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Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam 2019 Indian Institute of Technology Bombay

Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam

Duane D. Johnson

Magnesium silicides are favorable thermoelectric materials considering resource abundance and cost. Chromium (Cr) doping in magnesium silicides has not yet been explored. Using first-principles calculations, we have studied the stability of Mg2Si with chromium (1.85, 3.7, 5.55, and 6.25% Cr) and tin (12.5 and 50% Sn). Three Mg2Si compounds doped with Sn, (Sn + Bi), and (Sn + Bi + Cr) are used to explain doping effects on thermoelectric performance. Notably, Cr behaves nonmagnetically for ≤2%Cr, after which ferromagnetic ordering is favored (≤12.96% Cr), despite its elemental antiferromagnetic state. With alloying of Sn (70.4%), Mg2Si ...


Fabrication Of High-Resolution Graphene-Based Flexible Electronics Via Polymer Casting, Metin Uz, Kyle Jackson, Maxsam S. Donta, Juhyung Jung, Matthew T. Lentner, John A. Hondred, Jonathan C. Claussen, Surya K. Mallapragada 2019 Iowa State University

Fabrication Of High-Resolution Graphene-Based Flexible Electronics Via Polymer Casting, Metin Uz, Kyle Jackson, Maxsam S. Donta, Juhyung Jung, Matthew T. Lentner, John A. Hondred, Jonathan C. Claussen, Surya K. Mallapragada

Chemical and Biological Engineering Publications

In this study, a novel method based on the transfer of graphene patterns from a rigid or flexible substrate onto a polymeric film surface via solvent casting was developed. The method involves the creation of predetermined graphene patterns on the substrate, casting a polymer solution, and directly transferring the graphene patterns from the substrate to the surface of the target polymer film via a peeling-off method. The feature sizes of the graphene patterns on the final film can vary from a few micrometers (as low as 5 µm) to few millimeters range. This process, applied at room temperature, eliminates the ...


Thermal Efficiency Of Steel Melting, Kent D. Peaslee, Semen Naumovich Lekakh, Bradley Randall 2019 Missouri University of Science and Technology

Thermal Efficiency Of Steel Melting, Kent D. Peaslee, Semen Naumovich Lekakh, Bradley Randall

Simon N. (Semen Naumovich) Lekakh

This paper presents the results of energy consumption measurements at steel foundries using induction and/or electric arc furnace melting. Statistical methods, infrared thermography, and numerical investigations were used for analysis of heat losses. The influence of different melting practices on energy losses was examined. Industrial experiments in isothermal holding of liquid steel in induction furnaces under different power inputs were used for evaluation of the real values of heat losses by radiation from liquid steel and conductivity through lining. Average values and statistical distributions of energy consumptions for melting steel are presented in this article.


Improving Melting Efficiency Through The Application Of New Refractory Materials, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Todd P. Sander, Jeffrey D. Smith, Mangesh Vibhandik 2019 Missouri University of Science and Technology

Improving Melting Efficiency Through The Application Of New Refractory Materials, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Todd P. Sander, Jeffrey D. Smith, Mangesh Vibhandik

Simon N. (Semen Naumovich) Lekakh

Ladle design and ladle practices have a significant effect on a foundry operation and product quality. Large steel temperature losses or instabilities in the pouring temperature are frequently compensated by tapping at higher temperatures dramatically increasing furnace and ladle lining wear, oxidation of the steel, alloying element losses, and energy consumption in steel melting. Ladle lining materials need to satisfy a complex array of often conflicting requirements. For example, ceramic materials for linings must possess a high strength at liquid steel temperatures to prevent erosion and crack formation. However, linings need to also have a low thermal conductivity which typically ...


Increasing Energy Efficiency Through Improvements In Ladle Materials And Practices, Kent D. Peaslee, Semen Naumovich Lekakh, Jeffrey D. Smith, Mangesh Vibhandik 2019 Missouri University of Science and Technology

Increasing Energy Efficiency Through Improvements In Ladle Materials And Practices, Kent D. Peaslee, Semen Naumovich Lekakh, Jeffrey D. Smith, Mangesh Vibhandik

Simon N. (Semen Naumovich) Lekakh

Steel foundry ladle practices play an important role in total energy efficiency of melting as well as influence casting quality. Extensive heat losses in the ladle could be associated with excessive superheating of the melt before tap which increases energy consumption, promotes oxidation of the melt and increases refractory consumption. A high cooling rate of the liquid metal in the ladle could also cause casting quality instability. The overall ladle heat balance and components of heat losses were analyzed using FLUENT and FACTSAGE software and validated with experimental data from both the UMR foundry and industrial foundries. The purpose of ...


Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh 2019 Missouri University of Science and Technology

Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh

Simon N. (Semen Naumovich) Lekakh

The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundry. The steel was followed from electric arc furnace melting through ladle refining to final casting. Timed sampling was performed at all stages of the process. Samples were analyzed using an automated SEM/EDS system. The overall evolution of oxide inclusions in terms of nucleation, growth, and flotation during liquid processing was studied using area fraction and average diameter. Chemical composition evolution was observed using a joint ternary plotting tool developed under this program. It was found that the use of zirconium as an addition for ...


Improvements In Steel Melting Efficiency -- Industrial Trials, Kent D. Peaslee, Semen Naumovich Lekakh, Edith Martinez 2019 Missouri University of Science and Technology

Improvements In Steel Melting Efficiency -- Industrial Trials, Kent D. Peaslee, Semen Naumovich Lekakh, Edith Martinez

Simon N. (Semen Naumovich) Lekakh

Industrial trials were completed to improve energy efficiency in steel melting. First, the benefits of increased chemical energy from an oxyfuel burner and a Co-Jet system in a basic 20 ton electric arc furnace (EAF) were studied. Observations and measurements were made during production before and after the installation of the two systems. The additional chemical energy improved energy efficiency and resulted in increased production. In addition, production using a basic EAF practice was compared to the traditional acid EAF practice. Second, an industrial trial using a 750 lb ladle with a combination of a lightweight alumina castable refractory and ...


Efficiency In Steel Melting: Opportunities And Progress, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Jay Triplett 2019 Missouri University of Science and Technology

Efficiency In Steel Melting: Opportunities And Progress, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Jay Triplett

Simon N. (Semen Naumovich) Lekakh

This paper summarizes the findings from a study of melting efficiency in steel foundries and provides examples of material and energy savings from improvements in technology and melting practices. This study is based on information gathered at 19 Steel Founders Society of America member foundries and includes a combination of historical data and industrial measurements by the research team. Information and data were collected on the type of melting equipment, melting practices, energy use and ladle practices. The data was statistically analyzed using STATGRAPHICS commercial software. A multiple regression analysis allowed evaluation of the influence of the melting furnace (type ...


Efficiency In Steel Melting: Ladle Development, Kent D. Peaslee, Semen Naumovich Lekakh, Todd P. Sander, Jeffrey D. Smith 2019 Missouri University of Science and Technology

Efficiency In Steel Melting: Ladle Development, Kent D. Peaslee, Semen Naumovich Lekakh, Todd P. Sander, Jeffrey D. Smith

Simon N. (Semen Naumovich) Lekakh

Effective ladle design and use is important for steel casting production. In foundry operations, the ladle temperature of the liquid steel is typically 150 to 250°F above the steel's melting point to compensate for the heat losses in small ladles and the associated high cooling rates from the large surface area to volume ratios. Higher superheat is also necessary to provide sufficient steel fluidity to properly fill the mold cavity. In spite of the relatively short time that the steel is in contact with the ladle lining, the huge thermal gradients in the lining drive high values of ...


Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang 2019 Missouri University of Science and Technology

Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang

Simon N. (Semen Naumovich) Lekakh

This paper summarizes results of industrial experiments investigating the introduction of supplemental chemical energy in Electric Arc Furnaces (EAF). Specifically, this research evaluates the effects of adding 0.4-0.6% of the scrap charge weight as SiC (10 lbs per scrap ton charged) in the EAF. SiC additions increase the available exothermic reactions during oxygen boiling in an attempt to reduce the electrical energy requirements. Results from 180 trial heats at two different steel foundries are highlighted and statistically evaluated. In both cases, the SiC additions had a measurable effect on decreasing the electrical energy consumption.


Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark C. Emmendorfer, Brenton Hrebec 2019 Missouri University of Science and Technology

Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark C. Emmendorfer, Brenton Hrebec

Simon N. (Semen Naumovich) Lekakh

Solidification macrostructure is of great importance for the properties and the quality of castings made from austenitic grade stainless steels (ASS) because there are limited options to change as-cast macrostructure in the solid condition. A typical cast macrostructure of ASS has a fine surface chilled zone followed by an elongated dendrite zone, columnar to equiaxed transition (CET) zone, and centrally located equiaxed crystals. Several castings from ASS were produced to determine the effects of casting geometry, chilling, and grain refinement on CET. The transient thermal field in solidified heavy castings was simulated and used to determine an isotherm velocity (V ...


Alloy Recovery And Control In Steel Melting, Kent D. Peaslee, Darryl S. Webber, Semen Naumovich Lekakh, Bradley Randall 2019 Missouri University of Science and Technology

Alloy Recovery And Control In Steel Melting, Kent D. Peaslee, Darryl S. Webber, Semen Naumovich Lekakh, Bradley Randall

Simon N. (Semen Naumovich) Lekakh

Alloy recovery plays an important role in steel melting economics because the cost of alloying additives such as ferroalloys and pure non-ferrous metals is significantly higher than the cost of steel scrap. Recovery of alloying additives also influences the reproducibility of steel properties from heat to heat. This paper reviews alloy recovery and final chemistry distributions at seven steel foundries and preliminary laboratory studies of alloy dissolution in ladles. Melting and alloy practices were observed for several plant trial heats in each of the foundries. Alloying and chemistry data were collected for an additional 20 - 155 heats at each plant ...


Super-Strong Materials For Temperatures Exceeding 2000 ⁰C, Laura Silvestroni, Hans Joachim Kleebe, William Fahrenholtz, Jeremy Lee Watts 2019 Missouri University of Science and Technology

Super-Strong Materials For Temperatures Exceeding 2000 ⁰C, Laura Silvestroni, Hans Joachim Kleebe, William Fahrenholtz, Jeremy Lee Watts

Jeremy Watts

Ceramics based on group IV-V transition metal borides and carbides possess melting points above 3000⁰C, are ablation resistant and are, therefore, candidates for the design of components of next generation space vehicles, rocket nozzle inserts, and nose cones or leading edges for hypersonic aerospace vehicles. As such, they will have to bear high thermo-mechanical loads, which makes strength at high temperature of great importance. While testing of these materials above 2000⁰C is necessary to prove their capabilities at anticipated operating temperatures, literature reports are quite limited. Reported strength values for zirconium diboride (ZrB2) ceramics can exceed 1 GPa at ...


Development And Characterization Of Tungsten Carbide Based Composites, Jeremy Lee Watts 2019 Missouri University of Science and Technology

Development And Characterization Of Tungsten Carbide Based Composites, Jeremy Lee Watts

Jeremy Watts

"The mining industry currently uses tri-cone, or roller cone bits to drill blast holes. Bit inserts used in these drill heads are predominantly manufactured from either cemented carbides or steels. The cemented carbides afford high hardness along with good wear resistance; however they have a low fracture toughness which can result in catastrophic failure. Steels, while exhibiting a much higher fracture toughness, have a low hardness which results in poor wear resistance. A material which could combine high hardness, good wear resistance, and high fracture toughness would represent a leap forward over today’s technology. Research being performed at the ...


Stress Measurement And Development Of Zirconium Diboride-Silicon Carbide Ceramics, Jeremy Lee Watts 2019 Missouri University of Science and Technology

Stress Measurement And Development Of Zirconium Diboride-Silicon Carbide Ceramics, Jeremy Lee Watts

Jeremy Watts

"Research presented in this dissertation focused on the production of ZrB₂-SiC composites and their characterization; in particular their mechanical properties and thermally generated residual stresses. Thermally generated stresses were measured using Raman spectroscopy as well as both neutron and x-ray diffraction. For 70 vol% ZrB₂ - 30 vol% SiC composites neutron diffraction revealed that the SiC phase was under ~880 MPa compressive stress and the ZrB₂ phase was under ~450 MPa tension at room temperature. It was also discovered that stresses began to accumulate at ~1400 ⁰C upon cooling from the processing temperature (1900 ⁰C -2000 ⁰C). Raman spectroscopy and x-ray ...


Degeneracy Of The 1/8 Plateau And Antiferromagnetic Phases In The Shastry-Sutherland Magnet Tmb4, Jennifer Trinh, Sreemanta Mitra, Christos Panagopoulos, Tai Kong, Paul C. Canfield, Arthur P. Ramirez 2019 University of California, Santa Cruz

Degeneracy Of The 1/8 Plateau And Antiferromagnetic Phases In The Shastry-Sutherland Magnet Tmb4, Jennifer Trinh, Sreemanta Mitra, Christos Panagopoulos, Tai Kong, Paul C. Canfield, Arthur P. Ramirez

Paul C. Canfield

The 1/8 fractional plateau phase (1/8 FPP) in Shastry-Sutherland lattice (SSL) spin systems has been viewed an exemplar of emergence on an Archimedean lattice. Here we explore this phase in the Ising magnet TmB4 using high-resolution specific heat (C) and magnetization (M) in the field-temperature plane. We show that the 1/8 FPP is smoothly connected to the antiferromagnetic phase on ramping the field from H=0. Thus, the 1/8 FPP is not a distinct thermodynamic ground state of TmB4. The implication of these results for Heisenberg spins on the SSL is discussed.


Pairing Toroidal And Magnetic Dipole Resonances In Elliptic Dielectric Rod Metasurfaces For Reconfigurable Wavefront Manipulation In Reflection, Odysseas Tsilipakos, Anna C. Tasolamprou, Thomas Koschny, Maria Kafesaki, Eleftherios N. Economou, Paul C. Canfield, Costas M. Soukoulis 2019 Institute of Electronic Structure and Laser, FORTH

Pairing Toroidal And Magnetic Dipole Resonances In Elliptic Dielectric Rod Metasurfaces For Reconfigurable Wavefront Manipulation In Reflection, Odysseas Tsilipakos, Anna C. Tasolamprou, Thomas Koschny, Maria Kafesaki, Eleftherios N. Economou, Paul C. Canfield, Costas M. Soukoulis

Paul C. Canfield

A novel approach for reconfigurable wavefront manipulation with gradient metasurfaces based on permittivity‐modulated elliptic dielectric rods is proposed. It is shown that the required 2π phase span in the local electromagnetic response of the metasurface can be achieved by pairing the lowest magnetic dipole Mie resonance with a toroidal dipole Mie resonance, instead of using the lowest two Mie resonances corresponding to fundamental electric and magnetic dipole resonances as customarily exercised. This approach allows for the precise matching of both the resonance frequencies and quality factors. Moreover, the accurate matching is preserved if the rod permittivity is varied, allowing ...


Collapse Of The Kondo State And Ferromagnetic Quantum Phase Transition In Ybfe 2zn 20, Udhara S. Kaluarachchi, Li Xiang, Jianjun Ying, Tai Kong, Viktor Struzhkin, Alexander Gavriliuk, Sergey L. Bud’ko, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Collapse Of The Kondo State And Ferromagnetic Quantum Phase Transition In Ybfe 2zn 20, Udhara S. Kaluarachchi, Li Xiang, Jianjun Ying, Tai Kong, Viktor Struzhkin, Alexander Gavriliuk, Sergey L. Bud’Ko, Paul C. Canfield

Paul C. Canfield

We present the electrical resistivity data under application of pressures up to ∼26 GPa and down to 50 mK on YbFe2Zn20. We find a pressure induced magnetic phase transition with an onset at pc=18.2±0.8 GPa. At ambient pressure, YbFe2Zn20 manifests a heavy fermion, nonmagnetic ground state and the Fermi liquid behavior at low temperatures. As pressure is increased, the power law exponent in resistivity, n, deviates significantly from Fermi liquid behavior and tends to saturate with n=1 near pc. A pronounced resistivity maximum Tmax, which scales with the Kondo temperature, is observed. Tmax decreases with ...


Optical Properties And Mechanical Modeling Of Acetylated Transparent Wood Composite Laminates, Kyle E. O. Foster, Kristen Hess, Garret M. Miyake PhD, Wil V. Srubar PhD 2019 University of Colorado Boulder

Optical Properties And Mechanical Modeling Of Acetylated Transparent Wood Composite Laminates, Kyle E. O. Foster, Kristen Hess, Garret M. Miyake Phd, Wil V. Srubar Phd

University Libraries Open Access Fund Supported Publications

Transparent wood composites (TWCs) are a new class of light-transmitting wood-based materials composed of a delignified wood template that is infiltrated with a refractive- index-matched polymer resin. Recent research has focused primarily on the fabrication and characterization of single-ply TWCs. However, multi-ply composite laminates are of interest due to the mechanical advantages they impart compared to the single ply. In this work, 1- and 2-ply [0 ◦ /90 ◦ ] TWC laminates were fabricated using a delignified wood template (C) and an acetylated delignified wood template (AC). The optical and mechanical properties of resultant C and AC TWC laminates were determined using ultraviolet-visible ...


Ambient Synthesis Of Nanomaterials By In Situ Heterogeneous Metal/Ligand Reactions, Boyce S. Chang, Brijith Thomas, Jiahao Chen, Ian D. Tevis, Paul Karanja, Simge Çınar, Amrit Venkatesh, Aaron Rossini, Martin M. Thuo 2019 Iowa State University and Ames Laboratory

Ambient Synthesis Of Nanomaterials By In Situ Heterogeneous Metal/Ligand Reactions, Boyce S. Chang, Brijith Thomas, Jiahao Chen, Ian D. Tevis, Paul Karanja, Simge Çınar, Amrit Venkatesh, Aaron Rossini, Martin M. Thuo

Ames Laboratory Accepted Manuscripts

Coordination polymers are ideal synthons in creating high aspect ratio nanostructures, however, conventional synthetic methods are often restricted to batch-wise and costly processes. Herein, we demonstrate a non-traditional, frugal approach to synthesize 1D coordination polymers by in situ etching of zerovalent metal particle precursors. This procedure is denoted as the heterogeneous metal/ligand reaction and was demonstrated on Group 13 metals as a proof of concept. Simple carboxylic acids supply the etchant protons and ligands for metal ions (conjugate base) in a 1 : 1 ratio. This scalable reaction produces a 1D polymer that assembles into high-aspect ratio ‘nanobeams’. We demonstrate ...


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