Pressure‐Assisted Anisotropy in Carbon Nanofiber Films for Smart Electromagnetic Interference Shielding and Joule Heating

Intelligent electromagnetic interference (EMI) shielding materials with adjustable properties and performances are garnering significant attention due to the escalating complexity of application scenarios for electronic devices. Also, the trend of miniaturization is calling for lightweight and multifunctional materials. Here, the preparation of highly aligned carbon nanofiber film (a-CNFF) by electrospinning technology and a two-stage carbonization process is proposed, in which the pressurization strategy in the carbonization process promotes the development of highly aligned fiber network structures. The serialized anisotropic structures exhibit an impressive tunability in EMI shielding effectiveness (SE) adjustable from 23.0 to 35.6 dB for linearly polarized electromagnetic waves, and a superior specific SE value (SSE/t) of 34 000 dB cm² g^-1, with an EMI SE per unit thickness of 5791 dB cm^-1. Moreover, under a low load voltage of 1.6 V, the peak temperature of the film can be tuned within a wide range of 49.2-120.6 °C. These remarkable performances achieved by simply rotating the film demonstrate adjustable functionalities of the a-CNFF, providing guidelines in the applications of aerospace, military, microelectronics, and wearable devices.