Alternating current impedance measurement

Alternating current impedance measurements enjoy appreciable application in the study of a diverse range of electrochemical processes including... 

Thiele, E A. and Malten, K.E. (1973). Evaluation of skin damage. I. Skin resistance measurements with alternating current (impedance measurements), Br. J. Dermatol,... 

Significant corrosion inhibition of polyaniline-coated mild steel exposed to saline (3.59 NaCl) and acidic (0.1 N HCl) environments was reported by Thompson et al. [19]. These polyaniline coatings seemed to promote corrosion protection even where scratches existed in the protective coating. But no reliable quantitative characterization was provided in this report, and only a qualitative explanation was made from electrochemical alternating current impedance measurements or direct current linear polarization experiments. Several other conducting polymers including poly(3-hexylthiophene), poly(3-octylthiophene), poly(3-thienylmethylacetate)... 

Immittance — In alternating current (AC) measurements, the term immittance denotes the electric -> impedance and/or the electric admittance of any network of passive and active elements such as the resistors, capacitors, inductors, constant phase elements, transistors, etc. In electrochemical impedance spectroscopy, which utilizes equivalent electrical circuits to simulate the frequency dependence of a given elec-trodic process or electrical double-layer charging, the immittance analysis is applied. 

Reactance — In alternating current (AC) measurements, reactance is the imaginary part of impedance given by ... 

Anisotropic ionic conductivities were measured by an alternating current impedance method [66, 67] for the samples forming oriented monodomains in two types of cells shown in Figure 25.10. The comb-shaped gold electrodes with thickness of... 

The dielectric properties were measured by using an alternating current impedance analysis apparatus (HP-4294A). 

Electrochemical corrosion techniques are essential to predict service life in chemical and construction industries. The following direct current (dc) electrochemical methods are used in corrosion engineering practice linear polarization technique, Tafel extrapolation, and open circuit potential vs. time measurements. The alternating current (ac) technique is electrochemical impedance spectroscopy (EIS). This technique uses alternating current to measure frequency-dependent processes in corrosion and estimates the change of polarization resistance as a function of time. 

For SAMs with attached redox molecules, k (units of s ) can be measured by cychc voltammetry, chronoamperome-try (CA), alternating current impedance spectroscopy (ACIS), alternating current voltammetry (AGV), AG electroreflectance spectroscopy, and an indirect laser-induced temperature (ILIT) jump method. 

The impedance has frequently been designated as the ac impedance or the complex impedance. Both these modifiers are redundant and should be omitted. Impedance without a modifier always means impedance applying in the frequency domain and usually measured with a monochromatic signal. Even when impedance values are derived by Fourier dansformation from the time domain, the impedance is still defined for a set of individual frequencies and is thus an alternating-current impedance in character. 

Ervin, E. N., H. S. White, L. A. Baker, and C. R. Martin, Alternating current impedance imaging of high-resistance membrane pores using a scanning electrochemical microscope. Application of membrane electrical shunts to increase measurement sensitivity and image contrast. Anal. Chem., Vol. 78, 2006 pp. 6535-6541. 

The apphcation of an impressed alternating current on a metal specimen can generate information on the state of the surface of the specimen. The corrosion behavior of the surface of an electrode is related to the way in which that surface responds to this electrochemical circmt. The AC impedance technique involves the application of a small sinusoidal voltage across this circuit. The frequency of that alternating signal is varied. The voltage and current response of the system are measured. 

As with alternating electrical currents, phase-sensitive measurements are also possible with microwave radiation. The easiest method consists of measuring phase-shifted microwave signals via a lock-in technique by modulating the electrode potential. Such a technique, which measures the phase shift between the potential and the microwave signal, will give specific (e.g., kinetic) information on the system (see later discussion). However, it should not be taken as the equivalent of impedance measurements with microwaves. As in electrochemical impedance measurements,... 

The IV measurements on molecules and monolayers have been carried out almost exclusively using direct current (DC) frequency-dependent alternating current (AC) impedance measurements have rarely been performed, even though a rich spectroscopy may reveal itself, if the IV measurements were followed as a function of frequency v. 

Impedance spectroscopy is a versatile electrochemical tool, helpful to characterize the intrinsic dielectric properties of various materials. The basis of this technique is the measurement of the impedance (opposition to alternating current) of a system, in response to an exciting signal over a range of frequencies (Bard and Faulkner, 2001). 

To carry out this type of study, a small AC amplitude voltage perturbation, AV ico,/), is applied, superimposed onto a DC bias voltage component, and the resulting alternating current response and its phase, A/(co,t), is measured [123,132], Then, the electrochemical impedance of the system is thus defined as... 

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