Hydrophobic SiC@C Nanowire Foam with Broad-Band and Mechanically Controlled Electromagnetic Wave Absorption.

With the booming of modern information technology, electromagnetic wave (EMW) absorption materials are playing more and more crucial roles in applications ranging from wearable smart electronics to national defense security. However, the application of present EMW absorption materials is severely hindered by their drawbacks, such as narrow absorption bandwidth and low absorption intensity. In this work, a series of highly porous and well-interconnected SiC@C nanowire foams (SCNFs) are rationally designed to exhibit modified impedance match and multiscale EMW energy dissipation mechanisms. The SCNF with a density of 108 mg cm-3 realizes a broad absorption bandwidth covering the whole X and Ku bands with an intensity of -52.5 dB. The SCNF with a density of 36 mg cm-3 and a thickness of 9.6 mm exhibits a mechanically controlled absorption band ranging from 2.9 to 18 GHz (covering over 93% of the entire radar band, 2-18 GHz) with a minimum intensity of -46 dB by simply applying a reversible compressive strain from 0 to 66.7%. Moreover, the special microstructure of SCNF also endows it with excellent hydrophobicity, which enables its good self-cleaning property. These encouraging achievements pave the way to the development of the continuous network microstructure of absorbents with a broad-band and tunable EMW absorption property.