Freeze gelcasting of hydrogenated vegetable oil-in-aqueous alumina slurry emulsions for the preparation of macroporous ceramics

Freeze gelcasting of hydrogenated vegetable oil-in-aqueous alumina slurry (HVO-in-AAS) emulsions has been studied for the preparation of macroporous ceramics. The emulsions with HVO to AAS volume ratios in the range of 1.34–2.69 prepared from a 30 vol.% AAS containing carrageenan using sodium dodecyl sulphate emulsifying agent at 85 °C undergo gelation on cooling to room temperature due to the solidification of HVO and physical cross-linking of carrageenan. Macroporous ceramics obtained by drying, HVO removal followed by sintering at 1500 °C of the gelled emulsion bodies had porosity in the range of 70.7–84% and contain cells of spherical to polygonal shape. The average cell size (13.24–3.6 μm) decreased and the cell interconnectivity increased with an increase in HVO to AAS volume ratio and mixing speed. The macroporous alumina bodies had high compressive strength (6.5–39.6 MPa) and Young's modulus (350–2352 MPa).