Single crystal experiments on grains of polycrystalline materials: : Oxide formation on Zr and Ta

Schultze, J.W.; Pilaski, M.; Lohrengel, M. M.; König, U.

doi:10.1039/b111216n

Cited by 43 publications

(26 citation statements)

References 23 publications

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“…In H 2 SO 4 and in the potential range up to 2 V, Ta is stable and shows immediate metal passivation [21]. Under these conditions, the growth of a compact Ta 2 O 5 film on the Ta anode is obtained [18,19].…”

Section: Resultsmentioning

confidence: 99%

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Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

et al. 2006

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The initiation and growth of porous oxide on Ta was investigated in mixed H 2 SO 4 /HF electrolytes. Under selected potentiodynamic anodic oxidation conditions the formation of nearly uniform porous Ta 2 O 5 layer was observed. The porous Ta 2 O 5 layers consist of self-organized pore arrays with single pore diameters ranging from 2 to 10 nm. The morphology and the thickness of the layer depend strongly on the applied potential, the scan rate and on HF presence. The composition of the porous oxide layer is Ta 2 O 5 .

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Section: Resultsmentioning

confidence: 99%

“…Most of the work focuses on the growth mechanism and the protective properties of the compact metal oxide under the influence of different parameters (e.g. temperature, nature of the electrolyte and its concentration) [14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

et al. 2006

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“…15,16 These challenges could be circumvented if one could directly probe the local structure of a polycrystalline sample, for example with electron backscatter diffraction (EBSD), 17 and correlate this with localized electrochemical measurements. 17,18 One approach for performing localized electrochemistry on a polycrystalline surface is to prepare an array of individually addressable micrometer scale electrodes through lithographic processing. 17 However, due to the irregular shape and size of crystalline grains, the employment of lithographic techniques to expose specific grains 4 is technically very demanding.…”

Section: Introductionmentioning

confidence: 99%

“…19,20 Another approach is to limit the contacted area of the working electrode by employing droplet based techniques. 18,[21][22][23] However, methods of this type have tended to be restricted to static point-by-point measurements (usually on a large scale), and the mapping of an area of an electrode has proved to be time consuming and difficult technically.…”

Section: Introductionmentioning

confidence: 99%

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction

et al. 2013

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The influence of electrode surface structure on electrochemical reaction rates and mechanisms is a major theme in electrochemical research, especially as electrodes with inherent structural heterogeneities are used ubiquitously. Yet, probing local electrochemistry and surface structure at complex surfaces is challenging. In this paper, high spatial resolution scanning electrochemical cell microscopy (SECCM) complemented with electron backscatter diffraction (EBSD) is demonstrated as a means of performing ‘pseudo-single-crystal’ electrochemical measurements at individual grains of a polycrystalline platinum electrode, while also allowing grain boundaries to be probed. Using the Fe2+/3+ couple as an illustrative case, a strong correlation is found between local surface structure and electrochemical activity. Variations in electrochemical activity for individual high index grains, visualized in a weakly adsorbing perchlorate medium, show that there is higher activity on grains with a significant (101) orientation contribution, compared to those with (001) and (111) contribution, consistent with findings on single-crystal electrodes. Interestingly, for Fe2+ oxidation in a sulfate medium a different pattern of activity emerges. Here, SECCM reveals only minor variations in activity between individual grains, again consistent with single-crystal studies, with a greatly enhanced activity at grain boundaries. This suggests that these sites may contribute significantly to the overall electrochemical behavior measured on the macroscale.

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“…Single grains of the polycrystalline surface are also characterized by individual crystallographic orientations, and the single grains cause anisotropic corrosion of copper, 7 iron, [8][9][10][11] magnesium, 12 titanium, 13,14 zinc, 15 tantalum and zirconium. 16 The grain boundary, which is the border of two or three single grains, also has different electrochemical reactivity from that of the single grains. 17 From the viewpoint of the universality of grain-dependent corrosion that occurs on most metallic materials, elucidation of the detailed mechanism of grain-dependent corrosion has been required.…”

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confidence: 99%

Grain-Dependent Passivation of Iron in Sulfuric Acid Solution

Takabatake

Fushimi

Nakanishi

et al. 2014

J. Electrochem. Soc.

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Passive films formed on single grains of a polycrystalline pure iron substrate were investigated in 0.05 mol dm −3 sulfuric acid with a micro-capillary cell (MCC). Passivation behavior under the condition of potentiostatic polarization was strongly dependent on the crystallographic orientation of the substrate surface. Electrochemical impedance spectroscopy revealed that the charge transfer resistance of the passivated surface was determined by the substrate orientation. Galvanostatic reduction and XPS analysis of the surface passivated using the MCC showed that the substrate orientation affected the chemical state of iron in the oxide. The results suggested that the aging of the passive film formed on the iron substrate depended on its crystallographic orientation due to the differences in surface energy of the substrate surface that has a bcc lattice structure. It was concluded that the grain dependency on the electric property of the passive film arose from the compositional differences of the oxide film. © The Author A passive film, which is a protective oxide layer that forms on a metal surface, plays an important role in preventing corrosion of metallic materials. Through many efforts made by researchers, the mechanism and the kinetics of passivation of metals have been revealed. 1,2However, heterogeneous reactions such as pitting and local corrosion that frequently occur on passivated polycrystalline surfaces have not been considered in detail due to the lack of measurement methods to focus on the heterogeneity at micro-and nano-meter scales. Since most of the metallic materials used in various fields of industry are polycrystalline rather than single crystals, anisotropic corrosion of polycrystalline metals is one of the key factors that cause heterogeneous corrosion of metals. It has been shown in studies using single crystal metals 3-6 that the crystallographic orientation of the surface has effects on the corrosion behavior of metals, such as dissolution and oxide formation rates. Single grains of the polycrystalline surface are also characterized by individual crystallographic orientations, and the single grains cause anisotropic corrosion of copper, 7 iron, 8-11 magnesium, 12 titanium, 13,14 zinc, 15 tantalum and zirconium. 16The grain boundary, which is the border of two or three single grains, also has different electrochemical reactivity from that of the single grains. 17 From the viewpoint of the universality of grain-dependent corrosion that occurs on most metallic materials, elucidation of the detailed mechanism of grain-dependent corrosion has been required.The passivation mechanism and kinetics of polycrystalline iron have been intensively investigated for more than half a century due to their importance for industry. Passivation potential, 18,19 electrolyte pH [20][21][22] and anion concentration [23][24][25] affected not only the formation rate but also the property of oxide film. Computational simulation of the oxide growth mechanism on iron was also conducted.26 Graindependent passivatio...

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Single crystal experiments on grains of polycrystalline materials: : Oxide formation on Zr and Ta

Cited by 43 publications

References 23 publications

Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction

Grain-Dependent Passivation of Iron in Sulfuric Acid Solution

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Single crystal experiments on grains of polycrystalline materials: : Oxide formation on Zr and Ta

Cited by 43 publications

References 23 publications

Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe2+/Fe3+ Redox Reaction

Grain-Dependent Passivation of Iron in Sulfuric Acid Solution

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Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction