Strengthening Effect in Aluminum-Graphene Nanolayered Composites via Interface Engineering

Two-dimensional (2D) graphene, renowned for its outstanding mechanical properties, has been extensively studied as an interlayer in metal or metallic glass composites to enhance their performance. Graphene's high in-plane intrinsic strength (130 GPa) and modulus (1 TPa) enables it to effectively block dislocations despite being a single atomic layer in thickness, thereby increasing the strength of the composite. For Al-graphene nanolayered composite, the presence of a native oxide layer that forms during breaking of vacuum for graphene layer transfer prevents the formation of a direct bonding between the metal and graphene. There is a lack of understanding of the effect of the presence of the oxide layer and the focus of this study is to examine the deformation mechanisms by studying Al-graphene nanolayered composite with different interfacial bonding and structure. In this study, we evaluated the mechanical properties of Al-graphene nanolayered composite with the presence of thin native oxide of 5 nm (Al/Al₂O₃/graphene) and compared the results to that of Al layer passivated with a thin epitaxial layer of Ag (5 nm), that is alternated with graphene, <i>i.e.</i> Al/Ag/graphene nanolayered composite. The Ag inhibits the formation of oxide in the Al layer and hence was chosen as an interlayer to study the effect of interfacial properties. High-resolution transmission electron microscopy (HRTEM) was used to determine the dislocation interaction at the two different interface types of Al/Al₂O₃/graphene and Al/Ag/graphene. The presence of Ag passivation layer that suppressed the formation of the alumina allowed for direct bonding between aluminum and graphene as evidenced by XPS analysis. Therefore, such strong interfacial bonding allowed for a notable enhancement in strength of the composite. The outcomes of this study revealed that interfacial engineering of metal-graphene nanolayered composite can contribute to different interaction of dislocations at the interfaces thereby is critically affecting the overall mechanical properties.