We have investigated the stationary sedimentation profiles of colloidal gels obtained by an arrested phase-separation process driven by depletion forces, which have been compressed either by natural gravity or by a centrifugal acceleration ranging between 6g and 2300g. Our measurements show that the gel rheological properties display a drastic change when the gel particle volume fraction exceeds a value øc, which barely depends on the strength of the interparticle attractive forces that consolidate the network. In particular, the gel compressive yield stress , which increases as for , displays a diverging behaviour for , with an asymptotic value that is close to the random close packing value for hard spheres. The evidence we obtained suggests that basically coincides with the liquid (colloid-rich) branch of the metastable coexistence curve, rather than with the lower (and φ-dependent) values expected for an attractive glass line penetrating inside the coexistence region.

Compressive yield stress of depletion gels from stationary centrifugation profiles

Lattuada, Enrico;Buzzaccaro, Stefano;Piazza, Roberto
2018

Abstract

We have investigated the stationary sedimentation profiles of colloidal gels obtained by an arrested phase-separation process driven by depletion forces, which have been compressed either by natural gravity or by a centrifugal acceleration ranging between 6g and 2300g. Our measurements show that the gel rheological properties display a drastic change when the gel particle volume fraction exceeds a value øc, which barely depends on the strength of the interparticle attractive forces that consolidate the network. In particular, the gel compressive yield stress , which increases as for , displays a diverging behaviour for , with an asymptotic value that is close to the random close packing value for hard spheres. The evidence we obtained suggests that basically coincides with the liquid (colloid-rich) branch of the metastable coexistence curve, rather than with the lower (and φ-dependent) values expected for an attractive glass line penetrating inside the coexistence region.
analytical centrifugation; compressive rheology; depletion forces; disperse systems; gels; glasses; Materials Science (all); Condensed Matter Physics
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/1044800
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