On the possibility of using two models of the viscosity superanomaly effect for analyzing the flow curves of structured disperse systems

Khil’ko, S. L.; Титов, Е. В.; Fedoseeva, A. A.; Petrenko, A. G.; Fedoseev, R. A.

doi:10.1134/s1061933x06010145

Cited by 3 publications

(2 citation statements)

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“…[64][65][66] A number of previous reports have observed a similar "viscosity anomaly" associated with the onset of shear banding. 35,[67][68][69][70][71][72] No clear evidence of banding texture was observed by direct observation, but the mechanism of individual sliding layers above a critical rate of deformation appears to be consistent with the microstructure of the smectic liquid crystals here. Further studies incorporating in situ light scattering or SAXS measurements during shear deformation, and potentially velocity tracking measurements, will be necessary to directly identify the length scale associated with the banding texture, if present.…”

Section: Steady Shear Viscositysupporting

confidence: 62%

“…Based on the previous work, the negative slope of shear stress (decreasing stress with increasing shear rate) is attributed to a mechanical instability associated with a non-uniform velocity prole through the gap of the instrument. 67,68,73 Olmsted proposed a general constitutive relationship to account for this behaviour based on the co-existence of multiple "phases" with distinct viscosities at a given shear rate (or shear stress). 74 In this context, the anomalous shape of the ow curves for the concentrated group of smectic suspensions may be attributed to a transition between microstructural "regimes," as suggested in Fig.…”

Section: Steady Shear Viscositymentioning

confidence: 99%

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Interlayer structure and self-healing in suspensions of brush-stabilized nanoplatelets with smectic order

White

Wong

et al. 2015

Soft Matter

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We have investigated the rheology of an uncured epoxy fluid containing high aspect ratio (length/thickness ≈ 160) α-zirconium phosphate (ZrP) nanoplatelets with smectic order. The nanoplatelets were exfoliated into monocrystalline sheets with uniform thickness using a monoamine-terminated oligomer. The oligomers were densely grafted to the plate surfaces and behave as a molecular brush. Suspensions containing ∼ 2 vol.% ZrP and above show liquid crystalline order with scattering peaks characteristic of a smectic (layered) mesophase. At much higher loading, ∼ 4 vol.% ZrP, there is a sharp transition in visual appearance, steady shear rheology, and linear and non-linear viscoelasticity that is attributed to the reversible interdigitation of oligomer chains between closely spaced layers. The oligomers are proposed to serve as inter-lamellar bridges that store elastic stresses for intermediate rates of deformation, but are able to relax on longer time scales. Under steady shearing conditions, the smectic suspensions with "overlapped" microstructure show a discontinuous flow curve characteristic of shear banding that is attributed to the dynamic pull-out of oligomer chains from the overlap region. At high shear rates, the limiting viscosity of the concentrated suspensions is on the same order of magnitude as the unfilled suspending fluid. When the rate of deformation is reduced below a critical time scale, the original network strength, and corresponding microstructure, is recovered through a passive self-healing process. The unique combination of concentration-dependent yield stress, low post-yield viscosity, and self-healing is potentially useful for various applications in the liquid state, and desirable for scalable processing of nanocomposite materials for structural applications.

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