Abstract
Highly dispersible nanospring single-walled carbon nanotubes (NS-CNTs) were incorporated in a P(VDF-TrFE) copolymer with up to 15 wt.% of nanofiller. The relative dielectric constant (K) of the polymer nanocomposite at 1 kHz was greatly enhanced from 12.7 to 62.5 at 11 wt.% of NS-CNTs, corresponding to a 492% increase over that of pristine P(VDF-TrFE) with only a small dielectric loss tangent (D) of 0.1. Based on two theoretical models, the Bruggeman equation and self-consistent effective medium theory (SC-EMT), experimental permittivity data for the P(VDF-TrFE) and NS-CNTs nanocomposites were simulated to estimate the dielectric constant of the NS-CNTs while changing both the shape of the nanofillers and the volume fraction of the interface when increasing the number of NS-CNTs in piled layers of P(VDF-TrFE). The number of NS-CNTs layers was counted from HR-TEM images to calculate the interfacial volume fraction, and used to infer the Eshelby tensor of the NS-CNTs in the SC-EMT model. The experimental dielectric constants of the composite films fit the Bruggeman equation and SC-EMT theory well for dielectric constants k=240–360, showing that the NS-CNTs nanofillers may be considered electrically semiconductive.
Highlights
Highly-dispersible buckled nanospring single-walled carbon nanotubes (NS-CNTs) 20–30 nm in diameter were successfully synthesized for the first time
As shown in high-resolution transmission electron microscope (HRTEM) images (Fig. 1a), the NS-CNTs produced resembled distorted hexagons closely related to the crystalline structure of the inner ZnO NPs template
In order to measure the dielectric constant of the P(VDF-TrFE) composite with varying buckled NS-CNTs content, 100-nm Au electrodes were deposited on the top and bottom by e-beam deposition
Summary
Kumar et al.[2] studied the electrical and dielectric properties of multi-walled PVDF-CNT composites prepared by solution-casting and melt-mixing They fabricated various concentrations of CNT composite films and measured their dielectric constant of 217 and loss value of 0.4 at 1 kHz. The inserted conducting linear or plate-shaped fillers had excellent dispersibility, and increased the dielectric constant in the polymer composite film. It has been claimed that the geometry of NS-CNTs fillers, compared to other nanocarbons, provide a highly unique structure to achieve high dispersibility and minimize the networking. For SC-EMT, the volume fraction of the interfacial region between fillers and the matrix and the electric field concentration factor, which depends on the geometry of the fillers, are taken into account Dielectric constant and the Eshelby tensor of the NS-CNTs fillers in this P(VDF-TrFE) composite are predicted
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