Interfacial Characteristics of Graphene-Reinforced Iron Composites: A Molecular Dynamics Study

Interface has a significant effect on mechanical properties of graphene reinforced metal composites. Taking graphene nanosheet reinforced iron composite (Gr/Fe) as an example, the interfacial characteristics of Gr/Fe (110), (111), ((Formula presented.)), and (001) interfaces have been studied using molecular dynamics (MD) simulations. Two types of interfacial bonding have been examined: physical and chemical bonding. The results show that when the graphene and iron form a physical adsorption (weak-bonded) interface, the interactive energy of the graphene and Fe (110), (111), ((Formula presented.)), and (001) interface is −1.00 J/m², −0.73 J/m², −0.82 J/m², and −0.81 J/m², respectively. The lengths of the Fe-C bonding are distributed in the range of 2.20–3.00 Å without carbide formation, and no distinct patterns of atomic structure are identified. When the graphene and iron form a chemical (strong-bonded) interface, the corresponding interactive energy is −5.63 J/m², −4.32 J/m², −4.39 J/m², and −4.52 J/m², respectively. The lengths of the Fe-C bonding are mainly distributed in the ranges of 1.80–2.00 Å and 2.30–2.50 Å, which the carbides such as Fe₃C and Fe₇C₃ are formed at the interface. Moiré patterns are observed at different-oriented interfaces, because of the lattice geometrical mismatch between graphene and different-oriented iron crystal structures. The pattern of diamond stripe is at the (110) interface, which is in good accordance with the experiment. Other patterns are the hexagonal pattern at the (111) interface, the wavy stripe pattern at the ((Formula presented.)) interface, and the chain pattern at the (001) interface. These moiré patterns are formed through the competition and coordination of the three binding sites (Hollow, Bridge, and Top) of graphene with Fe atoms.