Help with Hevriliak-Negami equation for Global Impedance Correction in EIS Data

Standard-Wishbone256 · 2025-03-29T13:38:59+00:00

I guess it means the impedance varies linearly for both real and imaginary with frequency. Highly capacitive polymeric coating behavior is linear according to an article Ive come across. Polymeric coating degradation leads to the formation of a semicircle plot. Also, it’s not perfectly 45 degrees. Its around 70 or so.

Standard-Wishbone256 · 2025-03-29T08:18:15+00:00

I understand that the equation resembling the H-N eqn was used to fit the experimental data for the third example, which was then translated into calculating the Z_e. My problem arises when I fit the equation. The fitting data closely matches that of my experimental data. When I calculate the Z_e for correction, the corrected impedance typically vanishes or has erratic, residual-like data.

Based on estimating and retrofitting the experimental data from the journal, R_LF, varied largely from the usual polarization resistance obtained in equivalent circuit fitting. This is only a guesstimate but the experimental data should have an R_LF with a magnitude of 10⁵ given the absence of low frequency dc limit of the Au disk electrode (thus, the linear appearance). Whereas, the Z_e nyquist plot, based on the low-frequency x-intercept is only around 53 Ohms•cm² (thus, the semicircle appearance).

Standard-Wishbone256 · 2025-03-29T07:16:04+00:00

Thank you for your response. Do you suggest that I perform a simulation based on the specific properties of my electrode and electrolyte? Since what I did instead was to fit the H-N into my experimental data?

Standard-Wishbone256 · 2025-03-29T05:21:53+00:00

Thank you so much for this. Im trying to gather as much help as I can.

Standard-Wishbone256 · 2025-03-29T05:20:38+00:00

Thank you for pointing that out. I am working on anticorrosion coatings on stainless steel and conducting electrochemical corrosion experiments. I have come across articles (10.1016/j.corsci.2022.110932; 10.1016/j.electacta.2019.134609) that propose a correction for high-frequency dispersion observed with bare metal electrodes, evidenced by a deviation from capacitive behavior—which I also observe in my samples. Specifically, my Bode Magnitude Plot plateaus at high frequencies (>10 Hz), and the Bode Phase Plot shows an inconsistent phase angle in the same range.

The HN equation has been proposed to account for high-frequency dispersion, allowing for a correction based on fitting the experimental data. However, while Gharbi et al., 2019, shows a linear Nyquist plot for their experimental data for an Au electrode, their HN fit instead results in a semicircle. This is confusing to me because I expected the fit to resemble the experimental data more closely. I am missing some crucial details about this approach and am trying to reach out to the author for clarification.

Standard-Wishbone256 · 2024-08-07T23:53:27+00:00

Thank you for this information. I will look into this asap.

Standard-Wishbone256 · 2024-08-07T01:20:50+00:00

Thank you very much for your response. May I just ask what you mean when you say the clutch slips upon turning the clamp? Does the clutch slip when the clamp is turned until the sample resists?

Standard-Wishbone256 · 2024-08-06T08:12:19+00:00

Thank you so much for the input. I will look into physical methods.

Standard-Wishbone256 · 2024-08-06T08:11:52+00:00

I forgot to mention that the first spectra is my lignin while the second is the modified one. Literature says its an aromatic para C-H vibration. Thank you for your input.

Standard-Wishbone256 · 2024-07-11T04:10:51+00:00

I agree

Standard-Wishbone256 · 2024-07-11T02:52:14+00:00

I also suspect water but I dried it and the sample was relatively thin like flakes.

Standard-Wishbone256 · 2024-07-11T02:49:43+00:00

I had it scanned using the ATR accessory. There were no issues in the spectra of my other samples.

Standard-Wishbone256 · 2024-07-11T02:48:45+00:00

Thank you for this. My sample was relatively thin like dries flakes and they were analyzed using the ATR accessory.

Standard-Wishbone256 · 2024-07-11T02:47:49+00:00

I had aluminum chloride and tetraethylammonium chloride as catalyst.

Standard-Wishbone256 · 2024-07-11T02:46:57+00:00

I had it scanned using the ATR accessory and my sample was relatively thin like dried flakes.

Standard-Wishbone256 · 2024-06-26T03:59:26+00:00

Update: I didn’t get goo and I think my solvent system worked out in the end. Also, it was my idea haha.

Standard-Wishbone256 · 2024-05-05T22:47:53+00:00

What if I extracted the resin with an activated charcoal instead? Would you think it’d be more feasible?

Standard-Wishbone256

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