Materials Science and Engineering Commons^™

Fiberglass Goes Green: Developing Phosphate Glass For Use In Biodegradable Composites, Christina Lee Arendt

Open Access Theses & Dissertations

Composite materials, such as the glass fiber reinforced polyester thermosets known as "fiberglass," are used in many applications. However, recycling processes for these materials are inefficient and not widely available. Specially engineered degradable polymers offer an opportunity to redesign these composites. Additionally, the composite could be tailored to be multi-use, such that upon degradation, the resulting products could be used as part of a zeoponic substrate (artificial soil) for growing plants. Such a material would be beneficial for long-duration space missions, terraforming, or in other agricultural applications.

The research presented in this Dissertation focuses on developing phosphate glass for use …

Yttria Rich Tbcs As Candidates For Cmas Resistant Top Coats, Juan Jose Gomez

Open Access Theses & Dissertations

State of the art thermal barrier coatings (TBC) commonly made of 7-8 wt. % yttria stabilized zirconia (7YSZ) are used in modern gas turbines to generate a thermal protection to the underlying super alloy components. TBCs allow higher operating temperatures for hot gas path components, thus, generating higher engine efficiency. The infiltration of molten glassy mineral deposits composed of CaO-MgO-Al2O3-SiO2 (CMAS) represents one of the major threats in reducing performance and service life in aero and land based gas turbine engines. The CMAS deposits are ingested into the engine carried commonly in sand, runways debris, fly ash and volcanic ash. …

Synthesis, Device Fabrication, And Characterization Of Two-Dimensional Molybdenum Disulfide, Gustavo Alberto Lara Saenz

Open Access Theses & Dissertations

The miniaturization of electronic devices according to Moore's Law has been propelled by the continuous demand for faster and smaller devices which continue to advance technology. One recent contribution to this trend was the isolation and characterization of one atom thick of graphite, known as graphene, which led to the Nobel Prize in physics in 2010 being awarded to Andre Geim and Konstantin Novoselov. Graphene and its related nanocarbon derivatives have exceptional mechanical, thermal, optical and electronic properties, making them a potential candidate for electronics and optoelectronics applications. However, this material has no intrinsic bandgap and complicated processes are required …

Improving The Engineering Properties Of Pla For 3d Printing And Beyond, Carmen R. Rocha

Open Access Theses & Dissertations

Additive manufacturing (AM), now more commonly known as 3D printing, has been classified as efficient, fast, and practical in the prototyping sector of product development. In the work presented here, we will use one of the AM techniques known as Material extrusion 3D printing (ME3DP), which has all the advantages of AM. However, one of the biggest challenges facing ME3DP technologies is the limitation of the range of materials used by this technique. Acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) are currently the most common thermoplastics materials used in ME3DP because of their ability to melt and be reprocessed. …

Damage Tolerance And Assessment Of Unidirectional Carbon Fiber Composites, Mark David Flores

Open Access Theses & Dissertations

Composites are beginning to be used in a variety of different applications throughout industry. However, certification and damage tolerance is a growing concern in many aerospace and marine applications. Although compression-after-impact have been studied thoroughly, determining a damage tolerance methodology that accurately characterizes the failure of composites has not been established. An experimental investigation was performed to study the effect of stacking sequence, low-velocity impact response, and residual strength due to compression and fatigue. Digital Image Correlation (DIC) captured the strains and deformation of the plate due to compression. Computational investigations integrated non-destructive techniques (C-Scan, X-Ray) to determine the extent …

Wettability Of Magnesium Based Alloys, Victor Manuel Ornelas

Open Access Theses & Dissertations

The premise of this project was to determine the wettability behavior of Mg-based alloys using three different liquids. Contact angle measurements were carried out along with utilizing the Zisman method for obtaining values for the critical surface tension. Adhesion energy values were also found through the use of the Young-Dupre equation. This project utilized the Mg-based alloy Mg-2Zn-2Gd with supplemented α-Minimum Essential Medium (MEM), Phosphate Buffer Saline solution (PBS), and distilled water. These three liquids are commonly used in cell cultivation and protein adsorption studies. Supplemented α-MEM consisted of α-MEM, fetal bovine serum, and penicillin-streptomycin. Mg-2Zn-2Gd was used because of …

Molecular Dynamics Proxy Applications For Optimizing Performance Of Simulations Under Extreme Conditions, Jayalath Abeywardhana Mudiyanselage Madawa Abeywardhana

Open Access Theses & Dissertations

Exascale performance of scientific application is a prominent goal for the scientific community and computer hardware vendors. As a result, several proxy applications for the widely used scientific codes have been developed with the purpose of testing performance, memory and power consumption issues associated with simulations at the exascale. Co-MD is a proxy application for classical Molecular Dynamics (MD) codes based on the (SPaSM) Los Alamos code.

This work comprises two different but related computational aspects: performance evaluation and optimization of Co-MD (Co-Design Molecular Dynamics) for different computer architectures/execution models, and direct application of SPaSM (Scalable Parallel Short-range Molecular Dynamics) …

Effects Of Fabrication Conditions On Mechanical Properties Of Ti-6al-4v Fabricated By Powder Bed Fusion Additive Manufacturing, Paola Azani

Open Access Theses & Dissertations

At the writing of this Thesis, additive manufacturing (AM) also known as 3D printing, has been popularized for its diversity in applications ranging from home and personal use, medical, industrial, consumer products, aerospace, architecture, automotive, military, fashion, food, art and more. Industries taking advantage of the design freedom and complexity offered by AM have exploded the growth of the technologies. Specifically, technologies that process metals using electron and laser beams have been recognized by the aerospace industry as a promising avenue for re-engineered components leading to reduced weight and improved engineering efficiencies for components like engine brackets and nozzles. However, …

Characterization In 2d Sulfides And Graphene Composites For Sensing Applications, Alberto Delgado

Open Access Theses & Dissertations

In this work, we have evaluated 2D layered material composites for opto-electro-mechanical sensing applications. In particular, we have focused on TMDCs and graphite and studied the effects of chemical liquid exfoliation on the structural characteristics of the 2D layered materials, through particle size, x-ray diffraction, Raman and surface area analysis. An approach was developed to combine the solution-processed dispersion with organic and inorganic matrix materials for forming the composites. From Raman Spectroscopy of the ultra-sonicated samples, the I2D/IG>2 for graphite, and for MoS2 the difference between the A1g and E2g peak was 22.85cm-1, consistent with few layer 2D MoS2. …

Mechanically Activated Combustion Synthesis Of Molybdenum Borosilicides For Ultrahigh-Temperature Structural Applications, Alan Alberto Esparza Hernandez

Open Access Theses & Dissertations

The desire to improve the efficiency of power generation gas-turbines has led to a relentless quest for new, ultrahigh-temperature structural materials to replace the current nickel-based superalloys. These materials have reached the maximum allowable operating temperature determined by the melting temperature of these alloys, which is about 1150 °C. These materials could be replaced by molybdenum silicides and borosilicides based on Mo5SiB 2 (T2) phase due to their high melting point and mechanical properties. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at elevated temperatures. One novel approach to improve these properties is …

Towards The Scalability And Hybrid Parallelization Of A Spatially Variant Lattice Algorithm, Henry Roger Moncada Lopez

Open Access Theses & Dissertations

The purpose of this research is to design a faster implementation of the spatially variant algorithm that improves its performance when it is running on a parallel computer system.

The spatially variant algorithm is used to synthesize a spatially variant lattice for a periodic electromagnetic structure. The algorithm has the ability to spatially vary the unit cell orientation and exploit its directional dependencies. The algorithm produces a lattice that is smooth, continuous and free of defects. The lattice spacing remains strikingly uniform when the unit cell orientation, lattice spacing, fill fraction and more are spatially varied. This is important for …

Intrinsic And Metal-Doped Gallium Oxide Based High-Temperature Oxygen Sensors For Combustion Processes, Ernesto Javier Rubio

Open Access Theses & Dissertations

Currently, there is enormous interest in research, development and optimization of the combustion processes for energy harvesting. Recent statistical and economic analyses estimated that by improving the coal-based firing/combustion processes in the power plants, savings up to ~$450-500 million yearly can be achieved. Advanced sensors and controls capable of withstanding extreme environments such as high temperatures, highly corrosive atmospheres, and high pressures are critical to such efficiency enhancement and cost savings. For instance, optimization of the combustion processes in power generation systems can be achieved by sensing, monitoring and control of oxygen, which is a measure of the completeness of …

Microstructural Investigation Of Vintage Pipeline Steels Highly Susceptible To Stress Corrosion Cracking, Monica Adriana Torres

Open Access Theses & Dissertations

The use of pipelines for the transmission of gas offers not only efficiency, but a number of economic advantages. Nevertheless, pipelines are subject to aggressive operating conditions and environments which can lead to in-service degradation [1] and thus to failures. These failures can have catastrophic consequences, such as environmental damage and loss of life [2]. One of the most dangerous threats to pipeline integrity is stress corrosion cracking (SCC). Despite the substantial progress that has been achieved in the field, due to the complex nature of this phenomenon there is still not a complete understanding of this form of external …

Investigation Of Ti-6al-4v Alloy Response To Atmospheric Re-Entry Exposure, Jessica Lynn Buckner

Open Access Theses & Dissertations

Ti-6Al-4V is a widely used aerospace alloy for its high strength-to-weight ratio and high operating temperature properties. Despite widespread use, titanium and its alloys have been shown to ignite in oxygen and nitrogen rich test streams. The reactivity of titanium is attributed to the high solubility for oxygen that increases with temperature, accelerating the oxidation rate and resulting in a combustion reaction. When introduced to the monatomic oxygen rich and high enthalpy re-entry environment, Ti-6Al-4V X-link components from the space shuttle Columbia exhibited accelerated oxidation and combustion behavior. Ti-6Al-4V metal plates tested in the simulated re-entry environment of an arc-jet …

Vascularization In Interconnected 3d Printed Ti-6al-4v Foams With Hydrogel Matrix For Biomedical Bone Replacement Implants, Victor Correa

Open Access Theses & Dissertations

Abstract:

Vascularization or angiogenesis on newly implanted metal orthopedic implants has remained a challenge in the field of tissue engineering. In this research, an interconnected foam structure of Ti-6Al-4V was micro-fabricated by Electron Beam Melting (EBM) technique. The foam in question has a density of 1.77g/cm3 with 60% porosity and a tensile strength of 18GPa. An Extracellular Matrix based hydrogel was added as an aqueous matrix to the foam in question. Hypoxia mimetic stress has been closely related to many wound healing biomedical applications as it increases survival and proliferation molecular signals. To that end, increased expression of Hypoxia-Inducible Factor-1α …

Materials Characterization Of Deposits On Starboard (Inboard) Elevon Actuator Shaft Recovered From Space Shuttle Columbia, Mayra Contreras

Open Access Theses & Dissertations

With the new era of space exploration upon us and the Orion spacecraft currently being tested, which would replace the Space Shuttle as the orbiter that will transport humans into space once again, safety assurance is the main component for a successful mission. Aerospace materials have always played a big role when it comes to safety assurance. Having the knowledge of what materials are suitable to keep using when designing the future spacecraft that will take humans to Mars is fundamental in order to be confident that the vehicle and all that comprises it will function as envisioned. Expanding the …

Structural, Dielectric, And Ferroelectric Characterization Of Lead-Free Calcium-Cerium Co-Doped Batio3 Ceramics, Juan Alberto Duran

Open Access Theses & Dissertations

Structure, morphology, and regulation of the dielectric properties via close-composition intervals is demonstrated for variable-cerium, constant-calcium co-doped barium titanate (Ba0.80Ca0.20CeyTi1-yO3; y=0.0-0.25; referred to BCCT). The effect of variable Ce-content on the structure and dielectric properties of BCCT is investigated. X-ray diffraction spectra confirms the studied samples are mainly in BT tetragonal phase with a small secondary phase detected as CaTiO3 in BCCT for y = 0.20 and 0.25. However, the lattice parameter reduction was evident with increasing Ce-content. Composition-driven dielectric constant leap (4,000-5,500) was observed from intrinsic BCT to BCCT for (y = 0.0-0.04). The temperature dependent dielectric constant showed …

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 …

Hybrid Nano-Structure For Enhanced Energy Storage Devices, Mohammad Arif Ishtiaque Shuvo

Open Access Theses & Dissertations

The goal of this research is to develop electrode materials using various nano-structure hybrids for improved energy storage devices. Enhancing the performance of energy storage device has been gaining tremendous attention since it holds the key solution to advance renewable energy usage thus reduce the consumption of fossil fuels. The application of energy storage devices such as super-capacitor and Li-ion-battery has seen significant growth; however, it is still limited mainly by charge/discharge rate and energy density. One of the solutions is to use nano-structure materials, which offer higher power at high energy density and improved stability during the charge discharge …

Processing And Property Evaluation Of Tungsten-Based Mixed Oxides For Photovoltaics And Optoelectronics, Mirella Vargas

Open Access Theses & Dissertations

Tungsten Oxide (WO3) films and low-dimensional structures have proven to be promising candidates in the fields of photonics and electronics. WO3 is a well-established n-type semiconductor characterized by unique electrochromic behavior, an ideal optical band gap that permits transparency over a wide spectral range, and high chemical integrity. The plethora of diverse properties endow WO3 to be highly effective in applications related to electrochromism, gas sensing, and deriving economical energy. Compared to the bulk films, a materials system involving WO3 and a related species (elements or metal oxides) offer the opportunity to tailor the electrochromic response, and an overall enhancement …

Moisture Susceptibility Of Dense Graded Asphalt Concrete Using Cyclic Moistue Induced Stress Tester, Sarvesh Dip Dhakal

Open Access Theses & Dissertations

Moisture damage in asphalt concrete causes loss in mechanical properties of asphalt material due to the presence of moisture in its microstructures in a liquid or a vapor state. Some of the common types of distress observed in asphalt pavements due to moisture damage are stripping (separation of asphalt binder and aggregate), raveling (dislodgement of aggregate particles in asphalt mixture from surface), and hydraulic scour (a process that occurs on a saturated surface by which the pavement material is eroded due to dynamic action of tires in the presence of water). This Thesis focuses on the research on the effects …

Reaction Of Liquid Aluminium- Samarium Alloys With B4c At Ultra High Temperatures, Sanjay Shantha-Kumar

Open Access Theses & Dissertations

Reactive studies between a packed bed of B4C and Al-Sm-Me (Me = Ti, Zr, Hf) alloy melts were carried out under a pseudo-isopiestic thermodynamic system. A graphite enclosure isolated the system under a temperature gradient with one end reaching temperatures greater than 1800 K and the opposite end of the graphite enclosure contains liquid Al with temperatures approximating 950 K. The liquid Al establishes an oxygen potential to control oxidation of very reactive elements (i.e., Al, Sm and Ti). The Al-Sm-Me alloy infuses into a packed bed of B4C reacting exothermically to form borides and carbides depending on the thermodynamic …

High Temperature Oxidation Of Nb-Cr-Mo-Si-B Alloys, Kathryn S. Thomas

Open Access Theses & Dissertations

It has been the trend to use nickel based superalloys in high temperature applications, however higher temperatures are required in the effort to enhance the efficiency of such components as jet turbine engines. The melting temperature of the nickel based superalloy limits the extent to which temperature can be raised as these materials are typically used at temperatures within 200 degrees of their melting point. Refractory metal based systems are attractive due to their high melting points, low densities, and good high temperature strength. However, in such cases as niobium, poor oxidation resistance limits the widespread use of such alloys. …

Defeating Anisotropy In Material Extrusion 3d Printing Via Materials Development, Ángel Ramón Torrado Pérez

Open Access Theses & Dissertations

Additive Manufacturing technologies has been in continuous development for more than 35 years. Specifically, the later denominated Material Extrusion Additive Manufacturing (MEAM), was first developed by S. Scott Crump around 1988 and trademarked later as Fused Deposition Modeling (FDM). Although all of these technologies have been around for a while, it was not until recently that they have been more accessible to everyone. Today, the market of 3D printers covers all ranges of price, from very specialized, heavy and expensive machines, to desktop printers of only a few cubic inches in volume. Until recently, FDM technology had remained somewhat stagnant …

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 …

Novel Engineered Nanomaterials For Water Remediation And Gas Adsorption: Graphene Oxide And Carbon Nanotubes Decorated With Metal-Organic Frameworks And Magnetic Nanoparticles, Vahid Jabbari

Open Access Theses & Dissertations

In the current study, a series of novel magnetic and non-magnetic hybrid nanocomposites based on metal-organic frameworks (MOFs) of M3(BTC)2 (M: Ni, Cu, Zn, and Cd), graphene oxide (GrO), and carbon nanotubes (CNTs), and Fe3O4 magnetic nanoparticles (MNPs) were developed via a green, simple and versatile solvothermal method at which GrO and CNT were used as platform to grow the MOFs and Fe3O4 MNPs over them. The as-synthesized nanocomposites were characterized by XRD, SEM, TEM, XPS, IR, Raman, TGA, and N2 adsorption/desorption isotherms. Morphological analysis confirmed successful growth of nano-size Fe3O4 MNPs and M3(BTC)2 MOFs over GrO and CNT platforms. …

A Methodology For Use Of Digital Image Correlation For Hot Mix Asphalt Testing, Estefany Ramos

Open Access Theses & Dissertations

Digital Image Correlation (DIC) is a relatively new technology which aids in the measurement of material properties without the need for installation of sensors. DIC is a noncontact measuring technique that requires the specimen to be marked with a random speckled pattern and to be photographed during the test. The photographs are then post-processed based on the location of the pattern throughout the test. DIC can aid in calculating properties that would otherwise be too difficult even with other measuring instruments.

The objective of this Thesis is to discuss the methodology and validate the use of DIC in different hot …

Acoustic Emission Characteristics Of Damage Accumulation In Kevlar® 49 Composites, Eduardo Andrade

Open Access Theses & Dissertations

Acoustic emission (AE) data attained during tensile testing of epoxy impregnated Kevlar® 49 (K/Ep) composite strands were reduced and analyzed to monitor progressive damage accumulation during the approach to tensile failure. The K/Ep material tested in this study was chosen due to its similarity to the material-of-construction used in composite overwrapped pressure vessels (COPVs) used on the NASA Space Shuttle Orbiter. Insight into the progressive microstructural degradation of K/Ep strands was gained by monitoring AE event rate and energy. Source location based on energy attenuation and arrival time data was used to differentiate between significant AE attributable to microstructural damage …

Novel Endohedral Derivatives Of Sc3n@C2n (N = 34, 40) And Unique Tether Controlled Bis-Functionalization Of Fullerenes, Maira Raquel Ceron Hernandez

Open Access Theses & Dissertations

Since the discovery of fullerenes in 1985, their exohedral functionalization has been necessary to increase their solubility and explore their properties and potential applications in materials science and medicinal chemistry. This Thesis provides a short overview of the importance of electronic, size and shape complementarity in determining the structures of specific endohedral fullerene compounds. This is followed by a description of a new method for the separation of scandium nitride endohedral fullerenes Sc3N@C2n (n = 34, 39 and 40), and their monofunctionalization.

We also present the regioselective synThesis of easily isolable bis-derivatives of C60, C70, and M3N@Ih-C80 (M = Sc, …

Transition States And Modeling For Co9s8/Mos2 Catalysis, Gabriel Angel Gonzalez

Open Access Theses & Dissertations

Transition state computational studies of the sulfur removal from dibenzothiophene (DBT) molecule have herein been performed considering the Co9S8/MoS2 interface existing on unsupported Co/MoS2 catalysts. The linear synchronous transit (LST) and quadratic synchronous transit (QST) methods integrated in a density functional theory (DFT) program such as Dmol3 were used for the calculations of energy barriers of the transition states. Three different configurations present on the Co9S8/MoS2 interface have been envisaged as possible catalytic sites: sulfur-sulfur (S, S) sites, and molybdenum-sulfur (Mo, S) and molybdenum-molybdenum (Mo, Mo) edge sites. This study revealed that the (Mo, Mo) edge site is the most …