Restructuring and aging in a capillary suspension
- 520 Downloads
The rheological properties of capillary suspensions, suspensions with small amounts of an added immiscible fluid, are dramatically altered with the addition of the secondary fluid. We investigate a capillary suspension to determine how the network ages and restructures at rest and under applied external shear deformation. The present work uses calcium carbonate suspended in silicone oil (11 % solids) with added water as a model system. Aging of capillary suspensions and their response to applied oscillatory shear is distinctly different from particulate gels dominated by the van der Waals forces. The suspensions dominated by the capillary force are very sensitive to oscillatory flow, with the linear viscoelastic regime ending at a deformation of only 0.1 % and demonstrating power-law aging behavior. This aging persists for long times at low deformations or for shorter times with a sudden decrease in the strength at higher deformations. This aging behavior suggests that the network is able to rearrange and even rupture. This same sensitivity is not demonstrated in shear flow where very high shear rates are required to rupture the agglomerates returning the apparent viscosity of capillary suspensions to the same viscosity as for the pure vdW suspension. A transitional region is also present at intermediate water contents wherein the material response depends very strongly on the type, strength, and duration of the external forcing.
KeywordsCapillary suspensions Aging Capillary force
EK would like to acknowledge financial support from the European Research Council under the European Union’s Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 335380.
- Dittmann J, Koos E, Willenbacher N (2013) Ceramic capillary suspensions: novel processing route for macroporous ceramic materials. J Am Ceram Soc 96(2):391–397Google Scholar
- Gallay W, Puddington IE (1943) Sedimentation volumes and anamalous flow in lyophobic suspensions. Can J Chem 21(2):171Google Scholar
- Rumpf H (1962) The strength of granules and agglomerates. In: Knepper WA (ed) Agglomeration. Wiley, New York, pp 379–418Google Scholar