Nonlinear rheology of a concentrated spherical silica suspension:

摘要: Time-dependent nonlinear flow behavior was investigated for a model hard-sphere suspension, 50 wt% suspension of spherical silica particles (radius = 40 nm; effective volume fraction 0.53) in 2.27/1 (wt/wt) ethylene glycol/glycerol mixture. The had two stress components, the Brownian σ B and hydrodynamic H After start-up at various shear rates $$\dot \gamma $$ , viscosity growth function η+ (t, ) measured with time t until it reached steady state. decay η− after cessation from as well transient states. At low where state η ( exhibited shear-thinning, data were quantitatively described BKZ constitutive equation utilizing relaxation moduli G γ). This result enabled us to attribute thinning decrease contribution η / (considered through damping γ)). On other hand, high thickening, prediction largely deviated data, latter obtained flow. suggested that thickening due an enhancement (not considered equation). However, when stopped only small strain (<0.2) applied, hardly enhanced agreed prediction. Correspondingly, onset characterized -insensitive (≌ 0.2). basis these results, (thickening mechanism) related dynamic clustering took place applied fast larger than characteristic necessary close approach/collision particles.