Elaboration and behavior under extreme irradiation conditions of nano- and micro-structured TiC

Titanium carbide samples were prepared by spark plasma sintering. Three different microstructures were prepared with average grain sizes of about 0.3, 1.3 and 25.0 μm. Each microstructure was irradiated with either 500 keV 40Ar+ ions or 800 keV 129Xe++ ions. The irradiation fluence varied from 6 × 1016 to 3.2 × 1017 at.cm−2. Irradiation was carried out at room temperature (RT) or at 1000 °C. Post-irradiation annealing was performed on some samples to follow the surface modification. In fact, clusters and nanocracks were observed at depth in the nanometric grains (<100 nm) whereas more extended cracks were found in larger grains (>1 μm). Microcracks can induce localized surface blistering after irradiation at RT and for the highest fluencies. The size, shape and density of the blisters were proposed to depend on the crystallographic orientation of each grain. The microstructure with sub-micrometric grains exhibited increased surface roughness after irradiation, with grain removal and grain boundary abrasion but no blistering. Surface blistering is not observed after irradiation at 1000 °C but the complete delamination of extended areas containing large grains occurs. In this article, we highlight the role played by gastight grain boundaries and porosity to explain the distinct behavior of microstructures.