Structural anisotropy of directionally dried colloids

TL;DR

This paper investigates how directional drying induces anisotropy in colloidal silica dispersions, affecting their mechanical and optical properties through stored elastic strain during solidification.

Contribution

It reveals the mechanism of anisotropy formation via uniaxial strain during evaporation and its impact on the properties of dried colloidal films.

Findings

Anisotropy arises from uniaxial strain during drying.

Stored elastic strain influences shear band formation.

Birefringence is generated in the dried colloids.

Abstract

Aqueous colloidal dispersions of silica particles become anisotropic when they are dried through evaporation. This anisotropy is generated by a uniaxial strain of the liquid dispersions as they are compressed by the flow of water toward a solidification front. Part of the strain produced by the compression is relaxed, and part of it is stored and transferred to the solid. This stored elastic strain has consequences for the properties of the solid, where it may facilitate the growth of shear bands, and generate birefringence.