STL files and data to support: Improvements in methods for measuring the volume conductivity of electrically conductive carbon powders

Electrically conductive carbon powders are commonly used as filler
materials in polymers to create electrically semi-conductive composite
materials for use in battery electrodes and anti-static applications.
Current methods for characterizing the conductivity of these powders use
two pistons to compress the powders. Two-piston methods are known to
underestimate conductivity. This study develops a guard-electrode method
based on ASTM D257 to better characterize the bulk conductivity and
impedance spectra of electrically conductive powders. The conductivity and
impedance spectra of a highly conductive powder (copper powder) and a low
conductivity powder (cellulose) were used to bound the conductivity of
carbon black, graphite, and biochar. Powders were measured through a full
range of compression with both the two-piston and the guard-electrode
method. In all cases, measurements using the guard-electrode method have
higher conductivity and lower impedance than the same powders measured
using the two-piston method. The grain conductivity of the particles is
obtained through fitting the relationship of conductivity versus packing
fraction using the GEM equation. The guard-electrode method is shown to be
more similar to established conductivity values as measured via a
four-probe technique for copper and graphite then the two-piston method.