Effect of dispersants on rheological behavior of BaTiO3 powders in ethanol–isopropanol mixtures

The rheological behavior of barium titanate (BaTiO3) powders dispersed in ethanol–isopropanol mixtures of 1:1 ratio was investigated in terms of dispersant type, dispersant concentration (0.1–5 wt.% of the powder) and volumetric solid loading (φ=0.3–0.6) over a shear rate range 1–1000 s−1. Six commercially available dispersants were used in the study; among which, a non-ionic polymeric surfactant (KD-6) provided the best dispersion effectiveness. The suspension viscosity decreased pronouncedly as the surfactant concentration was increased, and the viscosity reached a minimum as the surfactant concentration exceeded 3 wt.% of the solid to a viscosity level only 4% of the suspensions containing no dispersant. Dependence of the suspension viscosity to the solid fraction was compared with existing models. The model equation proposed by Krieger and Dougherty appeared reasonable in predicting the viscosity over a broad solid concentration range (φ=0.3–0.55).