Enhanced electrical/dielectrical properties of MWCNT@Fe3O4/polyimide flexible composite film aligned by magnetic field

Abstract

Magnetic carbon nanotube (marked as “MWCNT@Fe3O4”) has been prepared by depositing magnetic Fe3O4 on carbon nanotube. In order to align MWCNT@Fe3O4 in polyimide (PI) film, weak magnetic field by permanent magnet has been applied during the film curing process. The orientation mechanism of MWCNT@Fe3O4 between the magnetic carbon nanotubes and the PI film matrix has been theoretically studied. Experimental results showed that MWCNT@Fe3O4 was formed in a chain-like alignment in the PI film matrix by the magnetic field, which significantly improved the dielectric properties of composite films. The dielectric permittivity of parallel-aligned films (1.6 wt%) was increased from 5.5 to 52.75 at 58 Hz and percolation threshold of 1.6 wt% was almost 6 times that of the film in random alignment. The dielectric loss of the aligned films before reaching the percolation threshold was between 10–2 and 1. The magnetic alignment can greatly enhance the dielectric permittivity of composite films and suppress their dielectric loss. As for magnetic properties, the relationship between different arrangements and saturation magnetization is as follows: randomly aligned > parallel aligned. PI(//)-0.4wt% film shows the best tensile strength of 70 MPa, 5% elongation at break improvement, and 23% improvement in elastic modulus. This study provides an effective method to align MWCNT in PI film matrix, and the MWCNT@Fe3O4/PI composite film has a promising application prospect in flexible electronic devices.