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Field-grading polymer nanocomposites have drawn significant attention in high voltage electrical industries due to their excellent nonlinear conductive or dielectric properties. But composites with both nonlinear properties are rarely reported, and desirable nonlinear performance associated with excess fillers in the composite is at the expense of electric breakdown strength. In this work, BaTiO 3 nanoparticles were decorated successively using double-shell layers of TiO 2 and polydopamine, which are developed as novel nanofillers (BT@TiO 2 @PDA) for field-grading applications. Subsequently, BNNSs were prepared by liquid phase exfoliation, serving as the inhibitor of breakdown phase growth in the composites. Finally, novel epoxy nanocomposites (EP/BT@TiO 2 @PDA-OB) with BT@TiO 2 @PDA and oriented BNNSs were fabricated by a simple hot-pressing method. Results show that the hierarchically designed nanoparticles can make the composites possess not only nonlinear dielectric properties due to high ε r of BT and improved interfacial polarization, but also nonlinear conductive properties resulted from the organic semiconductor PDA shell. Nonlinear effective medium theory (EMT) was utilized to explain the nonlinear dielectric properties, and the hopping transport model considering Pool-Frenkel effect was applied to explain the nonlinear conductive properties. In addition, electric breakdown tests reveal that EP/BT@TiO 2 @PDA-OB has significantly enhanced breakdown strength (45.7 kV/mm) as compared to that of pristine epoxy resin (29.4 kV/mm) and EP/BT@TiO 2 @PDA-RB (randomly dispersed BNNSs, 36.2 kV/mm). It is expected that these results can open new avenues for the design of novel composites with both nonlinear conductive properties and dielectric properties as well as high breakdown strength. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymeric materials doped with SiC particles can exhibit promising nonlinear properties that can be widely used in electrical field grading applications. However, excellent field-grading performance is at the expense of mechanical characteristics due to excess fillers in the composites. Therefore, how to realize synergistic optimization of electrical and mechanical performances in ultra-low SiC loading is urgent for practical applications. In this study, we report a novel strategy to achieve comprehensive enhancement of thermal, mechanical and electrical properties of epoxy composites with self-assembly surface-modified SiC particles on cellulose aerogel scaffolds. The composites exhibit excellent nonlinear electrical properties at a low SiC loading of 4.47 vol%, and introducing different volume fractions of SiC into cellulose aerogel supported epoxy composites can largely broaden the range of switching field. Meanwhile, the dynamic mechanical test reveals that the storage modulus and crosslinking density of the composites are markedly enhanced due to 3D interconnected structure, while the thermal conductivity of this composite is also notably improved by about 300%. This method provides a novel idea for electric field grading composites with concurrent reinforcement performances in potential applications. [Display omitted] [ABSTRACT FROM AUTHOR]