Abstract
With the increasing application of barium titanate (BaTiO3) in polyvinylidene fluoride (PVDF), the evaluation of its dielectric properties has attracted the attention of many frontier scholars. In this paper, from the theoretical point of view, the effects of the aspect ratio and the concentrations of BaTiO3 nanowires on macroscopic dielectric properties were studied by the finite element method. Depending on the calculation results, some conclusions had been obtained: First, it was found that the effect of higher aspect ratios of nanowires on the effective permittivity of the composites was not significant when the aspect ratio of the nanowire filler exceeded 20. Second, when the permittivity of the BaTiO3 nanowires reaches about 3000, as the permittivity of the filler increases, the rate of change of the effective permittivity of the composite material gradually slows down, which indicates that nanowires with higher permittivity have little influence on the effective permittivity of the composites. Finally, by comparing with permittivity data of BT/PVDF composites in the literature, it was found that the simulation results have good consistency with the experimentally measured values. The above-mentioned results have shown that the composite may exhibit good dielectric properties at a low concentration (<30 vol. %) and low permittivity filler. Moreover, the electrostatic field can roughly represent the electric field of a low-concentration composite under a certain electric field strength.
Highlights
INTRODUCTIONEffective permittivity is an essential indicator of their macroscopic characterization and critical parameters for evaluating their dielectric properties. In insulation systems, effective permittivity is expected to be smaller to reduce leakage capacitance dissipation
In composite materials, effective permittivity is an essential indicator of their macroscopic characterization and critical parameters for evaluating their dielectric properties.1,2 In insulation systems, effective permittivity is expected to be smaller to reduce leakage capacitance dissipation
The simulation results are in good agreement with the experimental results. This result demonstrates the validity of the model and indicates that when the nanowire volume concentration is lower than 30 vol %, the electric field distribution in the heterogeneous composite can be approximated by the electrostatic field, which is of great significance for further analysis of the dielectric properties at the microscopic level
Summary
Effective permittivity is an essential indicator of their macroscopic characterization and critical parameters for evaluating their dielectric properties. In insulation systems, effective permittivity is expected to be smaller to reduce leakage capacitance dissipation. Wang et al proved that linear fillers improve the dielectric properties and energy storage density of the composite by preparing a low-concentration of BaTiO3 nanowire/polyimide composite material. Studying the microscopic mechanism of the macro-dielectric behaviors of the composite is of great significance for improving the accuracy of the experiment. It can avoid unreasonable research problems, such as the endless pursuit of high-permittivity fillers to achieve high energy storage density. A three-dimensional model of BT-NW randomly distributed in the PVDF polymer matrix was built to approximate the actual composite, and the relationship between the internal electric field distribution and dielectric properties was thoroughly studied. The simulation results of the effective permittivity of the polymer were compared with the experimental measurements
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