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a) b - École Polytechnique de Montréal

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droplets. The results indicate that due to forces and coalescence, each phase joins with same<br />

phase, and thus phase sizes become larger. In other words, a complete transition from multiple<br />

subinclusion particles within a given shell to a core-shell structure is observed. It can be said that<br />

this process is performed similarly to the case of binary blends, as thin parts of each component<br />

are being pushed to thick parts of the same component due to capillary forces, which results in an<br />

increase in average pore size.<br />

Figure 2-15. Experimental pore size growth (points) with the theoretical mo<strong>de</strong>l (solid lines) for<br />

different blends annealed at 200°C. (Yuan, 2005)<br />

2.2 Percolation Theory<br />

The behavior of the connected clusters in a random graph in mathematics is <strong>de</strong>scribed by the<br />

percolation theory. The main concept of the percolation theory is the existence of a percolation<br />

threshold. Percolation threshold is a mathematical term <strong>de</strong>fined as the formation of long-range<br />

connectivity in random systems. Percolation threshold in engineering and material science <strong>de</strong>als<br />

with fluid flow and similar processes which concern the movement and filtering of fluids through<br />

porous media. One question that arises is whether a liquid poured on top of a porous material is<br />

able to make its way from the top to the bottom. From a mathematical point of view, a regular<br />

40

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