Large Dielectric Constant and High Thermal Conductivity in Poly(vinylidene fluoride)/Barium Titanate/Silicon Carbide Three-Phase Nanocomposites

Dielectric polymer composites with high dielectric constants and high thermal conductivity have many potential applications in modern electronic and electrical industry. In this study, three-phase composites comprising poly(vinylidene fluoride) (PVDF), barium titanate (BT) nanoparticles, and beta-silicon carbide (beta-SiC) whiskers were prepared. The superiority of this method is that, when compared with the two-phase PVDF/BT composites, three-phase composites not only show significantly increased dielectric constants but also have higher thermal conductivity. Our results show that the addition of 17.5 vol % beta-SiC whiskers increases the dielectric constants of PVDF/BT nanocomposites from 39 to 325 at 1000 Hz, while the addition of 20.0 vol % beta-SiC whiskers increases the thermal conductivity of PVDF/BT nanocomposites from 1.05 to 1.68 W m(-1) K-1 at 25 degrees C. PVDF/beta-SiC composites were also prepared for comparative research. It was found that PVDF/BT/beta-SiC composites show much higher dielectric constants in comparison with the PVDF/beta-SiC composites within 17.5 vol % beta-SiC. The PVDF/beta-SiC composites show dielectric constants comparable to those of the three-phase composites only when the beta-SiC volume fraction is 20.0%, whereas the dielectric loss of the PVDF/beta-SiC composites was much higher than that of the three-phase composites. The frequency dependence of the dielectric property for the composites was investigated by using broad-band (10(-2)-10(6) Hz) dielectric spectroscopy.