Formation of porous surface on NiTi and suppression of Ni ion release

以NiTi合金为原料，在熔融金属中浸泡，制备了具有多孔结构的脱合金化Ni表面。从NiTi基片到表面的Ni浓度逐渐降低，在基片上形成了内层Ti2Ni层和外层α-Ti层。对这些样品洗脱到质量分数为1%的乳酸溶液中金属离子的量进行了评估。尽管脱合金样品的表面积增加，但镍离子的淋洗被抑制到与未处理的NiTi衬底相同的水平。两步热氧化形成的锐钛矿层抑制了镍离子从非合金衬底中的释放。

A dealloying Ni surface having a porous structure was prepared from NiTi alloys through immersion in molten metals. The concentration of Ni from the NiTi substrate to the surface was decreased in a stepwise manner forming an inner Ti2Ni layer and outer alpha-Ti layer on the substrate. The amounts of metallic ions eluted from these specimens to 1mass% lactic acid solution were evaluated. Despite the increased surface area of the dealloyed specimen, Ni ion elution was suppressed to the same level as that in the non-treated NiTi substrate. The anatase layer formed by two-step thermal oxidation suppressed the Ni ion release from the dealloyed substrate.