Isotope labeling for quantitative determination of defect sink strength and fundamentals studies on defect-sink interactions
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Nontechnical Abstract Nuclear power is one solution to meet the ever-increasing demand for energy. One key issue in the so called "nuclear renaissance" is materials development towards longer life time under harsh environments. In order to withstand neutron damage at high temperatures, various nanostructured materials have been developed by introducing defect sinks to absorb/remove defects. However, quantitative determination of defect sink strength is still a technological bottleneck. This project uses an isotope labeling technique to quantitatively measure the sink strength in ion irradiated stainless steels as a key approach for a full scope investigation on defect-sink interactions. Such capability is critical to develop radiation tolerant materials. Even for the same type of defect sinks, fine tuning of their microstructures to maximize sink strength requires knowledge of one-to-one correlation between structures and sink strength. The study will contribute to the general understanding of defects in metals. The project offers students unique opportunities to combine training and research in nuclear engineering, nanomaterials, atomic scale characterization and atomic scale modeling, for solving issues of real-world importance. Technical Abstract For Fe based stainless steels of nature Fe abundance, implantation of 57Fe isotope atoms will introduce 57Fe interstitials. Upon annealing, the amount of 57Fe enrichments at defect sinks directly reflects the sink strength for defect trapping. Hence the defect sink strength under different irradiation/annealing/stress conditions can be systematically studied. Three-dimensional atom probe tomography (APT) will be used to map 57Fe isotope distributions. APT is coupled with transmission electron microscopy (TEM) and 3-D TEM tomography to establish one-to-one correlation between defect sink structure and sink strength. The project will study two defect sink types: (1) grain boundaries in grain-engineered stainless steels in order to understand effects of boundary misorientation angles on sink strength and (2) oxide particles in oxide-dispersion-strengthened alloys (ODS) in order to understand the effects of oxide-matrix interfaces on sink strength. The project further integrates molecular dynamics simulations to shed light onto fundamentals. The defect sink strength will be used as inputs in kinetic Monte Carlo simulations for obtaining structural evolutions which can be linked to and compared with experimental observations. In conjunction with materials synthesis, modeling, and atomic scale characterization, the project will obtain the fundamental understanding needed to maximize radiation tolerance of reactor core components. The project offers students unique opportunities to combine training and research in nuclear engineering, nanomaterials, atomic scale characterization and atomic scale modeling, for solving issues of real-world importance.