Morphology coarsening

Note 3 Morphology coarsening can be substantially stopped by, for example, vitrification, crosslinking, and pinning, the slowing down of molecular diffusion across domain interfaces. 

Thus, one could expect to find a droplet morphology at those quench conditions at which the equilibrium minority phase volume fraction (determined by the lever rule from the phase diagram) is lower than the percolation threshold. However, the time interval after which a disperse coarsening occurs would depend strongly on the quench conditions (Fig. 40), because the volume fraction of the minority phase approaches the equilibrium value very slowly at the late times. 

Note 2 Representative mechanisms for coarsening at the late stage of phase separation are (1) material flow in domains driven by interfacial tension (observed in a co-continuous morphology), (2) the growth of domain size by evaporation from smaller droplets and condensation into larger droplets, and (3) coalescence (fusion) of more than two droplets. The mechanisms are usually called (1) Siggia s mechanism, (2) Ostwald ripening (or the Lifshitz-Slyozov mechanism), and (3) coalescence. 

Diffraction experiments have discovered values of a that span nearly the entire range 0 < a < 1, see Fig. 2. Theories for the coarsening of self-similar morphologies predict a = l/i,i = 3,4,5 the value of i depends on assumptions about the geometry of the roughness (e.g., 1-D vs. 2-D) and mechanisms for mass-transport many of the experiments have indeed found 1/5 < a < 1/3. We note however, that in our opinion, the interpretation of these diffraction experiments is greatly complicated by the fact that the variation of the step density in the plane of the surface, the lateral characteristic... 

Capillary forces induce morphological evolution of an interface toward uniform diffusion potential—which is also a condition for constant mean curvature for isotropic free surfaces (Chapter 14). If a microstructure has many internal interfaces, such as one with fine precipitates or a fine grain size, capillary forces drive mass between or across interfaces and cause coarsening (Chapter 15). Capillary-driven processes can occur simultaneously in systems containing both free surfaces and internal interfaces, such as a porous polycrystal. 

The behavior of chemical phase-separated blends in the bulk after thermal quenching into the unstable region of the phase diagram is variable. In the bulk, the concentration fluctuations that govern the phase-separation process are random. As a result, the final morphology consists of mutually interconnected domain structures rich in a given blend component that coarsen slowly with time. 

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