Engineering Commons^™

Machine Learning For Electronic Structure Prediction, Shashank Pathrudkar

Dissertations, Master's Theses and Master's Reports

Kohn-Sham density functional theory is the work horse of computational material science research. The core of Kohn-Sham density functional theory, the Kohn-Sham equations, output charge density, energy levels and wavefunctions. In principle, the electron density can be used to obtain several other properties of interest including total potential energy of the system, atomic forces, binding energies and electric constants. In this work we present machine learning models designed to bypass the Kohn-Sham equations by directly predicting electron density. Two distinct models were developed: one tailored to predict electron density for quasi one-dimensional materials under strain, while the other is applicable …

Sustainable Materials For Environment − Multifunctional Material Made From Dead Leaves And Nanostructured Materials For Antibiotic Degradation, Siyuan Fang

Dissertations, Master's Theses and Master's Reports

As environmental pollution from industrial processes and human activities continues to rise, finding efficient approaches to recycle waste materials and degrade persistent contaminants becomes increasingly critical. Dead leaves, an abundant but underutilized biomass, present an opportunity for creating value-added materials if their biocomponents can be preserved and transformed. Simultaneously, antibiotics such as tetracycline are widely found in water bodies but pose serious ecological and health risks, necessitating effective degradation methods. This dissertation addresses these challenges by leveraging natural and nanostructured materials to develop multifunctional products and advanced photocatalytic processes.

Chapter 3 of this dissertation addresses the challenge of converting waste …

Calculation Of Elastic Constants Of Bulk Metallic Glasses From Indentation Tests, Zhitong Xu, Ming Liu, Fuqian Yang

Chemical and Materials Engineering Faculty Publications

One of the challenges in the applications of instrumented indentation is to simultaneously measure elastic modulus and Poisson’s ratio of homogeneous, isotropic materials. This work proposes empirical equations for simultaneous calculation of elastic modulus and Poisson’s ratio of bulk metallic glasses (BMGs) from the ratio of the short diagonal length to the long diagonal length and the area of the Knoop imprint. The parameters pre- sented in the empirical equations are determined first by Knoop microhardness tests of 24 BMGs, whose elastic moduli and Poisson’s ratios are measured by resonant ultrasound spectroscopy. These empirical equations are further validated by the …

“Zero” Porosity High Loading Nmc622 Positive Electrodes For Li-Ion Batteries, Haidar Y. Alolaywi, Kubra Uzun, Yang-Tse Cheng

Chemical and Materials Engineering Faculty Publications

LiNi0.6 Mn0.2Co0.2 O 2 (NMC622) is a widely used positive electrode material for lithium-ion batteries, including electric vehicles. In this work, we investigated the effects of porosity, ranging from “zero” to the typical 35%, on the electrochemical behavior of high- loading NMC622 electrodes. Although it is well known that the energy density of the electrode increases with increasing areal capacity and decreasing porosity, NMC-positive electrodes with exceedingly low porosity (e.g., near zero) and high loading (e.g., 4 mAh cm−2 ) have not been investigated. Here, we report an intriguing observation that the “zero porosity” NMC electrode can have higher capacity …

Bioprinting With Adipose Stem Cells And Hydrogel Modified With Bioactive Glass, Krishna C.R. Kolan, Apurv Saxena, Bradley A. Bromet, Lesa B. Steen, August T. Bindbeutel, Julie A. Semon, Delbert E. Day, Ming C. Leu

Biological Sciences Faculty Research & Creative Works

Bioprinting research is focused on utilizing growth factors and multiple cell types to create clinically relevant three-dimensional (3D) tissue models using hydrogels. Rheological and biological challenges are two main factors that limit the creation of extrudable bioactive hydrogels. In this study, we investigate incorporation of fast dissolving and bioactive borate glass in different weight to volume percentages (0.075 to 0.6%) to alginate-gelatin (1:1) hydrogel to improve rheological properties and enable bioprinting with bioactive glass. The addition of glass improved the stiffness of the hydrogel. Human adipose-derived mesenchymal stem cells (ASCs) were uniformly mixed in this bioink at 1 x 106 …

Cf/Sic Ceramic Matrix Composites With Extraordinary Thermomechanical Properties Up To 2000 °C, Min Sung Park, Jian Gu, Heesoo Lee, Sea Hoon Lee, Lun Feng, William Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

The thermomechanical properties of carbon fiber reinforced silicon carbide ceramic matrix composites (Cf/SiC CMCs) were studied up to 2000 °C using high temperature in situ flexural testing in argon. The CMC specimens were fabricated using an ultrahigh concentration (66 vol%) aqueous slurry containing nano-sized silicon carbide powder. The SiC powder compacts were obtained by drying the slurry and were densified using the precursor impregnation and pyrolysis (PIP) method with field assisted sintering technology/spark plasma sintering (FAST/SPS). The high relative density of the SiC green body (77.6%) enabled densification within 2.5 days using four PIP cycles. In contrast, conventional PIP processes …

Thermodynamic Analysis Of Metal Segregation In Dual Phase High Entropy Ceramics, Steven M. Smith, William G. Fahrenholtz, Gregory E. Hilmas, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

Equilibrium Gibbs' free energy calculations were used to determine metal segregation trends between boride and carbide solid solutions containing two metals that are relevant to dual phase high entropy ceramics. The model predicted that Ti had the strongest tendency to segregate to the boride phase followed by Zr, Nb, Mo, V, Hf, and Ta, which matches experimental results of measured compositions. The ratio of a metal in the carbide phase to the content of the same metal in the corresponding metal boride had a linear trend with the change in standard Gibbs' free energy of reaction for a metal carbide …

Spark Plasma Sintering Of Magnesium Titanate Ceramics, Suzana Filipović, Nina Obradović, William G. Fahrenholtz, Steven Smith, Miljana Mirković, Adriana Peleš Tadić, Jovana Petrović, Antonije Đorđević

Materials Science and Engineering Faculty Research & Creative Works

Magnesium titanate ceramics were prepared by reactive spark plasma sintering (SPS) at 1200 °C for 5 min. Prior to sintering, MgO and TiO₂ powders were mixed by high energy ball milling (HEBM) for 15, 30, or 60 min. The effect of milling time on phase composition was analyzed by X-ray diffraction (XRD) for milled powders and sintered specimens. The morphology of the sintered ceramics was investigated by scanning electron microscopy (SEM), while elemental distribution was determined by energy dispersive spectroscopy (EDS). The presence of the MgTi2O5 phase was detected in XRD and was confirmed by EDS analysis. Microcracking was …

Morphology And Particle Size (Maps) Exercise: Testing The Applications Of Image Analysis And Morphology Descriptions For Nuclear Forensics, Stuart A. Dunn, Ian J. Schwerdt, David E. Meier, Naomi E. Marks, Thomas Shaw, Alexa Hanson, Kari Sentz, Meena Said, Richard A. Clark, Kyle A. Makovsky, Jason M. Lonergan, Matthew Gilbert

Materials Science and Engineering Faculty Research & Creative Works

Image analysis techniques have been applied and shown to be a valuable tool in nuclear forensics analysis. The interlaboratory exercise reported here has tested quantitative and qualitative approaches for characterizing nuclear materials. Particle size, surface features and morphology descriptions were compared by four laboratories on a common image set generated by Scanning Electron Microscopy and Digital Light Microscopy. Quantitative analysis of the image sets through the Morphological Analysis for Materials software highlighted the strength of image analysis, but also that the application of the software alone can introduce significant bias in the analysis. Qualitative morphology descriptions following the process outlined …

A Super-Hard High Entropy Boride Containing Hf, Mo, Ti, V, And W, Suzana Filipovic, Nina Obradovic, Greg E. Hilmas, William G. Fahrenholtz, Donald W. Brenner, Jon Paul Maria, Douglas E. Wolfe, Eva Zurek, Xiomara Campilongo, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

Super-Hard (Hf,Mo,Ti,V,W)B2 Was Synthesized by Boro-Carbothermal Reduction and Densified by Spark Plasma Sintering. This Composition Was Produced for the First Time as a Single-Phase Ceramic in the Present Research. the Optimized Ceramic Had a Single Hexagonal AlB2-Type Crystalline Phase with a Grain Size of 3.8 µm and Homogeneous Distribution of the Constituent Metals. the Vickers Hardness Exhibited the Indentation Size Effect, Increasing from 27 GPa at a Load of 9.8 N to as High as 66 GPa at a Load of 0.49 N. This is the Highest Hardness Reported to Date for High Entropy Boride Ceramics.

Phosphate-Based Dechlorination Of Electrorefiner Salt Waste Using A Phosphoric Acid Precursor, Paige Murray, Harmony Werth, Sean Sullivan, Brian J. Riley, Michael Simpson, Charmayne E. Lonergan, Krista Carlson

Materials Science and Engineering Faculty Research & Creative Works

Electrochemical processing of spent nuclear fuel in molten chloride salts results in radioactive salt waste. Chlorine removal from the salt has been identified as an effective and efficient first step in the management of high-level waste. In this work, a simple salt was dechlorinated with a phosphoric acid phosphate precursor, resulting in a glassy dechlorinated product. The dechlorination efficacy was evaluated in air and argon environments. This work serves as an initial step to advance the technological readiness level of h3po4-based dechlorination step toward implementation of iron phosphate waste forms to immobilize electrochemical fuel reprocessing salt waste streams.

Oxidation Of Additively Manufactured Zrb2–Sic In Air And In Co2 At 700–1000 °C, Marharyta Lakusta, Nicholas M. Timme, Abid H. Rafi, Jeremy Lee Watts, M. (Ming) C. (Chuan) Leu, Gregory E. Hilmas, William G. Fahrenholtz, David W. Lipke

Materials Science and Engineering Faculty Research & Creative Works

Oxidation behavior of additively manufactured zrb2–sic in air and in co2 is reported in the temperature range of 700–1000 °c. Observed scale morphologies in air and in co2 were similar, featuring an outer borosilicate layer and an inner porous zirconia layer containing partially oxidized silicon carbide particles and remnant borosilicate products. Oxide scale thicknesses and parabolic scaling constants in air were approximately twice those observed in co2 across all studied temperatures. Activation energies for oxidation of 140 ± 20 kj/mol in air and 110 ± 20 kj/mol in co2 were determined, indicating similar diffusion processes that appear to be rate-limiting. …

Thermal And Electrical Properties Of Single-Phase High Entropy Carbide Ceramics, Paul M. Brune, Gregory E. Hilmas, William G. Fahrenholtz, Jeremy Lee Watts, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

Thermal and Electrical Properties Were Investigated for Five Nominally Phase-Pure High Entropy Carbide Ceramics. the Compositions (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)C, (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C, (Hf0.2Mo0.2Ta0.2Ti0.2Zr0.2)C, (Hf0.2Ta0.2Ti0.2W0.2Zr0.2)C, and (Hf0.2Mo0.2Ti0.2W0.2Zr0.2)C Were Synthesized by Carbothermal Reduction of Oxides. the Thermal Diffusivity and Heat Capacity Were Measured from Room Temperature to 1800°C. the Room Temperature Thermal Conductivity Ranged from 5.1 W/mK for (Hf0.2Mo0.2Ti0.2W0.2Zr0.2)C to 9.0 W/mK for (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C. the Thermal Conductivity Increased over the Temperature Range with Maximum Conductivities of 19.6 W/mK Measured for (Hf0.2Mo0.2Ta0.2Ti0.2Zr0.2)C to 29.7 W/mK for (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C at 1800°C. the Electron Contribution to Thermal Conductivity Calculated from Measured Electrical Resistivity Varied from 41% to 52% of the …

High Temperature Oxidation Regime Transitions In Hafnium Carbide, Jonathan A. Scott, Xiaoqing He, David W. Lipke

Materials Science and Engineering Faculty Research & Creative Works

Understanding the oxidation behavior of hafnium carbide is crucial to its application in extreme environments. In this work, the transition in high-temperature oxidation kinetics regimes in hafnium carbide is explained based on phase equilibria considerations supported by observed changes in oxide scale microstructure evolution associated with different transformation pathways. Below, a composition-dependent critical temperature and oxygen pressure, hafnium carbide first transforms to an amorphous material with nominal composition HfO2C followed by phase separation into carbon and hafnia domains. Subsequently, gaseous transport through a nanometric pore network formed by oxidative removal of phase-separated carbon becomes rate-limiting. Above this critical point, the …

Optimized Gadolinium-Do3a Loading In Raft-Polymerized Copolymers For Superior Mr Imaging Of Aging Blood-Brain Barrier, Hunter A. Miller, Aaron Priester, Evan T. Curtis, Krista Hilmas, Ashleigh Abbott, Forrest M. Kievit, Anthony J. Convertine

Materials Science and Engineering Faculty Research & Creative Works

The development of gadolinium-based contrast agents (GBCAs) has been pivotal in advancing magnetic resonance imaging (MRI), offering enhanced soft tissue contrast without ionizing radiation exposure. Despite their widespread clinical use, the need for improved GBCAs has led to innovations in ligand chemistry and polymer science. We report a novel approach using methacrylate-functionalized DO3A ligands to synthesize a series of copolymers through direct reversible addition-fragmentation chain transfer (RAFT) polymerization. This technique enables precise control over the gadolinium content within the polymers, circumventing the need for subsequent conjugation and purification steps, and facilitates the addition of other components such as targeting ligands. …

Beneficiation Of Lunar Regolith Simulants Through Electrostatic Sieving And Magnetic Separation, Peter Bachle, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daoru Han

Materials Science and Engineering Faculty Research & Creative Works

In the light of future development of lunar structures, in-situ feldspar beneficiation is imperative for metal extraction. This research incorporates the tandem use of electrostatic sieving and magnetic separation for collecting a specific size range and mineral composition from lunar soil that optimizes subsequent chemical processing. While earlier works focused on silt-sized particles, this work expands that range up to medium-grained sand with a greater variety of potential lunar regolith compositions. This work shows that a 2.5 kV, 7 Hz to 30Hz frequency, single-phase square wave can lift silt and fine sand for collection. This lifting is successful directly from …

High-Temperature Oxidation Behavior Of High Entropy Carbide (Tanbtiv)C In Atmospheres With Different Oxygen Contents, Ruoyu Chen, Hongbin An, Jie Zhan, Saisai Li, Aiqin Mao, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (Nb_xTi_1-x)C_yO_2-y and oxides (Nb_0.5Ta_0.5)₂O₅, TiO₂, and Nb₂O₅. Importantly, the …

Strength Comparison For Fully Dense Zirconium Diboride Ceramics Tested By Different Methods, Darko Kosanović, Suzana Filipović, Isaak Trajković, Nina Obradović, Paul M. Brune, Gregory E. Hilmas, William G. Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

The strength of zirconium diboride ceramics was tested by three different methods, 3-point flexure, 4-point flexure, and compression. Nearly full-density ceramics were obtained by hot pressing commercial ZrB₂ powder with the addition of.5 wt.% carbon as a sintering aid. The thermal properties and hardness were studied for ZrB₂ milled with ZrB₂ and WC media. Based on phase purity and higher thermal conductivity, ZrB₂ ceramics prepared from powders milled with ZrB₂ media were selected for mechanical property studies. The strength in 3-point flexure was 546 ± 55 MPa. The flexure strength was 476 ± 41 MPa …

Kinetic Modeling Of Electrostatic Sieving For Lunar Regolith Beneficiation: Case Studies, Easton Ingram, Emmanuela Amen Eze, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daoru Han

Materials Science and Engineering Faculty Research & Creative Works

A new kinetic particle modeling framework was developed to investigate electrostatic transport of lunar regolith particles with applications to the concept of electrostatic sieving. The new approach is based on kinetic particle dynamics and includes major modules of sampling the particle size distribution, solving electric fields, and tracking motion of charged dust grains. Case studies for a concept of electrostatic sieving were chosen to validate the new model. The simulation achieved similar yields reported in previous works, which served as validation of the model. The new model is computationally efficient and could serve as a design, analysis, and optimization tool.

Synergistic Hardening In A Dual Phase High-Entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

A dual phase high-entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramic was synthesized using a single step boro-carbothermal reduction route. The synthesized powder was densified by spark plasma sintering at 2000°C, resulting in complete solid solution formation and a relative density of ≈99%. The dual phase ceramic was 43 vol% high-entropy carbide and 57 vol% high-entropy boride. The grain sizes were 0.85 ± 0.34 µm for the carbide and 0.87 ± 0.33 µm for the boride with minimal residual oxide (0.2 vol%) detected in the microstructure. The resulting composition had a higher microhardness than the individual boride and carbide ceramics across the range …

Effect Of Sc Spatial Distribution On The Electronic And Ferroelectric Properties Of Alscn, Bipin Bhattarai, Xiaoman Zhang, Wangwang Xu, Yijia Gu, W. J. Meng, Andrew C. Meng

Materials Science and Engineering Faculty Research & Creative Works

While aluminum scandium nitride based ferroelectric materials have shown significant promise for non-volatile memory applications, difficulties relating challenges in device performance, such as electrical leakage, to structural characteristics motivate improved understanding of the fundamental structure-property relationship. Spinodal decomposition has been reported in this material system, consistent with our observation of compositional segregation in AlScN films grown by reactive sputter epitaxy. To better understand the effects of spatially non-uniform Sc concentrations, the electronic and ferroelectric (FE) properties of AlScN as a function of Sc distribution are studied using density functional theory (DFT). We explore the impact of Sc-rich atomic planes in …

Effect Of Ph And Hydroxyapatite-Like Layer Formation On The Antibacterial Properties Of Borophosphate Bioactive Glass Incorporated Poly(Methyl Methacrylate) Bone Cement, Kara A. Hageman, Rebekah L. Blatt, William A. Kuenne, Richard K. Brow, Terence E. Mciff

Materials Science and Engineering Faculty Research & Creative Works

Infection is a leading cause of total joint arthroplasty failure. Current preventative measures incorporate antibiotics into the poly (methyl methacrylate) (PMMA) bone cement that anchors the implant into the natural bone. With bacterial resistance to antibiotics on the rise, the development of alternative antibacterial materials is crucial to mitigate infection. Borate bioactive glass, 13–93-B3, has been studied previously for use in orthopedic applications due to its ability to be incorporated into bone cements and other scaffolds, convert into hydroxyapatite (HA)-like layer, and enhance the osseointegration and antibacterial properties of the material. The purpose of this study is to better understand …

Development Of A Highly Loaded Zirconium Carbide Paste For Material Extrusion Additive Manufacturing, Clare Sabata, Austin J. Martin, Jeremy L. Watts, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

A highly loaded, aqueous-based zirconium carbide (ZrC) paste was developed for ceramic on-demand extrusion (CODE). Commercial ZrC powder was ball milled to reduce the particle size to ∼1 μm. Paste composition was determined by rheological characterization and observation of printing behavior; the final paste consisted of 46–47 vol% ZrC, 43.5 vol% distilled water, 8.1 vol% dispersant, and 1.6 vol% binder. Rheological characterization of the paste showed a yield stress of ∼8 Pa and shear thinning behavior (ΔG′/Δσ* = −55). The paste was printed using a 610 μm nozzle; a test print showed shape fidelity using the developed paste. A pressureless …

Impact Of Quenching Intensity Conditions On Using A Finite Element Model To Investigate The Microstructure And Hardenability Of Low-Alloy Steel, J. S. Alabi, E. Heidari, M. F. Buchely, K. Chandrashekhara, S. N. Lekakh, R. J. O'Malley, V. Athavale, A. Kumar

Materials Science and Engineering Faculty Research & Creative Works

Quenching is one of the primary processes to improve mechanical properties in steels, particularly hardness. Quenching is well established for different geometries of individually treated steel components; while in-steam quenching of large diameter continuously cast steel bar has several specific features which are difficult and costly to experimentally optimize. The end-quench Jominy test has been used extensively to study the hardenability of different steel grades. Different numerical, analytical, and empirical models have been developed to simulate the Jominy process and to understand quenching of steels. However, it is not straight forward to translate experimental data from Jominy test on instream …

Magnetic Separation Of Lunar Regolith Simulants With Applications To In Situ Resource Utilization On The Moon, Peter Bachle, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daoru Han

Materials Science and Engineering Faculty Research & Creative Works

The development of in situ resource utilization (ISRU) for metal extraction is imperative as a steppingstone for habitation construction in lunar and non-terrestrial environments. Separation of minerals by chemical composition is important to optimize metal and oxygen liberation from lunar ore. to this effect, devices capable of separating aluminum bearing minerals from iron-bearing minerals from the lunar regolith simulants have been developed. Twenty-eight different simulants have been used in this study. a dual-belt separator was designed to reduce middlings. Para-magnetic minerals were reliably separated using a neodymium N52-magnet-separator system. Effective separation of aluminum-bearing minerals from iron-bearing minerals was greater than …

Impact Of Quenching Intensity Conditions On Using A Finite Element Model To Investigate The Microstructure And Hardenability Of Low-Alloy Steel, J. S. Alabi, E. Heidari, M. F. Buchely, K. Chandrashekhara, S. N. Lekakh, R. J. O'Malley, V. Athavale, A. Kumar

Materials Science and Engineering Faculty Research & Creative Works

Quenching is one of the primary processes to improve mechanical properties in steels, particularly hardness. Quenching is well established for different geometries of individually treated steel components; while in-steam quenching of large diameter continuously cast steel bar has several specific features which are difficult and costly to experimentally optimize. the end-quench Jominy test has been used extensively to study the hardenability of different steel grades. Different numerical, analytical, and empirical models have been developed to simulate the Jominy process and to understand quenching of steels. However, it is not straight forward to translate experimental data from Jominy test on instream …

A Concept Of Producing Aluminum In-Situ On The Moon Through Molten Salt Electrolysis, Jacob N. Ortega, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daniel Stutts, Daoru Han

Materials Science and Engineering Faculty Research & Creative Works

This paper presents a concept of producing aluminum in-situ on the lunar surface, namely, the Lunar In-Situ Aluminum Production through Molten Salt Electrolysis (LISAP-MSE) method developed at Missouri University of Science and Technology. This paper aims to demonstrate the use of electro-deoxidation to reduce aluminum oxide (i.e., alumina) into aluminum and oxygen gas via electrolysis in a molten salt bath for the production of aluminum on the Moon. It is shown that with a steady supply of hydrogen chloride, this in-situ resource utilization (ISRU) method could supply several necessary materials consumed in the electro-deoxidation process except hydrogen chloride to produce …

Quantification Of Swelling In Hematite Pellets Reduced Using Hydrogen–Nitrogen Gas Mixture, Amogh Meshram, Yuri Korobeinikov, Xingwen Wei, Ronald J. O'Malley, Seetharaman Sridhar

Materials Science and Engineering Faculty Research & Creative Works

Iron ore pellets are reduced in a 50%H2–50%N2 1 atm gas mixture at 750, 800, 850, 900, and 950 °C while simultaneously documenting swelling (change in pellet radius) and weight change. Swelling increases with increasing temperature, with catastrophic swelling (>20% of reduction swelling index) observed at 850, 900, and 950 °C. As the pellet is reduced, the pellet radius increases until 40–50% reduction is achieved, followed by a decrease in diameter beyond 40–50% reduction at 750 and 850 °C. At 950 °C, the pellet radius continues to increase with additional pellet reduction without any subsequent decrease in diameter. Scanning …

Water Vapor Oxidation Of Sic Layer Of Tristructural Isotropic Particles, Visharad Jalan, Adam Bratten, Matthew Luebbe, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

Tri structural isotropic (TRISO) fuel particles, developed for use in high-temperature gas-cooled nuclear reactors, can be subjected to oxidizing environments in off-normal accident scenarios. In this study, surrogate TRISO fuel particles were oxidized at 1000–1350°C for 4 h in 20 kPa water vapor atmosphere balanced with ultrahigh-purity helium gas. The oxide scale morphology and thickness were studied via scanning electron microscopy, focused ion beam, and transmission electron microscopy. The oxide thickness increased as the oxidation temperature was increased. Although the oxide scale at 1000°C was completely amorphous, pockets of crystalline oxide were observed on particles oxidized at 1200 and 1300°C. …

Bipolar Hipims Kick-Pulse For High Hardness In High-Entropy Boride Thin Films, Nathaniel S. Mcilwaine, Nestor O.Marquez Rios, Eva Zurek, Donald W. Brenner, William G. Fahrenholtz, Stefano Curtarolo, Douglas E. Wolfe, Jon Paul Maria

Materials Science and Engineering Faculty Research & Creative Works

We report a microhardness indentation study for multicomponent refractory metal boride thin films that belong to the family of high-entropy ceramics exhibiting superior hardness and high temperature properties. We focus on the nominally equimolar composition (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2) B2, which we refer to as HEB3, on c-plane sapphire substrates. Thin films are prepared using bipolar high power impulse magnetron sputtering (HiPIMS), where the positive kick pulse is optimized to produce films with high density, high crystallinity, and a microstructure that is isometric in nature as revealed by cross-sectional fracture surface imaging, X-ray diffraction, and X-ray reflectometry. Low-load Knoop indentation is used to …