Influence of slip preparation and casting conditions on aqueous tape casting of Al 2O 3

Abstract

In this work the influence of the slip preparation on manufacturing alumina tapes through an aqueous tape-casting process is studied. For this purpose deflocculated slips with 80 to 87 wt% of solids have been prepared and rheologically characterized. Ceramic tapes were produced following two different preparation routes, (1) starting from deflocculated suspensions with a fixed final solid concentration of 80 wt% after binders addition, and (2) starting from deflocculated slips with 84 wt% solid loading to produce tape casting slurries with different final solid concentration after binders addition. A mixture of two acrylic emulsions with different T g values has been used as binding system with total concentrations of 10, 15, and 20 wt% with respect to solids. It has been found that tapes produced by route 1 have a maximum green density (56% of theoretical density) when adding 15 wt% of binder system and 95% of relative final density, while tapes produced by route 2 give a similar relative green density (∼58.5% Th.) for any binder system additions. The final density of tapes obtained from route 2 have a maximum density of 97% for slips with 15 wt% of binder system. Additionally, the influence of tape casting parameters on green and final density was also studied. From this it was found that it is possible to increase the green density values from 60 to 62% and from 97 to 98% for fired density from tapes which were cast at 400 μm gap and 5 mm/s.