Understanding self-assembled He-bubble superlattices under deformation in materials utilizing novel experimental methods

非技术摘要：例如，在材料中由辐射引起的核反应在材料中产生惰性气体，可能导致材料中产生非常小的气泡。这些特征可以改变材料对机械变形的反应，并可能导致强度增加。根据温度、气体量和时间的不同，这些气泡可以将自己排列成有序的结构，这种结构通常被称为气泡“超晶格”。材料的变形，可以改变这种气泡超晶格的排列，这反过来又可以改变材料的机械性能响应。在这项工作中，我们将重点关注氦(He)气泡，这是暴露在核环境中的材料中常见的。我们将使用氦离子束显微镜和随后的小规模机械性能评估技术，如压痕和纳米柱压缩测试。我们将研究代表不同结构的不同材料，这将使我们能够了解这些结构在变形时所经历的变化及其对材料机械性能的影响。这项研究的图像和结果将被用作课堂和演讲中的外展工具，让当地高中生参与材料研究。此外，我们将积极邀请本科生，特别是那些来自少数族裔群体的学生参与这项研究工作，从而对他们进行相关材料科学技术和工具的培训，并为他们早日进入研究生院做好准备。技术摘要：本项目旨在对具有代表性的不同晶体结构的金属材料在外部载荷和随后的变形下自组装的纳米级氦气泡超晶格有一个基本的了解。我们的目标是观察这种规则排列的气泡对变形的反应，甚至可能到失去规则排列气泡的程度。为了系统地进行这些观察，我们将以一种新颖的方式利用氦离子束显微镜：也就是说，不是拍摄图像，而是将束流的氦离子植入材料中。通过控制注入，我们可以以更高的实验精度量化与这些结构相关的机械性能变化，这将使我们能够用这些实验的直接参数输入来改进材料硬化模型。将实验文本矩阵扩展到不同的晶体结构(fcc、bcc、hcp)将使我们对这些结构的形成有更基本的了解，同时也概括了这些结构对力学性能的影响。此外，这种新注入技术的发展不仅将加快材料中气泡的研究，还可能影响其他研究半导体和纳米泡沫材料的光学和量子性质的科学领域。这笔资金将提供进行研究所需的资源，并将使加州大学伯克利分校的核材料小组加强我们在学术界内外的推广努力，以激发公众对材料和纳米科学的兴趣。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical abstract:The creation of inert gases in materials, by nuclear reactions induced by irradiation within a material, for example, can lead to the development of very small gas bubbles in the material. These features can change a material's response to mechanical deformation and can lead to increased strength. Depending on temperature, the amount of gas, and time, these gas bubbles can arrange themselves into an ordered structure, which is oftentimes called a gas-bubble 'superlattice'. Deformation of the material, can change the arrangement of this gas-bubble superlattice, which, in turn, can change the mechanical-property response of the material. In this work, we will focus on helium (He) bubbles, which are common in materials exposed to nuclear environments. We will use a helium-ion-beam microscope with subsequent small-scale mechanical-property evaluation techniques, such as indentation and nano-pillar compression testing. Different materials which represent different structures will be investigated which will allow us to understand the changes these structures undergo while being deformed and its implications for the mechanical performance of a material. The images and results of this research will be used as an outreach tool in classes and in presentations, to engage local high-school students in materials research. Furthermore, we will actively engage undergraduate students, especially those from underrepresented minority groups, in this research effort, thereby training them on relevant materials-science techniques and tools and preparing them early for graduate school.Technical abstract:This program aims to obtain a fundamental understanding of self-assembled, nanoscale, He-bubble superlattices in representative metallic materials of different crystal structures under external load and subsequent deformation. The goal is to observe how this regular arrangement of gas bubbles reacts to the deformation, perhaps even to the point of losing the regular arrangement of the bubbles. To make these observations systematically, we will utilize a He-ion-beam microscope in a novel way: namely, not to photograph images but to implant the beam's He into the material. By controlling the implantation, we can quantify with increased experimental accuracy the mechanical-property changes associated with these structures, which will allow us to refine the material-hardening models with direct parameter input from these experiments. Expanding the experimental text matrix to different crystal structures (FCC, BCC, HCP) will lead to a more fundamental understanding of the formation of these structures while also generalizing the effect of these structures on mechanical properties. Additionally, the development of this new implantation technique not only will accelerate research on gas bubbles in materials but may also impact other scientific fields investigating the optical and quantum properties of semiconductors as well as nano-foamed materials. The funding will provide the resources needed to do the research and will allow the nuclear-materials group at UC Berkeley to intensify our outreach efforts both within and outside the academic community, to trigger the general public's interest in materials and nanoscience.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.