Diffusion during cooling

These solutions are used often in treating diffusion during cooling. 

Spear F. S. (1991) On the interpretation of peak metamorphic temperatures in fight of garnet diffusion during cooling. J. Metamorph. Geol. 9, 379-388. 

The Dodson equation (Eqn. 9) defines Tc strictly in terms of diffusion. Use of Tc (Eqn. 9) implicitly assumes that other processes are not important. The strong dependence of diffusion coefficient on temperature (Eqn. 5) causes the transition from rapid to slow diffusion during cooling to be over a relatively small temperature interval. Dodson (1973, 1979) presented an equation for the closure temperature, Tc of a single mineral ... 

Figure 5-14 Diffusive loss of Ar that was initially in hornblende during cooling after complete cooling down t=rx>) for asymptotic cooling history with (a) a fixed cooling timescale but varying the initial temperature and (b) a fixed initial temperature but varying the cooling rate.

Fig. 2. Deuterium (D) and free carrier concentration (n) profiles of a n-type GaAs Si bulk sample exposed to a rf deuterium plasma for 90 min. at 250°C (rf power density = 0.2W/cm2). The loss of free carriers occurring only in.the deuterated region suggests that hydrogen plays a major role in the free carrier concentration decrease. The deuterium concentration drop in the near surface region is attributed to a deuterium out-diffusion during the cooling stage of the sample with the plasma off. J. Chevallier et al., Materials Science Forum, 10-12, 591 (1986). Trans. Tech. Publications.

The volume decrease accompanying formation of intermetallic compounds produces a bulk dilation stress over the whole thickness of growing layers. Thermal expansion of the couple constituents during heating up as well as their contraction during cooling down in the course of successive anneals of the same couple produces a shear stress. These inevitably lead to the rupture of Ni-Zn and Co-Zn diffusion couples, with the latter effect being most disastrous. 

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