Effects of Shear-Induced Crystallization on the Rheology and Ageing of Hard Sphere Glasses

TL;DR

This study investigates how shear-induced crystallization affects the rheological behavior and aging of hard sphere glasses, revealing structural and mechanical changes due to shear and long-range order.

Contribution

It provides new insights into the rheological response of shear-induced crystals compared to glasses, highlighting structural effects on mechanical properties.

Findings

Shear-induced crystallization reduces elastic and viscous moduli.

Crystals exhibit smaller critical and crossover strains than glasses.

Crystals show similar aging behavior to glasses despite structural differences.

Abstract

The rheological properties of highly concentrated suspensions of hard-sphere particles are studied with particular reference to the rheological response of shear induced crystals. Using practically monodisperse hard spheres, we prepare shear induced crystals under oscillatory shear and examine their linear and non-linear mechanical response in comparison with their glassy counterparts at the same volume fraction. It is evident, that shear-induced crystallization causes a significant drop in the elastic and viscous moduli due to structural rearrangements that ease flow. For the same reason the critical (peak of G'') and crossover (overlap of G' and G'') strain are smaller in the crystal compared to the glass at the same volume fraction. When, however the distance from the maximum packing in each state is taken into account the elastic modulus of the crystal is found to be larger than the glass at the same free volume suggesting a strengthened material due to long range order. Finally, shear induced crystals counter-intuitively exhibit similar rheological ageing to the glass (with a logarithmic increase of G'), indicating that the shear induced structure is not at thermodynamic equilibrium.