Cascade simulations in single crystal and nanocrystalline SiC were conducted in order to determine the role of grain boundaries and grain size on defect production during primary radiation damage. Cascades were performed with 4 and 10keV silicon as the primary knock-on atom. Total defect production was found to increase with decreasing grain size, and this effect was shown to be due to increased production in grain boundaries and changing grain boundary volume fraction. In order to consider in-grain defect production, a new mapping methodology was developed to properly normalize in-grain defect production rates for nanocrystalline materials. It was shown that the presence of grain boundaries does not affect the total normalized in-grain defect production significantly (the changes were lower than ~20%) for the knock-on atom energies considered. Defect production in the single grain containing the knock-on atom was also studied and found to increase for smaller grain sizes. In particular, for smaller grain sizes the defect production decreased with increasing distance from the grain boundary while for larger grain sizes the presence of the grain boundaries had a negligible effect upon defect production. The results suggested that experimentally observed changes in radiation resistance of nanocrystalline materials may be due to long-term damage evolution rather than changes in defect production rates from primary damage.

Effects of Grain Size and Grain Boundaries on Defect Production in Nanocrystalline 3C–SiC. N.Swaminathan, P.J.Kamenski, D.Morgan, I.Szlufarska: Acta Materialia, 2010, 58[8], 2843-53