Influence of coupling agent on microcosmic morphology and dielectric properties of energy-storage nanocomposite

A series of PVDF-based composite materials with 20 % volume concentrations of nano-sized BaTiO₃ fillers were prepared and studied by solutions-casting. The samples were added with different contents of KH550 as coupling agent. The four main dielectric parameters: dielectric constant, dielectric loss tangent, dielectric breakdown strength and resistivity under high electrical field, were tested. And the energy-storage densities of the samples were also calculated. The results showed that the nanocomposites with 1.0 wt% of KH550 exhibited the appropriate dielectric constant, loss tangent, high dielectric breakdown strengths, high resistivity and high energy-storage density, which was 27.74, 0.039, 245 MV/m, 1,625 MΩ m and 7.4 J/cm³, respectively. This implied that such kind of composites could be used as the dielectric layers of pulsed-power capacitors. In order to explain the relationships between the dielectric properties and the microcosmic physical and chemical properties, the samples were also studied by XRD, SEM and FTIR. The results demonstrated that the coupling agent could improve the filler-matrix interfaces and had significant influence on the dielectric properties of the nanocomposites.