Electrochemical dissolution, selective

In [53], oscillatory wave patterns observed during electrochemical dissolution of a nickel wire in acidic media was reported. It was shown that space-averaged potential or current oscillations are associated with the creation of an inhomogeneous current distribution, and that the selection of a specific spatial current pattern depends on the current control mode of the electrochemical cell. In the almost potentiostatic (fixed potential) mode of operation, a train of traveling pulses prevails, whereas antiphase oscillations occur in the galvanostatic (constant average current) mode. 

Utilizing the principle of the drop-off technique, electrochemical dissolution can also be controlled selectively from the microtool by applying insulation at the desired portion of the anodic electrode as shown in Fig. 6.13(a). During machining, electrochemical dissolution will not take place from the insulated area hence, the desired microtool shape can be achieved as shown in Fig. 6.13(b). 

Figure 6.18 shows SEM images of a disk microtool fabricated by selective electrochemical dissolution in EMM, and surface quality of machined surfaces at various applied voltages. It can be... 

A variant of chemical etching, electrochemical dissolution based on the principle of the dissolving anode, being a carefully selected part of the munition, offers the theoretical advantage of a wide choice of electrolytes (acids, neutrals or bases) whose composition may neutralise or even destroy the explosives and/or chemical agents. 

Chen S J, Sanz F, Ogletree D F, Hallmark V M, Devine T M and Salmeron M 1993 Selective dissolution of copper from Au-rich Au-Cu alloys an electrochemical STS study Surf. Sc . 292 289... 

There is considerable metallographic and electrochemical evidence in support of each theory and it is of interest to note that two of the most authoritative works on corrosion appear to support opposite views — Uhlig favours the selective dissolution of zinc theory, whereas Fontana and Greene favour the dissolution-precipitation theory. 

Bard AJ, Wrighton MS (1977) Thermodynamic potential forthe anodic dissolution of n-type semiconductors - A crucial factor controlling durability and efficiency in photoelectrochem-ical cells and an important criterion in the selection of new electrode/electrolyte systems. J Electrochem Soc 124 1706-1710... 

Different electrochemical surface treatments have found extensive use for the purposes of providing metal parts with particular properties, appearance, and shape. This includes the apphcation of superficial oxide or salt films (see Section 16.3), metal films (Section 16.5), and a number of methods that exploit the selective anodic dissolution of different segments of the metal surface. We examine briefly a few examples of the latter type. 

The electrochemical machining (ECM) of metals rests on the selective local anodic dissolution of metal. It is used to give metal parts the required shape and size, to drill holes, create hollows, cut shaped slots, and fashion parts of a complex pattern (e.g., the blades of gas turbines). It is an advantage of this method that it can also be used for hard metals (high-alloy steels and other alloys, metals in the quenched state, etc.). 

Dissolution media UV detection Other selective methods (electrochemical, fluorescence, etc.) Mass spectrometric detection... 

Two aspects of Table 1 are important. The standard conditions are 298 K and all reactants and products are at unity activity. The second key is the selection of the hydrogen reaction as having a standard reversible potential of 0.0 V. The table allows the first use of thermodynamics in corrosion. For a metal in a 1 M solution of its salt, the table allows one to predict the electrochemical potential below (i.e., more negative) which net dissolution is impossible. For example, at +0.337 V(NHE), copper will not dissolve to cuprous ion if the solution is 1 M in Cu2+. In fact, at more negative potentials, there will be a tendency at the metal/solution interface to reduce the cuprous ions to copper metal on the surface. 

Alloy dissolution — The process of anodic oxidation of an alloy electrode by application of a suitable - electrode potential. It leads to dissolved products. Under non-electrochemical conditions the dissolution of an alloy can be performed with a chemical oxidant The rate of dissolution depends on the structure and homogeneity of the processed material. When the applied potential or, in the case of chemical dissolution, the oxidation potential of the chemical oxidant lays between the formal potentials of the dissolved components, a selective... 

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