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.

磁性碳纳米管（标记为“ MWCNT @ Fe ₃ O ₄ ”）已经通过在磁性碳纳米管上沉积磁性Fe ₃ O ₄来制备。为了使聚酰亚胺（PI）膜中的MWCNT @ Fe ₃ O ₄对准，在膜固化过程中施加了永磁体产生的弱磁场。从理论上研究了磁性碳纳米管与PI膜基体之间MWCNT @ Fe ₃ O ₄的取向机理。实验结果表明，MWCNT @ Fe ₃ O ₄通过磁场在PI膜基质中形成链状排列的Sn，大大改善了复合膜的介电性能。平行取向膜的介电常数（1.6 wt％）在58 Hz时从5.5增加到52.75，渗透阈值1.6 wt％几乎是随机取向膜的6倍。达到渗滤阈值之前，取向膜的介电损耗在10 ^–2之间 1.磁取向可以大大提高复合膜的介电常数并抑制其介电损耗。至于磁性能，不同排列与饱和磁化强度之间的关系如下：随机排列>平行排列。PI（//）-0.4wt％的薄膜显示出70 MPa的最佳拉伸强度，断裂伸长率提高5％，弹性模量提高23％。本研究提供了一种在PI薄膜基体中对准MWCNT的有效方法，MWCNT @ Fe ₃ O ₄ / PI复合膜在柔性电子器件中具有广阔的应用前景。