Microstructure and rheological behavior of capillary suspension prepared with plate-shaped particles

Abstract

Capillary suspension is a unique strategy to prepare high-yield-stress fluids, in which particle-to-particle interaction caused by capillary bridges results in a substantial change in fluidity. The capillary suspension with plate-shaped particles have recently been considered useful in various applications, including Li-battery electrodes and conductive elastomers, due to their large specific surface area, which results in a rigid sample-spanning capillary network. However, there is a poor understanding of the relationship between the dimensions of plate-shaped particles and the fluidity of the capillary suspensions.In this study, the yield stress of the capillary suspension prepared with plate-shaped particles of various diameters and thicknesses was investigated to establish a correlation equation. Additionally, the conformation of the particles in the capillary suspension was also determined by microscopic analysis. As a result, it was discovered that when the secondary fluid is added, plate-shaped particles form a laminated structure supported by capillary bridges generated between their largest faces (pendular state). Furthermore, rheological measurements revealed that the yield stress of the capillary suspension was determined by the number density of particles, cross-sectional area of the particle, and volume fraction of the secondary fluid. Based on these findings, we established a power-law-based correlation equation that accurately predicted (20% error at most) the yield stress of the capillary suspension regardless of the size of the particles.