Speaker
Description
This study is dedicated to investigating the defects induced by gamma irradiation in zirconium carbide (ZrC) nanocrystals and their impact on the crystal structure using both theoretical and experimental approaches. Gamma irradiation was carried out at doses of 1500 and 3000 kGy, and the resulting changes were comprehensively analyzed using Positron Annihilation Spectroscopy (PAS), Raman spectroscopy, and Density Functional Theory (DFT). The results indicate that high-dose irradiation leads to the formation of carbon vacancies, which tend to combine with existing defects to form large vacancy clusters. PAS measurements revealed two lifetime components τ1 and τ2—indicating that positrons predominantly annihilate at defect sites, reflecting a high concentration of defects at nanoscale grain boundaries. DFT calculations confirmed that the formation energy of carbon vacancies is lower than that of zirconium vacancies, explaining their dominance in the defect structure. The changes observed in Raman spectroscopy—particularly the Sp2 C–C signal at 1795 cm-1 and the decrease in the intensity ratio of the D and G peaks—indicate amorphization of the structure and the formation of an oxide layer on the surface. At the same time, electron momentum distribution (EMD) analysis reveals that gamma irradiation leads to changes in electron density, primarily occurring within the carbon sublattice. Additionally, the impact on mechanical properties was evaluated, showing that the presence of vacancies reduces the Young’s modulus, while variations in the B/G ratio suggest an increase in the material’s brittleness [1].
As a result, this study demonstrates that gamma irradiation induces complex changes in the microstructure of ZrC, which are critically important for its radiation resistance and long-term operational stability [2]. The findings confirm that ZrC is a reliable candidate for applications under high-temperature and high-radiation conditions—particularly in nuclear energy systems such as TRISO fuel particles and gas-cooled reactors [3].
