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Articles 31 - 60 of 75
Full-Text Articles in Ceramic Materials
Dielectric Properties Of Polycrystalline And Single-Crystal Magnesium Oxide At High Temperatures, Alan Devoe, Hung Trinh, Fatih Dogan
Dielectric Properties Of Polycrystalline And Single-Crystal Magnesium Oxide At High Temperatures, Alan Devoe, Hung Trinh, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
The electrical properties of high-purity magnesium oxide (MgO) samples sintered between 1500 and 1650°C were investigated up to 800°C. Dielectric constant, loss tangent and electrical conductivity were measured between 25 and 800°C. Optimum electrical properties were obtained for the sample sintered at 1600°C. The impurities in polycrystalline and single crystal MgO were discussed to understand their effect on electrical properties and the role of grain boundaries. Higher dielectric losses of polycrystalline samples as compared to the single crystal MgO were attributed to the presence of grain boundaries. MgO could be a useful dielectric material for capacitor applications up to 600°C.
Influence Of Environmental Barrier Coatings On The Overall Effectiveness Of A Film Cooled Ceramic Matrix Composite Plate, Shane P. Lindsay
Influence Of Environmental Barrier Coatings On The Overall Effectiveness Of A Film Cooled Ceramic Matrix Composite Plate, Shane P. Lindsay
Theses and Dissertations
Silicon carbide ceramic matrix composites, a promising new potential upgrade over the conventional metals currently used for jet engine turbine blades, have a propensity to oxidize in a combustion environment. Engine manufacturers often apply environmental barrier coatings to prevent the composites from oxidizing. What is unclear, however, is how environmental barrier coatings effect underlying composite temperatures. This research examined the coatings’ effects by first characterizing the influence of environmental barrier coatings on the underlying temperature of a protected ceramic, then evaluating the significance of lateral conduction for cooling a coated ceramic, and finally comparing cooling results for coated and uncoated …
A Priori Procedure To Establish Spinodal Decomposition In Alloys, Simon Divilov, Hagen Eckert, Cormac Toher, Rico Friedrich, Adam C. Zettel, Donald W. Brenner, William G. Fahrenholtz, Douglas E. Wolfe, Eva Zurek, Jon Paul Maria, Nico Hotz, Xiomara Campilongo, Stefano Curtarolo
A Priori Procedure To Establish Spinodal Decomposition In Alloys, Simon Divilov, Hagen Eckert, Cormac Toher, Rico Friedrich, Adam C. Zettel, Donald W. Brenner, William G. Fahrenholtz, Douglas E. Wolfe, Eva Zurek, Jon Paul Maria, Nico Hotz, Xiomara Campilongo, Stefano Curtarolo
Materials Science and Engineering Faculty Research & Creative Works
Spinodal decomposition can improve a number of essential properties in materials, especially hardness. Yet, the theoretical prediction of the onset of this phenomenon (e.g., temperature) and its microstructure (e.g., wavelength) often requires input parameters coming from costly and time-consuming experimental efforts, hindering rational materials optimization. Here, we present a procedure where such parameters are not derived from experiments. First, we calculate the spinodal temperature by modeling nucleation in the solid solution while approaching the spinode boundary. Then, we compute the spinodal wavelength self-consistently using a few reasonable approximations. Our results show remarkable agreement with experiments and, for NiRh, the calculated …
Degradation Of The Mechanical Properties And Hydrogen Generation In Cement Under Gamma Irradiation Assessed By Atomistic Simulation, Omar Al Najjar
Degradation Of The Mechanical Properties And Hydrogen Generation In Cement Under Gamma Irradiation Assessed By Atomistic Simulation, Omar Al Najjar
Theses and Dissertations
Although understanding the effect of the gamma-ray on cement-based materials is essential for many applications, such as the concrete contaminate of nuclear reactors or the storage of radioactive waste in cement-based waste forms, such understanding is still not fully developed. The importance of having such an understanding is becoming of utmost importance, especially with calls to extend the lifetime of nuclear power plants, and also due to some recent incidents of failures of the concrete structure in the nuclear fields. In this work, the details of preparing three molecular models as a representative structure of the main binding phase of …
Dielectric Properties Of Polycrystalline And Single Crystal (100) Strontium Titanate From 4 To 295 K, Hung Trinh, Alan Devoe, Fatih Dogan
Dielectric Properties Of Polycrystalline And Single Crystal (100) Strontium Titanate From 4 To 295 K, Hung Trinh, Alan Devoe, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
The dielectric properties of single crystal and polycrystalline SrTiO3 (ST) were investigated from 295 to 4 K. Relative permittivity (εr) and loss tangent (tan(δ)) were measured systematically as a function of direct current (DC) voltage (0 V/cm to 800 V/cm), frequency (100 Hz to 1 MHz), and temperature (295 K to 4 K) for type (100) single crystal SrTiO3 (SC-ST) and for polycrystalline SrTiO3 (PC-ST). Calculated equivalent series resistance (ESR) data are also reported. Overall, the permittivity of ST showed a dependence on temperature, DC voltage, and frequency. Dependences on voltage and frequency were only observed at …
Processing & Properties Of Zirconium Carbide Manufactured By Ceramic On-Demand Extrusion, Clare Sabata
Processing & Properties Of Zirconium Carbide Manufactured By Ceramic On-Demand Extrusion, Clare Sabata
Masters Theses
"This research focuses on the development of a zirconium carbide (ZrC) paste for use in material extrusion direct ink write additive manufacturing (AM) followed by the pressure less densification of ZrC and the mechanical and thermal characterization of the resulting ceramics. A highly loaded, aqueous paste was developed using commercial ZrC powder ball milled to ~1 μm. Optimal dispersant, binder, and solids loading were found by rheological characterization. The paste composition consisted of 46-47 vol% ZrC, 43.5 vol% distilled water, 8.1 vol% dispersant, and 1.6 vol% binder. A yield stress of ~8 Pa allowed for shape retention upon removal of …
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
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 …
Pressureless Sintering And Properties Of Additively Manufactured Zrb2–Sic, Marharyta Lakusta, Nicholas M. Timme, Jeremy L. Watts, William G. Fahrenholtz, Gregory E. Hilmas, David W. Lipke
Pressureless Sintering And Properties Of Additively Manufactured Zrb2–Sic, Marharyta Lakusta, Nicholas M. Timme, Jeremy L. Watts, William G. Fahrenholtz, Gregory E. Hilmas, David W. Lipke
Materials Science and Engineering Faculty Research & Creative Works
Densification behavior, grain growth kinetics, mechanical and thermal properties of pressurelessly sintered zirconium diboride–silicon carbide (ZrB2–SiC) fabricated by extrusion of high solids loading pastes have been studied. The effects of sintering temperature (1600–2300°C), heating rate during constant heating rate sintering (10–50°C/min), and time during isothermal sintering (3–24 h) on density and grain size were examined. The apparent activation energy for densification was determined to be 940 ± 90 kJ/mol, suggesting lattice diffusion as the dominant sintering mechanism. Grain growth of both ZrB2 and SiC followed a normal grain growth power law with grain growth exponent n = 2 indicating diffusion-controlled …
Phenolic Polymer Infiltration And Pyrolysis Process For Additively Manufactured Carbon/Peek Composites To Produce Carbon–Carbon Composites, S. Weiler, H. A. Haffner, K. Chandrashekhara, J. Watts, G. E. Hilmas, J. Bayldon, L. M. Rueschhoff
Phenolic Polymer Infiltration And Pyrolysis Process For Additively Manufactured Carbon/Peek Composites To Produce Carbon–Carbon Composites, S. Weiler, H. A. Haffner, K. Chandrashekhara, J. Watts, G. E. Hilmas, J. Bayldon, L. M. Rueschhoff
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Carbon–carbon composites are carbon fibers reinforced with carbon matrix and are classified as advanced materials well suited for high-temperature structural applications. Carbon–carbon composites are characterized by maintaining excellent mechanical properties and structural stability at high temperatures and have been used in aerospace application as nozzles, heatshields, and leading edge. However, conventional methods to manufacture carbon–carbon composites are costly and time-consuming. the aim of this work is to develop a method for creating additively manufactured (AM) carbon–carbon composites using a high-pressure re-infiltration process. in doing so, less infiltration cycles are required compared to a low-pressure re-infiltration, reducing the total manufacture time. …
Electrostatic Sorting Of Lunar Regolith Simulants For Sustainable Resource Utilization: Modeling And Characterization Of Particle Size Distribution, Abdullah Al Moinee, Peter Bachle, Kyle Newport, William Schonberg, David Bayless, Jeffrey Smith, Daoru Han, Fateme Rezaei
Electrostatic Sorting Of Lunar Regolith Simulants For Sustainable Resource Utilization: Modeling And Characterization Of Particle Size Distribution, Abdullah Al Moinee, Peter Bachle, Kyle Newport, William Schonberg, David Bayless, Jeffrey Smith, Daoru Han, Fateme Rezaei
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
In pursuit of sustainable resource utilization on the Moon, this paper delves into modeling and characterization of particle size distribution (PSD) of lunar regolith simulants in an electrostatic system. A prototype electrostatic sieve was built and tested with four sample simulants mirroring properties of lunar mare and highland regolith. An alternating four-phase (90 degrees, 180 degrees, 270 degrees, 360 degrees) traveling square-wave was utilized for particle-directed transport to model the diverse trajectories of the particles. Numerically, we scrutinized how the distribution functions of the particles are manifested as the electrostatic field propagates, with a focus on three distinct particle ranges …
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
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.
Progress Of Lisap-Mse: A Concept Of Producing Aluminum In-Situ On The Moon Through Molten Salt Electrolysis, Jacob N. Ortega, David Bayless, Daniel Stutts, Daoru Han, Todd P. Sander, Jeffrey Smith, Fateme Rezaei, William Schonberg
Progress Of Lisap-Mse: A Concept Of Producing Aluminum In-Situ On The Moon Through Molten Salt Electrolysis, Jacob N. Ortega, David Bayless, Daniel Stutts, Daoru Han, Todd P. Sander, Jeffrey Smith, Fateme Rezaei, William Schonberg
Mechanical and Aerospace 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 …
Ultra-Fast Annealing Improves Snr And Long-Term Stability Of A Highly Multiplexed Line-By-Line Fbg Array Inscribed By Femtosecond Laser In A Coreless Fiber For Extreme-Temperature Applications, Farhan Mumtaz, Bohong Zhang, Jeffrey D. Smith, Ronald J. O'Malley, Rex E. Gerald, Jie Huang
Ultra-Fast Annealing Improves Snr And Long-Term Stability Of A Highly Multiplexed Line-By-Line Fbg Array Inscribed By Femtosecond Laser In A Coreless Fiber For Extreme-Temperature Applications, Farhan Mumtaz, Bohong Zhang, Jeffrey D. Smith, Ronald J. O'Malley, Rex E. Gerald, Jie Huang
Electrical and Computer Engineering Faculty Research & Creative Works
This study reports the fabrication of an 4th-order line-by-line Fiber Bragg Gratings (FBG) array using femtosecond laser inscription within a highly multimode coreless optical fiber, with a particular focus on achieving substantial multiplexing capabilities. An ultra-fast annealing procedure is employed, resulting in an impressive enhancement of the FBG sensor's fringe visibility by approximately 13 dB, signifying a notable improvement of approximately ~4 dB. This substantial enhancement contributes to the long-term stability and performance of the multiplexed FBG array in extreme temperature conditions. The systematic fabrication approach employed for the multiplexed FBG array guarantees a high signal-to-noise ratio (SNR) for each …
Experimental Investigation Of A Viscoelastic Liner To Reduce Under Helmet Overpressures And Shock Wave Reflections, Cody J.H. Thomas, Fatih Dogan, Catherine E. Johnson
Experimental Investigation Of A Viscoelastic Liner To Reduce Under Helmet Overpressures And Shock Wave Reflections, Cody J.H. Thomas, Fatih Dogan, Catherine E. Johnson
Materials Science and Engineering Faculty Research & Creative Works
Introduction: Shock wave overpressure exposures can result in blast-induced traumatic brain injury (bTBI) in warfighters. Although combat helmets provide protection against blunt impacts, the protection against blast waves is limited due to the observed high overpressures occurring underneath the helmet. One route to enhance these helmets is by incorporating viscoelastic materials into the helmet designs, reducing pressures imposed on the head. This study aims to further investigate this mitigation technique against under-helmet overpressures by adding a viscoelastic liner to the inside of a combat helmet. Methods: The liner's effectiveness was evaluated by exposing it to free-field blasts of Composition C-4 …
Electrostatic Sorting Of Lunar Regolith Simulants For Sustainable Resource Utilization: Modeling And Characterization Of Particle Size Distribution, Abdullah Al Moinee, Peter Bachle, Kyle Newport, William Schonberg, David Bayless, Jeffrey Smith, Daoru Han, Fateme Rezaei
Electrostatic Sorting Of Lunar Regolith Simulants For Sustainable Resource Utilization: Modeling And Characterization Of Particle Size Distribution, Abdullah Al Moinee, Peter Bachle, Kyle Newport, William Schonberg, David Bayless, Jeffrey Smith, Daoru Han, Fateme Rezaei
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
In pursuit of sustainable resource utilization on the Moon, this paper delves into modeling and characterization of particle size distribution (PSD) of lunar regolith simulants in an electrostatic system. a prototype electrostatic sieve was built and tested with four sample simulants mirroring properties of lunar mare and highland regolith. an alternating four-phase (90 degrees, 180 degrees, 270 degrees, 360 degrees) traveling square-wave was utilized for particle-directed transport to model the diverse trajectories of the particles. Numerically, we scrutinized how the distribution functions of the particles are manifested as the electrostatic field propagates, with a focus on three distinct particle ranges …
Molecular Modeling Of Phenolic Resin For Carbon-Carbon Composites, Ivan Gallegos
Molecular Modeling Of Phenolic Resin For Carbon-Carbon Composites, Ivan Gallegos
Dissertations, Master's Theses and Master's Reports
One of the most difficult challenges associated with space exploration is terrestrial atmospheric reentry due to the high thermal loads generated. Carbon carbon (C/C) composites have been used as heat shielding materials due to their high strengthto- weight ratio and thermal properties and their applications include heat shielding for various high temperature environments. C/C composites are manufactured by polymer-infiltration pyrolysis (PIP) via cycles of curing and pyrolysis of a prepreg which can be costly and take up to several days. Thus, C/C composites ideal candidates for computationally-driven optimization techniques, such as a multiscale Integrated Computational Materials Engineering (ICME) approach, by …
Mechanisms Of Dendritic Shorting In Lithium Metal Batteries With Li7la3zr2o12 Solid Electrolytes, Lukas Karapin-Springorum
Mechanisms Of Dendritic Shorting In Lithium Metal Batteries With Li7la3zr2o12 Solid Electrolytes, Lukas Karapin-Springorum
Pomona Senior Theses
Energy storage will play a crucial role in efforts to mitigate the effects of climate change caused by greenhouse gas emissions from human activity. Lithium metal batteries using solid electrolytes like Li7La3Zr2O12 have higher energy density than lithium-ion batteries, which may enable a more rapid and complete electrification of transportation. However, lithium metal batteries suffer from undesirable short-circuiting when metallic lithium deposits connect the two electrodes. It has been debated whether these lithium dendrites generally grow directionally from the anode or are generated by the reduction of lithium ions inside the solid electrolyte, …
Calculation Of Elastic Constants Of Bulk Metallic Glasses From Indentation Tests, Zhitong Xu, Ming Liu, Fuqian Yang
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 …
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
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
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
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
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 …
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
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.
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
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
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 …
Beneficiation Of Lunar Regolith Simulants Through Electrostatic Sieving And Magnetic Separation, Peter Bachle, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daoru Han
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 …
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
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
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
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 …
Development Of A Highly Loaded Zirconium Carbide Paste For Material Extrusion Additive Manufacturing, Clare Sabata, Austin J. Martin, Jeremy L. Watts, Gregory E. Hilmas
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 …