Structural transitions and the rheology of soft sphere suspensions

+184hlm.;24c

Shear thickening in suspensions as modeled on different length scales

A theory is presented for the rheology of dense, electrically stabilized, colloidal suspensions under shear. It is based on a combination of an activation model (microsocopic scale) and a Landau theory (mesoscopic scale). Shear thickening is described here as a structural transition induced by an electroviscous effect in concentrated suspensions. A set of phenomenological equations are established that describe the shear-rate dependent viscosity. The results will be compared to experimental investigations on monodisperse and polydisperse suspensions of different volume fractions. A good agreement between theory and experimental results can be obtained

Shear thickening in suspensions as modeled on different length scales

A theory is presented for the rheology of dense, electrically stabilized, colloidal suspensions under shear. It is based on a combination of an activation model (microsocopic scale) and a Landau theory (mesoscopic scale). Shear thickening is described here as a structural transition induced by an electroviscous effect in concentrated suspensions. A set of phenomenological equations are established that describe the shear-rate dependent viscosity. The results will be compared to experimental investigations on monodisperse and polydisperse suspensions of different volume fractions. A good agreement between theory and experimental results can be obtained

Shear thickening in electrically stabilized non-aqueous colloidal suspensions

A theory is presented for the onset of shear thickening in colloidal suspensions of particles, stabilized by an electrostatic repulsion. Based on an activation model, a critical shear stress can be derived for the onset of shear thickening in dense suspensions for a constant potential and a constant charge approach of the spheres. Unlike previous models, the total interaction potential is taken into account (sum of attraction and repulsion). The critical shear stress is related to the maximum of the total interaction potential scaled by the free volume per particle. A comparison with experimental investigations shows the applicability of the theory

Shear thickening in electrically-stabilized colloidal suspensions

A theory is presented for the onset of shearthickening in colloidal suspensions of particles, stabilizedby an electrostatic repulsion. Based on an activation model,a critical shear stress can be derived for the onset of shearthickening in dense suspensions for a constant potential anda constant charge approach of the spheres. Unlike previousmodels, the total interaction potential is taken into account(sum of attraction and repulsion). The critical shear stress isrelated to the maximum of the total interaction potentialscaled by the free volume per particle. A comparison withexperimental investigations shows the applicability of thetheory

The impact of non-DLVO forces on the onset of shear thickening of concentrated electrically stabilized suspensions

This paper exposes an extension of an activation model previously published by the authors. When particles arranged along the compression axis of a sheared suspension, they may overcome the electrostatic repulsion and form force chains associated with shear thickening. A percolation-based consideration allows an estimation of the impact of the force chains on a flowing suspension. It suggests that similar to mode coupling models, the suspension becomes unstable before the critical stress evaluated from the activation model is reached. The percolated force chains lead to discontinuous shear thickening. The model predictions are compared with results from two experimental studies on aqueous suspensions of inorganic oxides; in one of them, hydration repulsion and in the other hydrophobic attraction can be expected. It is shown that the incorporation of non-Derjaguin-Landau-Verwey-Overbeek forces greatly improve predictions of the shear thickening instability. © Springer-Verlag 2009

Shear thickening as a consequence of an acoustic resonance in sheared colloidal crystals

A model is presented that predicts the critical shear rate of shear thickening of soft sphere colloidal suspensions. It is based on the idea that shear in a colloidal crystal leads to a periodic variation of the elastic modulus with time. At a specific shear rate an acoustic resonance occurs which leads to an increase of the viscosity. Good agreement with experimental results could be obtained by fitting the single parameter of the model

Shear thickening in suspensions as modeled on different length scales

A theory is presented for the rheology of dense, electrically stabilized, colloidal suspensions under shear. It is based on a combination of an activation model (microsocopic scale) and a Landau theory (mesoscopic scale). Shear thickening is described here as a structural transition induced by an electroviscous effect in concentrated suspensions. A set of phenomenological equations are established that describe the shear-rate dependent viscosity. The results will be compared to experimental investigations on monodisperse and polydisperse suspensions of different volume fractions. A good agreement between theory and experimental results can be obtained