Helium Induced Bubble Formation In Ultrafine And Nanocrystalline Tungsten Under Different Extreme Conditions
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Helium Induced Bubble Formation In Ultrafine And Nanocrystalline Tungsten Under Different Extreme Conditions
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Author :
language : en
Publisher:
Release Date : 2014
Helium Induced Bubble Formation In Ultrafine And Nanocrystalline Tungsten Under Different Extreme Conditions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Helium Bubble Formation In Ultrafine And Nanocrystalline Tungsten Under Different Extreme Conditions
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Author :
language : en
Publisher:
Release Date : 2014
Helium Bubble Formation In Ultrafine And Nanocrystalline Tungsten Under Different Extreme Conditions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover, at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.
Helium Nano Bubble Formation In Tungsten
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Author : Matt Thompson
language : en
Publisher: Springer
Release Date : 2018-08-01
Helium Nano Bubble Formation In Tungsten written by Matt Thompson and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-08-01 with Science categories.
This PhD thesis characterises the damage that occurs in tungsten when it is exposed to a fusion-like environment. The book presents pioneering work on the use of grazing-incidence small-angle X-ray scattering (GISAXS) to measure nano-bubble formation in tungsten exposed to helium plasma. The phenomenon of nanoscale bubble formation within metals during helium plasma exposure can lead to undesirable changes in the material properties, such as complex nanoscale surface modification or a reduction in thermal conductivity. As a result of this work, it is now possible to quantify how nanobubble behaviour changes within different materials, and under different plasma conditions. In 2015 the author published the first GISAXS study of helium-induced nanobubble formation in tungsten, demonstrating the viability of using GISAXS for this work. This paper has generated significant interest from the international fusion community and was selected as one of the highlights for the journal Nuclear Fusion.
Radiation Damage In Materials
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Author : Yongqiang Wang
language : en
Publisher: MDPI
Release Date : 2020-12-28
Radiation Damage In Materials written by Yongqiang Wang and has been published by MDPI this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-12-28 with Science categories.
The complexity of radiation damage effects in materials that are used in various irradiation environments stems from the fundamental particle–solid interactions and the subsequent damage recovery dynamics after the collision cascades, which involves multiple length and time scales. Adding to this complexity are the transmuted impurities that are unavoidable from accompanying nuclear processes. Helium is one such impurity that plays an important and unique role in controlling the microstructure and properties of materials used in fast fission reactors, plasma-facing and structural materials in fusion devices, spallation neutron target designs, actinides, tritium-containing materials, and nuclear waste. Their ultra-low solubility in virtually all solids forces He atoms to self-precipitate into small bubbles that become nucleation sites for further void growth under radiation-induced vacancy supersaturations, resulting in material swelling and high-temperature He embrittlement, as well as surface blistering under low-energy and high-flux He bombardment. This Special Issue, “Radiation Damage in Materials—Helium Effects”, contains review articles and full-length papers on new irradiation material research activities and novel material ideas using experimental and/or modeling approaches. These studies elucidate the interactions of helium with various extreme environments and tailored nanostructures, as well as their impact on microstructural evolution and material properties.
Surface Response Of Tungsten To Helium And Hydrogen Plasma Flux As A Function Of Temperature And Incident Kinetic Energy
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Author : Faiza Sefta
language : en
Publisher:
Release Date : 2013
Surface Response Of Tungsten To Helium And Hydrogen Plasma Flux As A Function Of Temperature And Incident Kinetic Energy written by Faiza Sefta and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Tungsten is a leading candidate material for the diverter in future nuclear fusion reactors. Previous experiments have demonstrated that surface defects and bubbles form in tungsten when ex- posed to helium and hydrogen plasmas, even at modest ion energies. In some regimes, between 1000K and 2000K, and for He energies below 100eV, "fuzz" like features form. The mechanisms leading to these surfaces comprised of nanometer sized tungsten tendrils which include visible helium bubbles are not currently known. The role of helium bubble formation in tendril morphology could very likely be the starting point of these mechanisms. Using Molecular dynamics (MD) simulations, the role of helium and hydrogen exposure in the initial formation mechanisms of tungsten "fuzz" are investigated. Molecular dynamics simulations are well suited to describe the time and length scales associated with initial formation of helium clusters that eventually grow to nano-meter sized helium bubbles. MD simulations also easily enable the modeling of a variety of surfaces such as single crystals, grain boundaries or "tendrils". While the sputtering yield of tungsten is generally low, previous observations of surface modification due to plasma exposure raise questions about the effects of surface morphology and sub-surface helium bubble populations on the sputtering behavior. Results of computational molecular dynamics are reported that investigate the influence of sub-surface helium bubble distributions on the sputtering yield of tungsten (100) and (110) surfaces induced by helium ion exposure in the range of 300 eV to 1 keV. The calculated sputtering yields are in reasonable agreement with a wide range of experimental data; but do not show any significant variation as a result of the pre-existing helium bubbles. Molecular dynamics simulations reveal a number of sub-surface mechanisms leading to nanometer- sized "fuzz" in tungsten exposed to low-energy helium plasmas. We find that during the bubble formation process, helium clusters create self-interstitial defect clusters in tungsten by a trap mutation process, followed by the migration of these defects to the surface that leads to the formation of layers of adatom islands on the tungsten surface. As the helium clusters grow into nanometer sized bubbles, their proximity to the surface and extremely high gas pressures can cause them to rupture the surface thus enabling helium release. Helium bubble bursting induces additional surface damage and tungsten mass loss which varies depending on the nature of the surface. We then show tendril-like geometries have surfaces that are more resilient to helium clustering and bubble formation and rupture. Finally, the study includes hydrogen to reveal the effect of a mixed 90%H-10%He plasma mix on the tungsten surface. We find that hydrogen greatly affects the tungsten surface, with a near surface hydrogen saturation layer, and that helium clusters still form and are attractive trapping sites for hydrogen. Molecular dynamics simulations have also investigated the effect of sub-surface helium bubble evolution on tungsten surface morphology. The helium bubble/tungsten surface interaction has been systematically studied to determine how parameters such as bubble shape and size, temperature, tungsten surface orientation and ligament thickness above the bubble impact bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom islands, craters and pinholes. The study provides insight into the mechanisms and conditions leading to various tungsten topology changes, most notably the formation of nanoscale fuzz. An atomistic study of the mechanisms behind initial phases of tungsten nano-fuzz growth has determined that tungsten surfaces are affected by sub-displacement energy helium and hydrogen fluxes through a series of mechanisms. Sub-surface helium atom clustering, bubble nucleation, growth and rupture lead to tungsten surface deformation. Helium clustering processes vary near grain boundaries or in tendril-like surface geometries. In the presence of hydrogen, these mechanisms are coupled with hydrogen surface saturation. Finally, further investigation to connect these atomistic mechanisms to nano-size tungsten fuzz growth is needed to get a comprehensive under- standing of the effects of low energy helium and hydrogen on tungsten.
Atomic Defects In Metals Atomare Fehlstellen In Metallen
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Author : H. Ullmaier
language : en
Publisher: Springer
Release Date : 1991-09-30
Atomic Defects In Metals Atomare Fehlstellen In Metallen written by H. Ullmaier and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991-09-30 with Science categories.
Atomic or point defects are disturbances of the periodicity of the crystal lattice extending over only a few atomic distances. Many physical and mechanical properties of solids are sensitive to their presence. Furthermore other defects which are crucial to material behaviour are influenced by their interaction with atomic defects. A detailed knowledge of production mechanisms and properties of point defects is therefore essential for assessing and for understanding the atomistic as well as the macroscopic behaviour of materials. As a result of the use of new research methods in recent years, such information is now available for almost all pure metals, for many dilute alloys and for some concentrated alloys. However, a critical and comprehensive collection of these data has so far been missing. The aim of the present volume is to close this gap by sifting, evaluating and compiling data on vacancies and self-interstitial atoms in solid metals. A chapter on the element helium is included because of the exeptional position of He as an "alloying" element and its role in radiation damage phenomena.
Laser Ablation In Liquids
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Author : Guowei Yang
language : en
Publisher: CRC Press
Release Date : 2012-02-22
Laser Ablation In Liquids written by Guowei Yang and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-02-22 with Science categories.
This book focuses on the fundamental concepts and physical and chemical aspects of pulsed laser ablation of solid targets in liquid environments and its applications in the preparation of nanomaterials and fabrication of nanostructures. The areas of focus include basic thermodynamic and kinetic processes of laser ablation in liquids, and its applic
Fundamentals Of Radiation Materials Science
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Author : GARY S. WAS
language : en
Publisher: Springer
Release Date : 2016-07-08
Fundamentals Of Radiation Materials Science written by GARY S. WAS and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-07-08 with Technology & Engineering categories.
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.
Advanced Techniques For Surface Engineering
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Author : W. Gissler
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-04-17
Advanced Techniques For Surface Engineering written by W. Gissler and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-17 with Technology & Engineering categories.
Today's shortages of resources make the search for wear and corrosion resistant materials one of the most important tasks of the next century. Since the surface of a material is the location where any interaction occurs, it is that there the hardest requirements on the material are imposed: to be wear resistant for tools and bearings; to be corrosion resistant for turbine blades and tubes in the petrochemical industry; to be antireflecting for solar cells; to be decorative for architectural panels and to combine several of these properties in other applications. Surface engineering is the general term that incorporates all the techniques by which a surface modification can be accomplished. These techniques include both coating and modification of the surface by ion implantation and laser beam melting. In recent years a continuously growing number of these techniques were developed to the extent that it became more and more difficult to maintain an overlook and to understand which of these highly differentiated techniques might be applied to resolve a given surface engineering problem. A similar development is also occuring for surface characterization techniques. This volume contains contributions from renowned scientists and engineers to the Eurocourse the aim of which was to inform about the various techniques and to give a comprehensive survey of the latest development on this subject.
Tungsten
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Author : Erik Lassner
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Tungsten written by Erik Lassner and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
Why does someone write a book about Tungsten? There are several reasons and precedents for this, the most important of which is that the last book on tungsten was written more than 20 years ago, in 1977, by St. W H. Yih and Ch T. Wang. During the intervening period there have been many new scientific and technological developments and innova tions, so it was not only our opinion but the view of many other members of the "tungsten family" that it was time to start writing a new book about tungsten. Preparations of the new book began in 1994. further impetus to the project was provided by the realization that in spite of this new knowledge having been presented at seminars or published in the technical press, a general acknowledgement of it by the majority of technicians and scientists is still far from being realized. It is our hope that this book will significantly contribute to a broader acceptance of recent scientific and technological innovations. An important prerequisite for such a project is the availability of a recently retired, experienced person willing to devote his time and talents to the tedious part of the exercise.