Electrolyte diffusion coefficient

Electrolyte Diffusion Coefficient D in Units of 10 cm at Concentration (in molarity) s... 

Here, the ionic diffusion coefficient of Cl—, D, is equal to the ionic diffusion coefficient of K+, D+, and hence to the electrolyte diffusion coefficient, D of KCI. The boundary conditions for the solution of Equation 6 are... 

These equations repeat those previously set down. Flete, u is the kinematic viscosity, and a is the thermal diffusivity. The subscripts have been dropped in the convective diffusion equation, and D can be the binary diffusion coefficient, the effective electrolytic diffusion coefficient, or the diffusion coefficient of the fth species. The molar concentration is to be interpreted in the same context. In the energy equation, sometimes referred to as the heat conduction equation in the form written, heat flux due to interdiffusion and due to viscous dissipation have been neglected as small. Heat sources are also absent. 

Chokshi et al. [24] described the use of two electrochemical techniques, cyclic voltammetry (CV) and rotating disk voltammetry (RDV), to characterize oil-in-water microemulsions containing a cationic surfactant CTAB, 1-butanol as cosurfactant, -octane, and water (in the range of 90-95%). NaBr was used as the electrolyte. Diffusion coefficients of microemulsions droplets were determined using ferrocene as a hydrophobic electroactive probe. Typical voltammograms and a corresponding plot of anodic peak current versus square root of scan rate are shown in Fig. 2 [24]. The diffusion coefficient is calculated from... 

The electrolyte diffusion coefficient, (3.19), may be related to ion equivalent conductance using (3.13). Show that an alternative form for D is... 

The reader may want to better understand Figure 7.4 and Equation 7.16 by calculating the ratio of the Nemst diffusion layer to the Prandtl layer for an aqueous solution species at a given temperature and pressure using the viscosity and density of water from [Chapter 10, Table 10.22] and an electrolyte diffusion coefficient from [Chapter 10, Table 10.12]. The result of such calculations should show that at ambient conditions 8 is about 10 times smaller than 8pr. 

Figure 11.10 Diffusion coefficients of mandelic acid from gel emulsions as a function of added electrolyte. Diffusion coefficients (D) over partition coefficients (P) are also plotted...

In the latter case the diffusion coefficient D of the electrolyte is given by... 

The diffusion coefficient of oxygen in solid silver was measured with a rod of silver initially containing oxygen at a conceim ation cq placed end-on in contact with a calcia-zirconia electrolyte and an Fe/FeO electrode. A constant potential was applied across dre resulting cell... 

The behavior of ionic liquids as electrolytes is strongly influenced by the transport properties of their ionic constituents. These transport properties relate to the rate of ion movement and to the manner in which the ions move (as individual ions, ion-pairs, or ion aggregates). Conductivity, for example, depends on the number and mobility of charge carriers. If an ionic liquid is dominated by highly mobile but neutral ion-pairs it will have a small number of available charge carriers and thus a low conductivity. The two quantities often used to evaluate the transport properties of electrolytes are the ion-diffusion coefficients and the ion-transport numbers. The diffusion coefficient is a measure of the rate of movement of an ion in a solution, and the transport number is a measure of the fraction of charge carried by that ion in the presence of an electric field. 

From the value of the diffusion coefficient of Br2 in electrolyte solutions, conclu-... 

Table 9. Diffusion coefficients of Br2 in the aqueous electrolyte phase at 25 °C (taken from Ref. [68])...

A microelectrode has been used by Uchida et al. to study lithium deposition in order to minimize the effect of solution resistance [41], They used a Pt electrode (10-30 jum in diameter) to measure the lithium-ion diffusion coefficient in 1 mol L 1 LiC104/PC electrolyte. The diffusion coefficient was 4.7 x 10-6 cm2 s at 25 °C. 

The primary question is the rate at which the mobile guest species can be added to, or deleted from, the host microstructure. In many situations the critical problem is the transport within a particular phase under the influence of gradients in chemical composition, rather than kinetic phenomena at the electrolyte/electrode interface. In this case, the governing parameter is the chemical diffusion coefficient of the mobile species, which relates to transport in a chemical concentration gradient. 

T0 is a reference temperature which can be identified with T, and although the constant B is not related to any simple activation process, it has dimensions of energy. This form of the equation is derived by assuming an electrolyte to be fully dissociated in the solvent, so it can be related to the diffusion coefficient through the Stokes-Einstein equation. It suggests that thermal motion above T0 contributes to relaxation and transport processes and that... 

Figure 13. Voltage relaxation method for the determination of the diffusion coefficients (mobilities) of electrons and holes in solid electrolytes. The various possibilities for calculating the diffusion coefficients and from the behavior over short (t L2 /De ) and long (/ L2 /Dc ll ) times are indicated cc h is the concentration of the electrons and holes respectively, q is the elementary charge, k is the Boltzmann constant and T is the absolute temperature.

Siemes and Weiss (SI4) investigated axial mixing of the liquid phase in a two-phase bubble-column with no net liquid flow. Column diameter was 42 mm and the height of the liquid layer 1400 mm at zero gas flow. Water and air were the fluid media. The experiments were carried out by the injection of a pulse of electrolyte solution at one position in the bed and measurement of the concentration as a function of time at another position. The mixing phenomenon was treated mathematically as a diffusion process. Diffusion coefficients increased markedly with increasing gas velocity, from about 2 cm2/sec at a superficial gas velocity of 1 cm/sec to from 30 to 70 cm2/sec at a velocity of 7 cm/sec. The diffusion coefficient also varied with bubble size, and thus, because of coalescence, with distance from the gas distributor. 

X-ray scattering studies at a renewed pc-Ag/electrolyte interface366,823 provide evidence for assuming that fast relaxation and diffu-sional processes are probable at a renewed Sn + Pb alloy surface. Investigations by secondary-ion mass spectroscopy (SIMS) of the Pb concentration profile in a thin Sn + Pb alloy surface layer show that the concentration penetration depth in the solid phase is on the order of 0.2 pm, which leads to an estimate of a surface diffusion coefficient for Pb atoms in the Sn + Pb alloy surface layer on the order of 10"13 to lCT12 cm2 s i 820 ( p,emicai analysis by electron spectroscopy for chemical analysis (ESCA) and Auger ofjust-renewed Sn + Pb alloy surfaces in a vacuum confirms that enrichment with Pb of the surface layer is probable.810... 

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