Production of calcium hexaluminate porous planar membranes with high morphological stability and low thermal conductivity.

High-quality Al 2 O 3 porous ceramic planar membranes suffer from severe deformation and cracking, which occur during sintering process. This study reports on solving this problem, by introducing calcium hydroxide powder in the alumina slurry. Phase-inversion tape-casting technology, applied during molding, and sintering at 1550 °C, favored an in-situ expansion reaction, which effectively suppressed deformation, and well-formed and crack-free calcium hexaluminate porous planar membranes were obtained. The produced membranes had a low thermal conductivity (0.69 W·m−1 K−1 at 85 °C), ascribed to the in-situ formed plate-like structure of calcium hexaluminate (CA 6) and to the high porosity. After hydrophobic modification, the membranes were applied in membrane distillation processing. High rejection rate (>99.9%) and water flux (19.8 L·m-2 h−1) were achieved at 85 °C, using a 4 wt% NaCl solution as a feed solution. [ABSTRACT FROM AUTHOR]