Radiation Tolerance of Nanocrystalline Ceramics: Insights from Yttria Stabilized Zirconia

Abstract

Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr+, 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

Ceramic Nanomaterials for High Temperature Applications

“…This could be verified with some other experiments using SiC and Si 3 N 4 as the matrix former complimented with nitrides, carbides of borides for the ceramic composite high temperature material [14][15][16].…”

Energetics of vacancy segregation to [100] symmetric tilt grain boundaries in bcc tungsten

“…This effect of absorbing or emitting point defects can have significant implications for nanomaterials with a high volume fraction of GBs or interfaces. Prior experimental studies161718 and atomistic simulations101117 revealed that nanomaterials generally show better radiation resistance in comparison with conventional coarse-grained materials. The underlying mechanism has been revealed by Bai, Uberuaga and coworkers1019, demonstrating that interstitial-loaded GBs, acting as a source, can emit interstitials to annihilate vacancies present in the near-GB region.…”

Fast crystallization of amorphous Gd2Zr2O7 induced by thermally activated electron-beam irradiation

“…29,31 However, nanocrystalline materials may be more inclined to ion-irradiation-induced amorphization given their very small particle size in which the excess surface energy leads to a more stable amorphous structure. As was demonstrated in MgGa 2 O 4 29 and YSZ, 30 the kinetics of defects-recovery may help to counter-balance this thermodynamic destability. 16 The simultaneous effects of thermodynamics and kinetics dominating defect formation and healing in nanomaterials have been discussed by Shen. 32 Similar to the ion-irradiation-induced disordering and amorphization process, the electron-irradiation-induced recrystallization process may also exhibit a noticeable grain size effect.…”

“…The role of electronic deposition and the coupled dynamics of electronic and atomic processes need to be studied over a range of irradiation conditions to elucidate the underlying mechanisms for different classes of materials. 26 Lately, the preparation of waste forms on the nanoscale has attracted much attention owing to their enhanced radiation resistance, such as is observed in silicon carbide, 27 pyrochlore Gd 2 30 For the nanocrystalline materials, abundant grain boundaries can act as sinks for the irradiation-induced defects and hinder the accumulation of the defects. 29,31 However, nanocrystalline materials may be more inclined to ion-irradiation-induced amorphization given their very small particle size in which the excess surface energy leads to a more stable amorphous structure.…”