Shear Thickening Fluids
When subjected to increasing shear rates, concentrated colloidal suspensions can exhibit a steep rise in viscosity. This shear thickening phenomenon can damage processing equipment and induce dramatic changes in suspension microstructure, such as particle aggregation, which results in poor fluid and coating qualities. On the other hand, this behavior can be exploited in the design of damping and control devices, whereby the fluid can limit the maximum rate of flow through a highly nonlinear response.
It has been demonstrated that reversible shear thickening in concentrated colloidal suspensions is due to the formation of jamming clusters bound together by hydrodynamic lubrication forces, often denoted by the term ˇ°hydroclusters? The microstructure of shearing suspensions has been studied by rheo-optical experiments, neutron scattering and stress-jump rheological measurements. The onset of shear thickening in steady shear can now be quantitatively predicted for suspension of hard-spheres and electrostatically stabilized dispersions.
The diagram below illustrates the shear thickening phenomenon, including schematics of the microstructure of a shear thickening suspension.
More information on shear thickening fluids in conjunction with small angle neutron scattering can be found at C&EN.
M. J. Decker, C. J. Halbach, C. H. Nam, N. J. Wagner and E. D. Wetzel, "Stab resistance of shear thickening fluid (STF)-treated fabrics" Composites Science and Technology, accepted, August 2006
Y. S. Lee and N. J. Wagner, "Rheological Properties and Small Angle Neutron Scattering of a Shear Thickening, Nanoparticle Dispersion at High Shear Rates" I&EC Research, to appear Nov. 2006.
R. G. Egres, F. Nettesheim and N. J. Wagner,"Rheo-SANS investigation of acicular precipitated calcium carbonate colloidal suspensions through the shear thickening transition" J. Rheology, In Press, 2006.
L. Krishnamurthy, N. J. Wagner and J. Mewis, "Shear Thickening in Polymer Stabilized Colloidal Dispersions" J. Rheology, 39(6), 1347-1360, 2005.
S. S. Shenoy and N. J. Wagner, "Influence of Medium Viscosity and Adsorbed Polymer on the Reversible Shear Thickening Transition in Concentrated Colloidal Dispersions" Rheol. Acta, 44, 360-371, 2005.
R. G. Egres and N. J. Wagner, "The rheology and microstructure of acicular precipitated calcium carbonate colloidal suspensions through the shear thickening transition" Journal of Rheology, 49(3), 719-746, 2005.
Y. S. Lee and N. J. Wagner, "Dynamic properties of shear thickening colloidal suspensions" Rheologica Acta, 42(3), 199-208, 2003.
B. J. Maranzano and N. J. Wagner, "Flow-Small Angle Neutron Scattering Measurements of Colloidal Dispersion Microstructure Through the Shear Thickening Transition" J. Chem. Phys., 117, 10291-10302, 2002. Also selected to appear on the Virtual Journal of Nanoscale Science & Technology, Dec. 2nd, 2002.
B. J. Maranzano and N. J. Wagner, "The effects of interparticle interactions and particle size on reversible shear thickening: hard-sphere colloidal dispersions" Journal of Rheology, 45(5), 1205-1222, 2001.
J. W. Bender, S. S. Shenoy and N.J. Wagner, "E-FiRST: Electric Field Responsive Shear Thickening Fluids" Rheol. Acta, 42, 287-294 (2003).
B. J. Maranzano and N. J. Wagner, "The Effects of Particle Size on Reversible Shear Thickening of Concentrated Colloidal Dispersions" J. Chem. Phys., 114(23), 10514-10527, 2001.
J. W. Bender and N. J. Wagner, "Reversible Shear Thickening in Monodisperse and Bidisperse Colloidal Dispersions" Journal of Rheology, 40(5), 899-916, 1996.
J. W. Bender and N. J. Wagner, "Optical Measurement of the Contributions of Colloidal Forces to the Rheology of Concentrated Suspensions" J. Coll. Int. Sci., 172, 171-184, 1995.