Influence Of Environmental Barrier Coatings On The Overall Effectiveness Of A Film Cooled Ceramic Matrix Composite Plate,
2024
Air Force Institute of Technology
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 …
Degradation Of The Mechanical Properties And Hydrogen Generation In Cement Under Gamma Irradiation Assessed By Atomistic Simulation,
2024
American University in Cairo
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,
2024
Missouri University of Science and Technology
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 …
Oxidation Of Additively Manufactured Zrb2–Sic In Air And In Co2 At 700–1000 °C,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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 …
Processing & Properties Of Zirconium Carbide Manufactured By Ceramic On-Demand Extrusion,
2024
Missouri University of Science and Technology
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 …
Bioprinting With Adipose Stem Cells And Hydrogel Modified With Bioactive Glass,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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.
Magnetic Separation Of Lunar Regolith Simulants With Applications To In Situ Resource Utilization On The Moon,
2024
Missouri University of Science and Technology
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 …
A Concept Of Producing Aluminum In-Situ On The Moon Through Molten Salt Electrolysis,
2024
Missouri University of Science and Technology
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 …
Kinetic Modeling Of Electrostatic Sieving For Lunar Regolith Beneficiation: Case Studies,
2024
Missouri University of Science and Technology
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.
Beneficiation Of Lunar Regolith Simulants Through Electrostatic Sieving And Magnetic Separation,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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 …
Synergistic Hardening In A Dual Phase High-Entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 Ultra-High Temperature Ceramic,
2024
Missouri University of Science and Technology
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,
2024
Missouri University of Science and Technology
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 …
Sic Addition To A Dual Phase High Entropy Ultra-High Temperature Ceramic,
2024
Missouri University of Science and Technology
Sic Addition To A Dual Phase High Entropy Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Kantesh Balani, Gregory E. Hilmas, Jeremy Watts
Materials Science and Engineering Faculty Research & Creative Works
Dual phase (Hf,Ta,Ti,W,Zr)B2-(Hf,Ta,Ti,W,Zr)C high entropy ultra-high temperature ceramics were processed from commercial diboride and carbide powders with and without SiC additions. A 30-min hold at a maximum temperature of 1850 °C in spark plasma sintering resulted in a relative density of ∼95 %, which increased to ∼100 % with the addition of 7.5 wt.% SiC. The compositions did not reach chemical equilibrium under the given sintering conditions resulting in an inhomogeneous distribution of transition metals in both the boride and carbide phases. The addition of SiC improved densification by inhibiting grain growth, which reduced the grain size from 9.0 ± …
Pressureless Sintering And Properties Of Additively Manufactured Zrb2–Sic,
2024
Missouri University of Science and Technology
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 …
