Ultrathin and Light-Weight Graphene Aerogel with Precisely Tunable Density for Highly Efficient Microwave Absorbing

Graphene aerogel (GA) possessing good electrical conductivity and low weight has been widely considered as a promising candidate for high-performance microwave-absorbing (MA) materials. However, simultaneous realization of high reflection loss (RL), low thickness, and light weight remains very challenging for GA because of the trade-off between impedance match and attenuation ability. Herein, through use of (3-aminopropyl)triethoxysilane as a surface modifier and cross-linker, the GA materials with precisely controlled density are fabricated via a unique solvothermal protocol of zero-volume shrinkage. The density-controlled GA (4.5 mg·cm^-3) exhibits a remarkable minimum RL (RL_min) of -50 dB at a thickness of 1.14 mm in the K-band, owing to the optimized dielectric properties. Moreover, even higher attenuation ability without sacrificed impedance match is obtained by incorporating magnetic Fe₃O₄@C microspheres into the density-controlled GA. Superior MA performance involving unprecedented RL_min of -54.0 dB and qualified bandwidth covering 80% of the K-band has been achieved in the superlight Fe₃O₄@C/GA composite at a thickness less than 1 mm, which is highly desirable for MA material applied in mobile devices.