ZnO-Decorated Carbon Nanotube Hybrids as Fillers Leading to Reversible Nonlinear I–V Behavior of Polymer Composites for Device Protection

Overvoltage protection is becoming increasingly important because of miniaturization and multifunctionality of electronic devices. Flexible, easily processable materials with nonlinear and reversible I–V behavior are highly desired. In this study, hybrid nanoparticles of ZnO-decorated carbon nanotubes (CNT–ZnO) were synthesized via a sol–gel hydrothermal process employed in an epoxy matrix to prepare composites. Microstructure analysis demonstrated that ZnO nanoparticles were well-bonded to the surface of CNT. The CNT–ZnO/epoxy composites exhibited nonlinear I–V behavior under increasingly applied voltage with a nonlinear coefficient of 5.01 (10 wt % filler loading). More importantly, the composites possessed excellent reversibility from dielectric to conductor and vise versa in the recycling of increase and decrease of applied electric field, in contrast to the poor recoverability of pure CNT-filled epoxy. The mechanism of the nonlinear I–V behavior and reversibility was investigated and discussed. A simple circuit was fabricated, which verified well the protection function of the CNT–ZnO/polymer composites.