Novel carbon nanotubes reinforced Ti28Nb35.4Zr matrix composites fabricated via direct metal deposition for bone implant applications

In this study, new β Ti-28Nb-35.4Zr (hereafter denoted TNZ) and multi-walled carbon nanotubes (MWCNTs; 0.1 wt.%) reinforced TNZ composite (hereafter denoted TNZCNT) were manufactured for bone implant applications via direct metal deposition (DMD). The effect of MWCNTs addition was systematically investigated on the microstructure and resultant mechanical, nano-tribological, and biocompatibility properties of TNZ. Results indicated that the microstructures of TNZ and TNZCNT composite were primarily composed of β along with localized α″ martensite phases. TNZ and TNZCNT composite exhibited average compressive yield strengths of 706 MPa and 833 MPa, respectively, with outstanding plastic deformation ability (>55%) without forming cracks and fractured surfaces under high compressive loads. Average nanohardness of TNZ and TNZCNT composite was measured as 2.9 GPa and 3.4 GPa, respectively. Compared to average wear volume of TNZ counterpart (0.19 µm3), nano-tribological tests also revealed higher resistance of TNZCNT composite to wear (0.07 µm3) owing to its higher hardness. MTS assay revealed that both TNZ and TNZCNT composite exhibit high viabilities of SaOS2 cells measured as 97.6% and 107.6%, respectively, after 7 d of cell culturing. Moreover, TNZCNT composite exhibited thriving adhesion and spreading of SaOS2 cells showing their growth and proliferation on its surface after cell culture for 1 and 7 d, demonstrating its extraordinary biocompatibility. Overall, owing to their appropriate mechanical, nano-tribological, and biocompatibility properties, the DMD-manufactured TNZ and TNZCNT composite displayed promising potential to be utilized as a candidate material for load-bearing implant applications.