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Dielectric materials with superb thermal and electrical properties are highly desired for high-voltage electrical equipment and advanced electronics. Here, we propose a novel strategy to improve the performance of epoxy composites by employing boron nitride nanosheets (BNNSs) and γ-glycidyl ether oxypropyl sesimoxane (G-POSS) as functional fillers. The resultant ternary epoxy composites exhibit high electrical resistivity (1.63 × 1013 Ω·cm) and low dielectric loss (<0.01) due to the ultra-low dielectric constants of cage-structure of G-POSS. In addition, a high thermal conductivity of 0.3969 W·m−1·K−1 is achieved for the epoxy composites, which is 114.66% higher than that of pure epoxy resin. This can be attributed to the high aspect ratio and excellent thermally conductive characteristics of BNNSs, promoting phonon propagation in the composites. Moreover, the epoxy composite simultaneously possesses remarkable dynamic mechanical properties and thermal stability. It is believed that this work provides a universal strategy for designing and fabricating multifunctional composites using a combination of different functional fillers. [ABSTRACT FROM AUTHOR]

Dielectric materials with excellent thermal stability, mechanical properties, and thermal conductivity are highly desirable for advanced electronics and electrical equipment. However, it remains a significant challenge to develop a single material with these properties. Here we describe a new strategy to prepare dielectric paper by combining one-dimensional aramid nanofiber (ANF) with two-dimensional fluorinated graphene (F-graphene) through a vacuum-assisted filtration method. The obtained ANF/F-graphene paper exhibits a low dielectric constant of 1.92 at 103 Hz and its electrical breakdown strength is 17.6% higher than that of the neat ANF paper, owing to the presence of F-graphene, which significantly suppresses the accumulation of space charge in the prepared paper. Moreover, high mechanical strength (>200 MPa), thermal conductivity (6.29 Wm−1K−1), and thermal decomposition temperature (>500°C) are simultaneously achieved for the ANF/F-graphene paper. These findings highlight the fabrication of multifunctional dielectric materials and broaden their practical applications in the field of high-temperature electronics and devices. [ABSTRACT FROM AUTHOR]

The boom in high-power-density electronics and advanced pulsed power systems has led to a requirement for high-energy-density dielectric capacitors, for which the key enabler is the availability of dielectric materials with high energy densities and high efficiencies. Although antiferroelectric ceramics are promising dielectric materials with high energy densities, they have low efficiencies. In this study, we address this problem through the core–shell structure design. A phase-field model is developed by considering the core as antiferroelectric and the shell as linear dielectric, and the polarization hysteresis loops are determined. The results show that the polarization–electric field loop of the core–shell sample is slanted, with a delayed saturation polarization, decreased maximum polarization, and declined hysteresis loss compared with the pure sample. This phenomenon becomes more distinct with increasing shell fraction and decreasing shell permittivity, and vanished hysteresis is achieved in samples with a high shell fraction and a low shell permittivity. Through deconvolution, it is determined that the underlying mechanism of energy storage is the difference in the antiferroelectric polarization contribution of various shell parameters. It is found that a giant energy density of 15.5 J/cm3 and an ultrahigh efficiency of 99.7% at the saturation polarization can be achieved concurrently for a certain core–shell sample; these values considerably exceed the corresponding values (5.0 J/cm3 and 52.8%) for the pure sample. The findings of this study can serve as guidance for engineering core–shell structures, thus paving the way for enhancing the energy-storage performance of antiferroelectric ceramics. [ABSTRACT FROM AUTHOR]