Article ID Journal Published Year Pages File Type
1659597 Surface and Coatings Technology 2009 6 Pages PDF
Abstract
The surfaces of porous NiTi shape memory alloys (SMAs) were modified by double treatment of passivation (PA) in HNO3 solution and oxygen plasma immersion ion implantation (O-PIII) methods. SEM and XPS were used to characterize the modified surface. It has been found that a protective film consists of three layers formed on the surface after modification. From the outmost surface towards inside, they are a 10 nm thick layer consisting of rutile and anatase TiO2 with pure rutile TiO2 on the surface and their ratio varying in gradient, a 45 nm thick layer containing anatase TiO2 and NiTi with constant ratios and a 40 nm thick layer of TiO2, TiO and NiTi with their ratio varying in gradient. The immersion tests in simulated human body fluid demonstrated that the modified porous NiTi samples exhibit a good Ni suppression performance, approaching to that of the untreated dense NiTi samples. The Ni ion content released from the porous NiTi SMAs double treated by PA and O-PIII is one magnitude lower than that from the untreated porous samples. Moreover, the released Ni ion content after 8 weeks can be reduced into the safe range acceptable to the human body.
Related Topics
Physical Sciences and Engineering Materials Science Nanotechnology
Authors
, , , , ,