Composition and conduction mechanism of the surface oxide film on Ni-based alloys in molten hydroxide

Petia Gencheva, Tzvety Tzvetkoff, Martin Bojinov (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)

Abstract

A study of the anodic oxidation of nickel-based alloys in molten NaOH is presented, investigating the mechanism of growth, the composition and structure of the surface oxide films. The potential ranges of passivation, passivity and transpassivity have been estimated by voltammetry. Impedance measurements were performed in the passive potential region to investigate the conductivity mechanism of the oxide films. The surface and in-depth composition of the films has been estimated by X-ray photoelectron spectroscopy and Auger electron spectroscopy. As a result, the main passivation product on the Ni surface was found to be NiO. Further oxidation of the NiO layer was presumed to lead to the formation of Ni(III) ions and nickel cation vacancies. Transport of nickel cation vacancies was assumed to be the rate-limiting step of the overall process in the passive region. A tentative kinetic model of the nickel alloy/oxide/melt system is proposed to describe the impedance spectra. On the basis of the model, several kinetic and transport parameters are estimated.
Original languageEnglish
Pages (from-to)459-470
JournalApplied Surface Science
Volume241
Issue number3-4
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

Fingerprint

Nickel
Oxide films
Molten materials
Passivation
Vacancies
Cations
Positive ions
Chemical analysis
Kinetics
Nickel alloys
Anodic oxidation
Auger electron spectroscopy
Voltammetry
Oxides
X ray photoelectron spectroscopy
Ions
Oxidation
hydroxide ion

Keywords

  • nickel-based alloys
  • molten hydroxide
  • anodic oxide film
  • electrochemical impedance spectroscopy
  • point defect transport

Cite this

Gencheva, Petia ; Tzvetkoff, Tzvety ; Bojinov, Martin. / Composition and conduction mechanism of the surface oxide film on Ni-based alloys in molten hydroxide. In: Applied Surface Science. 2005 ; Vol. 241, No. 3-4. pp. 459-470.
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abstract = "A study of the anodic oxidation of nickel-based alloys in molten NaOH is presented, investigating the mechanism of growth, the composition and structure of the surface oxide films. The potential ranges of passivation, passivity and transpassivity have been estimated by voltammetry. Impedance measurements were performed in the passive potential region to investigate the conductivity mechanism of the oxide films. The surface and in-depth composition of the films has been estimated by X-ray photoelectron spectroscopy and Auger electron spectroscopy. As a result, the main passivation product on the Ni surface was found to be NiO. Further oxidation of the NiO layer was presumed to lead to the formation of Ni(III) ions and nickel cation vacancies. Transport of nickel cation vacancies was assumed to be the rate-limiting step of the overall process in the passive region. A tentative kinetic model of the nickel alloy/oxide/melt system is proposed to describe the impedance spectra. On the basis of the model, several kinetic and transport parameters are estimated.",
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Composition and conduction mechanism of the surface oxide film on Ni-based alloys in molten hydroxide. / Gencheva, Petia; Tzvetkoff, Tzvety; Bojinov, Martin (Corresponding Author).

In: Applied Surface Science, Vol. 241, No. 3-4, 2005, p. 459-470.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Composition and conduction mechanism of the surface oxide film on Ni-based alloys in molten hydroxide

AU - Gencheva, Petia

AU - Tzvetkoff, Tzvety

AU - Bojinov, Martin

PY - 2005

Y1 - 2005

N2 - A study of the anodic oxidation of nickel-based alloys in molten NaOH is presented, investigating the mechanism of growth, the composition and structure of the surface oxide films. The potential ranges of passivation, passivity and transpassivity have been estimated by voltammetry. Impedance measurements were performed in the passive potential region to investigate the conductivity mechanism of the oxide films. The surface and in-depth composition of the films has been estimated by X-ray photoelectron spectroscopy and Auger electron spectroscopy. As a result, the main passivation product on the Ni surface was found to be NiO. Further oxidation of the NiO layer was presumed to lead to the formation of Ni(III) ions and nickel cation vacancies. Transport of nickel cation vacancies was assumed to be the rate-limiting step of the overall process in the passive region. A tentative kinetic model of the nickel alloy/oxide/melt system is proposed to describe the impedance spectra. On the basis of the model, several kinetic and transport parameters are estimated.

AB - A study of the anodic oxidation of nickel-based alloys in molten NaOH is presented, investigating the mechanism of growth, the composition and structure of the surface oxide films. The potential ranges of passivation, passivity and transpassivity have been estimated by voltammetry. Impedance measurements were performed in the passive potential region to investigate the conductivity mechanism of the oxide films. The surface and in-depth composition of the films has been estimated by X-ray photoelectron spectroscopy and Auger electron spectroscopy. As a result, the main passivation product on the Ni surface was found to be NiO. Further oxidation of the NiO layer was presumed to lead to the formation of Ni(III) ions and nickel cation vacancies. Transport of nickel cation vacancies was assumed to be the rate-limiting step of the overall process in the passive region. A tentative kinetic model of the nickel alloy/oxide/melt system is proposed to describe the impedance spectra. On the basis of the model, several kinetic and transport parameters are estimated.

KW - nickel-based alloys

KW - molten hydroxide

KW - anodic oxide film

KW - electrochemical impedance spectroscopy

KW - point defect transport

U2 - 10.1016/j.apsusc.2004.07.049

DO - 10.1016/j.apsusc.2004.07.049

M3 - Article

VL - 241

SP - 459

EP - 470

JO - Applied Surface Science

JF - Applied Surface Science

SN - 0169-4332

IS - 3-4

ER -