▎ 摘　　要

With the rapid development of information technology, the conductive switching materials induced by voltage are highly desired to protect the electronic devices from surge voltage and electrostatic discharge. Polymeric composites filled with conductive or semiconductive fillers with high nonlinear I-V characteristics can be used for the overvoltage protection. In this study, the graphene nanoplatelets (GNPs) were processed by two methods (TEC1 and TEC2) and embedded in an epoxy resin (ER) to prepare composites. In the TEC1, the graphene oxide (GO) was firstly reduced for improving conductivity and modified by coupling agent later. On the contrary, the GO was modified before reduction in the TEC2, which focused on improving the compatibility and dispersivity of fillers with the matrix. The microstructure analysis and conductive characteristic measurements of the GNPs/ER composites obtained by TEC1 and TEC2 exhibited obvious nonlinear I-V behavior under certain applied voltage range with a high nonlinear coefficient. The switching threshold voltage and nonlinear coefficients could be adjusted by changing the filling concentration of the filler. Moreover, the conductive mechanism of the nonlinear I-V behavior was discussed, which verified that the GNPs/ER composites obtained by TEC2 was more suitable for the actual need of overvoltage protection because of their stable nonlinear I-V characteristics.