In situ E-SEM and TEM observations of the thermal annealing effects on ion-amorphized 6H-SiC single crystals and nanophased SiC fibers

Hi Nicalon type S (HNS) SiC fiber and 6H-SiC single crystals have been irradiated with 4 MeV Au3+ at room temperature (RT) and to a fluence of 2 × 1015 cm−2. These irradiation conditions lead to the complete amorphization of the irradiated layer in both samples. Post-irradiation thermal annealing effect on the amorphized samples has been characterized in situ with both Environmental Scanning (E-SEM) and Transmission (TEM) Electron Microscopes. E-SEM observations reveal cracking and exfoliation of the amorphous layer in both samples for temperatures between 850 and 1000 °C. In parallel, TEM observations reveal recrystallization of the amorphous layer in both samples. Even though TEM thin foil specimens did not suffer mechanical failure during the tests, the good agreement between the recrystallization temperatures – 870 °C for the single crystal and 900 °C for the HNS fiber – place the recrystallization process as the stress source for the cracking and exfoliation phenomena. Crack detail of a Hi Nicalon type S SiC fiber triggered by the post-irradiation thermal annealing.