I currently performed an EIS analysis but could not get a semicircle in the Nyquist plot. The material being tested in 1.5% NaCl is aluminum matrix composite (AMC) reinforced with SiC particles and coated with ZrO2 thin film by ALD. In other words, ZrO2 was deposited on AMC as a protection layer against corrosion. The frequency region was set from 100000 to 0.01 Hz. Does the result show poor coating? I wonder how I should interpret the result and what to do next.
Dear Anita Chen ,
it looks as an 'accepted protection' coating.
Try a timeline (set) of EIS-spectra[1].
However, could you show, please, the Nyquist plot in a magnified window, say: (104, 104)Ohm, or even less ?
Also, could you show, please, the bode plot(s).
1. About a long(er)-term (aging) protection coating: Try to measure an EIS-spectra, once every weekday, under the same EIS-parameters.
Dear Anita Chen
I think the potential parameter was underestimate as the inclined line corresponding to the low frequency region is strongly potential dependent, and with increasing the potential to higher value than you practiced practically, you can get an increasing tendency to move towards the real axis and finally becoming a semicircle in the medium frequency region and a straight line in the low frequency region at proper potential. Finally don't worry about coating performance before you get the right polarization potential value for the test and results analysis.
Best regards
http://www.electrochemsci.org/papers/vol16/210229.pdf
Dear Anita Chen
Can you provide Bode plot, it will be easier to visualize from the phase response.
Sometimes not so clear plots are due to drift in OCP. What is the actual impedance value you are recording before area normalization? Is the corresponding expected current well above the lower resolution of your set-up?
If you correctly presented the obtained impedance spectrum, it would turn out that the material covered with your coating exhibits typical capacitive behavior. That is, it has very good barrier properties. In the impedance spectrum, the unit on the real axis must be equal to the unit on the imaginary axis.
Best regards
stefan
For a complete (protections') confirmation, dear Dr. Chaitanya Kumar Kanukula
, (and Anita Chen), we should see/compare: two (* two[1] = 4) curves,1) before, and
2) after
protection, also.
1. E.g., a)Simulation (ECM-theoretical), and b)experimental curves.
The absence of a semicircle in a Nyquist plot (EIS) means that there is no charge transfer reaction taking place.
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