Download or read book Predicting the Equilibria of Point Defects in Zirconium Oxide written by Mostafa Youssef Mahmoud Youssef and published by . This book was released on 2014 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of zirconium alloys in nuclear reactors is compromised by corrosion and hydrogen pickup. The thermodynamics and kinetics of these two processes are governed by the behavior of point defects in the ZrO2 layer that grows natively on these alloys. In this thesis, we developed a general, broadly applicable framework to predict the equilibria of point defects in a metal oxide. The framework is informed by density functional theory and relies on notions of statistical mechanics. Validation was performed on the tetragonal and monoclinic phases of ZrO2 by comparison with prior conductivity experiments. The framework was applied to four fundamental problems for understanding the corrosion and hydrogen pickup of zirconium alloys. First, by coupling the predicted concentrations of oxygen defects in tetragonal ZrO2 with their calculated migration barriers, we determined oxygen self-diffusivity in a wide range of thermodynamic conditions spanning from the metal-oxide interface to the oxide-water interface. This facilitates future macro-scale modeling of the oxide layer growth kinetics on zirconium alloys. Second, using the computed defect equilibria of the tetragonal and monoclinic phases, we constructed a temperature-oxygen partial pressure phase diagram for ZrO2. The diagram showed that the tetragonal phase can be stabilized below its atmospheric transition-temperature by lowering the oxygen chemical potential. This work adds a new explanation to the stabilization of the tetragonal phase at the metal-oxide interface where the oxygen partial pressure is low. Third, using the developed framework, we modeled co-doping of monoclinic ZrO2 with hydrogen and a transition metal. Our modeling predicted a volcano-like dependence of hydrogen (proton) solubility on the first-row transition metals, which is consistent with a set of systematic experiments from the nuclear industry. We discovered that the reason behind this behavior is the ability of the transition metal to p-type-dope ZrO2 and hence lower the chemical potential of electron. Therefore, the peak of the hydrogen solubility in monoclinic ZrO2 also corresponds to an increased barrier for hydrogen gas evolution on the surface. This explanation opens the door to physics-based design of resistant zirconium alloys, and qualitatively consistent with the monoclinic ZrO2. Finally, we uncovered the interplay between certain hydrogen defects and planar compressive stress which tetragonal ZrO2 experiences on zirconium alloys. The stress enhances the abundance of these defects, while these same defects tend to relax the stress. This interplay was used to propose an oxide fracture mechanism by which hydrogen is picked up.
Download or read book First principles Based Treatment of Charged Species Equilibria at Electrochemical Interfaces Model System of Zirconium Oxide and Titanium Oxide written by Jing Yang (Ph. D.) and published by . This book was released on 2020 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ionic defects are known to influence the magnetic, electronic and transport properties of oxide materials. Understanding defect chemistry provides guidelines for defect engineering in various applications including energy storage and conversion, corrosion, and neuromorphic computing devices. While DFT calculations have been proven as a powerful tool for modeling point defects in bulk oxide materials, challenges remain for linking atomistic results with experimentally-measurable materials properties, where impurities and complicated microstructures exist and the materials deviate from ideal bulk behavior. This thesis aims to bridge this gap on two aspects. First, we study the coupled electro-chemo-mechanical effects of ionic impurities in bulk oxide materials. Second, we develop a modeling framework for describing point defect redistribution at extended defects, including grain boundaries, oxide/oxide interfaces, and oxide/water interfaces. The first part of this thesis deals with zirconium oxide in the context of corrosion of zirconium alloys used as nuclear cladding materials in light water reactors. We provide physically-deduced diffusion coefficients for higher-level modeling as well as better mechanistic understanding of zirconium alloy corrosion by studying defect equilibria in ZrO2 passive films. A first-principles based model for predicting charged species redistribution profiles at electrochemical interfaces is established and applied to ZrO2/Cr2O3 and ZrO2/water interfaces, and ZrO2 grain boundaries. Defect redistribution at these extended defects can lead to significant changes in transport properties of oxides. The second part applies similar methodology to TiO2 as a model system for studying field-assisted sintering (FAST). FAST has been demonstrated for multiple ceramic materials as a promising sintering technique for shortening consolidation times and lowering sintering temperatures. By studying the defect chemistry of acceptor- and donor-TiO2 and designing experiments accordingly, we show that while Joule heating is the dominant effect of the applied electric field, the shrinkage rate also correlates strongly with titanium diffusivity. Through donor doping, which increases the concentrations of fast-diffusing titanium interstitials, a higher shrinkage rate is achievable. These results prove that first-principles base calculations are capable of predicting the defect chemistry of oxide materials that quantitatively agree with measured values. Such understanding of defect chemistry gives insights into practical defect engineering strategies that are broadly applicable to electrochemical applications.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1975 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Defects in HIgh k Gate Dielectric Stacks written by Evgeni Gusev and published by Springer Science & Business Media. This book was released on 2006-01-27 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main goal of this book is to review at the nano and atomic scale the very complex scientific issues that pertain to the use of advanced high dielectric constant (high-k) materials in next generation semiconductor devices. One of the key obstacles to integrate this novel class of materials into Si nano-technology are the electronic defects in high-k dielectrics. It has been established that defects do exist in high-k dielectrics and they play an important role in device operation. The unique feature of this book is a special focus on the important issue of defects. The subject is covered from various angles, including silicon technology, processing aspects, materials properties, electrical defects, microstructural studies, and theory. The authors who have contributed to the book represents a diverse group of leading scientists from academic, industrial and governmental labs worldwide who bring a broad array of backgrounds (basic and applied physics, chemistry, electrical engineering, surface science, and materials science). The contributions to this book are accessible to both expert scientists and engineers who need to keep up with leading edge research, and newcomers to the field who wish to learn more about the exciting basic and applied research issues relevant to next generation device technology.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Point Defect Effects on Hot Corrosion of Zirconia Based Coatings written by and published by . This book was released on 1991 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal barrier coatings are vulnerable to certain types of hot corrosion: sulfidation and vanadic attack. Stabilized zirconia, an often used thermal barrier coating, is degraded by dissolution of the stabilizing components, mass transport in the coating must occur. The presence of point defects in a crystalline solid greatly affect the transport properties in that solid. The nature and concentration of these defects can be altered which, in turn, can impart large changes in the transport properties of a material (eg. ionic conductivity and diffusion). In this study, we are determining the defect structures of yttria and ceria-stabilized zirconium oxides. Using electrical conductivity measurements, the activation energy of yttria-stabilized have been examined as a function of frequency, composition, and oxygen activity. Conductivity measurements on ceria-stabilized zirconia have shown anomalous results. At low oxygen activities, ZrO2-CeO2 samples did not reach equilibrium. The cause for this phenomenon has yet to be determined. Transport properties of molten Na2SO4 have been investigated to aid in understanding hot corrosion processes at 1173 K. An A.C. impedance technique for the total electrical conductivity, the potentiostatic polarization method for ionic transport number, and the steady state polarization method of Wagner and Hebb for the electronic conductivity were employed as a function of Na2O activity in the melt by controlling gas atmosphere.
Download or read book Studying point defects in zirconium irradiated by neutrons at 24 k written by P. Vialaret and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Solid State Materials Chemistry written by Patrick M. Woodward and published by Cambridge University Press. This book was released on 2021-04 with total page 709 pages. Available in PDF, EPUB and Kindle. Book excerpt: A modern and thorough treatment of the field for upper-level undergraduate and graduate courses in materials science and chemistry.
Download or read book Metals Abstracts Index written by and published by . This book was released on 1996 with total page 1622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Air Force Research Resum s written by and published by . This book was released on with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1998-04 with total page 1176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ERDA Energy Research Abstracts written by United States. Energy Research and Development Administration and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Journal of Physics and Chemistry of Solids written by and published by . This book was released on 1990 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Diffusion and Defect Data written by and published by . This book was released on 2000 with total page 918 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Download or read book Comprehensive Nuclear Materials written by and published by Elsevier. This book was released on 2020-07-22 with total page 4871 pages. Available in PDF, EPUB and Kindle. Book excerpt: Materials in a nuclear environment are exposed to extreme conditions of radiation, temperature and/or corrosion, and in many cases the combination of these makes the material behavior very different from conventional materials. This is evident for the four major technological challenges the nuclear technology domain is facing currently: (i) long-term operation of existing Generation II nuclear power plants, (ii) the design of the next generation reactors (Generation IV), (iii) the construction of the ITER fusion reactor in Cadarache (France), (iv) and the intermediate and final disposal of nuclear waste. In order to address these challenges, engineers and designers need to know the properties of a wide variety of materials under these conditions and to understand the underlying processes affecting changes in their behavior, in order to assess their performance and to determine the limits of operation. Comprehensive Nuclear Materials, Second Edition, Seven Volume Set provides broad ranging, validated summaries of all the major topics in the field of nuclear material research for fission as well as fusion reactor systems. Attention is given to the fundamental scientific aspects of nuclear materials: fuel and structural materials for fission reactors, waste materials, and materials for fusion reactors. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource of information. Most of the chapters from the first Edition have been revised and updated and a significant number of new topics are covered in completely new material. During the ten years between the two editions, the challenge for applications of nuclear materials has been significantly impacted by world events, public awareness, and technological innovation. Materials play a key role as enablers of new technologies, and we trust that this new edition of Comprehensive Nuclear Materials has captured the key recent developments. Critically reviews the major classes and functions of materials, supporting the selection, assessment, validation and engineering of materials in extreme nuclear environments Comprehensive resource for up-to-date and authoritative information which is not always available elsewhere, even in journals Provides an in-depth treatment of materials modeling and simulation, with a specific focus on nuclear issues Serves as an excellent entry point for students and researchers new to the field
Download or read book Journal of the Chemical Society written by and published by . This book was released on 1989 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt:
