Nonlinear Optical Studies Of Defects And Domain Structures In Perovskite-Type Dielectric Ceramics, 2017 The Graduate Center, City University of New York
Nonlinear Optical Studies Of Defects And Domain Structures In Perovskite-Type Dielectric Ceramics, David J. Ascienzo
All Graduate Works by Year: Dissertations, Theses, and Capstone Projects
In order to improve future generations of dielectric capacitors a deeper understanding of voltage-induced dielectric breakdown and electrical energy storage limitations is required. This dissertation presents the use of far-field optical second harmonic generation (SHG) polarimetry for probing structural defects and polar domains in linear and nonlinear perovskite dielectric ceramics. We investigated the formation of electric field-induced structural distortions at pristine Fe-doped SrTiO3 (Fe:STO) electrode interfaces, structural defect and strain formation due to oxygen vacancy migration in electrodegraded Fe:STO single crystals, and mixed tetragonal and rhombohedral phase domains in ferroelectric Zr-doped BaTiO3 (BZT) films ...
Structure Evolution And Dielectric Behavior Of Polystyrene-Capped Barium Titanate Nanoparticles, 2017 Iowa State University
Structure Evolution And Dielectric Behavior Of Polystyrene-Capped Barium Titanate Nanoparticles, H.Z. Guo, Yaroslav Mudryk, M.I. Ahmad, X.C. Pang, L. Zhao, M. Akinc, Vitalij K. Pecharsky, Nicola Bowler, Z.Q. Lin, Xiaoli Tan
Polystyrene-capped barium titanate (BaTiO3) nanoparticles with sizes of 11 nm and 27 nm were prepared using amphiphilic star-like diblock copolymer templates. The crystal structure evolution of these nanoparticles over a wide temperature range (10-428 K) was investigated by powder X-ray diffraction. The Rietveld refinement indicates that the abrupt structural transitions observed in micron-sized powders become broad as particle size is reduced to a few tens of nanometers. The orthorhombic phase (Amm2) is observed in the range of 10-388 K, coexisting with the rhombohedral phase (R3c) at lower temperatures and with the tetragonal phase (P4mm) at higher temperatures. At room temperature ...
Silicon Carbide Materials Properties Selection For Mechanical Seal Faces, 2017 University of Tennessee, Knoxville
Silicon Carbide Materials Properties Selection For Mechanical Seal Faces, William Charles Hoskins
University of Tennessee Honors Thesis Projects
No abstract provided.
Production Of Fine Calcium Powders By Centrifugal Atomization With Rotating Quench Bath, 2017 Iowa State University
Production Of Fine Calcium Powders By Centrifugal Atomization With Rotating Quench Bath, Liang Tian, Iver E. Anderson, Trevor M. Riedemann, Alan M. Russell
Materials Science and Engineering Publications
Recently, a novel Al/Ca composite was produced by severe plastic deformation of Al powders and Ca granules for possible use as a high-voltage power transmission conductor. Since the strength of such composites is inversely proportional to the Ca filament size, fine Ca powders (less than ~ 250 μm) are needed to achieve the desired high strength for the powder metallurgy production of an Al-matrix composite reinforced by nano-scale Ca filaments. However, fine Ca powders are not commercially available. Therefore, we have developed a method to produce fine Ca powders via centrifugal atomization to supply Ca powder for prototype development of ...
Quality Improvement In Drilling Silicon By Using Micro Laser Assisted Drilling, 2017 Western Michigan University
Quality Improvement In Drilling Silicon By Using Micro Laser Assisted Drilling, Barkin Bakir
The Hilltop Review
The micro-laser assisted drilling (µ-LAD) of monocrystalline silicon (100), using a diamond cutting tool coupled with a laser, was tested in order to improve the cutting edge quality of a drilled samples. The laser beam is transmitted through an optically transparent diamond drill bit and focused precisely at the tool-workpiece interface, where the material is under high pressure induced by the diamond tool. The influence of the laser power on the quality and the inner surface finish of the drilled materials is investigated. Different laser powers were used to carry out the experiments. The experimental results indicated that the µ-LAD ...
Computational Studies Of Grain Boundary Behavior In Uranium Dioxide Nuclear Fuels, 2017 Westinghouse Electric Company LLC
Computational Studies Of Grain Boundary Behavior In Uranium Dioxide Nuclear Fuels, Eric Nelson, Lan Li (Mentor), Simon C. Middleburgh (Mentor)
Idaho Conference on Undergraduate Research
Nuclear power is responsible for the production of 380,000 Megawatts of energy worldwide, which results in over 11% of the world’s energy production [world-nuclear.org]. Pellet-cladding interactions (PCI) are a key nuclear fuel failure mechanism which presents formidable challenges to researchers due to extreme nuclear fission conditions. Although PCI interactions have been reduced due to fuel additives, understandings of PCI interactions remain elusive. We propose new approaches to increase understanding of nuclear fuel interactions; specifically, uranium dioxide and the effects of dopants. This study focuses on amorphous uranium dioxide and fission products, while benchmarking new methods with previous ...
Cermet Development For High Temperature And High Pressure Applications, 2017 Boise State University
Cermet Development For High Temperature And High Pressure Applications, Beatriz Justus Ferez, Samantha Guthrie, Brian J. Jaques (Mentor), Darryl P. Butt (Mentor)
Idaho Conference on Undergraduate Research
Many traditionally used low cost alloys are easily corroded in steam or supercritical CO2. An effective solution is to utilize ceramic heat exchangers that are often integrated with metallic components which result in a significant thermal expansion mismatch. The goal of this project is to develop a sealing method to create a hermetic joint between the ceramic and metal alloy. Proposed is a seal ring containing a cermet powder with a coefficient of thermal expansion (CTE) higher than the ceramic and metal to produce a high temperature compressive seal. Cermets of Ag and MgO have been selected to withstand ...
Verifying The Implementation Of An Anisotropic Grain Boundary Energy Model In Idaho National Lab’S Marmot, 2017 Brigham Young University Idaho
Verifying The Implementation Of An Anisotropic Grain Boundary Energy Model In Idaho National Lab’S Marmot, John-Michael H. Bradley, Evan D. Hansen, Jarin C. French, Yongfeng Zhang (Mentor)
Idaho Conference on Undergraduate Research
This work aims to verify the correct implementation of an anisotropic grain boundary (GB) energy model for face-centered cubic (FCC) and fluorite materials in Idaho National Laboratory’s phase field fuel performance code MARMOT. The model was recently implemented in MARMOT with the purpose of enabling higher fidelity simulations of UO2 nuclear fuels. As part of verification, tests were performed to measure the energy dependence on misorientation of high symmetry GBs in an FCC metal (Cu). The energies of the , , and  twist boundaries result as predicted, as do the energies of the  symmetric tilt boundaries ...
Deformation Processed Al/Ca Nano-Filamentary Composite Conductors For Hvdc Applications, 2017 Iowa State University
Deformation Processed Al/Ca Nano-Filamentary Composite Conductors For Hvdc Applications, Charles F. Czahor, Iver E. Anderson, Trevor M. Riedemann, Alan M. Russell
Materials Science and Engineering Conference Papers, Posters and Presentations
Efficient long-distance power transmission is necessary as the world continues to implement renewable energy sources, often sited in remote areas. Light, strong, high-conductivity materials are desirable for this application to reduce both construction and operational costs. In this study an Al/Ca (11.5% vol.) composite with nano-filamentary reinforcement was produced by powder metallurgy then extruded, swaged, and wire drawn to a maximum true strain of 12.7. The tensile strength increased exponentially as the filament size was reduced to the sub-micron level. In an effort to improve the conductor's ability to operate at elevated temperatures, the deformation-processed wires ...
Nonlinear Dielectric Behavior Of Field-Induced Antiferroelectric/Paraelectric-To-Ferroelectric Phase Transition For High Energy Density Capacitor Application, 2017 Michigan Technological University
Nonlinear Dielectric Behavior Of Field-Induced Antiferroelectric/Paraelectric-To-Ferroelectric Phase Transition For High Energy Density Capacitor Application, Mingyang Li
Dissertations, Master's Theses and Master's Reports
Electric field-induced antiferroelectric(AFE)/paraelectric(PE)-to-ferroelectric(FE) phase transitions are investigated for the associated nonlinear dielectric behavior, which could offer high dielectric capacity. The phenomenon in monolithic materials has been computed for Kittel antiferroelectric and BaTiO3 model systems using the Landau-Ginzburg-Devonshire theory. The general switching curves give values of the polarization as a function of external electric field. A similar computation is performed for particle-filled polymer-matrix composites where an internal depolarization field is considered. The polarization-electric field response changes with different depolarization factors, which demonstrate the shape and alignment of the dielectric particles embedded in polymer-matrix are key ...
Controlling Properties Of Agglomerates For Chemical Processes, 2017 Michigan Technological University
Controlling Properties Of Agglomerates For Chemical Processes, Joseph A. Halt
Dissertations, Master's Theses and Master's Reports
Iron ore pellets are hard spheres made from powdered ore and binders. Pellets are used to make iron, mainly in blast furnaces. Around the time that the pelletizing process was developed, starch was proposed as a binder because it’s viscous, adheres well to iron oxides, does not contaminate pellets and is relatively cheap. In practice, however, starch leads to weak pellets with rough surfaces – these increase the amount of dust generated within process equipment and during pellet shipping and handling. Thus, even though the usual binder (bentonite clay) contaminates pellets, pelletizers prefer it to starch or other organics.
Charge Transport In Electronic-Ionic Composites, 2017 University of Kentucky
Charge Transport In Electronic-Ionic Composites, Long Zhang
Theses and Dissertations--Chemical and Materials Engineering
The goal of this thesis is to generate fundamental understandings of charge transport behaviors of composites consisting of garnet structured Al substituted Li7La3Zr2O12 (LLZO) electrolyte and LiCoO2 electrode. In order to take full advantage of all-solid-state batteries, bulk type composite electrodes should be introduced to increase energy and power density. However, the charge utilization of bulk type composite electrodes is quite low. Understanding ionic conduction behavior is, therefore, important for improving the performance of all-solid-state batteries, because ion conduction within solids depends on effective pathways. Electronic conductivity can be easily compensated by ...
Processing, Microstructure, And Properties Of Engineered Diboride Structures, 2017 Missouri University of Science and Technology
Processing, Microstructure, And Properties Of Engineered Diboride Structures, Connor Charles Wittmaier
"The mechanical properties and processing parameters of boride ceramics in foam and laminate architectures were evaluated. The ceramic reticulated foam was produced through a polymer substrate replication technique and the hardness and compressive strength were tested. The laminate structure was tested to evaluate the flexure strength and work of fracture as a function of temperature.
The foam architecture was produced using a TiB2 slurry coating on a polyurethane reticulated foam preform. Foams sintered to 2150⁰C displayed an average grain size of 8.9 ± 7.3 µm, and a hardness of 17.3 ± 2.4 GPa. Crush testing foams were ...
Zirconium Diboride, Hexagonal Boron Nitride, And Amorphous Alumina Thin Films For High Temperature Applications, David Murdock Stewart
Electronic Theses and Dissertations
The use of microelectronic sensors and actuators in harsh, high temperature environments, such as power plants, turbine engines, and industrial manufacturing, could greatly improve the safety, reliability, and energy efficiency of these processes. The primary challenge in implementing this technology is the breakdown and degradation of thin films used in fabricating these devices when exposed to high temperatures >800 °C and oxidizing atmospheres. Zirconium diboride, hexagonal boron nitride, and amorphous alumina are candidate materials for use as thin film sensor components due to their high melting temperatures and stable phases. Zirconium diboride thin films have metallic-like electrical conductivity and remain ...
Giant Strain With Low Cycling Degradation In Ta-Doped [Bi1/2(Na0.8k0.2)1/2]Tio3 Lead-Free Ceramics, 2016 Iowa State University
Giant Strain With Low Cycling Degradation In Ta-Doped [Bi1/2(Na0.8k0.2)1/2]Tio3 Lead-Free Ceramics, Xiaoming Liu, Xiaoli Tan
Non-textured polycrystalline [Bi1/2 (Na 0.8K0.2)1/2](Ti1− x Ta x)O3 ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi1/2 (Na 0.8K0.2)1/2]TiO3 with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient ...
Helium Diffusion And Accumulation In Gd2ti2o7 And Gd2zr2o7, 2016 University of Tennessee, Knoxville
Helium Diffusion And Accumulation In Gd2ti2o7 And Gd2zr2o7, Caitlin Anne Taylor
The effects of helium accumulation on bubble formation and mechanical properties, as well as the fundamentals of helium diffusion in pyrochlores, are experimentally investigated in Gd2Ti2O7 [gadolinium titanate] and Gd2Zr2O7 [gadolinium zirconate]. We find that helium accumulation results in bubble formation at concentrations of 6 at.% in pre-damaged Gd2Ti2O7 and 4.6 at.% in pre-damaged Gd2Zr2O7. Lattice parameter, residual stress, and hardness changes due to helium accumulation were investigated in Gd2Zr2O7, which remains crystalline after ...
Microstructure And Properties Of Spark Plasma Sintered Moalb Ceramics, 2016 University of Nebraska-Lincoln
Microstructure And Properties Of Spark Plasma Sintered Moalb Ceramics, Ting Lou
Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research
Molybdenum aluminum boride (MoAlB) is a ternary transition metal boride which has promising aeronautic and nuclear applications. It inheres excellent properties of the binary transitional metal borides (e.g., MoB, ZrB2) such as high melting temperature, high hardness, and thermal conductivity. Besides, MoAlB is superior to MoB because: (1) the Al element provides an oxidation resistance at high temperatures; (2) its nanolaminated structure consisting of M-B layers with alternating Al layers results in a unique damage tolerance property. In this research, polycrystalline MoAlB have been successfully synthesized and simultaneously sintered using spark plasma sintering (SPS) from molybdenum boride (MoB ...
Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook
Electronic Theses and Dissertations
This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared ...
Nanoindentation Techniques For The Evaluation Of Silicon Nitride Thin Films, 2016 California Polytechnic State University, San Luis Obispo
Nanoindentation Techniques For The Evaluation Of Silicon Nitride Thin Films, Weston T. Mangin
Master's Theses and Project Reports
Silicon nitride thin films are of interest in the biomedical engineering field due to their biocompatibility and favorable tribological properties. Evaluation and understanding of the properties of these films under diverse loading and failure conditions is a necessary prerequisite to their use in biomedical devices. Three wafers of silicon nitride-coated silicon were obtained from Lawrence Livermore National Laboratory and used to create 96 samples. Samples were subjected to nanoindentation testing to evaluate the mechanical properties of the film. Samples were subjected to nanoimpact testing to compare the damage resistance of the film to separate nanoimpact types. Samples were subjected to ...
Empirical Models For Structural Effects Of A-Site Point Defects And Ordering In Perovskites, 2016 Boise State University
Empirical Models For Structural Effects Of A-Site Point Defects And Ordering In Perovskites, Kevin Ross Tolman
Boise State University Theses and Dissertations
Composition-structure-property relationships are essential keys to unlocking the strength of predictive crystal chemistry. Awkwardly, the electroceramics industry largely relies on various time-consuming and expensive trial-and-error experiments to address new questions which often could otherwise be interpolated from published data. Indeed, predictive models, which can be derived from empirical evidence, can greatly aid the direction and support of future development in a meaningful, apt, and cost-effective way. Theory suggests that intrinsic properties on the scale of a unit cell may be estimated from the sizes and charges of the chemical constituents alone. Ultimately, researchers could be provided a compositional recipe for ...