Admittance data

Horton and Price (H11) have obtained acoustic-admittance data for a series of double-base and composite propellants with different burning-rate characteristics. They examined the effects of pressure at various frequencies... 

Horton (H9, H10) has obtained additional acoustic-admittance data for a series of composite propellants. At a given frequency, decreasing the mean oxidizer particle size increases the acoustic admittance and thereby the tendency for instability. Horton also investigated the effects on the acoustic admittance of the incorporation of traces of copper chromite, a known catalyst, for the decomposition of ammonium perchlorate, lithium fluoride (a burning-rate depressant), and changes in binder these data are difficult to analyze because of experimental errors. 

In this section, the interpretation of interfacial admittance data in the case of an a.c. reversible reaction with adsorption of O is briefly described. The relationships expressing the frequency dependence were derived some time ago [15, 17], but the essential meaning of the parameters involved was fully explained only recently [143], The brief description here is derived from the latter reference. 

J. R. Macdonald and J. A. Garber, "Analysis of Impedance and Admittance Data for Solids and Liquids," Journal of The Electrochemical Society, 124 (1977) 1022-1030. 

B. Boukamp, "A Package for Impedance/Admittance Data Analysis," Solid State Ionics, Diffusion Reactions, 18-19 (1986) 136-140. 

Admittance data are plotted in the following two ways 1. As magnitude,... 

Figure 3. Admittance data from a K +-conducting membrane and curve fits (solid curves) of eqs 2, 3, and 4 with Y /jf,) = 0 plotted in the complex plane [X(f) vs. R(f)] as impedance [Z(jf) = R(f) + jX(f) = Y 1(jf/)] loci (400 frequency points) over the 12.5 5000-Hz frequency range. These data were acquired rapidly as complex admittance data, as illustrated in Figure 1, at premeasurement intervals of 0.1 and 0.5 s after step voltage clamps to each of the indicated membrane potentials from a holding of —65 mV. The near superposition and similarity in shape of the two loci at 0.1 and 0.5 s, at each voltage, indicates that the admittance data reflect a steady state in this interval after step clamps. Axon 86-41 internally perfused with buffered KF and externally perfused in ASW + TTX at 12 °C. The membrane area is 0.045 cm2.

Note All values are given in milliseconds and are taken from fits of the admittance data plotted as impedance loci in Figure 3 at the two premeasurement intervals (PMI) 0.1 and 0.5 s after step changes to membrane voltage, V. 

Best Fits of Impedance Data with the YNa( jf) Model. After the existence of a steady-state condition 20 ms after step clamps was established, we acquired a set of admittance data in the 5-2000-Hz frequency range in a Na+-conducting axon at a premeasurement interval of 100... 

Figure 5. Admittance data plotted as magnitude and phase angle vs. frequency as determined at the three premeasurement intervals (20, 100, and 200 ms) shown in Figure 2 and at the indicated membrane voltages. The superposition of the admittance data at each voltage indicates that the admittance is time-invariant in the interval from 20 to 200 ms after step changes in membrane voltage. Axon 87-19 internally perfused with the perfusate described in the text and externally perfused with ASW at 8 °C.

Figure 6. Admittance data from a Na+-conducting membrane and curve Jits (solid curves) of eqs 2, 3, and 5 with YK()f) = 0 plotted in the complex plane [X(f) vs. R(f)] as impedance loci (400 frequency points) over the frequency range 5 to 2000 Hz. Same axon and conditions as in Figure 5.

In order to test the instrument and the data analysis procedures we made a number of experiments on dummy cells, for example the one shown in Fig.6. Here we made use of the possibility of time-domain averaging, the ac excitation was repeated 8 times and the data were averaged. The dummy cell was enclosed in a Faraday cage and the noise level was quite low, reducing the need for frequency-domain averaging, i.e., averaging of admittance data, after Fourier transformation and calculation of the admittance. 

STORE Performs RCSUB on all admittance data and writes corrected data on magnetic tapes. 

An important finding by Yamamoto and Yamamoto (1976) was that the impedance of the removed SC layers did not produce a circular arc in the complex impedance plane. This is obvious from Figure 4.19, in which the admittance data from Figure 4.17 have been transformed to impedance values and plotted in the complex plane. 

Suppose that we have obtained the measurement results shown in Table 9.6. The table contains raw data, as for instance obtained directly from a lock-in amplifier. It is admittance data according to Y = G + jB, and the results are given in microsiemens. 

Boukamp, B.A. 1986. A package for impedance/admittance data analysis. Solid State Ionics 18-19 (1) 136. 

J. R. Macdonald, A. Hooper, and A. P. Lehnen [1982] Analysis of Hydrogen-Doped Lithium Nitride Admittance Data, Solid State Ionics 6, 65-11. 

The Applicability and Power of Complex Nonlinear Least Squares for the Analyses of Impedance and Admittance Data, J. Electroanal. Chem. 131, 77-95. 

Y.-T. Tsai and D. W. Whitmore [1982] Nonlinear Least-Squares Analysis of Complex Impedance and Admittance Data, Solid State Ionics 1, 129-139. 

G. G. Roberts and coworkers deposited monolayers of diyne fatty adds on the surface of the narrow band gap semiconductor Hg Cdj Te, utilized in the fabrication of infrared detection devices. Admittance data determined after polymerization of the amphiphiles compared favourably with data obtained for equivalent devices with inorganic insulators. Hence, an application for passivating semiconductor surfaces seems feasible. 

Therefore admittance data can also be plotted in the complex plane (V versus F with (o implicit). Some researchers choose to display data in terms of the complex capacitance C( o>) here C( a>) = Y j(o)lj(o. The latter type of representation can be useful when examining the electrochemical response of electronically conducting polymer films. The low-frequency redox pseudocapacitance can be read directly from a plot of C" versus C at low frequency. 

McKubre and Syrett (1983, 1988) were the first to adapt the method of harmonic analysis for the control of the corrosion rate of cathodically polarized systems. They presented a theoretical description of the problem and developed the measuring technique by making measurements over a wide range of frequencies from 1 Hz to 10 kHz. The method applied by them is known in the literature as harmonic impedance spectroscopy (HIS). It is based on the measurement of the zero, first, second, and third harmonics of the current response of an electrode perturbed by a voltage sinusoid signal. The elaborate mathematical treatment of results theoretically gives the possibility of obtaining admittance data independent of the frequency. The numerical solution of a system of three equations with three unknowns allows the determination of required AE, b, and values, and finally the corrosion current. The authors of the HIS method carried out attempts to determine the corrosion rate of copper-nickel alloys, steel, and titanium under cathodic protec-... 

Blasco J., Garcia J. Structural, magnetic and electrical-properties of NdNi Fe 03 and NdNii ,Co03 systems. J. Phys. Chem. Solids 1994 55 843-852 Boukamp B.A. A nonlinear least-squares fit procedure for analysis of immittance data of electrochemical system. Solid State Ionics 1986 20 31-44 Boukamp B.A. A package for impedance admittance data-analysis. Solid State Ionics 1986 18 136-140... 

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