Contact charging ionic

This complexity explains why definitive, quantitative verification of ionic contact charging has proved to be so elusive. Nevertheless, a body of convincing evidence for the role of ions in the charging process now exists for special categories of polymers with ionic features in their compositions. 

It has been argued in the preceding section that all surfaces carry an excess electric charge, i.e., that surfaces in contact with ionic solutions are electrified. However, the argument was made by considering an isolated piece of material unconnected to a source or sink of electrons. 

Kavan [28] and Kijima et al. [29] have used the electrochemical method to synthesize carbyne. This technique may be realized by classical electrochemistry whereby the charge transfer reaction occurs at interface of a metal electrode and liquid electrolyte solution. Electrons in reaction were supplied either through redox active molecules or through an electrode, which contacts an ionically conducting solid or liquid phase and the precursor. In general, the structure and properties of electrochemical carbon may differ considerably from those of usual pyrolytic carbons. The advantage of this technique is the synthesis of carbyne at low (room) temperature. It was shown that the best product was prepared by cathodic defluorination of poly(tetrafluoroethylene) and some other perhalo-//-alkanes. The carbyne... 

When hydrated silica is brought in contact with water, hydrated silicon atoms or silanol groups may dissociate and form electrically charged ionic sites. 

When two conducting phases come into contact with each other, a redistribution of charge occurs as a result of any electron energy level difference between the phases. If the two phases are metals, electrons flow from one metal to the other until the electron levels equiUbrate. When an electrode, ie, electronic conductor, is immersed in an electrolyte, ie, ionic conductor, an electrical double layer forms at the electrode—solution interface resulting from the unequal tendency for distribution of electrical charges in the two phases. Because overall electrical neutrality must be maintained, this separation of charge between the electrode and solution gives rise to a potential difference between the two phases, equal to that needed to ensure equiUbrium. 

Ionic species present in liquids undergo adsorption at interfaces such that predominantly one sign of charge is more strongly bound at the contacted surface than the other. This results in a bound layer close to the surface farther from which is a diffuse layer having a net countercharge. This two-layer... 

In some cases, e.g., the Hg/NaF q interface, Q is charge dependent but concentration independent. Then it is said that there is no specific ionic adsorption. In order to interpret the charge dependence of Q a standard explanation consists in assuming that Q is related to the existence of a solvent monolayer in contact with the wall [16]. From a theoretical point of view this monolayer is postulated as a subsystem coupled with the metal and the solution via electrostatic and non-electrostatic interactions. The specific shape of Q versus a results from the competition between these interactions and the interactions between solvent molecules in the mono-layer. This description of the electrical double layer has been revisited by... 

In Sec. 2 we saw that the vertical arrows in Fig. 1 denote the process of plunging ions from a vacuum into a solvent. Initially the ionic field exists in the vacuum, and we may say that, in this process, solvent molecules are introduced into this field. In fact, starting with the ion in a vacuum, the final state could equally well be reached by placing molecules in contact with the ion, and continuing to add more and more molecules until the ion is situated in a drop of liquid. In either case each vertical arrow in Fig. 1 denotes a process where solvent molecules are introduced into an intense ionic field and therefore corresponds to the process of introducing a dielectric into the gap between the plates of a condenser which already bears charges +q. 

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