Synergistic effect of hybrid reduced graphene oxide (rGO) and carbon nanotubes (CNTs) reinforcement on microstructure, mechanical and biological properties of magnesium-based composite

Magnesium (Mg) was considered as a new kind of biomaterial implant due to its biodegradability and biocompatibility. Nevertheless, sufficient mechanical properties and low degradation rates in physiological environments are required. In this research, we have demonstrated that a network structure is developed from the reduced graphene oxide (rGO) and carbon nanotubes (CNTs), which inhibited face-to-face aggregation of rGO nano-platelets by straight CNTs inserted into adjacent rGO nano-platelets. The combination of rGO and CNTs was then used to strengthen the Mg-based nanocomposite fabricated using semi-powder metallurgy. The compressive strength and strain to fracture were maximally achieved 326.7 MPa and 11.58%, respectively for composite with 0.16 wt% CNTs and 0.5 wt% rGO. It was due to the effective load transfer and energy absorption of rGO and CNTs. Mechanisms for crack tip shielding, crack bridging and crack deflection was found to be responsible for mechanical enhancement. The electrochemical tests showed that the composite with the lowest CNTs concentration has the best corrosion resistance. In addition, the apatite-forming ability of composite in simulated body fluid (SBF) and cell culture experiments demonstrated favorable composite bioactivity and biocompatibility. Evaluation of the antibacterial activity showed that the growth and penetration of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria could be significantly inhibited with increasing rGO-CNTs hybrid content in Mg alloy. This study may open the doors to the fabrication of Mg-based nanocomposite implants containing rGO-CNTs hybrid fillers for load-bearing applications.