Physical Sciences and Mathematics Commons^™

Development Of Flexible Nickel-Zinc And Nickel-Iron Batteries, Xianyang Meng

Dissertations

The fabrication of flexible nickel-zinc batteries using a facile mixing of electroactive components for electrode preparation is presented. Polytetrafluoroethylene (PTFE) is found to be an effective binder by reducing concentration polarization, providing chemical/physical stability and enhancing flexibility. The zinc electrode containing PTFE maintains its original porous morphology even after hundreds of cycles while polymers such as PEO show morphology change. Each component, as well as the assembled flexible cells show desired flexibility and stability even under bending conditions.

The fabrication of flexible nickel-iron batteries using printable composite electrodes embedded with multiwalled carbon nanotubes (CNT) is also presented. All the metal …

Optimization Of Useful Hard X-Ray Photochemistry, David Lewis Goldberger

UNLV Theses, Dissertations, Professional Papers, and Capstones

X-ray induced damage is generally considered a nuisance, but in the field of Useful Hard X-ray Photochemistry we harness the highly ionizing and penetrating properties of hard X-rays (> 7 keV) to initiate novel photochemical decomposition and synthesis at ambient and extreme conditions. Preliminary experiments suggest that the energy of irradiating photons and the sample pressure play roles in determining the nature of X-ray induced damage. Here, we present the X-ray energy dependence of damage induced in strontium oxalate, strontium nitrate, and barium nitrate, as well as the pressure dependence of X-ray induced damage of strontium oxalate. Our results indicate …

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Linking Structure And Dynamics In Metallic Liquids: A Combined Experimental And Molecular Dynamics Approach, Robert Ashcraft

Arts & Sciences Electronic Theses and Dissertations

A major outstanding problem in condensed matter physics is the nature of the glass transition, in which a rapidly cooled liquid can bypass the transition into a crystalline state and the liquid structure is "frozen-in" due to kinetic arrest. To characterize the fundamental features behind this transition the liquid, both in the high temperature (equilibrium) and supercooled state, needs to be better understood. By examining the relationship between structure and dynamics a better characterization of the liquid state and a determination of the mechanisms that are ultimately important for the formation of the glass can be gained. In this dissertation, …

Corrosion Dynamics Of Carbon Steel In Used Fuel Container Environments, Dan Guo

Electronic Thesis and Dissertation Repository

The current Canadian used nuclear fuel container (UFC) design uses a pressure‑grade carbon steel (CS) vessel with its outer surface coated with a thin layer of copper. One concern regarding the structural integrity of the UFC design is the potential internal corrosion of the CS vessel. Moisture trapped inside a UFC could condense within the gap between the hemispherical head and the cylindrical body of the vessel. The internal UFC environment will be exposed to a continuous flux of ionizing radiation arising from the decay of radionuclides trapped in the used UO₂ fuel matrix.

This thesis research project investigates …

Application Of Silicon Nanohair Textured P-N Junctions In A Photovoltaic Device, Michael Small

Electronic Theses and Dissertations

The goal of this project is to design and develop a fabrication process for a silicon photovoltaic device which incorporates a nanohair textured p-n junction. The silicon nanowires are etched into a silicon wafer, comprising an epitaxial p-layer on n-substrate, via metal-assisted chemical etching (MACE). The resulting nanowires contain p-n junctions that lie along the length of the vertical nanowires. This construct has the potential to increase the optical bandwidth of a silicon photovoltaic device by allowing a greater amount of short wavelength light to reach the junction. In addition, the MACE method of nanofabrication has the potential for decreasing …

Fabrication And Characterization Of Electrochemical Glucose Sensors, Mohammed Marie

Graduate Theses and Dissertations

Electrochemical sensors based on the nanostructure of the semiconductor materials are of tremendous interest to be utilized for glucose monitoring. The sensors, based on the nanostructure of the semiconductor materials, are the third generations of the glucose sensors that are fast, sensitive, and cost-effect for glucose monitoring.

Glucose sensors based on pure zinc oxide nanorods (NRs) grown on different substrates, such ITO, FTO, and Si/SiO2/Au, were investigated in this research. Silicon nanowire (NW)- based glucose sensors were also studied. First, an enzyme-based glucose sensor was fabricated out of glass/ITO/ZnO NRs/BSA/GOx/nafion membrane. The sensor was tested amperometrically at different glucose concentrations. …

Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, Kyoungtae Kim

Dissertations

Preparation and characterization of tin fluorophosphate glass (Pglass) matrix nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) were investigated on the structural, thermal, morphological, mechanical, and rheological properties. Various processes including synthesis, extrusion and sintering processes were applied to prepare the nanocomposite samples. Another application of POSS with hydrophobic functional groups on the well-structured nanoscale silicate cage with three silanol groups was investigated to present the feasibility to use POSS molecule as a coating material on the surface of the hydrophilic inorganic glass. In addition, Poly(ethylene terephthalate) polymer matrix composites incorporating Pglass was studied to present the benefits of the Pglass with …

Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh

Doctoral Dissertations

Metamaterials (MMs) are nanocomposite materials consisting of metal-dielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications …

Early Detection Of Corrosion Via Hydrogel-Based Spectroelectrochemical Sensors, Capri Ann Price

Dissertations and Theses

The backbone of the industrialized world is comprised of refined, zerovalent metal, a material which thermodynamically favors an oxidative return to more chemically stable states. There are many methods used to slow or delay this process, such as protective coatings, sacrificial anodes, and alloys, but no method can entirely prevent corrosion. This body of work instead proposes detecting the earliest chemical markers of corrosion: that is, metal ions as they solubilize from a metal surface. Such information would allow maintenance personnel to make informed decisions about the necessity or lack thereof of preventive maintenance, and intervene before advanced damage has …

Swelling Induced Deformation Of Thermally Responsive Hydrogels, Ying Zhou

Doctoral Dissertations

Hydrogels are crosslinked polymeric networks imbibed with aqueous solutions. They undertake dramatic volume changes through swelling and deswelling processes, which can be stimulated by factors like temperature, pH or different chemicals. These unique properties render hydrogels particularly interesting for shape morphing related applications. In this thesis, we focus on the swelling induced deformation of thermally responsive hydrogels with lower critical solution temperatures (LCSTs), including poly(N-isopropylacrylamide) (PNIPAm) and poly(N,N-diethylacrylamide) (PDEAm). Particularly, benzophenone containing monomers are copolymerized with NIPAm or DEAm to create photocrosslinkable temperature-responsive polymers, which allows fabrication of hydrogels with controlled shapes and crosslinking …

Parallel Algorithms For Time Dependent Density Functional Theory In Real-Space And Real-Time, James Kestyn

Doctoral Dissertations

Density functional theory (DFT) and time dependent density functional theory (TDDFT) have had great success solving for ground state and excited states properties of molecules, solids and nanostructures. However, these problems are particularly hard to scale. Both the size of the discrete system and the number of needed eigenstates increase with the number of electrons. A complete parallel framework for DFT and TDDFT calculations applied to molecules and nanostructures is presented in this dissertation. This includes the development of custom numerical algorithms for eigenvalue problems and linear systems. New functionality in the FEAST eigenvalue solver presents an additional level of …

Ultra-Low Temperature Properties Of Correlated Materials, Seyed Mohammad Ali Radmanesh

University of New Orleans Theses and Dissertations

Abstract

After the discovery of topological insulators (TIs), it has come to be widely recognized that topological states of matter can actually be widespread. In this sense, TIs have established a new paradigm about topological materials. Recent years have seen a surge of interest in topological semimetals, which embody two different ways of generalizing the effectively massless electrons to bulk materials. Dirac and, particularly, Weyl semimetals should support several transport and optical phenomena that are still being sought in experiments. A number of promising experimental results indicate superconductivity in members of half-Hesuler semimetals which realize the mixing singlet and triplet …

High Dynamic Range Optical Devices And Applications., Elijah Robert Jensen

Electronic Theses and Dissertations

Much of what we know about fundamental physical law and the universe derives from observations and measurements using optical methods. The passive use of the electromagnetic spectrum can be the best way of studying physical phenomenon in general with minimal disturbance of the system in the process. While for many applications ambient visible light is sufficient, light outside of the visible range may convey more information. The signals of interest are also often a small fraction of the background, and their changes occur on time scales so quickly that they are visually imperceptible. This thesis reports techniques and technologies developed …

Dynamics And Structure Of Polyelectrolyte Complexes, Hamidreza Shojaei-Mahib

Doctoral Dissertations

Interaction of charged macromolecules among themselves and with charged interfaces in salty aqueous medium is a common phenomenon prevalent in biology and synthetic systems. We have addressed several inter-related issues in this general context. First we present a theory of adsorption of polyelectrolytes on the interior and exterior surfaces of a charged spherical vesicle. We derive the critical adsorption condition and the density profile of the polymer in terms of various characteristics of the polymer, vesicle, and the solution, such as the length and charge density of polymer, the radius and charge of the vesicle, the salt concentration of the …

Self-Assembling Networks In Soft Materials, Ishan Prasad

Doctoral Dissertations

This dissertation presents a study on heterogeneous network structure in two distinct classes of soft material systems: disordered assemblies of jammed binary spheres and ordered morphologies of block copolymer melts. The aim is to investigate the combined role of geometry and entropy in structure formation of soft matter assemblies. First, we investigate the influence of particle size asymmetry on structural properties of jammed binary sphere mixtures. We give evidence of two distinct classes of materials separated by a critical size ratio that marks the onset of a sharp transition due to simultaneous jamming of a sub-component of the packing. We …

The Effect Of Processing Conditions On The Energetic Diagram Of Cdte Thin Films Studied By Photoluminescence, Shamara P. Collins

USF Tampa Graduate Theses and Dissertations

The photovoltaic properties of CdTe-based thin films depend on recombination levels formed in the CdTe layer and at the heterojunction. The localized states are resultant of structural defects (metal sublattice, chalcogen sublattice, interstitial), controlled doping, deposition process, and/or post-deposition annealing. The photoluminescence study of CdTe thin films, from both the bulk and heterojunction, can reveal radiative states due to different defects or impurities. Identification of defects allows for potential explanation of their roles and influence on solar cell performance. A thorough understanding of the material properties responsible for solar cell performance is critical in further advancing the efficiency of devices. …

Non-Destructive Evaluation For Composite Material, Desalegn Temesgen Delelegn

Electrical & Computer Engineering Theses & Dissertations

The Nondestructive Evaluation Sciences Branch (NESB) at the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) has conducted impact damage experiments over the past few years with the goal of understanding structural defects in composite materials. The Data Science Team within the NASA LaRC Office of the Chief Information Officer (OCIO) has been working with the Non-Destructive Evaluation (NDE) subject matter experts (SMEs), Dr. Cheryl Rose, from the Structural Mechanics & Concepts Branch and Dr. William Winfree, from the Research Directorate, to develop computer vision solutions using digital image processing and machine learning techniques that can help identify …

Structural Studies To Determine The Mechanisms Supporting Multiferroic And Ferroelectric Properties Of Complex Oxides, Han Zhang

Dissertations

Multiferroics are a class of materials which possess both magnetic and electrical polarization with possible coupling between them. They show promise to enable new sensors and data storage devices with novel features, such as the possibility of writing polarization bits with magnetic fields at low power. The coexisting magnetic and ferroelectric order parameters are usually weakly coupled, preventing practical use. The development and study of new classes of materials with large magnetoelectric couplings is of high importance. Understanding the structure of these materials is key to this effort.

As one class of these systems, the RX3(BO₃)₄ has …

Investigation Of The Effects Of Harmful Radiation On Type-Ii Strained Layer Superlattice Focal Plane Arrays Operated In The Long Wave Infrared, Patrick Fumo

Electrical Engineering Theses and Dissertations

In-situ exposure of InAs/InAsSb strained layer superlattice focal plane arrays to gamma-rays revealed the possibility of a detector capable of imaging through a total ionizing dose event. Two long wave infrared focal plane arrays were exposed to a Co⁶⁰ source at dose rates of 60 Rads/s and 70 Rads/s in incremental steps up to a total accumulated dose of 30 kRads. The first device showed no degradation in dark current density with accumulated dose while the second device tested showed a small increase up to 1 kRad and minimal increases with subsequent dose steps. The primary imaging defect in …

Ii-Vi Semiconductor Nanowire Array Sensors Based On Piezotronic, Piezo-Phototronic And Piezo-Photo-Magnetotronic Effects, Shuke Yan

University of New Orleans Theses and Dissertations

With the rapid progress of nanotechnologies, there are two developing trends for the next generation of sensors: miniaturization and multi-functionality. Device miniaturization requires less power consumption, or even self-powered system. Multi-functional devices are usually based on multi-property coupling effects. Piezoelectric semiconductors have been considered to be potential candidates for self-powered/multi-functional devices due to their piezotronic coupling effect. In this dissertation, ZnO and CdSe nanowire arrays have been synthesized as the piezoelectric semiconductor materials to develop the following self-powered/multi-functional sensors: (1) self-powered gas sensors of ZnO/SnO₂, ZnO/In₂O₃, ZnO/WO₃ and CdSe nanowire arrays have been …

A Novel Approach To Analyzing Strain Heterogeneity In Polycrystalline Quartz Specimens Deformed At High Pressure And Temperature, Nolan Ambrose Regis

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rheological studies of rocks and minerals allow researchers to study the grain-scale deformation mechanisms that govern large-scale geologic processes from mountain building to mantle mixing. Deforming rock samples with high pressure and temperature apparatuses similar to the Griggs piston cylinder apparatus allows us to simulate deformation at depth. However, many apparatuses are limited to “cook-and-look” analysis and require modeling techniques to determine the evolution of deformation patterns found in experimental samples. A previous study used two-dimensional finite element models to analyze the development of stress and strain patterns in polycrystalline rocks. The study suggested rhythmic patterns in deformed rocks develop …

Effects Of Tension On Resonant Frequencies Of Strings, Blake Burnett

Senior Theses

This project tests and explores resonance of strings. Since all materials and mechanisms are affected by vibrations, it is important to know the frequencies at which resonance occurs. To explore this subject, strings were used as a model material to test the effect tension has on resonance. The fundamental frequencies and the corresponding modes of resonance were used to analyze the data. The results of this experiment show that increasing tension on a string increases its resonance frequency. Understanding the physics behind resonance frequency allows systems to be designed to take advantage of resonance properties, or to avoid resonance where …

Thermoelectrics And Thermoelectric Devices, Benjamin T. Erck

Senior Theses

The field of thermoelectrics has many applications, and more are found in everyday systems. From its current studies, it is apparent that improving the figure of merit zT (which defines a good thermoelectric material) is important in the effectiveness of power generation. Another important part of thermoelectrics is the duality of these devices. They can both move heat and generate power, depending on their role in the system. In this thesis research, a process was made to test these thermoelectric relationships for a few Peltier devices in order to understand their efficiencies and what systems they can be applied to.

Measuring The Double Layer Capacitance Of Electrolyte Solutions Using A Graphene Field Effect Transistor, Agatha Ulibarri

Senior Theses

When operating graphene field effect transistors (GFETs) in fluid, a double layer capacitance (C_dl) is formed at the surface. In the literature, the C_dl is estimated using values obtained using metal electrode experiments. Due to the distinctive electronic and surface properties of graphene, there is reason to believe these estimates are inadequate. This work seeks to directly characterize the double layer capacitance of a GFET. A unique method for determining the C_dl has been implemented, and data has been obtained for three electrolytes and one ionic fluid. The results yield dramatically lower C_dl values than …

New Approaches To Multi-Functional Soft Materials, Seyedali Banisadr

Theses and Dissertations

Soft robotics is a relatively new, but fast-developing field of science and technology that utilizes soft materials such as polymers in their body structure. Despite significant progress in soft robotic devices, robots that can sense their environments are still very rare. Although some soft robots have exhibited sensing capabilities, they still have not demonstrated synergistic coupling of sensing and actuation. From our perspective, this type of coupling may take us one step closer to fabricate soft robots with autonomous feedback dynamics. In this work, we present new approaches to soft robotic devices, which are fabricated from responsive soft materials and …

Novel Solar Cells Based On Two-Dimensional Nanomaterials And Recycled Lead Components, Xiaoru Guo

Theses and Dissertations

To meet the rapidly growing demand for energy and reduce the use of dwindling fossil fuels, the efficient utilization of renewable energy is a constant pursuit globally. Because solar cells convert vastly available sunlight into electricity, developing high-performance and low-cost solar cells is a top strategy for future energy supply. Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) are the most promising choices. In the meantime, highly concentrated sulfuric acids from retired lead-acid batteries become an environmental concern, and lead contamination in drinking water raises concerns in general public. This study addresses both above-mentioned problems by using two-dimensional (2D) …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

The Incorporation Of Graphene To Lithium Cobalt Oxide As A Cathode To Improve The Performance Of Lithium Ion Batteries, Kenan Wang

Graduate Theses and Dissertations

One of the objectives of this thesis work was to investigate the cathode performance of lithium cobalt oxide (LiCoO2) incorporated with graphene powder in lithium ion batteries (LIBs). Graphene powder was incorporated into cathode materials to enhance the performance of LIBs. The other objective was to impede the construction of a solid electrolyte interphase (SEI) sheet using graphene sheet coating on its cathode.

The results of this work show that adding graphene powder improved the performance of LiCoO¬2 as a cathode material. With the incorporation of different weight percentages of graphene powder, the LiBs showed distinct changes in their charging …

Near Bandgap Two-Photon Excited Luminescence Of Inas Quantum Dots, Xian Hu

Graduate Theses and Dissertations

Semiconductor quantum dots (QDs) confine carriers in three dimensions, resulting in atomic-like energy levels as well as size-dependent electrical and optical properties. Self-assembled III-V QD is one of the most studied semiconductor QDs thanks to their well-established fabrication techniques and versatile optical properties. This dissertation presents the photoluminescence (PL) study of the InAs/GaAs QDs with both above bandgap continuous-wave excitation (one-photon excitation) and below-bandgap pulse excitation (two-photon excitation). Samples of ensemble QDs, single QD (SQD), and QDs in a micro-cavity, all grown by molecular beam epitaxy, are used in this study. Morphology of these samples was examined using atomic force …