27pB03
高線量中性子照射後の原子力グレードSiC/SiC複合材料の強度特性と微細組織
Mechanical Properties and Microstructures of Nuclear-grade SiC/SiC Composites
after High Dose Irradiation
小沢和巳、小柳孝彰1、野澤貴史、加藤雄大1、近藤創介2、谷川博康、Lance L. Snead1
Kazumi OZAWA, Takaaki KOYANAGI1, Takashi NOZAWA, Yutai KATOH1, Sosuke KONDO2,Hiroyasu TANIGAWA, Lance L. Snead1
原子力機構、ORNL1、京大エネ研2
JAEA、ORNL1、Institute of Advanced Energy, Kyoto University2~50% degradation of proportional limit stress andultimate flexural strength was observed for thecomposite irradiated at 629°C, while the one
irradiated at 319°C exhibited brittle behavior, as
shown in Fig. 1. In the ion-experiment results,
shrinkage of the HNLS fiber was observed forspecimens irradiated at 300 and 600°C to 100 dpa.
The FE-TEM results, EELS analysis and ourprevious work suggest that the shrinkage would be
result of ballistic mixing and transport of excesscarbon atoms from the intergranular phase into SiC
grains, and resulting production of excess CSi
antisites [S. Kondo et al. Acta Mater. 83 (2015) 1].
This work was partly supported by the Office ofFusion Energy Sciences, U.S. Department ofEnergy, under contracts DE-AC05-00OR22725
with UT-Battelle, LLC, and NFE-10-02779 for theJAEA-DOE Collaboration. This paper has been
also prepared as an account of work assigned to theJapanese Implementing Agency under theProcurement Number IFERC-T1PA03-JA withinthe “Broader Approach Agreement” between theGovernment of Japan and the European Atomic
Energy Community.
600
UnirradiatedFlexural stress [MPa]Silicon carbide fiber-reinforced silicon carbide
matrix (SiC/SiC) composites are promising
candidate materials for advanced fusion reactorblankets (eg. DEMO) owing to its excellent
thermo-mechanical / -chemical properties andintrinsic irradiation tolerance.
The irradiation
responseofhighly-crystalline
andnear-stoichiometric SiC fiber has been assumed tobe the same as that of high purity monolithic β-SiC.
Unfortunately, based on recent data this assumption
appears not to be correct [Katoh, et al. J. Nucl.
Mater. 462 (2015) 450]. In the case of high dose
irradiation, SiC/SiC composites reinforced with oneof the “nuclear-grade” fibers (Hi-Nicalon™ Type S(HNLS)) irradiated to 70 dpa at various irradiation
temperatures, undergo a moderate to significant
drop in the ultimate tensile strength depending on
the irradiation temperature. The degradation is
primarily attributed to fiber deterioration, thoughdetails remain unclear. The current study mainly
aims to investigate mechanical and microstructuralchanges in the SiC/SiC composite after neutron
irradiation to higher dose.
Materials for the present study include
plain-weave HNLS composites produced via thechemical vapor infiltration process with themultilayered interface of (PyC20 nm/SiC100 nm)5sequence. Neutron irradiation was conducted in
the HFIR at ORNL. The peak neutron fluence
was ~1.0 × 1026 n/m2 (E > 0.1 MeV, equivalent to~100 dpa) at nominal irradiation temperatures of319 and 629°C. Post irradiation experiments
included 1/4-four-point flexural tests (size:6.3×2.8×62.8 mm) and SEM observations.
Parallel, ion irradiation tests at DuET and TIARA
facilities were used for comparison.
Ionirradiation dose was ~100 dpa and temperatures 300
and 600°C. FE-TEM microscopy and EELS wereused for microstructural evaluations.
In the post neutron irradiation experiments,

500

Size: 6.3*2.8*62.8 mm
20 mm

40040 mm300319°C
100 dpa

200629°C
100 dpa

100
000.2

0.4 0.6 0.8 1 1.2 1.4
Flexural strain [%]Fig.1 Flexural stress-strain curves. Curves areoffset for visible purpose.