Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites

Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites

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Publisher:

Published: 2007

Total Pages:

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The effects of fast neutron irradiation on SiC and SiC composites have been studied. The materials used were chemical vapor deposition (CVD) SiC and SiC/SiC composites reinforced with either Hi-Nicalon{trademark} Type-S, Hi-Nicalon{trademark} or Sylramic{trademark} fibers fabricated by chemical vapor infiltration. Statistically significant numbers of flexural samples were irradiated up to 4.6 x 1025 n/m2 (E>0.1 MeV) at 300, 500 and 800 C in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Dimensions and weights of the flexural bars were measured before and after the neutron irradiation. Mechanical properties were evaluated by four point flexural testing. Volume increase was seen for all bend bars following neutron irradiation. Magnitude of swelling depended on irradiation temperature and material, while it was nearly independent of irradiation fluence over the fluence range studied. Flexural strength of CVD SiC increased following irradiation depending on irradiation temperature. Over the temperature range studied, no significant degradation in mechanical properties was seen for composites fabricated with Hi-Nicalon{trademark} Type-S, while composites reinforced with Hi-Nicalon{trademark} or Sylramic fibers showed significant degradation. The effects of irradiation on the Weibull failure statistics are also presented suggesting a reduction in the Weibull modulus upon irradiation. The cause of this potential reduction is not known.


High Dose Neutron Irradiation of Hi-Nicalon Type S Silicon Carbide Composites, Part 1

High Dose Neutron Irradiation of Hi-Nicalon Type S Silicon Carbide Composites, Part 1

Author:

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30 40 dpa at temperatures of 300 800 C. However, more recent studies of these same fiber composites irradiated to damage levels of>70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 C. Here, electron microscopy is used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 C, substantial microstructural evolution is observed in those irradiated at 300 C. Specifically, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.


High Dose Neutron Irradiations of Hi-Nicalon Type S Silicon Carbide Composites, Part 1

High Dose Neutron Irradiations of Hi-Nicalon Type S Silicon Carbide Composites, Part 1

Author:

Publisher:

Published: 2014

Total Pages: 7

ISBN-13:

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Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30-40 dpa at temperatures of 300-800 °C. However, more recent studies of these same fiber composites irradiated to damage levels of >70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 °C. Here, electron microscopy is used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 °C, substantial microstructural evolution is observed in those irradiated at 300° C. Furthermore, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.


Fracture Toughness Evaluation of Neutron-Irradiated Composites by a Miniaturized Charpy Test

Fracture Toughness Evaluation of Neutron-Irradiated Composites by a Miniaturized Charpy Test

Author: K. Hamada

Publisher:

Published: 1993

Total Pages: 13

ISBN-13:

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The impact properties of advanced metal matrix composites (MMCs) such as unidirectionally reinforced silicon carbide (SiC)/aluminum (Al) and C/Al have been investigated based on recent improvements in their mechanical properties. This paper details the effects of test temperature and neutron irradiation on the fracture toughness of these MMCs. The materials used were sheets of PCS-SiC/Al and PAN-C/Al. Miniaturized Charpy V-notched specimens were tested in an instrumented Charpy impact tester. Neutron irradiation was performed in the Japanese Materials Testing Reactor (JMTR), a light water reactor (LWR) at Oarai. The fracture energy increased with increasing test temperature and with neutron irradiation. SiC/Al was rather more insensitive to neutron fluence than C/Al, which was related to the difference in interfacial structure between the two systems.


Radiation Effects in Silicon Carbide

Radiation Effects in Silicon Carbide

Author: A.A. Lebedev

Publisher: Materials Research Forum LLC

Published: 2017

Total Pages: 172

ISBN-13: 1945291117

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The book reviews the most interesting research concerning the radiation defects formed in 6H-, 4H-, and 3C-SiC under irradiation with electrons, neutrons, and some kinds of ions. The electrical parameters that make SiC a promising material for applications in modern electronics are discussed in detail. Specific features of the crystal structure of SiC are considered. It is shown that, when wide-bandgap semiconductors are studied, it is necessary to take into account the temperature dependence of the carrier removal rate, which is a standard parameter for determining the radiation hardness of semiconductors. The carrier removal rate values obtained by irradiation of various SiC polytypes with n- and p-type conductivity are analyzed in relation to the type and energy of the irradiating particles. The influence exerted by the energy of charged particles on how radiation defects are formed and conductivity is compensated in semiconductors under irradiation is analyzed. Furthermore, the possibility to produce controlled transformation of silicon carbide polytype is considered. The involvement of radiation defects in radiative and nonradiative recombination processes in SiC is analyzed. Data are also presented regarding the degradation of particular SiC electronic devices under the influence of radiation and a conclusion is made regarding the radiation resistance of SiC. Lastly, the radiation hardness of devices based on silicon and silicon carbide are compared.


Ceramic Matrix Composites

Ceramic Matrix Composites

Author: Narottam P. Bansal

Publisher: John Wiley & Sons

Published: 2014-10-27

Total Pages: 725

ISBN-13: 1118832892

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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.


Handbook of Ceramic Composites

Handbook of Ceramic Composites

Author: Narottam P. Bansal

Publisher: Springer Science & Business Media

Published: 2006-08-25

Total Pages: 547

ISBN-13: 0387239863

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This valuable handbook has been compiled by internationally renowned researchers in the field. Each chapter is focused on a specific composite system or a class of composites, presenting a detailed description of processing, properties, and applications.


Quantitative EPR

Quantitative EPR

Author: Gareth R. Eaton

Publisher: Springer Science & Business Media

Published: 2010-04-10

Total Pages: 192

ISBN-13: 3211929487

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There is a growing need in both industrial and academic research to obtain accurate quantitative results from continuous wave (CW) electron paramagnetic resonance (EPR) experiments. This book describes various sample-related, instrument-related and software-related aspects of obtaining quantitative results from EPR expe- ments. Some speci?c items to be discussed include: selection of a reference standard, resonator considerations (Q, B ,B ), power saturation, sample position- 1 m ing, and ?nally, the blending of all the factors together to provide a calculation model for obtaining an accurate spin concentration of a sample. This book might, at ?rst glance, appear to be a step back from some of the more advanced pulsed methods discussed in recent EPR texts, but actually quantitative “routine CW EPR” is a challenging technique, and requires a thorough understa- ing of the spectrometer and the spin system. Quantitation of CW EPR can be subdivided into two main categories: (1) intensity and (2) magnetic ?eld/mic- wave frequency measurement. Intensity is important for spin counting. Both re- tive intensity quantitation of EPR samples and their absolute spin concentration of samples are often of interest. This information is important for kinetics, mechanism elucidation, and commercial applications where EPR serves as a detection system for free radicals produced in an industrial process. It is also important for the study of magnetic properties. Magnetic ?eld/microwave frequency is important for g and nuclear hyper?ne coupling measurements that re?ect the electronic structure of the radicals or metal ions.


Neutron Irradiation Effects on High Nicalon Silicon Carbide Fibers

Neutron Irradiation Effects on High Nicalon Silicon Carbide Fibers

Author:

Publisher:

Published: 1996

Total Pages: 4

ISBN-13:

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The effects of neutron irradiation on the mechanical properties and microstructure of SiC and SiC-based fibers is a current focal point for the development of radiation damage resistant SiC/SiC composites. This report discusses the radiation effects on the Nippon Carbon Hi-Nicalon{trademark} fiber system and also discusses an erratum on earlier results published by the authors on this material. The radiation matrix currently under study is also summarized.