Co-manipulation of defects and porosity for enhancing the electrical insulation, microwave absorbing/shielding, and thermal properties of filter-paper-derived 2D interlinked carbon fiber networks

To develop light-weight polymer-based multifunctional materials with outstanding electromagnetic wave absorbing/shielding properties and high thermal conductivity, 2D interlinked carbon fiber networks (2D ICFNs) were synthesized via direct pyrolysis of filter papers at 600-900 degrees C. The pyrolysis temperature (Tp) was controlled to modulate the porosity, defects, and the resulting properties of 2D ICFNs. Owing to the co-manipulation of defects and porosity, the 2D ICFNs formed under Tp = 900 degrees C exhibit a larger EABWmax/ d (3.57 GHz/mm) and stronger absorption (-44.66 dB) at a lower load (15%) compared to most other carbon fiber (CF)-based materials. Their shielding effectiveness is beyond 20 dB over 2.0-18.0 GHz with a maximal value of 76.2 dB at 18 GHz, surpassing the minimum requirement (20 dB) for practical applications. Besides, the 2D ICFNs with moderate porosity and high graphitization bear a larger thermal conductivity (2.69-2.93 W/mK) at a lower filling ratio (20 wt%) in comparison to the majority of previously reported materials. This is primarily due to the shortened phonon/electron transfer paths, decreased phonon-interface/-defect scattering, and continuous paths for thermal transmission in the 2D ICFNs. Overall, it is believed that the 2D ICFNs can be one of the most promising multifunctional fillers for EM absorption applications.