Modulating topological structure of carbon nanotube/cyanate ester-boron nitride/cyanate ester multi-layered composites for enhancing dielectric properties, breakdown strength and energy density

Constructing multi-layered structures based on insulating layers and conductor/polymer composites is proved to be an effective strategy of preparing high dielectric constant conductor/polymer composites with suppressed dielectric loss, high breakdown strength and high energy density; however, up-to-date, researches are mainly focused on three-layer structures, the influence of the layer number on dielectric properties, breakdown strength and energy density of multi-layered composites has not been clearly elaborated yet. Starting from a typical three-layer structure composite (CBC) with outstanding integrated performance using carbon nanotube (CNT)/cyanate ester resin (CE) and hexagonal boron nitride (BN)/CE composites as C layer and B layer, respectively, new four-layer structure (CBCB) and five-layer structure (CBCBC and BCBCB) composites were fabricated to reveal the role and mechanism of layer number and BN content, consequently finding a new technique to get multi-layered composites with better integrated performances. Results show that when the content of BN in B layer is 20 wt%, the five-layer structure composite (CBC20BC) achieves the highest energy density, about 6264% higher than that of 0.4CNT/CE, this improvement of energy density is the maximum value among all multi-layered composites based on conductor/polymer layer reported so far. In addition, the dielectric constant of CBC20BC composite is as high as 352 (100 Hz), and the breakdown strength of CBC20BC composite is 1.4 times of that of CBC composite. The mechanism behind these excellent integrated performances is that the increase in layer number not only enhances the interfacial polarization, but also extends the length and tortuosity of breakdown path.