Electrolyte solutions frictional coefficient

Finally, if the sliding surfaces are in contact with an electrolyte solution, an analysis indicates that the coefficient of friction should depend on the applied potential [41]. 

Historically, one of the central research areas in physical chemistry has been the study of transport phenomena in electrolyte solutions. A triumph of nonequilibrium statistical mechanics has been the Debye—Hiickel—Onsager—Falkenhagen theory, where ions are treated as Brownian particles in a continuum dielectric solvent interacting through Cou-lombic forces. Because the ions are under continuous motion, the frictional force on a given ion is proportional to its velocity. The proportionality constant is the friction coefficient and has been intensely studied, both experimentally and theoretically, for almost 100... 

Stochastic dynamics The stochastic dynamics (SD) method is a further extension of the original molecular dynamics method. A space-time trajectory of a molecular system is generated by integration of the stochastic Langevin equation which differs from the simple molecular dynamics equation by the addition of a stochastic force R and a frictional force proportional to a friction coefficient g. The SD approach is useful for the description of slow processes such as diffusion, the simulation of electrolyte solutions, and various solvent effects. 

In 1933 Debye published a theoretical study in which he predicted the origination of an electric field, the so-called ionic vibration potential (IVP), upon the passage of ultrasonic waves through electrolyte solutions [34]. Debye outlined that ultrasonic waves should cause the separation of charges due to the differences in the effective masses and friction coefficients of the solvated anions and cations, and suggested that such an effect might serve as a means... 

Atomic force microscopy has been combined with nano-indentation and nano-scratching studies [95]. The hardness (and, to a similar extent, the friction coefficient) of passivated titanium was three to four times higher under in situ conditions, this was assigned to a much faster repassivation process in the presence of the passivating electrolyte solution. Nanotribology, particularly surface friction forces mea-... 

A reciprocating motion set-up involves the back-and-forth motion between a ball or a pin and a flat plate. The friction coefficient is obtained from the measurement of the normal and the tangential forces. This type of set-up can be easily adapted to the study of tribocorrosion behavior in electrolyte solutions. For this, the contact is immersed in the electrolyte that is contained in a cell equipped with a reference electrode and a counter electrode. The rubbing metal surface is branched as the working electrode in a potentiostatic circuit, which permits to perform rubbing experiments under potential control. The friction coefficient shown in Figure 10.11 was determined in this way by scanning the potential of the stainless steel in the positive direction. 

The same equation (2) was also used by Spikes et al. to model the classical friction coefficient in the presence of electrochemical effects between two metal oxide surfaces in aqueous solutions onamacroscopic scale [29,30] and by Lin et al. to model force interactions between tip and surface in an electrolyte for larger separations [18]. 

We presented the consequences of assuming that an ion moving through a solution experiences a frictional force proportional to its speed with a proportionality constant called a friction coefficient. It was shown that this assumption leads to Ohm s law for an electrolyte solution, with a conductivity contribution for each type of ion that is inversely proportional to the friction coefficient. 

In Ref. 76, self-consistent expressions were derived for the frequency-dependent electrolyte friction and the conductivity. Unlike our approach, the effect of the surrounding solvent (water) was described using the phenomenological coefficients. However, no oscillatory component of ct co) or cr"(co) were discovered in Ref. 157, while our Figs. 48 and 49 show typical damped oscillations. A reservation should be made that no damped oscillations are seen in the case of a solution (see Fig. 50), if we employ the additivity approximation Eq. (387). 

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