Fabrication and enhanced dielectric properties of polyimide matrix composites with core-shell structured CaCu_3Ti_4O_(12)@TiO_2 nanofibers

摘要

Core–shell structured CaCu~(3)Ti~(4)O~(12)@TiO~(2)(CCTO@TiO~(2)) nanofibers were prepared via a normal coaxial electrospinning technique with sol precursors. Polyimide (PI) nanocomposite films containing the core–shell structured CCTO@TiO~(2)nanofibers were fabricated by the solution casting method. The core–shell structure of the CCTO@TiO~(2)nanofibers was confirmed through transmission electron microscope. The percolation of the CCTO/TiO~(2)interfaces leads to much enhanced interfacial polarization of the CCTO@TiO~(2)nanofibers, which gives rise to substantially increased dielectric constant of the nanocomposites. Compared to the nanocomposites with CCTO nanofibers, the breakdown strength of the nanocomposites with CCTO@TiO~(2)nanofibers is also increased due to the charge shifting is limited to the interfacial zone of CCTO/TiO~(2)interfaces, instead of in the PI matrix to form a percolation path. For the nanocomposites with 5 vol% nanofibers, the dielectric constant of 5.55 was enhanced to 5.85 and the breakdown strength of 201 kV/mm was increased to 236 kV/mm by utilizing the TiO~(2)coated CCTO nanofibers, while the dielectric loss shows no obvious change. Meanwhile, the PI nanocomposite film filled with 1 vol% CCTO@TiO~(2)nanofibers exhibits a maximal energy density of 1.6 J/cm_(3). The core–shell structured nanofibers open up an effective way to optimize the dielectric properties of polymer nanocomposites with high energy density.