Handbook of SiC properties for fuel performance modeling

Continuous SiC fiber, CVI SiC matrix composites for nuclear applications: Properties and irradiation effects

Current status and critical issues for development of SiC composites for fusion applications

Silicon carbide has enjoyed both fundamental study and practical application since the early days of nuclear materials science. In the past decade, with the increased interest in increasing efficiency, solving the real issues of waste disposal, and the constant mission to improve safety of nuclear reactors, silicon carbide has become even more attractive. The purpose of this paper is to discuss recent research that not only strives to understand the remarkable radiation stability of this material, but also the practical application of silicon carbide as waste form and for fission and fusion power applications.

Radiation effects in SiC for nuclear structural applications

Current status and recent research achievements in SiC/SiC composites

Microstructural development in cubic silicon carbide during irradiation at elevated temperatures

Irradiation creep of high purity CVD silicon carbide as estimated by the bend stress relaxation method

The influences of helium on microstructural development and dimensional stability in high purity � -SiC after Si 2þ -ion irradiation with and without He þ -ion injection at high temperature were studied. The microstructural observations of � -SiC irradiated up to 10 dpa at irradiation temperatures of 1073, 1273, and 1673 K were performed by transmission electron microscopy, respectively. ‘Black spot’ defects and dislocation loops were observed densely in all irradiated � -SiC. Small cavities were formed at grain interior of � -SiC above 1273 K. Helium increased the number density of cavities, but helium dose not effect on the cavity size. Swelling in � -SiC irradiated up to 3 dpa at 1273 K was measured by precision-surface profilometry. The influences of damage rate (dpa/s) and helium on the swelling were studied. The swelling values were saturated above 1 dpa after single-ion and dual-ion irradiation under higher dpa/s condition (1:0 � 10 � 3 dpa/s). In lower dpa/s case (5:0 � 10 � 5 dpa/s), the swelling was also saturated after single-ion irradiation, but the saturated swelling value was approximately half of the higher dpa/s case. On the contrary, the swelling value of � -SiC irradiated with dual-ion under the lower dpa/s condition increased at 3 dpa without saturation. Small cavities observed in this specimen, which were formed on {111} family planes, may cause the enhanced swelling at 3 dpa.

Synergistic Effects of Heavy Ion and Helium Irradiation on Microstructural and Dimensional Change in β-SiC

Unidirectional SiC/SiC composites fabricated with highly-crystalline and stoichiometric fibers and matrix, but with three different interfacial types (single-layer pyrolytic carbon (PyC), multilayered SiC/PyC, and pseudo porous SiC interfaces) were irradiated up to 1.0 × 1025 n/m2 (E > 0.1 MeV) at 1073 and 1273 K. Tensile, inter-laminar shear, and flexural properties were evaluated to compare the role of different interfaces on neutron irradiation behavior. There was nearly no significant degradation in tensile and flexural strength after high-temperature neutron irradiation, except for porous SiC interphase composite. Moreover, no meaningful reduction of tensile modulus was identified regardless of interphase types, although 20–40% degradation in flexural moduli occurred due to a reduction in inter-laminar shear modulus. In contrast, matrix cracking stress was significantly dependent on interfacial properties. Multilayer interphase composites exhibited the best irradiation stability. Irradiation instability of thick PyC and porous SiC interphase resulted in 20% and 40% degradations of matrix cracking stress, respectively.

Tensile, Flexural, and Shear Properties of Neutron Irradiated SiC/SiC Composites with Different Fiber-Matrix Interfaces

Dense SiC ceramics fabricated by NITE process (NITE-SiC), using SiC nano-powder, were subjected to exposure tests from 1000 to 1800 � C in an argon-oxygen gas mixture with an oxygen partial pressure of 0.1 Pa. The thermal stability of NITE-SiC was examined through mass change, 3-point bending test, XRD analysis and TEM/SEM observation. The NITE-SiC presented excellent bending strength (above 800 MPa) up to � 1800 � C while the conventional liquid-phase sintered SiC ceramics (LPS-SiC), using SiC sub-micron powder, indicated severe degradation at 1300 � C due to volatilization and softening of amorphous grain boundary phase. The in situ 3-point bending test at 1300 � C was carried out to evaluate in-service fracture behavior, where excellent improvements in bending strength, elastic modulus and fracture behavior were confirmed, compared with the conventional LPS-SiC. These are interpreted by the modification with reduction and crystallization of grain boundary phase (Y3Al5O12). The decomposition of Y3Al5O12 were caused by the reactions with CO gas on the surface of NITE-SiC exposed at 1800 � C, but the severe degradation was not identified in strength.

Akira Kohyama

Papers

Microstructural development in cubic silicon carbide during irradiation at elevated temperatures

Irradiation creep of high purity CVD silicon carbide as estimated by the bend stress relaxation method

Synergistic Effects of Heavy Ion and Helium Irradiation on Microstructural and Dimensional Change in β-SiC

Tensile, Flexural, and Shear Properties of Neutron Irradiated SiC/SiC Composites with Different Fiber-Matrix Interfaces

High-temperature mechanical property improvements of SiC ceramics by NITE process