Effects of the amount of nickel powder (Ni) in Ni-carbon fiber (CF) hybrid filler systems
on the conductivity(or resistivity) and thermal coefficient of resistance (TCR) of filled high
density polyethylene were studied. Increases of the resistivity and TCR with increasing Ni
concentration at a given hybrid filler content were observed. Using the fiber contact model,
we showed that the main role of Ni in the hybrid filler system is to decrease the interfiber
contact resistance when Ni concentration is less than the threshold point. The formation
of structural defects leading to reduced reinforcing effect resulted in both a reduction of
strength and an increase of the coefficient of thermal expansion in the composite film; these
changes are responsible for the increases of both resistivity and TCR with increasing Ni
concentration in the hybrid filler system.