Relaxation processes in nano-colloidal suspensions
Samanvaya Srivastava (Cornell University), Lynden Archer (Cornell University)
Complex Fluids: Suspensions, Emulsions, and Gels
Tue 2:40 - 4:00
Barus-Holley 160
Time scales associated with relaxation processes in colloidal suspensions can span many orders of magnitudes. It is known that external forces produced by shear flow can probe as well as speed up the underlying relaxation process. Well-dispersed sterically-stabilized nanoparticle suspensions allow us to probe dynamics in suspensions on length scales where thermal forces play a dominant role in aiding particle relaxations. At high particle volume fractions, we find that these "nano-colloid" suspensions simultaneously exhibit properties associated with jammed materials, including solid-like viscoelastic behavior and strong shear thinning, as well as those normally associated with simple fluids, such as Newtonian flow behavior and complete decorrelation in particle positions corresponding to terminal relaxation. In this talk, we put a spotlight on the various time scales associated with the dynamical processes that produce these paradoxical properties in nanoparticle suspensions. In particular, we propose relationships between suspension structure under quiescent conditions as well as under shear, and the various relaxation processes that occur in nanoparticle suspensions, including diffusion, cage rattling (beta relaxation), cage escape (alpha relaxation) and cage renewal.