High yield hollow carbon cubes with excellent microwave absorption property at a low loading ratio

High yielding synthesis of hollow carbon cubes (HCCs) was realized by using easily available NaCl cubes as templates in a simple way. The cubic carbon shells featuring an average side length of 3.5 mm, a thickness of 22.9 nm and the presence of macro and mesopores in the material, endow the HCCs/paraffin composites with an appropriate balance between good impedance matching and strong loss capacity. Superior electromagnetic wave (EMW) absorption performance was obtained at a very low loading ratio of 1.5 wt% of the HCCs. The composite having 4.5 mm thickness gave the maximum reflection loss of -46.0 dB at 7.8 GHz. At a thickness of 2.6 mm, a maximum effective absorption bandwidth of 6.6 GHz was achieved. Further investigation on the EMW dissipation mechanism of HCCs surrounding polarization relaxation and conductive loss was conducted. The integrity of the hollow structure plays a dominant role during EMW dissipation. The present study provides easy processing, cost-effective and environment-friendly HCCs as a predominant candidate for ultralight carbon-based EMW absorbing materials.