Engineering Commons^™

Ion Irradiation Characterization Studies Of Max Phase Ceramics, Daniel William Clark

Masters Theses

The family of layered carbides and nitrides known as MAX phase ceramics combine many attractive properties of both ceramics and metals due to their nanolaminate crystal structure and are promising potential candidates for application in future nuclear reactors. This thesis reports on the background, design, and analysis of an experiment focused on determining the effects of energetic heavy ion irradiations on polycrystalline samples of titanium silicon carbide 312, titanium aluminum carbide 312, and titanium aluminum carbide 211. The irradiation conditions consisted of ion doses between 10 and 30 displacements per atom at temperatures of 400 and 700 degrees Celsius, conditions …

Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck

Electronic Theses and Dissertations

Little is known about the impact of additive manufacturing in the spare part supply chain. A few studies are available, but they focus on specific parts and their applications only. A general model, which can be adapted to different applications, is nonexistent. This dissertation proposes a decision making framework that enables an interested practitioner/manager to decide whether using additive manufacturing to make spare parts on demand is economical when compared to conventional warehousing strategy. The framework consists of two major components: a general discrete event simulation model and a process of designing a wide range of simulation scenarios. The goal …

Designing Optical Properties In Infrared Glass, Benn Gleason

All Dissertations

Chalcogenide glasses (ChGs) are well-known for their attractive optical properties, such as high refractive index and transparency in across infrared wavelengths. ChGs also possess the ability to compositionally tune properties such as the refractive index, the thermo-optic coefficient, and other non-optical properties. Chalcogenide glasses with compositionally tailored physical and optical properties will provide optical designers with new materials necessary to create novel infrared imaging systems requiring new or expanded functionality. This dissertation has evaluated the relationship between glass composition, the resulting atomic structure, and resulting optical and thermo-optical properties, with specific focus on the infrared refractive index and the thermo-optic …

Solution Processed Optical Coatings For Solar Cell Applications, Rajesh Tummala

Material Science and Engineering Theses

In the recent past the demand for higher energy conversion efficiency of solar cells is on the rise. Extensive research is carrying out and many new methods have been proposed by changing either fabrication process or implementation of anti-reflection coatings. In this thesis, the solution processed omni directional anti-reflection coatings have been demonstrated on commercial amorphous silicon solar cells and on fabricated organic solar cells. A simple convective coating technique is utilized to deposit spherical silica micro-particles on the commercial amorphous silicon solar cells and on fabricated organic solar cells. In order to investigate the behavior of solar cells at …

Mechanical Reliability Of Porous Low-K Dielectrics For Advanced Interconnect: Study Of The Instability Mechanisms In Porous Low-K Dielectrics And Their Mediation Through Inert Plasma Induced Re-Polymerization Of The Backbone Structure, Yoonki Sa

Material Science and Engineering Dissertations

Continuous scaling down of critical dimensions in interconnect structures requires the use of ultralow dielectric constant (k) films as interlayer dielectrics to reduce resistance-capacitance delays. Porous carbon-doped silicon oxide (p-SiCOH) dielectrics have been the leading approach to produce these ultralow-k materials. However, embedding of porosity into dielectric layer necessarily decreases the mechanical reliability and increases its susceptibility to adsorption of potentially deleterious chemical species during device fabrication process. Among those, exposure of porous-SiCOH low-k (PLK) dielectrics to oxidizing plasma environment causes the increase in dielectric constant and their vulnerability to mechanical instability of PLKs due to the loss of methyl …

Studying An All-Vanadium Photoelectrochemical Cell For Highly Efficient Solar Energy Conversion And Storage Via Photocatalytic Redox Reaction, Dong Liu

Material Science and Engineering Dissertations

This study aims at developing a promising alternative approach to utilize solar energy continuously with high efficiency by employing photocatalytic vanadium redox reactions to overcome major drawbacks associated with conventional photoelectrochemical water splitting. The preliminary study was implemented on TiO2 and WO3/TiO2 by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and zero-resistance ammetry (ZRA) in a photoelectrochemical cell (PEC). The results show much enhanced photoelectrochemical response with the assistance of vanadium(IV, VO2+) redox species. Such photoresponse improvement is attributed to the hole scavenging effect by fast vanadium redox reaction to depress charge recombination at semiconductor/liquid interface in both TiO2 and …

Magnetic-Plasmonic Multilayered Nanorods, Orathai Thumthan

Material Science and Engineering Dissertations

Multilayered nanorods which consist of alternating magnetic layers separated by Au layers combine two distinctive properties, magnetic properties and surface plasmonic resonance (SPR) properties into one nano-entity. Their magnetic properties are tunable by changing the layer thickness, varying from single domain to superparamagnetic state. Superparamagnetic is a key requirement for magnetic nanoparticles for bioapplications. Superparamagnetic nanoparticles exhibit high magnetic moments at low applied magnetic field while retain no magnetic moments when magnetic field is removed preventing them from aggregation due to magnetic attraction. Au layers in the nanorods provide anchorage sites for functional group attachment. Also, Au nanodisks exhibit SPR …

Comprehensive Study Of Composition Gradient Strontium Doped Lanthanum Manganite Thin Films Deposited By Magnetron Co-Sputtering, Yishu Wang

Material Science and Engineering Dissertations

In this body of work, the examination of three different types of Strontium doped lanthanum manganite thin films synthesized by magnetron sputtering in the Surface and Nano Engineering Laboratory (SaNEL) allowed for the development of a detailed understanding between the processing conditions, the nano-scale structure and strain relaxation of the as-deposited thin films. Pure Lanthanum manganite and strontium doped lanthanum manganite thin films which were epitaxially grown on (001) single crystalline lanthanum alumina (LAO) and magnesium oxide (MgO) were fabricated by using single target deposition. The optimum deposition conditions were explored as preparation for synthesis epitaxial composition gradient strontium doped …

Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker

Theses and Dissertations

The importance of a reliable and safe way to store energy, and allow for on-demand usage, has led to much research in the field of secondary battery development. The thesis herein explores a technology that has shown promising results when implemented in large-scale energy grid applications. Though the technology has proven viable in both load-leveling on existing grids as well as serving to legitimize renewable energy sources, the development of such advanced battery systems is not without challenge. Sodium-sulfur (NaS) secondary cells have shown promising results when implemented in the aforementioned energy storage applications. One of the main drawbacks to …

A Platform For Fast Detection Of Let-7 Micro Rna Using Polyaniline Fluorescence And Image Analysis Techniques, Partha P. Sengupta

Master's Theses

The project describes a new strategy for transducing hybridization events through modulating intrinsic properties of the electroconductive polymer polyaniline (PANI). When DNA based probes electrostatically interact with PANI, its fluorescence properties are increased, a phenomenon that can be enhanced by UV irradiation. Hybridization of target nucleic acids results in dissociation of probes causing PANI fluorescence to return to basal levels. By monitoring restoration of base PANI fluorescence as little as 10^-11 M (10 pM) of target oligonucleotides could be detected within 15 minutes of hybridization. Detection of complementary oligos was specific, with introduction of a single mismatch failing to …

Kinetic And Thermodynamic Modeling Of Long Term Phase Stability In Alloy 800h Subjected To Lwr Core Conditions, Wayne Ethan Pratt

Masters Theses

An in depth literature review of Incoloy Alloy 800H was conducted and presented to summarize the current understanding of microstructural evolution under irradiation and secondary phase precipitate stability. Due to a lack of radiation induced segregation (RIS) data for Alloy 800H, Isopleth sections varying Cr, Ni, Ti, and Si were generated from a computational thermodynamics approach using ThermoCalc and analyzed to compensate for knowledge related to radiation induced precipitates (RIP’s). These isopleths were analyzed for a composition range based off previous knowledge of RIS tendencies in austenitic stainless steels. Analysis of four major binary phase diagrams and complex phase diagrams …

In Vacuo Fabrication And Electronic Structure Characterization Of Atomic Layer Deposition Thin Films, Michael Schaefer

USF Tampa Graduate Theses and Dissertations

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements.

The work presented here encompasses the implementation of an …

Investigation Of Low Thermal Conductivity Materials With Potential For Thermoelectric Applications, Kaya Wei

USF Tampa Graduate Theses and Dissertations

Thermoelectric devices make it possible for direct energy conversion between heat and electricity. In order to achieve a high energy conversion efficiency, materials with a high thermoelectric figure of merit (ZT = S²σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity) are in great demand. The standard approach is to optimize charge carrier transport while at the same time scatter the heat transport, a task that is easier said than done. Improving the electrical properties in order to increase ZT is limited since electrons …

Near-Field Microwave Microscopy For Surface And Subsurface Characterization Of Materials, Maria Fernanda Cordoba Erazo

USF Tampa Graduate Theses and Dissertations

This dissertation presents an investigation on the capabilities of Near-Field Microwave Microscopy (NFMM) for the characterization of surface and subsurface materials. Subsurface characterization refers to the detection, differentiation and imaging of dielectric, and metallic features that are coated with an insulating layer. The design, simulation and modeling, and testing of a dielectric resonator (DR)-based NFMM and a coaxial transmission line resonator-based NFMM are discussed in detail in this work. Additionally, materials differentiation and imaging capabilities of each microscope are examined using several bulk samples, liquids, GaAs MMIC circuits, and gold/glass testing patterns.

The 5.7 GHz DR-based NFMM uses a microwave …

Synthesis, Characterization And Ferroelectric Properties Of Ln-Type Znsno3 Nanostructures, Corisa Kons

USF Tampa Graduate Theses and Dissertations

With increasing focus on the ill health and environmental effects of lead there is a greater push to develop Pb-free devices and materials. To this extent, ecofriendly and earth abundant LiNbO₃-type ZnSnO₃, a derivative of the ABO₃ perovskite structure, has a high theoretically predicted polarization making it an excellent choice as a suitable alternative to lead based material such as PZT. In this work we present a novel synthesis procedure for the growth of various ZnSnO₃ nanostructures by combined physical/chemical processes. Various ZnSnO₃ nanostructures of different dimensions were grown from a ZnO:Al template …

Evaluating Corrosion Resistance Of Reinforcing Steel In A Novel Green Concrete, Andrea Carolina Ramirez

USF Tampa Graduate Theses and Dissertations

Reinforced concrete structures are expected to have a long service life with minimal maintenance. Corrosion of reinforcing steel is a major factor in reducing concrete structure lifespan, as corrosion products occupy a larger volume than that of the consumed steel and generate tensile stresses that crack the concrete cover. Procedures to control corrosion in traditional concrete, which is made with Portland-cement (PC), have been well established. However, in recent years novel concrete materials based on alternatives to normally cured PC have been developed in response to global needs to reduce greenhouse gases emissions. In particular, a promising new cement has …

Tailoring The Pore Environment Of Metal-Organic And Molecular Materials Decorated With Inorganic Anions: Platforms For Highly Selective Carbon Capture, Patrick Stephen Nugent

USF Tampa Graduate Theses and Dissertations

Due to their high surface areas and structural tunability, porous metal-organic materials, MOMs, have attracted wide research interest in areas such as carbon capture, as the judicious choice of molecular building block (MBB) and linker facilitates the design of MOMs with myriad topologies and allows for a systematic variation of the pore environment. Families of MOMs with modular components, i.e. MOM platforms, are eminently suitable for targeting the selective adsorption of guest molecules such as CO₂ because their pore size and pore functionality can each be tailored independently. MOMs with saturated metal centers (SMCs) that promote strong yet reversible …

Measuring Polydimethylsiloxane (Pdms) Mechanical Properties Using Flat Punch Nanoindentation Focusing On Obtaining Full Contact, Federico De Paoli

USF Tampa Graduate Theses and Dissertations

In this research, the materials used were the Polydimethylsiloxane (PDMS) polymers. PDMS mechanicals properties were measured using a customized version of the nanoindentation test using a flat punch tip. The method is proposed in Chapter 3 and it is used to calculate the elastic modulus of different PDMS samples. The samples tested were both produced specifically for this research and available in the laboratory’s storage. They all present different levels of cross-linking degree.

It is quite common to not have full contact between the cylindrical flat punch and the sample because of the unavoidable tilt. The new method guarantees establishing …

Inkjet Printed Thin Film Electrodes For Lithium-Ion Batteries, Stephen D. Lawes

Electronic Thesis and Dissertation Repository

With the miniaturization of wireless electronics, the demand for ever-smaller energy storage devices has increased. Thin film batteries can meet this need by providing higher energy densities at smaller scales than conventional lithium-ion batteries. However, the fabrication of thin films batteries by vapor deposition methods typically involves expensive equipment and high temperatures, which limits their commercial application. This thesis reports the development of an inexpensive inkjet printing method of fabricating thin film electrodes for thin film lithium-ion batteries. Inks containing various electrode materials were first developed and optimized in terms of physical properties to ensure ideal jetting conditions. Then, thin …

Dynamic Triaxial Compression Experiments On Borosilicate And Soda-Lime Glass, John T. Chojnacki

Open Access Theses

A series of compression experiments were performed on borosilicate and soda-lime glass using a triaxial compression Kolsky bar. The triaxial compression Kolsky bar differs from a traditional Kolsky bar by having two pressure chambers, one enclosing the specimen and the other enclosing the end of the transmission bar, so that a specimen may be pre-stressed axially and radially before a dynamic axial load is applied. The result is a modified Kolsky bar capable of measuring axial deformation and axial stresses of a specimen at various strain rates under a range of confinement pressures. Borosilicate glass was subjected to triaxial confinement …

Improving Response Characteristics Of Split Ring Resonators Using Experimental Designs, Omer Faruk Keskin

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this thesis is to investigate the application of design of experiments approaches in the analysis of split ring resonators, and to compare two different approaches. The design parameters of the meta-material device are examined to study all the main effects, the two factor interactions, and the curvature effects. A full factorial design and a central composite design is utilized for the study. The results in improving split ring resonator design are discussed.

This study shows that the design of experiments approaches can effectively be utilized to examine the effects on the response values of a specific type …

Application Of 3d Printing Technology In Porous Anode Fabrication For Enhanced Power Output Of Microbial Fuel Cells, Bin Bian

Electronic Thesis and Dissertation Repository

Microbial fuel cells (MFCs) are widely researched for application in wastewater treatment. However, the current anodes used in MFCs often suffer from high fabrication cost and uncontrollable pore sizes. In this thesis, three-dimensional printing technique was utilized to fabricate anodes with different micro pore sizes for MFCs. Copper coating and carbonization were applied to the printed polymer anodes to increase the conductivity and specific surface area. Voltages of MFCs with various anodes were measured as well as other electrochemical tests such as linear sweep voltammetry and electrochemical impedance spectroscopy. 3D copper porous anode produced higher maximum voltages and power densities …

Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak

Theses and Dissertations

More than twenty-five years of continuous operation in the dusty environments of Southwest Asia have shown that degradation of gas turbine engine components due to particle ingestion is a serious threat to operations. In particular, the continued push for higher engine operating temperatures has brought a new emphasis to the damage mechanisms (for example CMAS glass formation and hot corrosion) caused by ingested particles forming molten deposits on engine components. Despite decades of research little progress has been made to mitigate the effects of CMAS and hot corrosion degradation to engine components. This research focused on hot corrosion specifically. A …

Characterization Of Point Defects In Lithium Aluminate (Lialo2) Single Crystals, Maurio S. Holston

Theses and Dissertations

Lithium aluminate (LiAlO₂) is an insulating wide-band gap material currently under development for tritium breeding and radiation detection and dosimetry applications. Point defects are imperfections in a crystal lattice localized over a few atomic lengths that can alter the electrical, mechanical, or optical properties of materials. An understanding of point defect behavior is a necessary precursor for optimizing lithium aluminate for nuclear applications. This dissertation has identified and characterized the major point defects created and induced through x-ray and neutron radiation using electron paramagnetic resonance and fluorescence spectroscopy, thermoluminescence, and optical absorption. This dissertation explains for the first …

Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center And Reaction Center Plus Light Harvesting Complexes, Houman Yaghoubi

USF Tampa Graduate Theses and Dissertations

Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic …

Ductility And Use Of Titanium Alloy And Stainless Steel Aerospace Fasteners, Jarrod Talbott Whittaker

USF Tampa Graduate Theses and Dissertations

The main purpose of this thesis is to investigate the ductility and application of titanium alloys, like titanium 6Al-4V, when used in aerospace fasteners compared to more conventional stainless steel aerospace fasteners such as A286. There have been concerns raised about the safe usability of titanium 6-4 in the aerospace industry due to its lack of strain hardening. However, there is a lack of data pertaining to this concern of safe usage which this thesis aims to address. Tensile tests were conducted to find the ductility indexes of these fasteners which quantify the amount of plastic to elastic elongation. From …

An Investigation On The Band Gap And Band Edge Of Semi-Conducting Lanthanum Transition Metal Perovskites For Photocatalytic Applications, Divya Suresh

USF Tampa Graduate Theses and Dissertations

For the past few decades, a frenzy of attention has been given towards the development of an assortment of photocatalysts as a solution for various environmental problems. TiO2 is the most widely used photocatalyst. TiO2 is biocompatible, chemically and thermally stable but TiO2 and a vast majority other photocatalysts have large band gaps, and hence they find applicability only in the UV region of the solar spectrum. These large band gap photocatalysts suffer a severe limitation with regard to their overall process efficiency as the UV region contributes to about 3 to 4 % of the solar spectrum in terms …

Production And Characterization Of Composite Nano/Micro Sized Particles By Rapid Expansion Of Supercritical Solutions (Ress) Co-Precipitation, Beidi He

Dissertations

Nanoscale composites of hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX) and polymer binders were produced by co-precipitation using rapid expansion of supercritical solutions (RESS). The binders used in this study are poly (vinylidene fluoride-co-hexafluoropropylene) (VDF-HFP22), polystyrene (PS) and 7-amino-4-methyl coumarin (AMC). The RDX/VDF-HFP22 and RDX/PS co-precipitated nanoparticles were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). The average size of produced nanoparticles is ca. 100 nm. TEM analysis of RDX/PS nano-composite shows a core-shell structure with RDX as the core material and the shell consisting of the polymeric binder. X-ray Powder Diffraction (XRPD) analysis …

Corrosion Fatigue Crack Growth Behavior At Notched Hole In 7075-T6 Under Biaxial And Uniaxial Fatigue With Different Phases, Ali Khawagi

Theses and Dissertations

This research investigates fatigue crack propagation behavior in both air and saltwater (3.5% NaCl) environments from pre-cracked notched circular hole in a 7075-T6 cruciform specimen. With stress ratio of 0.5, biaxility stress ratio of unity, and frequency of applied load of 10 Hz, the crack growth behavior was investigated under in-plane biaxial tension-tension fatigue with 45⁰, 90⁰ and 180⁰ phase difference conditions and then compared to previous fatigue tests with no phase difference to study the effect of changing the phase differences between the applied loads on the crack growth rate. Finite Element Analysis (FEA) was used to calculate cyclic …

Diamond Coated Wire Cutting Of Solar Si Ingots: New Insights Using Raman Microspectroscopy, Junting Yang

McKelvey School of Engineering Theses & Dissertations

Diamond embedded abrasive wire (henceforth called diamond wire) sawing process of Si is a highly efficient technique for rapid wafering of solar Si ingots. However, the root causes for cutting efficiency losses are unknown. One approach to understanding this complex process is to study 1) diamond particles on diamond coated wire (DCW) and 2) Si swarf collected during cutting process. In this thesis, we use confocal, micro Raman spectroscopy to unravel loss mechanisms of wafer sawing efficiency.

In the first part, we analyze the diamond microparticles which perform the sawing. By analyzing the phase transformation and stress distribution on single …