Intragrain diffusion

Kramar N., Cosca M. A., and Hunziker J. C. (2001) Heterogeneous " °Ar distributions in naturally deformed muscovite in situ UV-laser ablation evidence for micro structurally controlled intragrain diffusion. Earth Planet. Sci. Lett. 192(3), 377-388. 

The overall conversion of the solid may then be determined by using Eq. (4.3.26). Calvelo and Smith [63] obtained numerical solution for a system with F = Fp = 3. The effect of intragrain diffusion is shown in Fig. 4.24. It is seen that as decreases, the solution approaches the = 0 asymptote. 

From the results of Section 3.3.3, it may be expected that the = 0 asymptote is valid for <0.1. In this regime the system becomes identical to the grain model presented earlier. On the other hand, when 10 the reaction of an individual grain is expected to be controlled by the intragrain diffusion. For this condition Pigford and Sliger [29] have proposed an approximate method of solution that is valid for low conversion of the solid. 

In the first case one can simply neglect the intragrain diffusion < 0.1). But when Z)g = 1.0 x 10 cm /sec, the intragrain diffusion should be taken care of, although it is not the controlling factor (when > 10, intragrain diffusion is the controlling step). 

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