Effect of carbon nanotube and aluminum oxide addition on plasma-sprayed hydroxyapatite coating's mechanical properties and biocompatibility

This study reports on the synthesis of novel bioceramic composite coating of hydroxyapatite (HA) reinforced with carbon nanotubes (CNTs) and aluminum oxide (Al2O3) using plasma spray technique. Fracture toughness of HA–20 wt.% Al2O3 improved by 158% as compared to HA coating whereas HA–18.4 wt.% Al2O3–1.6 wt.% CNT showed an improvement of 300%. Carbon nanotubes provided reinforcement via rebar mechanism. Human fiber osteoblast cell-growth studies showed that biocompatibility of the coating remained unaltered, as Al2O3 retained its bio-inertness and CNT, its bioactivity, within the composite coatings. Composite coating showed lower attachment, but higher proliferation rate, for the osteoblast cells, which has been attributed to the surface roughness. An optimized relation between coating composition, its biocompatibility and mechanical properties was established to predict the most suited coating material for orthopedic implants. HA–Al2O3–CNT composite coating displayed most improved mechanical properties while retaining its biocompatibility.