Environment Assisted Cracking of Graphene

该奖项支持对石墨烯环境辅助裂解机理的研究。环境辅助开裂是金属和玻璃等各种工程材料中常见的损伤问题，导致材料在远低于其最大强度的情况下失效。最近对石墨烯断裂性能的研究表明，石墨烯也可以发生以应力腐蚀形式的环境辅助开裂。石墨烯的潜在应用范围广泛，从纳米器件到空间电梯，需要了解环境辅助石墨烯开裂的机理，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一种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促使它被用作铜等金属的保护层。然而，关于这一课题的实验结果却非常矛盾。一些实验表明，石墨烯可以几乎完全阻止腐蚀，而另一些实验表明，使用石墨烯涂层可以在底层金属中导致更广泛的腐蚀。高级数值模拟将被用来了解石墨烯在什么条件下充当保护层，以及在什么条件下石墨烯使情况变得更糟。从这个项目中获得的见解可以降低与腐蚀破裂相关的巨大工业成本，从而造福社会。对高中生的推广也将与研究活动结合在一起。理解腐蚀破裂机制的一个主要困难是了解机械载荷对化学反应的影响。为了考虑长程应力场对裂纹尖端化学反应的影响，将发展一种原子域和连续域相结合的分层多尺度方法。化学反应将通过分子动力学和基于自洽电荷密度泛函的紧束缚相结合的方法在原子化区捕获，而长程应力场的影响则使用连续统区捕获。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.