Characterization, mechanical and in vitro biological behavior of hydroxyapatite-titanium-carbon nanotube composite coatings deposited on NiTi alloy by electrophoretic deposition

In this study, the hydroxyapatite (HA)-titanium (Ti, 20 wt%)-multi-walled carbon nanotubes (MWCNTs, 1 wt%) composite coating was coated on the NiTi alloy using the electrophoretic deposition (EPD) technique and reaction bond sintering process. The FE-SEM and XRD were employed to characterize the microstructure and phase analysis of the HA, HA-Ti (20 wt%), and HA-Ti (20 wt%)-MWCNTs (1 wt%) coatings, respectively. The mechanical characteristics of the coatings were evaluated using the micro-indentation and adhesion testers. The bioactivity behavior of the coatings was assessed in a simulated body fluid by studying the growth of the apatites. In addition, the cellular behavior of the coatings was investigated using the MG63 osteoblast-like cells. The results of the FE-SEM analysis revealed the sintering of the HA coating substantially improved after composed with the titanium. Also, the hardness and adhesion strength of the HA coating improved from 72 HV and 17.2 MPa to 405 HV and 32.1 MPa, respectively, after composed with Ti and carbon nanotubes (HA-Ti(20 wt %)-MWCNTs(1 wt%) coating). Moreover, the results of the biological tests revealed an incredible improvement in the apatite and bone cell growth on the HA coatings composed with titanium and MWCNTs.