Phenolic foam-derived magnetic carbon foams (MCFs) with tunable electromagnetic wave absorption behavior

Abstract

• Magnetic porous graphitic carbon-based foams are synthesized. • Ultralight EMW absorbers with strong capacity, broad frequency and thin thickness. • The mechanism of the EMW absorption behavior has been discussed in depth. • Effect of internal cell-wall thickness on EMW absorption behavior is investigated. • Effective adsorption from C to Ku band is achieved via adjusting absorber thickness. By now, magnetic porous carbon-based composites have almost dominated recent development of electromagnetic wave (EMW) absorbers. Herein, we report on the fabrication of magnetic carbon foams (MCFs) via in-situ polymerization of iron acetylacetonate (Fe(acac) 3 ) N, N-Dimethylformamide (DMF) solution and phenolic resin, followed by in-situ carbonization processes, and the investigation of their EMW absorption behaviors and regulatory mechanism. MCFs display solid 3D foam architectures based on interconnected cells with narrow and smooth C/CFe 15.1 skeletons, where α-Fe, Fe 2 O 3 and Fe 3 Care formed on their surface. The EMW absorption capacity of MCFs varies with iron contents and internal foaming pressures. Among them, the absorber obtained with 0.12 g/mL Fe(acac) 3 and under a controlled pressure of 0.4 MPa possesses not only the strongest absorption capacity with the minimum reflection loss value of −54.02 dB and the relatively thin matching thickness (3.05 mm), but also the broadest effective absorbing bandwidth of 8.92 GHz. In addition, MCF-3 demonstrates the potential of simultaneously effectively absorbing EMWs from C-band to Ku-band by simply adjusting the thickness of the absorbers. The superior absorption behavior is proved to be attributed to the Maxwell-Wagner-Sillars (MWS) polarization and the residual loss. Besides, multiple reflections and scatterings inside the macroporous structures of MCFs increase the path of EMW propagation, being beneficial to the attenuation of EMW. This is the first time to investigate cell-wall thickness effect on EMW absorption capacities of porous absorbers. Our research hews out a facial way for preparing carbon-based foams embedded with metal/metal oxide and their application in EMW absorption.