Rational design in suspension rheology of cellular silica

Abstract

Slurry based processing route involving the use of partially hydrophobized fused silica particles, binders, long chain surfactants and drying control additives have been optimized for the fabrication of cellular silica. The major accomplishments of this study are the optimization of the fused silica powder based suspension composition, foaming duration and foam stabilization to prepare cellular silica-based components. Rheological studies have been carried out on the suspensions to examine the effect of solids loading, and volume fractions of individual additives on the viscosity, with the objective of optimizing the slurry composition and viscosity for maximum air entrainment and foam stability. The rheological studies on silica-based suspensions have exhibited that the final properties of the foams depend on the slurry composition. The suspensions prepared in the study have been found to be non-Newtonian, and have shown shear thinning behavior at higher shear rates. The role of viscosity and surface tension has shown a significant effect on the flow behavior, foaming characteristics and stability of the air bubbles in a suspension, which in turn affects the overall pore volume fraction and porous architecture of the finished foams.