RESUMO
Polyvinylidene fluoride (PVDF)-based dielectric energy storage materials have the advantages of environmental friendliness, high power density, high operating voltage, flexibility, and being light weight, and have enormous research value in the energy, aerospace, environmental protection, and medical fields. To investigate the magnetic field and the effect of high-entropy spinel ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4 nanofibers (NFs) on the structural, dielectric, and energy storage properties of PVDF-based polymers, (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4 NFs were prepared via the use of electrostatic spinning methods, and (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4/PVDF composite films were prepared via the use of the coating method. The effects of a 0.8 T parallel magnetic field, induced for 3 min, and the content of high-entropy spinel ferrite on the relevant electrical properties of the composite films are discussed. The experimental results show that, structurally, the magnetic field treatment causes the originally agglomerated nanofibers in the PVDF polymer matrix to form a linear fiber chain with different fiber chains parallel to each other along the magnetic field direction. Electrically, the introduction of the magnetic field enhanced the interfacial polarization, and the (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4/PVDF composite film with a doping concentration of 10 vol% had a maximum dielectric constant of 13.9, as well as a low energy loss of 0.068. The high-entropy spinel ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4 NFs and the magnetic field influenced the phase composition of the PVDF-based polymer. The α-phase and γ-phase of the cohybrid-phase B1 vol% composite films had a maximum discharge energy density of 4.85 J/cm3 and a charge/discharge efficiency of 43%.
RESUMO
Energy depletion is one of the significant threats to global development. To increase the usability of clean energy, the energy storage performance of dielectric materials must be urgently enhanced. Semicrystalline ferroelectric polymer (PVDF) is the most promising candidate for the next generation of flexible dielectric materials thanks to its relatively high energy storage density. In this work, high-entropy spinel ferrite (La0.14Ce0.14Mn0.14Zr0.14Cu0.14Ca0.14Ni0.14Fe2O4) nanofibers (abbreviated 7FO NFs) were prepared by the sol-gel and electrostatic spinning methods, then blended with PVDF to prepare composite films using the coating method. A magnetic field was used to control the orientation distribution of the high-entropy spinel nanofibers in the PVDF matrix. We investigated the effects of the applied magnetic field and the content of high-entropy spinel ferrite on the structure, dielectric, and energy storage properties of the PVDF substrate films. The 3 vol% 7FO/PVDF film treated in a 0.8 T magnetic field for 3 min exhibited a good overall performance. The maximum discharge energy density was 6.23 J/cm3 at 275 kV/mm and the efficiency was 58% with 51% ß-phase content. In addition, the dielectric constant and dielectric loss were 13.3 and 0.035, respectively, at a frequency of 1 kHz.
RESUMO
Manipulating the light scattering direction and enhancing directivity are important research areas in integrated nanophotonic devices. Herein, a novel, to the best of our knowledge, nanoantenna composed of hollow silicon nanoblocks is designed to allow directional emission manipulation. In this device, forward scattering is enhanced and backward scattering is restrained substantially in the visible region. Owing to electric dipole resonance and magnetic dipole resonance in this nanoantenna, Kerker's type conditions are satisfied, and the directionality of forward scattering GFB reaches 44.6 dB, indicating good characteristics in manipulating the light scattering direction.
