Materials Science and Engineering Commons^™

Investigations In Hydrogen Ironmaking, Joseph William Govro

Doctoral Dissertations

The purpose of this research is to contribute to the Grid Interactive Steelmaking with Hydrogen (GISH) project. This research investigates the viability of both producing and melting Direct-Reduced Iron (DRI) utilizing hydrogen. Conventional CO reduced DRI will be referred to as “C-DRI” and DRI produced using hydrogen gas will be referred to as “H-DRI”.

An H-DRI pilot plant was constructed in Golden Colorado. The pilot plant was commissioned and successfully operated four campaigns. Process improvements were made throughout the campaigns and the process was optimized. In addition to running the pilot plant in a pure hydrogen condition, the pilot plant …

Zirconium Carbide Based Materials For Extreme Aerospace Environments, Nathaniel Hyman Blatt

Doctoral Dissertations

This research focuses on the processing and properties of zirconium carbide-based materials to promote their use in extreme environment aerospace applications, including nuclear thermal propulsion and hyper sonics. Several carbide systems including ZrC, ZrC-Mo cermets, (Zr, Nb)C, and a high entropy carbide were developed. The ZrC-Mo cermet was studied extensively to understand the effect of starting carbide grain size on the final microstructure, composition, elastic moduli, hardness, fracture toughness, room and elevated temperature flexural strength, thermal diffusivity, electrical resistivity, thermal expansion coefficient, and thermal conductivity. It was shown that heat transport in the cermets was dominated by the ZrC phase …

Critical Parameters Controlling Oxide Scale Formation And Hydro-Descaling Efficiency During Steelmaking, Tochukwu Princewill Ojiako

Doctoral Dissertations

In modern steelmaking, cast slabs are exposed to high-temperature oxidizing environments during secondary cooling, reheating, and hot rolling, resulting in the formation of multilayer oxide scales on the steel surface. These scales interact with mold-flux residues originating from the casting process (CC). The morphology, chemistry, and adhesion of oxide scale strongly influence its removability during high-pressure hydraulic descaling and ultimately determine the surface quality of hot-rolled products. However, the mechanistic relationship between oxide scale evolution, scale-steel interfacial structure, and hydraulic descaling performance remains poorly understood.

This dissertation investigates oxide scale formation, modification, and removal in low-carbon thin-slab steels produced by …

Strontium Titanate For Capacitor And Energy Storage Applications At Cryogenic Temperatures, Hung Trinh

Doctoral Dissertations

This study investigates the dielectric properties of single crystal and ceramic strontium titanate (SrTiO₃) for cryogenic capacitor applications from room temperature to 4 K. Permittivity (k) and loss tangent are dependent on temperature, frequency, mechanical stress, and applied DC electric field. Accordingly, the dielectric constant and loss tangent were measured at various frequencies and DC bias levels. Loss tangent data are also presented as equivalent series resistance (ESR). For single crystal SrTiO₃, an impurity level of ≈500 ppm barium resulted in an increase of the maximum permittivity to approximately 50,000 at 6 K. This relatively high …

Investigation Of Electrochemical Corrosion Fatigue Mitigation Strategies For Mild Carbon Steel, Joel Andrew Hudson

Doctoral Dissertations

Corrosion fatigue remains a critical durability challenge for steels used in boiler tubes and other safety-critical components, where the interaction of cyclic stresses and corrosive environments accelerates material degradation. This dissertation comprises three experimental studies aimed at advancing mitigation strategies and test methodologies: (1) enhancing corrosion resistance through electrodeposited Fe-Ni anodic coatings, (2) inducing synthetic crack closure to suppress fatigue crack growth, and (3) developing an accessible, low-cost, automated testing system to investigate environmentally assisted cracking (EAC) under controlled laboratory conditions. The first study examined the corrosion behavior of Fe and Fe-Ni electrodeposits synthesized from sulfate-based baths and applied to …

Solid-State Crystallization Of Zeolites And Their Use In Plastic Upcycling Applications, Yixin Liao

Doctoral Dissertations

Plastics have been an irreplaceable component of modern technology as well as everyday life. They have brought much convenience to us with their characteristics of great malleability, durability, and stability. The versatile and low-cost nature of plastics also enables their wide engagement in many modern industries including automobile, medical, communication as well as aerospace. Polyethylene (“PE”), made from polymerization of ethylene, is one of the most widely used plastics in the world. Being cheap, flexible, and long-lasting, they are extensively used in the packaging industry, especially for plastic bags and other sorts of containers. However, the durability of plastics, on …

Phase-Field Modeling Of Rapid Solidification Processes, Nima Najafizadeh

Doctoral Dissertations

"Many advanced manufacturing processes such as additive manufacturing utilize rapid solidification of alloys, as it enables the formation of exotic non-equilibrium microstructure and thus improved properties. However, the interrelationship between the processing parameters and the resulting microstructure in rapid solidification is yet to be fully understood. We aim to investigate the microstructure evolutions during the rapid solidifications using phase-field modeling. The phase-field method assumes a diffuse interface, which avoids tracking the moving interface and hence enables efficient numerical simulations for complex microstructure evolution. A phase-field model with coupled solute-thermal diffusion and solute trapping effect is developed to investigate the rapid …

The Structure, Properties And Dissolution Behaviors Of Phosphate Glasses, Han Zhang

Doctoral Dissertations

The poor chemical durability remains a critical challenge for the application of phosphate glasses. This study investigates the compositional influences on the structure, properties and chemical durability of Li2O-ZnO-P₂O₅ glasses. Their structural characteristics were analyzed utilizing high-performance liquid chromatography, Raman spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of (Li2O+ZnO) in LZeq glasses depolymerizes the phosphate network. In LZ40P and LZ45P glasses, Li⁺ initially replaces Zn²⁺ associated with non-bridging oxygens (NBOs) in Q² tetrahedra. Once the substitution in Q² is complete, further Li⁺ incorporation leads to the replacement of Zn²⁺ in Q^{1 …}

Development, Characterization And Testing Of Traditonal And Advanced Nuclear Fuel Cladding Materials, Joshua Eddy Rittenhouse

Doctoral Dissertations

Kanthal D and FeCrAl alloys in general, are prospective candidates as accident tolerant nuclear fuel cladding materials. The work presented herein focuses on applying two techniques of severe plastic deformation, equal channel angular pressing (ECAP) and high-pressure torsion (HPT), as means of grain refinement to improve irradiation resistance. Samples of as-received, ECAP, and HPT processed Kanthal D were exposed to neutron irradiation to a dose of 2 DPA at two different temperatures, 300 °C and 500 °C. Detailed characterization was performed including mechanical and microstructural, and several positive improvements with regards to irradiation resistance were identified in the ECAP and …

Investigating The Effects Of Fly Ash On The Properties Of Silica-Deficient High Alumina Materials, Sai Akshay Ponduru

Doctoral Dissertations

This research is made up of five studies mainly focused on attaining sustainability in high alumina cements like calcium aluminate cement (CAC) and calcium sulfoaluminate belite cements (CSAB) by partially replacing them with additives and supplementary cementitious materials (SCMs) like fly ash (FA). The first study focused on understanding the reaction kinetics of CAC and FA binders at different replacement levels (i.e. between 10%-to-50% by mass) and their effect on mechanical properties. It was also shown that the reactive nature of FAs can be determined by calculating a single parameter called number of constraints (nc) derived from topological constraint theory. …

Characterization And Deportment Of Anode Impurities In Copper Electrorefining, Charles Michael Campbell

Doctoral Dissertations

The objective of this research was to study the deportment of the group 15 elements, arsenic, antimony and bismuth during copper electrorefining. Samples were collected from six industrial copper anodes with different compositions. Specimens were physically characterized and electro refined to understand the differences in the behavior of selected impurities. Inclusions in the cast metal structures were characterized using automated scanning electron microscopy and energy dispersive spectroscopy to measure and correlate their size, shape and composition. Arsenic and lead were found to have a positive correlation between concentration and size of inclusions. Using wavelength dispersive spectroscopy, multiphase inclusions were examined, …

Optical Sensor Instrumentation For Enhanced Continuous Caster Development, Hanok Wondimagegnehu Tekle

Doctoral Dissertations

Fiber-optic sensors are an emerging technology that can enhance process monitoring and control in steelmaking. They are especially valuable in the continuous caster’s harsh environment. This dissertation presents the industrial application and demonstration of three sensor types: single-mode silica fiber with Rayleigh-based Optical Frequency Domain Reflectometry (OFDR), sapphire fiber (single-crystal alumina) with Fiber Bragg Gratings (sFBG), and an in-line Raman spectroscopy probe. Each sensor served a distinct role in the continuous caster. Rayleigh OFDR sensors were embedded in tundishes for distributed thermal mapping at 7-mm spatial resolution across ≈4 m. Measurements were taken during preheating, casting, and ladle exchanges, and …

Effect Of Thermomechanical Processing And Heat Treatment On The Microstructure And Mechanical Properties Of Ultra-High Strength Steels, Rogerio Antao Cardoso

Doctoral Dissertations

"A martensite-based and an austenite-based Fe-Mn-Al steels were investigated aiming the pilot-scale production of steels that meet military specifications for Rolled Homogeneous Armor (RHA) and High-hardness Armor (HHA) plates. Each material underwent specific thermomechanical processes and the following hardness, Charpy V-notch (CVN) impact toughness at -40 °C and room-temperature tensile properties were correlated with the resulting microstructures.

Specimens of the martensitic steel were austenitized at 1010 °C, quenched and tempered at 150, 175, 200, 225 and 250 °C for times up to four hours. As for the Fe-Mn-Al steel, its hot rolling schedule was design to promote strain accumulation in …

Processing And Densification Of Multi-Phase High-Entropy Ceramics, Steven Smith

Doctoral Dissertations

"This work focuses on the processing and densification of multiphase, high-entropy ceramics to promote their use in friction stir welding technologies. Several high-entropy systems including high-entropy borides, carbides, and their composites were produced. Boro/carbothermal and carbothermal synthesis were used to produce high-entropy powders from oxide powder mixtures. Composites of high-entropy borides and high-entropy carbides were produced using a sequential approach to produce both phases. The carbide was first produced using carbothermal reduction, then ZrH2 and B4C were added to the carbide powder to produce the high-entropy boride phase. The resulting powder was densified by spark plasma sintering and pressureless sintering, …

Raft-Based Polymer And Nanoparticle Materials For Traumatic Brain Injury Treatment And Diagnostics, Aaron Priester

Doctoral Dissertations

"Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Neurodegenerative diseases that develop post-TBI can be, in part, attributed to DNA and cell-damaging reactive oxygen species (ROS) and lipid peroxidation products (LPOx). This thesis focused on overcoming the limits of current TBI material treatment approaches by employing a RAFT (reversible-addition fragmentation chain transfer) polymer approach that incorporated novel therapeutic, diagnostic and peptide-targeting monomers. An improved nanoparticle synthesis approach was also developed. Thiol and thioether-containing monomers neutralize both ROS and LPOx while Gd-containing monomers with enhanced magnetic resonance imaging (MRI) contrast provide diagnostics and material tracking in …

Oxidation Behavior Of Silicon Carbide, Matrix Graphite, And Refractory Multi-Principal Element Alloy, Visharad Jalan

Doctoral Dissertations

"The present study focuses on the investigation of the oxidation behavior of silicon carbide, matrix graphite in a water vapor environment. It also examines the oxidation behavior of refractory multi-principal element alloys when exposed to air. The oxidation behavior of silicon carbide and matrix graphite were investigated in conditions pertaining to off-normal incidents in high-temperature gas-cooled nuclear reactors. Understanding this is crucial for the prediction of their performance in such accidents and ensuring that the nuclear reactor is accident tolerant. Upon exposure to water vapor, the two A3-based matrix graphite exhibited different behaviors. The A3-27 type showed oxidation in all …

Development And Testing Of Irradiation-Tolerant High-Entropy Alloys, Matthew John Luebbe

Doctoral Dissertations

"High entropy alloys (HEAs) are a novel class of alloys made of multiple principal elements in near equal proportions. They have been observed to possess an array of useful engineering properties, such as good ductility and fracture toughness, high temperature strength, oxidation and corrosion resistance and irradiation resistance. This makes them promising candidates for harsh environments, especially nuclear reactors. These properties could potentially realize advanced Gen IV nuclear reactor designs. However, most HEA compositions contain Co, which activates under irradiation, generating safety and waste management concerns. This work studies three compositions of Co-free HEAs whose strength and microstructures are evaluated …

Ceramic Dielectrics For High Temperature Capacitor Applications, Alan Daniel Devoe

Doctoral Dissertations

Technical progress in microelectronics is allowing operation in environments that were previously considered impossible. Building complete electronic circuits for applications above 450 degrees C, such as the planned NASA missions to Venus, require a variety of active and passive components, including multilayer ceramic capacitors (MLCC).

This study explores calcium zirconate CaZrO3 and magnesium oxide MgO based dielectric compositions for MLCC applications that are capable of operating at extreme temperatures between 450 degrees C and 600 degrees C. Both materials were characterized with respect to impurities, dopants, crystal structure and microstructural development. Dielectric properties were measured to determine permittivity, dissipation factor, …

Computational Design Of Complex Concentrated Alloys, Hamid Sharifi

Doctoral Dissertations

A high-throughput parameterization of modified embedded atom model (MEAM) interatomic potentials for combinations of Cu, Ti, Ni, Cr, Co, Al, Fe, and Mn was carried out using a genetic algorithm. Unary systems were parameterized based on DFT calculations and experimental results. MEAM potentials for 28 binary and 56 ternary combinations of the elements were parameterized to DFT results that were carried out with semi-automated frameworks. Specific attention was made to reproduce properties that impact compositional segregation, material strength, and mechanics. Utilizing the MEAM interatomic potentials and a Monte Carlo scheme, phase segregation in the CrNiCo, CuNiCr and CuNiCo fcc alloys …

In-Depth Characterization Of The Selective Oxidation Products Of Hafnium Carbide, Jonathan Allen Scott

Doctoral Dissertations

"Materials capable of withstanding oxidative environments at temperatures >2000°C are necessary for hypersonic applications. Hafnium carbide (HfC) shows a combination of properties that lends itself toward these applications; however, its oxidation behavior is poorly understood. At 1300°C, HfC was found to oxidize via the following mechanism: 1) Initial oxidation of both C and Hf present in the system, 2) Formation of an interconnected pore network, whose size is related to the volume of gases being generated during the oxidation process, 3) Growth of the oxide scale to become sufficiently protective, 4) Formation of an initially amorphous “HfO₂C” at …

Processing-Microstructure-Properties Relationships In Additively Manufactured Zrb2-Sic Ceramics, Marharyta Lakusta

Doctoral Dissertations

"The study explores the pressure less sintering (PS) and chemical compatibility of ZrB₂-30 vol.%SiC produced by additive manufacturing (AM) with CO₂. The oxidation kinetics and scale microstructures were compared for ZrB₂-SiC made by hot pressing (HP) and by AM coupled with PS. All specimens exhibited parabolic oxidation kinetics. The difference in oxidation behavior becomes evident at temperatures of 1100-1400°C (200-900h). Oxidation rates increased as grain size increased. Similar oxide scale morphologies were observed in both CO₂ and air, with an outer borosilicate layer and an inner porous ZrO₂ layer containing partially oxidized …

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 …

Atomistic-Informed And Machine Learning-Assisted Crystal Plasticity Modeling For Materials Interface, Ibrahim Altarabsheh

Doctoral Dissertations

This dissertation presents a comprehensive study that addresses two critical challenges in the field of computational materials science and engineering from nano- to mesoscale. First, to overcome the well-acknowledged length scale limitation associated with atomistic simulations, a novel two-step approach is introduced for a probabilistic prediction of stress-strain curves in terms of material volume. The method combines Molecular Dynamics (MD) simulations and a multioutput Gaussian process (MOGP) with Bayesian analysis to model stress-strain behavior and predict stress and strain values. The model effectively captures the intricate three-stage curve shape exhibited in stress-strain plots, discerning key points such as yielding, hardening, …

Intragranular Tungsten-Titanium Carbide Composite Ceramics Via Gas-Solid Displacement Reactions, Ryan Daniel Dempsey

Doctoral Dissertations

"Research presented herein details the synthesis and characterization of nanocomposite ceramics featuring novel heterogeneous microstructures of potential interest in a variety of electrical and structural applications. Specifically, W-TiCy composite ceramics featuring tungsten nanoprecipitates located primarily within TiCy grains have been produced via sintering of intragranular nanocomposite powders produced via reaction processing-based techniques. This dissertation details the thermodynamic basis and applied kinetics of a processing scheme for fabricating nanocomposite ceramics whose morphological heterogeneity reflects that originally developed in the powder state. The first study in this series overviews the motivation for applying metallothermic displacement reactions, conducted through gaseous intermediates, to solid …

Phosphate And Borophosphate Glasses For Optical And Biomedical Applications, Parker Tracy Freudenberger

Doctoral Dissertations

"The goal of this work was to connect the network structures of phosphate and borophosphate glasses to the compositional dependence of properties related to biomedical applications. The glasses were characterized by a variety of techniques, including phosphate ion chromatography, Raman spectroscopy, and ¹¹B and ³¹P Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy, which provide qualitative and quantitative information about the phosphate and borate moieties that constitute the network structures. The systematic addition of borate to a phosphate glass initially creates tetrahedral borate sites that replace P-O-P linkages with B-O-P linkages, and the properties of the resulting borophosphate glasses …

Effectiveness Of Clay Nanotube Blended Coating Materials For Thermal Insulation, Hawa Hashm

Doctoral Dissertations

Studies conducted by the U.S. Department of Energy reported that heating and cooling systems use nearly 60% of the total energy consumed in a building, while approximately 31% of that energy loss occurs through the improperly insulated floor, walls, and ceiling. Hot summers or severely cold weather can make these problems worse. The passing of conditioned air through these building materials is a substantial source of energy loss, which has driven significant investigation into new environmentally friendly, sustainable, and cost-effective solutions. The main objective of the research was to experimentally evaluate the thermal conductivity of paints blended with halloysite nanotubes …

Molten Steel Interactions With Tundish Linings And Refractory Glazes, Tyler Michael Richards

Doctoral Dissertations

"In the final stages of casting, molten steel is in contact with two main types of refractories: the working lining of the tundish used to serve as an intermediate vessel between the ladle and copper mold, and the various glazed carbon-bearing refractories used to control the flow of steel from the ladle to the tundish and from the tundish to the mold. If steel interacts with these refractories in such a way as to result in the formation of inclusions, it may be too late to remove them, leading to degradation of the steel’s mechanical properties. Understanding these interactions and …

Bulk Nanostructured Steels For Nuclear Reactor And Extreme Environment Applications, Maalavan Arivu

Doctoral Dissertations

"Candidate accident tolerant FeCrAl fuel (ATF) claddings for light water reactors (LWRs) need to be thinner than current Zircaloys owing to higher neutronic penalty, demanding an improvement in strength. Therefore, equal channel angular pressing (ECAP), and high-pressure torsion (HPT) were used to produce bulk ultra-fine grained and nanocrystalline Kanthal-D [KD; Fe-21Cr-5Al-0.026C (wt.%) alloy] which resulted in an improvement in strength of up to 3 times their nominal strength from grain boundary strengthening, and dislocation strengthening. Dynamic recovery was promoted due to ECAP at 520 oC rendering it with a large area fraction of less mobile low angle grain boundaries (LAGBs) …

Novel Ferromagnetic Materials With Improved Mechanical Performance, Wesley Alexander Everhart

Doctoral Dissertations

"The ductility of intermetallics has long been a hindrance to their broad adaptation despite a significant range of properties such as magnetic, half-metallic, and shape memory behavior. The lack of a general theory for the ductility of intermetallics along with the lack of prior art that experimentally measured mechanical properties drives the need for significant investment in many of these novel magnetic materials in order to even understand, let alone correct, poor ductility.

This dissertation includes work that explored the effect of vanadium content and quenching rate on the microstructure and ductility of Fe-Co alloys. Results indicated that a martensitic …