Interfacial strengthening by reduced graphene oxide coated with MgO in biodegradable Mg composites

Graphene oxide has been proven to be a promising anti-penetrant shield for Mg alloys against their over-rapid biodegradation, but the weak interfacial bonding between graphene oxide and Mg alloy is the main obstacle for effective protection. In this study, magnesium oxide (MgO) nanoparticles are coated on reduced graphene oxide (RGO) surface and then introduced in AZ61 alloy by laser melting, expecting to strengthen the interfacial bonding between Mg matrix and RGO. The results reveal that MgO acts as an interfacial bridge between Mg matrix and RGO and constructs nanoscale-contact and distortion areas with RGO. Moreover, MgO and α-Mg form a semi-coherent interfacial structure, in which an orientation relationship of MgO (‾200)//α-Mg (‾110‾2) and a small planar disregistry of 7.5% are detected. These interfacial characteristics indicate strong bonding at both the RGO/MgO and MgO/α-Mg interfaces, which thereby strengthens the protective capability of RGO. Compared with AZ61-RGO composite and AZ61 alloy, the AZ61-RGO/MgO composite present 13.3% and 34.0% decreases in corrosion rate, respectively. Meanwhile, the compressive strength and hardness of AZ61 alloy are also enhanced owing to the strengthened interfacial bonding. These findings demonstrate that the RGO/Mg interfacial strengthening is a promising candidate for improving the degradation behavior of Mg alloys.