How can impedance spectroscopy be used for carbon dispersion characterization?

Structural characterization of carbon dispersions is important for understanding processes such as dispersion, coating, and drying. Impedance spectroscopy is a useful technique because dispersions can be measured in their original state; however, the accessible structural information depends on the measurement configuration and frequency range, and practical guidance for selecting the appropriate configuration has not yet been established. In this study, rheo-impedance spectroscopy (Rheo-IS) and high-frequency impedance spectroscopy (HF-IS) were compared using percolated and non- or weakly percolated carbon dispersions to clarify how impedance spectroscopy can be used for carbon dispersion characterization. Rheo-IS captured the electronic conduction response through a carbon network bridging the electrodes in the percolated dispersion, enabling evaluation of carbon-network connectivity. In contrast, HF-IS enabled stable measurement of the high-frequency response in non- or weakly percolated dispersions, providing information on the agglomerate dispersion state. These results demonstrate the importance of selecting an appropriate impedance measurement configuration according to the percolation state and the target structural information of carbon dispersions. This configuration-dependent application of impedance spectroscopy can support process understanding and control in carbon-dispersion-based manufacturing.