Calcium Phosphate Deposition on the Surface of Porous TiNi Alloys with Different Sintering Temperatures in Simulated Body Fluid

Near-equiatomic TiNi alloys were produced by powder metallurgy (P/M) using Ti and Ni powders at different temperatures (950, 1000, 1050, 1100 degrees C). To obtain a material surface having excellent affinity to bone, surface modification by hydroxyapatite coatings was conducted in a simulated body fluid (SBF). Phase composition and surface structure of Ca-P coatings were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) attached to SEM. Results indicate that porosity of TiNi alloys produced by P/M is high and peaks of hydroxyapatite is sharp. In the same experimental condition, more apatite coatings are formed on TiNi samples sintered at 1050 degrees C and 1100 degrees C due to their high porosity and pure TiNi phase, which is beneficial to heterogeneous nucleation. However, a low ion concentration region is formed in the bottom of small-sized holes, and it is not helpful to heterogeneous nucleation.