Assembly of PAN/Gr@MWCNTs/CoFe2O4 multilayer composite films for high-efficiency electromagnetic shielding and Joule heating

Creating novel, high-efficiency and multi-functional electromagnetic interference (EMI) shielding materials with high absorption attenuation is crucially important for integrated electronic devices. Herein, heterogeneous polyacrylonitrile (PAN)/graphene (Gr)@multi-walled carbon nanotubes (MWCNTs)/CoFe₂O₄ multilayer films featuring electric-magnetic coupling were fabricated through a facile vacuum filtration method. The asymmetric layered architecture was composed of a flexible PAN electrospun nanofiber mat, an electrically conductive hybrid of Gr@MWCNTs, and a layer of insulating CoFe₂O₄ particles. The nanosized magnetic CoFe₂O₄ particles with unique magnetic hysteresis loss and natural resonance were synthesized by hydrothermal method and deposited on the conductive layer, to improve the impedance matching and reduce the electromagnetic wave (EMW) reflection. As a consequence, after incorporating the CoFe₂O₄ layer, the EMW absorption loss (SE_A) was improved from 21.7 to 25.7 dB. Furthermore, the hybrid conductive network was regulated by altering the ratio of two-dimensional (2D) Gr to one-dimensional (1D) MWCNTs, to endow the well-designed multilayer films with a high EMI shielding effectiveness (SE) of 40.1 dB and a superior specific shielding effectiveness (SSE) of 326.3 dB/mm. By virtue of the fine-tuned Gr@MWCNTs conductive network, the PAN/Gr@MWCNTs/CoFe₂O₄ multilayer films exhibited excellent Joule heating performance, with high sensitivity, low driving voltage, rapid response, superior cycling stability and long-term durability. The multilayer films could be controllably heated to 114.1 °C within 5 s under a low input voltage of 3.00 V. This work presents a viable strategy for exploiting functional materials that exhibit excellent EMI shielding and thermal management performance, suitable for applications in electronics operating at extremely low temperatures.