Investigation On Three-phase Composite And Surface Modification Of High Dielectric Polymer-based Materials

In order to improve the dielectric constant of polymer materials，the traditional modification method was to fillin high dielectric constant ceramic particles or conductive particles. However, both of these methods had theiradvantages and disadvantages. To improve the dielectric constant of polymer materials obviously, the ceramicparticles should be over50vol%. Although, the dielectric loss was low, it has definitely broken down the flexibilityof the matrix. On the other hand, though the addition of conductive fillers would improve the dielectric constantremarkably when the volume fraction of fillers was around the percolation threshold, the dielectric loss was high.Therefore, in recent years, researchers have tried to fill in both ceramic particles and conductive particles intopolymer matrix, in order to prepare the three-phase composites to improve the dielectric properties of polymermaterials by taking advantage of each component. At the same time, the conglomeration of conductive particleshas limited the promotion of polymer, and the surface modification of conductive fillers could improve thecompatibility and dispersibility between fillers and matrix. Therefore, filling the modified fillers into matrix wasalso an effective method to improve the dielectric properties of polymer materials.In this article, we choosed PVDF as matrix, Fe3O4and Ni as conductive fillers and BaTiO3as ceramic filler toresearch the dielectric properties of three-phase composites. We also have researched the dielectric properties ofNi/PVDF composites after the surface treatment of Ni nanoparticles.Results showed that, in Fe3O4/BaTiO3/PVDF three-phase composites, the dielectric constant was as1.8timeshigh as that of Fe3O4/PVDF composites, when Fe3O4was20vol%and BaTiO3was8vol%. In Ni/BaTiO3/PVDFcomposites, With the increased volume fraction of BaTiO3, the conductivity and dielectric constant of thecomposite materials have climbed up and then declined. The dielectric constant of oleic acid modified Ni/PVDFcomposites and KH550modified Ni/PVDF composites was as60and90times as that of unmodified Ni/PVDFcomposites when the volume fraction of Ni was close to the percolation threshold.