Microstructure damage in silicon carbide fiber induced by 246.8-MeV Ar-ion irradiation

Microstructure characterizations of silicon carbide (SiC) fibers irradiated with 246.8-MeV Ar¹⁶⁺ at different fluences were investigated using transmission electron microscopy (TEM), Raman scattering spectroscopy and scanning electron microscopy (SEM). TEM results reveal that 3C-SiC grains were surrounded by the carbon ribbons. The size of 3C-SiC grains first decreases and then increases with increasing ion fluence. Raman spectra display that SiC fiber consists of both 3C-SiC and abundant graphite phase. A redshift of the vibration mode of 3C-SiC in the fibers occured as compared with that of standard bulk 3C-SiC. Meanwhile, 4H-SiC phase was observed after irradiation. Furthermore, scattering intensity of all peaks in Raman spectra first reduces and then increases with increasing ion fluence, indicating that damage accumulates at low fluences and subsequently recovers to some extent at higher fluences. SEM results exhibit that the diameter of SiC fibers first shrinks and then expands, simultaneously, carbon concentration on fibers surface decreases while silicon concentration increases gradually, with increasing ion fluence, accompanied by an adsorption of oxygen.