Percolation behavior of polymer/metal composites on modification of filler

Polymer-metal composites with different fillers, such as nanocrystalline nickel (n-Ni), core shell n-Ni and nickel oxide (NiO) [n-Ni@NiO] were prepared under the same processing conditions with polyvinyledene fluoride matrix. The larger value of critical exponents (s and s') and percolation threshold (f c ∼ 0.30) for n-Ni@NiO composites as compared to n-Ni composites (fc ∼ 0.07) and a comparable effective dielectric constant (εeff ∼ 300) with low loss tangent (tan δ ∼ 0.1) at 100 Hz in case of percolative n-Ni@NiO composite was observed. The core shell structure [n-Ni@NiO] also shows a very high value of εeff ∼ 6000 with tan δ ∼ 8 at 40 Hz. The results have been explained by using boundary layer capacitor effect and the percolation theory. The difference in fc and critical exponents is attributed to NiO insulating layer that gives rise to different extent of continuumness at fc and have been explained with the help of Swiss cheese model. © 2014 World Scientific Publishing Company.