Paper Number
GG25 

Session
Arrested Systems: Gels and Glasses

Title
Investigation of the yielding transition in concentrated colloidal systems via rheo-XPCS

Presentation Date and Time
October 13, 2021 (Wednesday) 1:55

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Donley, Gavin J. (Georgetown University, Physics)
  2. Park, JD (Sookmyung Women's University, Chemical Engineering)
  3. Wade, Matthew A. (University of Illinois Urbana-Champaign, Chemical and Biomolecular Engineering)
  4. Narayanan, Suresh (Argonne National Laboratory)
  5. Leheny, Robert L. (Johns Hopkins University)
  6. Harden, James L. (University of Ottawa, Physics)
  7. Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Gavin J. Donley1, JD Park2, Matthew A. Wade3, Suresh Narayanan4, Robert L. Leheny5, James L. Harden6 and Simon A. Rogers3
1Physics, Georgetown University, Washington DC, DC 20057; 2Chemical Engineering, Sookmyung Women's University, Seoul, Republic of Korea; 3Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801; 4Argonne National Laboratory, Lemont, IL; 5Johns Hopkins University, Baltimore, MD; 6Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada

Speaker / Presenter 
Donley, Gavin J.

Keywords
experimental methods; colloids; glasses; non-Newtonian fluids; rheology methods; suspensions

Text of Abstract
We probe the microstructural yielding dynamics of a concentrated colloidal system by performing creep/recovery tests with simultaneous collection of scattering data via X-ray Photon Correlation Spectroscopy (XPCS). This combination of rheology and scattering allows for time-resolved observations of the microstructural dynamics as yielding occurs, which can be linked back to the applied rheological deformation to form structure-property relations. To more accurately track the non-equilibrium processes which occur under yielding, we utilize two-time correlation functions, which provide additional time-resolved information that is inaccessible via more typical one-time correlations. Under sufficiently small applied creep stresses, examination of the correlation in the flow direction reveals that the scattering response recorrelates with its pre-deformed state, indicating nearly-complete microstructural recovery, and the dynamics of the system under these conditions slows considerably. Conversely, larger creep stresses increase the speed of the dynamics under both applied creep and recovery. The data show a strong connection between the microstructural dynamics and the acquisition of unrecoverable strain. By comparing this relationship to that predicted from homogeneous, affine shearing, we find that the yielding transition in concentrated colloidal systems is highly heterogenous on the microstructural level.