Materials Science and Engineering Commons^™

Subwavelength Engineering Of Silicon Photonic Waveguides, Farhan Bin Tarik

All Dissertations

The dissertation demonstrates subwavelength engineering of silicon photonic waveguides in the form of two different structures or avenues: (i) a novel ultra-low mode area v-groove waveguide to enhance light-matter interaction; and (ii) a nanoscale sidewall crystalline grating performed as physical unclonable function to achieve hardware and information security. With the advancement of modern technology and modern supply chain throughout the globe, silicon photonics is set to lead the global semiconductor foundries, thanks to its abundance in nature and a mature and well-established industry. Since, the silicon waveguide is the heart of silicon photonics, it can be considered as the core …

Study Of Thin Gan/Ingan/Gan Double Graded Structures For Future Photovoltaic Application, Mirsaeid Sarollahi

Graduate Theses and Dissertations

Indium gallium nitride (In_x Ga_(1-x) N) materials have displayed great potential for photovoltaic and optoelectronic devices due to their optical and electrical properties. Properties such as direct bandgap, strong bandgap absorption, thermal stability and high radiation resistance qualify them as great materials for photovoltaic devices. The tunable bandgap which absorbs the whole solar spectrum is the most significant feature which became attractive for scientists. The bandgap for these materials varies from 0.7 eV for InN to 3.4 eV for GaN covering from infrared to ultraviolet. In_x Ga_(1-x) N wurtzite crystal is grown on GaN buffer layer by Molecular Beam Epitaxy …

Study Of Single-Photon Wave-Packets With Atomically Thin Nonlinear Mirrors, Christopher Klenke

Graduate Theses and Dissertations

A novel controlled phase gate for photonic quantum computing is proposed by exploiting the powerful nonlinear optical responses of atomically thin transition metal dichalcogenides (TMDs) and it is shown that such a gate could elicit a π-rad phase shift in the outgoing electric field only in the case of two incident photons and no other cases. Firstly, the motivation for such a gate is developed and then the implementation of monolayer TMDs is presented as a solution to previous realization challenges. The single-mode case of incident photons upon a TMD is derived and is then used to constrain the more …

Multi-Technique Characterization Of Superconducting Materials For Particle Accelerator Applications, Junki Makita

Physics Theses & Dissertations

We investigated the performance limitations of superconducting radio-frequency (SRF) cavities and materials using multiple experimental techniques. In particular, this study focuses on understanding the surface properties of nitrogen-doped Nb cavities and superconducting thin films with higher T_c such as Nb₃Sn. The main goal of this work is to use different techniques to better understand each aspect of the complex loss mechanism in superconductors to further improve the already highly efficient SRF cavities.

Nitrogen doping applied to a Nb SRF cavity significantly improves the quality factor Q₀ compared to a conventional Nb cavity, at an expense of …

Development Of Smart Wearable Sensory Systems On Flexible And Fabric Platforms For Health Monitoring Applications, Simin Masihi

Dissertations

Wearable sensing technology has recently received an increased attention in both research and commercialization phases and has moved from a vision of science fiction to reality with a wide variety of applications. This incredible growth can be attributed to several factors, such as affordability and ergonomics provided by advances in flexible electronics. The other factors that realized wearable sensing technology include a critical need for more accessible health care services experienced during the recent COVID pandemic, integration to the Internet of Things (IoT), and a growing consumer desire for health awareness. This dissertation presents the fulfillment of three main projects …

Modeling Pattern Formation And Morphology Development In Polymer Networks, Yao Xiong

All Dissertations

Topography and morphology have considerable impacts on the functionalities of soft materials in an entire range of applications from smart optics to tissue engineering. Adapting theoretical and computational approaches, we focus on the dynamics of pattern formation and morphology development in polymer networks. This dissertation starts with studying the dynamical control of pattern formation in confined thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) gel films. The patterns are formed due to mechanical instabilities. We perform a linear stability analysis and identify the limits of this analysis in predicting pattern formation in gels. We then study the restructuring between patterns and hysteresis phenomena …

Quantum-Mechanical Evaluation Of Defects In Uranium-Bearing Materials, Megan Hoover

All Dissertations

Quantum-mechanical calculations using density functional theory with the generalized gradient approximation were employed to investigate the effects dopants have on the uranium dioxide (UO₂) structure. Uraninite is a common U⁴⁺ mineral in the Earth's crust and an important material used to produce energy and medical isotopes. Though the incorporation mechanism remains unclear, divalent cations are known to incorporate into the uranium dioxide system. Three charge-balancing mechanisms were evaluated to achieve a net neutral system, including the substitution of (1) a divalent cation for a tetravalent uranium atom and oxygen atom; (2) two divalent cations for a tetravalent …

Modeling Hierarchical Porous Electrodes With Tailored Anisotropic Structure, Debanjan Sarker

All Theses

Modern electric vehicles and consumer electronics applications demand high specific energy from Li-ion batteries, which can be charged and discharged faster. In the search for high specific energy, researchers have tried to make thicker battery electrodes which contain a greater proportion of active material. While chemical and structural modification of electrodes can help to increase the electronic conductivity of active material, the microstructure of porous electrodes can be engineered to enhance ion transport for fast charge and discharge. Previous research has shown that macropores introduced by directional freeze tape casting can enhance the performance of thick porous electrodes. For instance, …

Characterization Of Thermal Gelation Properties In Bioresorbable Thermally Activated Hydrogel Polymers For Hernia Surgery Applications, Alexander Mayfield

All Theses

Hydrogel adhesives are a new class of materials with excellent biocompatibility, which makes them very attractive for biomaterial applications. It has been previously shown that Tetronic T1107, a four-arm poly (propylene oxide)-poly (ethylene oxide) (PPO-PEO) block copolymer, is useful as a chemical crosslinking thermo-responsive hydrogel for bioadhesive applications. The end groups of this polymer are modified with acrylate and N-hydroxysuccinimide (NHS) functional groups. The acrylate end group gives the polymer cohesive properties with long-range chemical crosslinking using dithiothreitol (DTT), while the NHS end group gives the polymer adhesive properties through bonding with amines found in organic tissue. It was found …

A Comparison Of Uniaxial Compressive Response And Inelastic Deformation Mechanisms In Freeze Cast Alumina-Epoxy Composites Without And With Rigid Confinement, Tareq Aljuhari

Mechanical & Aerospace Engineering Theses & Dissertations

Cellular ceramics have an array of improved mechanical properties that make them incredibly desired for different applications such as armor systems, aircraft structures, automobiles bumpers, and biomedical implants. It is also desirable that porous architecture could be shaped into bulk complicated shapes and easy to scale-up with low manufacturing cost. Despite several efficient techniques to fabricate cellular ceramics, some limitations are preventing us from meeting the high demand of the after mentioned applications. For that, freeze casting, also called ice-templating, is technique of solidifying an aqueous ceramic suspension under the effect of unidirectional temperature gradient. In this study, Ice-templated porous …

Fabrication Of Nb3Sn By Magnetron Sputtering For Superconducting Radiofrequency Application, Md Nizam Sayeed

Electrical & Computer Engineering Theses & Dissertations

Particle accelerators are considered as an important device that has wide applications in cancer treatment, sterilizing waste, preserving foods, ion implantation in semiconductor industry, and in production of isotopes for medical applications. Superconducting radiofrequency (SRF) cavities are the building blocks of a linear particle accelerator. Current particle accelerators use niobium (Nb) superconductors as the sheet material to fabricate a single SRF cavity for particle acceleration. With better superconducting properties (critical temperature T_c ~ 18.3 K, superheating field H_sh~ 400 mT), Nb₃Sn is considered a potential candidate in SRF technology. Magnetron sputtering is a promising deposition …

Role Of Structural Hierarchy In Multiscale Material Systems, Siavash Sattar

Mechanical & Aerospace Engineering Theses & Dissertations

Multiscale material systems derive their effective mechanical properties through a hierarchical organization of their structural elements and components. The hierarchy of a material is related to its effective properties, material processing, and composition. The hierarchy can be defined as an identifiable structural component with a specific size scale, such as the individual fibers collimated into platelets arranged randomly and producing a complex composite system or the lamellar structure in freeze-casted ceramic with the variation of in-plane orientation. In this study, the role of the structural hierarchy on the effective mechanical response and failure behavior of three complex material systems was …

Predictive Thermal Modeling And Characterization Of Ultrasonic Consolidation Process For Thermoplastic Composites, Madeline Kirby

LSU Master's Theses

Ultrasonic consolidation (USC) of thermoplastic composites (TPCs) is a highly attractive and promising method to manufacture high-performance composites. This work focuses on USC of dry carbon fiber (CF) fabrics with high-temperature polyphenylene sulfide (PPS) films. Experimental trials to assess feasibility of the process are time-consuming. Consequently, a predictive thermal model would facilitate process parameters selection to reduce expensive trial-and-error approaches. This paper presents a 2D finite element model of samples under consolidation, incorporating equations for viscoelastic heating, matrix phase change, and material properties. Theoretical temperature profiles for nodes of interest were compared to the corresponding experimental temperature curves for various …

Evaluation Of The Energetic Factors In Crystalline Pharmaceuticals Using Solid-State Density Functional Theory And Low-Frequency Vibrational Spectroscopy, Margaret P. Davis

Dissertations - ALL

Due to the importance of maintaining stable and effective pharmaceutical solid doses, it is critical to study the variety of solid forms that active pharmaceutical ingredients can adopt including polymorphs, hydrates, and cocrystals. In this work, low-frequency vibrational spectroscopies and rigorous quantum mechanical simulations are combined to provide a new technique for characterizing and investigating pharmaceutically relevant polymorphs, hydrates, and cocrystals as well as a series of model cocrystals. Low-frequency spectra in the sub-200 cm-1 range provide not only unique and characteristic spectra for all of the systems explored here but, along with X-ray structural parameters, they offer a way …

New Solid Polymer Electrolytes For Lithium, Sodium, And Calcium-Based Batteries, Francielli Silva Genier

Dissertations - ALL

The establishment of sustainable energy sources highly depends on efficient storage devices to guarantee a consistent power supply. The growing demand for lithium-ion batteries (LIBs) for this purpose, combined with concerns about lithium availability, has motivated the search for viable storage alternatives, such as sodium and calcium. While several studies have investigated different lithium-free liquid electrolytes, the transport of these alternative ions in their polymer counterparts remains understudied. The advantages of solid polymer electrolytes include the possibility of higher energy density in solid-state devices and the elimination of safety concerns associated with liquid electrolytes, such as flammability, leakage, and dendrite …

Damage In Non-Crimp Fabric Carbon Fiber Reinforced Epoxy Composites Under Various Mechanical Loading Conditions, Aaditya Pradeep Suratkar

Electronic Thesis and Dissertation Repository

Composite materials have emerged in the recent years as a frontrunning lightweight replacement for metals for structural applications in lightweight automobiles. However, the key adoption criteria for composites in lightweight vehicles is their crashworthiness, i.e., the amount of energy a structure made with composites would absorb in a crash event. The energy is absorbed in composites through various damage modes such as matrix cracks, delamination, fiber breakage, etc. Therefore, adoption of a certain composite material system requires thorough understanding of the initiation and propagation of damage until failure in that system under various mechanical loading conditions, which is also the …

Impedance Analysis Of Anodized Aluminum And Structural Bridge Tendons, Justin Silnutzer

USF Tampa Graduate Theses and Dissertations

This is a two-part thesis with the overall investigation technique being electrochemical impedance spectroscopy (EIS). In the first part, EIS is used to estimate the layer thickness of anodized aluminum oxide. This required the development of an appropriate electrical circuit model; that with parameters that correspond to physical properties of the oxide. In this work, it was found that for thicker oxides of which the outer porous layer is greater than 12 microns, impedance may be used to estimate the outer layer thickness. However, further research is required to understand the role of outer porous layer structure on the impedance …

Additive Manufacturing Of Sub-Micron Features And Mechanical Linkages, David K. Limberg

Doctoral Dissertations

In recent years material constraints have become the limiting factor in several fields, including batteries, robotics, and medicine, and these needs have prompted the development of materials with programmable properties. To this end, much effort has been dedicated to designing metamaterials that have unprecedented optical, mechanical, and thermal properties, along with systems for additive manufacturing to build their complex structures with high precision and throughput. The field of additive manufacturing has proved to be a platform for innovation across many industries yet is still limited with regards to feature sizes, print rates, and diversity of materials. Mechanical devices like linkages …

Phase Behavior Of Oppositely Charged Polymerized Ionic Liquids In Solution, Bulk, And Crosslinked Network States, Minjung Lee

Doctoral Dissertations

Polymerized ionic liquids (PILs), a class of polyelectrolytes, are fascinating materials for various applications utilizing ion transport, especially due to their advantageous properties including negligible vapor pressure, low flammability, thermal stability, high conductivity, and wide electrochemical stability windows. Furthermore, PILs are tunable in their properties such as ionic conductivity, glass transition temperature (T_g), solubility, and (electro-)chemical stability. In this thesis, we focus on fundamental studies of phase behaviors of PILs in the solution and bulk states in chapters 2 and 3, respectively. Specifically, non-aqueous systems are used to study the effect of solvent quality in the regime …

Hydration Kinetics, Microstructure, And Mechanical Strength Development Of Cement-Based Composites Incorporating Phase Change Materials, Afshin Marani

Electronic Thesis and Dissertation Repository

The research conducted in this thesis investigates the effects of phase change materials (PCMs) on the hydration kinetics and strength development of cement-based composites using extensive experimental and numerical analyses. Purposefully, the effect of microencapsulated PCMs (MPCMs) on the strength development of cement-based mortars and concretes was evaluated using powerful machine learning models trained with the largest available experimental data. Furthermore, a novel ternary machine learning approach was proposed to optimize the mixture design of mortars and concretes based on the thermos-physical properties of the MPCMs. The results obtained from machine learning simulations suggest the assessment of the effects of …

Processing And Characterization Of Silicon Nitride For Rapid And Low-Level Detection Of Water Pathogens, Arielle H. Buchanan, Logan A. Chai

Materials Engineering

Water sanitation is a serious issue affecting the lives of many, and methods for assessing water cleanliness have been a major research interest for decades. Rapid and accurate water pathogen detection methods that can be performed in field applications have been a growing research focus, especially in low-income countries most affected by poor water quality. Silicon nitride was explored as a material for colorimetric water-pathogen sensing due to the large body of knowledge around its processing, and its isoelectric point. A bioassay of chlorophenol red-β-Dgalactopyranoside (CPRG) and β-galactosidase (β-gal) enzymes with Escherichia coli (E. coli) bacteria was used to examine …

In Situ Marine Biodegradation Of Poly(Lactic) Acid And Thermoplastic Starch Blends, Brittany Denicholas

Materials Engineering

Marine life has been suffering from macro- and microplastics since the inception of petroleum-based plastic. Bio-based biodegradable polymers such as PLA and TPS can help mitigate the damage done by petroleum plastics. Blending PLA and TPS can reduce the cost while preventing a significant effect on the material properties. PLA/TPS blend compositions such as 90/10, 80/20, 70/30 could be candidates for a solution. The PLA/TPS blends have been submerged in a marine environment at the Cal Poly Pier in Avila Beach for 8 weeks. Three sample sets containing three of each blend composition were collected every week and tested in …

Effect Of Oxygen Equivalence On The Strength And Toughness Of Ti-6al-4v Forgings, Kira Baylor, Clarissa Drouillard

Materials Engineering

Tensile testing and fracture toughness testing were conducted to establish a numerical relationship between interstitial content and performance in forged Ti-6Al-4V. The value of oxygen equivalence was used to represent the interstitial content by combining the weight percent of oxygen, carbon, and nitrogen. The correlation between oxygen equivalence and mechanical properties can be used to accurately predict the performance of forged parts. Samples of forged parts with varying levels of interstitial content were subjected to a recrystallization anneal at 75 F below the beta transus temperature to decrease microstructure variability across parts with a second anneal at 1300 F to …

Citric Or Acetic Acid Effects On The Crosslinking Of Pvoh, Samuel Carr, Erika Szaldobagyi

Materials Engineering

Transportation and shipping processes are the most dangerous times for food due to harsh handling and frequent temperature changes. Plain corrugated boxes cannot withstand the damp environment caused by melting ice that is used to keep foods cold and fresh. To minimize damage, a protective polymer film coating can be applied. These coatings can be unsafe when used with food and will lead to excess waste by limiting the recyclability of the boxes. The purpose of this project was to produce nontoxic crosslinked PVOH films to determine suitability for a cost effective, biodegradable, and repulpable corrugated box coating. Polyvinyl alcohol …

Stabilization Of Palm Wood Using Water-Based Impregnation, David A. Barnes

Materials Engineering

Impregnation is a technique for stabilizing wood that involves saturating the material in a liquid and allowing it to cure before use. Stabilization methods such as this are employed for a variety of reasons; chiefly, the low dimensional stability of wood and palm means that they are subject to several failure modes that arise from changing environmental conditions, such as cracking, warping, and bending. Samples of Borassus flabellifer, black palm, provided by DuraPalm were impregnated with solvent-based and water-based stabilizers, and untreated wood samples used as a control group. Kop-Coat WoodYouth® Plus was used as a solvent-based stabilizer, and impregnation …

Determining The Efficacy Of A Silica And Bacterial Cellulose Composite Model System, Hannah Martin, Daisy Kamp

Materials Engineering

Bacterial cellulose (BC) is a sustainable alternative to petroleum-based polymer films for synthetic leather applications. Synthesized by a symbiotic culture of bacteria and yeast, BC is a three-dimensional structure composed of cellulose microfibrils. However, pure BC lacks certain desirable properties such as high tensile strength. Previous studies have shown that loading BC with nanoparticles to form nanocomposites has improved BC’s mechanical properties. However, this was not studied as a function of particle size. This study focuses on using silica/BC nanocomposites to model the impact that particle size and silica soaking concentrations have on the uptake efficiency of these particles into …

Effects Of Release Materials And Temperature Ramp Rates On The Surface Finish Of Carbon-Fiber Composite Components, Sudeep Louis, Thucmy Dang, Ethan Schlocker

Materials Engineering

Toray Advanced Composites is interested in improving their carbon fiber reinforced polymers (CFRP) manufacturing process by enhancing their control on the amount of surface roughness for varied customer preference. Surface roughness of CFRP is important in post-production processes including coating, priming, and painting. This project seeks to determine the effects of three release materials and two temperature ramp rates on the surface finish of CFRP. The release materials used were Tooltech, FEP, and Frekote 770-NC. The two initial temperature ramp rates were 1°F/min and 2°F/min. Surface roughness was measured using a profilometer and analyzed using Ra values. Ra is an …

Analysis Of Novel Corrosion Resistant Maraging Steels For Use In Additive Manufacturing, Bradley Michael Samuel, James Knowlton Smith

Materials Engineering

Stainless maraging steel has been proven to be an industry standard material for plastic injection molds. Its high hardness and corrosion resistance extend the lifetime of the tool. This alloy system is also well-suited to additive manufacturing, which can be utilized to form internal cooling channels, further increasing tool life. Using Rapid Alloy Development (RAD) Oerilkon METCO is developing a new composition of stainless maraging tool steel that has high hardness/strength, is corrosion resistant, and has additive-capable melting and solidification properties. This study tests the hardness and corrosion resistance of the new RAD alloys against the current market competitor Corrax …

Investigation Of The Effects Of Cladding Layers On Longitudinal And Transverse Mechanical Properties In Composite Laminates, Rachel Potratz, Tiffany Foo, Joseph Kamlet

Materials Engineering

The addition of cladding layers to composite laminates is used in industry to improve bond adhesion and the ease of manufacturing. However, there is no public data on the effects of cladding layers on the mechanical properties of composite components. To directly observe how cladding layers affect mechanical properties, four laminates with zero, one, two, and three cladding layers of twill fabric were added symmetrically to a biased core. The mechanical testing performed was tensile, short beam strength, and compression testing in the longitudinal and transverse directions. The measured strengths were related to the longitudinal properties of the core, and …

Non-Destructive Material Analysis Of Metals And Composites Via Thermography, Jonathan R. Doubt, James L. Chapman

Materials Engineering

The Naval Surface Warfare Center, Port Hueneme Division, is interested in the development of non-destructive damage assessment of shipboard materials via drones at distance. Long Pulsed Thermography (LPT), a method of non-destructive evaluation, was investigated as a possible method for detecting damage in metals (5005h24 Al alloy and 1008 carbon steel) and composites (aramid fiber honeycomb sandwich structure) at distances from 0.5 m to 3.0 m. LPT was conducted using two 1000 W can lights to heat the samples, and a FLIR E8-XT thermal camera. The images were then analyzed using ImageJ software to determine if damage could be detected …