a b s t r a c tThanks to their refractoriness, carbides are sensed as fuel coating for the IVth generation of reactors. Among those studied, the Ti 3 SiC 2 ternary compound can be distinguished for its noteworthy mechanical properties: the nanolamellar structure imparts to this material some softness as well as better toughness than other classical carbides such as SiC or TiC. However, under irradiation, its behaviour is still unknown. In order to understand this behaviour, specimens were irradiated with heavy ions of different energies, then characterised. The choice of energies used allowed separation of the effects of nuclear interactions from those of electronic ones.

International audienceCarbide-type ceramics, which have remarkable thermomechanical properties, are sensed to manufacture the fuel cladding of Generation IV reactors that should work at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished from other materials by their ability to have some plasticity, even at room temperature. For this study, polycrystalline Ti3SiC2 was irradiated with ions of different energies, which allow to discriminate the effect of both electronic and nuclear interactions. After characterization by low-incidence X-ray diffraction and cross-sectional transmission electron microscopy, it appears that Ti3SiC2 is not sensitive to electronic excitations while nuclear shocks damage its structure. The results show the creation of many defects and disorder in the structure, an expansion of the hexagonal close-packed lattice along the c axis, and an increase in the microstrain yield

Low energy ion irradiation was used to investigate the microstructural modifications induced in Ti 3 SiC 2 by nuclear collisions. Characterization of the microstructure of the pristine sample by electron back-scatter diffraction (EBSD) shows a strong texturing of TiSi 2 , which is a common secondary phase present in Ti 3 SiC 2 . A methodology based on atomic force microscopy (AFM) was developed to measure the volume swelling induced by ion irradiation, and it was validated on irradiated silicon carbide. The swelling of Ti 3 SiC 2 was estimated to 2.2 ±0.8 % for an irradiation dose of 4.3 dpa at room temperature. Results obtained by both EBSD and AFM analyzes showed that nuclear collisions induce an anisotropic swelling in Ti 3 SiC 2 .

In the framework of the Generation IV International Forum, carbides are sensed for the design of the fuel cladding of the Gas-cooled Fast Reactor. Among the studied carbides, Ti 3 SiC 2 has the advantage of combining the properties of both metals and ceramics. After performing irradiations with 92 MeV Xe ions to 10 19 m -2 , hills were observed by AFM on the surface of Ti 3 SiC 2 . Such topographic modification seems to have never been observed in other materials irradiated in such conditions. A characterization of these hills by both XPS and X-TEM highlighted that these surface modifications do not appear in Ti 3 SiC 2 but in a native amorphous oxide layer on the sample. Moreover, the thickness of this oxide layer grows under irradiation. The comparison between different irradiations permitted to conclude that this surface modification is due to electronic interactions in this amorphous layer, and a threshold in electronic stopping power for hill formation is evidenced.