Interpreting Impedance Spectra in the Time Constant Domain: Application to the Characterization of Passive Films

The effect of dry grinding on 304L stainless steel’s passive behavior is compared to two other surface finishing (mechanical polishing down to 2400 with SiC emery paper and 1 µm with diamond paste, respectively). The characterization of the surface state was performed using scanning electron microscopy, transmission electron microscopy, 3D optical profilometer, and X-ray diffraction. Results indicate that each surface treatment leads to different surface states. The ground specimens present an ultrafine grain layer and a strong plastic deformation underneath the surface, while an ultrafine grain layer characterizes the subsurface of the polished specimens. Grinding induces high residual compressive stresses and high roughness compared to polishing. The characterization of the passive films was performed by electrochemical impedance spectroscopy and Mott–Schottky analysis. The study shows that the semiconductor properties and the thickness of the passive films are dependent on the surface state of the 304L stainless steel.

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On the characterization of glacier response by a single time-scale

Journal of Glaciology ◽

10.3189/172756501781831837 ◽

2001 ◽

Vol 47 (159) ◽

pp. 659-664 ◽

Cited By ~ 57

Author(s):

W. D. Harrison ◽

D. H. Elsberg ◽

K. A. Echelmeyer ◽

R. M. Krimmel

Keyword(s):

Climate Change ◽

Mass Balance ◽

Time Constant ◽

Time Scale ◽

Response Models ◽

Single Time ◽

Glacier Changes ◽

Major Increase ◽

Effect Of Surface

AbstractGlacier response to climate can be characterized by a single time-scale when the glacier changes sufficiently slowly. Then the derivative of volume with respect to area defines a thickness scale similar to that of Jóhannesson and others, and the time-scale follows from it. Our version of the time-scale is different from theirs because it explicitly includes the effect of surface elevation on mass-balance rate, which can cause a major increase in the time-scale or even lead to unstable response. The time constant has a dual role, controlling both the rate and magnitude of response to a given climate change. Data from South Cascade Glacier, Washington, U.S.A., illustrate the ideas, some of the difficulty in obtaining accurate values for the thickness and time-scales, and the susceptibility of all response models to potentially large errors.

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ChemInform Abstract: Characterization of Passive Films on Zinc Electrodes by Impedance Measurements and XPS.

ChemInform ◽

10.1002/chin.199140023 ◽

2010 ◽

Vol 22 (40) ◽

pp. no-no

Author(s):

H. MISHIMA ◽

B. A. LOPEZ DE MISHIMA ◽

E. SANTOS ◽

C. P. DE PAULI ◽

K. AZUMI ◽

...

Keyword(s):

Passive Films ◽

Impedance Measurements ◽

Abstract Characterization

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Characterization of passive films on shape memory stainless steels

Corrosion Science ◽

10.1016/j.corsci.2011.12.022 ◽

2012 ◽

Vol 57 ◽

pp. 154-161 ◽

Cited By ~ 63

Author(s):

C.A. Della Rovere ◽

J.H. Alano ◽

R. Silva ◽

P.A.P. Nascente ◽

J. Otubo ◽

...

Keyword(s):

Shape Memory ◽

Stainless Steels ◽

Passive Films

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Electrochemical Characterization of Low-Temperature Direct Ethanol Fuel Cells Using Direct and Alternate Current Methods

10.26434/chemrxiv.8787311.v1 ◽

2019 ◽

Author(s):

Paweł Wnuk ◽

Rafal Jurczakowski ◽

Adam Lewera

Keyword(s):

Low Temperature ◽

Current Density ◽

Ethanol Concentration ◽

Physical Parameters ◽

Impedance Spectra ◽

Ethanol Fuel ◽

Cell Temperature ◽

Faradaic Impedance ◽

Cell Impedance

Here we report for the first time the results of systematic characterization of a low-temperature polymer electrolyte membrane direct ethanol fuel cell using DC and AC electrochemical methods. Model catalysts (carbon supported Pt nanoparticles) painted on carbon paper are used as anode and cathode. Influence of physical parameters, such as cell temperature, current density, ethanol concentration and anode fuel flow rate on overall cell impedance is studied. Analysis of the obtained impedance spectra in connection with DC measurements allows us to comment on cell properties and to separate different contributions to the overall cell polarization. Our results suggest that the cell impedance is dominated by anode faradaic impedance, with negligible contribution from cathode faradaic impedance. The anode impedance depends strongly on current density and cell temperature, but is not significantly influenced by ethanol concentration. Presence of anode mass-transfer impedance, even when ethanol was fed to the cell in high excess, is confirmed. Based on the results we conclude that changes in ethanol electro-oxidation mechanism might manifest themselves on the impedance spectra in the low-frequency inductive loop. Nonetheless, further studies involving equivalent circuit modelling are needed to determine the exact influence of the cell parameters on the anode kinetics.

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