X.M. Liu

BIOMIMETIC DEPOSITION OF APATITE ON SURFACE CHEMICALLY MODIFIED POROUS NiTi SHAPEMEMORY ALLOY

Porous NiTi shape memory alloy (SMA) with 48% porosity and an average pore size of 50–800 μm was synthesized by capsule-free hot isostatic pressing (CF-HIP). To enhance the surface bioactivity, the porous NiTi SMA was subjected to H2O2 and subsequent NaOH treatment. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses revealed that a porous sodium titanate (Na2TiO3) film had formed on the surface of the porous NiTi SMA. An apatite layer was deposited on this film after immersion in simulated body fluid at 37°C, while no apatite could be found on the surface of the untreated porous NiTi SMA. The formation of the apatite layer infers that the bioactivity of the porous NiTi SMA may be enhanced by surface chemical treatment, which is favorable for its application as bone implants.

Formation of CaPO 4 and suppression of Ni leaching in nitinol using oxygen and sodium plasma immersion ion implantation

This study investigates the feasibility of apatite formation and the enhancement of Ni corrosion resistance in nitinol using combined sodium and oxygen plasma immersion ion implantation. X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy are used to determine the elemental depth profiles, surface morphology, chemical composition, and reactivity of the specimens. Immersion tests in simulated body fluids and cell cultures, used to assess the bioactivity and cytotoxicity of the plasma implanted samples, show better osteoblast adhesion which indicates enhanced biological performance.