Materials Science and Engineering Commons^™

Experimental Investigation Of Liquid Metal Embrittlement In Hot-Dip Galvanized Structural Steel, Amelia Mcnamee

College of Graduate Studies: Theses & Dissertations

This research investigated the liquid metal embrittlement (LME) of hot-dipped galvanized structural steel. The relationship between stress and failure time was analyzed to evaluate the potential presence of a critical stress threshold beyond which LME may occur. A testing apparatus to induce axial stress was designed and assembled in-house. A36 low carbon steel was tested in this study. Different deadweight loadings were applied to the testing sample along the axial direction. The test temperature was maintained by a programmable furnace while the sample gauge section was submerged in a molten zinc bath. Failure time and total displacement of the steel …

Effects Of Additions On The Microstructure, Macrostructure, And Mechanical Properties Of Gray Iron, Evan J. Carter

College of Graduate Studies: Theses & Dissertations

The iron matrix is a major component of the gray iron (GI) microstructure, which is the transformation product of austenite during solidification. It is generally accepted that the structure of the austenite will impact the final grain structure and thus the properties of GI. Refinement of the austenite grain structure has the potential to increase the strength of GI. Knowledge of controlling austenite grain size with common alloy additions in GI is very limited and is investigated in this research. Utilizing the DAAS heat treatment process, the austenite grain boundaries can be retained and observed directly. The observations were correlated …

Investigation Of Mechanically Fatigue Low-Frequency Energy Harvesting Effects On Isotropic Materials, Daniel J. Meade

College of Graduate Studies: Theses & Dissertations

This research project reports an exploratory investigation of energy harvesting effect on isotropic material that goes through low frequency mechanical fatigue. Energy harvesting is a growing field of study that can recycle ambient energy back into a system that would otherwise be lost. This is a significantly useful method for the ongoing energy crisis and provides an alternate route to design and upgrade systems to be more efficient and last longer than current system designs. However, it is time to investigate if there is any effect vibration-based energy harvesting has on the structure from which energy is being harvested. To …

Thermomechanical Process Simulation And Quantification Of Nanoscale Precipitation Influencing Ductility And Strength During Alloy Processing, Alyssa Stubbers

Theses and Dissertations--Chemical and Materials Engineering

Experimental process simulation and quantification of microstructure development during processing are challenging due to limitations with machinery temperature capability, inadequate resolution and sampling volume of currently available characterization techniques, and difficulty characterizing material microstructures as close to processing-relevant conditions as possible. This dissertation addresses how process simulation can be performed using Gleeble thermomechanical technologies and how microstructure development during these processing simulations can be quantified both in-situ and ex-situ.

The first portion of this dissertation demonstrates how Gleeble technologies can be applied to simulate complex material processing conditions in order to produce process-property profiles that can be used to inform …

Faceting Of Tungsten Via Environmental Control Of Temperature, Pressure And Chemistry, And Evolution Of Thermionic Cathode Materials, Huanhuan Bai

Theses and Dissertations--Chemical and Materials Engineering

Scandate cathode presents a great potential of being used as electron emitters in vacuum electron device due to its excellent emission performance. However, it is burdened by several issues, including poor emission uniformity, inadequate reproducibility, and limited lifetime, which have impeded its further industrial application. Therefore, extensive efforts and studies need to be conducted to obtain a more comprehensive understanding of scandate cathode.

W particles, as the base material, play a fundamental role in scandate cathode. Most recent experimental research has reported that the highly faceted crystallography of W grains contributes to the properties of scandate cathode. In order to …

Experimental Characterization And Quantification Of Deformation Behavior In A Porous Carbon Fiber Network, Robert N Quammen

Theses and Dissertations--Chemical and Materials Engineering

Due to their wide range of attractive functional properties (such as low thermal conductivity and low density) porous materials are utilized in a variety of applications. In order to characterize these properties and others, the intrinsically heterogeneous microstructures of these materials need to be taken into account. These microstructures result in interactions across multiple length scales spanning several orders of magnitude. This makes the creation of robust computational models and straight-forward predictions of mechanical properties difficult for porous materials. With this in mind, this dissertation aims to provide experimental mechanical and deformation information spanning the length scales of interest for …

Novel Precursors For Carbon Fiber Prepared By Direct Carbonization, Leah Noble

Theses and Dissertations--Chemical and Materials Engineering

For decades carbon fiber-based composites have been most heavily employed in lightweight, structural applications where low density and high strength are necessary, most notably within the aerospace industry. However, the advancement of carbon fiber into a wider array of industries has largely been limited by the high financial and energetic costs associated with its manufacture. Moreover, with an increasing societal emphasis on sustainability, there is an ever-growing desire for low-energy carbon fiber production pathways. One such pathway is the conversion of precursor fiber to carbon fiber by direct carbonization, wherein the energy-intensive, pre-carbonization stabilization step is omitted from the carbonization …

Nickel Superalloy Composition And Process Optimization For Weldability, Cost, And Strength, Sophie A. Mehl

Dissertations, Master's Theses and Master's Reports

To advance sustainability efforts, electric power plants have reduced specific carbon dioxide emissions by increasing operating temperatures and pressures to improve power generation efficiency. The latest improvements are utilized in advanced ultra-supercritical power generation. To meet these operating conditions, nickel superalloys are used in the highest temperature components; however, they are expensive and present weldability challenges. This project aims to experimentally optimize a nickel superalloy to improve material weldability and decrease cost without compromising strength. Three optimized compositions were developed, and their microstructures and mechanical properties were compared to Nimonic 263, a common nickel superalloy in electric power plants. The …

Anaerobic Reductive Bioleaching Of Manganese Ores, Neha Sharma

Dissertations, Master's Theses and Master's Reports

Manganese extraction by biological methods is a green and economical way to produce manganese from low as well as high grade manganese ores. This is especially important for US ores, which are primarily either small in extent, low-grade with a high iron content, or both. They are therefore not suitable for conventional mining, which is very capital-intensive and requires a large up-front investment and are therefore imported at high costs. The goal is therefore to develop a process that can be applied at small scales, with minimal startup costs, and low equipment and labor requirements. It is also critical to …

Halide-Assisted Growth Of Transition Metal Dichalcogenides, Vinaayak Sivam Balasubramaniam

Dissertations, Master's Theses and Master's Reports

Monolayers of transition metal dichalcogenides (TMDCs) have attracted significant attention as the rare two-dimensional (2D) semiconducting materials with a direct energy band gap. Chemical vapour deposition (CVD) is one of the scalable techniques to grow atomically thin TMDC monolayers in high quality, but it requires high growth temperature. Herein we report the growth of MoS2, WS2 and MoSe2 by a one-step halide-assisted CVD method using NaCl and KCl as the catalysts. These halides could reduce the growth temperature of TMDCS by reacting with the precursors (TMDC powders) to form volatile intermediate compounds as the growth species. We use optical microscopy, …

Fatigue Resistant Cast Steel Railcar Couplers Produced By Wire-Arc Additive Manufacturing (Waam), Samuel Vellequette

Dissertations, Master's Theses and Master's Reports

Every year, approximately 90,000 cast steel railcar coupler knuckles are replaced preemptively to avoid fatigue failure. The coupler geometry has been in service since the early 1930s, so geometry changes are restricted to maintain compatibility with the existing fleet. Defects from the casting process, decarburization during heat treatment, and in-service exposure to corrosive environments combine to promote fatigue crack nucleation in high-stress regions of the knuckle. Wire-arc additive manufacturing (WAAM), which uses traditional welding techniques to build material to near-net shapes, was employed to deposit higher-strength materials in critical regions. By replacing the cast steel in the high-stress region of …

Single-Atom Catalysts For Electrochemical Energy Conversion: Copper Single-Atom Catalyst For Oxygen Reduction Reaction And Quantification Of Site Density By Co Stripping Voltammetry, Dawatage Perera

Theses and Dissertations--Chemistry

Fuel cells are considered a promising technology for achieving cleaner and more sustainable energy production and utilization. However, one of the current major challenges is the economic viability associated with the extensive use of Pt group metal (PGM) catalysts, particularly on the cathode side. Therefore, non-PGM single-atom catalysts (SACs) have received considerable attention as alternatives for PGM catalysts in the oxygen reduction reaction (ORR), which occurs at the cathode of the fuel cell. Among various SAC structures, the non-PGM/nitrogen-doped carbon-based structure (M-N-C) stands out for its excellent ORR performance.

Chapter 2 illustrates the use of copper metal in place of …

Applying Synchrotron Saxs And Xas To Study The Microstructure Of Energy Conversion And Storage Materials, Lingzhe Fang

Graduate Research Theses & Dissertations

The microstructure of energy conversion and storage materials is a key determinant of physical properties and electrochemical performance. Synchrotron X-ray techniques, with their strengths of high flux and exceptional brightness, play an irreplaceable role in understanding nano and sub-nano structures. This helps the study of reaction mechanisms and benefits material design in energy conversion and storage area. Electrifying CO2 transformation using renewable energy offers a carbon-neutral solution to CO2 recycling and fuel generation. Among various feedstocks from the CO2 reduction reaction, CO, HCOOH, and CH4 have approached the performance thresholds for industry implementation. The application of single atom catalysts (SACs) …

Novel Membrane Materials For Nutrient Recovery From Nutrient-Rich Resources, Km Prottoy Shariar Piash

Graduate Theses, Dissertations, and Problem Reports (ETD)

Global demand for fertilizer production is expanding substantially to meet the food demand of an increasing world population. Anaerobic digestate (AD) of various centralized wastewater facilities contains substantial amounts of ammonium (NH₄⁺) (300-800 mg/L), potassium (K⁺) (13-120 mg/L), and phosphorus (P) (30-100 mg/L)- based nutrients. In addition to reducing energy costs and CO₂ emissions compared to conventional fertilizing raw material manufacturing, recovering nutrients from these waste streams could help mitigate problems such as eutrophication, which otherwise incurs billions of dollars losses to US economy annually. Apart from nutrients, wastewater streams also contain organic pollutants …

Passive Wireless Corrosion And Temperature Detection In High-Temperature Environments, Noah Lane Strader

Graduate Theses, Dissertations, and Problem Reports (ETD)

This work focuses on the theory and development of LC sensors for high temperature and corrosion measurement for stainless steel and copper surfaces with power industry and general corrosion detection applications. The LC resonators were fabricated via screen printing an Ag inductor on an alumina substrate. The LC design was modeled using the ANSYS HFSS modeling package. The LC passive wireless sensors operate with resonant frequencies centered at 85-110 MHz. The wireless response of the LC sensor was interrogated and received by a radio frequency signal generator and spectrum analyzer at temperatures from 50-800 °C for copper ground planes and …

Photoexcited Charge Carrier Dynamics And Electronic Properties Of Two-Dimensional Mxene, Nb2ctx, Andrew M. Fitzgerald, Emily Sutherland, Tarek A. Elmelegy, Mary Qin Hassig, Julia Martin, Erika Colin-Ulloa, Ken Ngo, Ronald L. Grimm, Joshua R. Uzarski, Michel W. Barsoum, N. Aaron Deskins, Lyubov V. Titova, Kateryna Kushnir Friedman

Mechanical Engineering

Two-dimensional, 2D, niobium carbide MXene, Nb2CTx, has attracted attention due to its extraordinarily high photothermal conversion efficiency that has applications ranging from medicine, for tumor ablation, to solar energy conversion. Here, we characterize its electronic properties and investigate the ultrafast dynamics of its photoexcitations with a goal of shedding light onto the origins of its unique properties. Through density functional theory, DFT, calculations, we find that Nb2CTx is metallic, with a small but finite density of states at the Fermi level for all experimentally relevant terminations of Nb2CTx that can be achieved using HF or molten salt etching of the …

Corrosion Characteristics Of Ti And Al2o3/Ti Thin Films Sputtered On 316lss, Iman El-Mahallawi, Hanan ِ Abd El-Fattah Dr., Lamiaa Mohamed Dr., Aliaa Abdelfattah

Mechanical Engineering

In this work, two thin films (Ti and Al2O3/Ti) were deposited on 316LSS substrates by the physical vapor deposition (PVD) sputtering technique. Heat treatment was applied for thin films at 400 °C for 2 h. Thin films were divided into two groups, The First group cooled in the air (normalized), and the second cooled in the furnace (annealed). The electrochemical characteristics were investigated by potentiodynamic polarization (POT) and impedance spectroscopy (EIS) tests. The corrosion resistance (CRST) for all thin films before and after heat treatment was determined in 3.5% NaCl at room temperature (RT). Scanning electron microscope (SEM), and surface …

Development And Characterization Of Ceramic Devices For Capillary Action In Microgravity For The Purpose Of Growing Vegetables In Space, Lucas S. Mougeot

UNF Graduate Theses and Dissertations

The future of humanity is often rendered in spectacular visions of a multiplanetary civilization with a booming space economy. Reaching this reality requires addressing one of the core needs of survival: food. Porous ceramics used for Passive Porous Tube Nutrient Delivery Systems (PPTNDS) offer a promising solution. In microgravity environments such as the International Space Station (ISS), fluid dynamics and liquid coagulation do not support conventional agricultural practices. Porous ceramic materials present a solution that enables nutrient solution diffusion via capillary action.

In this research, it was determined that extruding a wadding ceramic tube and sintering it at 1900 °F …

Influence Of Heat Treatment And Shielding Gas Environment On The Very High Cycle Fatigue Behavior Of 17-4 Precipitation Hardened Stainless Steel, Jade Welsh

UNF Graduate Theses and Dissertations

Additive manufacturing (AM) for stainless steel components has proved useful in a variety of industries ranging from aerospace to biomedical engineering. Many of these components are subject to very high cycle fatigue (VHCF) loading and must have tailored mechanical properties to ensure failures do not occur before a service life is reached. Testing the fatigue strength AM materials exposed to VHCF loading is paramount to compare with the expected life cycles of their wrought counterparts. In this thesis, AM 17-4 precipitation hardened (PH) stainless steel (SS) were fabricated using laser powder bed fusion (L-PBF) technique, while the wrought 17-4 PH …

Far-Field Passive Wireless Sensors Composed Of Electroceramic Materials For Harsh Environment Applications, Kevin M. Tennant

Graduate Theses, Dissertations, and Problem Reports (ETD)

The demand for high temperature sensing technologies in industrial applications has been steadily increasing, driven by the need for precise monitoring and control in extreme environments. This thesis presents an investigation into the development and optimization of passive wireless sensors for high temperature sensing applications. The research focuses on overcoming the challenges associated with traditional sensing methods by leveraging passive wireless sensor technology, offering advantages such as reduced complexity, improved reliability, and enhanced flexibility.

A passive wireless high temperature sensor for far-field applications was developed for stable temperature sensing up to 1000 °C. The goal is to leverage the properties …

Data-Driven Modeling Of Oxygen Kinetics In La0.6sr0.4co0.2fe0.8o3−Δ (Lscf) For High-Temperature Reduction Of Co2 In An Electrolysis Cell, Ferron Campbell

Graduate Theses, Dissertations, and Problem Reports (ETD)

Electrolysis systems are critical to several societal applications, particularly energy storage and conversion. Developing these systems requires a detailed knowledge of the chemistry and thermodynamics of the materials used in the electrolysis cell. This work focuses on using embedded scientific machine learning as an efficient way to build an interpretable model for the reaction and transport kinetics in the LSCF electrode, whose performance directly influences the electrolysis system’s performance. The models developed in this study are trained using the publicly available machine learning package, FoKL-GP. This package incorporates a robust Gibbs sampler that employs a forward variable selection process to …

Laser Deposition Additive Manufacturing Of Multi-Material And Metal-Ceramic Composite Structures, Manikanta Grandhi

Graduate Theses, Dissertations, and Problem Reports (ETD)

The increasing performance requirements of modern industrial systems, coupled with the imperative for decarbonization, necessitate a fundamental rethinking of metallic component design and manufacturing. Traditional materials, with their inherent limitations in property optimization, susceptibility to degradation, and weight constraints, are proving insufficient. Multi-material joining offers a potential solution, enabling designers to strategically integrate diverse materials with specific, tailored properties into single component. Functionally graded materials (FGMs) and oxide dispersion strengthened (ODS) materials are prime examples of this approach, delivering substantial improvements in wear resistance, thermal regulation, high-temperature resilience, and overall weight efficiency. However, conventional manufacturing approaches further exacerbate the limitations …

Machine Learning-Assisted Multiscale Simulation And Design Optimization Of Composite Jackets Under Low-Velocity Impacts, Masoud Mohammadi

Graduate Theses, Dissertations, and Problem Reports (ETD)

This research presents the development of a data-driven machine learning-assisted approach to simulate and optimize the design of composite materials subjected to low-velocity impacts. It focuses on a specific type of hybrid composite comprised of fiberglass and Kevlar fabrics stitched with Kevlar threads. The study begins by creating a multiscale finite element simulation for the composite under a low-velocity impact, which operates across three scales: microscale, mesoscale, and macroscale. This simulation accepts various inputs, such as different layer configurations and orientations, and provides impact outputs including maximum load and energy absorption capacity and displacement at failure.

Python and MATLAB scripts …

Development And Testing Of High Strength Scalable High Entropy Alloys, Hans Jakob Pommerenke

Doctoral Dissertations

"High entropy alloys have shown promise through their ability to be tailored to specific scenarios. From highly corrosive environments to precipitation strengthened alloys to radiation environments high entropy alloys allow tailor made alloys for every solution. New compositions are developed and tested but little work focuses on the processing effect choosing rather than using processing as a steppingstone to achieve properties without investigating the processing effects. This work focuses on single phase face-centered cubic alloys strengthened by processing and precipitation strengthening. In conjunction with the development of these alloys, the ability to scale production will be investigated and characterized to …

The Development Of Hard Materials And Fibrous Monolith Composites For Friction Stir Welding, Paul Michael Brune

Doctoral Dissertations

"This research focuses on the development of hard materials and fibrous monolith composites for the purpose of adding to current friction stir welding tool technology. Well studied hard material systems, such as WC-Co, were incorporated and evaluated as cell materials for fibrous monolith composites with ductile cell boundaries of Co, W, and Mo. The indentation behavior of the WC-Co and WC-Co-cBN composites indicated possible crack deflection at the cell/cell boundary interface. Cylindrical pin friction stir welding tools were developed for each of the three fibrous monolith material systems. Welding was achieved on AA1100 aluminum, 260 brass, and AISI 1018 steel …

Investigating The Role Of Tesserae In Energy Absorption In Shark Cartilage, Molly Dobrow

UNF Graduate Theses and Dissertations

Unlike mammals, shark endoskeletons are composed of cartilage, which is less stiff compared to bone. Despite this structural disadvantage, sharks have risen to become apex predators, with reported maximum posterior bite force estimates approximating 5914 N in bull sharks. Shark jaws are estimated to undergo high cycle loading within the organism’s lifecycle without evidence of failure. Fatigue resistance may relate to mineral distribution within a component of the endoskeletal system – tesserae. Tesserae are thin, roughly hexagonal tiles composed of calcium phosphate hydroxyapatite (HA) crystals and grow by accretion to eventually surround the hyaline cartilage core. Though tesserae dimensions are …

Process, Structure, & Property Investigation Of Gallium-Based Metallic Alloys Processed At Room Temperature, Jennifer E. Ruliffson

UNF Graduate Theses and Dissertations

Metallic and intermetallic alloys are important in engineering, necessitating a thorough comprehension of their structure, processing, and properties. Amalgams are a class of alloy which are synthesized by various methods to produce diverse properties. Gallium-based amalgams, particularly gallium eutectic alloys, have low melting points, which allow for applications in dentistry and temperature sensitive electronics. This thesis investigates the process-structure-property relationships of gallium-based amalgams mixed with copper. Phases, microstructure, and diffusion processes are investigated using XRD and SEM. Adhesion strength and thermal properties are then correlated to these as well as process steps. This study contributes to advancing the understanding and …

Processing Of Niti Sma For High Reflectivity Applications, Nicholas Dean Asbury

UNF Graduate Theses and Dissertations

Nickel Titanium (NiTi) is a shape memory alloy (SMA) that is capable of being deformed and subsequently returned to the original shape through heating. This unique property makes NiTi a prime material for potential applications in the aerospace industry. As manufacturing capabilities advance, the ability to produce and implement advanced materials, such as shape memory alloys like NiTi, becomes more feasible. One such application being studied is deployable mirrors for imaging satellites. Reflector and mirror surfaces for imaging in the visible and infra-red range of the light spectrum require low surface roughness across the largest allowable area for the collection …

Assessment Of Defect Generation Mechanism In Welding Processes Using Phased Array Ultrasonic Testing (Paut), Caleb D. Williams

Honors College Theses

Welding is one of the major and most commonly used methods of material joining in industries around the world. The mechanisms of welding include complicated processes which can cause significant alteration in final properties and quality of the weld compared to the base materials. Due to these physical and chemical processes during the welding processes, defects and flaws can be generated. Observing such flaws over the years, leads engineers and researchers to investigate the methodologies to identify the cause and effect of defects and their effect on the quality of the welds. A better understanding of such parameters helps to …

A Novel Magnetorheological Pump Concept For Insulin Delivery, Mohammad Towhidul Islam Rimon

College of Graduate Studies: Theses & Dissertations

Over the past 25 years, awareness of type 1 diabetes has significantly increased, leading to a comprehensive understanding of various aspects, including its genetics, epidemiology, and disease burden. According to the Type 1 Diabetic Index, about 8.7 million people around the world live with this long-term autoimmune disease characterized by insulin deficiency and resultant hyperglycemia. However, the increased availability and utilization of artificial pancreas systems could potentially save 673,000 lives by 2040. Although, the advancement of diabetes technology offers Type 1 diabetic patients more tools to enhance glycemic management and achieve effective outcomes, many patients are still hesitant to adopt …