Engineering Science and Materials Commons^™

Upcyclying Of Polyethylene Terephtalate By Addition Of Thermoplastic Elastomer, Diego Francisco Bermudez

Open Access Theses & Dissertations

Continual overconsumption of single-use plastics has generated challenges of solid waste management across the United States. Common plastic waste management solutions, such as landfill, have caused the migration of contaminants into the environment consequently affecting not only the health of wildlife, but also that of human beings. Alternative strategies for the handling of single-use plastic such as polyethylene terephthalate (PET), used in the food packaging industry, can ultimately help mitigate the noxious consequences of single-use plastics affecting entire ecosystems. This study demonstrates a potential avenue of materials upcycling by studying the effects of coupling PET with the thermoplastic elastomer styrene-ethylene-butylene-styrene …

Design And Development Of Transition Metal-Based Electrocatalysts For Environmentally Friendly And Efficient Hydrogen Evolution Reactions (Her), Navid Attarzadeh

Open Access Theses & Dissertations

Hydrogen fuel is a clean energy source primarily because it emits no carbon dioxide (CO2). Sustainable energy alternatives have attracted the scientific community and policymakers as concerns over global warming and depletion of fossil fuels have increased significantly. Substituting H2 gas as a primary source for our daily energy consumption under the guideline of the hydrogen economy concept has not progressed as anticipated because of inadequate efficiency associated with the generation (electrolyzer) and utilization (fuel cell) devices. However, there are challenges associated with hydrogen that must be overcome for it to become a truly sustainable and widespread energy source. The …

Electrochemical Approaches To Life-Support Resources In Space Missions And Nuclear Technologies: Hydrogen Peroxide And Uranium Films, Armando Manuel Pena-Duarte

Open Access Theses & Dissertations

Space race has developed several technological advances that have achieved and continue to achieve the success of space missions in the aerospace timeline. Currently, the number of space technical and scientific innovations is still growing––demanding new materials and developments for extreme performing applications of fuel cells, batteries, supercapacitors, and systems of nuclear energy. Space missions require life-support solutions, auto-sustainable closed-loop living environments, cleaning and sanitizing solutions against pathogens, and safe nuclear-based resources of energy––with fissile materials with well-controlled dimensions within the core fuel elements. Likewise, to guarantee safety conditions, reduce costs, and facilitate operational logistics, space missions must reduce their …

Thermal Behavior Of Plain And Fiber-Reinforced Rigid Concrete Airfield Runways, Arash Karimi Pour

Open Access Theses & Dissertations

The environmental condition and temperature gradient are important factors resulting in concrete airfield runways cracking during the time. Rigid concrete airfield runways experience different thermal gradients during the day and night due to changes in air temperature. Curling and thermal expansion stresses are the main consequences resulting in various types of cracking over the surface and thickness of concrete airfield runways and increasing maintenance costs. The curvature of concrete slabs increases with an increase in the temperature gradient which is amplified when runways open to traffic. Additionally, the combination of the curling and shrinkage stresses, in rare circumstances, can be …

Sulfonated Styrene Grafted Sebs/Abs Made By Additive Manufacturing For Ion Exchange Applications, Avianna Elaine Gallegos

Open Access Theses & Dissertations

An interpenetrating polymer network (IPN) for cation exchange applications was synthesized from a blend of styrene-ethylene/butylene-styrene (SEBS) and acrylonitrile butadiene styrene (ABS), which was 3D printed, grafted with crosslinked polystyrene (PS), and sulfonated. A method for styrene grafting was applied to reduce the damage to polymer phases caused by the sulfonation reaction. Styrene and divinylbenzene monomers were introduced to the IPN and induced with heat treatment to polymerize in situ. The graft copolymerization reaction was enhanced with varying quantities of benzoyl peroxide as a chemical initiator. The samples were subsequently sulfonated with chlorosulfonic acid in dichloroethane and functionalized for ion …

Nano-Engineered Soft Magnets: Potential Application In Water Treatment, Hyperthermia And Molecular (Organic) Magnets, Yohannes Weldemariam Getahun

Open Access Theses & Dissertations

Scrutinizing the remarkable and tunable properties of magnetic materials at a nanoscale size "There's Plenty of Room at the Bottom..." Richard Feynman, this study attempts to find sustainable solutions to some of the deteriorating environmental, health, and energy problems the world is encountering. Due to their simple preparation, surface adaptability, and tunable magnetic and optical properties, magnetic nanoparticles have been extensively investigated in water treatment, cancer therapy, data storage, and more. However, relying on non-reusable and chemical-based treatment agents in water, complex and costly cancer treatment procedures and molecular magnets that operate far below room temperature limited those attempts from …

The Qualification Of Sealability And Creep Relaxation Of Additively Manufactured Zytel Gaskets For Pem Fuel Cells, Robert Lazarin

Open Access Theses & Dissertations

The purpose of this thesis is to study the feasibility of low-cost additive manufacturing of gaskets for proton exchange membrane fuel cells exposed to extreme temperature conditions ranging from -55°C to 100°C. With the growing popularity and decreasing costs of additive manufacturing technologies, specifically Material Extrusion (ME), research is being conducted to determine the feasibility of ME components. Thermally cycled PEMFCs may exhibit accelerated gasket deterioration, therefore, the mechanical stability of material extruded gaskets following a harsh thermal cycle must be assessed. The feasibility of the material extruded gaskets will be proven by manufacturing optimization and mechanical testing. The target …

Magnetic Structures Of Sawtooth Olivines Mn2six 4 (X = S, Se) Determined Through Neutron Powder Diffraction, Melaku Sisay Tafere

Open Access Theses & Dissertations

In olivine chalcogenide Mn2SiX 4 (X = S, Se) compounds, the Mn lattice produces a sawtooth, which is of critical significance in magnetism due to the potential for manifesting at bands in the magnon spectrum, a crucial component in magnonics. The compounds Mn2SiS4 and Mn2SiSe4 in Mn2SiX 4 family undergo antiferromagnetic phase transitions at T â?? 85 K and â?? 66 K, respectively, as determined from the specific heat, Cp(T). The average and local crystal structuresare determined using synchrotron X-ray, neutron diffraction, and X-ray total scattering data followed by Rietveld and pair distribution function (PDF) analysis. It is found from …

Pressure-Induced Phase Transition And Electronic Structure Changes In Equiatomic Fev, Homero Reyes Pulido

Open Access Theses & Dissertations

Classical molecular dynamics methods can accurately describe a broad set of many-atomssystems. Although more economical, the results given by this framework lack the precision capable of density functional theory (DFT). Therefore, the structural stability of the B2 phase of a body-centered-cubic iron-vanadium (FeV) alloy using DFT on the electronic structure level is analyzed to verify and further explain classical results obtained by our group in this same alloy. Using Quantum Espresso and Phonopy for the computational simulations, the plotted band structure, electronic density of states (eDOS), phonon dispersions, charge density, and Fermi surfaces for various compressed unit cells are presented. …

Rational Design Of Composite Nanomaterials For Water Treatment Applications, Mariana Marcos-Hernandez

Open Access Theses & Dissertations

Water quantity and quality have been affected in communities all around the world due to population growth, pollution, changes in land use, and climate change. In order to cope with existing and anticipated water demands and shortages, the use of treated or reclaimed water is an ongoing alternative that has helped communities all over the world address this problem. The adaptation of nanotechnology to traditional water and wastewater treatment processes offers new opportunities in technological developments. Unique size-dependent properties such as: high surface to mass ratio, high reactivity, high sorption capacities, fast dissolution, superparamagnetism, among others, provide high-tech efficient materials …

Material Synthesis And Machine Learning For Additive Manufacturing, Jaime Eduardo Regis

Open Access Theses & Dissertations

The goal of this research was to address three key challenges in additive manufacturing (AM), the need for feedstock material, minimal end-use fabrication from lack of functionality in commercially available materials, and the need for qualification and property prediction in printed structures. The near ultraviolet-light assisted green reduction of graphene oxide through L-ascorbic acid was studied with to address the issue of low part strength in additively manufactured parts by providing a functional filler that can strengthen the polymer matrix. The synthesis of self-healing epoxy vitrimers was done to adapt high strength materials with recyclable properties for compatibility with AM …

Suitability Of Low-Cost Additive Manufacturing For Polymer Electrolyte Fuel Cells, David Alexander

Open Access Theses & Dissertations

The purpose of this dissertation is to study the feasibility of low-cost additive manufacturing to fabricate polymer electrolyte fuel cell bipolar plate materials. Traditional manufacturing techniques include molding, milling, hollow embossing, hydro-forming, rolling, and electromagnetic forming. These processes are employed when a design has been selected due to higher costs at low volumes. The combination of high initial costs and bipolar plates being the most expensive component of the polymer electrolyte fuel cell creates incentive to mitigate this obstacle. The feasibility of low-cost additive manufactured bipolar plates will be proven by fabrication, post-processing, and characterization of printed test specimen. The …

Evolution Of The Magnetic Properties On Van Der Waals Layered Magnets Via Pressure And Proton Irradiation, Rubyann Olmos

Open Access Theses & Dissertations

Probing the magnetism in quasi two-dimensional materials has the potential in driving their properties towards future use in spin electronic based devices. Studying such layered magnets will enable the scientific community to uncover tunable exotic phases such as superconductivity, quantum paramagnetism, etc. This work examines the influence of two types of external perturbations, namely, the pressure and proton irradiation, on the magnetic properties of several compounds in the van der Waals crystal family.

Pressure has been found to induce structural and magnetic phase transitions in many of these materials. Using hydrostatic pressure as a disorderless approach to manipulate the interlayer …

Rational Design Of Multifunctional Nanocatalysts For Environmental Remediation And Energy Conversion Technologies, Md Ariful Ahsan

Open Access Theses & Dissertations

The discovery of efficient and sustainable carbon-based nanotechnologies to solve both the scarcity of drinking water and global energy crisis has become a paramount task in the last decades. Owed to the fast population growth and industrialization of the modern society, access to potable water and clean energy technologies is becoming very hard around the globe. Water pollutants have become a serious threat to the environment and ecology because of their toxic nature. Parallelly, the current hydrocarbon-based fuel industries are generating high levels of contamination across the planet, making imperative the development of cleaner energy technologies. In this regard, the …

Synthesis, Characterization, And Direct-Ink-Writing Of Syntactic Foams, Andrea Irigoyen

Open Access Theses & Dissertations

This project encompasses three different methods to fabricate syntactic foams using a PDMS matrix i.e., hollow spheres inclusion, pore generator leaching by solvent, and emulsion. The foam formation by using polysiloxane hollow spheres is done in a 3-step process. The first step is to create a core of polystyrene following a dispersion polymerization process. The goal for the size of the pore is to monodisperse and have an average diameter of 5-10 μm, so the polystyrene core must be as well within that range. After that, the cores are coated with a polysiloxane shell by following a polymerization by condensation …

Magnesiothermic Combustion Synthesis Of Nanocrystalline Silicon And Oxidation Kinetics Of Magnesium Particles, Sergio Cordova

Open Access Theses & Dissertations

Magnesium (Mg) is a well-known reduction agent in metallurgy (more specifically, in metallothermy). Recently, magnesiothermic reduction of oxides has been used in self-propagating high-temperature synThesis (SHS) of advanced materials such as ultrahigh-temperature ceramics (UHTC). The magnesiothermic SHS has also been used for the conversion of silica (SiO2) to silicon-based materials for thermoelectric applications. However, since oxidation of Mg releases a lot of heat, the direct use of it as the reduction agent leads to excessively high temperatures and undesirable sintering of the products. We have proposed to use magnesium silicide (Mg2Si) instead of Mg in the SHS of nanostructured silicon. …

High Frequency Electron Spin Resonance Investigations On Quasi-Two-Dimensional Chromium Halide Magnets, Christian Saiz

Open Access Theses & Dissertations

Broadening the knowledge and understanding on the magnetic correlations in van der Waals layered magnets is critical in realizing their potential next-generation applications in devices such as spintronics. In this study, we employ high frequency (ν = 120 GHz, 240 GHz) electron spin resonance (ESR) spectroscopy on plate-like CrX3 (where X = Cl, Br, I) to gain insight into the magnetic interactions as a function of temperature (200 – 4.4 K) and the angle of rotation θ (degrees). We find that the temperature dependence of the ESR linewidth is well described by the Ginzburg-Landau critical model, indicative of antiferromagnetic correlations …

A Study Of The Frustrated Honeycomb Battery Material Na2ni2teo6, Nathan Christopher Episcopo

Open Access Theses & Dissertations

The P2-type layered hexagonal compound Na2Ni2TeO6 with Ni2+ on a honeycomb lattice was synthesized by the standard solid-state route. Structural characterization chemical phase purity was confirmed by Rietveld refinement of laboratory and synchrotron data. The crystal structure refines well in the P63/mcm space group. Single crystal growth trials using the self-flux-melt method were conducted with limited success. The magnetic transition temperature pertaining to Ni2+ lattice was confirmed by analysis of specific heat capacity to be . The magnetic susceptibility remains largely unchanged in magnetic field of and external pressure of . There is an almost linear response in isothermal magnetization …

Synthesis And Characterization Of Functiona Materials For 3d Printed Composites, Elizabeth Irene Reza

Open Access Theses & Dissertations

The following body of work encompasses the synThesis, upscaling, additive manufacturing, and characterization of microspheres as functional fillers incorporated into polymer syntactic foams. Synthesizing microspheres permits control over morphology, dispersion of particles, and size while the use of direct write manufacturing allowed for the controllability of filler orientation. Two different syntactic foams were developed from similar methodologies: (1) a silicone syntactic foam (2) epoxy syntactic foam. The silicone epoxy foam showed an increasing in damping and elastic modulus. The epoxy syntactic foams showed an enhanced thermal and electrical properties.

Investigation Of Iron Doped Gallium Oxide (Ga-Fe-O) System: Structure Property Relationship And Performance Evaluation For Optical And Catalytic Applications, Swadipta Roy

Open Access Theses & Dissertations

From September 2012 to May 2015, a phenocam monitored the seaward edge of a protected mangrove forest. Calculated GCC revealed seasonal greening patterns of a mangrove species, Rhizophoa apiculata, and an overall increase in the GCC, suggesting mangrove expansion. In comparing temperature and precipitation effects, it was found that this particular mangrove species had a greening optima at temperatures between 28°C and 28.5°C, and greening and canopy development response lag time of 10 weeks in response to precipitation. Tree saplings were monitored and showed to grow by 50%, mostly during a three month period during the rainy season. The establishment …

Development Of Software Tools And Experimental In Situ Electron Spin Resonance For Characterizing The Magnetic And Electrocatalytic Properties Of Transition Metal Chalcogenide Crystals, Jose Armando Delgado

Open Access Theses & Dissertations

Studying the magnetic properties and crystal defects of transition metal chalcogenide crystals is of paramount importance for utilizing them for next generation spintronics devices and hydrogen evolution reaction catalysts. Hydrothermally grown transition metal chalcogenide nanocrystals (MoS2, Ru2S3, Rh2S3, Co2S8) were chosen as catalysts for the hydrogen evolution reaction due to their low dimensionality and previous utilization as catalysts for hydrodesulfurization. The relationship between crystal defect sites and catalytic activity must be discerned to maximize the efficiency of hydrogen production during the hydrogen evolution reaction. ESR spectroscopy was utilized as a spin sensitive technique to study the defects and local changes …

Cmas/Volcanic Ash Infiltration Performance Of Yttria Rich-Zirconia Thermal Barrier Coatings Produced By Electron Beam Physical Vapor Deposition, Juan Jose Gomez Chavez

Open Access Theses & Dissertations

For many years the use of thermal barrier coatings (TBC) in gas turbine engines has allowed a significant increase in engine operating temperatures which are above the Ni-based super alloys' melting point. The base material for TBCs is the state of the art 7 wt % yttria stabilized zirconia (YSZ) which provides the thermal protection. Current industry demands for increased engine efficiency has pushed TBCs to the limits where significant technological constrains have been identified. One of the main ones represents the high temperature corrosion of the TBC material due to the ingestion of silicate based airborne particles commonly referred …

Computational Studies On Perovskite-Metallofullerene Interface And Magnetic Properties Of Mn-Based Mixed Olivines, Bethuel Omutiti Khamala

Open Access Theses & Dissertations

Methyl ammonium lead halide (MAPbX3) perovskite based solar cells have recently emerged as promising class of materials for photovoltaic applications with efficiencies reaching over 22%. Designing interfaces with strong binding is vital to developing efficient, high-performing solar cells. Fullerene-based materials are widely employed as efficient electron acceptors and can serve as electron transporting layer in perovskite based solar cells. We have studied interfaces of methyl ammonium lead iodide MAPbI3 with Sc3N@C80 fullerene and Sc3N@C80PCBM fullerene derivate within the density functional formalism. Different surface terminations and orientations of the methyl ammonium are examined for binding of the fullerene layer. Our calculated …

Solvent And Concentration Effects Governing The Hierarchical Organization Of Asphaltenes: A Small-Angle X-Ray Scattering Study, Hasan Rejoanur Rahman

Open Access Theses & Dissertations

Asphaltenes are a group of planar molecules found in crude oil and are prone to aggregation which often causes blockage of pipes along the oil production stream resulting a huge economic downside. In an effort to understand the hierarchical organization of asphaltene in different solvents and concentrations, the solution structure of various asphaltene solutions were studied using small-angle x-ray scattering (SAXS). Solvents were chosen based on miscibility maps. Such maps are generated on the critical value of the solubility parameter difference between asphaltenes or asphaltene components, and a range of solvents. The critical factors that affect asphaltene and asphaltene component …

Magnetic And Catalytic Properties Of Transition Metal Doped Mos2 Nanocrystals, Luis Martinez

Open Access Theses & Dissertations

Magnetism and catalytic activity of nanoscale layered two-dimensional (2D) transition metal dichalcogenides (TMDs) have gained an increasing research interest in the recent past. To broaden the current knowledge and understanding on this subject, in this work, together with my collaborators, I study the magnetic and electrocatalytic properties of hydrothermally grown pristine and transition metal doped (10% of Co, Ni, Fe and Mn) 2H-MoS2 nanosheets/nanocrystals (NCs), with the particle size of 25-30 nm. A broad range of experimental measurements such as x-ray diffraction, transmission electron microscopy, x-ray photo absorption spectroscopy, Raman spectroscopy, magnetic, catalytic and electron spin resonance have been employed …

Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer

Open Access Theses & Dissertations

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Raman Microscopic Analysis Of Internal Stress In Boron-Doped Diamond Thin Films, Emma M.A. Sundin

Open Access Theses & Dissertations

The correlations between induced stress on undoped and boron-doped diamond (BDD) thin films, sample chemical composition, and fabrication substrate are investigated in this study via confocal Raman microspectroscopic analysis. Stability of BDD films is relevant to fast-scan cyclic voltammetry, as film delamination and dislocation of BDD-coated electrodes that can occur during neurosurgical electrode implantation can negatively impact the biosensing reliability of this technique. Electrodes were fabricated by coating cylindrical tungsten rods using a custom-built chemical vapor deposition reactor. The results of the analysis reveal a direct correlation between regions of pure diamond and enhanced material stress, as well as preferential …

Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala

Open Access Theses & Dissertations

We have investigated the superspin dynamics of 5 nm and 10 nm mixed state Mn3O4 nanoparticles utilizing ac-susceptibility and electron paramagnetic resonance measurements. The out of phase component of the ac-susceptibility measurements show a magnetic anomaly below (T

Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle

Open Access Theses & Dissertations

A density functional theory (DFT) study on the geometric and electronic structure of C60 and Sc3N@C80 along with their adsorption on pristine single layer graphene (SLG) is presented. C60 is found to adsorb in two nearly degenerate configurations: (i) with a pentagon facing the SLG, which is the most stable one, and (ii) with a hexagon facing the SLG in a face-to-face perfect alignment, rarely common in Ï?â??Ï? interactions, 0.06 eV higher in energy. The calculated binding energy of 0.76 eV, which includes dispersion effects, is in good agreement with previous theoretical and experimental reports. On the contrary, Sc3N@C80 adsorption …

Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal

Open Access Theses & Dissertations

We present the most stable structures for VXSc3-XN@C2n (where X=1-3 and 2n=70, 76, 78 and 80) using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search procedure developed involved structural optimizations of thousands of fullerenes and correctly identifies the experimentally observed VSc2N@C80 and V2ScN@C80 isomer as the most stable structures. The structural analysis shows that a few V-doped endohedral fullerenes do not follow the isolated pentagon …