Effect of neutron irradiation on select MAX phases

Herein we report on the effect of neutron irradiation – of up to 0.1 displacements per atom at 360(20)°C or 695(25)°C – on polycrystalline samples of Ti3AlC2, Ti2AlC, Ti3SiC2 and Ti2AlN. Rietveld refinement of X-ray diffraction patterns of the irradiated samples showed irradiation-enhanced dissociation into TiC of the Ti3AlC2 and Ti3SiC2 phases, most prominently in the former. Ti2AlN also showed an increase in TiN content, as well as Ti4AlN3 after irradiation. In contrast, Ti2AlC was quite stable under these irradiation conditions. Dislocation loops are seen to form in Ti2AlC and Ti3AlC2 after irradiation at 360(20)°C. The room temperature electrical resistivity of all samples increased by an order of magnitude after irradiation at 360(20)°C, but only by 25% after 695(25)°C, providing evidence for the MAX phases’ dynamic recovery at temperatures as low at 695(25)°C. Based on these preliminary results, it appears that Ti2AlC and Ti3SiC2 are the more promising materials for high-temperature nuclear applications.