2016 年 63 巻 8 号 p. 766-770
NiTi has been used in biomedical implants because of its shape memory effect and superelasticity. In this study, a dealloying process was applied to NiTi substrates to form porous surfaces with low Ni content. The NiTi substrates were immersed in Ce or Mg melts for dealloying Ni. The reaction layers were characterized by using SEM/EDX and XRD. Upon dealloying, a porous layer consisting of NiTi2 and α-Ti phases was obtained at the surface of the NiTi. The Ni content in the porous layer formed at the surface of the NiTi substrate decreased step-wise until it reached a value of 2.0 at%. The thickness of the porous layer obtained by using the Ce melt was higher than that obtained by using the Mg melt, which might be due to the high affinity of Ni with Ce. 1 mass% lactic acid solution was used as an eluent for eluting Ni ions from the reaction layers. Although the amount of Ni ions eluted from the reaction layer formed by using the Ce melt was higher than that eluted from the as-polished NiTi substrate, the amount of eluting Ni ions per unit area decreased. In the case of the reaction layer obtained by using the Mg melt, the amount of eluting Ni ions was comparable with that from the as-polished NiTi substrate.
