Effect on diffusivity

From various studies" " it is becoming clear that in spite of a heat flux, the overriding parameter is the temperature at the interface between the metal electrode and the solution, which has an effect on diffusion coefficients and viscosity. If the variations of these parameters with temperature are known, then / l (and ) can be calculated from the hydrodynamic equations. 

Alsairafi, A., Lee, S.T., and T ien, J.S., Modeling gravity effects on diffusion flames stabilized around a cylindrical wick saturated with liquid fuel. Combust. Sci. Technol., 176, 2165, 2004. 

Thamer, B.J., Nielson, K.K., and Felthauser, K., The Effects of Moisture on Radon Emanation Including the Effects on Diffusion, Report BuMines 0FR 184-82, PB83-136358, U.S. Dept, of Commerce,... 

Shapes of pores have a great effect on diffusion through them. They are greatly varied and usually cannot be observed directly for commercial materials. For theoretical comparisons they may be assumed parallel cylinders of some mean diameter. Diffusion experments also have been performed with parallel small capillaries. 

Thus, the whole area of fillings for the large lattices considered is concentrated into a narrow range of threshold values of ZB, and ZBpercolation processes, since the sites bound to them are filled through wider bonds. One should expect that nonpercolation bonds have a relatively small effect on diffusion mass transfer that extends from the external surface of a lattice to its bulk. 

The band positions of Fe oxides are also influenced by the substitution for Fe by other cations in the structure, as indicated partly by their colour. Scheinost et al. (1999) noticed a linear shift in the position of the Ai " Ti transition from 943 to 985 nm and that of the Ai " T2 transition from 653 to 671 nm for 47 synthetic goethites whose Al-substitution (Al/(Al-i-Fe) ranged between 0 and 0.33 mol mol (R = 0.92 for both). Mn "-substituted goethites showed bands arising from Mn " near 454 and 596 nm. The overall reflectivity in the visible range decreased as structural Mn increased from 0 to 0.20 mol mol (Vempati et al., 1995). The same effect has been observed for V "-substituted goethites (Schwertmann Pfab, 1994). The position of the EPT band of Mn "-substituted hematite shifted to 545 nm and that of the Ai " T2 transition to 700 nm (Vempati et al., 1995). The position of the same transition shifted from ca. 600 to 592 nm as the Al-substitution in hematite rose from 0 to 0.125 mol mol (Kosmas et al., 1986). Crystal size and crystal shape also have an effect on diffuse reflectance, as shown for hematite (see Fig. 6.12). As the crystals become smaller, reflectance increases and needles also reflect more than cubes, i. e. the colour becomes more vivid. 

Radiation damage may cause at least two effects on diffusion. One is that radiation damage results in defects in crystalline structures, and they facilitate diffu-... 

Notice the similarity in form of Eq. (4.65) with Eq. (4.7), which used the packing fraction to estimate the viscosity. In this case, however, the dependences are the inverse of packing fraction and molecular weight to those in Eq. (4.7). In other words, whatever factors that change viscosity will have the opposite effect on diffusion. As viscosity goes up, diffusivity goes down the inverse is true as well. This relationship is stated... 

Anisothermal Transport Across a Phase Boundary. Once we know the effect of temperature on equilibrium position, we need know only its effects on diffusivities and the condensation coefficient to complete our task. The Stephan-Maxwell equation states that diffusivity in the vapor increases with the square root of the absolute temperature. In the condensed phase the temperature effect is expressed by an Arrhenius-type equation. 

Ion-Binding Effects on Diffusion of Reversibly Dissociating Lobster Hemocyanin... 

I 76) Gary-Bobo, C. M., Rigaud, J. L. Hydration Effect on Diffusion in Lecithin-Water Lamellar Phase, in 14). 

Reactions in biphasic systems can take place either at the interface or in the bulk of one of the phases. The reaction at the interface depends on the reactants meeting at the interface boundary. This means, the interface area as well as the diffusion rate across the bulk of the phase plays an important role. On the contrary, in reactions that take place in the bulk phase, the reactants have to be transferred first through the interface before the reactions take place. In this case, the rate of diffusion across the interface is an important factor. Diffusion across the interface is more complicated than the diffusion across a phase, as the mass transfer of the reactant across the interface must be taken into account. Hence, the solubility of the reactants in each phase has to be considered, as this has an effect on diffusion across the interface. In a system where the solubility of a reactant is the same in both phases, the reactant diffuses from the concentrated phase to the less concentrated phase across the interface. This takes into account the mass transfer of the reactant from one phase into the other through the interface. The rate of diffusion J in such systems is described in Equation 4.1, where D is the diffusion coefficient, x is the diffusion distance and l is the interface thickness (Figure 4.9). 

---