Surface damage of Ti3SiC2 by MeV iodine bombardment

The damage produced by a 2 MeV iodine ion beam in MAX-phase Ti3SiC2 polycrystalline targets at room temperature has been studied at doses up to 3 x 10(15) ions cm(-2). The evolution of microstructure and induced defects of the irradiated sample with different doses was surveyed by combining grazing incident X-ray diffraction (GIXRD) using synchrotron radiation and variable energy positron beam analysis (PBA). With increasing irradiation dose, the crystallinity degrades gradually and leads to a combination of damaged Ti3SiC2 in combination with the precipitation of a Tic(x) phase. For high dose irradiation, a nano-dispersed Tic(x) phase becomes the dominant component. The PBA measurements indicate the formation of a new large vacancy-type defect that could be a cluster or void. The combination of GIXRD and PBA demonstrates that the damage of the MAX phase is more serious in the first 10 nm surface layer than that in the deeper layers closer to the final resting position of the projectile in the solid. The possible damage mechanisms have been discussed. (C) 2013 Elsevier B.V. All rights reserved.