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Theses/Dissertations

Materials Science and Engineering

2011

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Full-Text Articles in Engineering

Development Of X-Ray Holography Methods For Structure Determination : Application Of High Speed Detectors And Novel Numerical Methods, Yuhao Wang Dec 2011

Development Of X-Ray Holography Methods For Structure Determination : Application Of High Speed Detectors And Novel Numerical Methods, Yuhao Wang

Dissertations

Holographic methods show much promise to enable direct determination of atomic structure with minimal assumptions and approximations. The approach can, in principle, provide three dimensional information on atomic positions. However, significant developments in experimental techniques, instrumentation and in data collection and analysis are needed. A review of the holography method is given with a focus on X-ray fluorescence holography. Methods for analysis of X-ray holographic data are also reviewed. An overview of the detectors relevant to X-ray measurements is also presented. An experimental apparatus for rapid acquisition of X-ray holographs using novel X-ray detectors has been developed. The integration of ...


Hydrogen Storage In Pt/Carbon Nanotube Sheets, An-Yu Ma Dec 2011

Hydrogen Storage In Pt/Carbon Nanotube Sheets, An-Yu Ma

Theses

Three types of self-assembled carbon nanotube (CNT) sheets, for example, carboxylic functionalized multi-walled CNTs (MWNTs-COOH), pure multi-walled CNTs (MWNTs), and pure single-walled CNTs (SWNTs), were prepared as substrates by ambient environment vacuum filtration of suspensions of the nanotubes. To enhance hydrogen storage on the CNTs, platinum particles were deposited on the three types of CNT sheets using two processes: electrodeposition (ED) using a DC power source and electrochemical deposition under cyclic voltammetry (CV). To verify platinum deposition on the surface of the CNT sheets, a Scanning Electron Microscope (SEM) was used to obtain images, and Energy Dispersive X-ray (EDX) spectroscopy ...


Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin Dec 2011

Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin

Publicly Accessible Penn Dissertations

This thesis describes a series of experiments to both determine the origins of charge transport and enhanced photoconduction in metal nanoparticle arrays linked with zinc-porphyrin complexes, but to also determine the nucleation and growth mechanisms related to Ferroelectric Nanolithography (FNL) as a platform for hybrid devices. The development of test structures on glass substrates was undertaken to not only allow the study of the mechanisms controlling charge transport but the photoconduction of zinc-porphyrin linked gold nanoparticle (AuNP) arrays. In this study, the dominate charge transport mechanism was determined to be thermally assisted tunneling and the origins of enhanced photoconduction in ...


A Framework For Studying The Physical Degradation Characteristics Of Dvds And Their Relationship To Digital Errors, Brian K. Saville Dec 2011

A Framework For Studying The Physical Degradation Characteristics Of Dvds And Their Relationship To Digital Errors, Brian K. Saville

Theses and Dissertations

The methods used to store data on DVD-R discs have been proven to work over the last 15 years. However, there has been a growing concern that these discs will be outlasted by the paper records they were meant to replace. The data on a DVD-R is stored as optical contrasts which have the potential to be misread and even damaged. This damage may occur either on the surface or internally to the disc, especially on the recording layer itself. The literature is saturated with studies attempting to determine the time period in which discs may fail and what the ...


Nanoscale Metal Thin Film Dewetting Via Nanosecond Laser Melting: Understanding Instabilities And Materials Transport In Patterned Thin Films, Yueying Wu Dec 2011

Nanoscale Metal Thin Film Dewetting Via Nanosecond Laser Melting: Understanding Instabilities And Materials Transport In Patterned Thin Films, Yueying Wu

Doctoral Dissertations

Nanoscale metal thin film dewetting via laser treatment is studied in this dissertation. The purpose is to understand: 1) the spatial and temporal nature of intrinsic instabilities; and 2) mass transportation involved in dewetting pattern evolution in metal thin films as well as in lithographically patterned nanostructures; and finally 3) to explore advanced control of metallic nanostructure fabrication via the confluence of top down nanolithography and pulsed laser induced dewetting. This study includes three sections. In first section, thin film Cu-Ni alloys ranging from 2-8nm were synthesized and laser irradiated. The evolution of the spinodal dewetting process is investigated as ...


Computational And Experimental Study Of Structure-Property Relationships In Nial Precipitate-Strengthened Ferritic Superalloys, Shenyan Huang Dec 2011

Computational And Experimental Study Of Structure-Property Relationships In Nial Precipitate-Strengthened Ferritic Superalloys, Shenyan Huang

Doctoral Dissertations

Ferritic superalloys strengthened by coherent ordered NiAl B2-type precipitates are promising candidates for ultra-supercritical steam-turbine applications, due to their superior resistance to creep, coarsening, oxidation, and steam corrosion as compared to Cr ferritic steels at high temperatures. Combined computational and experimental tools have been employed to investigate the interrelationships among the composition, microstructure, and mechanical behavior, and provide insight into deformation micromechanisms at elevated temperatures.

Self and impurity diffusivities in a body-centered-cubic (bcc) iron are calculated using first-principles methods. Calculated self and impurity diffusivities compare favorably with experimental measurements in both ferromagnetic and paramagnetic states of bcc Fe. The calculated ...


Processing, Microstructures, And Properties Of Aluminide-Strengthened Ferritic Steels, Zhenke Teng Dec 2011

Processing, Microstructures, And Properties Of Aluminide-Strengthened Ferritic Steels, Zhenke Teng

Doctoral Dissertations

NiAl-strengthened ferritic steel is a material of interest for steam turbine applications due to their promising creep resistance, high thermal conductivity, low cost and thermal expansion coefficient. However, there are two critical issues restricting their applications: low room temperature ductility and limited creep resistance at temperatures higher than 600°C. The reasons for these behaviors have not been fully understood, especially the processing-microstructure-property relationship has not been clearly identified.

The alloys were designed, fabricated, and processed, according to the required microstructures and properties. The matrix and precipitates can be thoroughly characterized by a combination of techniques, including atom probe tomography ...


Shear-Band Formation And Thermal Activation In Metallic Glasses, Lu Wang Dec 2011

Shear-Band Formation And Thermal Activation In Metallic Glasses, Lu Wang

Doctoral Dissertations

Metallic glasses (MGs) usually have high strength, high hardness and high elastic strain limit. However, the deformation mode and mechanism in metallic glasses are radically different from those in conventional crystalline materials with a long-range ordered structure. For crystalline materials, the intrinsic relationship between their mechanical properties and crystal structures has been well described by dislocation theory. In contrast, for amorphous materials, theories on the structures and controlling factors of localized shear-band formation are far from being complete.

In this thesis, shear-banding behavior of MGs under nanoindentation was first reviewed. The hardness of MGs was found to be independent on ...


Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead Dec 2011

Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead

Theses and Dissertations

Nano-engineered-textures on a material surface can dramatically improve the wetting and non-wetting properties of a surface, and they also show promise to address friction issues that affect surfaces in contact. In this work, aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) was used to produce nano-textures on copper (Cu) substrates. A study was performed to examine the effects of changing the annealing conditions and a-Si thickness on nano-texture formation. The creation of various nano-topographies and chemically modifying them using octafluorocyclobutane (C4F8) was performed to control hydrophilicity, hydrophobicity, and oil affinity of nano-textured surfaces. A video-based contact angle measurement system was used ...


Effect Of Selected Phase Change Materials Concentration And Manufacturing Process On The Properties Of Plaster Mixture Systems, Rong Cui Dec 2011

Effect Of Selected Phase Change Materials Concentration And Manufacturing Process On The Properties Of Plaster Mixture Systems, Rong Cui

All Theses

Phase change materials (PCM) are generally used in building construction materials for their ability to absorb and release large amounts of energy when their phase change happens at their specific melting temperature. This results in a significant increase in thermal mass of the building, a reduction in temperature fluctuations and therefore a reduction in heating and cooling loads. However, in order to properly select a PCM and optimize its integration in a specific building, the properties of building construction materials enhanced with PCM must be known. This research focuses on studying the effects of the concentration of a micro-encapsulated PCM ...


Micromechanical Studies Of Intergranular Strain And Lattice Misorientation Fields And Comparisons To Advanced Diffraction Measurements, Lili Zheng Dec 2011

Micromechanical Studies Of Intergranular Strain And Lattice Misorientation Fields And Comparisons To Advanced Diffraction Measurements, Lili Zheng

Doctoral Dissertations

Inhomogeneous deformation fields arising from the grain-grain interactions in polycrystalline materials have been evaluated using a crystal plasticity finite element method and extensively compared to neutron diffraction measurements under fatigue crack growth conditions. The roles of intergranular deformation anisotropy, grain boundary damage, and non-common deformation mechanisms (such as twinning for hexagonal close packed crystals) are systematically evaluated. The lattice misorientation field can be used to determine the intragranular deformation behavior in polycrystals or to describe the deformation inhomogeneity due to dislocation plasticity in single crystals. The study of indentation-induced lattice misorientation fields in single crystals sheds lights on the understanding ...


Modeling And Control Of A Flexible Ionic Polymer Metal Composite(Ipmc) Actuator For Underwater Propulsion, Shivakanth Gutta Dec 2011

Modeling And Control Of A Flexible Ionic Polymer Metal Composite(Ipmc) Actuator For Underwater Propulsion, Shivakanth Gutta

UNLV Theses, Dissertations, Professional Papers, and Capstones

The goal of this research is to model and control the underwater vehicle propelled by IPMC actuator. IPMC consists of an ionic membrane sandwiched between two metallic electrodes. When an external voltage is applied, IPMC undergoes large deformation due to transport of ions. Due to its ability to work in aqueous environments, it can be used for developing small scale underwater vehicles.

First, Finite element approach is used to describe the dynamics of the both single and segmented IPMC actuator. In the approach presented, each element is attached with a local coordinate system that undergoes rigid body motion along with ...


Printing Carbon Nanotube Based Supercapacitors For Packaging, Alexandra Hartman Dec 2011

Printing Carbon Nanotube Based Supercapacitors For Packaging, Alexandra Hartman

All Theses

Living in a world full of portable electronics, there is great need for energy storage devices. Currently, limitations for storage involve power inefficiencies as well as bulkiness. This is why printable charge storage devices that display good electrochemical performance are needed. It is for this reason that research into the production and packaging of carbon nanotube based super capacitors was carried out.
A super capacitor can be built by using high surface area multi-walled carbon nanotubes suspended in an ionic liquid. The two active electrodes are made from a combination of the multi-walled carbon nanotubes and an ionic liquid, ground ...


Empirical Study: Failure Of Glass-To-Metal Seals During Shock Loading, William Horton Dec 2011

Empirical Study: Failure Of Glass-To-Metal Seals During Shock Loading, William Horton

All Theses

The goal of this thesis was to determine the empirical failure mechanisms and sequence of cartridge actuated devices (CADs) experiencing failure of the glass-to-metal (G/M) seal. Impact loading was conducted with a drop weight machine at room temperature and 300¡F, and then empirically analyzed with high speed video. Resulting peak overload force, shear stress, and impulse were all calculated. The room temperature samples were found to absorb twice the impulse upon failure as the elevated temperature G/M seals. Closed-form and three-dimensional finite element analysis was used to determine the stress state and deformation upon loading. Furthermore, high ...


Highly Conductive Carbon Nanotube Fibers For Biomedical Applications, Vijoya Sa Dec 2011

Highly Conductive Carbon Nanotube Fibers For Biomedical Applications, Vijoya Sa

All Dissertations

We developed a wet spinning process for the formation of polymeric fibers with high loading of single walled carbon nanotubes. The dissertation consists of five chapters. In the first chapter, the research goals were formulated and the art and technologies of fiber spinning from carbon nanotubes were critically analyzed. The next three chapters report the original results. Last chapter summarizes all the findings.
In the second chapter, we describe a surfactant based method of stabilization of carbon nanotube dispersions. The conditions of stability of nanotube dispersions in aqueous solutions of sodium dodecyl sulfate were analyzed. Using surface tension isotherms, the ...


Influence Of Aging And Severe Plastic Deformation On The Shape Memory Behavior Of Ti-50.6at%Ni, William Shirley Dec 2011

Influence Of Aging And Severe Plastic Deformation On The Shape Memory Behavior Of Ti-50.6at%Ni, William Shirley

All Theses

Martensitic phase transformations were investigated for Ti -50.6 at % Ni processed via severe plastic deformation (SPD) and subsequent aging for temperatures between 400 and 550C and times ranging from 1hr to 100hrs. Phase transformations of the SPD material were compared to material processed via solution treated at 800C and 850C for 1hr. Transformations were investigated with differential scanning calorimetry (DSC) and confirmed by X-ray diffraction (XRD) with optical microscopy being used to determine grain size. Solution treated samples displayed a single (1-1) B2↔B19' transformation prior to and upon initial aging, i.e. 400C/1h, 450C/1/10h. Intermediate ...


Role Of Surface Coatings In Lithium-Ion Batteries, Archana Kayyar Dec 2011

Role Of Surface Coatings In Lithium-Ion Batteries, Archana Kayyar

All Theses

Rechargeable batteries that can charge and discharge at high rates have applications in hybrid and plug-in hybrid vehicles and they provide energy storages for wind energy. Various methods like reducing particle size, aliovalent doping and carbon coating have been researched in order to attain higher charge and discharge rates in rechargeable Li-ion batteries. In this work, the electrode materials were coated with amorphous films in an attempt to improve the rate capability of the batteries.
A study by Kang and Ceder suggested that a Li4P2O7-like 'fast-ion conducting surface phase' could form on the surface ...


The Development Of A Far Red To Near Infrared Fluorescent Probe For Use In Optical Imaging, Margaret Fiedler Dec 2011

The Development Of A Far Red To Near Infrared Fluorescent Probe For Use In Optical Imaging, Margaret Fiedler

All Theses

New techniques for biological optical imaging are of great interest for the detection and visualization of processes and disease in both clinical and research areas. One major advancement has been the use of far red and near infrared (NIR) light, as it has the ability to penetrate tissues deeper than other parts of the spectrum which are readily scatter and absorbed by the surroundings. In order to improve the signal to noise ratio and resolution of optical images, contrast agents are used. Fluorescent markers can be modified to attach to specific molecular targets, creating small molecular probes. These targets can ...


Novel Oxadiazole Containing Monomers For Polymeric Light Emitting Devices, Alexandra Foguth Dec 2011

Novel Oxadiazole Containing Monomers For Polymeric Light Emitting Devices, Alexandra Foguth

All Theses

Organic light emitting diodes (OLED) have received a great deal of
attention in the research community in the past few decades. This
work focuses on OLEDs utilizing the donor-acceptor operational
approach. In specific a single layer device architecture with an
emissive layer of copolymerized hole and electron transport moieties
in an effort to frustrate phase segregation that can occur during
device operation. A new methacryalate based oxadiazole monomer,
4-[5-(biphenly-4-yl)- 1,3,4-oxadiazol-2-yl] phenyl methacrylate (mPBD) an electron transporter, was successfully synthesized. The new monomer was copolymerized with N-vinylcarbazole (VK), a hole transporter, to form statistical copolymers. The glass ...


Modeling Of A Novel Solar Down Beam Test Facility Utilizing Newtonian Optics, Ryan J. Hoffmann Dec 2011

Modeling Of A Novel Solar Down Beam Test Facility Utilizing Newtonian Optics, Ryan J. Hoffmann

UNLV Theses, Dissertations, Professional Papers, and Capstones

As advances in concentrated solar energy progress there will inevitably be an increase in the demand of resources for testing new conceptions. Currently, there are limited facilities available for taking concentrated solar energy concepts from the laboratory bench scale to the engineering test scale. A proposed solution is a scientific and developmental facility that provides highly concentrated solar energy at ground level. The design presented is a solar down beam test facility utilizing a Newtonian optics approach with a flat rectangular down beam mirror to reflect and concentrate the sun's rays at ground level.

Literature review suggests a hyperbolic ...


Spectral Engineering Of Optical Fiber Through Active Nanoparticle Doping, Tiffany Lindstrom-James Dec 2011

Spectral Engineering Of Optical Fiber Through Active Nanoparticle Doping, Tiffany Lindstrom-James

All Dissertations

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions.
Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result ...


Direct Contact Pyrolysis Of Hydrocarbons: A Source Of Hydrogen And Interesting Carbon Formations, Peter G. Faught Dec 2011

Direct Contact Pyrolysis Of Hydrocarbons: A Source Of Hydrogen And Interesting Carbon Formations, Peter G. Faught

UNLV Theses, Dissertations, Professional Papers, and Capstones

The work detailed in this document looks at a novel liquid metal supported catalytic system for the generation of hydrogen by decomposition of ethanol through direct contact pyrolysis. The hydrogen is produced at relatively low temperatures (500-600°C) and has carbon and water as co-products. It should be noted that CO is not observed as a product at these low temperatures. This is to be contrasted with the hydrogen produced at higher temperature from ethanol which does contain carbon monoxide. The presence of carbon monoxide in hydrogen complicates fuel cell operation and catalytic chemical processes. Thus, the lack of CO ...


Failure Analysis Of Leaking Stainless Steel Pump Casing, Mary E. Parker Dec 2011

Failure Analysis Of Leaking Stainless Steel Pump Casing, Mary E. Parker

Chancellor’s Honors Program Projects

No abstract provided.


A Conceptual Framework And Simulation Modeling Of Engineering Change Management In A Collaborative Environment, Krishna Rao Reddi Dec 2011

A Conceptual Framework And Simulation Modeling Of Engineering Change Management In A Collaborative Environment, Krishna Rao Reddi

Mechanical and Aerospace Engineering - Dissertations

Engineering Change Management (ECM) in a collaborative environment is a complex process and is crucial to the Original Equipment Manufacturer (OEM) to ensure low product development time and cost. In this thesis, the ECM in a collaborative environment has been studied and a conceptual framework to support the process is presented. New Product Development (NPD) and ECM processes have been modeled and simulated to study the associated process dynamics.

An extensive review of the literature indicated that the research on ECM in a collaborative environment is very limited. The review also highlighted that, (i) the ECM frameworks from past research ...


Effects Of Grain Boundary Character On Dynamic Recrystallization Using A Modified Monte Carlo Method, Michael B. Morse Dec 2011

Effects Of Grain Boundary Character On Dynamic Recrystallization Using A Modified Monte Carlo Method, Michael B. Morse

Boise State University Theses and Dissertations

Dynamic recrystallization (DRX) is the recrystallization that occurs during high temperature deformation of metals and alloys. While DRX has been observed experimentally, the parameters that affect the microstructure are still being explored. For example, the effects of temperature, strain rate, and initial grain size have already been studied, yet the effect of initial special boundary fraction is still unknown. Special boundaries are high-angle, low-energy grain boundaries. It is believed that higher initial fractions of special boundaries will lead to a delay in the onset of recrystallization and a higher peak stress.

Experimentation has shown that triple junctions are preferred nucleation ...


Spark Plasma Sintering Of Tungsten And Tungsten-Ceria: Microstructures And Kinetics, Jeffrey Bryce Perkins Dec 2011

Spark Plasma Sintering Of Tungsten And Tungsten-Ceria: Microstructures And Kinetics, Jeffrey Bryce Perkins

Boise State University Theses and Dissertations

Tungsten casting is impractical, and tungsten compacts are most often produced by press-and-sinter or by hot pressing. The temperatures typically required to sinter tungsten above 90% dense are above 1800 ºC, and sintering times are typically hours. Alternatively, spark plasma sintering (SPS) can be used to consolidate materials to high densities at lower temperatures and shorter times than traditional sintering techniques. In this study, pure tungsten and tungsten with 1, 4, 10, 15, and 20 weight percent ceria were spark plasma sintered at varying pressures, temperatures, and times to investigate the microstructures and the kinetics of sintering.

Densification of tungsten ...


Gesn Devices For Short-Wave Infrared Optoelectronics, Benjamin Ryan Conley Dec 2011

Gesn Devices For Short-Wave Infrared Optoelectronics, Benjamin Ryan Conley

Theses and Dissertations

The electronics industry has a large silicon infrastructure for the manufacture of complementary-metal oxide semiconductor (CMOS) based electronics. The increasing density of Si based circuits has set a pace that is now pushing the physical limits of connectivity between devices over conventional wire based links. This has driven the increasing interest in Si based optoelectronics and to use the groundwork already established by the electronics industry for lower cost optical communications. The greatest limitation to this effort has been the incorporation of a Si based laser, which requires integration of a direct bandgap material within this CMOS process.

The Ge1-xSnx ...


Degradation Of Polystyrene Foam Under Radiant Heat Flux, James Butler Dec 2011

Degradation Of Polystyrene Foam Under Radiant Heat Flux, James Butler

Theses and Dissertations

As the demand for liquefied natural gas has increased, safety concerns about the performance of transport vessels under fire conditions have been raised. Current codes for the sizing of the pressure relief systems require that the vessels are able to withstand an emmissive heat flux of 108kW/m2 and do not take into account the effects of insulation loss due to thermal decomposition of the insulation materials. To address this possible oversight in the current code models were presented to a working group organized by the Society of International Gas Tanker and Terminal Operators Ltd. focusing on the decomposition rate ...


Synthesis Of Zinc Oxide Nanorods And Use In Biosensor Applications, Anishkumar Manoharan Dec 2011

Synthesis Of Zinc Oxide Nanorods And Use In Biosensor Applications, Anishkumar Manoharan

Theses and Dissertations

The main aim of this research was to develop a nanorod based biosensor for biomedical applications. In this project I use zinc oxide nanorods as the bio-material for biosensor. I fabricated these nanorods using a solution-based technique. Initially I coated a zinc oxide seed layer as the base. This seed layer was then annealed at 350 degrees for almost 1 hour. As a next step, interdigitated electrodes were fabricated on the top of the seed layer using a lift off process. The zinc oxide nanorods were then grown at 90 degrees for almost 4 hours along the electrodes. In this ...


Fabrication Of Horizontal Silicon Nanowires Using A Thin Aluminum Film As A Catalyst, Khaja Hafeezuddin Mohammed Dec 2011

Fabrication Of Horizontal Silicon Nanowires Using A Thin Aluminum Film As A Catalyst, Khaja Hafeezuddin Mohammed

Theses and Dissertations

Silicon nanowires have been the topic of research in recent years for their significant attention from the electronics industry to grow even smaller electronic devices. The semiconductor industry is built on silicon. Silicon nanowires can be the building blocks for future nanoelectronic devices. Various techniques have also been reported in fabricating the silicon nanowires. But most of the techniques reported, grow vertical silicon nanowires. In the semiconductor industry, integrated circuits are designed and fabricated in a horizontal architecture i.e. the device layout is flat compared to the substrate. When vertical silicon nanowires are introduced in the semiconductor industry, a ...