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Open AccessArticle

Characterization of Oxide Film of Implantable Metals by Electrochemical Impedance Spectroscopy

National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba-shi, Ibaraki 305-8566, Japan
Materials 2019, 12(21), 3466; https://doi.org/10.3390/ma12213466
Received: 28 September 2019 / Revised: 15 October 2019 / Accepted: 16 October 2019 / Published: 23 October 2019
The oxide film resistance (RP) and capacitance (CCPE) diagrams of implantable metals (commercially pure Ti, four types of Ti alloys, Co–28Cr–6Mo alloy, and stainless steel) were investigated by electrochemical impedance spectroscopy (EIS). The thin oxide film formed on each implantable metal surface was observed in situ by field-emission transmission electron microscopy (FE-TEM). The Ti–15Zr–4Nb–1Ta and Ti–15Zr–4Nb–4Ta alloys had higher oxygen concentrations in the oxide films than the Ti–6Al–4V alloy. The thickness (d) of the TiO2 oxide films increased from approximately 3.5 to 7 nm with increasing anodic polarization potential from the open-circuit potential to a maximum of 0.5 V vs. a saturated calomel electrode (SCE) in 0.9% NaCl and Eagle’s minimum essential medium. RP for the Ti–15Zr–4Nb–1Ta and Ti–15Zr–4Nb–4Ta alloys was proportional to d obtained by FE-TEM. CCPE was proportional to 1/d. RP tended to decrease with increasing CCPE. RP was large (maximum: 13 MΩ·cm2) and CCPE was small (minimum: 12 μF·cm−2·sn−1, n = 0.94) for the Ti–15Zr–4Nb–(0 to 4)Ta alloys. The relative dielectric constant (εr) and resistivity (kOX) of the oxide films formed on these alloys were 136 and 2.4 × 106–1.8 × 107 (MΩ·cm), respectively. The Ta-free Ti–15Zr–4Nb alloy is expected to be employed as an implantable material for long-term use. View Full-Text
Keywords: Ti–15Zr–4Nb alloy; implantable metals; oxide film resistance; capacitance; electrochemical impedance spectroscopy Ti–15Zr–4Nb alloy; implantable metals; oxide film resistance; capacitance; electrochemical impedance spectroscopy
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MDPI and ACS Style

Okazaki, Y. Characterization of Oxide Film of Implantable Metals by Electrochemical Impedance Spectroscopy. Materials 2019, 12, 3466.

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