In order to observe the dispersion of CB in conductive layers, the
specimens were quenched in liquid nitrogen and cryogenically
ruptured to obtain sections along the extrusion direction. The
freshly broken surfaces were sputter coated with Au before scanning
electron microscope (SEM) observation and then observed in
a JEOL JSM-5900LV SEM. The polar light microscope (PLM) observation
was performed using an Olympus BX51 polarizing microscope
with an attached camera, and the sample thickness was
approximately 20 mm.