Paper Number
SC40 

Session
Suspensions, Colloids, and Granular Materials

Title
Rheology and shear-induced structural breakdown in model conductive carbon black suspensions

Presentation Date and Time
October 23, 2019 (Wednesday) 4:35

Track / Room
Track 2 / Room 304

Authors (Click on name to view author profile)

  1. Hipp, Julie B. (University of Delaware, Chemical and Biomolecular Engineering)
  2. Richards, Jeffrey J. (Northwestern University, Chemical & Biological Engineering)
  3. Wagner, Norman J. (University of Delaware, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Julie B. Hipp1, Jeffrey J. Richards2, and Norman J. Wagner1
1Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716; 2Chemical & Biological Engineering, Northwestern University, Evanston, IL 60203

Speaker / Presenter 
Hipp, Julie B.

Text of Abstract
The shear-dependent behavior of carbon black suspensions has been widely studied due to their use in many applications where flow is an important aspect as well as their use as a model colloidal suspension for understanding the general behavior of thixotropic suspensions and suspensions of non-uniform particles. In these suspensions, it is commonly understood that shear-dependent properties of interest are directly related to the suspension microstructure. However, direct measurements of this shear-dependent microstructure are lacking, especially at high particle loadings where interactions play a significant role. In this research, the shear-induced microstructure of carbon black suspensions is directly measured by performing Rheo-USANS (Ultra-Small Angle Neutron Scattering) experiments at a range of applied shear rates. The suspensions studied consist of two conductive carbon blacks suspended in either propylene carbonate or mineral oil at a range of volume fractions above the gel point. Therefore, these experiments explore the effects of interaction strength, particle loading, and building block characteristics on the shear-dependent size and fractal dimension of carbon black agglomerates. This structural information is quantified using a hierarchical fractal model and shows a decrease in agglomerate size with increasing shear intensity as well as a volume fraction-dependent agglomerate fractal dimension. This structural information is paired with rheo-electric measurements which show that the extent of structural breakdown is related to the measured shear-thinning behavior and evolution in electrical conductivity. The scaling behaviors of these properties are shown to be system-specific, which points towards a different mechanism by which structures are formed in these systems. This research provides quantitative structure-property relationships for the design of carbon black suspensions for applications such as electrochemical energy storage methods as well as for related suspensions based on particle gels.