Viscoelastic cluster densification in sheared colloidal gels

Massaro, Roberta; Colombo, Gabriele; Puyvelde, Peter Van; Vermant, Jan

doi:10.1039/c9sm02368b

Cited by 18 publications

(11 citation statements)

References 72 publications

(82 reference statements)

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“…Visualisation of dense particle suspension microstructure is challenging and thus optical imaging and actual quantification of the shear-induced characteristics of such systems has been fairly limited; to date very few relevant studies exist mainly focusing on smooth or spherical particles and biological samples, such as blood (Gunes et al, 2008;Kaliviotis et al, 2016;Lin et al, 2018;Ma et al, 2008;Massaro et al, 2020;Tanner, 2015;Varga et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

On the shear thinning of non-Brownian suspensions: Friction or adhesion?

Papadopoulou

Gillissen

Wilson

et al. 2020

Journal of Non-Newtonian Fluid Mechanics

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Shear thinning is fundamental to a broad range of particle suspensions, both in nature and in industrial applications. Yet the mechanisms governing it remain unclear. In particular, the distinct, and often competing, roles of the interparticle, particle-fluid interactions and the particle surface morphology need clarity. By using non-Brownian silica particles with different morphology, surface functional groups and suspending media, here we reveal two different shear thinning mechanisms, controlled either by frictional or adhesion forces between particles. Smooth glass sphere suspensions in a polar medium (glycerol), where particles interact strongly with the solvent, showed no shear thinning even at high volume fractions (φ≥0.5), while rough silica particles, with similar size distribution, induced shear thinning behaviour at φ values of 0.25 and above. The latter is attributed to the increased frictional contacts in rough and irregular particles. Considering surface irregularity as elastically deformable asperities enabled us to estimate the critical load above which two neighbouring rough particles experience frictional contacts giving rise to shear thinning. In contrast, in a non-polar (mineral oil) solvent, with which the particles do not interact strongly, both glass spheres and the rough silicas showed a pronounced shear thinning response and yield stress behaviour at volume fractions as low as 2% v/v. The rheology of these suspensions is dictated by the adhesion forces between the particles that lead to the formation of large agglomerates, which breakdown under increasing shear. The evolution of the sheared suspensions microstructure was captured using an optical shearing cell, which also enabled us to quantify the particle agglomeration characteristics using an aggregation index. To demonstrate the generality of our approach, we modified the surface chemistry of the glass spheres by introducing hydrophobic groups (e.g. a fluorosilane or palmitic acid) to inhibit inter-particle interactions and improve the dispersion of the otherwise inherently hydrophilic glass spheres in mineral oil; as expected, this suppressed the shear thinning behaviour of the suspensions. The present results clearly elucidate alternative design routes to controlling suspension rheology, whether to promote or suppress shear thinning, offering new insights for the manufacturing and manipulation of complex particle suspensions.

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Section: Introductionmentioning

confidence: 99%

On the shear thinning of non-Brownian suspensions: Friction or adhesion?

Papadopoulou

Gillissen

Wilson

et al. 2020

Journal of Non-Newtonian Fluid Mechanics

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“…18 Such models often require structural data that describe the gel network over a broad range of length scales, and microscopy and numerical simulations both offer powerful tools for probing the formation kinetics and structural properties of particle gels on this broad range of length scales. [19][20][21][22][23][24][25][26] These methods are often combined with computational analyses that allow for the extraction of structural parameters, 27,28 such as pair correlation functions, structure factors, and coordination numbers, that are particularly useful for describing the local network structure. [29][30][31][32] Applying these analyses to experimental and computational datasets, 14,33,34 valuable insight regarding the local structure of such particle networks can be gained.…”

Section: Introductionmentioning

confidence: 99%

ArGSLab: a tool for analyzing experimental or simulated particle networks

et al. 2021

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“…Fig.4(a). Up to γ ≈ 100, the small-particle gel coarsens and separates into irregular flocs, reminiscent of sheared pure gels[17,20]. Between γ ≈ 100 and 1000, the flocs gradually compact into disjoint blobs with a characteristic size d b ≈ 20 µm.…”

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confidence: 99%

Flow-Switched Bistability in a Colloidal Gel with Non-Brownian Grains

et al. 2022

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We show that mixing a colloidal gel with larger, non-Brownian grains generates novel flow-switched bistability. Using a combination of confocal microscopy and rheology, we find that prolonged moderate shear results in liquefaction by collapsing the gel into disjoint globules, whereas fast shear gives rise to a yield-stress gel with granular inclusions upon flow cessation. We map out the state diagram of this new 'mechanorheological material' with varying granular content and demonstrate that its behavior is also found in separate mixture using different particles and solvents.

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Viscoelastic cluster densification in sheared colloidal gels

Abstract: The effect of medium viscoelasticity on the microstructure and rheology of flocculated suspensions was studied by rheological and rheo-confocal methods. Cluster densification under flow mainly affects high shear viscosities and material strength.

Cited by 18 publications

References 72 publications

On the shear thinning of non-Brownian suspensions: Friction or adhesion?

On the shear thinning of non-Brownian suspensions: Friction or adhesion?

ArGSLab: a tool for analyzing experimental or simulated particle networks

Flow-Switched Bistability in a Colloidal Gel with Non-Brownian Grains

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