Polyimide Derived Carbon/Graphene Hybrid Aerogel Microspheres for Strong and Wide Bandwidth Microwave Absorption
Yifan Cai, Zhanhua Wang, Guoxia Fei, Marino Lavorgna, Hesheng Xia
Abstract
Abstract Graphene‐based aerogel microspheres (GAMs) are effective electromagnetic wave (EMW) absorbers due to their excellent impedance matching and high loss capabilities. The main challenge in the development of GAMs is to improve their dielectric loss and also the mechanical strengthto meet practical application requirements. Herein, the polyimide derived carbon/graphene hybrid aerogel microspheres (PI∼NC‐GAMs) are prepared by high‐pressure spraying, freeze shaping, freeze drying, in‐situ thermal reduction and imidization, and high temperature pyrolysis. Due to the reinforcing and supporting effect of the PI‐derived carbon layer, the prepared ultralight hybrid PI∼NC‐GAMs with a low packing density have a good compressive strength, ≈10.67 kPa at a compressive strain of 40%, far better than the blank reduced graphene oxide aerogel microspheres (rGOAMs). PI~NC‐GAMs could be an effective candidate for ultralight and high‐efficiency EMW absorbers, showing a minimal reflection loss (RL) of ‐63.6 dB at 9.16 GHz with 1 wt% filler loading at 3.43 mm thickness and exhibiting a maximum effective absorption band (EAB) of 7.45 GHz (10.55‐18 GHz) at 2.57 mm thickness.The highly efficient EMW absorption performance for PI∼NC‐GAMs originates from the hierarchical porous structures caused multiple scatterings and impedance match, the better dipolar/interfacial polarizations, and the enhanced electrical conductivity of the hybrid aerogel microspheres.