Rheology and structure of ceramic suspensions under constraints : a computational study

Abstract : The main objective of this thesis is to predict and understand the structural and rheological properties of colloidal suspensions when (1) hydrodynamic interactions (HIs) and/or (2) external forces are present. We employ two of the fastest techniques in literature: Brownian dynamics (BD), for systems without HIs; and the hybrid "stochastic rotation dynamics - molecular dynamics" (SRD-MD) for systems with HIs. Three different systems were studied. The first is a system of hard spheres subjected to shear, where the goal was to ensure that SRD-MD can correctly reproduce the viscosity vs. volume fraction relationship. The results are consistent with known analytical, numerical and experimental data. The second system is an alumina suspension described by the DLVO theory (Derjaguin-Landau-Verwey-Overbeek). The simulations show that the percolation threshold (phi_c) decreases as the depth of the potential well increases. Moreover, we note that HIs tend to form more elongated structures compared to the systems without HIs. The phi_c values ​​obtained are in good agreement with those estimated by Flatt and Bowen's yield stress model (YODEL). The third system consists of binary colloids that interact by Yukawa potential and subjected to the influence of an attractive wall. We show that the presence of an attractive wall may alter the crystalline structures such that CsCl crystals are formed instead of the metastable NaCl crystals. Finally, we conducted a preliminary study of suspensions under an oscillating shear. We show that when the aggregation process suspension coincides with the oscillatory motion, more compact structures are formed.
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Aleena Maria Laganapan. Rheology and structure of ceramic suspensions under constraints : a computational study. Materials. Université de Limoges, 2015. English. ⟨NNT : 2015LIMO0082⟩. ⟨tel-01263223⟩



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