Unique hybridized graphene and its high dielectric constant composites with enhanced frequency stability, low dielectric loss and percolation threshold

A novel hybrid (TiO2@TiB2-rGO) with microcapacitor structure was synthesized by chemically decorating core-shell titanium dioxide@titanium diboride (TiO2@TiB2) on reduced graphene oxide (rGO). By adjusting the weight ratio of TiO2@TiB2 to rGO, a series of TiO2@TiB2-rGO hybrids with different morphologies are obtained. When the loading of rGO is fixed at 0.75 wt.%, the TiO2@TiB2-0.75rGO hybrids with different weight ratios of TiO2@TiB2 to rGO were used to prepare TiO2@TiB2-0.75rGO/epoxy (EP) composites, which have much higher and stable dielectric constant as well as lower dielectric loss than 0.75rGO/EP composite. When the weight ratio of TiO2@TiB2 to rGO is 0.1:1, the dielectric constant and loss at 100 Hz of the TiO2@TiB2-0.75rGO/EP composite are about 1.14 and 5.8 × 10−2 times of those of 0.75rGO/EP composite, respectively. Besides, TiO2@TiB2-0.75rGO/EP composites have much lower percolation threshold than most rGO/polymer composites reported. These results are attributed to the unique structure of TiO2@TiB2-rGO hybrids. The TiO2@TiB2 coating blocks the contact among rGO sheets; moreover, the core-shell structure of TiO2@TiB2 on rGO allows the construction of a large number of microcapacitors and suppresses the leakage current by isolating the rGO sheets in the EP matrix, resulting in excellent dielectric properties. The statement is also supported by different equivalent circuits.