Moving electrodes

Important features of a slip-ring motor Starting of slipring motors Hypothetical procedure to calculate the rotors resistance Speed control of slip-ring motors Moving electrode electrolyte starters and controllers... 

Convection-based systems fall into two fundamental classes, namely those using a moving electrode in a fixed bulk solution (such as the rotated disc electrode (RDE)) and fixed electrodes with a moving solution (such as flow cells and channel electrodes, and the wall-jet electrode). These convective systems can only be usefully employed if the movement of the analyte solution is reproducible over the face of the electrode. In practice, we define reproducible by ensuring that the flow is laminar. Turbulent flow leads to irreproducible conditions such as the production of eddy currents and vortices and should be avoided whenever possible. 

Note that iL depends on Vf1/2 whereas, for the wall-jet electrode, it depends on Vf4. This equation only holds for 0.1 Mass transfer is more efficient than at an RDE however, the electrode has to be smaller. Nevertheless, in applications where it is difficult to fabricate a moving electrode (i.e. photoelectrochemical and semiconductor), it could be very valuable. From the theoretical point of view all that has to be done is replace by 0.98 Vf /r% in all the equations for a rotating disc or ring--disc electrode to obtain the wall-tube analogue. In particular, the steady-state collection efficiency, N0 [eqn. (41)], is the same not only in form but also in numerical value for the same radius ratios [50] (Table 2). 

Direct reduction of metal ions is undoubtedly the electrochemical reduction process that has reached the highest degree of technical and commercial development. Fortunately, the concentration of these ions in aqueous streams and wastes is typically low, but this introduces an additional complication for their treatment because mass transfer becomes severely limited. To counter this, electrochemists have designed reactors that promote more turbulence and higher contact areas. Three-dimensional and moving electrodes offer promising alternatives. 

Mixing (moving electrodes up and down) Position, command (mix), number of times, driving way (pm)... 

We found also that the sharpness of the histogram curve depends on the speed of moving electrodes (macroscopic wires) during formation of a nanowire. Each histogram presented in this paper was obtained at a speed of 4.8 pm/s. 

The equations governing mass and charge transport in dilute solutions are derived and it is established that for many practical problems these equations can be reduced to a potential model. This model describes transport of charge in the solution and deals with electrode kinetics and mass transport in the diffusion layer which are considered as boundary conditions. Particular boundary conditions involved by resistive electrodes or coatings are also mentioned. The concepts primary, secondary and tertiary distribution are discussed and the Wagner number, characterizing a current distribution, is defined. The local form of Faraday s law is derived and extended to deal with moving electrodes. 

Classical electrochemical reactor designs invariably evolved from direct scale-up of simple laboratory electrolysis experiments. The most common example of this concept is the tank cell where an array of electrodes is immersed in a plastic or metal tank. More sophisticated versions involve a variety of approaches to enhancing convection, by rapid stirring, rotating or moving electrodes or improving geometry with plate and frame or filter-press-type cells. 

The moving electrodes include fluidized bed electrodes [25, 26], formed by individual carbon or metal particles fluidized by an appropriate flow of electrolyte, and also Circulating bed electrodes [26, 27] where the geometrical configuration promotes two differentiated zones concerning the relative motion of particles and solution one with both circulating in the same direction, the other with counter-current stream of each phase. Several less... 

Mechanical scraping which may be divided into static scraping of a moving electrode, or a static electrode with moving scrapers. 

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