Dramatically improved dielectric properties of polymer composites by controlling the alignment of carbon nanotubes in matrix

Abstract

Aligned multi-walled carbon nanotubes (MWCNTs)/polyvinyl alcohol composite films were prepared by using an easy and controllable electrospinning-in situ film-forming (EF) technique. A high dielectric constant (k), a low dielectric loss, a consistently high breakdown strength, and a high energy density were obtained by using this technique. The dramatically improved dielectric properties are ascribed to the good dispersion and alignment of MWCNTs in the matrix, facilitating the formation of a large number of separated nano-capacitors (high k and low direct current (DC) conductance). For comparison purposes, the same composite films were prepared by solution casting (SC). At the same MWCNT content, the SC method yielded a higher k, but a significantly higher dielectric loss and much lower breakdown strength and energy density because of the random dispersion of MWCNTs in the matrix and the formation of a MWCNT network, which result in a large increase in DC conductance. The formation mechanism of the different microstructures and the relationships between the microstructures and dielectric properties are clarified. Our results indicate that high-performance MWCNTs/polymer dielectric composites can be obtained by controlling the microstructure of the composites by using the EF technique, which widens the applications of dielectric materials.

Simultaneously improved actuated performance and mechanical strength of silicone elastomer by reduced graphene oxide encapsulated silicon dioxide

“…Because of the curl and entanglement of CNTs with fibrous nanostructure, even quite a low content of CNTs can result in the formation of CNT network, thus leading to the large increase in k [19,20]. However, in this case, a high dielectric loss was also obtained owing to the high direct current (DC) conductance caused by the direct connection of CNTs [21].…”

Achieving significantly enhanced dielectric performance of reduced graphene oxide/polymer composite by covalent modification of graphene oxide surface

“…The fabrication of flexible dielectric films using polymers and electric conductive fillers has proven to be a promising strategy in producing films with advantageous dielectric properties [5][6][7][8][9][10][11][12].…”

One-Step Fabrication of Electrospun Photo-Cross-Linkable Polymer Nanofibers Incorporating Multiwall Carbon Nanotubes and Enzyme for Biosensing

“…Hydrogen bonding interactions between the hydroxyl groups present in PVA-SbQ and carboxylic groups present on the acid treated MWCNTs can also contribute to the reduction in PVA-SbQ/MWCNT-COOH NFs diameter and alignment by favoring MWCNT-COOHs dispersion into the PVA-SbQ solution. 37,[41][42][43] On the contrary, the formation of beads could not be avoided at the highest MWCNT-COOHs concentration tested and a large increase of AFD and size distribution (450 ± 100 nm) was observed (Fig. 2d), which could be the result of poor alignment of MWCNT-COOHs inside the fibers and the formation of nanotubes agglomerates.…”

“…Alignment of the nanotubes plays also an important role in the conductive properties of the NFs, as observed by several authors. 36,41 The electronic transfer properties of the bare, pure PVA-SbQ and PVA-SbQ/MWCNT-COOH modified gold electrodes were also characterized by EIS. The Nyquist plots were repetitively cycled until several consecutive plots were superimposed.…”