Strong and Heat-Resistant SiC-Coated Carbonized Natural Loofah Sponge for Electromagnetic Interference Shielding

Renewable, processable, and efficient electromagnetic shielding materials have received great attention with the urgent requirement of alleviating the depletion of fossil resources and the harm of electromagnetic pollution. Biomaterials (natural loofah sponges) have long been considered to be good candidates because of their unique texture and environmental friendliness. However, these natural fibrous structures are usually required to be electrically conductive by carbonization treatment, which leads to lose their original flexibility and strength. Here, we have successfully prepared a SiC-coated carbonized loofah sponge (SCLS) electromagnetic shielding material together with high flexural strength and good thermal insulation properties. A 2.5 mm thick SCLS achieves an electromagnetic shielding effectiveness of 68.4 dB, which is extremely competitive among those reported porous shielding materials at the same thickness. This outstanding property originates from the formation of a continuous three-dimensional conductive network constructed by the carbonized loofah sponge (CLS) coated with SiC and tailorable porosity. The electrical conductivity of SCLS reaches 22.3 S/m. More importantly, the flexural strength of 8.4 MPa offered by the SCLSs enables them to be directly applied to the practical environment. Moreover, the CLS exhibits a polymer-like thermal insulation, achieving a thermal conductivity of only 0.226 W m^–1 K^–1 at 300 °C. Therefore, the multifunctional CLS has great potential to be widely used in electromagnetic shielding materials with good heat and fire resistance.