Materials Science and Engineering Commons^™

Simulation Of Infiltrating Rate Driven By Surface Tension-Viscosity Of Liquid Elements From The Titanium Group Into A Packed Bed, Arturo Medina

Open Access Theses & Dissertations

The simulation of infusion of molten reactive metals (e.g., yttrium) into a porous, carbide packed bed to create carbide and boride composites was studied at ultrahigh temperatures (>1700°C). The infusion was investigated through a computational fluid dynamic (CFD) system of capillary pores and compared to a predicted analytical calculation formulated by Selmak and Rhines. Simulations of two-phase flow penetration of yttrium into a packed bed of B4C were investigated and compared with titanium, zirconium, hafnium, and samarium liquids. The non-reactive, liquid metal infusion was primarily driven by the surface tension and viscosity. The liquid metal depth and rate of …

Design And Analysis Of A Novel Latch System Implementing Fiber-Reinforced Composite Materials, Francisco Guevara

Open Access Theses & Dissertations

The use of fiber-reinforced composite materials have increased in the last four decades in high technology applications due to their exceptional mechanical properties and low weight. In the automotive industry carbon fiber have become popular exclusively in luxury cars because of its high cost. However, Carbon-glass hybrid composites offer an effective alternative to designers to implement fiber-reinforced composites into several conventional applications without a considerable price increase maintaining most of their mechanical properties. A door latch system is a complex mechanism that is under high loading conditions during car accidents such as side impacts and rollovers. Therefore, the Department of …

Sustainable Disposal Of Coal Processing Waste Streams, Mohammad Rezaee

Theses and Dissertations--Mining Engineering

Modern coal preparation facilities incorporate a wide array of solid-solid and solid-liquid separation processes for rejecting mineral matter to meet market specifications. The coarse mineral matter is typically placed into engineered refuse piles whereas the fine refuse is either stored in impoundments or co-disposed with the coarse refuse. The discharge water from the refuse material represents an environmental concern due to the potential release of trace elements, and the subsequent elevation of total dissolved solids and conductivity. The research findings reported in this dissertation addresses sustainable coal processing waste disposal through using strategies aimed at minimizing the environmental impacts. To …

Containment Materials For Thin-Strip Casting Of Steel, Abhishek Kumar

Doctoral Dissertations

"The focus of this research was to investigate the corrosion behavior of BN-based and ZrO₂-C refractories by molten steel. These refractories are used as side-dam and core-nozzle in the thin-strip casting of steel. The improvement and development of these refractory components will increase the process efficiency by prolonging the refractory service life.

The first part of this study focused on interaction of BN-ZrO₂-SiC side-dams with steel-inclusion system in a laboratory setup under argon gas environment. It was observed that corrosion of this ceramic was severe in contact with steel compared to slag/inclusion.

The second part of …

Inclusion Engineering In Mn-Si De-Oxidized Steel For Thin-Strip Casting, Vivek Thapliyal

Doctoral Dissertations

"The focus of this research was to understand inclusion formation and evolution in Mn-Si de-oxidized steels used in thin-strip casting. Inclusions formation and evolution in ultra-low carbon low-alloyed steels were studied. Inclusion engineering can be used to remove or modify detrimental inclusions, which cause casting issues.

The first part of this study focused on inclusion formation as a result of ferro-alloy addition. De-oxidation reaction in steels are the primary source of the typical oxide inclusion formed in steel. For Mn-Si de-oxidized steels ferro-silicon and ferro-manganese are the two ferro-alloys used for de-oxidation. Inclusion formation and evolution during the early stages …

Characterization Of Investment Shell Thermal Properties, Mingzhi Xu

Doctoral Dissertations

Thermal properties of investment casting shells have a great influence on the solidification of metal and thus control the properties of the cast product. Computational simulation requires accurate thermal properties to better represent the real process. Due to the porosity and meta-stable materials used in the investment shells, it is difficult to determine the real time thermal properties as a function of components and thermal processing history. Previous studies measured the thermal properties using a variety of methods, but very few results can be directly used in simulations due to lack of accuracy.

This research developed a new methodology that …

Resistance Switching Of Electrodeposited Cuprous Oxide, Sanaz Yazdanparast

Doctoral Dissertations

In this work, the resistance switching behavior of electrodeposited cuprous oxide (Cu₂O) thin films in Au/Cu₂O/top electrode (Pt, Au-Pd, Al) cells was studied. After an initial FORMING process, the fabricated cells show reversible switching between a low resistance state (16.6 Ω) and a high resistance state (0.4 x 10⁶ Ω). Changing the resistance states in cuprous oxide films depends on the magnitude of the applied voltage which corresponds to unipolar resistance switching behavior of this material. The endurance and retention tests indicate a potential application of the fabricated cells for nonvolatile resistance switching random access …

Metallurgical Optimization Of High Strength Cast Steels With Stage I Tempering, Terrell Owen Webb Jr.

Doctoral Dissertations

“Eglin steel was developed by the U.S. Air Force and Ellwood National Forge Company as a cost-effective, ultrahigh strength steel for use in armament, aerospace, and commercial applications. Eglin steel has been successfully substituted for high alloy steels, such as AF1410 and HP-9-4-20/30, to produce the casing for “bunker buster” bombs where penetration of concrete barriers and rock at high velocity ( > 1000 ft/sec) is desired. Unlike AF1410 and HP-9-4-20/30, Eglin steel is low nickel (nominal 1 wt.%) and contains no cobalt. Given the successful performance of Eglin steel in the casings applications, the Department of Defense has directed that …

Dissolution Of Borate Glasses And Precipitation Of Phosphate Compounds, Jaime Lynn George

Doctoral Dissertations

"Borate glasses have been developed for biomedical applications such as scaffolds for soft tissue and bone repair. The dissolution processes of borate glasses in phosphate-containing aqueous solutions were studied by µ-Raman spectroscopy which provided information about the types and concentrations of borate species released into the solution as a function of time and characterized the formation of calcium phosphate reaction products on the glass surface. Boric acid molecules (H₃BO₃) and borate anions (B(OH)₄^-) can be detected in solution and their relative concentrations depend on the solution pH.

Static and dynamic single-pass flow-through experiments …

Synthesis And Fabrication Of Graphene/Conducting Polymer/Metal Oxide Nanocomposite Materials For Supercapacitor Applications, Mohamad Khawaja

USF Tampa Graduate Theses and Dissertations

The rising energy consumption worldwide is leading to significant increases in energy production with fossil fuels being the major energy source. The negative environmental impact of fossil fuel use and its finite nature requires the use of alternative sources of energy. Solar energy is a clean alternative energy source; however, its intermittent nature is a major impediment that needs to be reduced or eliminated by the development of cost effective energy storage. Thermal storage in tanks filled typically with molten salt at elevated temperatures is widely used in concentrating solar power plants to generate electricity during periods of low daytime …

Studies Related To Microbially Induced Corrosion Of Stainless Steel 304 And 316, Somil Gupta

Electronic Theses and Dissertations

Pitting corrosion of stainless steel (SS) is observed in many different industries including the dairy industry. It is of concern, because it weakens the steel, and can cause cracking. Any replacement or repair of SS equipment is very costly and also causes delays in product manufacture. Microbial Induced Corrosion (MIC) is a possible accelerator of natural corrosion seen in galvanized steel pipes. Studies have shown a correlation between surface roughness and the ability of bacteria to colonize and form biofilms. Dairy industry utilizes higher food grade SS 304 and 316. However, even these relatively corrosion resistant stainless steel grades may …

Assessing Coupled Mechanical Behavior And Environmental Degradation At Submicron Scales, Samantha K Lawrence

Open Access Dissertations

Mechanical and electromechanical properties, deformation and fracture mechanisms, and environmental resistance of materials at submicron scales have been investigated through the combination of nanomechanical testing, high resolution microscopy, diffraction, and electrochemical testing. Nanomechanical techniques were used to isolate environmental, orientation, and size effects. Material evaluation focuses on metals, both model and engineering alloys, in bulk and thin-film form as well as oxide-substrate systems. Yield behavior of Ni 200, a model material, depends on sampled volume size, orientation, and surface preparation. Exposure to high-pressure hydrogen gas is also found to impact incipient plasticity and mechanical properties of commercially pure Ni 201. …

Kesterite Thin-Film Solar Cell Absorbers Derived Using Inhomogeneous Czts Nanoparticles, Wei-Chang D. Yang

Open Access Dissertations

My doctoral research focuses on understanding the structure-property-processing relationship of the kesterite materials to improve their device performance. It is recognized in both my own work and the recent literature that the structural and compositional integrities of CZTSSe are crucial to derive the solar cell grade kesterite thin-films. Analytical electron microscopy (AEM) allows me to demonstrate the structural and compositional inhomogeneity of the CZTS nanoparticles and CZTSSe thin-films at the nanoscale. For example, the observed forbidden reflections in TED patterns and FFT diffractograms corresponding to HRTEM images indicate that cation disorder leads to stacking faults in CZTS nanoparticles. Probe-corrected STEM …

Characterization And Mechanical Properties Of Solar Grade Silicon In Granular And Nanopowder Form, Mohamad Bilal Zbib

Open Access Dissertations

Polycrystalline silicon is mainly used for solar cell applications, structures in micro-electromechanical systems, and production of single crystal Si. One of the relatively new methods for producing large quantities of polysilicon is fluidized bed reactor (FBR), where two main morphologies are produced, granular solid (1-3 mm) and nanopowders (30-300 nm). Grinding and fracture occurs in the granular solid during shipping and handling which can affect the final product properties and create safety issues. The microstructure and the morphology of both the granular and the nanopowder forms of Si were examined using scanning and transmission electron microscopes (SEM and TEM). The …

Determination Of Current Density Distribution In An Electron Beam, Yudhishthir Prasad Kandel

Legacy Theses & Dissertations (2009 - 2024)

Electron beams are useful in many applications because they can be focused down to a spot far exceeding the physical limit of focusing visible light or x-rays. Additionally, electron beams are useful in transferring concentrated amounts of energy to a very small well defined region of a target for a fixed duration. This has led to the development of both scanning electron microscopes (SEMs) and electron beam lithography. The goal of this work was to develop a general method that accurately and easily yields the best estimate of the electron current density distribution of a focused electron beam, known as …

Study Of Millisecond Laser Annealing On Ion Implanted Soi And Application To Scaled Finfet Technology, Tyler J. Michalak

Legacy Theses & Dissertations (2009 - 2024)

The fabrication of metal-oxide-semiconductor field effect transistors (MOSFET) requires the engineering of low resistance, low leakage, and extremely precise p-n junctions. The introduction of finFET technology has introduced new challenges for traditional ion implantation and annealing techniques in junction design as the fin widths continue to decrease for improved short channel control. This work investigates the use of millisecond scanning laser annealing in the formation of n-type source/drain junctions in next generation MOSFET.

Optical Metrology For Directed Self-Assembly Patterning Using Mueller Matrix Spectroscopic Ellipsometry Based Scatterometry, Dhairya J. Dixit

Legacy Theses & Dissertations (2009 - 2024)

The semiconductor industry continues to drive patterning solutions that enable devices with higher memory storage capacity, faster computing performance, lower cost per transistors, and higher transistor density. These developments in the field of semiconductor manufacturing along with the overall minimization of the size of transistors require cutting-edge metrology tools for characterization.

Implementation Of Strategies To Improve The Reliability Of Iii-Nitride Photodetectors Towards The Realization Of Visible And Solar-Blind Imaging Arrays, John Bulmer

Legacy Theses & Dissertations (2009 - 2024)

Ultraviolet (UV) radiation detectors are being heavily researched for applications in non-line-of-sight (NLOS) communication systems, flame monitoring, biological detection, and astronomical studies. These applications are currently being met by the use of Si-based photomultiplier tubes (PMTs), which are bulky, fragile, expensive and require the use of external filters to achieve true visible-blind and solar-blind operation.

Initiated Chemical Vapor Deposition (Icvd) Polymer Thin Films : Structure-Property Effects On Thermal Degradation And Adhesion, Vijay Jain Bharamaiah Jeevendrakumar

Legacy Theses & Dissertations (2009 - 2024)

Opportunities and challenges for chemical vapor deposition (CVD) of polymer thin films stems from their applications in electronics, sensors, and adhesives with demands for control over film composition, conformity and stability. Initiated chemical vapor deposition (iCVD) is a subset of the CVD technique that conjoins bulk free-radical polymerization chemistry with gas-phase processing. The novelty of iCVD technique stems from the use of an initiator that can be activated at low energies (150 – 300 °C) to react with surface adsorbed monomer to form a polymer film. This reduces risk for potential unwarranted side-reactions.

Ion Implantation In Zno : Defect Interaction And Impurity Diffusion, Faisal Yaqoob

Legacy Theses & Dissertations (2009 - 2024)

In the first part of this research we studied the entropy changes in diffusion prefactor and its