Scaling of the shear viscosity of the system nitrobenzene—<i>n</i>-hexane in the critical region

Dega-Dałkowska, A.

doi:10.1080/01411598908206833

Cited by 3 publications

(1 citation statement)

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“…Experiments on molecular systems indicate a very small critical exponent for the zero shear and zero frequency shear viscosity, [1][2][3][4] or a logarithmic divergence, 5 although in a few papers it is shown that the experimental accuracy is not sufficient to distinguish between the two. [6][7][8] It is also reported that neither an exponential nor logarithmic divergence occurs, but that the viscosity remains finite at the critical point.…”

Section: Introductionmentioning

confidence: 99%

Critical behavior of the non-Newtonian shear viscosity of colloidal systems

Dhont

1995

The Journal of Chemical Physics

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The anomalous behavior of the ͑zero frequency͒ shear viscosity of colloidal systems on approach of the gas-liquid critical point is analyzed. As a result of hydrodynamic interactions, the anomalous behavior is found to be qualitatively different from that of molecular systems. On the basis of the asymptotic solution of the Smoluchowski equation for the shear rate dependent pair-correlation function, an expression for the non-Newtonian zero frequency viscosity of a near-critical suspension is derived. The viscosity depends on two dimensionless groups: on Ϫ1 d via a cutoff function and on ϰ␥ 4 via the structurefactor ͑ is the correlation length in the equilibrium system, d is the core diameter, and ␥ is the shear rate͒. The transition from weak to strong shear occurs at Ϸ1. The anomalous behavior of both the zero shear viscosity and the non-Newtonian characteristics is formally due to the fact that close to the critical point, where is large, a very small shear rate ␥ is sufficient to make a large number. The critical exponent for the zero shear viscosity is found to be equal to that of the correlation length. This exponent is much larger than for molecular systems, which is known to be very small ͑Ϸ0.03͒. The exponential behavior sets in at /dϷ3.

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