Analysis of the formation of Ta2O5 passive films in acid media through mechanistic modeling |
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| Authors: | R. Cabrera-Sierra,J. Vazquez-Arenas,S. Cardoso,R.M. Luna-Sá nchez,M.A. Trejo,J. Marí n-Cruz,J.M. Hallen |
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| Affiliation: | aInstituto Politécnico Nacional, Escuela Superior de Ingeniería Química e Industrias Extractivas, Departamento de Ingeniería Química Industrial, UPALM Ed. 7, 1er. Piso CP 07738, D.F., Mexico;bChemical Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G, Canada;cUniversidad Autónoma Metropolitana-Azcapotzalco, Departamento de Energía, Av. San Pablo No. 180, Col. Reynosa Tamaulipas, CP 02200, D.F., Mexico;dInstituto Mexicano del Petróleo, Coordinación de Ingeniería Molecular, Competencia de Química Aplicada. Eje Central Lázaro Cárdenas Norte 152, CP 07730, D.F., Mexico |
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| Abstract: | Electrochemical impedance spectroscopy (EIS) analyses are carried out to evaluate the passive features of tantalum oxide films (Ta2O5) formed at different potentiostatic conditions (0.5, 1.0, 1.5 and 2.0 V vs SSE). A supporting electrolyte of 0.1 M H2SO4 (pH 1) has been used to emulate acidic corrosive conditions for the growth of films with an n-type electronic character. A modification of the point defect model (PDM) accounting for the formation of molecular hydrogen (blistering damage) is used to fit the experimental EIS diagrams, and obtain the kinetic parameters that best describe the semiconductive behavior of the passive films. After this analysis, diffusivities in the order of 5.37 ± 1.6 × 10−17 and 1.98 ± 1.4 × 10−20 cm2 s−1 were obtained for the oxygen (DVO ) and hydroxyl vacancies (DVOH), respectively. These findings show the capabilities of the EIS and the physicochemical modeling to account for the formation of valve-metal oxide films on a different range of conditions. |
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| Keywords: | Oxygen vacancy Hydroxyl vacancy PDM Passive films Blistering |
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