying three-dimensional information because it uses phase-sensitive interferometry to record interference patterns when a reference beam encounters coherent light arriving from an object. The 3D information is contained in the values of wave optics. Holography is a broad field that goes beyond recording and displaying. For instance, holographic optical elements, which take advantage of holographic imaging principles, perform the functions of lenses, gratings or mirrors. Holographic interferometry is also …

Wave Propagation And Imaging In Structured Optical Media, Zun Huang

Open Access Dissertations

Structured optical media, usually characterized by periodic patterns of inhomogeneities in bulk materials, provide a new approach to ultimate control of wave propagation with possible practical applications: from distributed feedback lasers by diffraction gratings, to highly nonlinear performance for super-continuum generation, to fiber-optic telecommunications by microstructured photonic crystal fibers, to invisibility cloaking, to super-resolution imaging with metamaterials etc.

In particular, structured optical media allow to manipulate the wave propagation and dispersion. In this thesis, we focus on engineering the propagation phase dispersion by modulating the compositions and dimensions of the periodic elements. By tailoring the dispersion in momentum space, we …

Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal

Graduate Theses and Dissertations

The nonlinear studies of two-dimensional (2D) nanomaterials, specifically graphene, are very significant since graphene is finding its usefulness in handling the enormous heat in nanoscale high-density power electronics. Graphene has emerged to be a promising nanomaterial as an excellent heat spreader due to its high thermal conductivity. However, the experimental nonlinear study of graphene materials and their application in developing future optoelectronic devices demands for more developed research.

The research objective is first to build a precise, and sensitive technique to investigate and understand the thermal nonlinear properties, including nonlinear refractive index (n2), nonlinear absorption coefficient (β), and thermo-optic coefficient …

Synthesis, Characterization, And Fabrication Of All Inorganic Quantum Dot Leds, Haider Baqer Salman

Graduate Theses and Dissertations

Quantum Dot LEDs with all inorganic materials are investigated in this thesis. The research was motivated by the potential disruptive technology of core shell quantum dots in lighting and display applications. These devices consisted of three main layers: hole transport layer (HTL), electron transport layer (ETL), and emissive layer where the emission of photons occurs. The latter part was formed of CdSe / ZnS core-shell quantum dots, which were synthesized following hot injection method. The ETL and the HTL were formed of zinc oxide nanocrystals and nickel oxide, respectively. Motivated by the low cost synthesis and deposition, NiO and ZnO …

Fabrication Of Infrared Photodetectors Utilizing Lead Selenide Nanocrystals, Justin Anthony Hill

Graduate Theses and Dissertations

Colloidal lead selenide and lead selenide / lead sulfide core/shell nanocrystals were grown using a wet chemical synthesis procedure. Absorbance and photoluminescence measurements were made to verify the quality of the produced nanocrystals. Absorbance spectra were measured at room temperature, while photoluminescence spectra were measured at 77 K. Organic ligands were exchanged for shorter ligands in order to increase the conductivity of the nanocrystals. Absorption and PL spectra for both core and core/shell nanocrystals were compared. Interdigital photodetector devices with varying channel widths were fabricated by depositing gold onto a glass substrate. Lead selenide nanocrystals were deposited onto these metallic …

Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix

Graduate Theses and Dissertations

As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …

Development, Analysis, And Optimization Of A Swirl-Promoting Mean Flow Solution For Solid Rocket Motors, Andrew Steven Fist

Masters Theses

This work demonstrates and analyses a new flow candidate for describing the internal gaseous motion in simulated rocket motors. The fundamental features of this solution include the conservation of key system properties also incorporated in the classic Taylor-Culick (TC) system (i.e. inviscid, axisymmetric, steady and rotational properties), while allowing for the development of a swirling velocity component. The work compares the new solution to the development and formulation of the classic TC system, ultimately identifying that both the new and classic solutions are special cases of the Bragg-Hawthorne equation. Following this development, the text then explores the development of energy-optimized …

Quantitative Optical Studies Of Oxidative Stress In Rodent Models Of Eye And Lung Injuries, Zahra Ghanian

Theses and Dissertations

Optical imaging techniques have emerged as essential tools for reliable assessment of organ structure, biochemistry, and metabolic function. The recognition of metabolic markers for disease diagnosis has rekindled significant interest in the development of optical methods to measure the metabolism of the organ.

The objective of my research was to employ optical imaging tools and to implement signal and image processing techniques capable of quantifying cellular metabolism for the diagnosis of diseases in human organs such as eyes and lungs. To accomplish this goal, three different tools, cryoimager, fluorescent microscope, and optical coherence tomography system were utilized to study the …

Experimental Methods In Cryogenic Spectroscopy: Stark Effect Measurements In Substituted Myoglobin, Bradley Michael Moran

Theses and Dissertations

Dawning from well-defined tertiary structure, the active regions of enzymatic proteins exist as specifically tailored electrostatic microenvironments capable of facilitating chemical interaction. The specific influence these charge distributions have on ligand binding dynamics, and their impact on specificity, reactivity, and biological functionality, have yet to be fully understood. A quantitative determination of these intrinsic fields would offer insight towards the mechanistic aspects of protein functionality. This work seeks to investigate the internal molecular electric fields that are present at the oxygen binding site of myoglobin.

Experiments are performed at 1 K on samples located within a glassy matrix, using the …

Reduced Dimensionality Effects In Gd-Based Magnetocaloric Materials, Hillary Faith Belliveau

USF Tampa Graduate Theses and Dissertations

Magnetic refrigeration based on the magnetocaloric effect (MCE) is a promising alternative to conventional gas compression based cooling techniques. Understanding impacts of reduced dimensionality on the magnetocaloric response of a material such as Gadolinium (Gd) or its alloys is essential in optimizing the performance of cooling devices, which is also the overall goal of this thesis. We have determined, in the first part of the thesis, that laminate structures of pure Gd produced by magnetron sputtering have several disadvantages. The target material (pure Gd), ultra-high vacuum components, and the electrical energy it takes to run the manufacturing process are all …

Confinement Effects And Magnetic Interactions In Magnetic Nanostructures, Kristen Lee Stojak Repa

USF Tampa Graduate Theses and Dissertations

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers.

Magnetite (Fe₃O₄) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of …

Novel Magnetic Nanostructures For Enhanced Magnetic Hyperthermia Cancer Therapy, Zohreh Nemati Porshokouh

USF Tampa Graduate Theses and Dissertations

In this dissertation, I present the results of a systematic study on novel multifunctional nanostructure systems for magnetic hyperthermia applications. All the samples have been synthesized, structurally/magnetically characterized, and tested for magnetic hyperthermia treatment at the Functional Materials Laboratory of the University South Florida. This work includes studies on four different systems: (i) Core/shell Fe/γ-Fe₂O₃ nanoparticles; (ii) Spherical and cubic exchange coupled FeO/Fe₃O₄ nanoparticles; (iii) Fe₃O₄ nano-octopods with different sizes; (iv) High aspect ratio FeCo nanowires and Fe₃O₄ nanorods.

In particular, we demonstrated the enhancement of the heating …

Experimental Investigation Of Plasma Dynamics In Jets And Bubbles Using A Compact Coaxial Plasma Gun In A Background Magnetized Plasma, Yue Zhang

Electrical and Computer Engineering ETDs

Numerous solar and astrophysical observations of jet- and bubble-like plasma structures exhibit morphological similarities, suggesting that there may be common plasma physics at work in the formation and evolution processes of these structures at different system scales. The ideal magnetohydrodynamics (MHD) provide the necessary theoretical basis for employing laboratory experiments to investigate key physical processes in nonlinear astrophysical and solar systems, especially when magnetic fields are present.

A coaxial magnetized plasma gun has been designed, installed, and operated in the HelCat linear device at the University of New Mexico. In Region I, a current-driven plasma jet is formed. The plasma …

Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang

Doctoral Dissertations

Polymer-based semiconducting materials are promising candidates for large-scale, low-cost photovoltaic devices. To date, the efficiency of these devices has been low in part because of the challenge of optimizing molecular packing while also obtaining a bicontinuous structure with a characteristic length comparable to the exciton diffusion length of 10 to 20 nm. In this dissertation we developed an innovative evaporation-induced nanoparticle self-assembly technique, which could be an effective approach to fabricate uniform, densely packed, smooth thin films with cm-scale area from home-made P3HT nanoparticles. Unlike the previous reports of nanoparticle-based film formation, we use a mixture of two solvents so …

Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar

Doctoral Dissertations

The idea of sequencing a DNA based on single-file translocation of the DNA through nanopores under the action of an electric field has received much attention over the past two decades due to the societal need for low cost and high-throughput sequencing. However, due to the high speed of translocation, interrogating individual bases with an acceptable signal to noise ratio as they traverse the pore has been a major problem. Experimental facts on this phenomenon are rich and the associated phenomenology is yet to be fully understood. This thesis focuses on understanding the underlying principles of polymer translocation, with an …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Effect Of Void Fraction On Transverse Shear Modulus Of Advanced Unidirectional Composites, Jui-He Tai

USF Tampa Graduate Theses and Dissertations

In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.

Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, …

Development Of Ultrasonic Techniques For Characterization Of Liquid Mixtures, William A. Cooke

Electronic Thesis and Dissertation Repository

To evaluate the suitability of ultrasonic techniques for on-line process monitoring applications, an ultrasonic probe was used to measure acoustic velocity, acoustic impedance, and isentropic compressibility of hydrocarbons (including n-, iso-, and cycloalkanes, toluene, mineral oil, and crude oil) and polar liquids (alcohols, water, salt water) over a temperature range of 25-60°C. Temperature, carbon chain length, molecular shape, and intermolecular forces had significant effects on ultrasonic parameters. Relationships between media characteristics and observed ultrasonic parameters were modeled using empirical-least squares equations. The same parameters were measured in binary mixtures of hydrocarbons in heptane, as well as polar liquids in ethanol. …

Parametric Design, Modeling, And Optical Evaluation Of Retroreflective Prismatic Structures, Sama Hussein

Electronic Thesis and Dissertation Repository

Retroreflectors (RR) are defined as passive optical structures that redirect incident light to its originating source. Specific types of retroreflectors called inverted cubes (ICs) function through total internal reflection (TIR) and are used in various applications such as measurement tools, traffic signs and automotive rear and side lighting. This thesis aims to model, analyze, fabricate and study a novel type of IC retroreflectors called right triangular prism (RTP). A parametric approach is used to model existing IC geometries from a generic unit cube and is then implemented to model the novel RTP geometry. Those elements are then tested by optical …

A Generalized Method For Fissile Material Characterization Using Short-Lived Fission Product Gamma Spectroscopy, Justin Richard Knowles

Doctoral Dissertations

Characterizing the fissile content of nuclear materials is of particular interest to the safeguards and nuclear forensics communities. Short-lived fission product gamma spectroscopy offers a significant reduction in analysis time and detection limits when compared to traditional non-destructive assay measurements. Through this work, a fully generalizable method that can be applied to variations in fissile compositions and neutron spectra was developed for the modeling and measurement of short-lived fission product gamma-rays. This method uses a 238-group neutron flux that was characterized for two pneumatic tube positions in the High Flux Isotope Reactor using flux monitor irradiations. This flux spectrum was …

Characterizing Local Order And Physical Properties Of Rare Earth Complex Oxides, Thomas Jacob Shamblin

Doctoral Dissertations

With more than 500 compositions, materials possessing the pyrochlore structure have a myriad of technological applications and physical phenomena. Three of the most noteworthy properties are the structure’s ability to resist amorphization making it a possible host matrix for spent nuclear fuel, its exotic magnetic properties arising from geometric frustration, and fast ionic conductivity for solid-oxide fuel cell applications. This work focuses on these three aspects of the pyrochlore’s many potential uses. Structural characterization revealed that pyrochlore-type oxides have a tendency to disorder from a high symmetry cubic structure to a lower symmetry orthorhombic arrangement in response to a variety …

Actinium-225 Production Via Proton Irradiation Of Thorium-232, Justin Reed Griswold

Doctoral Dissertations

High energy proton spallation reactions on natural thorium metal targets have been utilized to produce multi mCi [milliCurie] quantities of Actinium-225. Theoretical cross sections for actinium and thorium isotopes as well as for a select number of the fission products produced in these reactions were generated by the Monte Carlo radiation transport code PHITS to simulate the experimental data obtained from sixteen irradiations of thorium metal targets with 25-210 µA [microampere] proton beams ranging in energies from 77 to 192 MeV. Irradiations were conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing …

Forcing Cesium Into Higher Oxidation States Via Useful Hard X-Ray Induced Chemistry At Extreme Conditions, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recent theoretical work published in Nature Chemistry postulates the existence of cesium in high oxidation states when bonding with fluorine. It is thus predicted to behave as a p-block element (such as xenon) at pressures above 5 GPa. At these pressures, fluorine atoms may bond with the inner p-shell electrons forming CsFn, where n may vary from 2 up to 6; thus the oxidation state of Cs may change up to 6+. My research focused on physically synthesizing these compounds and to verify that, given the right conditions, bonding doesn't only occur with valence electrons, but with the inner p-shell …