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Materials Science and Engineering Faculty Research & Creative Works
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Articles 1 - 23 of 23
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Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Materials Science and Engineering Faculty Research & Creative Works
The ac conductivity of CaCu₃Ti₄O₁₂ ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.
Microstructural Modification Of As-Cast Al-Si-Mg Alloy By Friction Stir Processing, Z. Y. Ma, S. R. Sharma, Rajiv S. Mishra
Microstructural Modification Of As-Cast Al-Si-Mg Alloy By Friction Stir Processing, Z. Y. Ma, S. R. Sharma, Rajiv S. Mishra
Materials Science and Engineering Faculty Research & Creative Works
Friction stir processing (FSP) has been applied to cast aluminum alloy A356 plates to enhance the mechanical properties through microstructural refinement and homogenization. the effect of tool geometry and FSP parameters on resultant microstructure and mechanical properties was investigated. the FSP broke up and dispersed the coarse acicular Si particles creating a uniform distribution of Si particles in the aluminum matrix with significant microstructural refinement. Further, FSP healed the casting porosity. These microstructural changes led to a significant improvement in both strength and ductility. Higher tool rotation rate was the most effective parameter to refine coarse Si particles, heal the …
Humidification Factors From Laboratory Studies Of Fresh Smoke From Biomass Fuels, D. E. Day, J. L. Hand, C. M. Carrico, Guenter Engling, W. C. Malm
Humidification Factors From Laboratory Studies Of Fresh Smoke From Biomass Fuels, D. E. Day, J. L. Hand, C. M. Carrico, Guenter Engling, W. C. Malm
Materials Science and Engineering Faculty Research & Creative Works
Measurements of smoke aerosol humidification factors were performed in a laboratory for different biomass fuel types and burn conditions. Two nephelometers simultaneously measured dry and humidified light scattering coefficients (bsp(dry) and bsp(RH), respectively), providing the first observations of the temporal evolution of the humidification factor (f(RH) = bsp(RH)/bsp(dry)) for fresh (minutes-old) smoke. Hygroscopic characteristics of the smoke aerosols varied with fuel type and fire conditions, with the mean f(RH) ranging from 1.01 to 1.95 for fresh minutes-old smoke for the relative humidity (RH) range of 70-94%. These f(RH) values exhibited temporal variability, with some fuels alternating from hygroscopic to nonhygroscopic …
Effect Of Friction Stir Processing On The Microstructure Of Cast A356 Aluminum, Z. Y. Ma, S. R. Sharma, Rajiv S. Mishra
Effect Of Friction Stir Processing On The Microstructure Of Cast A356 Aluminum, Z. Y. Ma, S. R. Sharma, Rajiv S. Mishra
Materials Science and Engineering Faculty Research & Creative Works
Friction stir processing (FSP) was applied to cast A356 Al to modify the as-cast microstructure. FSP homogenizes and refines the cast microstructure, completely eliminates porosity, and creates a microstructure with fine Si particles (0.25-0.42 μm) distributed in a fine grain aluminum matrix (3-4 μm). Further, FSP parameters significantly influence microstructural development in the processed zone of cast A356 Al. Generally, higher tool rotation rate creates a more homogeneous microstructure. at lower tool rotation rates, a macroscopically visible banded structure characterized by a low density of coarse particles, was detected in the nugget zone. However, FSP parameters did not significantly influence …
Composite (La, Sr)Mno3-Ysz Cathode For Sofc, Toshio Suzuki, Masanobu Awano, Piotr Jasinski, Vladimir Petrovsky, Harlan U. Anderson
Composite (La, Sr)Mno3-Ysz Cathode For Sofc, Toshio Suzuki, Masanobu Awano, Piotr Jasinski, Vladimir Petrovsky, Harlan U. Anderson
Materials Science and Engineering Faculty Research & Creative Works
(La, Sr) MnO3 (LSM)-Y doped ZrO2 (YSZ) composite was prepared using YSZ colloidal suspension (initial YSZ particle size ∼100 nm), YSZ and LSM polymer precursors on dense substrates at 800 °C annealing temperature. the results of a symmetrical LSM-YSZ composite cell test showed the area specific resistance for overpotential of 0.14 Ω cm2 at 800 °C, which indicated that the LSM-YSZ composite could be a potential candidate for cathode in SOFCs. the performance of the cell with the LSM-YSZ composite cathode and Ni-YSZ anode was investigated and the power density of about 0.26 W cm- 2 was obtained …
Mössbauer And Epr Spectra For Glasses And Glass-Ceramics Prepared From Simulated Compositions Of Lunar And Martian Soils, C. S. Ray, Signo Tadeu Dos Reis, W. M. Pontuschka, J. B. Yang, F. F. Sene, J. M. Giehl, Chang-Soo Kim, S. Sen
Mössbauer And Epr Spectra For Glasses And Glass-Ceramics Prepared From Simulated Compositions Of Lunar And Martian Soils, C. S. Ray, Signo Tadeu Dos Reis, W. M. Pontuschka, J. B. Yang, F. F. Sene, J. M. Giehl, Chang-Soo Kim, S. Sen
Materials Science and Engineering Faculty Research & Creative Works
In situ resource processing and utilization on planetary bodies is an important and integral part of NASA's space exploration program. within this scope and context, our general effort is primarily aimed at developing glass and glass-ceramic type materials using Lunar and Martian soils and exploring various application potentials of these materials for planetary surface operations. This paper reports the successful preparation of glasses from the melts of simulated composition of Lunar and Martian soils, and thermal and structural characterization using differential thermal analysis (DTA), Mössbauer and electron paramagnetic resonance (EPR) spectroscopy. Glass-ceramic materials were developed from these glasses using selective …
Freeze-Spray Processing Of Layered Ceramic Composites, Qiang Fu, Oratai Jongprateep, Ashlee Abbott, Fatih Dogan
Freeze-Spray Processing Of Layered Ceramic Composites, Qiang Fu, Oratai Jongprateep, Ashlee Abbott, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
Thermal gradients and associated stresses are critical in designing with ceramic composites having low thermal conductivity. In order to reduce the stresses from thermal gradients, compositional gradients are employed in designing of composite structures. This study addresses development of freeze-spray process to fabricate layered ceramic structures with controlled layer thickness and microstructural development. The composites were processed by spraying of ceramic slurries with low binder content and relatively high solids loadings (up to 40 vol%) on a cooled substrate. The frozen parts were freeze-dried and sintered at elevated temperatures. The relationship between microstructural development and thermal expansion behavior of Al …
Method For Fabricating Nanostructured Solid Oxide Fuel Cells And Cell Components, Harlan U. Anderson, X.-D. Zhou, Wayne Huebner
Method For Fabricating Nanostructured Solid Oxide Fuel Cells And Cell Components, Harlan U. Anderson, X.-D. Zhou, Wayne Huebner
Materials Science and Engineering Faculty Research & Creative Works
A method of fabricating a nanostructured solid oxide fuel cell includes dispersing ceria and doped ceria nanoparticles in a first colloidal solution, atomizing the first colloidal solution into a spray, depositing the spray onto a substrate to form a thin film electrolyte, dispersing a nanocomposite powder including ceria and CuO in the first solution, forming a second colloidal solution, atomizing the second colloidal solution into a second spray, and depositing the second spray over the thin film electrolyte as an interfacial layer.
Method Of Preparing A Solid Oxide Fuel Cell, Greg Hilmas, Dustin Beeaff
Method Of Preparing A Solid Oxide Fuel Cell, Greg Hilmas, Dustin Beeaff
Materials Science and Engineering Faculty Research & Creative Works
A solid oxide fuel cell having a multichannel electrode architecture and method for preparing the same, the method including forming a first carbon laden composition, including a first thermoplastic binder, into a rod, applying a first zirconia laden composition, including a second thermoplastic binder, onto the rod to form a composite feed rod, extruding the composite feed rod to form a controlled geometry filament, bundling the extruded composite feed rod to form a multicellular feed rod, extruding the multicellular feed rod to form a multicellular rod, cutting the multicellular rod into multicellular discs, applying a zirconia laden material to one …
Inelastic Deformation Behavior Of La0.6sr0.4feo3 Perovskite, Nina Orlovskaya, Harlan U. Anderson, Mykola Brodnikovskyy, Mykola Lugovy, Michael John Reece
Inelastic Deformation Behavior Of La0.6sr0.4feo3 Perovskite, Nina Orlovskaya, Harlan U. Anderson, Mykola Brodnikovskyy, Mykola Lugovy, Michael John Reece
Materials Science and Engineering Faculty Research & Creative Works
Inelastic deformation behavior of the rhombohedral La0.6Sr0.4FeO3 perovskite is reported. Such behavior is very similar to the ferroelastic deformation of LaCoO3 or lead zirconate titanate perovskites, except that no twin structure was found to exist in La0.6Sr0.4FeO3. the possible mechanisms responsible for such nonlinear deformation behavior are discussed. © 2006 American Institute of Physics.
Dielectric Constant Of Particles Determined By Impedance Spectroscopy, Vladimir Petrovsky, Abhishek Manohar, Fatih Dogan
Dielectric Constant Of Particles Determined By Impedance Spectroscopy, Vladimir Petrovsky, Abhishek Manohar, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
Electrical characterization of slurries prepared by mixing dielectric powders with solvents can be used to estimate dielectric properties of the particles. In particular, dielectric constant of the particles can be calculated from effective dielectric constant of the slurry measured at high frequency by using the Lorentz-Lorenz or similar equations based on mixing rules. Unfortunately, this approach leads to high margin of errors in dielectric constant estimation and is very sensitive to any slurry nonidealities such as sedimentation or agglomeration of particles. Impedance spectroscopy techniques are introduced to measure dielectric properties of particles at different frequency ranges. Dielectric constant of strontium …
Simulations Of A New Continuous Steelmaking Process, Jorg Annie Peter, Kent D. Peaslee, D. G. C. Robertson
Simulations Of A New Continuous Steelmaking Process, Jorg Annie Peter, Kent D. Peaslee, D. G. C. Robertson
Materials Science and Engineering Faculty Research & Creative Works
A new continuous steelmaking process has been designed in an effort to reduce meltshop costs and increase productivity beyond the possibilities of current EAF-LMF-CC meltshops. This paper discusses possible operational performance based on industrially-verified kinetic, thermodynamic, and heat-transfer models. Dynamic simulations predict variations in steel chemistry and temperature, resulting from steel treatment and upsets. Savings in costs are projected because of increased metallic yield, lower energy requirements, more efficient use of deoxidants and alloys, fewer man-hours per ton, and decreased capital investment.
Method For Preparation Of Nanometer Cerium-Based Oxide Particles, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson
Method For Preparation Of Nanometer Cerium-Based Oxide Particles, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson
Materials Science and Engineering Faculty Research & Creative Works
The invention comprises novel undoped and doped nanometer-scale CeO2 particles as well as a novel semi-batch reactor method for directly synthesizing the novel particles at room temperature. The powders exhibited a surface area of approximately 170 m2/g with a particle size of about 3-5 nm, and are formed of single crystal particles that are of uniform size and shape. The particles’ surface area could be decreased down to 5 m2/g, which corresponds to a particle size of 100 nm, by thermal annealing at temperatures up to 1000° C. Control over the particle size, size distribution …
The Phase Stability Of Cerium Species In Aqueous Systems Iii. The Ce(Iii/Iv)-H2o-H2o2/O2 System Dimeric Ce(Iv) Species, Pu Yu, Thomas J. O'Keefe
The Phase Stability Of Cerium Species In Aqueous Systems Iii. The Ce(Iii/Iv)-H2o-H2o2/O2 System Dimeric Ce(Iv) Species, Pu Yu, Thomas J. O'Keefe
Materials Science and Engineering Faculty Research & Creative Works
Equilibria and thermodynamic data for cerium dimer species were calculated for both the Ce-H2O-O2 and Ce-H2O-H2O2 systems. It was found that Ce (IV) has a tendency to form dimers, especially when the total cerium concentration is higher than 0.001 M. There are three major soluble dimer forms considered in this paper: (CeOCe)6+,(CeOCe)(OH)5+, and (CeOCe)(OH)24+, all having very similar standard potentials (E0 Ce(IV)dimer/Ce(III)01.66∀0.02V). When they coexist in solution, the concentration ratio of the Ce (IV) dimer to Ce3+ depends on the total cerium concentrations, the …
Large Scale Growth And Magnetic Properties Of Fe And Fe₃O₄ Nanowires, Jinbo Yang, H. Xu, Shaoxin You, X.-D. Zhou, C. S. Wang, William B. Yelon, William Joseph James
Large Scale Growth And Magnetic Properties Of Fe And Fe₃O₄ Nanowires, Jinbo Yang, H. Xu, Shaoxin You, X.-D. Zhou, C. S. Wang, William B. Yelon, William Joseph James
Materials Science and Engineering Faculty Research & Creative Works
Fe and Fe3O4 nanowires have been synthesized by thermal decomposition of Fe(CO)5, followed by heat treatments. The Fe wires are formed through the aggregation of nanoparticles generated by decomposition of Fe(CO)5. A core-shell structure with an iron oxide shell and Fe core is observed for the as-prepared Fe wires. Annealing in air leads to the formation of Fe2O3/Fe3O4 wires, which after heat treatment in a N2/alcohol atmosphere form Fe3O4 wires with a sharp Verwey [Nature (London) 144, 327 (1939)] transition at 125 K. The Fe3O4 wires have coercivities of 261 and 735 Oe along the wire axis at RT and …
Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang
Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang
Materials Science and Engineering Faculty Research & Creative Works
Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x < 0.4. Mixed valent Mn cations and cation vacancies, therefore, exist in all the samples. The samples with x > 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x < 0.3 the structure is rhombohedral and magnetically disordered above 16 K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.
Redox Stable Electrodes For Hydrogen Producing Solid Oxide Electrolyzer, Yong Wook Sin, Vladimir Petrovsky, Harlan U. Anderson
Redox Stable Electrodes For Hydrogen Producing Solid Oxide Electrolyzer, Yong Wook Sin, Vladimir Petrovsky, Harlan U. Anderson
Materials Science and Engineering Faculty Research & Creative Works
This report focuses on a study which measured the electrical conductivity of LSCrM, LSCr and LSM as a function of oxygen activity and temperature to evaluate the chemical and mechanical stability of the materials as an electrode in a solid oxide fuel-fed electrolyzer cell (SOFEC). the LSCrM symmetrical cell was fabricated using La0.75Sr0.25Cr0.5Mn0.5O3 (LSCrM) powder and evaluated using electrical conductivity, impedance spectroscopy, current density and power density as a function of temperature. during the evaluation, symmetrical cell tests and fuel cell tests were performed as a function of temperature. Silver (Ag) …
Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon
Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon
Materials Science and Engineering Faculty Research & Creative Works
The crystal structure of LiNH2 was reinvestigated using powder neutron diffraction with high sensitivity. The compound crystallizes in the tetragonal space group I4 with lattice parameters α = b= 5.034 42 (24) Å, c = 10.255 58 (52) Å. It is found that H atoms occupy 8g1(0.2429, 0.1285, 0.1910) and 8g2 (0.3840, 0.3512, 0.1278) sites. The bond lengths between the nearest nitrogen and hydrogen atoms are 0.986 and 0.942 Å, respectively. The bond angle between H-N-H is about 99.97°. These results are significantly different from those of previous experiments. The electronic structure was calculated according to the revised structural …
Vibration Testing Of Repaired Lead-Tin/Lead-Free Solder Joints, Matthew O'Keefe, S. Vetter, D. Murry, J. Smith, P. Amick, Martin G. Perez, D. W. Kleine, Richard S. Colfax
Vibration Testing Of Repaired Lead-Tin/Lead-Free Solder Joints, Matthew O'Keefe, S. Vetter, D. Murry, J. Smith, P. Amick, Martin G. Perez, D. W. Kleine, Richard S. Colfax
Materials Science and Engineering Faculty Research & Creative Works
No abstract provided.
Effect Of Welding Parameters On Properties Of 5052 Al Friction Stir Spot Welds, T. A. Freeney, S. R. Sharma, Rajiv S. Mishra
Effect Of Welding Parameters On Properties Of 5052 Al Friction Stir Spot Welds, T. A. Freeney, S. R. Sharma, Rajiv S. Mishra
Materials Science and Engineering Faculty Research & Creative Works
Effect of process parameters on friction stir spot welding (FSSW) of 5052 Al alloy has been evaluated. a plunge type FSSW machine was used for this study. Sheet thicknesses of 1 and 1.6mm were used. the tool rotation rate was varied between 1000 and 3000 rpm. the tool plunge rate and dwell time was varied to give weld cycle of 1-4 seconds. Shear tests were performed in 2 sheet and 3 sheet configurations to determine the influence of processing parameters on the mechanical properties of lap joint FSSWs. Higher joint strengths were observed at lower tool rotation rates. Copyright © …
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
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
Materials Science and Engineering Faculty Research & Creative Works
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 …
Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang
Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang
Materials Science and Engineering Faculty Research & Creative Works
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.
Effect Of Nozzle Base Material On The Rate Of Clogging During The Continuous Casting Of Aluminum-Killed Steels, Luis Trueba, Kent D. Peaslee, Jeffrey D. Smith, Musa Karakus
Effect Of Nozzle Base Material On The Rate Of Clogging During The Continuous Casting Of Aluminum-Killed Steels, Luis Trueba, Kent D. Peaslee, Jeffrey D. Smith, Musa Karakus
Materials Science and Engineering Faculty Research & Creative Works
One approach to solving the problem of nozzle clogging during the continuous casting of aluminum-killed steels is through careful selection of nozzle materials. in this study, the rate of clogging was measured while casting steel through simulated nozzles produced from alumina, zirconia, magnesia, zirconia-graphite, and alumina-graphite - three common base materials and two common carbon-containing nozzle materials. Spent nozzles were characterized using optical and cathodoluminescence microscopy. Interactions between the nozzles and steel were not observed in the alumina, zirconia, and zirconia-graphite nozzles. Slight interactions were observed in the magnesia nozzles as alumina inclusions within the steel interacted with the nozzle …