Radiation resistance in alloys by solute-defect trapping

非技术摘要：目前核反应堆使用的材料不能满足为未来反应堆提出的先进设计的关键要求。特别是，它们对辐射损伤的抵抗力不足。我们在这里研究了一种提高材料抗辐射能力的方法，其中精心挑选的合金元素的少量添加被用来显著减缓这些材料的演化动力学。该方法利用社区现在可以从高通量原子计算获得的大量准确数据来筛选最有希望的合金化元素。这项研究建议使用最先进的纳米级实验来验证这种方法在铜基中的有效性，对于铜基，锑已经被预先选择为一种有希望的合金元素。这项工作还旨在确定这种材料设计方法是否可以与另一种材料设计方法相结合，依赖于纳米级沉淀的自发形成，从而产生极端的抗辐射能力。这项研究将为两名研究生和几名本科生提供教育，重点是先进的材料合成和表征技术，以及原子建模。将特别努力招收女性和代表性不足的少数民族学生。这项研究将与教育相结合，进一步开发和实施主动学习技术。技术摘要：这项基础研究计划研究了一种设计抗辐射损伤的单相材料的策略，通过添加少量的合金化的溶质来捕获点缺陷，以增加点缺陷的相互复合，而不是在汇点消除点缺陷。虽然这一策略过去曾被考虑过，并取得了令人鼓舞的结果，但它在很大程度上没有得到广泛的关注，这在很大程度上是因为没有可靠的方法来选择最佳的溶质来捕获点缺陷。这项拟议的研究利用了最近的建模进展来克服这些限制。具体地说，对于铜基，用第一性原理计算了溶质-点缺陷相互作用，用自洽平均场理论计算了缺陷和溶质输运系数，Sb被认为是这些有前途的溶质之一。实验程序直接测量了稀铜-锑合金辐照过程中复合相对于消除凹陷的相对速率，测量了位于Nb层包围的铜薄膜中处于关键位置的薄标志层的展宽和漂移，铜/Nb界面为点缺陷的消除提供了近乎完美的凹陷。这些展宽和位移是用原子探针层析成像(APT)和分析扫描电子显微镜(TEM)在纳米尺度上测量的。此外，该方法还用于赋予在辐照下自组织的合金(如铜-铁)抗辐照能力，从而进一步扩展其在辐照下的稳定性。通过结合点缺陷捕获和成分图案化这两种方法，可以在极大范围的辐照条件下实现抗辐射。实验计划得到原子KMC模拟的补充，以支持数据分析和探索在溶质筛选阶段所做的简化的潜在影响。通过向本科生提供研究机会，并通过在私人投资机构教授的课程中通过计算模块将研究与教育结合起来，该计划的影响得到了扩大。还提供主动参与来开发、评估和传播主动学习技术。

NON-TECHNICAL ABSTRACT:Materials used in current nuclear reactors cannot meet key requirements of the advanced designs proposed for future reactors. In particular, their resistance to radiation damage is insufficient. We investigate here one approach to increase materials radiation resistance, where small additions of carefully selected alloying elements are used to drastically slow down the kinetics of evolution of these materials. The approach takes advantage of the large body of accurate data now available to the community from high-throughput atomistic calculations to screen the most promising alloying elements. The research proposes to employ state-of-the-art nanoscale experiments to validate this approach in a copper matrix, for which antimony has been pre-selected as a promising alloying element. The work also aims at determining whether this material design approach can be combined with another one, relying on the spontaneous formation of precipitates at the nanoscale, thus resulting in extreme radiation resistance. The research will provide education for two graduate students and several undergraduate students, with an emphasis on advanced materials synthesis and characterization techniques, and atomistic modeling. Special effort will be made to recruit female and underrepresented minority students. The research will be integrated with education to further develop and implement active learning techniques.TECHNICAL ABSTRACT:This fundamental research program examines a strategy for designing single phase materials resistant to radiation damage by using small alloying additions of solutes that trap point defects so as to increase point defect mutual recombination over their elimination at sinks. While this strategy has been considered in the past, and yielded encouraging results, it has not received widespread attention in large part because no reliable method was available to select the best solutes to trap point defect. The proposed research takes advantage of recent modeling advances to overcome these limitations. Specifically, for a Cu matrix, using first principles calculations to calculate solute-point defect interactions, and self-consistent mean-field theory to calculate defect and solute transport coefficients, Sb was identified as one of these promising solutes. The experimental program measures directly the relative rate of recombination over sink elimination during irradiation of dilute Cu-Sb alloys from the broadening and the drift of thin marker layers placed at strategic positions in a Cu thin film bounded by Nb layers, the Cu/Nb interfaces providing near perfect sinks for point defect elimination. These broadenings and shifts are measured at the nanoscale using atom probe tomography (APT) and analytical scanning transmission electron microscopy (TEM). In addition this approach is implemented for imparting radiation resistance to alloys that self-organizes under irradiation, such as Cu-Fe, so as to further extend their stability under irradiation. By combining the two approaches, point defect trapping and compositional patterning, radiation resistance can be achieved in a vastly extended domain of irradiation conditions. The experimental program is complemented by atomistic KMC simulations to support the data analysis and to explore the potential impact of simplifications made during the solute screening stage. The impact of the program is broadened by offering research opportunities to undergraduates and by integrating research with education through computational modules in courses taught by the PIs. Active engagement is also offered to develop, assess, and spread active learning techniques.