Microwave-Sintered Graphene/ZTA Biocomposites for Artificial Joints: Synergistic Mechanical Reinforcement, Tribological Enhancement, and Biofunctional Improvement

Although zirconia-toughened alumina (ZTA) ceramics exhibit favorable bioinertness and toughness, their flexural strength, fracture resistance, and tribological performance still fall short of the mechanical robustness, wear resistance, and biocompatibility required for the long-term reliability of artificial joint implants. This study investigates the effects of graphene content on the microstructure, mechanical properties, and biological performance of microwave-sintered ZTA composites. Microwave sintering effectively preserved graphene integrity. At 0.3 wt% graphene, homogeneous dispersion and enhanced densification yielded optimal mechanical properties: hardness of 18.15 GPa, fracture toughness of 6.54 MPa m 1 / 2 , and flexural strength of 660.54 MPa—surpassing pure ZTA (18.65 GPa, 5.02 MPa m 1 / 2 , 559.7 MPa) except in hardness. Biofunctionally, the incorporation of graphene markedly promoted osteoblast proliferation, while imparting enhanced antibacterial efficacy and anti-inflammatory properties. At 0.5 wt%, graphene agglomeration increased porosity and deteriorated both mechanical and biological performance, confirming an optimal addition threshold. A 12-week in vivo rabbit bone defect study confirmed that 0.3GZTA exhibited good systemic biosafety, with thinner fibrous encapsulation and stronger osseointegration than pure ZTA, supporting the translational potential of microwave-sintered graphene/ZTA composites for next-generation joint prostheses.