Electrical-Field Induced Nonlinear Conductive Characteristics of Polymer Composites Containing SiO2-Decorated Silver Nanowire Hybrids

Nonlinear Conductive Characteristics of ZnO-Coated Graphene Nanoplatelets-Carbon Nanotubes/Epoxy Resin Composites

With the increasing threats arising from the electromagnetic environment, polymeric composites which could exhibit nonlinear conductive characteristics are highly required in the protection of electronic devices against overvoltage. In this research, ZnO nanoparticles are coated onto graphene nanoplatelets (GNPs)-carbon nanotubes (CNTs) hybrid, and then it is embedded in epoxy resin (ER) matrix via solution blending. Based on the characterization results, CNTs are well dispersed across the GNPs which prevent the restacking of GNPs and CNTs. At the same time, ZnO nanoparticles are well-bonded to the surfaces of GNPs-CNTs hybrid. During repeated conductive characteristic measurements, GNPs-CNTs-ZnO/ER composite is able to demonstrate distinctly reversible nonlinear conductive behavior, with high nonlinear coefficients. Especially, the filler content in GNPs-CNTs-ZnO/ER composite is only 12.5% of that in GNPs-ZnO/ER composite reported in our previous work. Moreover, it is shown that the nonlinear coefficients and switching threshold voltage can be modified by controlling the weight ratios of GNPs, CNTs, and ZnO. Finally, the samples with 1:1 weight ratio of GO to MWCNTs (A-6.67 and A-10) exhibit the best reversible nonlinear conductive behavior.

Reversible Nonlinear I-V Behavior of ZnO-Decorated Graphene Nanoplatelets/Epoxy Resin Composites

With the more serious threats from complex electromagnetic environments, composites composed of conductive or semiconductive fillers and polymeric matrices could exhibit excellent nonlinear I-V characteristics, and have drawn significant attention in the field of overvoltage protection. In this research, graphene nanoplatelets (GNPs) are decorated by ZnO and mixed into an epoxy resin (ER) matrix via solution blending to prepare composites. A characterization analysis and the I-V measurement results of the GNPs/ER composites indicate that ZnO nanoparticles are well bonded with GNPs and exhibit obvious nonlinear I-V behavior under proper applied voltage with high nonlinear coefficients. The switching threshold voltage and nonlinear coefficients could be controlled by adjusting the weight ratio of GNPs and ZnO of the filler. Moreover, compared with the poor recoverability of pure GNP-filled ER in previous research, the GNP-ZnO/ER composites exhibited excellent reversibility of nonlinear I-V behavior under multiple repetitive I-V measurements. And compared with different composites, the sample with a 1:8 weight ratio of GO to Zn(Ac)₂ presents the smallest variation of switching threshold voltage at 158 V, with a standard deviation of 1.27% from among 20 measurements, which indicates the best reversibility. Finally, the conducting mechanism of the reversible nonlinear I-V characteristic is investigated and analyzed.