Shear Thickening in Concentrated Soft Sphere Colloidal Suspensions: A Shear Induced Phase Transition

A model of shear thickening in dense suspensions of Brownian soft sphere colloidal particles is established. It suggests that shear thickening in soft sphere suspensions can be interpreted as a shear induced phase transition. Based on a Landau model of the coagulation transition of stabilized colloidal particles, taking the coupling between order parameter fluctuations and the local strain-field into account, the model suggests the occurrence of clusters of coagulated particles (subcritical bubbles) by applying a continuous shear perturbation.The critical shear stress of shear thickening in soft sphere suspensions is derived while reversible shear thickening and irreversible shear thickening have the same origin. The comparison of the theory with an experimental investigation of electrically stabilized colloidal suspensions confirms the presented approach.Comment: 10 page

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