Study of pulse electrodeposition of calcium phosphate on anodized surface of Nitinol alloy

Over the last decades Nitinol alloys are very promising biomaterials for orthopedic implants due to their unique properties including super-elasticity, shape memory effects as well as similarity of their mechanical properties to natural bone. But Nitinol alloys are bio-inert to obtain bioactivity and consequently enhancement their osteointegration, itseems that applying calcium phosphate coating on their surface can be useful. Therefore, in this study, anodized surfaces of Nitinol samples were coated by calcium phosphate using pulsed electrodeposition method. Field emission-scanning electron microscope (FESEM)and Grazing incident beam XRD were employed in order to characterize the anodized surfaces. Also, the obtained calcium phosphate layer was analyzed by SEM, EDS, FTIR and XRD. The effect of this bioactive coating as well as anodizing on thedecreasing release of the toxic Ni ions from Nitinol substrate were investigated by AAS, meanwhile bonding strength was studied by tensile strength test machine. The resultsindicate that, anodizing method promotes the formation of more uniform and cracks free coating containing mostly HA phase as a most stable phase among all of calciumphosphate phases. On the other hand the existence of barrier TiO2 layer formed during anodizing and HA coating could significantly decrease from 143.5μg/Lcm2 to 9.5μg/Lcm2 the Ni releasing. Additionally, bonding strength of coating were increased from 11.1 MPa to 24.5 Mpa owing to the formation of porous anodized surface and so inducing mechanical locks between this surface with calcium phosphate coating.

کلیدواژه ها:

Nitinol ، Anodizing ، Calcium phosphate ، Pulse electrodeposition