- William Alexander Hanson, The University of Tennessee, Knoxville
The Mn+1AXn phases are promising candidates for several nuclear applications due to their high thermal conductivity, high-temperature structural stability, and low neutron absorption cross section. Numerous ion and neutron irradiation studies have demonstrated apparent resistance to irradiation-induced structural damage in the Ti3SiC2 composition; however, comparison between these two irradiation environments is not fully understood for this material. In order to deconvolute the influences of electronic and nuclear stopping, 9 MeV Ti-ion irradiations were conducted at room temperature at The University of Tennessee Ion Beam Materials Laboratory. A systematic exploration of the effects of varying energy deposition at comparable damage doses, utilizing grazing incidence x-ray diffraction and transmission electron microscopy, revealed that inelastic energy dissipation is a major contributor to damage evolution in this material system. There is an electronic stopping threshold above which increases in electronic energy loss result in increasing c/a ratio and increases in an FCC-phase formation. No apparent damage was observed in regions below this threshold, although local damage dose was significantly higher in these regions, demonstrating the effects above the threshold are dose (dpa) independent. The individual stopping effects have been further separated following a sequential irradiation study, and a series of mechanisms are proposed to describe how energy dissipation affects the damage evolution.