Viscoelastic properties of concentrated shear-thickening dispersions

Abstract

The viscoelastic properties of electrostatically stabilized concentrated dispersions of silica and of glass particles in a glycerol/water mixture are studied by oscillatory shear measurements. These dispersions are shear-thickening in steady shear flow. At most frequencies the loss modulus is found to dominate the storage modulus. At certain critical combinations of deformation amplitude and frequency the response signal becomes distorted, containing higher harmonics. This phenomenon can be ascribed to flow blockage, closely related to shear thickening in steady shear flow. When plotting the critical deformation against the frequency, three different regions can be detected. At low frequencies there is the steady shear flow limit, at intermediate frequencies double-layer overlap causes nonlinearity in the response signal, and at high frequencies there is a region where the critical deformation for flow blockage is a system-dependent function of the frequency, but is independent of the volume fraction. The magnitudes of the storage moduli are found to be in reasonable agreement with theoretical predictions.

Energy dissipation in concentrated monodisperse colloidal suspensions of silica particles in polyethylene glycol

“…The relative area of the distorted ellipsoids thus tends to decrease with stress level. This is in opposition with the expected behaviour [2], nonetheless this phenomenon has already been reported in literature [38], and attributed to flow blockage. Figure 5 plots E d calculated using Eq.…”

“…After the transition, the response is distorted and takes a rectangular shape near the transition and a distorted sinusoid shape far from it. This typical evolution of the response signal with an increase of the stress amplitude has been previously reported in the literature [13,27,38]. The rectangular shape reveals the non-linear response of shear thickening, as the experimental signal is composed of several harmonics [27].…”

Numerical Simulation in Steady Flow of Non-Newtonian Fluids in Pipes with Circular Cross-Section

“…Figure 4 shows the viscosity curve of a STF containing the three characteristic regions typically exhibited: slight shear thinning at low shear rates, followed by a sharp viscosity increase over a threshold shear rate value (critical shear rate), and a subsequent pronounced shear thinning region at high shear rates. Nowadays, the physics of the phenomenon is deeply understood thanks to the use of modern rheometers, scattering techniques, rheo-optical devices and Stokesian dynamic simulations (Bender & Wagner, 1996;Hoffman, 1974;Boersma et al, 1992;D'Haene et al, 1993;Hoffman, 1998;Maranzano & Wagner, 2002;Larson, 1999). However, there is a lack of experimental or theoretical models able to predict the whole effective viscosity curve of STFs, including the shear thinning behaviours normally present in these materials for low enough and high enough values of the shear rate.…”

Tuning of the rheological properties of concentrated silica suspensions using carbon nanotubes

“…According to the order-disorder transition (ODT) theory, disorder in the particle arrangements in the fluid by the application of shear rate is responsible for the shear-thickening behavior (Hoffman 1972;Hoffman 1974;Hoffman 1998;Boersma et al 1992;Laun et al 1992); while according to the hydrocluster mechanism, the shear-thickening occurs when hydrodynamic shear forces overcome repulsive steric and Brownian forces (Bender and Wagner 1995;Bender and Wagner 1996;Brady and Bossis 1988).…”