Tuning the inner hollow structure of lightweight amorphous carbon for enhanced microwave absorption

Herein, we demonstrate that amorphous carbon can be converted to lightweight superior MA materials only via a facile inside three dimensional ordered hollow (3DOH) architecture fabrication. The as-fabricated 3DOH carbon (3DOHC) blocks consist of ordered spherical voids formed by connected thin porous amorphous carbon walls. The diameter of the voids has a great influence on the MA performance, and a minimum reflection loss (RL) value of -66.24 dB is observed at 15.68 GHz for the 3DOHC blocks with inside void diameter of 500 nm (3DOHC-500) at a low filling rate of 5.0 wt% and absorber thickness of 1.6 mm. Moreover, the widest absorption bandwidth for RL values below -10 dB is 4.78 GHz when the absorber thickness is 1.7mm while still keeping a low RL value of -45.85 dB. The enhancement of the MA performance of 3DOHC-500 based absorber can be attributed to the synergic effect of dielectric loss and impedance matching. The excellent MA performance combining with the low filling rates (2.5-5.0 wt%), thin thickness and lightweight (<= 100 mg/cm(-3)) makes these 3DOHC-500 very promising candidate for practical MA applications.