title: Formation of bioactive functionally graded structure on Ti-6Al-4V alloy by chemical surface treatment.
abstract: An Al- and V-free sodium titanate hydrogel layer with a graded structure where the sodium titanate gradually decreases toward the interior, was formed on the surface of Ti-6Al-4V alloy, when the alloy was exposed to 5M NaOH solution at 60 degrees C for 24 h. This gel layer was transformed into an amorphous sodium titanate layer without giving considerable change in the graded structure, except a little increase in the depth of the oxygen distribution by a heat treatment at 600 degrees C for 1 h. The sodium titanate layer formed Ti-OH groups on its surface by exchanging its Na+ ion with H3O+ ion in simulated body fluid when soaked in the fluid, and thus formed Ti-OH groups induced the apatite nucleation. The apatite layer also formed a graded structure toward the substrate. The strong bond of the apatite layer to the substrate was attributed to this graded structure.
authors.affiliation: Department of Material Chemistry, Faculty of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. kim@sung7.kuic.kyoto-u.ac.jp
authors.forename: H M
authors.initials: HM
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Takadama
authors.forename: F
authors.initials: F
authors.lastname: Miyaji
authors.forename: T
authors.initials: T
authors.lastname: Kokubo
authors.forename: S
authors.initials: S
authors.lastname: Nishiguchi
authors.forename: T
authors.initials: T
authors.lastname: Nakamura