Paper Number
SC45 

Session
Suspensions, Colloids and Granular Media

Title
Percolation behavior of carbon black suspensions in polar aprotic solvents

Presentation Date and Time
February 16, 2017 (Thursday) 9:30

Track / Room
Track 1 / Audubon B

Authors (Click on name to view author profile)

1. Hipp, Julie B. (University of Delaware, Chemical and Biomolecular Engineering)
2. Richards, Jeffrey J. (NIST Center for Neutron Research)
3. Wagner, Norman J. (University of Delaware, Chemical & Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Julie B. Hipp¹, Jeffrey J. Richards², and Norman J. Wagner^1
1Chemical & Biomolecular Engineering, University of Delaware, Newark, DE 19716; ²NIST Center for Neutron Research, Gaithersburg, MD

Speaker / Presenter 
Hipp, Julie B.

Text of Abstract
In this work, the microstructural origin of the rheo-electric behavior of carbon black gels and suspensions is studied. These materials find widespread use as conductive fillers in composites and slurry-based electrochemical energy storage technologies. In these applications, both the viscosity and electrical conductivity are key design parameters determined by their microstructure. Using small angle neutron scattering (SANS) and electron microscopy, we perform detailed structural analysis on carbon black suspensions as a function of volume fraction for two commonly used conductive additives – KetjenBlack and Vulcan. From these measurements, the static structure factor is determined and characterized at low-Q by a power-law scaling, I(Q) ~ Q^-3. Similar to depletion gels, this scaling confirms that carbon black gels form as a result of arrested phase separation. We characterize the onset of gelation using oscillatory rheological measurements and identify the percolation threshold associated with the jamming transition. While the onset of mechanical percolation is commonly associated with the electrical percolation threshold for these materials, results from impedance spectroscopy measurements show that the electrical percolation threshold occurs at far lower volume fractions. Further, the power-law scalings associated with the yield stress and elastic moduli are not consistent with that extracted from the conductivity. These results suggest a rich relationship between electrical conductivity and the fluid properties of carbon black dispersions that could improve the design of future low-viscosity, high conductivity conductive additives for electrochemical flow applications.