Diffusion in binary systems

Uphill diffusion in binary systems and spinodal decomposition... 

Uphill diffusion of some components is reported in silicate melts (e.g., Sato, 1975 Watson, 1982a Zhang et al., 1989 Lesher, 1994 Van Der Laan et al., 1994). Recall that uphill diffusion in binary systems is rare and occurs only when the two-component phase undergoes spinodal decomposition. In multicomponent systems, uphiU diffusion often occurs even when the phase is stable, and may be explained by cross-effects of diffusion by other components. 

In this section it is shown how the multicomponent equations just discussed can be applied to the discussion of binary systems. First a summary is given of the various notations used in discussing two-component systems. Then some important special results are given for the diffusion and thermal diffusion in binary systems. These equations are used as the starting point for the discussions in Sec. IV. 

In the preceding section it is seen how the theory of multicomponent systems gives the correct starting formulas for the analysis of ordinary and thermal diffusion in binary systems. Whereas these latter topics have been the subject of considerable investigation, there are a number of types of more complex diffusion problems of engineering interest for which little has been done. Several of these topics are discussed here, and an attempt is made to indicate to what extent they can be interpreted in terms of the theoretical development in the preceding sections. 

Belmonte, T. and Goune, M., Numerical modelling of interstitial diffusion in binary systems Application to iron nitriding. Mater. Sci. Eng. A 302 (2001) 246-257. 

Jj is the molar flux vector for species j with respect to the mass average velocity (kmol/m s). When the flow is laminar or perfectly ordered the term V Jj results from molecular diffusion only. It can be written more explicitly as an extension, already encountered in Chapter 3, of Pick s law for diffusion in binary systems, as... 

Binder, K. (1977) Theory of the dynamics of clusters . II. Critical diffusion in binary systems and the kinetics of phase separation, Phys. Rev. B 15, 4425. 

STEADY-STATE MOLECULAR DIFFUSION IN BINARY SYSTEMS... 

TABLE 4.4 Forms of Pick s First Law of Diffusion in Binary Systems... 

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