Improving electromagnetic engineering of thermal conductive composites by establishing continuous thermal conductive networks with gradient impedance

Driven by the increasing integration and higher power requirements of electronics, polymer-based composites with high-performance in terms of thermal conductivity (TC) and electromagnetic (EM) wave absorption have become an important issue. Herein, multi-layer boron nitride-carbon nanotube/carboxymethyl cellulose/polydimethylsiloxane (BN–CNT/CMC/PDMS) composites with enhanced interface interactions and continuous thermal pathways with gradient impedance were manufactured through a strategy involving chemical surface modification, directional freeze casting, freeze drying and matrix infiltration. Benefiting from the covalent bonding effect between fillers as well as the consecutive thermal conductive pathways, the obtained composites achieved a maximum through-plane TC of 3.56 W m K−1 at a filler content of only 8 wt%. Meanwhile, the composites also achieved an ultra-wide effective electromagnetic wave absorption bandwidth (EMB) of 13.45 GHz, which was attributed to the precisely controllable electromagnetic parameters and the gradient impedance structures. Therefore, these results fully indicate that the composites have great application potential as packaging materials for advanced electronics.