Engineering Commons^™

Influence Of Temperature And Microstructural Modification On Formability Of Magnesium Alloys, Arun Mohan

Doctoral Dissertations

"The ß-precipitate free AZ31, ß-precipitate rich AZ91 and a few Mg-Y-Zn alloys were studied to understand the dependence of Mg formability on microstructural condition and temperature. Friction stir processing (FSP) was used to refine the grain size and to obtain desirable distribution of precipitates in the matrix. Since Mg alloys exhibit challenges in achieving room temperature formability, superplastic deformation was utilized. This work focused on high strain rate superplasticity (HSRS, ≥10⁻² s⁻¹) which is more attractive for industrial applications as compared to the slower rates of conventional superplasticity.

Thermally stable fine grains and pinning particles at HSRS temperatures were essential …

Stress Corrosion Cracking Behavior Of Friction Stir Processed Ultrafine Grained Light Metal Alloys, Gaurav Ramchandra Argade

Doctoral Dissertations

"The influence of friction stir processing (FSP), a microstructural modification tool, on the corrosion behavior of Al-Mg, Al-Mg-Sc, Mg-Al-Zn and Mg-Y-RE alloys has been studied. An attempt has been made to establish correlation between processing parameters and the subsequent microstructural evolution especially matrix grain size on the corrosion and stress corrosion properties of the alloys. A relationship between grain size and corrosion rate for Mg-Y-RE alloys was envisaged and power law type behavior was proposed. Ultrafine fine grained (UFG) microstructure showed one order magnitude lower corrosion rate.

Grain refinement achieved through different FSP parameters showed lower corrosion currents for Al-Mg …

Microstructure And Mechanical Properties Of Cold Drawn Steel Wires, Ning Liu

Theses: Doctorates and Masters

Cold drawn eutectoid steel wires have been widely used for a variety of applications, such as suspension bridges, steel cords for automobile tires, and springs. Much research has been done to increase their mechanical strength. With advances in modern production technology, both the drawing speed and the quality of drawn steels have been enhanced. After a careful literature survey, it is obvious that some issues are still controversial. As Y.S. Yang, J.G. Bae and C.G. Park mentioned, the lamellar spacing, thickness and volume fraction of cementites have all reached the nanometer regime, and the conventional theory is not enough to …

High Performance Magneto-Optic Garnet Materials For Integrated Optics And Photonics, Mohammad Alam

Theses: Doctorates and Masters

This work explores the preparation, characteristics and properties of highly bismuth (Bi) substituted, metal doped, iron garnet compounds and investigates their potential for various emerging applications in the visible and near infrared spectral regions.

Bi-substituted iron garnet and garnet-oxide nanocomposite films of generic composition type (Bi, Dy/Lu)3(Fe, Ga/Al)5O12 are prepared by using a radio frequency (RF) magnetron sputtering technique. The physical properties (crystallinity, film morphology, optical absorption spectra across the visible spectral range and the elemental composition of layers), and magneto-optic behaviour (Faraday rotation, hysteresis loops of Faraday rotation, and magnetic switching behaviour) of these sputtered garnet films are investigated …

Purification Of Metals Through Filtration And Electromagnetic Separation, Lucas Nana Wiredu Damoah

Doctoral Dissertations

"The applicability of a high frequency electromagnetic field to the removal of nonmetallic inclusions from silicon and aluminum, and the mechanism of depth mode filtration during aluminum purification were investigated. Electromagnetic separation experiments at frequencies of 63 - 120 kHz and aluminum filtration experiments using both conventional Al₂O₃ filters and AlF₃ coated Al₂O₃ filters were carried out by flowing molten aluminum through, and partly solidified in the filter bed followed by analysis of the metal and filter material. Materials were characterized with an optical microscope and macroscope, scanning electron microscope (SEM/EDX), x-ray diffraction (XRD), electron probe microanalysis (EPMA) and glow …

Thermal Properties Of Spinel Based Solid Solutions, Kelley R. Wilkerson

Doctoral Dissertations

"Solid solution formation in spinel based systems proved to be a viable approach to decreasing thermal conductivity. Samples with systematically varied additions of MgGa₂O₄ to MgAl₂O₄ were prepared and thermal diffusivity was measured using the laser ash technique. Additionally, heat capacity was measured using differential scanning calorimetry and modeled for the MgAl₂O₄-MgGa₂O₄ system. At 200⁰C thermal conductivity decreased 24% with a 5 mol% addition of MgGa₂O₄ to the system. The solid solution continued to decrease the thermal conductivity by 13% up to 1000⁰C with 5 mol% addition. The decrease in thermal conductivity ultimately resulted in a decrease in heat flux …

Densification And Thermal Properties Of Zirconium Diboride Based Ceramics, Matthew Joseph Thompson

Doctoral Dissertations

"The research presented in this dissertation focuses on the processing and thermomechanical properties of ZrB₂ based ceramics. The overall goal was to improve the understanding of thermal and mechanical properties based on processing conditions and additives to ZrB₂. To achieve this, the relationships between the thermal and mechanical properties were analyzed for ZrB₂ ceramics that were densified by different methods, varying amounts of carbon, B₄C, or TiB₂ additions. Four main areas were investigated in this dissertation. The first showed that decreased processing times, regardless of densification method, improved mechanical strength to >500 MPa. This study also revealed that lower oxygen …

Role Of Alloy Additions On Strengthening In 17-4 Ph Stainless Steel, Arpana S. Murthy

Doctoral Dissertations

"Alloy modifications by addition of niobium (Nb ), vanadium (V), nitrogen (N) and cobalt (Co) to cast 17-4 PH steel were investigated to determine the effect on mechanical properties. Additions of Nb, V, and N increased the yield strength from 1120 MPa to 1310 MPa while decreased the room temperature charpy V notch (CVN) toughness from 20 J to four Joules. The addition of Co to cast 17-4 PH steel enhanced the yield strength and CVN toughness from 1140 MPa to 1290 MPa and from 3.7 J to 5.5 J, respectively. In the base 17-4 PH steel, an increase in …

Hollow Hydroxyapatite Microspheres As Devices For Controlled Delivery Of Proteins And As Scaffolds For Tissue Engineering, Hailuo Fu

Doctoral Dissertations

"Hollow HA microspheres were prepared by converting Li₂O-CaO-B₂O₃ glass microspheres in a K₂HPO₄ solution. Process parameters, such as reaction temperature (25°C-60°C) and concentration of the phosphate solution (0.02-0.25 M) significantly influenced the microstructure of the hollow HA microspheres. Microspheres with the largest hollow core size were obtained at lower temperature or with low K₂HPO₄ concentration. In comparison, microspheres with high surface area (~140 m²/g) were obtained at higher K₂HPO₄ concentration (0.25 M). Upon heat treatment (up to 900°C), the surface area of the hollow HA microspheres decreased (from ~100 m²/g to ~2 m²/g), and the rupture strength increased (from ~11 …

Modeling And Synthesis Of Pvdf-Based Dielectrics For Energy Storage Applications, Xuhui Lu

Doctoral Dissertations

"The purpose of this research was to develop dielectric films for high energy density capacitor applications. Also desired was to develop a deeper understanding of dielectric breakdown and electric energy storage related phenomena through simulation, theoretical analysis, and experimental investigation.

An analytical model incorporating Weibull dielectric strength statistics was developed to establish quantitative relationships between material properties and device performance of self-healing capacitors. The model is useful for designing high voltage capacitors and developing dielectric materials where the effects of electric field-dependent permittivity need to be considered.

In the experimental work, solution-cast poly(vinylidene difluoride) (PVDF) homopolymer PVDF films with high …

Plastic Strain Accommodation And Acoustic Emission During Melting Of Embedded Indium Particles In Aluminum, Michael M. Kuba

Masters Theses

"Melting of micron-sized (0.2 to 3 µm diameter) indium particles embedded in an aluminum matrix was discovered to produce acoustic emission. Melting of embedded immiscible particles produces a pure dilation during the phase transformation and has no long-range diffusion field to control the speed of transformation. It was found that acoustic emission can no longer be considered as a criterion of displacive transformations and that melting of micron-sized embedded particles is strain energy controlled. Acoustic emission was confirmed to result from the rapid relaxation of aluminum around indium particles embedded on grain boundaries. Prismatic punching of dislocation loops is proposed …

The Effect Of Sulfur On Structure And Conversion Of Bioactive Borate Glasses, Ali Mohammadkhah

Masters Theses

"The effect of sulfur on glass structure and the conversion process of bioactive CaO-LI₂O-B₂O₃ glasses were studied. One glass without and two glasses with different amounts of sulfur were made using conventional melting and dry quenching techniques. These glasses reacted with a phosphate solution and converted to hydroxyapatite. Particles (150-355µm) were reacted in 0.25 and 0.5 molar K₂HPO₄ solutions at 37⁰C for 2 to 96 hours. The weight loss of the particles and the final pH of the solution were measured. The weight loss measurements indicated that the reaction rate increases with …

Process Simulation And Inclusion Characterization In Stainless Steel Ingot Casting, Jun Ge

Masters Theses

"For the ingot casting process, fluid flow of steel plays an important role in quality control and industrial operations. Using CFD software (FLUENT), this study overviews the fluid flow pattern in the bottom-teeming ingot filling process with three different swirl-modified upgate designs. Turbulent flow and mass transfer are considered main factors in controlling the process. The motion of the slag phase was also considered. In addition to the modeling studies, inclusions in stainless steel poured into ingots with a traditional and a swirl-modified upgate system were investigated using an optical microscope, SEM-EDS and ASPEX automated feature analysis technology. The main …

The Significance Of Equi-Biaxial Bubble Inflation In Determining Elastomeric Fatigue Properties, Stephen Jerrams, Niall Murphy, John Hanley

Books/Book Chapters

It is well documented that for the effective modelling of the static and dynamic behaviour of elastomeric components using the finite element (FE) method it is essential to obtain material parameters that are derived from a range of physical tests. For a conventional linear solid, uniaxial testing suffices to fully characterise the material, but for rubber it is necessary to test in at least two deformation modes. Also, the determination of fatigue lives of rubber components is still in its infancy and a reliable, repeatable fatigue test for rubber will have important consequences for component design, functionality, maintenance and cost. …

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

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 …

Effect Of Extracellular Matrix (Ecm) Protein Micropatterns On The Behavior Of Human Neuroblastoma Cells, Ishwari Poudel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Recent advances in patterning techniques and emerging surface microtechnologies have allowed cell micropatterning to control spatial location of the cells on a surface as well as cell shape, attachment area, and number of contacting neighbor cells. These parameters play important roles in cell cellular behaviors. Cell micropatterning has thus become one of the most important strategies for biomedical applications, such as, tissue engineering, diagnostic immunoassays, lab-on-chip devices, bio-sensing, etc., and cell biology studies as well. For neuronal cells, there have been attempts to distribute neuronal cells on specific patterns to control cell-to-cell interaction. However, there have been very limited understanding …

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 …

Highly Porous Silica Network Prepared From Sodium Metasilicate, R E. Essien, O A. Olaniyi, L A. Adams, R O. Shaibu

Journal of Metals, Materials and Minerals

Porous silica network was prepared from sodium metasilicate (Na2SiO3) at room temperature (27C) using hydrochloric acid (HCl) as catalyst through the sol-gel method. The gel was dried at 120C for 1 day and calcined at 800C for 3 hours and the material obtained characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed the formation of amorphous silica particles of average sizes 598 nm with ordered porous network of pore sizes ranging from 0.18-0.91 ?m. This synthetic route uses sodium metasilicate as commercial precursor without pore forming templates which could be useful …

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

Graduate 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 …

Fundamental Understanding Of Soot Induced Wear Mechanism Of Diesel Engines, Mihir Patel

Material Science and Engineering Dissertations - Archive

Emission of Oxides of nitrogen and particulates matters from diesel engines have been reduced by implementing exhaust gas recirculation (EGR) protocols but at the expense of increased wear of engine components. This problem is aggravated by Environment Protection Agency (EPA) regulation such as API CJ 4 and SAPS where chemical limits have been places on the amount of phosphorous, sulfur and sulfated ash in lubrication oil. Several studies have examined the role played by diesel soot on enhanced wear but none have provided comprehensive mechanism. This would allow the possibility to comprehend fundamental understanding of soot induced wear mechanism of …

Templated Synthesis And Characterizations Of High Moment Magnetic Nanoparticles For Bioapplications, Punnapob Punnakitikashem

Material Science and Engineering Dissertations - Archive

Magnetic nanoparticles have been widely used for biomedical applications such as drug and gene delivery, hyperthermia treatment of cancer, MRI contrast enhancement, cell labeling and magnetic separation. We present two new types of magnetic nanoparticles for bioapplications; granular superparamagnetic gold nanoparticles and multilayered nanodisks. Granular superparamagnetic gold nanoparticles consist of superparamagnetic islands embedded in a gold matrix. Multilayered nanodisks consist of two magnetic layers separated by a non-magnetic layer with two capping layers. Capping layers such as gold provide functionalization sites for biomolecule attachment. These nanoparticles possess two key magnetic requirements for bioapplications, a high saturation magnetic moment and a …

An Innovative Epitaxial Growth Method For Minimizing Dislocations In Thin-Film Quantum-Dot Optoelectronic And Photovoltaic Device Applications, Jateen Gandhi

Material Science and Engineering Dissertations - Archive

A new buffer layer method for epitaxial growth of lattice-mismatched semiconductor quantum-dots based p-i-n structures is presented. To our knowledge this is the first instance of a dislocation-reduction approach that has shown reduced dark current behavior in a quantumdot device compared to its counterpart homojunction p-n device consisted of the barrier material. The present work compared a lattice misfit strain build-up behavior between an In0.15Ga0.85As (p) / InAs (i) / In0.15Ga0.85As (n) (QD) device to an In0.15Ga0.85As (p) / In0.15Ga0.85As (n) (HOM) device, as both were grown on an un-doped gallium arsenide (GaAs) (100) substrate. The intrinsic region of QD …

Electrochemical N-Type Doping In Metal Oxides And Its Application In Photovoltaics, Xiaofei Han

Material Science and Engineering Dissertations - Archive

Electrodeposition has the advantages of low-cost, high-throughput and large-area processing which is particularly suitable for solar cells fabrication. Two common metal oxides prepared by electrodeposition are discussed here, ZnO and Cu2O. ZnO is largely used in the solar cells as the window and transparent contact material. Cu2O is potential absorption material for next generation solar cell. n-type doping of these metal oxides was revealed during electrochemical deposition. For naturally n-type ZnO, n-type doping is achieved by substituting the cation (Zn) with a group III element (Al, Ga and Y) and for naturally p-type Cu2O, n-type doping is realized by substituting …

Optical And Magnetic Properties Of Feni Slanted Columnar Thin Films Infiltrated With Pmma And Fe3O4 Nanoparticles, Dan Liang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, dielectric polymer and magnetic nanoparticles were utilized to hybridize FeNi Slanted columnar thin films (SCTFs). Firstly Fe₃O₄ in PMMA matrix was prepared by physical blending process. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to investigate the dispersion of the nanoparticles in PMMA matrix and the preparation conditions were varied to optimize the dispersion. The hybridized materials were prepared by the infiltration of PMMA and 5 wt% Fe₃O₄ nanoparticles/PMMA to the voids of FeNi SCTFs. Spin-coating and annealing process were employed to reach an excellent infiltration.

The structural …

Strength Of Polycrystalline Ceramics Under Shock Compression, Jianbin Zhu

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Determinations of Some polycrystalline ceramics’ strength properties and inelastic deformation mechanisms in the shocked state are critically important to the design and optimization of armor structures involving these materials. In this work, multiscale modeling and simulations have been carried out to study strength of the effects of polycrystalline microstructure, crystal anisotropy, porosity, and their interactions with microscopic deformation/damage mechanisms on the responses of several polycrystalline ceramics under shock compression and to extract their shock strengths from the wave profiles measured in the related plate impact shock wave experiments.

With a mesoscopic computational model, the roles of intragranular microplasticity and deformation …

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 …

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

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 speed data was …

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 …