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Articles 181 - 210 of 246

Full-Text Articles in Materials Science and Engineering

Prediction Of The Wear & Evolution Of Cutting Tools In A Carbide / Ti-6al-4v Machining Tribosystem By Volumetric Tool Wear Characterization & Modeling, Mathew Kuttolamadom Aug 2012

Prediction Of The Wear & Evolution Of Cutting Tools In A Carbide / Ti-6al-4v Machining Tribosystem By Volumetric Tool Wear Characterization & Modeling, Mathew Kuttolamadom

All Dissertations

The objective of this research work is to create a comprehensive microstructural wear mechanism-based predictive model of tool wear in the tungsten carbide / Ti-6Al-4V machining tribosystem, and to develop a new topology characterization method for worn cutting tools in order to validate the model predictions. This is accomplished by blending first principle wear mechanism models using a weighting scheme derived from scanning electron microscopy (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis of tools worn under different operational conditions. In addition, the topology of worn tools is characterized through scanning by white light interferometry (WLI), and then application …

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Surface Characterization Of Nephila Clavipes Dragline Silk, Benoit Faugas May 2012

Surface Characterization Of Nephila Clavipes Dragline Silk, Benoit Faugas

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To design synthetic fibers for extreme applications, many research groups are trying to identify how the structure of natural fibers (such as spider silk) leads to desirable properties such as high tensile strength.
Spider silk is a biological fiber having mechanical properties that exceed those of the best man made fibers in terms of high tensile strength and large extensibility, this combination providing the silk with a large work of rupture. While the bulk structure, composition and properties have been intensively studied elsewhere, this study focuses on elucidating the Nephila clavipes spider dragline silk surface structure and composition, as well …

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Characterization And Optimization Of Solution-Derived Chalcogenide Glass Thin Films, Jacklyn Wilkinson May 2012

Characterization And Optimization Of Solution-Derived Chalcogenide Glass Thin Films, Jacklyn Wilkinson

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Chalcogenide glasses have many unique properties that allow them to be used in a variety of optical applications. Infrared transparency allows them to be used in sensors for molecules that have 'fingerprints' in the 2-25 μm range. By producing amorphous thin films of these materials, they can be incorporated into chemical sensors as planar waveguides and resonators. The goal of this work was to fabricate and characterize solution-derived chalcogenide thin films for use in chemical sensors with a source wavelength between 3-3.5 μm.
The structural and optical properties of the parent bulk glass were characterized and used as reference for …

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Nanoparticles In Solution-Derived Chalcogenide Glass Films, Spencer Novak May 2012

Nanoparticles In Solution-Derived Chalcogenide Glass Films, Spencer Novak

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The results in this thesis are from our efforts to modify the optical properties of solution-derived chalcogenide glass films by the incorporation of nanomaterials. First, the composition Ge23Sb7S70 was selected as the appropriate glass matrix for testing because solution-derived films of this composition have been well-studied in our group. Additionally, this composition was found to be less sensitive to certain processing parameters than As2S3, another well-studied, candidate chalcogenide glass composition, making Ge23Sb7S70 more suitable for the addition of nanomaterials. Optimization of film process parameters was performed to obtain high-quality films appropriate for doping with nanomaterials. This consisted of determining the …

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Grain Boundaries Structures And Wetting In Doped Silicon, Nickel And Copper, Kaveh Meshinchi Asl May 2012

Grain Boundaries Structures And Wetting In Doped Silicon, Nickel And Copper, Kaveh Meshinchi Asl

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This thesis reports a series of fundamental investigations of grain boundary wetting, adsorption and structural (phases) transitions in doped Ni, Cu and Si with technological relevance to liquid metal embrittlement, liquid metal corrosion and device applications. First, intrinsically ductile metals are prone to catastrophic failure when exposed to certain liquid metals, but the atomic level mechanism for this effect is not fully understood. A nickel sample infused with bismuth atoms was characterized and a bilayer interfacial phase that is the underlying cause of embrittlement was observed. In a second related study, we showed that addition of minor impurities can significantly …

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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

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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 speed data was …

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

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

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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 …

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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

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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 …

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

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

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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 transition of the copolymers …

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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

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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 aging conditions, 450C/100h; 500C/1/10/100h; and …

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

Printing Carbon Nanotube Based Supercapacitors For Packaging, Alexandra Hartman

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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 …

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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

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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 …

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

Highly Conductive Carbon Nanotube Fibers For Biomedical Applications, Vijoya Sa

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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 …

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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

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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 of …

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Stress Relaxation Of Glass Using A Parallel Plate Viscometer, Guy-Marie Vallet Aug 2011

Stress Relaxation Of Glass Using A Parallel Plate Viscometer, Guy-Marie Vallet

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Currently, grinding and polishing is the traditional method for manufacturing optical glass lenses. However, for a few years now, precision glass molding has gained importance for its flexibility in manufacturing aspheric lenses. With this new method, glass viscoelasticity and more specifically stress relaxation are important phenomena in the glass transition region to control the molding process and to predict the final lens shape.
The goal of this research is to extract stress relaxation parameters in shear of Pyrex¨ glass by using a Parallel Plate Viscometer (PPV). The PPV machine was originally created to measure the viscosity of glass solid cylinders …

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Substrate Topography Design And Fabrication For Osteoblast And Dental Pulp Stem Cells Studies, Gloria Chen Aug 2011

Substrate Topography Design And Fabrication For Osteoblast And Dental Pulp Stem Cells Studies, Gloria Chen

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Research for cell guidance based tissue engineering has rapidly grown due to the increasing interest in tissue engineering and reconstructive medicine applications, such as cranial reconstruction. Many research teams have begun the process of identifying what factors influence cell behavior (including cell growth, proliferation, alignment and spreading). Published studies have pointed to the influence of the cell medial pH, substrate stiffness, chemistry and topography. Conclusive results are often hard to identify since researchers often vary many of these factors simultaneously and it is hard to decouple individual factor influence. These reports also points out that the cellular response can be …

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Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy Aug 2011

Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy

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Nano-scale composites are being investigated by academic, industrial, and national laboratories for potential applications such as wear resistant coatings and high strength foils. These structures are of interest due to their as-fabricated mechanical properties, such as high strength for nanolaminates. However, there have only been limited studies of the long-term mechanical stability. A greater understanding of how these systems might respond to sustained use is needed before these systems transition from research laboratories into widespread application. It is the objective of this thesis to clarify the link between accelerated aging using elevated temperatures over time and mechanical properties of two …

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Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate Aug 2011

Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate

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Thermoelectric materials are involved in the direct conversion between thermal and electrical energy. They may be used to generate power from a thermal gradient or to pump heat in or out of a system when driven with DC power. Much of the recent advances in thermoelectric research have been in materials whose thermoelectric efficiency has been optimized at temperatures above room temperature where power generation is the main application.
The question that I seek to answer in this dissertation is to use our standard experimental techniques in order to assess the possibility of a class of transition metal dichalcogenides bases …

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Influence Of Material Selection And Fabrication Process Repeatability On Mechanical Properties Of Glass-Polymer Matrix Composite Structures, Charles Edwards May 2011

Influence Of Material Selection And Fabrication Process Repeatability On Mechanical Properties Of Glass-Polymer Matrix Composite Structures, Charles Edwards

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This study has aimed to evaluate property uniformity from data obtained utilizing one design of a single layup composite plaque, three sources of glass fibers and a single, industry accepted resin to produce a repeatable fabrication process. This thesis has investigated the following:
1. Whether the type of glass (E-Glass, S-Glass, and R-Glass) influences the property values of individually tested samples compared between glass types.
2. Whether the type of glass influences the property uniformity throughout the set of tested samples.
3. Whether the composite plaque design and resulting performance, as defined by ASTM Standards or industry accepted parameters, is …

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Integrating Phase Change Materials In Building Materials: Experimentation, Characterization And Numerical Simulation, Esvar Subramanian May 2011

Integrating Phase Change Materials In Building Materials: Experimentation, Characterization And Numerical Simulation, Esvar Subramanian

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Phase Change Materials (PCM) have many commercial applications, including in buildings to reduce cooling and heating loads. However, the lack of research has prevented their use as a common building material. This research is part of a larger project that aims at developing a set of practical design guidelines for integrating PCM in buildings. A review of and classification of common PCM available on the market is provided. The thesis then focuses on the experimental characterization of the thermo-physical properties of PCM-integrated building materials and the development of a numerical model for the thermal analysis of buildings with PCM. Different …

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Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy Dec 2010

Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy

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Zirconia is one of the extensively studied solid oxide ceramics with respect to its use in various industrial applications like electrolyte in fuel cells, sensors, refractories and exhaust chamber in automobile industry. It can be found from the literature 1-4 that are contradictory results on the mechanical properties when alumina is added. There are several factors like microstructure, phase composition and method of processing that affects the mechanical properties of the material. The focus of this research is to examine how hardness, tensile strength and other properties varies with alumina content and deduce the optimal amount of alumina that is …

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Utilizing Copper(I) Catalyzed Azide-Alkyne Huisgen 1,3-Dipolar Cycloaddition For The Surface Modification Of Colloidal Particles With Electroactive And Emissive Moieties, Parul Rungta Dec 2010

Utilizing Copper(I) Catalyzed Azide-Alkyne Huisgen 1,3-Dipolar Cycloaddition For The Surface Modification Of Colloidal Particles With Electroactive And Emissive Moieties, Parul Rungta

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The development of charge–transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build “better” colloidally–based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the …

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Production And Characterization Of Aramid Copolymer Fibers For Use In Cut Protection, Jeffrey Moreland Dec 2010

Production And Characterization Of Aramid Copolymer Fibers For Use In Cut Protection, Jeffrey Moreland

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High-performance fibers such as para-aramids are used extensively in gloves for cut protection. However, the inherent cut resistance of these fibers and the relationship between cut resistance and other material properties is not known. To better understand cut resistance at the material level, an experiment was conducted using a lab-scale wet spinning system to produce and characterize aramid copolymer fibers.
To facilitate the use of lab-scale equipment, the experiment was conducted as a four-factor split-plot response surface design. The four treatment factors studied were solvent concentration in the coagulation bath, the amount of salt in the coagulation bath, the degree …

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Microstructure Modification Of Cu0.2ag2.8sbsete2 Through, Sloan Lindsey Aug 2010

Microstructure Modification Of Cu0.2ag2.8sbsete2 Through, Sloan Lindsey

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Cu0.2Ag2.8SbSeTe2 is new potential thermoelectric compound that exhibits very low thermal conductivity and a region of glass-like thermal conductivity. The compound phase segregates into AgSbTe2 and Ag2Te phases with Se and Cu acting as isoelectronic dopants. Backscatter SEM imaging is used to study the resulting microstructure. Normally cast samples exhibit cracks forming near the interfaces of the two phases. In this work we show that the cracks are caused by a low temperature monoclinic to cubic phase transition that occurs in the Ag2Te phase. We demonstrate that through rapid quenching we can control the size and shape of the phase …

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Fabrication Of Fluorescent Nanoparticle-Polymer Composites For Photoactive-Based Materials, Brett Ellerbrock Aug 2010

Fabrication Of Fluorescent Nanoparticle-Polymer Composites For Photoactive-Based Materials, Brett Ellerbrock

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Nanocomposites of nanoparticles dispersed throughout a polymer matrix have been studied to great length to improve the overall polymer properties. These enhancements are observed in the thermal, physical, and/or optical characteristics. Being able to harness nanoparticles in such a way may help improve fiber technology into the 21st century.
This work was geared toward synthesizing rare earth doped lanthanum fluoride (LaF3) nanoparticles because good separation in the absorption and emission bands of the material and it fluoresces in the visible to near-infrared range. Terbium ions were added to a LaF3 crystal because of their distinct visible green …

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Surface Characterization And Electrochemical Behavior Of Colloidal Particles, Cinta Pepin Aug 2010

Surface Characterization And Electrochemical Behavior Of Colloidal Particles, Cinta Pepin

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There is an ongoing interest in research focused on developing polymeric organic-light-emitting-devices (OLED) to replace inorganic devices. Compared to inorganic devices, OLEDs could present better properties such as higher efficiency, lower cost and simpler device fabrication. In an attempt to get a device with high efficiency, the hole transporting group and the electron transporting group were combined into a polymer to make an individual 'particle device'. The idea was to create a polymer particle containing both charge transporting moieties via emulsion polymerization. In this presentation, different techniques will be described that were used to determine the stability and the surface …

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Influence Of Iso-Structural Substitutions On Properties Of Ge(As,Sb)(S,Se) Glasses, Guillaume Guery Aug 2010

Influence Of Iso-Structural Substitutions On Properties Of Ge(As,Sb)(S,Se) Glasses, Guillaume Guery

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Chalcogenide glasses possess exceptional infrared transparency, large non-linear refractive indexes and low phonon energies, making them good candidates for infrared optical applications. Previous studies in the Ge-Sb-S glass system have shown an increase in the nonlinear refractive index with an iso-structural substitution of two- coordinated selenium (Se) for sulphur (S) and variation of other physical properties with substitution of other iso-structural species such as three-coordinated arsenic (As) for antimony (Sb). The role of such iso-structural exchange on properties important to the thermo-, visco- and mechanical attributes of glasses in the Ge-As/Sb-S/Se system has not been thoroughly evaluated and form the …

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Biodegradable Polymer Blends And Composites From Proteins Produced By Animal Co-Product Industry, Bernice Nzioki May 2010

Biodegradable Polymer Blends And Composites From Proteins Produced By Animal Co-Product Industry, Bernice Nzioki

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ABSTRACT
Development of new green materials from by-products of animal rendering industries would provide a substantial economic return to animal rendering processors. Meat and bone meal (MBM), one of the products of the rendering industry, has potential for numerous bio-based applications. This research focuses on fabrication of plastics blends made of MBM (Meat and bone meal) and UHMWPE (ultra high molecular weight polyethylene). We investigated thermal, morphological, water absorption and mechanical properties of the plastics. The plastics were compression molded and their properties were examined.
DSC thermographs of the blends indicated that the thermal properties of UHMWPE did not change …

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Grain Boundary Premelting And Activated Sintering In Binary Refractory Alloys, Xiaomeng Shi May 2010

Grain Boundary Premelting And Activated Sintering In Binary Refractory Alloys, Xiaomeng Shi

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Quasi-liquid intergranular film (IGF) which has been widely observed in ceramic systems can persist into sub-solidus region whereby an analogy to Grain boundary (GB) premelting can be made.
In this work, a grain boundary (GB) premelting/prewetting model in a metallic system was firstly built based on the Benedictus' model and computational thermodynamics, predicting that GB disordering can start at 60-85% of the bulk solidus temperatures in selected systems. This model quantitatively explains the long-standing mystery of subsolidus activated sintering in W-Pd, W-Ni, W-Co, W-Fe and W-Cu, and it has broad applications for understanding GB-controlled transport kinetics and physical properties. Furthermore, …

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Kinetic And Finite Element Modeling For Firing Brick, Daniel Mckinney May 2010

Kinetic And Finite Element Modeling For Firing Brick, Daniel Mckinney

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Kinetic modeling and simulation were used to optimize the firing cycle for brick. This was done to develop a tool for the brick industry to reduce fuel consumption and emissions during firing. A kinetic model was built using shrinkage data from dilatometer measurements and mass loss data from thermogravimetry measurements in order to predict the density as a function of temperature and time. The density of brick was related to the absorption coefficient (C/B), an ASTM standard which is related to the durability of the brick. The kinetic model was used to optimize the firing curve using a rate controlled …

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