Rheological characterization of water-based slurries for the tape casting process

Rheological properties of aqueous tape casting slurries have been investigated as they strongly affect the tape casting process and the quality of the final product. The aqueous slurries consist of yttria stabilized zirconia and a polymeric latex emulsion as the binder. The viscosity, its time dependent behavior and the strength of the internal structure of the slurry were characterized by static and dynamic measurements using a cone-plate viscosimeter. The results were compared with the properties of the pure latex emulsion binder. The ceramic slurries exhibit the desired strong pseudoplastic, but non-thixotropic behavior. Due to the high solids content the slurries show distinctive elastic properties below a critical shear stress. Above the critical shear stress the internal structure is broken up and the viscous properties become predominant. The paper demonstrates that the measurement of the viscosity, its time dependent behavior and the strength of the internal structure of the slurry are excellent tools to characterize the suitability of a ceramic slurry for the tape casting process.