The effect of electronic energy loss on irradiation-induced grain growth in nanocrystalline oxides

Abstract

Grain growth of nanocrystalline materials is generally thermally activated, but can also be driven by irradiation at much lower temperature. In nanocrystalline ceria and zirconia, energetic ions deposit their energy to both atomic nuclei and electrons. Our experimental results have shown that irradiation-induced grain growth is dependent on the total energy deposited, where electronic energy loss and elastic collisions between atomic nuclei both contribute to the production of disorder and grain growth. Our atomistic simulations reveal that a high density of disorder near grain boundaries leads to locally rapid grain movement. The additive effect from both electronic excitation and atomic collision cascades on grain growth demonstrated in this work opens up new possibilities for controlling grain sizes to improve functionality of nanocrystalline materials.

Redox response of actinide materials to highly ionizing radiation

“…No contribution to broadening from a decrease in crystallite size is observed ( Supplementary Fig. 1), consistent with previous work that has shown grain growth to result from irradiation of fluorite materials in the electronic stopping regime 26 . Therefore, the increased breadth of the diffraction peaks can be attributed solely to microstrain.…”

“…Again, peak shifts indicate unit cell expansion, while peak broadening indicates the accumulation of heterogeneous microstrain. As expected 26 , no decrease in the crystallite size was observed in the Williamson-Hall analysis (Supplementary Fig. 1), such that broadening can be attributed solely to microstrain.…”

Point defect evolution in Ni, NiFe and NiCr alloys from atomistic simulations and irradiation experiments

“…In the current approach, microstructure evolution is accelerated or driven by the larger Frenkel pair concentration, and the results from this approach have been fruitful in reproducing experimentally observed clusters and in revealing the underlying clustering mechanisms [16]. Similarly, radiation-induced grain growth has been captured in CeO 2 while elucidating the fast kinetics of grain growth observed experimentally [17,18]. Such interstitial clustering and irradiation induced grain growth had not been captured previously from the conventional cascade methods.…”

An in situ transmission electron microscopy study of the ion irradiation induced amorphisation of silicon by He and Xe

“…During the He (light-ion) irradiation, the majority of energy loss is through the electronic system in which the energy is effectively dissipated through bond excitation. That is, the electronic energy transfer in the He irradiation performed here is expected to be insufficient to generate damage itself, but may facilitate damage recovery through electron-phonon coupling processes [20,21].…”

“…Examining the conditions used in these experiments, energy loss ratios of 17.43 and 0.09 are obtained for the He and Xe irradiations, respectively. Given that the energy loss ratio can have a significant impact on the defect formation and stability in ionic-covalent systems [20,21], this could play a role in the amorphisation kinetics of ion irradiated Si. The two irradiations performed in these experiments have significantly different energy loss mechanisms: Xe being predominantly nuclear and He predominantly electronic.…”