Calcium filling of TiO2 nanotubes on the surface of NiTi shape memory alloys by plasma immersion ion implantation

In this work, a thin layer of TiO₂ is produced on the NiTi surface using oxygen plasma immersion ion implantation (O-PIII), followed by anodization in electrolytes to induce the formation of a nanotubular layer. Finally, calcium PIII is conducted to fill the TiO₂ nanotubes with calcium. Inductively-coupled plasma mass spectrometry (ICPMS) results reveal that nickel leaching can be effectively suppressed. Immersion tests in simulated body fluid (SBF) show that the Ca-filled TiO₂ nanotubular layer can accelerate the deposition of apatite on the surface consequently significantly improving the biocompatibility of NiTi SMA.