Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles

Abade, G.C.; Wajnryb, E.; Ekiel-Jezewska, M.L.; Nägele, G.; Cichocki, B.

doi:10.1063/1.3689322

Journal Article

Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles

Abade, G. C. ; Cichocki, B. ; Ekiel-Jezewska, M. L. ; Nägele, G.FZJ* ; Wajnryb, E.

2012
American Institute of Physics Melville, NY

The journal of chemical physics 136, 104902 (2012) [10.1063/1.3689322]

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Please use a persistent id in citations: http://hdl.handle.net/2128/7494 doi:10.1063/1.3689322

Abstract: Short-time dynamic properties of concentrated suspensions of colloidal core-shell particles are studied using a precise force multipole method which accounts for many-particle hydrodynamic interactions. A core-shell particle is composed of a rigid, spherical dry core of radius a surrounded by a uniformly permeable shell of outer radius b and hydrodynamic penetration depth κ(-1). The solvent flow inside the permeable shell is described by the Brinkman-Debye-Bueche equation, and outside the particles by the Stokes equation. The particles are assumed to interact non-hydrodynamically by a hard-sphere no-overlap potential of radius b. Numerical results are presented for the high-frequency shear viscosity, η(∞), sedimentation coefficient, K, and the short-time translational and rotational self-diffusion coefficients, D(t) and D(r). The simulation results cover the full three-parametric fluid-phase space of the composite particle model, with the volume fraction extending up to 0.45, and the whole range of values for κb, and a/b. Many-particle hydrodynamic interaction effects on the transport properties are explored, and the hydrodynamic influence of the core in concentrated systems is discussed. Our simulation results show that for thin or hardly permeable shells, the core-shell systems can be approximated neither by no-shell nor by no-core models. However, one of our findings is that for κ(b - a) ≳ 5, the core is practically not sensed any more by the weakly penetrating fluid. This result is explained using an asymptotic analysis of the scattering coefficients entering into the multipole method of solving the Stokes equations. We show that in most cases, the influence of the core grows only weakly with increasing concentration.

Keyword(s): Colloids: chemistry (MeSH) ; Computer Simulation (MeSH) ; Diffusion (MeSH) ; Hydrodynamics (MeSH) ; Models, Chemical (MeSH) ; Particle Size (MeSH) ; Rheology (MeSH) ; Solvents: chemistry (MeSH) ; Surface Properties (MeSH) ; Colloids ; Solvents ; J

Classification:

Physics, Atomic, Molecular & Chemical

Note: The work of G.C.A. was supported by CAPES Foundation/Ministry of Education of Brazil. M.L.E.J. and E.W. were supported in part by the Polish Ministry of Science and Higher Education Grant No. N501 156538. G.N. thanks M. Heinen for helpful discussions and the Deutsche Forschungsgemeinschaft (SFB-TR6, project B2) for financial support. Numerical simulations were done at NACAD-COPPE/UFRJ in Rio de Janeiro, Brazil, and at the Academic Computer Center in Gdansk, Poland.

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