A novel cellulose-derived graphite carbon/ZnO composite by atomic layer deposition as an over-wideband microwave absorbent†

It is a major challenge to obtain broadband microwave absorption (MA) properties using low dielectric or magnetic nanoparticle-decorated carbon composites due to the limited single conductive loss or polarization loss of the carbon materials used as substrates. Novel pure cellulose-derived graphite carbon (CGC) materials can be used as an exceptional substrate option due to their special defective graphitic carbon structure, which provides both conduction and polarization loss. Herein, CGC@ZnO composites were first synthesized by atomic layer deposition (ALD) for use as microwave absorbents. Thanks to the multiple interfaces composed of graphitic carbon, defective carbon, and polar ZnO molecules, the CGC@ZnO composites exhibited superior MA properties. Specifically, the CZ-3 achieved a minimum reflection loss (RL_min) of −50.5 dB (over 99.999% MA) at 6.16 GHz in 2.98 mm. Amazingly, the maximum effective absorption bandwidth (RL < 10 dB, EAB_max) could reach up to 6.48 GHz at only 1.59 mm. The ultra-broadband absorption property is mainly attributed to its strong electromagnetic attenuation capability and excellent impedance matching, making it one of the most promising materials for MA applications.