Interplay of particle shape and suspension properties: a study of cube-like particles

Audus, Debra J.; Hassan, Ahmed M.; Garboczi, Edward J.; Douglas, Jack F.

doi:10.1039/c4sm02869d

Cited by 37 publications

(27 citation statements)

References 61 publications

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“…Most of the uncertainty in d H is due to uncertainty in the viscosity of the glycerol/water supernatant µ. Our measured d H is just slightly larger than the edge length (d H /2a = 1.06 ± 0.08) and consistent with recent numerical work by Audus et al 32 which predicts d H /2a ≈ 1.10 for m = 2.85.…”

Section: Rheology and Diffusion In Dilute Suspensionssupporting

confidence: 89%

Rheology and dynamics of colloidal superballs

et al. 2015

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Recent advances in colloidal synthesis make it possible to generate a wide array of precisely controlled, non-spherical particles. This provides a unique opportunity to probe the role that particle shape plays in the dynamics of colloidal suspensions, particularly at higher volume fractions, where particle interactions are important. We examine the role of particle shape by characterizing both the bulk rheology and micro-scale diffusion in a suspension of pseudo-cubic silica superballs. Working with these well-characterized shaped colloids, we can disentangle shape effects in the hydrodynamics of isolated particles from shape-mediated particle interactions. We find that the hydrodynamic properties of isolated superballs are marginally different from comparably sized hard spheres. However, shape-mediated interactions modify the suspension microstructure, leading to significant differences in the self-diffusion of the superballs. While this excluded volume interaction can be captured with a rescaling of the superball volume fraction, we observe qualitative differences in the shear thickening behavior of moderately concentrated superball suspensions that defy simple rescaling onto hard sphere results. This study helps to define the unknowns associated with the effects of shape on the rheology and dynamics of colloidal solutions.

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Section: Rheology and Diffusion In Dilute Suspensionssupporting

confidence: 89%

Rheology and dynamics of colloidal superballs

et al. 2015

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“…These particles were also used in Koos et al [29] along with spheres and spheroids. Unlike the particle shape dependence found in low Re regime rheological measurements [30,31], the measurements from Koos et al [29] did not show a difference with particle geometry.…”

Section: Experimental Rheometer and Pure Fluid Studiesmentioning

confidence: 54%

Effects of inertia and turbulence on rheological measurements of neutrally buoyant suspensions

2016

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For low-Reynolds number shear-flows of neutrally-buoyant suspensions, the shear stress is often modeled using an effective viscosity that depends only on the solid fraction. As the Reynolds number (Re) is increased and inertia becomes important, the effective viscosity also depends on the Reynolds number itself. The current experiments measure the torque for flows of neutrallybuoyant particles in a coaxial-cylinder rheometer for solid fractions, φ, from 10% to 50% and Reynolds numbers based on particle diameter from 2 to 1,000. For experiments for Reynolds of O(10) and solid fractions less than 30%, the effective viscosity increases with Reynolds number, in good agreement with recent numerical simulations found in the literature. At higher solid fractions over the same range of Re, the results show a decrease in torque with shear rate. For Reynolds numbers greater than 100 and lower solids concentrations, the effective viscosity continues to increase with Reynolds number. However, based on comparisons with pure fluid measurements the increase in the measured effective viscosity results from the transition to turbulence. The particles augment the turbulence by increasing the magnitude of the measured torques and causing the flow to transition at lower Reynolds numbers. For the highest solid fractions, the measurements show a significant increase in the magnitude of the torques, but the effective viscosity is independent of Reynolds number.

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“…The authors confirmed this result experimentally using dispersions of Fe 3 O 4 nanocubes (k E = 3.1 AE 0.2) and the Einstein coefficient was shown to be independent of the particle size and size distribution. Audus et al 43 employed three different computational methods and obtained very similar results. Vickers and co-workers 44 measured the steady shear rheology of a limited number of concentrated suspensions consisting of near monodisperse Co 3 O 4 nanocubes.…”

Section: Introductionmentioning

confidence: 84%

Rheology of cubic particles suspended in a Newtonian fluid

2016

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Many real-world industrial processes involve non-spherical particles suspended in a fluid medium. Knowledge of the flow behavior of these suspensions is essential for optimizing their transport properties and designing processing equipment. In the present work, we explore and report on the rheology of concentrated suspensions of cubic-shaped colloidal particles under steady and dynamic shear flow. These suspensions exhibit a rich non-Newtonian rheology that includes shear thickening and normal stress differences at high shear stresses. Scalings are proposed to connect the material properties of these suspensions of cubic particle to those measured for suspensions of spherical particles. Negative first normal stress differences indicate that lubrication hydrodynamic forces dominate the stress in the shear-thickened state. Accounting for the increased lubrication hydrodynamic interactions between the flat surfaces of the cubic particles allows for a quantitative comparison of the deviatoric stress in the shear-thickened state to that of spherical particles. New semi-empirical models for the viscosity and normal stress difference coefficients are presented for the shear-thickened state. The results of this study indicate that cubic particles offer new and unique opportunities to formulate colloidal dispersions for field-responsive materials.

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Interplay of particle shape and suspension properties: a study of cube-like particles

Cited by 37 publications

References 61 publications

Rheology and dynamics of colloidal superballs

Rheology and dynamics of colloidal superballs

Effects of inertia and turbulence on rheological measurements of neutrally buoyant suspensions

Rheology of cubic particles suspended in a Newtonian fluid

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