Shear-thickening response of fumed silica suspensions under steady and oscillatory shear
- North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical Engineering
Suspensions of fumed silica in polypropylene glycol exhibit shear-thickening under steady shear and strain-thickening under oscillatory shear. Strain-thickening refers to a sharp increase in the complex viscosity {eta}* observed at critical combinations of strain-amplitude and frequency. Two regimes of strain-thickening behavior have been found: The first occurs at high critical strains and low frequencies, whereas the second occurs at high critical frequencies and a constant lower strain. Strain-thickening in the first regime can be explicitly correlated with steady shear-thickening, using a modified version of the Cox-Merz rule. Accordingly, strain-thickening data for the complex viscosity {eta}* as a function of the maximum dynamic shear-rate {gamma}{sub 0}{omega} can be superposed against shear-thickening data for the steady viscosity as a function of the steady shear rate. Such a correlation between the two kinds of thickening phenomena has not been reported previously. The combination of shear- and strain-thickening behavior can be qualitatively explained using a clustering mechanism, which attributes the various phenomena to the formation of temporary, flow-induced clusters. The two regimes of strain-thickening are a result of differences in the relative ease of cluster formation.
- OSTI ID:
- 438887
- Journal Information:
- Journal of Colloid and Interface Science, Journal Name: Journal of Colloid and Interface Science Journal Issue: 1 Vol. 185; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English
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