Interpreting Impedance Spectra in Time-Constant Domain: Application to the Passive Film on Titanium
Notice bibliographique
Résumé
Electrochemical impedance spectroscopy (EIS) is a useful method for characterizing the interfacial characteristics of materials such as a passive layer underneath the surface of a titanium-based metal-oxide anode. Conventionally EIS data were interpreted by fitting them with electrically equivalent circuit. However, this method requires the initial knowledge of the structure of the tested material. It is also impossible to model a system with continuous variation of layers. Normally, an electrode with finite dielectric layers can be represented by a series of RC circuits plus an interfacial impedance. To cope with the difficulty of systems with continuous variation, a distribution function may be assumed to describe the distribution of time constant along the thickness of the layers [1]. Still, this approach needs to assume a profile to which the system is restricted. A reverse approach was proposed [2]. Within a layered material, a distribution function g( τ ) of the resistance over the time-constant ( τ =RC) may result from the discrete or continuous variation of the composition (Figure1). By simply fitting the EIS data into Equation 1, one may obtain the function g(τ) , which is directly related to the layered structures of the electrode. This method was previously applied to study a transient passive layer in the Ti-supported metal oxide anode, and showed a continuum over the time constant spectrum [2]. However, direct correlation between the bands and the physically observed layers was not well established. Thus the interpretation method by time-constant domain needs to be validated. In the present work, the growth of a titanium oxide film on top of Ti was studied. This reaction is well studied. The growth kinetics and characterization of the titanium oxide film is well established [3]. Therefore it is considered to be a suitable system to test and validate the use of time-constant spectra for the interpretation of EIS. Commercially pure titanium was polarized in a pH=7 buffer containing phosphate. Preliminary data confirmed that the system showed the growth of a resistance band with a characteristic time constant (Figure 2). This band is different from the other peak representing the surface charge-transfer process. Its position was almost stationary at all voltages. Judging by its increase, it was considered to be related to the dielectric film developed on top of the Ti. Further work will focus on correlating the data with physical data, including thickness and composition information from the literature. References [1] B. Hirschorn, M. E. Orazem, B. Tribollet, et al, Electrochim. Act. , 55, 6218 (2010). [2] Q. Ni, D. W. Kirk and S. J. Thorpe, J. Electrochem. Soc. , 162, H40 (2015). [3] J. F. Vanhumbeeck and J. Proost, Corrosion Rev. , 27, 117 (2009). Figure 1
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».