The effects of multiwall carbon nanotubes on the electrical characteristics of ZnO-based composites

AbstractIn this experimental work, the effects of multiwall carbon nanotubes (MWCNTs) on electrical characteristics of zinc oxide–MWCNT–high-density polyethylene composite varistors have been investigated. All the samples were made at the temperature of 130 °C and pressure of 60 MPa by the hot-press method. Results show that increasing zinc oxide content in the mixture increases breakdown voltage up to 170 V, where the highest nonlinear coefficient (α ~ 13) corresponds to the samples with 95 wt% of ZnO. Results with regard to the effects of MWCNT as an additive reveal that increasing its content from 1 to 2.5% in the composites, the breakdown voltage decreases to 50 V, but the highest nonlinear coefficient (~ 14) corresponds to the sample with 1.5% of MWCNT content. It is also revealed that, heat treatment of the sample at a constant temperature of 135 °C and different time intervals from 2 to 10 h, the sample with 6 h annealing time shows maximum breakdown voltages (Vb = 140 V) with the highest nonlinear coefficient (~ 14). Investigation of the potential barrier height of samples shows a complete consistency with the breakdown voltage variations. The results have been justified regarding XRD patterns and SEM micrographs of samples.