Rheological behavior and drying characteristics of ceria-based suspensions under various pH conditions

Abstract

Microstructural changes in ceria-based suspensions at different pH values and corresponding rheological and drying properties were correlated. Ceria-based suspensions were classified into four zones based on their pH values. Well-dispersed or aggregated states of ceria particles in suspensions were mainly discerned by the magnitude of zeta-potential with pH variations and additional condensation reaction at relatively high pH. Suspensions with well-dispersed particles in a particular pH range exhibited transition between shear-thinning and Newtonian behavior along the shear rate and weak thixotropic features, whereas suspensions with agglomerated particles in different pH ranges showed significant shear-thinning and thixotropic behaviors with shear rate. The motion of particles within suspension droplets in each zone was quantified in terms of autocorrelation functions during drying using multi-speckle diffusing wave spectroscopy. Suspension droplets with well-dispersed particles showed conspicuous coffee-ring patterns compared to those with aggregated particles, owing to the rapid Brownian motion of well-dispersed particles. • The dispersion state of ceria particles depends on the pH condition. • A densely packed structure at high pH originates from the condensation reaction • Rheological properties and drying characteristics are correlated with the microstructures.