Lightweight, multifunctional MXene/polymer composites with enhanced electromagnetic wave absorption and high-performance thermal conductivity

Abstract

Polymer composites receive attentions for protecting from electromagnetic (EM) pollution. However, their EM wave (EMW) attenuation mechanism primarily results from reflection rather than absorption. Herein, we prepared poly(vinylidene fluoride)/cobalt (Co)/MXene composite foams that exhibited applicable impedance matching, enhanced EMW absorption and high-performance thermal conduction properties. With CO2-assisted foaming, a uniform foam structure was integrated into the polymer composites, and meanwhile, the introduced MXenes were partially oxidized and transformed into TiO2 and amorphous carbon. The formed TiO2 not only provided extra heterogeneous interfaces and capacitor-like structures in favor of dielectric polarization but also reduced the excessive electrical conductivity of the pristine MXenes to favor impedance matching. Accordingly, the EMW absorbing performance of the composite foam was enhanced with a minimum reflection loss of −45.6 dB at 4 mm when the filler content was only 12 wt% (6 wt% MXene and 6 wt% Co). Additionally, the synergism between the foam structure and TiO2 nanocrystals resulted in improved thermal conductivity, ranging from 1.28 W/(m·K) to 1.36 W/(m·K), which were 2–6 times higher than that in the solid composite films. This study provided new insights into the simultaneously enhanced EMW absorption and dissipating heat ability in polymer composite foams with a low percolation threshold.