Environment Assisted Cracking of Graphene

University Of North Carolina At Charlotte, Charlotte NC

Investigators

Abstract

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.