The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

493 / 2019-03-18 21:10:41

H/He co-irradiation induced structural modification and the evolution of irradiations in Li4SiO4

irradiation,bubble evolution,tritium breeder

Plenary track > Laser and Particle Beam Fusion

Lithium orthosilicate (Li4SiO4) is considered as leading candidate material for tritium breeders employed in the nuclear fusion reactors. In tritium breeding reaction, Li4SiO4 is attacked by energetic 4He and T particles generated via nuclear reaction, thus causes severe damage in matrix. The formation and evolution of defects induced by irradiation are significantly related to the microstructural change and gas bubbles’ behavior in Li4SiO4. In addition, helium atoms tend to concentrated in the lattice of Li4SiO4 as bubbles, meanwhile the bubbles can be absorber of other atoms to grow with time and temperature. The parameters, like shape, size distribution and migration behavior of bubbles, thus had important implications for evaluating the irradiation-induced aging effects in material. However, the present results are based on the experiments with single irradiation particles. To better understand the irradiation effects of Li4SiO4 in simulation experiment for neutron radiation environment, multiple particles irradiation should be considered.
In this work, the microstructural change of Li4SiO4 with different H+ and He2+ co-irradiation doze was well evaluated. Results suggest that H and He ions stay at interstitial sites of the host lattice after implantation, thus causes significant lattice swelling, and the lattice parameter increases with the increase of radiation doze. At the doze of 1017 ions/cm2(32 dpa), the crystallinity decreases because of the degradation of SiO4. The irradiated layer is found to be amorphous, and gas bubbles with mean diameter of 1.9 nm are formed. Further, in-situ TEM observations indicate that coarsening of gas bubbles is both time and temperature, which follows Migration-coalescence(MC) mechanism dominates the growth of bubbles in Li4SiO4 at relative low temperature. This work provides evidence of estimating the swelling, meanwhile, it shows the suitability of in-situ TEM experiments to study the behavior of gas bubbles in other kinds of nuclear materials.