Flowing suspensions of carbon black with high electronic conductivity for flow applications: Comparison between carbons black and exhibition of specific aggregation of carbon particles H. Parant a , G. Muller b , T. Le Mercier b , J.M. Tarascon d , P. Poulin a , A. Colin c, * a Centre de Recherche Paul Pascal, CNRS, Universite de Bordeaux,115 Avenue Schweitzer, 33600, Pessac, France b Solvay, Research and Innovation Center Paris, F-93308, Aubervilliers, France c ESPCI Paris, PSL Research University, CNRS, Laboratoire Sciences et Ingenierie de la Matiere Molle, UMR 7615,10 Rue Vauquelin, 75231, Paris Cedex 05, France d College de France, Laboratoire Chimie du Solide et Energie, 11 Place Marcelin-Berthelot, 75005, Paris, France article info Article history: Received 8 November 2016 Received in revised form 28 February 2017 Accepted 9 April 2017 Available online 12 April 2017 abstract Flow batteries and flow capacitors are promising technologies to store and generate electrical power. However, to increase their energy performances, low viscosity, electronic conductive suspensions loaded with active material are required. Comparing the behavior of three types of carbon black particles in water suspensions, we show that compressed acetylene carbon black particles suspensions display a slow variation of viscosity and conductivity as a function of concentration. It allows reaching interme- diate viscosity (1 Pa s for a shear rate of 10 s 1 ) with high electronic conductivity between 0.1 and 5 mS/ cm. This behavior is very promising for flow applications. At small range, attractive van der Walls in- teractions between carbon aggregates dominate. However, at longer range, compressed acetylene carbon black particles are highly attractive in water. After shearing with emulsifier, fractal-like shape clusters are obtained through a diffusion limited aggregation process. These fractal clusters constitute the building blocks of a flexible connected network. By contrast, for the two other investigated carbons, an energy barrier has to be overcome to enable aggregation. The clusters are compact and result from a reaction limited aggregation process. For these two carbons, the conductivity and the viscosity vary abruptly at percolation which is not suitable for flow devices. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Carbon materials are widely studied because of their electrical properties, their chemical and mechanical resistance. Many com- posite materials include carbon as a filler in polymer matrix to provide high mechanical resistance but also to have interesting electrical properties such as low electronic percolation [1], elec- trostrictive and piezoresistive effects [2,3], high permittivity for capacitive electrodes [4,5], high electronic conduction for flexible electrodes [6,7] or conductive ink [8], depending on the amount of filler. The above materials are often made by liquid processing. In this view, the study of colloidal dispersion of carbon particles in liquid media is of significant importance, especially in water for environmental and economical reasons. A large part of recent work focuses on CNT suspensions [6,9e11] and graphene suspensions [12,13] but carbon black particles are also very promising materials because of their low cost [14,15]. Generally, the suspensions are investigated at rest or dried to formulate electrodes as in battery applications. However, their flow behavior is critical when new technologies such as redox batteries or flow capacitors are considered. In this study, a particular attention is paid to the percolation behavior of water carbon black particles suspensions. Carbon black (CB) elementary particles have a characteristic size around several microns. They are made of primary graphitic particles of 100 nm in size chemically linked. The smallest units in CB suspensions are effectively the elementary particles and not the primary particles, since the elementary CB particles can not be broken, neither by thermal fluctuations, nor by adding a dispersant nor by applying a high shear, e.g. during rheology tests or sonication. Those elemen- tary CB particles can then aggregate together to form carbon clusters * Corresponding author. E-mail address: annie.colin@espci.fr (A. Colin). Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon http://dx.doi.org/10.1016/j.carbon.2017.04.014 0008-6223/© 2017 Elsevier Ltd. All rights reserved. Carbon 119 (2017) 10e20