Control of Kinetic Processes in Irradiated Alloys through Compositional Patterning

技术：先进的能源系统将操作环境推向更严峻和激进的极端，包括高温、高辐射剂量和高机械应力。为了应对这些挑战，需要新一代的材料，因为目前的材料是根据50年前开发的知识设计的，在这些条件下，将无法安全、可靠和经济地运行。该项目探索了一种全新的材料设计方法，可以永久抵抗辐射。pi计划了一种新的方法，即合金显微组织被设计成包括高密度的在辐照下动态稳定的点缺陷陷阱。这个目标是通过利用pi来实现的。过去在辐照诱导下的纳米级组成图案，以及学习如何利用这些组成异质性作为点缺陷的有效陷阱。通过设计，这种纳米结构材料对辐射不敏感。pi计划将这种方法应用于选定的铜基和铁基模型合金，以及通过纳米级氧化物分散强化的类似合金。在后一种情况下，采用簇束沉积和磁控溅射相结合的方法制备纳米复合氧化物-金属薄膜。结合XRD、TEM、原子探针层析成像等技术，对离子辐照前后的薄膜进行了表征。特别强调的是后者，因为它在三维中实现了亚纳米级的化学分辨率，从而可以完全表征纳米结构的成分模式。通过辐射增强扩散和膨胀测量来评估这些纳米结构的点缺陷捕获效率。一项计算工作将确定成分模式在微结构缓慢漂移时保持动态稳定的条件。为了实现这一目标，pi将与劳伦斯利弗莫尔国家实验室合作，实施一种新的并行动力学蒙特卡罗算法，将模拟速度提高几个数量级，从而使模拟中微观结构的复杂演变成为可能。非技术：该研究对开发对先进能源生产系统至关重要的新材料的合金设计策略具有广泛的科学影响。除了广泛发表这项研究的结果外，pi还计划在美国组织一个关于辐照下材料的暑期学校。其目标是教育下一代科学家和工程师，以维持甚至扩大核能在美国能源生产组合中的份额。此外，参与该项目的两名研究生将接受最先进的材料表征仪器的培训。pi将雇佣大学生助理，尤其是女性和未被充分代表的少数族裔。目前的工作将整合到pi的教学活动中，让本科生了解纳米结构材料的潜力和挑战。pi也会扩大吗？材料移动吗?高中访问计划，以达到更大的学生群体。

TECHNICAL: The advanced energy systems push operating environments to more severe and aggressive extremes, including high temperature, high radiation dose, and high mechanical stresses. A new generation of materials is required to meet these challenges since current materials, which were designed using knowledge developed as long as 50 years ago, will not operate safely, reliably, and economically under these conditions. This program explores a fundamentally new approach for the design of materials that would permanently resist radiation. PIs plan a new approach whereby alloy microstructures are designed to include a high density of point-defect traps that are dynamically stable under irradiation. This goal is achieved by taking advantage of PIs? past work on nanoscale compositional patterning induced by irradiation, and learning how to use these compositional heterogeneities as effective traps for point defects. By design, the nanostructured materials would thus be radiation-insensitive. PIs plan to apply this approach to selected Cu-base and Fe-base model alloys, as well as to similar alloys strengthened by nanoscale oxide dispersion. In the latter case, nanocomposite oxide-metal thin films are grown by combining cluster beam deposition with magnetron sputtering. The thin films are characterized before and after ion irradiation with a combination of techniques, including XRD, TEM, and atom probe tomography. A particular emphasis is put on the latter since it achieves sub-nanometric chemical resolution in three dimensions, and thus makes it possible to fully characterize nanostructured compositional patterns. The point-defect trapping efficiency of these nanostructures is assessed by radiation-enhanced diffusion and swelling measurements. A computational effort would identify the conditions for compositional patterns to remain dynamically stable even as the microstructure is slowly drifting. To achieve this goal, in collaboration with Lawrence Livermore National Laboratory, PIs will implement a new parallel kinetic Monte Carlo algorithm that speeds up simulations by several orders of magnitude, thus making it possible to follow the complex evolution of the microstructure in the simulations. NON-TECHNICAL: The research has broad scientific impact for the development of alloy design strategies for new materials that are critical to advanced energy production systems. Besides publishing widely the results from this research, PIs plan to organize, in the US, a summer school on Materials under Irradiation. The objective is to educate the next generation of scientists and engineers required to maintain or even expand the share of nuclear energy in the US energy production portfolio. In addition, the two graduate students working on this project will be trained on the most advanced instruments of materials characterization. PIs will hire undergraduate assistants, in particular women and underrepresented minorities. The present work will be integrated into the PIs teaching activities, exposing undergraduate students to the potentials and the challenges offered by nanostructured materials. PIs will also expand ?Materials Mobile? high-school visit program so as to reach a much larger student population.