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1,069 full-text articles. Page 7 of 16.

A New Phase Boundary In (Bi1/2na1/2)Tio3Batio3 Revealed Via A Novel Method Of Electron Diffraction Analysis, Cheng Ma, Hanzheng Guo, Xiaoli Tan 2014 Iowa State University

A New Phase Boundary In (Bi1/2na1/2)Tio3Batio3 Revealed Via A Novel Method Of Electron Diffraction Analysis, Cheng Ma, Hanzheng Guo, Xiaoli Tan

Xiaoli Tan

A new phase boundary is revealed in (1-x)(Bi1/2Na1/2)TiO3xBaTiO3, the most extensively studied lead-free piezoelectric solid solution. This discovery results from a novel method of electron diffraction analysis, which allows for the precise determination of oxygen octahedra tilting in multi-domain perovskite ferroelectrics. The study using this method supports the recently proposed Cc symmetry for pure (Bi1/2Na1/2)TiO3, and, more importantly, indicates the crystal structure evolves into the R3c symmetry with the addition of BaTiO3, forming a Cc/R3c phase boundary at x = 3~4%. In the poling field Epol vs. composition x phase diagram ...


Zone Refining Of Raw Materials For Metal Halide Scintillator Crystal Growth, Thomas Williams McAlexander 2014 University of Tennessee - Knoxville

Zone Refining Of Raw Materials For Metal Halide Scintillator Crystal Growth, Thomas Williams Mcalexander

Masters Theses

In recent years, scintillators have been researched for homeland security applications where properties such as high light output and low energy resolution are required for efficient gamma ray spectroscopy. Several promising scintillators, including SrI2 [Strontium Iodide], CsSrI3 [Cesium Strontium Iodide], and KSr2I5 [Potassium Strontium Iodide] are activated with EuI2 [Europium Iodide]. The quality of EuI2 raw material is generally poor and inconsistent as-received from the manufacturer. Material purity is known to affect its scintillation performance, and so purification processes have been investigated to improve the performance of Eu-doped [Europium-doped] scintillators. In this work ...


Characterizing The Mechanical Behavior Of Single And Polycrystalline Silicon Carbide Using Nanoindentation., Amit Datye 2014 University of Tennessee - Knoxville

Characterizing The Mechanical Behavior Of Single And Polycrystalline Silicon Carbide Using Nanoindentation., Amit Datye

Doctoral Dissertations

This research aims at enhancing the fundamental understanding of mechanisms controlling the deformation and fracture of silicon carbide based ceramics (single- and poly-crystal). The role of microstructure and material properties on the energy absorption capability of SiC is studied. This research helps to improve the ability to quantitatively predict the initiation and propagation of fracture and the interaction between fracture and plasticity, which provides a step towards a mechanistic understanding of deformation and failure properties of ceramic single crystals and polycrystals. The validity of the indentation-cracking method for toughness measurement is examined using nanoindentation tests with different indenters (spherical, pyramidal ...


Plastic Anisotropy Of Complex Crystals And Hierarchically Structured Alloys Using Micro-Mechanical Computational Analysis, Lin Li 2014 University of Tennessee - Knoxville

Plastic Anisotropy Of Complex Crystals And Hierarchically Structured Alloys Using Micro-Mechanical Computational Analysis, Lin Li

Doctoral Dissertations

The material anisotropy is one of the most important material properties that cannot be disregarded in today’s world of materials designing and manufacturing. As new materials being developed and new material demands are introduced the inevitable focus on anisotropic materials has been brought under the spotlight. In this dissertation, several experimental and simulation project regarding material anisotropic effects on hexagonal close packed crystals such as Silicon Carbide as well and hierarchically structured solid solution ferritic based alloys. The general purpose was to demonstrate the improvement on various intended material properties using finite element method. Since indentation is a widely ...


Thermodynamic Modeling Of Uranium And Oxygen Containing Ternary Systems With Gadolinium, Lanthanum, And Thorium, Jacob Wesley McMurray 2014 University of Tennessee - Knoxville

Thermodynamic Modeling Of Uranium And Oxygen Containing Ternary Systems With Gadolinium, Lanthanum, And Thorium, Jacob Wesley Mcmurray

Doctoral Dissertations

The CALPHAD method is used to assess the thermodynamic properties and phase relations in the U-M-O system where M = Gd, La, and Th. A compound energy formalism (CEF) model for fluorite UO2±x [urania] is extended to represent the complex U1-yMyO2±x [urania solid solution] phases. The lattice stabilities for fictive GdO2 [gadolinia] and LaO2 [lanthana] fluorite structure compounds are calculated from density functional theory (DFT) for use in the CEF for U1-yMyO2±x [urania solid solution phase] while U6+ [uranium 6 plus cation] is introduced ...


Refractory Plasmonics With Titanium Nitride: Broadband Metamaterial Absorber, W Li, U. Guler, N. Kinsey, G. Naik, A. Boltasseva, J. Guan, V Shalaev, A. Kildishev 2014 Purdue University

Refractory Plasmonics With Titanium Nitride: Broadband Metamaterial Absorber, W Li, U. Guler, N. Kinsey, G. Naik, A. Boltasseva, J. Guan, V Shalaev, A. Kildishev

U. Guler

A high-temperature stable broadband plasmonic absorber is designed, fabricated, and optically characterized. A broadband absorber with an average high absorption of 95% and a total thickness of 240 nm is fabricated, using a refractory plasmonic material, titanium nitride. This absorber integrates both the plasmonic resonances and the dielectric-like loss. It opens a path for the interesting applications such as solar thermophotovoltaics and optical circuits.


In Situ Tem Study On The Microstructural Evolution During Electric Fatigue In 0.7pb(Mg1/3nb2/3)O3–0.3pbtio3 Ceramic, Hanzheng Guo, Xiaoli Tan, Shujun Zhang 2014 Iowa State University

In Situ Tem Study On The Microstructural Evolution During Electric Fatigue In 0.7pb(Mg1/3nb2/3)O3–0.3pbtio3 Ceramic, Hanzheng Guo, Xiaoli Tan, Shujun Zhang

Materials Science and Engineering Publications

In this work, we report an experimental technique with nanometer resolution to reveal the microstructural mechanism for electric fatigue in ferroelectrics. The electric field in situ transmission electron microscopy (TEM) was used to directly visualize the domain evolution during the fatigue process in a 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramic. The structure–property relationship was well demonstrated by combining the microscopic observations with corresponding dielectric, piezoelectric, and ferroelectric properties measured on bulk specimens. It was found that the domain switching capability was substantially suppressed after 103 cycles of bipolar fields, leading to an immobilized domain configuration thereafter ...


Surface Modification Of Aluminum Alloys By Plasma Electrolytic Oxidation, Vahid Dehnavi 2014 The University of Western Ontario

Surface Modification Of Aluminum Alloys By Plasma Electrolytic Oxidation, Vahid Dehnavi

Electronic Thesis and Dissertation Repository

Plasma Electrolytic Oxidation (PEO) is a surface treatment for the production of ceramic oxide coatings with great properties, such as high wear and corrosion resistance, on metal substrates, particularly aluminum and magnesium alloys. Formation of PEO coatings involves complex processes and mechanisms that are difficult to study. Currently, the PEO process is in a transition phase from research to commercial application, with a primary focus on the corrosion and wear protection of light alloys, and has recently generated interest as a promising surface treatment for biomedical applications.

To justify the industrial application of PEO, a more systematic and in-depth study ...


Microstructure Development Of Granular System During Compaction, Chen Shang, Marcial Gonzalez 2014 Purdue University

Microstructure Development Of Granular System During Compaction, Chen Shang, Marcial Gonzalez

The Summer Undergraduate Research Fellowship (SURF) Symposium

Granular materials is the second most manipulated material in the industry today. They are easy to transport and more and more newly developed materials cannot stand the process of traditional casting, like energetic materials and bio-materials, but will survive the powder compaction process. Having a better understanding of the microstructure development of granular systems during compaction process, especially for particles that will heavily deform under loading, will give an insight of how to better process the powders to produce materials with overall better performance comparing to bulk materials. The main theory and mechanism applied are Hertz law and nonlocal contact ...


Investigation Of The Performance Of Different Types Of Zirconium Microstructures Under Extreme Irradiation Conditions, Eric M. Acosta, Osman J. El-Atwani 2014 Purdue University

Investigation Of The Performance Of Different Types Of Zirconium Microstructures Under Extreme Irradiation Conditions, Eric M. Acosta, Osman J. El-Atwani

The Summer Undergraduate Research Fellowship (SURF) Symposium

The safe and continued operation of the US nuclear power plants requires improvement of the radiation resistant properties of materials used in nuclear reactors. Zirconium is a material of particular interest due to its use in fuel cladding. Studies performed on other materials have shown that grain boundaries can play a significant role on the radiation resistant properties of a material. Thus, the focus of our research is to investigate the performance of different zirconium microstructures under irradiation conditions similar to those in commercial nuclear reactors. Analysis of the surface morphology of zirconium both pre- and post-irradiation was conducted with ...


Dependence Of The Magnetostrictive Properties Of Cobalt Ferrite On The Initial Powder Particle Size Distribution, Cajetan Ikenna Nlebedim, David C. Jiles 2014 Iowa State University

Dependence Of The Magnetostrictive Properties Of Cobalt Ferrite On The Initial Powder Particle Size Distribution, Cajetan Ikenna Nlebedim, David C. Jiles

David C. Jiles

The dependence of the magnetostrictive properties of cobalt ferrite on the size distribution of thepowder used in deriving the samples from traditional ceramic approach is presented. Sample obtained by combining the smallest and largest particle size distributions gave the highestmagnetostriction and strain sensitivity (216 ppm and 1.34 nm/A, respectively), for measurementin parallel direction but the least (66 ppm and 0.38 nm/A respectively) in perpendicular direction. Sample derived from largest particle size distribution gave the least magnetostriction and strain sensitivity (147 ppm and 0.61 nm/A, respectively) in parallel direction but the highest (126 ppm and ...


Radiation-Induced Radicals In Polyurea-Crosslinked Silica Aerogel, Benjamin Michael Walters 2014 University of Tennessee - Knoxville

Radiation-Induced Radicals In Polyurea-Crosslinked Silica Aerogel, Benjamin Michael Walters

Masters Theses

Free radicals are atoms or molecules with an odd number of electrons in an outer shell. Since electrons typically occur in pairs, this leaves one electron that is unpaired. In seek of another electron to pair with, free radicals react with and steal electrons from neighboring molecules, which then become free radicals themselves. This can start a chain reaction, cascading into large scale damage.

Ionizing radiation can tear through molecules, just as bullets can tear through things that we see. If free radicals can be detected, and seen to increase in a material upon radiation exposure, this can indicate molecular ...


The Electronic And Thermodynamic Properties Of Ca Doped Lafeo3 – A First Principles Study Using Density Functional Theory, Davis George Daniel 2014 Boise State University

The Electronic And Thermodynamic Properties Of Ca Doped Lafeo3 – A First Principles Study Using Density Functional Theory, Davis George Daniel

Boise State University Theses and Dissertations

Density functional theory (DFT) was used to evaluate the electronic and thermodynamic properties of Ca-doped LaFeO3 (La1-xCaxFeO3-y). La1-xCaxFeO3-y exhibits ionic (O2- anions) and electronic conductivity at high temperatures and has potential applications in gas separation, syngas production and solid oxide fuel cell cathodes. DFT is a computational technique based on the First Principles of physics, derived from the theory of quantum mechanics. DFT approximates the ground state energy of a system and can subsequently determine many bulk properties such as lattice constants, magnetic states, band gap, density of ...


Infrared Transmitting Glasses With High Glass Transition Temperatures, Steve W. Martin 2014 Iowa State University

Infrared Transmitting Glasses With High Glass Transition Temperatures, Steve W. Martin

Iowa State University Patents

A chalcogenide glass capable of infrared transmission which is either sulfur, selenium or tellurium based and consists of compositions of the formula MX+M.sub.2 'X.sub.3 +SiX.sub.2, wherein M is one of the metals calcium, strontium, barium, zinc and lead, and M' is either aluminum or gallium and X is either sulfur, selenium or tellurium. Aluminum or gallium chalcogenide acts to increase the covalent bonding network structure of the glass with the result being that excellent high temperature 8-14 micron IR transmitting glasses with transition temperatures above 500C are prepared.


Modulating Notochordal Differentiation Of Human Induced Pluripotent Stem Cells Using Natural Nucleus Pulposus Tissue Matrix, Yongxing Liu, M. N. Rahaman, B. Sonny Bal 2014 Missouri University of Science and Technology

Modulating Notochordal Differentiation Of Human Induced Pluripotent Stem Cells Using Natural Nucleus Pulposus Tissue Matrix, Yongxing Liu, M. N. Rahaman, B. Sonny Bal

Materials Science and Engineering Faculty Research & Creative Works

Human induced pluripotent stem cells (hiPSCs) can differentiate into notochordal cell (NC)-like cells when cultured in the presence of natural porcine nucleus pulposus (NP) tissue matrix. The method promises massive production of high-quality, functional cells to treat degenerative intervertebral discs (IVDs). Based on our previous work, we further examined the effect of cell-NP matrix contact and culture medium on the differentiation, and further assessed the functional differentiation ability of the generated NC-like. The study showed that direct contact between hiPSCs and NP matrix can promote the differentiation yield, whilst both the contact and non-contact cultures can generate functional NC-like ...


Polarization Alignment, Phase Transition, And Piezoelectricity Development In Polycrystalline 0.5ba(Zr0.2ti0.8)O3−0.5(Ba0.7ca0.3)Tio3, Hanzheng Guo, Brian K. Voas, Shujun Zhang, Chao Zhou, Xiaobing Ren, Scott P. Beckman, Xiaoli Tan 2014 Iowa State University

Polarization Alignment, Phase Transition, And Piezoelectricity Development In Polycrystalline 0.5ba(Zr0.2ti0.8)O3−0.5(Ba0.7ca0.3)Tio3, Hanzheng Guo, Brian K. Voas, Shujun Zhang, Chao Zhou, Xiaobing Ren, Scott P. Beckman, Xiaoli Tan

Materials Science and Engineering Publications

The microstructural origin of the exceptionally high piezoelectric response of polycrystalline 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 is investigated using in situ transmission electron microscopy, in addition to a wide variety of bulk measurements and first-principles calculations. A direct correlation is established relating a domain wall-free state to the ultrahigh piezoelectric d33 coefficient in this BaTiO3-based composition. The results suggest that the unique single-domain state formed during electrical poling is a result of a structural transition from coexistent rhombohedral and tetragonal phases to an orthorhombic phase that has an anomalously low elastic modulus. First-principles ...


Characterizing The Pore Structure Of Carbonated Natural Wollastonite, Chiara Villani, Robert Spragg, Raikhan Tokpatayeva, Jan Olek, W. Jason Weiss 2014 Purdue University

Characterizing The Pore Structure Of Carbonated Natural Wollastonite, Chiara Villani, Robert Spragg, Raikhan Tokpatayeva, Jan Olek, W. Jason Weiss

International Conference on Durability of Concrete Structures

This paper focuses on examining the pore structure of a cementitious paste made with a calcium silicate (wollastonite) that reacts with carbon dioxide and water to form a hardened solid. The pore structure of the hardened solid has been characterized using vapor sorption and desorption, low-temperature differential scanning calorimetry (LT-DSC), and scanning electron microscopy (SEM). The total porosity was also measured using mass measurement in oven-dry and vacuum-saturated conditions. Evidence exists that support the hypothesis that the solid has two main pore sizes: large macropores (>10 nm) appear to form between the initial calcium silicate particles and small micropores (<10 >nm ...


Unique Single-Domain State In A Polycrystalline Ferroelectric Ceramic, Hanzheng Guo, Chao Zhou, Xiaoli Tan 2014 Iowa State University

Unique Single-Domain State In A Polycrystalline Ferroelectric Ceramic, Hanzheng Guo, Chao Zhou, Xiaoli Tan

Xiaoli Tan

Non-180° ferroelectric domains are also ferroelastic domains; their existence in polycrystalline materials is to relieve internal stresses generated during solid-solid phase transitions and minimize the elastic distortion energy. Therefore, grains with random orientations in polycrystalline ceramics are always occupied by many domains, especially in the regions close to grain boundaries. In this Rapid Communication, we report the observation of a single-domain state in a BaTiO3-based polycrystalline ceramic at intermediate poling electric fields with in situ transmission electron microscopy. The grains in the virgin ceramic and under high poling fields are found multidomained. The unique single-domain state is believed to be ...


Developent Of A Phospholipid Encapsulation Process For Quantum Dots To Be Used In Biologic Applications, Logan Grimes 2014 California Polytechnic State University, San Luis Obispo

Developent Of A Phospholipid Encapsulation Process For Quantum Dots To Be Used In Biologic Applications, Logan Grimes

Master's Theses and Project Reports

The American Cancer Society predicts that 1,665,540 people will be diagnosed with cancer, and 585,720 people will die from cancer in 2014. One of the most common types of cancer in the United States is skin cancer. Melanoma alone is predicted to account for 10,000 of the cancer related deaths in 2014. As a highly mobile and aggressive form of cancer, melanoma is difficult to fight once it has metastasized through the body. Early detection in such varieties of cancer is critical in improving survival rates in afflicted patients. Present methods of detection rely on visual ...


Material Composition And Toxicology Of Cosmetic Products, Hilda Gonzalez 2014 California Polytechnic State University - San Luis Obispo

Material Composition And Toxicology Of Cosmetic Products, Hilda Gonzalez

Materials Engineering

In today’s modern society, the U.S. Food and Drug Administration regulates many industries to protect consumers’ health; the cosmetics industry is not one of them. Through self-regulation, companies continue to sell products for topical use on the body that have been known to contain toxic chemicals with little to no testing on the effects they have on the human body. The purpose of this project was to determine the content of such known toxins in five different brands of face powders. X-Ray Diffraction (XRD) was used to verify the primary component and Inductively Coupled Plasma-Optical Emissions Spectroscopy (ICP-OES ...


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