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

通过在熔融金属中浸渍，从NiTi合金制备具有多孔结构的脱合金Ni表面。从NiTi基体到表面的Ni浓度以逐步的方式降低，在基体上形成内部Ti 2Ni层和外部α-Ti层。评价了从这些样品洗脱到1质量%乳酸溶液中的金属离子的量。尽管脱合金试样的表面积增加，但Ni离子洗脱被抑制到与未处理的NiTi基材相同的水平。通过两步热氧化形成的氧化层抑制了Ni离子从脱合金基体中的释放。

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.