Impact of granular inclusions on the phase behavior of colloidal gels

TL;DR

This study uses simulations to explore how larger granular inclusions influence the phase behavior and microstructure of colloidal gels, revealing two regimes based on filler size and gel structure.

Contribution

It introduces a detailed analysis of how granular particles affect gel phase boundaries, distinguishing passive and active regimes based on filler size.

Findings

Passive regime shows minimal change in phase transition.

Active regime alters phase boundary via available free volume.

Phase behavior depends on filler size and gel microstructure.

Abstract

Colloidal gels formed from small attractive particles are commonly used in formulations to keep larger components in suspension. However, despite extensive work characterizing unfilled gels, little is known about how larger inclusions alter the phase behavior and microstructure of the colloidal system. Here we use numerical simulations to examine how larger `granular' particles can alter the gel transition phase boundaries. We find two distinct regimes depending on both the filler size and native gel structure: a `passive' regime where the filler fits into already-present voids, giving little change in the transition, and an `active' regime where the filler no longer fits in these voids and instead perturbs the native structure. In this second regime the phase boundary is controlled by an effective colloidal volume fraction given by the available free volume.