Ultralight lamellar amorphous carbon foam nanostructured by SiC nanowires for tunable electromagnetic wave absorption

Three-dimensional hybrid foams of SiC nanowires (SiC NWs) coated and bonded with nanostructured lamellar carbon films are, herein synthesized for the first time, by combination of unidirectional freeze drying and carbonization techniques. The crystallinity of the carbon films was tunable from amorphous carbon to graphene-like carbon by heat treatment of the as-received hybrid foams to different temperatures within the range of 600–1500 °C. The SiC NWs-nanostructured lamellar carbon (SiC NWs/C) hybrid foams exhibited electromagnetic (EM) wave absorbing properties highly superior to current state-of-the-art counterparts, at filler loadings as low as 9.2 mg/cm³. Effective absorption bandwidth of the SiC NWs/C foam was observed to cover the whole X-band frequency range of 8.2–12.4 GHz, with reflection loss values reaching −31 dB for an optimum thickness of 3.3 mm. The absorption efficiency of the SiC NW/C hybrid foams is discussed in the text in view of the highly absorbing layered morphology of the developed material, of interfacial polarization and multiple reflections effects and of polarization relaxation effects.