Analysis of the rheology of magnetic bidisperse suspensions in the regime of discontinuous shear thickening
Résumé
The phenomenon of discontinuous shear thickening (DST) is observed in suspensions of solid particles with a very high-volume fraction. For suspensions of ferromagnetic particles this transition can also be triggered by the application of a magnetic field (Bossis et al. 2016). Here we explore the rheological behavior of a bidisperse suspension made of magnetic -carbonyl iron(CI)- and non-magnetic -calcium carbonate (CC)- particles with a brush like coating of the same superplasticizer molecule. We highlight the synergetic effect of non-magnetic particles whose inclusion in the percolated frictional network amplifies the effect of the magnetic field on the remaining fraction of magnetic particles. In plate-plate geometry, a small fraction of ferromagnetic particles (about 5%) is sufficient to trigger the transition by the application of a magnetic field and optimum for the increase of viscosity. The progressive interpenetration of the coating layers of polymer and the demagnetizing field can explain this behavior.
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