Comparison of the proton irradiation-induced damage in SiCf/SiC with Sc-nitrate and Al2O3-Y2O3 sintering additives

We report microstructural evaluation in proton-irradiated SiCf/SiC up to a fluence level of 1018 p+/m2 (E = 20 MeV) performed at the Korea Multi-purpose Accelerator Complex (KOMAC). To fabricate the SiCf/SiC, a SiC-based matrix with two different sintering additives, Sc-nitrate and Al2O3-Y2O3, were infiltrated into the Tyranno® SiC preform by electrophoretic deposition and subsequent hot pressing. Scanning (SEM) and high resolution (HREM) electron microscopy was used to probe crack formation, pore generation and surface amorphization upon irradiation. SiC matrix was comparatively more crack-resistant in the SiCf/SiC with Sc-nitrate than that with Al2O3-Y2O3. Subsurface porosity evolved in the form of continuous bands for Al2O3-Y2O3 and discrete pockets for Sc-nitrate additives. Selective leaching of Si from the grain surface leads to the formation of a graded structure and surface amorphization. Irradiation-induced roughness on the fibers facilitates easy debonding at the SiCf-PyCcoating interface but no significant changes in the flexural behavior were observed.