Enhanced dielectric properties of poly(vinylidene fluoride-co-hexafluoropropylene) composites using oriented ZnFe2O4@BaTiO3 rod.

The distribution of functional filers in polymer matrix composites has a decisive effect on the material properties, however, functional fillers cannot be distributed in an orderly way and orientation in the polymerization system under natural conditions. It was found that the application of external field in the preparation process of materials can effectively improve the dispersion of functional fillers, and induce the orderly orientation of functional fillers, which can endow polymer matrix composites with excellent properties. In this paper, a novel core–shell structural nanorod with magnetic rod-shaped zinc ferrite (ZnFe₂O₄)(R-ZFO) as core and barium titanate (BaTiO₃)(BT) as shell was successfully prepared by sol gel method. Then this core–shell nanorod were doped into the polyvinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP)) to prepare the composites. The arrangement of ZnFe₂O₄@BaTiO₃ nanorod in P(VDF-HFP) was controlled by a parallel magnetic field during the hot-press to obtain an ordered directional arrangement. The microstructure and properties of composites were investigated and the orientation effects of ZnFe₂O₄@BaTiO₃ along the electric field orientation on the dielectric performance of P(VDF-HFP) composites were also analyzed. Results showed that ZnFe₂O₄@BaTiO₃ prepared in this experiment are composed of a core–shell particle with a magnetic core and a dielectric shell, the core–shell particle can turn under the action of a magnetic field, thus forming an oriented structure in the composite film. The dielectric properties of ZnFe₂O₄@BaTiO₃-P(VDF-HFP) composites were related to the anisotropy of ZnFe₂O₄@BaTiO₃. When the orientation of ZnFe₂O₄@BaTiO₃ is parallel to the electric field, the highest dielectric constant of the polymer composite with 80 vol% ZnFe₂O₄@BaTiO₃ reaches as high as 27.77 at 100 Hz, which is 28% higher than that of the non-oriented polymer and 113% higher than that of the pure polymer. when the filling ratio is 40 vol%, the energy storage density of ZnFe₂O₄@BaTiO₃-P(VDF-HFP) composites is 1.18 higher than that of non-oriented composites and 1.32 times higher than that of polymer matrix. This experiment proves that the magnetic core–shell particles can be oriented by the external magnetic field, and this orientation structure can improve the dielectric properties of the composite. [ABSTRACT FROM AUTHOR]