Porosity and pore size control in starch consolidation casting of oxide ceramics—Achievements and problems

The possibilities and limits of porosity and pore size control via starch consolidation casting (SCC) are discussed from a principal point of view. The results for alumina ceramics indicate that porosity control between 25 and 50% is feasible, while lower and higher porosities are difficult to achieve by SCC. The main factor of pore size control is the selected starch type, although swelling should be taken into account for a more precise size control. Of the starch types investigated here, potato starch is the largest (resulting in pore sizes of 50 μm and higher) and corn starch is the smallest (14 μm), while wheat starch is intermediate (20 μm). A quantitative comparison of pore size results, however, is complicated by Wicksell's problem and (in the case of potato and wheat starch) the anisometric shape (median aspect ratios of 1.3 and 2.0 for prolate and oblate shape, respectively).