Graphene nanoplatelets were added as reinforcement to alumina ceramics in order to enhance microscale tribological behavior, which would be beneficial for ceramic-on-ceramic hip implant applications. The reduction in microscale wear is critical to hip implant applications where small amounts of wear debris can be detrimental to patients and to implant performance. The addition of the GNPs lead to improvements in fracture toughness and wear (scratch) resistance of 21% and 39%, respectively. The improved wear resistance was attributed to GNP-induced toughening, which generates fine (~100nm) microcracks on the scratch surface. In addition, active participation of GNPs was observed in the scratch subsurface of GNP-reinforced samples through focused ion beam sectioning. Friction coefficients are not significantly influenced by the addition of GNPs, and hence GNPs do not act as solid state lubricants. In vitro biocompatibility with human osteoblasts was assessed to evaluate any possible cytotoxic effects induced by GNPs. Osteoblast cells were observed to survive and proliferate robustly in the GNP-reinforced samples, particularly those with high (10-15vol%) GNP content.
Keywords: Biocompatibility; Ceramic matrix composites; Graphene nanoplatelets; Microscratch; Nanotribology; Osteoblasts.
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