Aggregation kinetics and shear rheology of aqueous silica suspensions

Abstract

The kinetics of aggregation of silica nanoparticle solutions as a function of NaCl and silica concentrations is studied experimentally and theoretically. Silica nanoparticles form fractal aggregates due to the collapse of the electrical double layer at high salt concentrations and resulting reduction in stabilizing repulsive force. We propose a convenient model to describe the aggregation of silica nanoparticles and the growth of their aggregate size that depends on particle size and concentration and salt concentration. The model agrees well with experimental data. The aggregation of silica nanoparticles also affects the rheology of the suspension. We propose an equilibrium approach for sediment volume fraction to determine the maximum effective packing fraction. The results for the relative viscosity of silica aggregates agree well with the proposed viscosity model, which also collapses onto a single master curve.

Rheological response of a modified polyacrylamide–silica nanoparticles hybrid at high salinity and temperature

“…This is in agreement with the flocculation of small silica NPs into particulate networks, resulting in sedimentation as also reported by others. 58,59 Fig. 1d shows that for GPTMS-modified silica NPs in Brine2015, even though a few slightly larger agglomerates were formed, a majority of the NPs remained separated from each other.…”

Phase behavior and rheological characterization of silica nanoparticle gel

“…Figure 4 is a schematic presentation of sedimentation and gelation of aggregates. The structure of the aggregates within the sediment, such as the solid volume fraction, is discussed based on the equilibrium approach by Metin et al (2012a). Even though both nanoparticle dispersions display the same four phase behavior regions, the extent of each region, specifically the gelation window, is different.…”

“…Destruction of the structure or breakdown of the filler network occurs at higher strain, and the loss modulus decreases because of further breakdown of the structure (Yziquel et al 1999). Aggregate size decreases as the silica concentration increases (Metin et al 2012a). The increase in G 00 as silica concentration increases is likely a result of these smaller, more dissipative aggregates at higher silica concentrations.…”

Bio‐Inspired Hydro‐Pressure Consolidation of Silica

“…In colloidal chemistry, this condition of clustering and sedimentation is known as unstable suspension . The rate of aggregation of a suspension is dependent on the pH and zeta potential of the solution . This mechanism occurs immediately after the mixing of the powder and solution, prior to and during application of hydro‐pressure.…”