DMREF: A Fundamental Approach to Study the Effect of Structural and Chemical Composition in Functionalized Graphene Materials

该项目的核心目标是通过将理论、建模和实验以多尺度和协同的方式结合起来，建立材料设计的范式转变，以最大限度地提高纳米复合材料的强度和韧性，从而模拟使用氧化石墨烯的天然珍珠层的性能。预计具有最佳重叠几何形状的氧化石墨烯片，通过可调化学结合在一起，将模拟珍珠质。具体来说，本研究将通过研究单个原子薄片及其交联元素的强度和刚度来表征多层纳米复合材料系统的变形机制。本项目旨在对范德华相互作用、氢键、化学交联、构象和几何组装在调节基于氧化石墨烯的纳米复合材料的机械行为中所起的作用有一个基本的理解。功能化石墨烯片和宏观氧化石墨烯材料的力学性能将通过一系列迭代的合成-组装-建模循环得到优化。基于MEMS技术和AFM的新型纳米力学测试方法将被应用于测量具有“砖瓦”状分层结构的少层氧化石墨烯材料的力学行为。新的交联化学物质，如硫醇胺，将通过共价键断裂和重组来控制剪切相互作用。不同的几何重叠层之间的层和构象将被探索。原位电子显微镜力学测试，以获得多个长度尺度上的原子和微观尺度特征，再加上使用从头算和半经验方法的计算建模，将量化控制载荷传递机制的界面强度和变形。然后，开发的见解将用于指导宏观纳米复合材料的合成，该材料利用石墨烯的强度和受大自然启发的分层组装结构。预计用于预测和调整氧化石墨烯基纳米复合材料机械性能的标准的发展将转移到广泛的纳米复合材料中，并将优化具有分层结构的材料的设计过程，这些结构包括刚性构建块和延展性交联元素。这些下一代合成材料对于航空航天、卫星、汽车、军事和医疗保健行业的进步至关重要。该研究还将为基于结构的材料设计的关键前沿的研究生和博士后提供一个优秀的培训平台，以及在合成，建模和分层测量领域的跨学科科学研究艺术。

The central goal of this project is to establish a paradigm shift in material design by combining theory, modeling, and experimentation in a multiscale and synergistic manner to maximize the strength and toughness of nanocomposite materials that emulate the performance of natural nacre using graphene oxide. It is expected that graphene oxide sheets with optimal overlap geometry, bonded together by tunable chemistry, will mimic nacre. Specifically, this research will lead to characterization of the deformation mechanisms of multilayer nanocomposite systems through studies of the strength and stiffness of both the individual atomically thin sheets as well as their crosslinking elements. This project aims to develop a fundamental understanding of the roles that van der Waals interactions, hydrogen bonds, and chemical crosslinking, conformation, and geometrical assembly play in modulating the mechanical behavior of nanocomposite materials based on graphene oxide. The mechanical performance of functionalized graphene sheets and macroscopic oxidized-graphene materials will be optimized through a series of iterative synthesis-assembly-modeling cycles. Novel nanoscale mechanical testing methods based on MEMS technologies and AFM will be applied to measure the mechanical behavior of few-layer graphene oxide materials with "brick-and-mortar" like hierarchical structures. New crosslinking chemistries, such as thiol-amines, will be explored to impart significant improvements in controlling shear interactions through covalent bond breaking and reformation. Varying geometrical overlap between layers and conformations of the sheets will be explored. In-situ electron microscopy mechanical testing, to yield atomic and micro-scale characteristics on multiple length scales, coupled with computational modeling using ab initio and semi-empirical methods, will quantify the interface strength and deformation governing load-transfer mechanisms. The developed insight will then be used to guide the synthesis of a macroscopic nanocomposite material that takes advantage of the strength of graphene and the hierarchically assembled structures inspired by Nature.It is expected that the development of criteria for predicting and tailoring the mechanical properties of graphene oxide-based nanocomposite materials will be transferable to a wide range of nanocomposites and will optimize the design process of materials with hierarchical structure that incorporate stiff building blocks and ductile crosslinking elements. These next-generation synthetic materials are essential for advances in the aerospace, satellite, automotive, military, and healthcare industries. The research also will serve as an excellent training platform for graduate students and postdoctoral fellows in the critical frontier of structure-based material design and in the art of interdisciplinary scientific research in the areas of synthesis, modeling, and hierarchical measurements.