Influence of particle size and aggregation state of alumina on the rheology of a ceramic paste with an organic binder of ethylene-vinyl acetate copolymer and stearic acid

The flow behavior of ceramic pastes with various alumina powder contents and different particle sizes, L-particles (D-ave. = 6.7 mu m) and S-particles (D-ave. = 0.13 mu m), in an organic binder of ethylene-vinyl acetate copolymer and stearic acid was investigated by dynamic viscoelasticity measurements. The rheological properties of ceramic pastes with high powder content over 19 vol% could not be investigated by the rotational method due to the high viscosity, and were analyzed by the oscillation method. Relative dynamic complex viscosities increased with the powder content, and were consistent with the Dougherty-Krieger model for evaluation of the apparent hydrodynamic shape factor (K-H) and the maximum powder content (f(cr)(v)). The f(cr)(v) and K-H of the L-paste were 0.62 and 1.6, and those of the S-paste were 0.59 and 8.2, respectively. It is considered that the L-particles were comparatively well dispersed and S-particles were aggregated in the paste. These analyses agreed with the aggregates of S-particles determined by SEM observations. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.