MWCNTs-TiO₂ core-shell nanoassemblies for fabrication of poly(vinylidene fluoride) based composites with high breakdown strength and discharged energy density

Dielectric polymer composites with high breakdown strength and discharged energy density have potential applications in modern electric power systems. In this study, composites comprising MWCNTs-TiO₂ core-shell nanoparticles and poly(vinylidene fluoride) (PVDF) were fabricated by a solution casting method, followed by a melting and quenching process. The obtained composites are γ-phase PVDF dominated and present a dense structure. By the incorporation of MWCNTs-TiO₂ core-shell nanoparticles, the dielectric constant of composites can be significantly enhanced while the dielectric loss of composites remains low. Because of the core-shell structure of well-dispersed MWCNTs-TiO₂ and their strong interactions with matrix, high breakdown strength above 175 V/μm can be achieved in the composites. Additionally, the composites exhibit enhanced discharged energy density, which can be as high as 6.4 J/cm³ at 250 V/μm, while the maximum discharged energy density obtained in pure PVDF is only 2.6 J/cm³ (270 V/μm).