Rheology of polydisperse nonspherical graphite particles suspended in mineral oil

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 behavior is observed for volume fractions ϕ > 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 behavior is controlled by frictional and adhesive contacts, with the model suggesting that the adhesive stress is temperature dependent.