Unique Li0.3Ti0.02Ni0.68O-carbon nanotube hybrids: Synthesis and their epoxy resin composites with remarkably higher dielectric constant and lower dielectric loss

Abstract

Developing high-k (high dielectric constant) composites with simultaneously lower dielectric loss is an important subject of functional materials for actual cutting-edge applications. Novel hybrid (coded as LTNO–CNT) was synthesized by grafting nano-scale Li and Ti doped NiO (Li0.3Ti0.02Ni0.68O, LTNO) onto the surface of carboxylated carbon nanotube (aCNT). The LTNO–CNT hybrids with different ratios of aCNT to LTNO were embedded in epoxy (EP) resin to prepare composites (LTNO–CNT/EP) with greatly increased dielectric constant and decreased dielectric loss. With the same loading of aCNTs (0.5wt%), when the ratio of aCNT to LTNO was 1:1, the dielectric constant and loss at 100Hz of the (LTNO–CNT)0.5/EP composite were 1.4 and 0.015 times the corresponding values of aCNT0.5/EP composite, respectively. While the dielectric constant and loss at 100Hz of the composite with simple blends of LTNOs and aCNTs (LTNO/CNT0.5/EP) were severally about 0.36 and 0.12 times the values of the aCNT0.5/EP composite, meaning that the dielectric behavior of the LTNO–CNT/EP composite is not a simple additive property of those of LTNO/EP and aCNT/EP composites. This result is attributed to the special structure of the LTNO–CNT. Specifically, different from aCNTs, the LTNO–CNT hybrids have good dispersion in resin, forming many micro-capacitors, and thus leading to remarkably high dielectric constant. Meanwhile, LTNOs on the surfaces of aCNTs reduce the direct contact of aCNTs, resulting in greatly reduced dielectric loss. The aCNT/EP and LTNO–CNT/EP composites have different equivalent circuits, proving that the composites have different structures and thus significantly different dielectric behaviors.