Irradiation Damage Behavior and Mechanism of Pressureless-Sintered ZrC Ceramics

Zirconium carbide (ZrC) is a leading candidate for advanced nuclear reactor components due to its ultra-high melting point, thermomechanical stability, and low neutron absorption. However, its irradiation damage behavior and mechanism remains underexplored. In this work, dense pressureless-sintered ZrC ceramics with low-neutron-absorption MoSi₂ additives were irradiated with 500 keV He²⁺ ions at room temperature to peak damage levels of 0.30, 1.49, and 2.97 dpa. The changes in their microstructure, bonding states, and property were analyzed via TEM, GIXRD, Raman spectroscopy, nanoindentation, and TDTR. ZrC retained crystallinity regardless of high-density black-spot defects, while MoSi₂ exhibited severe amorphization and swelling. Lattice expansion and partial Zr-C bond breakage with C-C bond formation were confirmed, with maximum hardening at 1.49 dpa and significant elastic modulus reduction at 2.97 dpa. Thermal conductivity decreased modestly and showed minimal dose dependence, indicating a saturation effect. These results elucidate defect evolution in pressureless-sintered ZrC-MoSi₂ ceramics and support its application in high-irradiation nuclear environments.