Abstract
The microstructures of SiCf/SiC composites irradiated with 400 keV C+ and then 200 keV He+ at 633 K and annealed post-irradiation at 1073, 1273, and 1473 K for 5 h were analyzed. The SiCf/SiC composites were composed of nanocrystal SiC fibers with 5–25 μm in size, SiC matrix with a columnar crystal structure, and six transition layers (alternate distribution of pyrolytic carbon and SiC layers) between them. Several fine microcracks induced by irradiation appeared at the interfaces and grew during annealing. An irradiation band with a few helium bubbles was formed in the SiC fiber and had a width of approximately 260 nm, which decreased with increase in annealing temperature. Annealing caused the irradiation-induced bubbles to grow and induced a linear arrangement of the bubbles in the SiC fiber. Larger He bubbles were generated at the grain boundary and tended to form microcracks in the SiC matrix. Irradiation did not cause obvious amorphization at 633 K and annealing did not induce nanograin growth. After irradiation, the area fraction and size of carbon packets with graphitic nature in the SiC fiber decreased.
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