Aqueous tape casting of Al2O3 based on alginate gelation

Aqueous tape casting is receiving increasing attention because of health and environmental reasons, However, the main problem deals with the low evaporation rate of water that results in long drying times. As a consequence, the tapes adhere to the substrate and crack. The aim of this work is to avoid the differential shrinkage occurring in water by gelling the as-cast tapes. A chemical gelling binder, alginate, is used for such propose. To promote the intermolecular bonding, the wet tape is introduced in a CaCl2 bath. The role of different additives (dispersant, binder/ plasticizer, sequestrant, gelling agent and bonding former) in the suspension stability is studied through rheological measurements. The formulation of the suspension and the process sequence have been optimised to reach homogeneous tapes with sintered density values of 98% of the theoretical density.