Environment Assisted Cracking of Graphene

该奖项支持对石墨烯环境辅助开裂机制的研究。环境辅助开裂是各种工程材料（如金属和玻璃）中常见的损伤问题，导致材料的破坏远远低于其最大强度。最近对石墨烯断裂特性的研究表明，石墨烯也可能发生以应力腐蚀开裂形式出现的环境辅助开裂。从纳米器件到太空电梯，石墨烯的广泛潜在应用需要了解石墨烯环境辅助开裂的机制，以防止灾难性的腐蚀开裂。该项目的第二个目标是研究石墨烯是否可以作为防腐涂层来保护活性金属免受腐蚀。石墨烯的渗透性和光学透明性激发了它作为铜等金属保护层的用途。然而，关于这个问题的实验结果是非常矛盾的。一些实验表明，石墨烯几乎可以完全阻止腐蚀，而另一些实验表明，使用石墨烯涂层可能会导致底层金属更广泛的腐蚀。先进的数值模拟将用于了解石墨烯在什么条件下作为保护层，以及在什么条件下石墨烯使情况恶化。从该项目中获得的见解可以通过降低与腐蚀开裂相关的大量工业成本来造福社会。对高中生的拓展也将与研究活动相结合。理解腐蚀开裂机理的一个主要困难是理解机械载荷对化学反应的影响。建立了一种耦合原子域和连续域的分层多尺度方法来考虑远程应力场对裂纹尖端发生的化学反应的影响。化学反应将在原子区使用分子动力学结合自一致电荷密度-功能基紧密结合来捕获，而远程应力场的影响将使用连续区来捕获。多尺度方法将用于研究温度、晶界和环境分子等因素对多晶石墨烯晶间和晶内腐蚀的影响。

This award supports the study of the mechanism of environment assisted cracking in graphene. Environment assisted cracking is a common damage problem in a variety of engineering materials such as metals and glasses, leading to the failure of materials well below their maximum strength. Recent studies on the fracture properties of graphene show that environment assisted cracking in the form of stress corrosion cracking can occur in graphene too. The wide spectrum of potential applications of graphene from nanodevices to space elevators necessitates understanding of the mechanisms of environment assisted cracking in graphene to prevent catastrophic corrosion cracking. The second objective of this project is to investigate if graphene can act as an anticorrosion coating to protect reactive metals against corrosion. The permeability and optical transparency of graphene has inspired its use as a protective layer of metals such as copper. However, the experimental results on this subject are very contradictory. Some experiments have indicated that graphene can stop corrosion almost completely, while the others have indicated that using a graphene coating can lead to a more extensive corrosion in the underlying metal. Advance numerical modeling will be use to understand at what conditions graphene acts as a protective layer and under what conditions graphene makes the situation worse. Insights gained from this project can benefit society by reducing the large industrial costs related to corrosion cracking. Outreach to high school students will also be integrated with the research activities.A main difficulty in understanding the mechanism of corrosion cracking is to understand the impact of mechanical loading on the chemical reactions. A hierarchical multi-scale method coupling atomistic and continuum domains will be developed to consider the impact of long-range stress fields on the chemical reactions occurring at the crack tip. The chemical reactions will be captured in the atomistic zone using molecular dynamics combined with self-consistent charge density-functional-based tight-binding and the impact of the long-range stress field is captured using the continuum zone. The multi-scale method will be used to study the impact of factors such as temperature, grain boundaries and environmental molecules on the intergranular and intragranular corrosion of polycrystalline graphene.