Mechanical properties of high-purity polycrystalline cubic SiC was characterized after neutron irradiation. Bar samples were irradiated in target position capsules in the High Flux Isotope Reactor (HFIR, Oak Ridge, Tennessee) to nominal fluence levels up to 7.7 dpa at temperatures of 300, 500, and 800°C. A decrease in Young's modulus was observed after irradiation, and its irradiation temperature dependence qualitatively agreed with the calculated modulus change due to point defect swelling. Irradiation caused a significant modification of statistical flexural strength but caused only minor increase in nano-indentation hardness. The irradiation effect on fracture initiation through an enhanced cleavage resistance likely is primarily responsible for the major change in flexural strength properties.
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.
Papers from The American Ceramic Society's 31st International Conference on Advanced Ceramics and Composites, held in Daytona Beach, Florida, January 21-26, 2007. Content includes fundamental links among processing, microstructure, properties and performance of ceramics and composites, and how these change as a function of time, temperature and environment. Reviews progress on ternary compounds, ultra-high temperature ceramics, innovative processing techniques to achieve multifunctional properties and materials for power generation and nuclear energy applications.
This volume is a compilation of papers presented in the Mechanical Behavior and Performance of Ceramics & Composites symposium during the 34th International Conference & Exposition on Advanced Ceramics and Composites (ICACC) held January 24-29, 2010, in Daytona Beach, Florida. The Mechanical Behavior and Performance of Ceramics & Composites symposium was one of the largest symposia in terms of the number (>100) of presentations at the ICACC’10. This symposium covered wide ranging and cutting-edge topics on mechanical properties and reliability of ceramics and composites and their correlations to processing, microstructure, and environmental effects. Symposium topics included: • Ceramics and composites for engine applications • Design and life prediction methodologies • Environmental effects on mechanical properties • Mechanical behavior of porous ceramics • Ultra high temperature ceramics • Ternary compounds • Mechanics & characterization of nanomaterials and devices • Novel test methods and equipment • Processing - microstructure - mechanical properties correlations • Ceramics & composites joining and testing • NDE of ceramic components
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.
Covering an important material class for modern applications in the aerospace, automotive, energy production and creation sectors, this handbook and reference contains comprehensive data tables and field reports on successfully developed prototypes. The editor and authors are internationally renowned experts from NASA, EADS, DLR, Porsche, MT Aerospace, as well as universities and institutions in the USA, Europe and Japan, and they provide here a comprehensive overview of current R & D with an application-oriented emphasis.
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.
Over 45 papers included in this collection present the latest advances in research and development on the processing, mechanics and mechanical properties of advanced ceramics and composites. The focus is on the underlying fundamental linkages between microstructure and properties, and the ability to achieve desired properties through innovative processing techniques including design, modeling, evaluation and life-prediction of structural components, ceramics and composites.
Swelling and microstructure of silicon carbide (SiC) are studied by means of MeV-range ion irradiation. The material used is chemical vapor deposited high purity polycrystalline cubic (3C)-SiC. The swelling behavior is characterized by precision interferometric profilometry following ion bombardment to the diamond-finished surface over a molybdenum micro-mesh. Irradiation was carried out at temperatures up to 873 K, followed by profilometry at room temperature. Microstructural characterization by means of cross-sectional transmission electron microscopy has also been finished for selected materials. Irradiation induced swelling was increased with increasing the displacement damage level up to 0.3 dpa at all evaluated temperatures. At 333 K, the swelling was increased with increasing the damage level up to 1 dpa, and irradiation-induced amorphization was observed over 1.07 dpa. At the higher irradiation temperature, swelling was saturated over 0.3 dpa. The temperature dependence of saturated swelling obtained so far appeared very close to the neutron irradiation data. For the study of the synergism of displacement damage and helium production, a dual-beam experiment was performed up to 100 dpa at 873 K. Swelling of the dual-beam irradiated specimen was larger than that of single-beam irradiated specimen. The result also suggested the onset of unsteady swelling in high He/dpa conditions after "saturated point defect swelling" is once achieved at displacement damage levels over 50 dpa.
