Mechanically Insulated Graphene/Polymer Nanocomposites with Improved Dielectric Performance and Energy Storage Capacity

Graphene nanoplatelets (GNPs) were mechanically insulated with titanium dioxide (TD) nanopowder to address challenges of high dielectric loss and low breakdown strength associated with polymer/graphene nanocomposites. GNPs were functionalized (fGNPs) and TD was hydroxylated (TD-OH) to ensure wettability of the co-particles and well dispersion in polymer matrix. The composite samples were developed by solution blending and melting compounding processes. Successful modification of the co-particles and insulation of fGNPs were examined using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). Energy storage capacity, dielectric and electrical properties of the composites were investigated. Insulated fGNPs composites showed significant improvement in energy storage capacity and reduction in dielectric loss with addition of 10 wt % TD-OH compared to bared fGNPs composites. About 92.6% reduction in dielectric loss and 77% increase in energy storage density were recorded for 6.67 wt % fGNPs/10 wt % TD-OH composite compared to 6.67 wt % fGNPs composite at 100Hz. This was due to excellent insulating property of TD-OH on fGNPs. Although dielectric loss was further reduced on addition of 20 wt % TD-OH into fGNPs composites, their dielectric constant and energy storage density were slightly reduced compared to composites containing 10 wt % TD-OH. This study revealed that mechanical insulation of graphene with ceramic nanopowder can suppress energy dissipation associated with polymer/graphene nanocomposites with improve energy storage capacity.