Self-standing and compressible SiC_nw/SiC_nf composite aerogel via free carbon in-situ transformation mechanism: Towards thermal and electromagnetic wave protection

SiC nanofiber-based composite aerogel represents a promising lightweight, high-temperature-resistant, and broadband-absorbing material. However, the residual carbon phase during the pyrolysis process would threaten the high-temperature oxidation tolerance. Herein, a free carbon in-situ transformation (FCIT) strategy was proposed to convert the amorphous free carbon on the surface of SiC nanofibers into SiC nanowires, constructing a multi-scale SiC nanowire/SiC nanofiber (SiC_nw/SiC_nf) composite aerogel. The SiC_nw great broaden the inner fibrous framework, and the hierarchical network offers great enhancement for EM attenuation, compression resistance and thermal insulation. The self-standing composite aerogel possesses excellent flexibility (1500 cycles in 180°-bending test) and compression resistance (100 cycles at 40 % strain). With only 10 wt% filler content, the SiC_nw/SiC_nf sample displays an effective absorption bandwidth (EAB) of 8.81 GHz (9.19–18.00 GHz) at a thickness of 2.94 mm. Even after enduring oxidation at 800 °C, the EAB still remains substantial at 6.92 GHz (11.08–18.00 GHz). Moreover, the outstanding mechanical performance were also retained under high temperature and oxidation environment due the reduced density and thermal conductivity. Therefore, the multifunctional SiC_nw/SiC_nf composite aerogel prepared by FCIT strategy could be served as efficient thermal and EMW protection candidate.