Abstract
This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.
Highlights
With the miniaturization and multifunctionality of electronic device used in high charge-storage capacitors and high-speed integrated circuits, polymeric nanocomposites with high dielectric permittivity and low dielectric loss are needed.[1,2,3,4,5,6] The composites with high dielectric permittivity of great scientific and engineering importance are percolative dielectric composites
A low dielectric loss is preferred in order to reduce the energy loss from a dielectric material, for high frequency applications.[21]
Yao studied the percolation threshold of multi-walled carbon nanotube (MWNT)/ferroelectric polyvinylidene fluoride nanocomposites with four types of MWNT at different aspect ratios and found that the value of aspect ratio played a crucial role in determining the percolation threshold of nanocomposites.[20]
Summary
With the miniaturization and multifunctionality of electronic device used in high charge-storage capacitors and high-speed integrated circuits, polymeric nanocomposites with high dielectric permittivity and low dielectric loss are needed.[1,2,3,4,5,6] The composites with high dielectric permittivity ( known as high-k) of great scientific and engineering importance are percolative dielectric composites. Most of the previous researches on CCTO have been focused on bulk ceramic, thin film, and powders, and there are rarely literatures on CCTO fibers with high aspect ratio.[31] The large aspect ratio of CCTO nanofibers could have substantial effect on the dielectric properties of the composites reinforced by them and reduce the percolation threshold while retaining the flexibility.
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