Levich Institute Seminar Announcement, 02/16/2016
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Sachin Velankar
University of Pittsburgh
Chemical and Petroleum Engineering Department
"Capillarity, Wetting, and Rheology in Multiphase Particle-Liquid-Liquid Mixtures "
The colloids and rheology community has enormous knowledge about the structure and rheology of suspensions comprising particles dispersed in a liquid. Much less is known about suspensions composed of particles suspended in two immiscible fluids. In such cases, the ternary liquid/liquid/particle mixture can show a variety of microstructures: particles aggregated by fluid menisci, compact capillary aggregates, Pickering emulsions, and bicontinuous morphologies. Many of these mixtures show highly non-Newtonian flow characteristics including severe shear thinning or yield stress behavior. These microstructures, and the resulting rheological properties, result from a coupling between interfacial tension between the fluids, particle wettability, and viscous forces during mixing. This talk will explore these issues in two different systems: oil/water/particle mixtures, and mixtures of particles with two immiscible polymeric liquids. We will catalog the transitions between various microstructures, and the corresponding changes in rheology, as composition and particle wettability is changed. Not only do these two systems show similar behavior, but a diverse variety of mixtures from the literature - including air/water/particle mixtures - also behave similarly. This apparent universality indicates features that are shared across all liquid/fluid/particle mixtures, and we will propose a non-equilibrium state diagram for such ternary mixtures.
BRIEF ACADEMIC/EMPLOYMENT HISTORY
Undergraduate in Chemical Engineering at IIT Bombay, India, followed by PhD in Chemical Engineering at the University of Delaware (1999), followed by post-doctoral fellowships at the Katholieke Universiteit Leuven, Belgium and University of Minnesota. I have been on the Chemical Engineering faculty at the University of Pittsburgh since 2002, presently Associate Professor.
RECENT RESEARCH INTERESTS
Structure and rheology in multiphase particulate systems; buckling phenomena in thin solid films