Article ID Journal Published Year Pages File Type
592505 Colloids and Surfaces A: Physicochemical and Engineering Aspects 2015 7 Pages PDF
Abstract

•Higher pH value leads to higher critical shear stress for the onset of shear thickening.•Higher critical shear stress corresponds to higher low-shear-rate viscosity at high pH value.•Correlation between low-shear-rate viscosity and critical shear stress could change.

The effects of pH on the initial shear thinning and subsequent thickening behaviors of fumed silica suspensions with increased shear rate were investigated. The critical shear stress observed at the onset of the shear thickening of suspensions can be tuned through the pH of added aqueous solutions. The increase in pH of the addition shifts the onset of shear thickening to higher shear stresses. This finding is consistent with the trend of prediction models that involve the hydrocluster mechanism for shear thickening. A high critical shear stress at a relatively high pH corresponds to a high value of low-shear-rate viscosity, coincident with a high friction coefficient between two silica surfaces that are lubricated with high pH solutions. The correlation between low-shear-rate viscosity and critical shear stress of suspensions depends on whether the added dilute solution is HCl or NaOH.

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Related Topics
Physical Sciences and Engineering Chemical Engineering Colloid and Surface Chemistry
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