Engineering Commons^™

Morphological Characterization Of Irradiated Ultra High Molecular Weight Polyethylene (Uhmwpe), Christopher Phillip Stephens

Doctoral Dissertations

Effects of radiation (gamma and proton) on Ultra High Molecular Weight Polyethylene (UHMWPE) is studied for prosthetic joints and for radiation shielding for manned space missions. The first section of the dissertation will cover gamma radiation effects on UHMWPE by means of solubility, hardness, three-phase model, crystallite thickness, and molecular mobility studies. The second part will cover proton radiation effects on UHMWPE by means of solubility, three-phase crystallite model, and crystallite thickness study. The combined studies of the gamma irradiated samples shows that chain scission occurs on the surface and crosslinking in the center. The combined studies of the proton …

Laser Machining Of Structural Ceramics: Computational And Experimental Analysis, Anoop Samant

Doctoral Dissertations

Outstanding mechanical and physical properties like high thermal resistance, high hardness and chemical stability have encouraged use of structural ceramics in several applications. The brittle and hard nature of these ceramics makes them difficult to machine using conventional techniques and damage caused to the surface while machining affects efficiency of components. Laser machining has recently emerged as a potential technique for attaining high material removal rates. Major focus of this work is to understand the material removal mechanisms during laser machining of structural ceramics such as alumina (Al₂O₃), silicon nitride (Si₃N₄), silicon …

A Study Of Helium Ion Induced Secondary Electron Production, Ranjan Ramachandra

Doctoral Dissertations

The scanning electron microscope (SEM) is a popular instrument used for imaging because of its high resolution images it can generate. However the new scanning helium ion scanning microscope (SHIM) can produce higher resolution and better contrast images than the conventional SEM. In both the microscopes secondary electron (SE) signal is the most widely used imaging mode because of their high yield efficiency and their high spatial resolution. In order to be able to properly evaluate the relative strengths and weaknesses of electron induced SE (eSE) and ion induced SE (iSE) imaging a detailed model able to quantify them is …

Development Of A Low Cost Handheld Microfluidic Phosphate Colorimeter For Water Quality Analysis, Sean C. Kaylor

Master's Theses

This thesis describes the design, fabrication, and testing process for a microfluidic phosphate colorimeter utilized for water quality analysis. The device can be powered by, and interfaced for data collection with, a common cell phone or laptop to dramatically reduce costs. Unlike commercially available colorimeters, this device does not require the user to measure or mix sample and reagent. A disposable poly(dimethylsiloxane) (PDMS) microfluid chip, powered by an absorption pumping mechanism, was used to draw water samples, mix the sample at a specific ratio with a molybdovanadate reagent, and load both fluids into an onboard cuvette for colorimetric analysis. A …

Short-Term Failure Analysis Of Aluminum Conducting Composite Core Transmission Lines, Brian Burks

Electronic Theses and Dissertations

Recently the inefficiency and lack of capabilities of electric energy transmission have been put in the global spotlight; a transmission line design known as the Aluminum Conducting Composite Core Trapezoidal Wire (ACCC/TW^TM) attempts to eliminate the deficiencies. The ACCC core is comprised of a new hybrid composite material. The most probable causes of short-term damage to the ACCC core were investigated through a series of finite element models. It was found that excessive bending was the most likely cause of short-term damage to the core. During bending of the ACCC core, stresses are concentrated at the interface in …

Morphology Of Ingaas Multilayer Nanostructure On Gaas High-Index Surfaces, Yanze Xie

Graduate Theses and Dissertations

This work aimed to explore nanostructure configuration by growing multiple layers of strained InGaAs on GaAs high index surface. The knowledge learned would help to achieve a comprehensive picture of strain-driven nanostructure evolution. Ordered arrays of InGaAs quantum dots were demonstrated on GaAs(311)B. The ordering patterns depended on the thickness of GaAs interlayer between InGaAs Quantum Dots (QDs). With an increased interfacial thickness, a transition from two dimensional (2D) lateral ordering to 1D dot chains was observed. InGaAs growth on GaAs(311)A and GaAs(331)A ended up with 1D quantum wires (QWRs). Straight InGaAs QWRs were uniformly distributed across the surfaces owing …

The Creation Of Micropatterns Through The Femtosecond Laser Ablation Of Diamond Materials, Matthew D. Parrish

Masters Theses

Laser systems that create nanometer and micrometer scale features on the surface of materials are important tools used by the scientific and industrial communities to develop novel applications and technology. The goal of the research presented in this thesis is to investigate the characteristics of a custom femtosecond micro and nano machining station that uses laser ablation to create features and to advance system capabilities. The improvements include programs that allow for a greater variety and complexity of features and patterns that are easily customized to specification. In this work, a titanium doped sapphire (Ti:S) laser oscillator and amplifier system …

High Permittivity And High Permeability Of Nanoparticles In Conducting Polymer Films, Matthew Wayne Fuller

Masters Theses

The purpose of this study is to synthesize a new material out of conducting polymers and magnetic nanoparticles that has high electric permittivity and high magnetic permeability. There is a strong desire in electronics for lighter, faster, cheaper and more bandwidth providing materials. There is also an interest with the military for materials that are light weight, have high electric permittivity and high magnetic permeability. A way to synthesize a material that meets those criteria is to use conducting polymers for their high permittivity properties and to disperse magnetic particles in the polymer for their high permeability properties. The synthesized …

Proton Irradiation Effects On Semiconductor Cdse/Zns Core/Shell Nanocrystals, Stephen Graham Charter

Graduate Theses and Dissertations

The absorbance and photoluminescence measurement of semiconductor CdSe/ZnS core shell nanocrystals were reviewed and investigated after they were exposed to proton irradiation. The CdSe/ZnS core shell nanocrystals of 3.2nm and 4.4nm were commercially purchased and investigated. These nanocrystals were embedded in UV resin. Proton irradiation of energy 2MeV was applied at doses from 3 x 1013 protons cm-2 to 1.47 x 1015 protons cm-2 for both nanocrystal sizes. Absorbance measurements were conducted at 300K. Results from absorbance measurements showed slight broadening of the first exciton peak of both samples but was most noticeable in the 3.2nm nanocrystal sample. UV resin …

Synthesis And Polymorphic Control For Visible Light Active Titania Nanoparticles, Sujaree Kaewgun

All Dissertations

Titania (TiO₂) is useful for many applications in photocatalysis, antimicrobials, pigment, deodorization, and decomposition of harmful organics and undesirable compounds in the air and waste water under UV irradiation. Among the three phases of TiO₂, Rutile, Anatase, and Brookite, studies have been more focused on the anatase and rutile phases.
Pure brookite is the most difficult phase to prepare, even under hydrothermal conditions. Predominantly brookite phase TiO₂ nanoparticles were prepared by the Water-based Ambient Condition Sol (WACS) process in our laboratory. The objectives of this research were to enhance visible light active (VLA) photocatalytic properties …

Colloidal Electroluminescence: Novel Routes To Controlled Emission Of Organic Light Emitting Diode Devices, Christopher Huebner

All Dissertations

In recent years the importance of the organic light emitting diode (OLED) has grown immensely, and the past two decades have seen ongoing and exhaustive research in organic routes to solid state lighting,
wherein electricity is directly converted into emitted light through an excited state relaxation mechanism. The benefits of incorporating polymeric and small molecule materials into solid state lighting devices include high efficiences, low production costs, amenability to large-scale production and devices, reduced environmental impact and low energy consumption. Herein are presented novel routes to materials engineering and preparation, device fabrication and emission tailoring through the abilility to form …

Electrodeposition Of Nanocrystalline Ni-Based Alloys, Hanseung Park

All Theses

Nanocrystalline materials can often process superior properties, but they are generally unstable against grain growth. Addition of a dopant can stabilize nanocrystalline alloys by decreasing the excess grain boundary energy as the thermodynamic driving force for grain growth and reducing grain boundary mobility via a kinetic effect of solute drag. In this thesis study, eight Ni-based alloys (Ni-W, Ni-P, Ni-Mo, Ni-Cu, Ni-B, Ni-Mg, Ni-Zn and Ni-Co) and pure Ni were made using an electrodeposition method. It is concluded that the use of different dopant can drastically affect the deposition mechanism as well as the morphology of resultant films. Ni-W and …

Surface Geometry Of C60 On Ag(111), H. I. Li, K. Pussi, K. J. Hanna, Lin-Lin Wang, Duane D. Johnson, H.-P. Cheng, H. Shin, S. Curtarolo, W. Moritz, J. A. Smerdon, R. Mcgrath, R. D. Diehl

Duane D. Johnson

The geometry of adsorbed C60 influences its collective properties. We report the first dynamical low-energy electron diffraction study to determine the geometry of a C60 monolayer, Ag(111)−(23√×23√)30°−C60, and related density functional theory calculations. The stable monolayer has C60 molecules in vacancies that result from the displacement of surface atoms. C60 bonds with hexagons down, with their mirror planes parallel to that of the substrate. The results indicate that vacancy structures are the rule rather than the exception for C60 monolayers on close-packed metal surfaces.

51st Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 51st annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Snowmass, Colorado, July 19-23, 2009.

Section Abstracts: Astronomy, Mathematics, And Physics & Materials Science

Virginia Journal of Science

Abstracts of the Astronomy, Mathematics and Physics & Materials Science Section for the 87th Annual Meeting of the Virginia Academy of Science, May 27-29, 2009, Virginia Commonwealth University, Richmond VA.

Design And Development Of Rapid Battery Exchange Systems For Electric Vehicles To Be Used As Efficient Student Transportation, Jonathan A. Bevier

Master's Theses

Rapid battery exchange systems were built for an electric van and pedal assist electric bike as a method of eliminating the need to recharge the vehicles batteries in order to increase the feasibility of using electric propulsion as a method of efficient student transportation. After selecting proper materials it was found that the systems would need a protective coating to ensure consistent operation. 1020 cold rolled steel samples coated with multiple thicknesses of vinyl resin paint, epoxy resin paint, and powder coating were subjected to environmental wear tests in order to determine if the type and thickness of common protective …

Compensation Of Loss And Stimulated Emission Of Surface Plasmon Polaritons, Guohua Zhu

Electrical & Computer Engineering Theses & Dissertations

Surface plasmon polaritons (SPPs) have become in recent years an important research topic because of their interesting, physics and exciting potential applications, ranging from sensing and biomedicine to nanoscopic imaging and information technology. However, many applications of surface plasmon polaritons are hindered by one common cause—absorption loss in metal.

Over the years, numerous proposals have been made on how to conquer the plasmon loss. In this dissertation, (1) the known solutions to the loss problem by adding optical gain have been reviewed; (2) the properties of surface plasmon polaritons are studied theoretically, and the solution of the controversy regarding the …

Surface Dynamics Of Silicon Low-Index Surfaces Studied By Reflection High-Energy Electron Diffraction, Ibrahim El-Kholy

Electrical & Computer Engineering Theses & Dissertations

Surface morphology during the growth of Si on Si(111)-(7x7) by femtosecond pulsed laser deposition (fsPLD) is studied using reflection high-energy electron diffraction (RHEED) at different temperatures. The growth of Si on Si(111) has received considerable attention as a model system of homoepitaxy. PLD is a deposition technique that uses much more energetic species (atoms and ions) compared to other physical vapor deposition (PVD), such as in molecular beam epitaxy. In this work, in situ reflection high energy electron diffraction (RHEED) was used to study the dynamics of PLD of Si on Si(111)-(7x7). Epitaxial growth of Si/Si(111)-(7x7) at temperatures as low …

Numerical/Experimental Investigation Of Plunge Stage And Effect Of Donor Material In Friction Stir Welding, Saptarshi Mandal

Mechanical & Aerospace Engineering Theses & Dissertations

Friction Stir Welding (FSW) was developed in 1991 as a robust solid-state joining technique that uses a specially shaped rotating tool to generate heat and plasticize material around the tool. The tool then mixes plasticized material along the joint line to produce the weld. Over the last decade, FSW has become increasingly popular for welding aluminum. The combination of attractive properties of the weld and cost-efficiency has led researchers to investigate the feasibility of using FSW for steel. One of the major impediments for using friction stir welding for harder materials such as steel is tool wear. It is well-documented …

Polarization Switching Kinetics Of Ferroelectric Nanomesas Of Vinylidene Fluoride-Trifluoroethylene Copolymer, R. V. Gaynutdinov, O. A. Lysova, S. G. Yudin, A. L. Tolstikhina, A. L. Kholkin, V. M. Fridkin, Stephen Ducharme

Stephen Ducharme Publications

The polarization switching kinetics of ferroelectric polymer nanomesas was investigated using piezoresponse force microscopy. The nanomesas were made by self-organization from Langmuir–Blodgett films of a 70% vinylidene fluoride and 30% trifluoroethylene copolymer. The polarization switching time exhibits an exponential dependence on reciprocal voltage that is consistent with nucleation-type switching dynamics.

Creep-Rupture Behavior Of Die-Cast Magnesium Alloys, Y B. Unigovski

Journal of Metals, Materials and Minerals

It is found that the relationship between the time-to-rupture tr and the time to the onset of tertiary creep tοt (tr /tot) in die-cast Mg-9Al alloy is equal to 1.3 and independent of stress, test temperature and diecasting parameters over the range examined. It is shown that the introduction of creep-rupture strain into Monkman-Grant relation modified by Dobeš and Milička demonstrates only the deviation range of the minimum creep rate from the average creep rate. The apparent activation energy Ec of creep is below the value of magnesium self-diffusion energy ESD up to 175o C. At higher temperatures, Ec > ESD, …

Method For The Preparation Of Secondary Emulsions Of Fish Oil In Water, S Siramard, L Dubas, S T. Dubas

Journal of Metals, Materials and Minerals

The method for the preparation of stable secondary emulsion has been detailed and discussed in terms of polymer capping and emulsion ratio. The dispersion of omega-3 oil in water by emulsion stabilized with casein was further coated with a polycationic polyelectrolyte, Poly (dially dimethyl ammonium chloride). The stability of the emulsion was studied by turbidity measurements using a UV-visible spectrophotometer. The particles size of the primary and secondary emulsion was investigated by light scattering and zeta potential measurements. Results shown in this article provide some details about the mechanism of the formation of secondary emulsion, mainly regarding the polymer/emulsion-mixing ratio.

Interfacial Polymerization Of Water-Soluble Polyaniline And Its Assembly Using The Layer-By-Layer Technique, E Detsri, S T. Dubas

Journal of Metals, Materials and Minerals

The interfacial polymerization of aniline has been used to prepare water-soluble polyaniline. Polyaniline was made water-soluble by interfacial polymerization in the presence of poly(styrene sulfonated, sodium salt) (PSS), which acted as bundling agent to provide water solubility. The prepared polymer composite was later used for the fabrication of polyaniline nano-thin films using the layer-by-layer (LbL) self-assembly technique. Film produced by the LbL technique can be used in electro-chromic films, sensors or electro-catalytic films depending on the type of architectures. This paper first presents, a brief review on conducting polymer prepared by interfacial polymerization. Special interest is given to the synthesis …

Mechanical Property Improvement Of Upe Resin From Glycolyzed Pet With Commercial Upe Resin, T Limpiti, P Potiyaraj

Journal of Metals, Materials and Minerals

The aim of this research paper is to improve mechanical properties of cured unsaturated polyester (UPE) resin prepared from glycolyzed PET by mixing with a commercial UPE resin. Postconsumer PET bottles were depolymerized by glycolysis reaction in excess propylene glycol at 190ºC in the presence of zinc acetate as a catalyst. The glycolyzed product was polyesterified with maleic anhydride and mixed with styrene monomer in order to obtain UPE resin. The prepared UPE resin was mixed with a commercially available general purpose grade UPE resin at various ratios. The mixed resins were cured using methyl ethyl ketone peroxide and cobalt …

Characterizations Of Fibers Produced From Polypropylene/Silica Composite, N Srisawat, M Nithitanakul, K Srikulkit

Journal of Metals, Materials and Minerals

Fumed silica particles filled polypropylene (PP) filament fibers were prepared by melt spin pilot plant. First, virgin PP and silicas(hydrophilic and hydrophobic) were premixed using twin screw extruder to prepare silica containing PP composite resin. Then, the resin composite was again mixed with virgin PP and spun into filaments with various filler loadings in the range of 0.5 - 2.5 wt%. The characterizations of spun composite fibers including crystallization temperature (DSC analysis), polymer orientation (sonic modulus) and the fine structure (XRD) were studied. XRD results showed β-form crystallinity peak in x-ray pattern of fiber drawn with low take-up speed (300 …

Effect Of Discarded Ppvc Contents On Thermal And Ultraviolet Resistance Of Acrylonitrile Butadiene Rubber, S Patcharaphun, S Chuypun

Journal of Metals, Materials and Minerals

In this investigation, the discarded plasticized-polyvinyl chloride (pPVC) from the extrusion of weather-seal was added into acrylonitrile butadiene rubber (NBR). Subsequently, the effects of pPVC contents on the mechanical properties, thermal, ultraviolet and swelling resistances of NBR were studied. The results indicated that scorch and cure time, tensile strength, hardness and swelling resistance increased with the increasing amount of pPVC added. Considering the thermal and ultraviolet resistances, it was observed that the mechanical properties of unfilled NBR decreased due to the desulphurization of the sulphur crosslinks and chain scission during heat and ultraviolet aging. However, the mechanical properties of the …

Thermoplastic Cassava Starch/Sorbitol-Modified Montmorillonite Nanocomposites Blended With Low Density Polyethylene: Properties And Biodegradability Study, S Chuayjuljit, S Hosililak, A Athisart

Journal of Metals, Materials and Minerals

The objective of this research paper is to prepare environmentally friendly plastic materials from biodegradable cassava starch, montmorillonite (MMT) and low density polyethylene (LDPE). MMT was first modified by sorbitol via a solid state method. Results from X-ray diffraction (XRD) indicated that sorbitol molecules were intercalated in between MMT layers along 001 direction. Cassava starch was plasticized with sorbitol and formamide on a two-roll mill to obtain thermoplastic starch (TPS). The TPS/modified-MMT nanocomposites were prepared by means of melt blending of TPS with various amounts of MMT (0, 2, 4, and 6 phr). XRD and transmission electron microscopy (TEM) results …

Physical Properties Of Polyolefin/Bamboo Charcoal Composites, S Kittinaovarat, W Suthamnoi

Journal of Metals, Materials and Minerals

The physical properties of two kinds of polyolefin / bamboo charcoal composites, based upon polypropylene (PP) and low density polyethylene (LDPE), were studied for varying levels of charcoal inclusion between 0 and 20 phr. A Brabender mixer and two-roll mill were used for the mixing process of both polyolefin and bamboo charcoal composites, followed by compression moulding of the homogeneous mixtures to form the composite materials. The tensile strength and Young's modulus were both found to increase, whilst the elongation at break decreased, in a dose-dependent manner with increasing bamboo charcoal content in the composite materials. The tensile strength of …

Effect Of Electron Donor On Pe Polymerization, A Thongdonjui, W Trakarnpruk, R H. Strauss

Journal of Metals, Materials and Minerals

Ziegler-Natta catalyst was prepared from colloidal MgCl2 (from reaction between magnesium ethyl carbonate and aluminium sesquichloride, Al2Et3Cl3) followed by contact with TiCl4. Al/Mg and Ti/Mg molar ratios were studied as parameters affecting the catalyst synthesis. Catalytic performance and effect of electron donor on ethylene polymerization were investigated. Results showed that addition of electron donor (ethyl benzoate) increased activity balance when polymerizations were performed under hydrogen pressure of 1 bar and 3 bars. The morphology of the polymer can be improved while fine content of the polymer was reduced by addition of dicyclopentyl dimethoxysilane. A productivity of 17.3 and 15.0 kg …

Determination Of Yield Behaviour Of Boron Alloy Steel At High Temperature, J Tungtrongpairoj, V Uthaisangsuk, W Bleck

Journal of Metals, Materials and Minerals

The hot tensile test is a basic material testing method for investigation of the mechanical properties of steel at high temperature conditions. In industrial hot sheet forming processes such as hot stamping and hot gas metal forming, the influences of temperature and strain rate on microstructure and material behaviour play a significant role. In this work, sheet samples of steel grade 22MnB5 were examined using a hot deformation simulator. Different temperatures between 900 and 1200°C, which are above Ac3, and strain rates between 0.001 and 0.1 s-1 were considered. During the tensile test, a laser speckle extensometer (LSE) was deployed …