CAREER: Asymmetrical Fracture of Two-Dimensional High Entropy Materials

该学院早期职业发展(CALEAR)奖支持研究至少包含五种元素的二维原子厚度高熵材料的断裂。二维材料，如石墨烯，通常倾向于脆性行为，这降低了使用它们建造的电子、光电子和能量存储设备的机械稳定性。由于在原子水平上存在更大的不对称性，二维高熵材料有望具有更好的断裂韧性。因此，本项目为合成单层和多层二维高熵材料的基础研究，在电子显微镜下进行断口可视化实验，并从理论上再现实验观察到的行为提供了基础研究。这项研究将拓宽二维材料的家族，并促进对缺陷和其他因素对其力学性能和行为影响的理解。由于具有更高的断裂韧性，二维高熵材料有可能取代现有材料或与现有材料集成，制造出高生命周期的纳米器件。作为该项目的一部分，综合研究和教育计划将努力通过课堂/在线教育、知识传播、工程培训和外联活动产生社会影响。将向研究生和本科生，特别是代表性不足的少数民族学生提供研究机会。外展活动将针对K-12学生，特别是在家上学的学生，以激励他们接受STEM教育。受二维几何约束，裂纹在室温下一般表现为塑性最小的脆性行为，这构成了块体材料断裂韧性和力学强度性能互不相容的困境的基础。本研究旨在研究二维高熵材料的非对称断裂，其中由于裂纹尖端的非对称边缘弹性性质和裂纹扩展过程中的边缘交换而出现分叉、分支和挠度，从而显著提高断裂阻力。通过固相反应和化学气相沉积的方法可以合成各种二维高熵材料。在扫描电子显微镜和透射电子显微镜下进行原位拉伸试验，以显示各种微观组织缺陷和特征中的变形和断裂演化，如竞争的三元和四元相。将使用基于DFT计算、数据驱动MD模拟和相场模拟的多尺度建模框架来模拟断裂行为，重点是裂纹的萌生和扩展。最终，该项目将促进对晶格扭曲、缺陷、应变率和裂纹几何以及组成对二维高熵材料力学行为的影响的理解。该项目由土木、机械和制造创新部门(CMMI)和既定的刺激竞争研究计划(EPSCoR)联合资助。该奖项反映了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。

This Faculty Early Career Development (CAREER) award supports research to investigate fracture of two-dimensional atoms-thick high entropy materials containing at least five elements. Two-dimensional materials, such as graphene, generally favor a brittle behavior, which reduces mechanical stability of the electronics, photonics, and energy storage devices built with them. Two-dimensional high entropy materials are expected to possess substantially better fracture toughness owing to a greater asymmetry at the atomic level. Thus, this project supports fundamental research to synthesize monolayer and multiplayer two-dimensional high entropy materials, conduct experiments in electron microscopes to visualize fracture, and theoretically reproduce the experimentally observed behaviors. Insights from this study will broaden the family of two-dimensional materials and advance the understanding of the effect of defects and other factors on their mechanical properties and behaviors. With higher fracture toughness, two-dimensional high entropy materials could potentially replace or be integrated with existing materials to produce high lifecycle nanoscale devices. As part of the project, an integrated research and education program will strive for societal impacts through classroom/online education, knowledge dissemination, engineering training, and outreach activities. Research opportunities will be afforded to both graduate and undergraduate students, specially underrepresented minority students. Outreach activities will target K-12 students and, uniquely, homeschoolers to motivate them towards STEM education. Confined to two-dimensional geometry, cracks generally lead to brittle behavior with minimum plasticity at room temperature, which forms the basis of the dilemma of mutually exclusive fracture toughness and mechanical strength performance in bulk materials. This research aims to investigate asymmetrical fracture of two-dimensional high entropy materials, where bifurcations, branches, and deflections emerge due to asymmetric edge elastic properties at the crack tip and edge swapping during crack propagation, thus, significantly increasing the fracture resistance. Various two-dimensional high entropy materials will be synthesized via solid state reaction and chemical vapor deposition methods. In situ tensile tests in SEM and TEM will be conducted to visualize the deformation and fracture evolution amid various microstructural defects and features, such as the competing ternary and quaternary phases. A multiscale modeling framework based on DFT calculations, data-driven MD simulations, and phase field modeling will be used to simulate fracture behavior with focus on crack initiation and propagation. Ultimately, the project will advance the understanding of the effect of lattice distortion, defects, strain rate, and crack geometry as well as composition on the mechanical behavior of two-dimensional high entropy materials.This project is jointly funded by the Division of Civil, Mechanical and Manufacturing Innovation (CMMI) and the Established Program to Stimulate Competitive Research (EPSCoR).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.