Crystal impedance technique

Thin films of PVF exposed to non-swelling solvents are anticipated to behave as rigidly coupled masses, so that the Sauerbrey equation (equation (13.1)) accurately describes the EQCM responses. However, experimental conditions may not always conform to this situation. For example, an early EQCM study of PVF electroprecipitation yielded film mass data that were not consistent with coulometric assay of the film [39] non-rigidity of PVF films in the CH2C12 deposition solution was suggested. Also, Oyama et al. have studied thermoresponsive N-isopropylacrylamide-vinylferrocene copolymers [40] and found them to exhibit potential dependent viscoelastic characteristics. In the light of these observations, we use the crystal impedance technique (illustrated schematically in Fig. 13.1) to guide our study of PVF films. 

Lincot D, Ortega-Borges R (1992) Chemical bath deposition of cadmium sulfide thin films. In situ growth and structural studies by Combined Quartz Crystal Microbalance and Electrochemical Impedance techniques. J Electrochem Soc 139 1880-1889... 

In the event that the film is not rigid, the EQCM response is a function of both the film mass and its rheological characteristics. Application of the Sauerbrey equation under these circumstances is inappropriate it underestimates the mass change, to an extent that is dependent on the viscoelastic properties of the film. Under these circumstances, there are two questions to be addressed first, how does one diagnose film (non-)rigidity and, second, how does one interpret responses from a non-rigid film The answers to both questions can be found from crystal impedance measurements. This is a technique in which one determines the admittance (or impedance) of the loaded crystal as a function of frequency in the vicinity of resonance. Effectively, one determines the shape (width and height) and position (on the frequency axis) of the resonance, rather than just its position (as in the simple EQCM technique). 

All derivatives of the benzo-hydroxamic acid inhibited copper corrosion more effectively than BHA itself. The efficiency was affected much more by hydrophobic bulkiness in the phenyl ring than by the electronpushing or electron-attracting character of the substituents. The results attained by electrode impedance spectroscopy and quartz crystal nanobalance techniques led to recognition that the higher efficacy was not due to the inductive effect of the substituents, as both chloro and methyl substitution led to enhanced inhibition. The most important factor is the hydrophobic bulkiness. In the inhibition process, the inhibitor molecule is attached to the copper surface by the polar group (CON"), and the apolar hydro-phobic moiety may block the metal surface... 

Passive and Transpassive Dissolution of Nickel in Acidic Solutions The kinetics of nickel dissolution in the passive and transpassive ranges M remained totally unclear until the application of a very low frequency impedance technique. A general model was proposed on the basis of an extensive study of anion effects [143]. In the passive state, the fiequency domain had to be extended far below ImHz and long-term stability was obtained only by using single-crystal electrodes [144]. 

The monotonic increase of immobilized material vith the number of deposition cycles in the LbL technique is vhat allo vs control over film thickness on the nanometric scale. Eilm growth in LbL has been very well characterized by several complementary experimental techniques such as UV-visible spectroscopy [66, 67], quartz crystal microbalance (QCM) [68-70], X-ray [63] and neutron reflectometry [3], Fourier transform infrared spectroscopy (ETIR) [71], ellipsometry [68-70], cyclic voltammetry (CV) [67, 72], electrochemical impedance spectroscopy (EIS) [73], -potential [74] and so on. The complement of these techniques can be appreciated, for example, in the integrated charge in cyclic voltammetry experiments or the redox capacitance in EIS for redox PEMs The charge or redox capacitance is not necessarily that expected for the complete oxidation/reduction of all the redox-active groups that can be estimated by other techniques because of the experimental timescale and charge-transport limitations. 

Chronopotentiometry, galvanostatic transients, 1411 as analytical technique, 1411 activation overpotential, 1411 Clavilier, and single crystals, 1095 Cluster formation energy of, 1304 and Frumkin isotherm, 1197 Cobalt-nickel plating, 1375 Cold combustion, definition, 1041 Cole-Cole plot, impedance, 1129, 1135 Colloidal particles, 880, 882 and differential capacity, 880 Complex impedance, 1135 Computer simulation, 1160 of adsorption processes, 965 and overall reaction, 1259 and rate determining step, 1260... 

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