Double Layer Capacitance Measurements To Characterize the Water Intrusion into Porous Materials

In this work, we have proposed and substantiated a novel approach to study the dynamic wetting behavior during water intrusion, demonstrated for a porous carbon fiber substrate. The proposed methodology quantifies the evolution of the wetted interfacial area during intrusion by electrochemically measuring the double layer capacitance, which is proportional to the solidliquid interfacial area. We investigated the intrusion behavior for three commercially available substrates with distinct thicknesses and internal microstructures, using a combination of capacitance and pressure measurements. For the same imbibed volume of water, the pressure increase was comparable, while the capacitance increase was distinct for the substrates with dissimilar internal microstructures. The hydraulic radius and the cross section of the intruding meniscus of water reduced during the course of intrusion. A correlation between the capacitance and the pressurevolume work has been proposed as a measure for quantifying the favorability of wetting the fiber surface, during the liquid intrusion into the porous structure. The pressurevolume work done in wetting the fiber surface showed dependence on the internal microstructure and remains constant during the course of water intrusion. The approach presented here can facilitate quantitative characterization of the wetting behavior, and the new parameter (wetted interfacial area) could be used as the basis of analytical models for the water transport behavior through these porous structures.