Paper Number
GN41 My Program
Session
Gels and Networks
Title
Visualization of plastic events in colloidal gels
Presentation Date and Time
October 16, 2024 (Wednesday) 1:30
Track / Room
Track 1 / Waterloo 3
Authors
- Lehéricey, Pierre (Eth zurich, Materials)
- Niggel, Vincent (Eth Zurich, materials)
- Isa, Lucio (ETH Zürich, Department of Materials)
- Vermant, Jan (ETH Zurich, Department of Materials)
Author and Affiliation Lines
Pierre Lehéricey, Vincent Niggel, Lucio Isa and Jan Vermant
Department of Materials, ETH Zürich, Zürich, Zürich 8093, Switzerland
Speaker / Presenter
Vermant, Jan
Keywords
gels; networks
Text of Abstract
The yielding of colloidal gels is a gradual process where the transition from microscopic elastic to plastic deformations accompanies changes in the rheological properties. Whereas for glassy, disordered systems this is relatively well understood, for lower volume fraction systems with more open - or even fractal - structures our understanding on how stress is distributed over the particle networks and how plastic events are generated is less understood, in particular in relation to the physical chemistry of the particles used. To study this in real space, we report on high speed confocal studies of the yielding transition of depletion flocculated colloidal particles. PMMA-g-PHSA particles are used in an index and density matched suspending medium and the response to simple shear deformations is studied. The parameters studied are the volume fraction and the strength of the depletion force. Non affine motions or discontinuities identified with the optical flow method are measured as a function of strain for stresses in the vicinity of what is typically described as the rheological yield stress. We quantify the number of events per unit volume and the number of particles participating in such plastic events as a function of the different parameters. The goal is to get insights into the stress activated kernels which dictate plastic flow.