Ferromagnetic Quantum Dots Improving Polypropylene Film Performance in Strong Electromagnetic Field

In this article, the performance degradation of polypropylene (PP) films is investigated in a 0–12-T magnetic field. A modification method is proposed based on ferromagnetic quantum dots (QDs) blending. The experimental results show that the 12-T magnetic field reduces the relative permittivity by 0.07 at 1 kHz. The conductivity of PP films increases by 230% and the breakdown strength decreases by 16.8% under 12 T. After blending 20-nm Fe3O4 particles, the conductivity of the composite films is reduced by 70% under 0 T and 64.6% under 12 T. The withstand voltage increases by 13% under 0 T and 24% under 12 T. The energy density of the 0.2 wt% blending composite films increases from 2.07 to 3.12 J/cm3 under 12 T. Further analysis shows that the magnetic field leads to the film performance degradation by restraining polarization and exciting electrons. Doping Fe3O4 nanoparticles can slightly enhance polarization with the introduction of the interface and capture electrons to improve the electric resistance and the breakdown strength. This article is of significance to the performance optimization of PP dielectric for power capacitors in an electromagnetic environment.