Dielectric properties of Ni/poly(vinylidene fluoride) composites at high frequencies

The metal-polymer composites can possess a high dielectric constant with low filler content, and preserve the flexibility of the polymer matrix. Nickel (Ni) powder could be cheaply obtained through aqueous chemical reduction and not easily oxidized in air. In this study, composites of poly(vinylidene fluoride) (PVDF) filled with 0.7μm (average size) of metallic particles of nickel (Ni) were prepared via a grinding and hot-molding technique. The peak crystallization temperature (Tcp) of the composites shifts by around 4.5°C, from ~128.5°C for PVDF to ~133°C for the composites with 10wt% filler. The crystallization data indicates that the crystallinity of PVDF decreases with the increase of Ni content. The dielectric permittivity of the composite filled with 65wt% Ni particles is 800 at the frequency of 107Hz, while the dielectric loss tangent is about 1.6. The reason of high dielectric constant could be explained by the microcapacitor model and percolative theory. The easy processing, flexibility, and high dielectric constant of the composites make the composites attractive for practical applications in embedded capacitors.