Rheology of Polydisperse non-Spherical Graphite Particles Suspended in Mineral Oil

TL;DR

This study investigates how filler concentration and microphysics influence the rheological behavior of polydisperse non-spherical graphite particles in mineral oil, revealing shear thinning, yielding, and temperature-dependent adhesion effects.

Contribution

It introduces a constraint-based rheological model accounting for frictional and adhesive contacts, highlighting concentration and temperature effects on flow behavior.

Findings

Shear thinning and yielding occur at volume fractions above 0.18.

Flow activation energy depends on graphite concentration.

Adhesive stress varies with temperature, affecting flow dynamics.

Abstract

We study the role of filler concentration and microphysics on the rheology of polydisperse flake-graphite particles suspended in Newtonian mineral oil. Under steady shear, our samples exhibit shear thinning and yielding behaviour is observed for volume fractions $\phi > 0.18$. Time-temperature superposition was observed using an Arrhenius-type horizontal shift factor, giving a flow activation energy that is dependent on the graphite volume fraction, suggesting concentration-dependent contributions to relaxation processes in the suspensions. The flow curves are fitted by a constraint-based model, indicating that the flow behaviour is controlled by frictional and adhesive contacts, with the model suggesting that the adhesive stress is temperature dependent.