Structure and Property Evolution During Film Formation From Binary Colloidal Suspensions

Abstract

The structure and stress evolution of aqueous tape-cast layers prepared with varying composition of Al2O3:latex were studied by shear rheology, direct visualization, and a controlled environment stress measurement device. Their low shear viscosity was nearly independent of alumina:latex ratio for binary mixtures, whose particle size ratio (D¯ alumina:D¯latex) approached unity, but varied over an order of magnitude for systems with particle size asymmetry. Direct visualization of these mixtures revealed that particle flocculation occurred as their total soil loading increased. Pure alumina layers exhibited a maximum stress of ∼1 MPa and a residua stress below 0.01 MPa. The ceramic phase dominated the initial period of stress rise, while the latex phase strongly influenced the residual stress of layers cast from alumina:latex suspensions. Their maximum drying stress increased with decreasing Al2O 3 particle size, whereas their residual stress increased with increasing latex Tg. Our observations provide guidelines for the design of ceramic suspensions composed of deformable latex and rigid ceramic particles, such as those used for aqueous tape casting of ceramic films.