Preparation of extrudable alumina paste by coagulation of electrosterically stabilized aqueous slurries

The present work demonstrates the conversion of a low viscous concentrated (55 vol.%) alumina slurry into a thick extrudable paste by in situ coagulat ion. Highly concentrated (55 vol.%) electrosterically stabilized aqueous al umina slurry prepared using polyacrylate dispersant was coagulated by in si tu generation of acetic acid. Acetic anhydride was used for acid generation and the miscibility of acetic anhydride in aqueous medium was increased by polyethylene glycol. Addition of acetic anhydride >0.16 mol/l converts the slurry in to a stiff paste, within 5 min. The paste exhibits extrudable co nsistency. Incorporation of 1% PVA in the slurry provides additional streng th to the extruded tubes against deformation and development of drying crac ks. The tubes sintered to 97% TD and the sintered samples showed a fine gra ined microstructure. (C) 2001 Elsevier Science Ltd. All rights reserved.