3-D temperature profile of nano -sized zirconia upon intensive ionizing radiation

1. Nanostructured Materials Not Intrinsically TolerantJieLian, Rensselaer Polytechnic Institute, DMR 0906349 Outcome: Researchers at Rensselaer Polytechnic Institute have identified amorphization of nanostructured zirconia upon intensive ionizing radiation, which was highly tolerant at larger-size. Impact: Conventional wisdom exists that nanostructured materials are radiation tolerant due to interface and grain boundary behaving as effective sinks for defect recovery. This finding highlights the importance in understanding radiation interaction for designing nanostructured materials for nuclear applications. Explanation: Nanostructured zirconia was amorphized by ionizing radiation with an extremely high electronic energy loss in which a transient zone with temperature well above the melting temperature was induced. The extreme electronic energy loss, coupled with the high energy state of the nanostructured materials and a high thermal confinement due to the less effective heat transport within the transient hot zone, may eventually be responsible for the ionizing radiation-induced amorphization above a threshold electronic energy loss. 3-D temperature profile of nano-sized zirconia upon intensive ionizing radiation

2. Non-Saturation of Interface SinksHanchen Huang, University of Connecticut, DMR 0906349 Outcome: Researchers at University of Connecticut have found that interfaces do not saturate as sinks of radiation produced defects. Impact: This finding provides the foundation for the design and application of nanostructured materials in nuclear reactors. Explanation:Interfaces, particularly grain boundaries, serve as sinks of radiation produced defects, such as vacancies and interstitials. In nanostructured materials, the interfaces are more populous. If they do not saturate as sinks, their large population can make nanostructured materials more radiation resistant. However, the asymmetry of vacancies and interstitials in diffusivity means that a larger number of one type of defects (such as interstitials in metals) may jam or saturate the interfaces. Using a combination of atomistic simulations and analytical formulations, we have shown that such saturation does not occur. Prof. Huang working with graduate students and NSF Joule Fellows