Qualification of ECM-Processes by Electro Impedance Spectroscopy

Abstract:

Electrochemical machining (ECM) is an appropriate technology for structuring a wide range of metals and alloys independent of their mechanical properties. Further advantages the occurence of no tool wear and almost no change in the material properties of the work piece material due to the machining. As different studies showed it is possible to manufacture structures in the µm-range and also in the sub µm-range. The resulting geometry and feature size depend on the electrolyte, the working gap, the electric field, the flow conditions within the working gap and the material structure. The working gap is the most important parameter regarding the critical dimensions of ECM. Actual high resolution processes are limited by the process time due low current densities, while faster processes are limited by the resolution due to the dimensions of the double layer and the need for purging.\\Regarding these limits an enhanced understanding of the electrochemical processes within the working gap is mandatory for the optimization of the ECM. Therefore a measurement device is realised utilising electrochemical impedance spectroscopy (EIS), which is one technique to obtain a wide set of thermodynamic and kinetic parameters related to the electrochemical processes like reactions, adsorption, desorption and diffusion in the gap. There the impedance, which is the complex ratio between the voltage and the current in an AC circuit, is measured as a function of the frequency and it is compared to an equivalent circuit, composed out of basic elements representing the chemical sub processes. The spectrometer is realized by combining a commercial potentiostat with computer based signal processing realized in MATLAB\copyright. The spectrometer implements time-domain measurement techniques (Fourier transformation) for a strong reduction of measurement time. This time reduction allows in situ measurements.\\The presented spectrometer enables characterization of standard material systems like cooper, as well as the identification of the time-critical chemical processes and steps in more complex systems.

• Periodical: Key Engineering Materials (Volumes 611-612)
• Pages: 739-745
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.611-612.739
• Online since: May 2014
• Authors: Lutz Labusch*, Claas Müller, Holger Reinecke
• Keywords: ECM, Impedance Spectroscopy, In Situ Measurement

References

[1] C. H. Hamann and W. Vielstich, Elektrochemie, 4th ed. Weinheim: WILEY-VCH, (2005).

[2] A. J. Bard and L. R. Faulkner, Electrochemical methods: Fundamentals and applications, 2nd ed. New York: Wiley, (2001).

[3] A. D. Davydov, V. M. Volgin, and V. V. Lyubimov, Electrochemical machining of metals: Fundamentals of electrochemical shaping, Russ J Electrochem, vol. 40, no. 12, pp.1230-1265, (2004).

DOI: 10.1007/s11175-005-0045-8

[4] J.R. Macdonald, Ed, Impedance spectroscopy: Emphasizing solid materials and systems. New York: Wiley, (1987).

[5] P. Kurzweil and H. -J. Fischle, A new monitoring method for electrochemical aggregates by impedance spectroscopy, Journal of Power Sources, vol. 127, no. 1-2, pp.331-340, (2004).

DOI: 10.1016/j.jpowsour.2003.09.030

[6] G. S. Popkirov and R. N. Schindler, A new impedance spectrometer for the investigation of electrochemical systems, Rev. Sci. Instrum, vol. 63, no. 11, pp.5366-5366, (1992).

DOI: 10.1063/1.1143404

[7] G. Popkirov, Fast time-resolved electrochemical impedance spectroscopy for investigations under nonstationary conditions, Electrochimica Acta, vol. 41, no. 7-8, pp.1023-1027, (1996).

DOI: 10.1016/0013-4686(95)00434-3

[8] J. -S. Yoo and S. -M. Park, An Electrochemical Impedance Measurement Technique Employing Fourier Transform, Anal. Chem, vol. 72, no. 9, pp.2035-2041, (2000).

DOI: 10.1021/ac9907540

[9] M. Sluyters-Rehbach, Impedances of electrochemical systems: Terminology, nomenclature and representation - Part I: Cells with metal electrodes and liquid solutions (IUPAC Recommendations 1994), Pure and Applied Chemistry, vol. 66, no. 9, (1994).

DOI: 10.1351/pac199466091831