This work used spark plasma sintering (SPS) to prepare graphene nanosheets (GNS) reinforced zinc matrix composites. The influence of GNS on the microstructure and mechanical properties of zinc matrix composites was studied. The results show that the GNS/Zn composites prepared by SPS have a dense structure and good interface bonding, and GNS are uniformly distributed in the zinc matrix. Adding GNS can significantly improve the mechanical properties of the zinc matrix. When 0.7 wt% GNS are added, the comprehensive mechanical properties of the composite material are improved. The ultimate tensile strength is 254 MPa, and the Vickers hardness is 65 HV, which are 126 and 20.3% higher than those of pure zinc (112 MPa and 54 HV), respectively. The strengthening mechanisms of GNS/Zn composites are mainly load transfer of GNS and dislocation strengthening caused by coefficient of thermal expansion (CTE) mismatch. In addition, the biodegradability of GNS/Zn composites was evaluated by electrochemical measurement and immersion test. The results show that adding GNS to the zinc matrix will accelerate the degradation rate of the composite material. But the degradation rate can be controlled by the content of GNS. Its degradation rate is in the range of 69–301 μm/a, an ideal degradation rate as an orthopedic implant material.

The activity of zinc is between that of magnesium and iron, and it has a suitable degradation rate and good biocompatibility. It has been regarded as a very promising biodegradable metal material for biomedicine. However, the insufficient mechanical properties of pure Zn limit its practical application in the field of orthopedic implants. In this paper, partially unzipped carbon nanotubes (PUCNTs) obtained by meridionally cutting multi-walled carbon nanotubes (MWCNTs) were used as reinforcements and combined with spark plasma sintering to prepare partially unzipped carbon nanotube reinforced Zn matrix composites. The effects of PUCNT addition on the microstructure and the mechanical properties of Zn matrix composites were investigated. The microstructure analysis showed the good interface bonding between PUCNTs and the Zn matrix. Additionally, the strength of PUCNTs/Zn composites showed a trend of increasing first and then decreasing with the PUCNT content increases. When the PUCNT content was 0.2 wt%, the tensile strength and yield strength of composites were about 78.4% and 64.4% higher than that of pure Zn, respectively, while maintaining a high elongation (62.6%).

As a new type of biodegradable implant material, zinc matrix composites have excellent potential in the application of biodegradable implants because of their better corrosion resistance than magnesium matrix materials. Our previous studies have shown that graphene nanosheet reinforced zinc matrix composites (Zn-GNS) prepared by spark plasma sintering (SPS) have good mechanical properties and suitable degradation rate. However, the biocompatibility of zinc matrix composites is still a problem of concern. The cytocompatibility and blood compatibility of pure zinc and Zn-GNS composites in vitro were studied. The results showed that Zn-GNS composites had acceptable toxicity to MG-63 human osteosarcoma cells. In addition, the hemolysis rate of pure zinc and its composites were less than 3%, which has no adverse effect on adhered platelets, and has good antithrombotic and antiadhesion platelets properties. In conclusion, the addition of GNS did not adversely affect the biocompatibility of Zn-GNS composites, which indicated that Zn-GNS composites are a promising candidate for bone implantation.