| Co-Investigator(Kenkyū-buntansha) |
UEDA Mikito Hokkaido Univ., Grad.School of Eng., Inst., 大学院・工学研究科, 助手 (00292053)
NOTOYA Takenori Hokkaido Univ., Grad.School of Eng., Lec., 大学院・工学研究科, 講師 (50001251)
|
|---|
| Research Abstract |
The passivation film consists of thin oxide film on metals and functions as a barrier of anticorrosion against the environmental attack. The film has been studied by many authors, however, since its thickness is in nm order, the structure, composition, etc., are not known in detail. In this research, we adopt potential-modulation reflectance (PMR) and light-induced luminescence for the study of the passivation film on iron, nickel, stainless steel, and titanium.
Nickel electrode covered by the passivation film does not reveal any rectification for the reaction current with redox species in solution, while iron, titanium, and stainless exhibit a strong suppression of the anodic current under the positive bias condition relative to the individual flatband potentials. From impedance and PMR measurement, the relation between the bias-potential and the space charge layer thickness was estimated. For the iron, stainless, and titanium, the space charge layer is formed in the film, and functions as an effective insulator barrier. For the passivation film on titanium, photo-excited luminescence was further measured as a function of anodic potential. A luminescence light with a peak about 410nm wavelength is observed, which is assumed to correspond to an inter-band deexcitation of electrons in the oxide films. An extremely weak light is also observed in a wavelength region about 720 nm. The light may reflect a surface states induced by anion adsorption.
|
