Control of Kinetic Processes in Irradiated Alloys through Compositional Patterning

技术：先进的能源系统将工作环境推向更恶劣和更具侵略性的极端，包括高温、高辐射剂量和高机械应力。需要新一代材料来应对这些挑战，因为目前的材料是利用50年前发展起来的知识设计的，在这些条件下不会安全、可靠和经济地运行。该项目探索了一种设计永久抗辐射材料的全新方法。PIS计划了一种新的方法，通过这种方法，合金微结构被设计成包括高密度的点缺陷陷阱，这些陷阱在辐照下动态稳定。这一目标是通过利用PI实现的？过去关于辐射诱导的纳米级成分图案化的工作，并学习如何使用这些成分异质性作为点缺陷的有效陷阱。根据设计，纳米结构材料因此是辐射不敏感的。PIS计划将这一方法应用于选定的铜基和铁基模型合金，以及通过纳米氧化物分散强化的类似合金。在后一种情况下，采用团束沉积和磁控溅射相结合的方法制备了氧化物-金属纳米复合薄膜。用X射线衍射仪、透射电子显微镜和原子探针层析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，因为它在三维上实现了亚纳米级的化学分辨率，从而使充分表征纳米结构的组成模式成为可能。通过辐射增强的扩散和溶胀测量，评估了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保持动态稳定的条件，即使微观结构正在缓慢漂移。为了实现这一目标，PIS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，该算法将模拟速度提高几个数量级，从而使在模拟中跟踪微观结构的复杂演变成为可能。非技术性：这项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，PIS还计划在美国组织一次关于受辐射材料的暑期学校。其目标是培养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关于最先进的材料表征仪器的培训。PIS将聘请本科生助理，特别是女性和代表性不足的少数族裔。目前的工作将被整合到PIS教学活动中，让本科生接触到纳米结构材料带来的潜力和挑战。PIS还将扩展？材料移动？高中访问计划，以便接触到更多的学生人口。

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.