Electrolytic phenomenon

The concept of ECG was introduced by McGeough (1974). The electrolyt-ically conductive metal-bonded wheel is the anode and a fixed graphite stick is the cathode. The dressing process is an electrolytic phenomenon. Wlech et al. (1993) employed this principle but they used sodimn chloride solution as the electrolyte, which is harmful for machine tools. 

It is interesting to address the electronic property of CH3 Si(lll)-(l x 1) not only for the purpose of application as the lithography resist layer hut also as the basis of nanoelectronic devices. The I-V characteristic curve of STM reached a peak at —1.5 eV in the occupied levels additionally to the I-V curve of H Si(lll). This peak corresponds to the electronic state that contributes to electronic conduction through the surface. This conducting property is also materialized in an electrolytic phenomenon. Niwa etal. [61] demonstrated that CH3 Si(lll)-(1x1) as an electrode in an aqueous... 

The difference in performance between stainless steel filament yam electrodes and silver-coated PBO filament yam electrodes could be explained by the electrolytic phenomena observed by Bhattacharya [12] in their devices with silver-coated yam electrodes in the electron microscope measurement, they clearly observed migration of silver particles with the silver-coated yam electrodes. PEDOT PSS acted as an electrolyte that silver could migrate through in the presence of an electric field. There was also a possibility of chemical interaction at the silver/PEDOT PSS interface. However, with the stainless steel filament yam electrode, it is not clear if the electrolytic phenomenon exists in the first place, but this opens up the complexity in the mechanism of charge storage in these fabricated devices. Nevertheless we realized that the stainless steel filament yams had better performance in the fabricated cells. 

Salts of acids other than hydrochloric acid commonly show increased solubiUty in hydrochloric acid. This phenomenon has been explained by the Debye-Hbckel theory for strong electrolytes (17—19). 

Anodic oxide formation Lakhiani and Shreir have studied the anodic oxidation of niobium in various electrolytes, and have observed that temperature and current density have a marked effect on the anodising characteristics. The plateau on the voltage/time curve has been shown by electron microscopy to correspond with the crystallisation of the oxide and rupture of the previously formed oxide. It would appear that this is a further example of field recrystallisation —a phenomenon which has been observed previously during anodisation of tantalum" . No significant data on the galvanic behaviour of niobium are available however, its behaviour can be expected to be similar to tantalum. 

Corresponding to the charge in the potential of single electrodes which is related to their different overpotentials, a shift in the overall cell voltage is observed. Moreover, an increasing cell temperature can be noticed. Besides Joule-effect heat losses Wj, caused by voltage drops due to the internal resistance Rt (electrolyte, contact to the electrodes, etc.) of the cell, thermal losses WK (related to overpotentials) are the reason for this phenomenon. 

Usually, this phenomenon limits the lifetime of a battery because the storage capacity falls below a reasonable lower limit. One reason for this zinc migration was identified by McBreen [35] an inhomogeneous current distribution makes the zinc move away from high current density areas. Another mechanism seems to be active as well an electrolyte convection induced by electro-osmosis through the separator [36],... 

Using dilatometry in parallel with cyclic voltammetry (CV) measurements in lmolL 1 LiC104 EC-l,2-dimethoxy-ethane (DME), Besenhard et al. [87] found that over the voltage range of about 0.8-0.3 V (vs. Li/Li+), the HOPG crystal expands by up to 150 percent. Some of this expansion seems to be reversible, as up to 50 percent contraction due to partial deintercalation of solvated lithium cations was observed on the return step of the CV. It was concluded [87] that film formation occurs via chemical reduction of a solvated graphite intercalation compound (GIC) and that the permselective film (SEI) in fact penetrates into the bulk of the HOPG. It is important to repeat the tests conducted by Besenhard et al. [87] in other EC-based electrolytes in order to determine the severity of this phenomenon. 

Siemes and Weiss (SI4) investigated axial mixing of the liquid phase in a two-phase bubble-column with no net liquid flow. Column diameter was 42 mm and the height of the liquid layer 1400 mm at zero gas flow. Water and air were the fluid media. The experiments were carried out by the injection of a pulse of electrolyte solution at one position in the bed and measurement of the concentration as a function of time at another position. The mixing phenomenon was treated mathematically as a diffusion process. Diffusion coefficients increased markedly with increasing gas velocity, from about 2 cm2/sec at a superficial gas velocity of 1 cm/sec to from 30 to 70 cm2/sec at a velocity of 7 cm/sec. The diffusion coefficient also varied with bubble size, and thus, because of coalescence, with distance from the gas distributor. 

Some interesting results have been obtained by Akand and Wyatt56 for the effect of added non-electrolytes upon the rates of nitration of benzenesulphonic acid and benzoic acid (as benzoic acidium ion in this medium) by nitric acid in sulphuric acid. Division of the rate coefficients obtained in the presence of nonelectrolyte by the concentration of benzenesulphonic acid gave rate coefficients which were, however, dependent upon the sulphonic acid concentration e.g. k2 was 0.183 at 0.075 molal, 0.078 at 0.25 molal and 0.166 at 0.75 molal (at 25 °C). With a constant concentration of non-electrolyte (sulphonic acid +, for example, 2, 4, 6-trinitrotoluene) the rate coefficients were then independent of the initial concentration of sulphonic acid and only dependent upon the total concentration of non-electrolyte. For nitration of benzoic acid a very much smaller effect was observed nitromethane and sulphuryl chloride had a similar effect upon the rate of nitration of benzenesulphonic acid. No explanation was offered for the phenomenon. 

As a metal is brought in contact with an electrolyte, various phenomena occur that result in the onset of an electric potential difference (0M -0s), where M and S stand for metal and solution (the most usual electrolyte), respectively. The kind of phenomenon depends on the nature of the... 

The numerical calculation of the potential-dependent microwave conductivity clearly describes this decay of the microwave signal toward higher potentials (Fig. 13). The simplified analytical calculation describes the phenomenon within 10% accuracy, at least for the case of silicon Schottky barriers, which serve as a good approximation for semiconduc-tor/electrolyte interfaces. The fact that the analytical expression derived for the potential-dependent microwave conductivity describes this phenomenon means that analysis of the mathematical formalism should... 

By 19884 it became obvious that the NEMCA effect, this large apparent violation of Faraday s law, is a general phenomenon not limited to a few oxidation reactions on Ag. Of key importance in understanding NEMCA came the observation that NEMCA is accompanied by potential-controlled variation in the catalyst work function.6 Its importance was soon recognized by leading electrochemists, surface scientists and catalysis researchers. Today the NEMCA effect has been studied already for more than 60 catalytic systems and does not seem to be limited to any specific type of catalytic reaction, metal catalyst or solid electrolyte, particularly in view of... 

Most of the electrocatalysts we will discuss in this book are in the form of porous metal films deposited on solid electrolytes. The same film will be also used as a catalyst by cofeeding reactants (e.g. C2H4 plus 02) over it. This idea of using the same conductive film as a catalyst and simultaneously as an electrocatalyst led to the discovery of the phenomenon of electrochemical promotion. 

This observation immediately rules out the possibility that NEMCA is an electrocatalytic phenomenon causing only a local acceleration of the catalytic rate at the three-phase-boundaries (tpb) metal-solid electrolyte-gas. In such a case the rate increase would obviously be instantaneous during a galvanostatic transient. 

When first discovered in the eighties as a pronounced apparent violation of Faraday s law it looked like a phenomenon of limited importance, praised however already by several leading electrochemists and surface scientists including Bockris21 and Pritchard.22 The subsequent involvement of the groups of Comninellis, Haller, Lambert, Sobyanin, Anastasijevic, Smotkin and others and the continuous discovery of new electrochemically promoted reactions broadened substantially the horizons of electrochemical promotion as it became obvious that the phenomenon was not limited to any particular electrolyte, conductive catalyst or type of reaction. 

In 1861, Georg Hermann Quincke described a phenomenon that is the converse of electroosmosis When an electrolyte solution is forced through a porous diaphragm by means of an external hydrostatic pressure P (Fig. 31.1ft), a potential difference called the streaming potential arises between indicator electrodes placed on different sides of the diaphragm. Exactly in the same sense, in 1880, Friedrich Ernst Dorn described a phenomenon that is the converse of electrophoresis During... 

A more sophisticated approach takes into account the fact that the presence of the reacting ion at a given point in the solution distorts the distribution of other ions of the electrolyte and thereby distorts the potential distribution. This phenomenon is called the effect of the micropotential. The average /i potential is then replaced by another average potential, calculated in the presence of the reacting ion at a given point. 

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