Ohmic diffusion

Problems may involve simultaneous transport and mechanical deformation transport includes Darcian, Fickian, Fourier and Ohmic diffusion. 

The polarization curves consist of two parts in the mixed ohmic-diffusion-controlled electrodeposition [12]. The first part corresponds to the ohmic control... 

The Ohmic and the Mixed Ohmic-Diffusion Control of Electrodeposition Process... 

Electrodeposition processes characterized by extremely high values of the exchange current density (/q oo) belong to the fast electrochemical processes, and they usually occur under mixed ohmic-diffusion or even full ohmic control of... 

Nikolic ND, Popov KI, Zivkovic PM, Brankovic G (2013) A new insight into the mechanism of lead electrodeposition ohmic-diffusion control of the electrodeposition process. J Electroanal Chem 691 66-76... 

Dendritic Growth Inside Diffusion Layer of the Active Macroelectrode and Ohmic Diffusion and Activation-Diffusion-Controlled Deposition and Determination of tji and tjc... 

The initiation of dendritic growth in the case of very fast electrodeposition processes also will be followed by an increase of the deposition current density, and the overall current density will be larger than the limiting diffusion current on a flat active electrode. Based on the above discussion, the polarization curve equation in the mixed ohmic diffusion-controlled electrodeposition of metals can be determined as [108] ... 

For metals characterized by io Jl (electrodeposition in mixed ohmic-diffusion control of the electrodeposition e.g., Pb and Ag), increasing concentration of metal ions causes a decrease in both and [111]. Simultaneously, opposite to electrodeposition of metals in mixed activation-diffusion control, increasing the concentration of depositing ions leads to a strong increase in the io/t r tio. 

Ohmic-Diffusion and Activation-Diffusion Controlled Deposition... 

Regardless, structural alterations and water trapped in CCL described in Section 9.2.2 about effects of freezing-thaw cycles are also causes of performance degradations during cold start. However, they are emphasized during cold start as ice is produced in the core of the CCL and near the catalytic sites. Although an active area decrease is systematically observed by CV at the CCL, preponderance between ohmic, diffusion, and activation limitations is not clearly identified. 

Fig. 7. (a) Simple battery circuit diagram where represents the capacitance of the electrical double layer at the electrode—solution interface, W depicts the Warburg impedance for diffusion processes, and R is internal resistance and (b) the corresponding Argand diagram of the behavior of impedance with frequency, for an idealized battery system, where the characteristic behavior of A, ohmic B, activation and C, diffusion or concentration (Warburg... 

Tafel slope (Napieran loop) transfer coefficient diffusion layer thickness dielectric constant, relative electric field constant = 8.85 x 10 F cm overvoltage, polarization ohmic voltage drop, resistance polarization specific conductance, conductivity electrochemical potential of material X,... 

Recent applications of e-beam and HF-plasma SNMS have been published in the following areas aerosol particles [3.77], X-ray mirrors [3.78, 3.79], ceramics and hard coatings [3.80-3.84], glasses [3.85], interface reactions [3.86], ion implantations [3.87], molecular beam epitaxy (MBE) layers [3.88], multilayer systems [3.89], ohmic contacts [3.90], organic additives [3.91], perovskite-type and superconducting layers [3.92], steel [3.93, 3.94], surface deposition [3.95], sub-surface diffusion [3.96], sensors [3.97-3.99], soil [3.100], and thermal barrier coatings [3.101]. 

The trends of behavior described above are found in solutions containing an excess of foreign electrolyte, which by definition is not involved in the electrode reaction. Without this excess of foreign electrolyte, additional effects arise that are most distinct in binary solutions. An appreciable diffusion potential q) arises in the diffusion layer because of the gradient of overall electrolyte concentration that is present there. Moreover, the conductivity of the solution will decrease and an additional ohmic potential drop will arise when an electrolyte ion is the reactant and the overall concentration decreases. Both of these potential differences are associated with the diffusion layer in the solution, and strictly speaking, are not a part of electrode polarization. But in polarization measurements, the potential of the electrode usually is defined relative to a point in the solution which, although not far from the electrode, is outside the diffusion layer. Hence, in addition to the true polarization AE, the overall potential drop across the diffusion layer, 9 = 9 + 9ohm is included in the measured value of polarization, AE. ... 

Electrochemical macrokinetics deals with the combined effects of polarization characteristics and of ohmic and diffusion factors on the current distribution and overall rate of electrochemical reactions in systems with distributed parameters. The term macrokinetics is used (mainly in Russian scientific publications) to distinguish these effects conveniently from effects arising at the molecular level. 

When only taking into account the concentration polarization in the pores (disregarding ohmic potential gradients), we must use an equation of the type (18.15). Solving this equation for a first-order reaction = nFhjtj leads to equations exactly like (18.18) for the distribution of the process inside the electrode, and like (18.20) for the total current. The rate of attenuation depends on the characteristic length of the diffusion process ... 

Ohmic losses AEohmic originate from (i) membrane resistance, (ii) resistance of CLs and diffusion layers, and (iii) contact resistance between the flow field plates. Although it is common practice to split current-voltage characteristics of an MEA into three regions— kinetic (low currents), ohmic (intermediate currents), and mass transport (high currents) [Winter and Brodd, 2004]—implicit separation of vt Afiohmic is not always straightforward, and thus studies of size and... 

Antoine O, Bultel Y, Durand R, Ozil P. 1998. Electrocatalysis, diffusion and ohmic drop in PEMFC particle size and spatial discrete distribution effects. Electrochim Acta 43 3681-3691. 

The first of these is the ohmic potential gradient, characteristic for charge transfer in an arbitrary medium. It is formed only when an electric current passes through the medium. The second expression is that for the diffusion potential gradient, formed when various charged species in the electrolyte have different mobilities. If their mobilities were identical, the diffusion electric potential would not be formed. In contrast to the ohmic electric potential, the diffusion electric potential does not depend directly on the passage of electric current through the electrolyte (it does not disappear in the absence of current flow). 

Very often, the electrode-solution interface can be represented by an equivalent circuit, as shown in Fig. 5.10, where Rs denotes the ohmic resistance of the electrolyte solution, Cdl, the double layer capacitance, Rct the charge (or electron) transfer resistance that exists if a redox probe is present in the electrolyte solution, and Zw the Warburg impedance arising from the diffusion of redox probe ions from the bulk electrolyte to the electrode interface. Note that both Rs and Zw represent bulk properties and are not expected to be affected by an immunocomplex structure on an electrode surface. On the other hand, Cdl and Rct depend on the dielectric and insulating properties of the electrode-electrolyte solution interface. For example, for an electrode surface immobilized with an immunocomplex, the double layer capacitance would consist of a constant capacitance of the bare electrode (Cbare) and a variable capacitance arising from the immunocomplex structure (Cimmun), expressed as in Eq. (4). 

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