Optimizing impedance matching and interfacial characteristics of aromatic polyimide/graphene by molecular layer deposition for heat-conducting microwave absorption

Heat-conduction microwave absorbers with outstanding electromagnetic wave (EMW)-absorption and thermal-management performances are considerably attractive in the field of modern electronic devices. Herein, by uniformly depositing aromatic polyimide (PI) on the surface of graphene through a molecular layer deposition (MLD) method and tuning the number of deposition cycles, PI/graphene (PI/G) composites with excellent microwave-absorption and thermal-management properties were successfully fabricated. The as-prepared sample displayed a high-efficiency reflection loss (RL) of -57.16 dB and a wide effective absorbing bandwidth (EAB) of 4.32 GHz with a filling content of merely 5 wt%. Benefiting from the outstanding dielectric loss, appropriate impedance matching, and strong attenuation capacity, PI/G demonstrated strong, wide band, and excellent low-frequency absorption. In light of the radar cross-sectional (RCS) simulation results, PI/G could significantly suppress the strong scattering of EMWs. In addition, PI/G/natural rubber (PI/G/NR) composites exhibited remarkable thermal conductivity, flexibility, and smooth surface. This work paves the way for the preparation of highly efficient heat-conduction microwave absorbers with the direction of RCS simulations and offers an interesting option in the electronic packaging field.