Engineering Commons^™

Computational Study Of Microstructure-Propertymechanism Relations In Ferroic Composites, Fengde D. Ma

Dissertations, Master's Theses and Master's Reports - Open

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Ferroic materials, as notable members of smart materials, have been widely used in applications that perform sensing, actuation and control. The macroscopic property change of ferroic materials may become remarkably large during ferroic phase transition, leading to the fact that the macroscopic properties can be tuned by carefully applying a suitable external field (electric, magnetic, stress). To obtain an enhancement in physical and/or mechanical properties, different kinds of ferroic composites have been fabricated. The properties of a ferroic composite are determined not only by the properties and relative amounts of the constituent phases, but also by the microstructure of individual …

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Modeling And Simulation Of Microstructures, Mechanisms, And Diffraction Effects In Energy Materials: Ferroelectrics And Lithium Ion Battery Cathode Materials, Jie Zhou

Dissertations, Master's Theses and Master's Reports - Open

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Ferroelectric materials, as a large family exploited for the application of sensors, transducers and random access memories, open up a remarkable ground both for fundamental science and industry. Dielectric and piezoelectric properties are of the most interest in ferroelectric materials, which motivate research to enhance ferroelectric properties based on various application purposes. Among the multitudinous candidates in ferroelectric family, pseudo binary solid solutions with ABO₃ lattice structure attract special attention in virtue of their large strain response when applying external loading. Furthermore, existence of morphological phase boundary (MPB) on their phase diagrams shed light on tuning material compositions to …

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Beautiful Forms And Compositions Are Not Made By Chance: Exploring The Efficacy Of Portable X-Ray Fluorescence To Sort And Source English Lead Glazed Ceramics, Steven J. Sarich

Dissertations, Master's Theses and Master's Reports - Open

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Advances in portable X-ray fluorescence (pXRF) technology have made it a viable option for the non-destructive exploration of the underlying chemical composition of ceramic artifacts for the purposes of classification. However, because the literature regarding the use of this instrument on historic artifacts is limited, it is necessary to begin with a broad scale exploratory assessment that might act as a jumping off point for future studies on this topic. Toward that end, this research uses a collection of British and Continental European ceramics ranging from 1650-1920, owned and curated by the Chipstone Foundation in Fox Point, WI, to explore …

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A Field Investigation Of Composite Mud Brick Compressive Strength, Kevin D. Hale

Dissertations, Master's Theses and Master's Reports - Open

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It has been highlighted in numerous publications that in the field of earth construction there is a strong disconnect between experimental work in the laboratory and its application in the field. The current study attempts to help bridge this gap with a field test conducted in Nampula, Mozambique. Mud bricks were made with a simple hand mold and reinforced with bamboo and straw fibers. Fibers were cut into lengths of 3 cm and 6 cm while being mixed in fractions of 0.125%, 0.25% and 0.50% by weight and compressive strength was measured using an application of the 3-point bending test. …

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Structures, Properties And Functionalities Of Magnetic Domain Walls In Thin Films, Nanowires And Atomic Chains: Micromagnetic And Ab Initio Studies, Liwei D. Geng

Dissertations, Master's Theses and Master's Reports - Open

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Structures, properties and functionalities of magnetic domain walls in thin film, nanowires and atomic chains are studied by micromagnetic simulations and ab initio calculations in this dissertation. For magnetic domain walls in thin films, we computationally investigated the dynamics of one-dimensional domain wall line in ultrathin ferromagnetic film, and the exponent α = 1.24 ± 0.05 is obtained in the creep regime near depinning force, indicating the washboard potential model is supported by our simulations. Furthermore, the roughness, creep, depinning and flow of domain wall line with commonly existed substructures driven by magnetic field are also studied. Our simulation results …

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Biological Materials: Part A. Temperature-Responsive Polymers And Drug Delivery And Part B. Polymer Modification Of Fish Scale And Their Nano-Mechanical Properties, Xu Xiang

Dissertations, Master's Theses and Master's Reports - Open

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This research has three parts. Two parts deal with novel nanoparticle assemblies for drug delivery, and are described in Part A, while the third part looks at properties of fish scales, an abundant and little-used waste resource, that can be modified to have value in medical and other areas.

Part A describes fundamental research into the affects of block sequence of amphiphilic block copolymers prepared from on a new and versatile class of monomers, oligo(ethylene glycol) methyl ether acrylate (OEGA) and the more hydrophobic di(ethylene glycol) methyl ether methacrylate (DEGMA). Polymers from these monomers are biologically safe and give polymers …

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In-Situ Tem Plasma Chip Nanofabrication And Characterization, Xuebo Cui

Dissertations, Master's Theses and Master's Reports - Open

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A silicon-based microcell was fabricated with the potential for use in in-situ transmission electron microscopy (TEM) of materials under plasma processing. The microcell consisted of 50 nm-thick film of silicon nitride observation window with 60μm distance between two electrodes. E-beam scattering Mont Carlo simulation showed that the silicon nitride thin film would have very low scattering effect on TEM primary electron beam accelerated at 200 keV. Only 4.7% of primary electrons were scattered by silicon nitride thin film and the Ar gas (60 μm thick at 1 atm pressure) filling the space between silicon nitride films. Theoretical calculation also showed …

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Development Of Precipitation Hardenable Al-Sc-Zr-Hf Quaternary Alloys Through Thermodynamic Modeling, And Room-Temperature And Elevated Temperature Hardness, Matthew J. Wong

Dissertations, Master's Theses and Master's Reports - Open

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Aluminum alloyed with small atomic fractions of Sc, Zr, and Hf has been shown to exhibit high temperature microstructural stability that may improve high temperature mechanical behavior. These quaternary alloys were designed using thermodynamic modeling to increase the volume fraction of precipitated tri-aluminide phases to improve thermal stability. When aged during a multi-step, isochronal heat treatment, two compositions showed a secondary room-temperature hardness peak up to 700 MPa at 450°C. Elevated temperature hardness profiles also indicated an increase in hardness from 200-300°C, attributed to the precipitation of Al₃Sc, however, no secondary hardness response was observed from the Al …

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Microwave Absorption Properties Of Tires, Yuzhe Zhang

Dissertations, Master's Theses and Master's Reports - Open

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The waste tire is belonging to insoluble high polymer elastic materials. It takes hundreds of years to resolve the macromolecules of waste tire into the standard which does not pollute the environment. More and more waste tires are air stored which causes space occupation and mosquito-breeding in the places that will spread diseases. The disposal methods include landfill, stockpiles, dumping and incising into particles. However, all these methods are not technically and economically efficient. The trend for the development of waste tire treatment processes is low cost, on-site, and high product recovery at high energy efficiency. In this project, microwave …

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Design, Synthesis And Applications Of Fluorescent And Electrochemical Probes, Giri K. Vegesna

Dissertations, Master's Theses and Master's Reports - Open

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“Seeing is believing” the proverb well suits for fluorescent imaging probes. Since we can selectively and sensitively visualize small biomolecules, organelles such as lysosomes, neutral molecules, metal ions, anions through cellular imaging, fluorescent probes can help shed light on the physiological and pathophysiological path ways. Since these biomolecules are produced in low concentrations in the biochemical pathways, general analytical techniques either fail to detect or are not sensitive enough to differentiate the relative concentrations. During my Ph.D. study, I exploited synthetic organic techniques to design and synthesize fluorescent probes with desirable properties such as high water solubility, high sensitivity and …

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Nano-Engineering Of Composite Material Via Reactive Mechanical Alloying/Milling (Rma/M), Edward Andrew Laitila

Dissertations, Master's Theses and Master's Reports - Open

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Attempts to strengthen a chromium-modified titanium trialuminide by a combination of grain size refinement and dispersoid strengthening led to a new means to synthesize such materials. This Reactive Mechanical Alloying/Milling process uses in situ reactions between the metallic powders and elements from a process control agent and/or a gaseous environment to assemble a dispersed small hard particle phase within the matrix by a bottom-up approach. In the current research milled powders of the trialuminide alloy along with titanium carbide were produced. The amount of the carbide can be varied widely with simple processing changes and in this case the milling …

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Development Of Practical Applications For Reprap Style 3-D Printers In Engineering, Benjamin T. Wittbrodt

Dissertations, Master's Theses and Master's Reports - Open

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The current rise in popularity of consumer level 3-D printers introduces a need to understand the application and material property capabilities of the technology. Presented here is data demonstrating the ability for the average U.S. consumer to recuperate the cost of a 3-D printer within one year of ownership. Additionally, using a consumer level 3-D printer, multiple photovoltaic (PV) racking systems were printed and produced with much lower cost compared to commercially available aluminum racking. Additionally, mechanical testing on 3-D printed components showed a temperature dependence on both percent crystallinity and ultimate tensile strength. Conclusions are drawn using the information …

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Faulted Structures In Li Ion Exchanged Namo2 (M=Ni(0.25)Mn(0.75)), Aaron M. Dewahl

Dissertations, Master's Theses and Master's Reports - Open

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A family of LiMO2 materials (M=Ni_0.25Mn_0.75) was prepared from Na_1.2-xLi_xMO_∂ precursors (0≤x≤0.6) via ion exchange. The resulting IE products were examined via XRD and compared to simulated XRD patterns produced using DIFFax to determine the defect structures resulting from the IE process. For the 0.1≤x≤0.6 materials, it is observed that there are 3 LiMO₂ sub-phases with different Li contents present. As the amount of Li in the precursor increases, the amount of each phase changes resulting in a net shift to higher 2-theta; corresponding to an overall decrease in lattice …

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Molecular Modeling Of Pmr-15 Polyimide, Fnu Pruthul Kokkada Ravindranath

Dissertations, Master's Theses and Master's Reports - Open

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PMR-15 polyimide is a polymer that is used as a matrix in composites. These composites with PMR-15 matrices are called advanced polymer matrix composite that is abundantly used in the aerospace and electronics industries because of its high temperature resistivity. Apart from having high temperature sustainability, PMR-15 composites also display good thermal-oxidative stability, mechanical properties, processability and low costs, which makes it a suitable material for manufacturing aircraft structures. PMR-15 uses the reverse Diels-Alder (RDA) method for crosslinking which provides it with the groundwork for its distinctive thermal stability and a range of 280-300 degree Centigrade use temperature. Regardless of …

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An Investigation Of Waste Glass-Based Geopolymers Supplemented With Alumina, Mary U. Christiansen

Dissertations, Master's Theses and Master's Reports - Open

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An increased consideration of sustainability throughout society has resulted in a surge of research investigating sustainable alternatives to existing construction materials. A new binder system, called a geopolymer, is being investigated to supplement ordinary portland cement (OPC) concrete, which has come under scrutiny because of the CO2 emissions inherent in its production.

Geopolymers are produced from the alkali activation of a powdered aluminosilicate source by an alkaline solution, which results in a dense three-dimensional matrix of tetrahedrally linked aluminosilicates. Geopolymers have shown great potential as a building construction material, offering similar mechanical and durability properties to OPC. Additionally, geopolymers have …

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Dysprosium Transport In Nd-Fe-B Pellets, Parawee Pumwongpitak

Dissertations, Master's Theses and Master's Reports - Open

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The addition of heavy rare earth (RE) elements to Nd2Fe14B based magnets to form (Nd,Dy)₂Fe₁₄B is known to increase the coercivity and high temperature performance required for hybrid vehicle electric motors and other extreme temperature applications. Attempts to conserve heavy rare earth elements for high temperature (RE)₂Fe₁₄B based magnets have led to the development of a grain boundary diffusion process for bulk magnets. This process relies on transport of a heavy rare earth, such as Dy, into a bulk Nd₂Fe₁₄B magnet along pores, a low volume fraction of …

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Parametric Study Of Reaxff Simulation Parameters For Molecular Dynamics Modeling Of Reactive Carbon Gases, Benjamin David Jensen

Dissertations, Master's Theses and Master's Reports - Open

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Abstract

The development of innovative carbon-based materials can be greatly facilitated by molecular modeling techniques. Although the Reax Force Field (ReaxFF) can be used to simulate the chemical behavior of carbon-based systems, the simulation settings required for accurate predictions have not been fully explored. Using the ReaxFF, molecular dynamics (MD) simulations are used to simulate the chemical behavior of pure carbon and hydrocarbon reactive gases that are involved in the formation of carbon structures such as graphite, buckyballs, amorphous carbon, and carbon nanotubes. It is determined that the maximum simulation time step that can be used in MD simulations with …

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Intergranular Corrosion And Stress Corrosion Cracking Of Extruded Aa6005a, David James Seguin

Dissertations, Master's Theses and Master's Reports - Open

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A research program focused on understanding the intergranular corrosion (IGC) and stress corrosion cracking (SCC) behavior of AA6005A aluminum extrusions is presented in this dissertation. The relationship between IGC and SCC susceptibility and the mechanisms of SCC in AA6005A extrusions were studied by examining two primary hypotheses.

IGC susceptibility of the elongated grain structure in AA6005A exposed to low pH saltwater was found to depend primarily on the morphology of Cu-containing precipitates adjacent to the grain boundaries in the elongated grain structure. IGC susceptibility was observed when a continuous (or semi-continuous) film of Cu-containing phase was present along the grain …

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The Processing Of Aluminum Gasarites Via Thermal Decomposition Of Interstitial Hydrides, Joseph James Licavoli

Dissertations, Master's Theses and Master's Reports - Open

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Gasarite structures are a unique type of metallic foam containing tubular pores. The original methods for their production limited them to laboratory study despite appealing foam properties. Thermal decomposition processing of gasarites holds the potential to increase the application of gasarite foams in engineering design by removing several barriers to their industrial scale production. The following study characterized thermal decomposition gasarite processing both experimentally and theoretically. It was found that significant variation was inherent to this process therefore several modifications were necessary to produce gasarites using this method. Conventional means to increase porosity and enhance pore morphology were studied. Pore …

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Synthesis Of Graphene And Its Applications For Dye-Sensitized Solar Cells, Hui Wang

Dissertations, Master's Theses and Master's Reports - Open

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Graphene, which is a two-dimensional carbon material, exhibits unique properties that promise its potential applications in photovoltaic devices. Dye-sensitized solar cell (DSSC) is a representative of the third generation photovoltaic devices. Therefore, it is important to synthesize graphene with special structures, which possess excellent properties for dye-sensitized solar cells.

This dissertation research was focused on (1) the effect of oxygen content on the structure of graphite oxide, (2) the stability of graphene oxide solution, (3) the application of graphene precipitate from graphene oxide solution as counter electrode for DSSCs, (4) the development of a novel synthesis method for the three-dimensional …

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Diffuse-Interface Field Approach To Modeling Self-Assembly Of Heterogeneous Colloidal Systems And Related Dipole-Dipole Interaction Phenomena, Tianle Cheng

Dissertations, Master's Theses and Master's Reports - Open

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Colloid self-assembly under external control is a new route to fabrication of advanced materials with novel microstructures and appealing functionalities. The kinetic processes of colloidal self-assembly have attracted great interests also because they are similar to many atomic level kinetic processes of materials. In the past decades, rapid technological progresses have been achieved on producing shape-anisotropic, patchy, core-shell structured particles and particles with electric/magnetic charges/dipoles, which greatly enriched the self-assembled structures. Multi-phase carrier liquids offer new route to controlling colloidal self-assembly. Therefore, heterogeneity is the essential characteristics of colloid system, while so far there still lacks a model that is …

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The Use Of Life-Cycle Analysis To Reduce The Environmental Impact Of Materials In Manufacturing, Megan A. Kreiger

Dissertations, Master's Theses and Master's Reports - Open

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This thesis is composed of three life-cycle analysis (LCA) studies of manufacturing to determine cumulative energy demand (CED) and greenhouse gas emissions (GHG). The methods proposed could reduce the environmental impact by reducing the CED in three manufacturing processes.

First, industrial symbiosis is proposed and a LCA is performed on both conventional 1 GW-scaled hydrogenated amorphous silicon (a-Si:H)-based single junction and a-Si:H/microcrystalline-Si:H tandem cell solar PV manufacturing plants and such plants coupled to silane recycling plants. Using a recycling process that results in a silane loss of only 17 versus 85 percent, this results in a CED savings of 81,700 …

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The Quantification Of The Fly Ash Adsorption Capacity For The Purpose Of Characterization And Use In Concrete, Zeyad Tareq Ahmed

Dissertations, Master's Theses and Master's Reports - Open

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Fly ash has been shown to be an effective replacement for portland cement in concrete mixtures. However, many fly ash materials contain unburned carbon from the combustion process. Unburned carbon in fly ash adsorbs air entraining admixtures (AEAs) reducing their effectiveness in providing a specified air void system in concrete materials. Measurement tools and methods for characterization of the adsorption properties of fly ash materials are necessary for beneficial use of fly ash materials in concrete. In this research, two methods were developed to measure and quantify the adsorption capacity AEAs on fly ash materials. The first method is the …

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Reaction Control In Quiescent Systems Of Free-Radical Retrograde-Precipitation Polymerization, Vijaya Raghavan Tirumala

Dissertations, Master's Theses and Master's Reports - Open

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Free-radical retrograde-precipitation polymerization, FRRPP in short, is a novel polymerization process discovered by Dr. Gerard Caneba in the late 1980s. The current study is aimed at gaining a better understanding of the reaction mechanism of the FRRPP and its thermodynamically-driven features that are predominant in controlling the chain reaction.

A previously developed mathematical model to represent free radical polymerization kinetics was used to simulate a classic bulk polymerization system from the literature. Unlike other existing models, such a sparse-matrix-based representation allows one to explicitly accommodate the chain length dependent kinetic parameters.

Extrapolating from the past results, mixing was experimentally shown …

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