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The Effects of Displacement Damage and
Transmutation Atoms on Microstructure of SiC:
The Effects of H Atom on Dimensional Change of SiC
T. Nozawa a) , T. Taguchi b) and H. Tanigawa a)
a) Division of Fusion Energy Technology, FRDD, JAEA,
b) Neutron Material Research Center, QuBS, JAEA
A SiC/SiC composite is a candidate for fusion structural
material due to the inherently good irradiation resistance of
1, 2)
SiC itself . Specifically, a dense and robust nanoinfiltration
transient-eutectic-phase sintered (NITE) SiC/SiC
composite is believed to be viable due to potential high
competitiveness. However, irradiation tolerance of NITE
composites, which contain secondary phases composed of
sintering aids, is somehow questionable considering the fact
of irradiation-induced degradation for SiC with impurities 1) .
In contrast, for the practical application, understanding the
synergistic effects of He and H as transmutation products of
a fusion reactor on microstructural evolution of SiC under
irradiation is important. For instance, applying the triple
ion beam irradiation by the TIARA facility, the significance
of H on the He bubble formation was identified for pure
3)
SiC . However, this effect on SiC with impurities is
presently uncertain. This study primarily aims to identify
the effects of displacement damage and transmutation atoms
(He and H) on microstructure of SiC with sintering aids.
A NITE-SiC ceramic as representative matrix phase of
NITE-SiC/SiC composites was tested. The sintering aids
were Al2O3 and Y2O3. Triple ion beam (Si 2+ , He + and H + )
irradiation was carried out up to 10 dpa at 1,000 ºC. A
constant He/dpa ratio of 130 appm/dpa and varied H/dpa
ratios of 0, 40 and 130 appm/dpa were applied. Figure 1
shows the calculated depth profiles of displacement damage
and He, H and Si concentration. The radiation-induced
dimensional change was then evaluated by the step-height
measurement by the atomic force microscopy (Fig. 2). The
4)
detail of this technique was descrived elesewhere .
Figure 3 shows radiation-induced dimensional change as
Fig. 1 Displacement damage, He, H and Si concentration
as a function of depth from the surface in SiC calculated
by SRIM code.
JAEA-Review 2010-065
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Fig. 2 Example of the step-height swelling measurement
by the atomic force microscopy.
appmHe/dpa = 130
T irr. = 1000ºC
Hydrogen Implantation Ratio [appmH/dpa]
Fig. 3 The effect of H/dpa on dimensional change of SiC
under triple ion beam (Si 2+ , He + and H + ) irradiation.
a function of the H/dpa ratio. Considering data scatter, it is
speculated that the effect of the H/dpa ratio on the
radiation-induced dimensional change of NITE-SiC was
neglegibly small. However, for ~10 dpa, the amount of
implanted H was very little to form He bubbles, which
impact the magnitude of radiation-induced dimensional
change. Further evaluation is, therefore, required to
conclude this. The detailed analysis of the synergestic
effects on microstructure of NITE-SiC is being continued.
References
1) L.L. Snead et al., J. Nucl. Mater. 371 (2007) 329.
2) T. Nozawa et al., J. Nucl. Mater. 386-388 (2009) 622.
3) T. Taguchi et al., J. Nucl. Mater. 367-370 (2007) 698.
4) Y. Katoh et al., Mater. Trans. 43 (2002) 612.