Towards synchronously improving dielectric performance and thermal conductivity in Ni/PVDF by tailoring core-shell structured Ni@NiO particles

An insulating interlayer between conductive particles and polymer is crucial for preparing polymer dielectrics with high dielectric permittivity ( ε) but low loss and high breakdown strength ( E b ). To restrain the large loss of raw nickel (Ni)/poly (vinylidene fluoride) (PVDF) composites when still maintaining a high- ε at the percolation threshold ( f c ) of conductive fillers, in this work, nanoscale nickel oxide (NiO) shell with diverse thickness was coated around the surface of Ni particles via a facile thermal calcination at 650°C under air, and the gained Ni@NiO particles were composited with PVDF to produce morphology-controllable high- ε, low loss composites. The influences of the NiO shell and thickness on the dielectric performances and thermal conductivity (TC) of the composites were investigated in terms of filler loading and frequency. Compared with raw Ni/PVDF, the Ni@NiO/PVDF composites exhibit remarkably suppressed dielectric loss and enhanced E b and TC because the NiO interlayer not only prevents the Ni particles from direct contact and hinders the long-range electron migration thereby resulting in rather low leakage current, but also simultaneously suppresses thermal interfacial resistance and enhances interfacial compatibility between the fillers and the matrix subsequently resulting in improved TC. Therefore, the Ni@NiO/PVDF with high ε-low loss, heightened E b and TC present appealing potential applications in microelectronics and electrical industries.