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Petra Reinke - One of the best experts on this subject based on the ideXlab platform.
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
Journal of Physical Chemistry C, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfa...
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
The Journal of Physical Chemistry, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.
Kateryna Gusieva - One of the best experts on this subject based on the ideXlab platform.
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
Journal of Physical Chemistry C, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfa...
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
The Journal of Physical Chemistry, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.
Joachim Maier - One of the best experts on this subject based on the ideXlab platform.
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nonlinear electrical Grain boundary properties in proton conducting y bazro3 supporting the space charge depletion model
Physical Chemistry Chemical Physics, 2012Co-Authors: Mona Shirpour, Rotraut Merkle, Chengtian Lin, Joachim MaierAbstract:The overall proton conductivity of polycrystalline acceptor-doped BaZrO3 is limited by the high resistivity of its Grain boundaries. To investigate the nature of the electrical response of the Grain boundaries as a function of the DC bias, Y-doped BaZrO3 ceramics with a very large Grain size (up to 200 μm) have been prepared in an infrared image furnace. The Grains are so large that even Individual Grain boundaries can be addressed by microelectrodes. DC voltage-dependent resistance and capacitance of the Grain boundaries are discussed in terms of the space charge model. The results corroborate carrier depletion (, h˙, ) as origin of the pronounced Grain boundary resistance. This picture fits well into the space charge scenario found for various related oxide materials, and leads to strategies for improving Grain boundary conductivity.
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microcontact impedance spectroscopy at single Grain boundaries in fe doped srtio3 polycrystals
Journal of the American Ceramic Society, 2001Co-Authors: S Rodewald, Jurgen Fleig, Joachim MaierAbstract:Microcontacts on adjacent Grains of polycrystalline Fe-doped SrTiO3 samples have been used to locally investigate the properties of Individual Grain boundaries. Impedance spectroscopy was employed to separate bulk and Grain boundary impedances. Experiments at about 30 different Grain boundaries permit far-reaching conclusions on the distribution of Grain boundary resistances, capacitances, and peak frequencies measured between adjacent Grains. The rather narrow distribution of the Grain boundary peak frequencies indicates a narrow distribution of Grain boundary resistivities. All features (e.g., nonlinear current–voltage characteristics, Grain boundary thickness, temperature dependence) are in accordance with the assumption of space charge depletion layers (double Schottky barriers) as the origin of the enhanced Grain boundary resistivity. The average barrier height measured was about 630 mV. For comparison conventional (macroscopic) impedance measurements on a polycrystal were also performed and a brick layer model was used to extract effective properties. The reasonable agreement between these effective parameters and the average of the locally obtained parameters demonstrates that, in this case, a brick layer analysis of conventional impedance experiments yields satisfying estimates of the Grain boundary properties.
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microcontact impedance measurements of Individual highly resistive Grain boundaries general aspects and application to acceptor doped srtio3
Journal of Applied Physics, 2000Co-Authors: Jurgen Fleig, S Rodewald, Joachim MaierAbstract:The electrical properties of Grain boundaries in polycrystalline materials can vary from boundary to boundary and conventional impedance measurements yield only averaged information. Local measurements at Individual Grain boundaries using microelectrodes can partly overcome this restriction. Finite element calculations on the impedance of such microelectrode measurements are performed to reveal the interrelations between the measured Grain boundary impedance and the Grain boundary properties (Grain boundary resistivity, permittivity and geometry). We will discuss how far adjacent Grain boundaries influence the results. In particular, the calculations revealed that even in the case of identical Grain boundaries a considerable part of the current between two microelectrodes may flow across neighboring Grain boundaries. It is shown how these additional current paths can be taken into account with respect to a reliable data analysis. Experiments on SrTiO3 polycrystals demonstrate that spatially resolved imped...
William H Blades - One of the best experts on this subject based on the ideXlab platform.
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
Journal of Physical Chemistry C, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfa...
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
The Journal of Physical Chemistry, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.
Gopalakrishnan Ramalingam - One of the best experts on this subject based on the ideXlab platform.
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
Journal of Physical Chemistry C, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfa...
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repassivation behavior of Individual Grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
The Journal of Physical Chemistry, 2018Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, John H. Perepezko, Petra ReinkeAbstract:The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of Grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed Grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.