Download or read book Multiscale Modeling of Evolution of SiC Microstructure Due to Radiation and Corrosion written by Cheng Liu and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: SiC is an attractive material for nuclear energy, aerospace and semiconductor industries because of its uniquely combined properties, such as high-temperature strength, low neutron cross section, excellent corrosion and oxidation resistance, wide band-gap and low thermal expansion coefficient. Current and proposed applications include nuclear fuel components, nuclear structural components, airplane turbines, aerospace thermal protection layers and semiconductor electronics, etc. High temperature, irradiation and oxidizing environments can lead to degradation of SiC and its reduced reliability in application systems. This thesis is focused on understanding radiation-induced defects generation and evolution and as well as mechanisms of environmental degradation. Firstly, I report a statistical analysis of sizes and compositions of clusters produced in cascades during irradiation of SiC. The results are obtained by integrating molecular dynamics simulations of cascades caused by primary knock-on atoms (PKAs) over PKA energy spectrum derived from Stopping Range of Ions in Matter (SRIM) code. It is found that distributions of cluster size n obey a power law [f=A/n^S] and these clusters are dominated by carbons defects. Secondly, distribution of black spot defects (BSDs) and small clusters in irradiated 3C-SiC has been investigated by combining microscopy characterization with cluster dynamics (CD) model. It is found that there are small clusters identified in scanning transmission electron microscopy (STEM) invisible in TEM images. Simulations showed that both established properties of point defects (PDs) generation, reaction, clustering, and cluster dissociation, and additional phenomena of clusters generation, diffusion and morphology preference are necessary to be considered in a predictive model on cluster evolution in ion irradiated SiC. Then, based on CD model above, I developed a swelling model to estimate the swelling contributed by defects, which qualitatively explains that the swelling estimated based on X-Ray diffraction (XRD) is larger than that based on TEM is because there are PDs and small clusters invisible from TEM. Lastly, our molecular dynamics simulations show Incoherent grain boundaries (GBs) were more vulnerable to oxidation than single crystals, whereas oxidation of bicrystals with coherent GBs proceeded at a similar rate to that on single crystals. The accelerated oxidation along incoherent GBs can be attributed to larger free volume and silicon atoms with more negative charge state near GBs.

Download or read book Evolution of Radiation Induced Defects in SiC written by Hao Jiang and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of various excellent properties, SiC has been proposed for many applications in nuclear reactors including cladding layers in fuel rod, fission products container in TRISO fuel, and first wall/blanket in magnetic controlled fusion reactors. Upon exposure to high energy radiation environments, point defects and defect clusters are generated in materials in amounts significantly exceeding their equilibrium concentrations. The accumulation of defects can lead to undesired consequences such as crystalline-to-amorphous transformation1, swelling, and embrittlement, and these phenomena can adversely affect the lifetime of SiC based components in nuclear reactors. It is of great importance to understand the accumulation process of these defects in order to estimate change in properties of this material and to design components with superior ability to withstand radiation damages. Defect clusters are widely in SiC irradiated at the operation temperatures of various reactors. These clusters are believed to cause more than half of the overall swelling of irradiated SiC and can potentially lead to lowered thermal conductivity and mechanical strength. It is critical to understand the formation and growth of these clusters. Diffusion of these clusters is one importance piece to determine the growth rate of clusters; however it is unclear so far due to the challenges in simulating rare events. Using a combination of kinetic Activation Relaxation Technique with empirical potential and ab initio based climbing image nudged elastic band method, I performed an extensive search of the migration paths of the most stable carbon tri-interstitial cluster in SiC. This research reveals paths with the lowest energy barriers to migration, rotation, and dissociation of the most stable cluster. Based on these energy barriers, I concluded defect clusters are thermally immobile at temperatures lower than 1500 K and can dissociate into smaller clusters and single interstitials at temperatures beyond that. Even though clusters cannot diffuse by thermal vibrations, we found they can migrate at room temperature under the influence of electron radiation. This is the first direct observation of radiation-induced diffusion of defect clusters in bulk materials. We show that the underlying mechanism of this athermal diffusion is elastic collision between incoming electrons and cluster atoms. Our findings suggest that defect clusters may be mobile under certain irradiation conditions, changing current understanding of cluster annealing process in irradiated SiC. With the knowledge of cluster diffusion in SiC demonstrated in this thesis, we now become able to predict cluster evolution in SiC with good agreement with experimental measurements. This ability can enable us to estimate changes in many properties of irradiated SiC relevant for its applications in reactors. Internal interfaces such as grain boundaries can behave as sinks to radiation induced defects. The ability of GBs to absorb, transport, and annihilate radiation-induced defects (sink strength) is important to understand radiation response of polycrystalline materials and to better design interfaces for improved resistance to radiation damage. Nowadays, it is established GBs' sink strength is not a static property but rather evolves with many factors, including radiation environments, grain size, and GB microstructure. In this thesis, I investigated the response of small-angle tilt and twist GBs to point defects fluxes in SiC. First of all, I found the pipe diffusion of interstitials in tilt GBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, I show that both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled and can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the role of tilt GBs in annihilating radiation damage. The model predicts the role of tilt GBs in annihilating defects depends on the rate of defects segregation to and diffusion along tilt GBs. Tilt GBs mainly serve as diffusion channel for defects to reach other sinks when defect diffusivity is high at boundaries. When defect diffusivity is low, most of the defects segregated to tilt GBs are annihilated by dislocation climb. Up-to-date, the response of twist GBs under irradiation has been rarely reported in literature and is still unclear. It is important to develop atom scale insight on this question in order to predict twist GBs' sink strength for a better understanding of radiation response of polycrystalline materials. By using a combination of molecular dynamics and grand canonical Monte Carlo, here I demonstrate the defect kinetics in {001} and {111} twist GBs and the microstructural evolution of these GBs under defect fluxes in SiC. I found due to the deep potential well for interstitials at dislocation intersections within the interface, the mobility of defects on dislocation grid is retard and this leads to defect accumulation at GBs for many cases. Furthermore, I conclude both types of twist GBs have to form mixed dislocations with edge component in order to absorb accumulated interstitials at the interface. The formation of mixed dislocation is either by interstitial loop nucleation or by dislocation reactions at the interface. The continuous formation and climb of these mixed dislocations make twist GBs unsaturatable sinks to radiation induced defects.

Download or read book Radiation Effects and Micromechanics of SiC SiC Composites December 1 1990 November 14 1993 and Modeling the Mechanical Behavior of SiC SiC Composites in Fusion Environments November 15 1993 November 14 1996 Final Report December 1 1990 November 14 1996 written by and published by . This book was released on 1997 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of Silicon Carbide composite materials for structural applications in fusion energy systems is mainly motivated by the prospect that fusion power systems utilizing the material will have a much more favorable environmental impact. The research team at UCLA was the first to identify the potential advantages of SiC/SiC composite materials through early System Studies. Consequently, two three-year term grants have been awarded to the team, in order to focus on modeling the effects of irradiation on key properties that have been recognized by the community as fundamental to the successful development of the composite. Two main tasks, which are further subdivided into several subtasks each, have been pursued during the course of research during the period: December 1990 through November 1996. The first task deals with modeling the effects of irradiation on the dimensional stability of SiC. To achieve this goal, a substantial effort was launched for modeling the evolution of the microstructure under irradiation. Rate and Fokker-Planck theories have been advanced to model the complex multi-component system of SiC under irradiation. The effort has resulted in a deeper understanding of the interaction between displacement damage components, and transmutant helium gas atoms. Utilizing the methods of Molecular Dynamics (MD) and Monte Carlo (MC), the energetics of defects and the basic displacement mechanisms in SiC have been fully delineated. An advanced Fokker-Planck approach was formulated to determine the phase content and size distribution of damage microstructure in SiC. Finally, a rate theory model was developed and successfully applied to the experimental swelling data on SiC. In the second task, the authors investigated the mechanical behavior of SiC/SiC composites under the irradiation conditions of fusion reactors. The main focus of the second task has been on developing models for the micro-mechanics of cracks in the fiber reinforced matrix of the silicon carbide composite. The effects of irradiation on inducing inelastic deformations in the fiber and the matrix were emphasized. Brief reviews for the results of their research are given here, followed by copies of 26 journal publications resulting from the work supported under this grant.

Download or read book Radiation Effects and Micromechanics of SiC written by and published by . This book was released on 1997 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of Silicon Carbide composite materials for structural applications in fusion energy systems is mainly motivated by the prospect that fusion power systems utilizing the material will have a much more favorable environmental impact. The research team at UCLA was the first to identify the potential advantages of SiC/SiC composite materials through early System Studies. Consequently, two three-year term grants have been awarded to the team, in order to focus on modeling the effects of irradiation on key properties that have been recognized by the community as fundamental to the successful development of the composite. Two main tasks, which are further subdivided into several subtasks each, have been pursued during the course of research during the period: December 1990 through November 1996. The first task deals with modeling the effects of irradiation on the dimensional stability of SiC. To achieve this goal, a substantial effort was launched for modeling the evolution of the microstructure under irradiation. Rate and Fokker-Planck theories have been advanced to model the complex multi-component system of SiC under irradiation. The effort has resulted in a deeper understanding of the interaction between displacement damage components, and transmutant helium gas atoms. Utilizing the methods of Molecular Dynamics (MD) and Monte Carlo (MC), the energetics of defects and the basic displacement mechanisms in SiC have been fully delineated. An advanced Fokker-Planck approach was formulated to determine the phase content and size distribution of damage microstructure in SiC. Finally, a rate theory model was developed and successfully applied to the experimental swelling data on SiC. In the second task, the authors investigated the mechanical behavior of SiC/SiC composites under the irradiation conditions of fusion reactors. The main focus of the second task has been on developing models for the micro-mechanics of cracks in the fiber reinforced matrix of the silicon carbide composite. The effects of irradiation on inducing inelastic deformations in the fiber and the matrix were emphasized. Brief reviews for the results of their research are given here, followed by copies of 26 journal publications resulting from the work supported under this grant.

Download or read book Possible Microstructure Evolution of SiC Under High Transmutation Rates written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 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 1994 with total page 1620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Temperature Ceramic Matrix Composites written by R. Naslain and published by Woodhead Publishing Limited. This book was released on 1993 with total page 864 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sintering Technology written by Randall M. German and published by CRC Press. This book was released on 2020-09-30 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the sintering conference held at the Pennsylvania State University, USA, this text presents advances in the application of sintering to the most important industrial materials. It offers results on both solid-state and microphase sintering as well as microstructure evolution, and introduces new applications, processes, materials and solutions to technical problems.

Download or read book Ceramic Matrix Composites written by Narottam P. Bansal and published by John Wiley & Sons. This book was released on 2014-10-27 with total page 725 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a comprehensive source of information on various aspects of ceramic matrix composites (CMC). It covers ceramic and carbon fibers; the fiber-matrix interface; processing, properties and industrial applications of various CMC systems; architecture, mechanical behavior at room and elevated temperatures, environmental effects and protective coatings, foreign object damage, modeling, life prediction, integration and joining. Each chapter in the book is written by specialists and internationally renowned researchers in the field. This book will provide state-of-the-art information on different aspects of CMCs. The book will be directed to researchers working in industry, academia, and national laboratories with interest and professional competence on CMCs. The book will also be useful to senior year and graduate students pursuing degrees in ceramic science and engineering, materials science and engineering, aeronautical, mechanical, and civil or aerospace engineering. Presents recent advances, new approaches and discusses new issues in the field, such as foreign object damage, life predictions, multiscale modeling based on probabilistic approaches, etc. Caters to the increasing interest in the application of ceramic matrix composites (CMC) materials in areas as diverse as aerospace, transport, energy, nuclear, and environment. CMCs are considered ans enabling technology for advanced aeropropulsion, space propulsion, space power, aerospace vehicles, space structures, as well as nuclear and chemical industries. Offers detailed descriptions of ceramic and carbon fibers; fiber-matrix interface; processing, properties and industrial applications of various CMC systems; architecture, mechanical behavior at room and elevated temperatures, environmental effects and protective coatings, foreign object damage, modeling, life prediction, integration/joining.

Download or read book Research Opportunities in Corrosion Science and Engineering written by National Research Council and published by National Academies Press. This book was released on 2011-01-27 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of corrosion science and engineering is on the threshold of important advances. Advances in lifetime prediction and technological solutions, as enabled by the convergence of experimental and computational length and timescales and powerful new modeling techniques, are allowing the development of rigorous, mechanistically based models from observations and physical laws. Despite considerable progress in the integration of materials by design into engineering development of products, corrosion considerations are typically missing from such constructs. Similarly, condition monitoring and remaining life prediction (prognosis) do not at present incorporate corrosion factors. Great opportunities exist to use the framework of these materials design and engineering tools to stimulate corrosion research and development to achieve quantitative life prediction, to incorporate state-of-the-art sensing approaches into experimentation and materials architectures, and to introduce environmental degradation factors into these capabilities. Research Opportunities in Corrosion Science and Engineering identifies grand challenges for the corrosion research community, highlights research opportunities in corrosion science and engineering, and posits a national strategy for corrosion research. It is a logical and necessary complement to the recently published book, Assessment of Corrosion Education, which emphasized that technical education must be supported by academic, industrial, and government research. Although the present report focuses on the government role, this emphasis does not diminish the role of industry or academia.

Download or read book A Practical Guide to Rock Microstructure written by Ron H. Vernon and published by Cambridge University Press. This book was released on 2004-10-07 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rock microstructures provide clues for the interpretation of rock history. A good understanding of the physical or structural relationships of minerals and rocks is essential for making the most of more detailed chemical and isotopic analyses of minerals. Ron Vernon discusses the basic processes responsible for the wide variety of microstructures in igneous, sedimentary, metamorphic and deformed rocks, using high-quality colour illustrations. He discusses potential complications of interpretation, emphasizing pitfalls, and focussing on the latest techniques and approaches. Opaque minerals (sulphides and oxides) are referred to where appropriate. The comprehensive list of relevant references will be useful for advanced students wishing to delve more deeply into problems of rock microstructure. Senior undergraduate and graduate students of mineralogy, petrology and structural geology will find this book essential reading, and it will also be of interest to students of materials science.

Download or read book Multiscale Materials Modeling written by Siegfried Schmauder and published by . This book was released on 2016 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reactor Core Materials written by and published by . This book was released on 1960 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Damage Mechanics written by George Z. Voyiadjis and published by Springer. This book was released on 2014-10-14 with total page 1579 pages. Available in PDF, EPUB and Kindle. Book excerpt: This authoritative reference provides comprehensive coverage of the topics of damage and healing mechanics. Computational modeling of constitutive equations is provided as well as solved examples in engineering applications. A wide range of materials that engineers may encounter are covered, including metals, composites, ceramics, polymers, biomaterials, and nanomaterials. The internationally recognized team of contributors employ a consistent and systematic approach, offering readers a user-friendly reference that is ideal for frequent consultation. Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures is ideal for graduate students and faculty, researchers, and professionals in the fields of Mechanical Engineering, Civil Engineering, Aerospace Engineering, Materials Science, and Engineering Mechanics.

Download or read book Fundamentals of Radiation Materials Science written by GARY S. WAS and published by Springer. This book was released on 2016-07-08 with total page 1014 pages. Available in PDF, EPUB and Kindle. Book excerpt: The revised second edition of this established text offers readers a significantly expanded introduction to the effects of radiation on metals and alloys. It describes the various processes that occur when energetic particles strike a solid, inducing changes to the physical and mechanical properties of the material. Specifically it covers particle interaction with the metals and alloys used in nuclear reactor cores and hence subject to intense radiation fields. It describes the basics of particle-atom interaction for a range of particle types, the amount and spatial extent of the resulting radiation damage, the physical effects of irradiation and the changes in mechanical behavior of irradiated metals and alloys. Updated throughout, some major enhancements for the new edition include improved treatment of low- and intermediate-energy elastic collisions and stopping power, expanded sections on molecular dynamics and kinetic Monte Carlo methodologies describing collision cascade evolution, new treatment of the multi-frequency model of diffusion, numerous examples of RIS in austenitic and ferritic-martensitic alloys, expanded treatment of in-cascade defect clustering, cluster evolution, and cluster mobility, new discussion of void behavior near grain boundaries, a new section on ion beam assisted deposition, and reorganization of hardening, creep and fracture of irradiated materials (Chaps 12-14) to provide a smoother and more integrated transition between the topics. The book also contains two new chapters. Chapter 15 focuses on the fundamentals of corrosion and stress corrosion cracking, covering forms of corrosion, corrosion thermodynamics, corrosion kinetics, polarization theory, passivity, crevice corrosion, and stress corrosion cracking. Chapter 16 extends this treatment and considers the effects of irradiation on corrosion and environmentally assisted corrosion, including the effects of irradiation on water chemistry and the mechanisms of irradiation-induced stress corrosion cracking. The book maintains the previous style, concepts are developed systematically and quantitatively, supported by worked examples, references for further reading and end-of-chapter problem sets. Aimed primarily at students of materials sciences and nuclear engineering, the book will also provide a valuable resource for academic and industrial research professionals. Reviews of the first edition: "...nomenclature, problems and separate bibliography at the end of each chapter allow to the reader to reach a straightforward understanding of the subject, part by part. ... this book is very pleasant to read, well documented and can be seen as a very good introduction to the effects of irradiation on matter, or as a good references compilation for experimented readers." - Pauly Nicolas, Physicalia Magazine, Vol. 30 (1), 2008 “The text provides enough fundamental material to explain the science and theory behind radiation effects in solids, but is also written at a high enough level to be useful for professional scientists. Its organization suits a graduate level materials or nuclear science course... the text was written by a noted expert and active researcher in the field of radiation effects in metals, the selection and organization of the material is excellent... may well become a necessary reference for graduate students and researchers in radiation materials science.” - L.M. Dougherty, 07/11/2008, JOM, the Member Journal of The Minerals, Metals and Materials Society.

Download or read book Mathematical Contributions to the Theory of Evolution written by Karl Pearson and published by . This book was released on 1904 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: