Water transfer and crack regimes in nano-colloidal gels

TL;DR

This study investigates water transfer and crack formation in nano-colloidal gels during drying, revealing that air penetration occurs after shrinkage stops and influences fracture behavior through capillary effects.

Contribution

It provides new insights into nano-scale liquid dynamics and fracture mechanisms in colloidal gels during drying, based on direct observations and water distribution measurements.

Findings

Air begins to penetrate the gel after shrinkage stops.

Water saturation remains homogeneous despite air invasion.

Capillary effects induce fractures during drying.

Abstract

Direct observations of the surface and shape of model nano-colloidal gels associated with measurements of the spatial distribution of water content during drying show that air starts to significantly penetrate the sample when the material stops shrinking. We show that whether the material fractures or not during desiccation, as air penetrates the porous body, the water saturation decreases but remains almost homogeneous throughout the sample. This air-invasion is at the origin of another type of fracture due to capillary effects, these results provide a new insight in the liquid dynamics at the nano-scale. PACS number(s): 47.56.+r, 68.03.Fg, 81.40.Np