Fig. 11.

(a) SEM image (500 × magnification) showing whole cross section of a strip and ten non-overlapping sliced areas for porosity measurement (only 3 slices shown, slices not scaled); (b) Box-and-whisker plots representing pore size (d_n) against slice number. Median values, interquartile ranges (i.q.r.) and 1.5 times the i.q.r (excluding outliers ° and extreme values *) are denoted by horizontal bars, boxes and whiskers respectively. The change in pore sizes from top to bottom of the strip wasn't significant (Kruskal–Wallis, p > 0.05, pairwise comparisons); (c) plot of porosity (Φ) against slice number from the top to the bottom of a strip.