Calcium filling of TiO<inf>2</inf> nanotubes on the surface of NiTi shape memory alloys by plasma immersion ion implantation

In this work, a thin layer of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanotubular layer can accelerate the deposition of apatite on the surface consequently significantly improving the biocompatibility of NiTi SMA.