Influence of slip preparation and casting conditions on aqueous tape casting of Al2O3

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 the ologically characterized. Ceramic tapes were produced following two differe nt preparation routes, (1) starting from deflocculated suspensions with a f ixed final solid concentration of 80 wt% after binders addition, and (2) st arting from deflocculated slips with 84 wt% solid loading to produce tape c asting slurries with different final solid concentration after binders addi tion. A mixture of two acrylic emulsions with different Tg 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 I have a maximum green density (56% of theoretical density) when adding 15 wt% of b inder system and 95% of relative final density, while tapes produced by rou te 2 give a similar relative green density (similar to 58.5% Th.) for any b inder system additions. The final density of tapes obtained from route 2 ha ve a maximum density of 97% for slips with 15 wt% of binder system. Additio nally, 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 th e green density values from 60 to 62% and from 97 to 98% for fired density from tapes which were cast at 400 mum gap and 5 mm/s. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.