Mechanical properties of neutron irradiated SiC fibers (original) (raw)
Related papers
Fusion Engineering and Design, 2005
A high fluence irradiation of SiC f /SiC composites has been performed to study the effect of neutron irradiation on the mechanical and physical behaviour of those composites. The fibre reinforced silicon carbide composites have been irradiated at two temperature levels of 600 • C and 900 • C up to a fluence of 3.5 × 10 25 n/m 2 (E > 0.1 MeV). The stiffness of the bending bars after irradiation changed with factors between 0.75 and 1.04 for the different composites while the bending strength after irradiation was reduced with a factor of 2 in some cases. The laser flash thermal diffusivity ratio's (α irr /α o) of the composites measured at 600 • C are from 0.1 to 0.5 and from 0.25 to 0.75 for an irradiation temperature of 600 • C and 900 • C, respectively. The dimensional changes observed are small.
Neutron Irradiation Swelling of SiC and SiCf/SiC for Advanced Nuclear Applications
Energy Procedia, 2015
Silicon carbide (SiC) is used as a layer in TRISO fuel of high temperature gas-cooled reactors because of its excellent thermal and mechanical properties. SiC fiber-reinforced SiC composites (SiC f /SiC) are also a candidate material for structural material for fusion reactor blanket and cladding materials of advance fission reactors. In this research, seven of monolithic SiC or SiC f /SiC composites materials with different fabrication processes were irradiated in the BR2 reactor up to a fluence of 2.0-2.5×10 24 (E>0.1 MeV) at 333-363 K. Changes in macroscopic lengths and lattice parameters before and after the neutron irradiation were measured. Furthermore, microstructure of SiC f /SiC composites was investigated using a scanning electron microscope, too. Results showed that after the neutron irradiation, the group of SiC and SiC f /SiC composites were swelled approximately 1.24~1.33% and 1.00~1.19% in length, respectively. Apparently the presence of fibers resulted in smaller swelling. It may be attributed for smaller swelling of SiC fibers. Further difference in swelling may be caused by the presence of different sintering additives.
Behaviors of SiC fibers up to high temperature
Owing to progress in the manufacturing on SiC fibers, the mechanical and thermal behaviors of SiCf/SiCm composites have been sharply improved. Besides, regarding their physical and chemical properties and their stability under irradiation, SiC/SiC composites are potential candidates for nuclear applications in advanced fission (Generation IV) and fusion reactors (ITER). CEA must characterize and optimize them before their uses in reactors. In order to study these materials, CEA is developing a multi-scale modeling from fibers to bulk composite specimens. In this approach, the fiber behaviors must firstly be well known. The purpose of this paper is to present a review of the studies led by the CEA about the behaviors of SiC fibers. Thus, CEA has developed a specific device, named MecaSiC, for tensile testing single fibers up to high temperature.
Postirradiation fiber debonding and pull-out in SiC-SiC composites
Journal of Nuclear Materials, 1994
The toughness of ceramic matrix composites is contributed by crack bridging, matrix crack deflection, fiber debonding and pull-out and other minor effects. Crack bridging relies on fibers being intact close to the crack tip, while pull-out toughening relies on the debonding and frictional characteristics of the fiber-matrix interface. The interface friction depends on the interface pressure (i.e., on misfit strains) and interface roughness. In this paper, a calculational model for postirradiation fiber debonding and pull-out toughness in Sic-Sic composites is presented. It is shown that fiber debonding and pull-out toughness in Sic-Sic composites vary significantly with neutron fluence and irradiation tem~rature, which is a direct wnsequen~ of the dependence of the misfit strain on these irradiation variables. * This material is based upon work supported by the US Department of Energy under award number DE-FGO3-91ER.54115.
Characterization of ion-irradiation effects on third generation SiC fibers
2015
The objective of the present work is to study the irradiation effects on third generation SiC fibers which fulfill the minimum requisites for nuclear applications, i.e. Hi-Nicalon type S, hereafter HNS, and Tyranno SA3, hereafter TSA3. With this purpose, these fibers have been ionirradiated with 4 MeV Au ions at RT and increasing fluences. Irradiation effects have been characterized in terms of micro-Raman Spectroscopy (µRS) and Transmission (TEM) and compared to the response of the as-irradiated model material, i.e. 6H-SiC single crystals. It is reported that ion-irradiation induces amorphization in SiC fibers. Ion-amorphization kinetics between these fibers and 6H-SiC single crystals are similar despite their different microstructures and polytypes with a critical amorphization dose of ~3×10 14 cm-2 (~0.6 dpa) at RT. Also, thermally annealing induced cracking is studied via in-situ Environmental Scanning Electron Microscopy (E-SEM). The temperatures at which the first cracks appear as well as the crack density growth rate increase with increasing heating rates. The activation energy of the cracking process yields 1.05 eV in agreement with recrystallization activation energies of ion-amorphized samples.
Radiation Damage Parameters for SiC/SiC Composite Structure in Fusion Nuclear Environment
Fusion Science & Technology, 2003
The radiation effects in the fiber, matrix, and interface components of the SiC/SiC composite material are important input for lifetime assessment. Neutronics calculations were performed to determine the radiation damage parameters in the fiber/matrix and the candidate interface materials. The radiation damage parameters were calculated for both the carbon and silicon sublattices. The radiation damage parameters were evaluated for representative candidate breeding blankets. The breeder and/or coolant such as Pb 83 Li 17 , Flibe and Li 2 O affect the radiation damage parameters by impacting the neutron spectrum. The results provide an essential input for SiC/SiC composite lifetime assessment. The impact of the unique features of inertial fusion systems on damage parameters are identified.
Phenomenological Inelastic Constitutive Equations for SiC and SiC Fibers Under Irradiation
Fusion Technology, 1994
Experimental data on irradiation-induced dimensional changes and creep in beta-silicon carbide (SiC) and SiC fibers are analyzed with the objective of studying the constitutive behavior of these materials under high-temperature irradiation. The data analysis includes the empirical representation of irradiation-induced dimensional changes in an SiC matrix and SiC fibers as functions of time and irradiation temperature. The analysis also includes the formulation of simple scaling laws to extrapolate the existing data to fusion conditions on the basis of the physical mechanisms of radiation effects on crystalline solids. Inelastic constitutive equations are then developed for SCS-6 SiC fibers, Nicalon fibers, and chemical vapor deposition SiC. The effects of applied stress, temperature, and irradiation fields on the deformation behavior of this class of materials are simultaneously represented. Numerical results are presented for the relevant creep functions under the conditions of the fusion reactor (ARIES IV) first wall. The developed equations can be used in estimating the macromechanical properties of SiC-SiC composite systems as well as in performing a timedependent micromechanical analysis that is relevant to slow crack growth and fiber pullout under fusion conditions.
Ion irradiation effects on third generation SiC fibers in elastic and inelastic energy loss regimes
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014
Third generation silicon carbide fibers, mainly Hi-Nicalon Type S and Tyranno SA3, have improved the irradiation resistance of silicon carbide composites. In this work the microstructural evolution of these fibers due to ion irradiation is investigated in terms of Raman micro-spectrometry. In comparison with a 6H-SiC single crystal, similar amorphization kinetics have been found for increasing fluences of 4-MeV Au 3+ ions. Also, in situ tensile tests have been performed to these micrometric fibers that allow real time tracking of their strain behavior under different in-core-like conditions. Tyranno SA3 fibers have been irradiated with 12-MeV C 4+ at 300 MPa at RT and 1000°C revealing a high influence of the irradiation temperature on the fiber residual strain.
Journal of Nuclear Materials, 2022
In order to apply SiC/SiC composites in nuclear systems, it is essential to understand the potential effects of dimensional changes induced by neutron irradiation on property degradation. A microscale model has been developed to predict the mechanical behaviour of irradiated fibre composites, including matrix cracking and interface debonding. The present work investigated the states of residual stresses and damage that may be induced by swelling mismatch between fibres and matrix, and their subsequent effects on the transverse and longitudinal tensile mechanical properties of composites. Unidirectional (UD) composites with various fibre contents and porosities were subject to different swelling mismatch to simulate irradiation-induced dimensional changes. The composites were then virtually tested in tension to determine the modulus and strength. The focus of the present work is the transverse properties, and some illustrative results for the longitudinal behaviour are also presented. The sensitivity of the composites' properties to irradiation swelling was affected by the fibre volume fraction, and not by the pore volume fraction, though the porosity dramatically affected the initial unirradiated properties. The model correctly describes experimental trends reported in the literature, and a simple optimisation of the model parameters is demonstrated by the successful simulation of experimental data for tensile loading of a mini composite specimen.
Au ion irradiation of various silicon carbide fiber-reinforced SiC matrix composites
Journal of Nuclear Materials, 2013
Silicon carbide fiber-reinforced SiC matrix composites are promising candidates as fuel cladding for several concepts of Generation IV reactors and as structural materials for fusion reactors. The composites used in this study were composed of a SiC matrix obtained by chemical vapor infiltration associated with various fiber types (Tyranno Type-S, Tyranno SA Grade-3 and Hi-Nicalon Type-S) and with a PyC layer as the interphase. 12 MeV Au ions were used for irradiation up to 0.05 and 1 displacement per atom (dpa) fluences at room temperature and 800°C. Analysis of both microstructure and composition of composites were performed by scanning electron microscopy (SEM), electron probe microanalysis and Raman spectroscopy. At room temperature and low fluence, Raman spectroscopy results showed that irradiation induces a disordered/distorted state into fibers and matrix. With increasing fluence, a total amorphization of these constituents occurs. The increase in the irradiation temperature leads to a damage recovery and partial recrystallization of samples. Image analysis performed from SEM micrographs highlights no significant change in fiber diameter and shape. However, SEM analysis suggests a longitudinal shrinkage of Tyranno Type-S fibers for the composite irradiated at 1 dpa at room temperature and 800°C. These results are in complete agreement with conclusions from neutron irradiations suggesting an appropriate relevance of irradiations with 12 MeV Au.