Sodium alginate derived SiC-carbon composite aerogel for effective microwave absorption

Biomass-derived carbon aerogels are expected to be ideal candidates for electromagnetic wave (EMW) absorption due to their extensive sources, cheap cost, low density and abundant porosity. Herein, using the natural polymer sodium alginate (SA) as the carbon-based precursor and SiC nano-whiskers (SiC_w) as the reinforcing material, a series of three-dimensional (3D) SiC_w@C composite aerogels doped with different metal ions (Fe, Ni, Al) were designed and studied for lightweight and effective EMW absorption. The emergence of metal ions and three-dimensional conductive carbon networks enriches the loss mechanism of the composites. The results show that the SiC_w@C-Al exhibits a considerable minimum reflection loss (RL_min) value at 1.5 mm thickness (-28.7 dB) and a broad effective absorption bandwidth (EAB, RL < -10 dB) of 4.1 GHz. Meanwhile, SiC_w@C-Fe has good wave absorption performance at a thickness of 2 mm, RL_min is −49.2 dB, and EAB is 3.6 GHz. By adjusting the matching thickness of the Al³⁺ and Fe³⁺ crosslinked composite aerogel from 1.5 mm to 3.5 mm, the integrated EAB can cover the Ku-band, X-band and even C-band. The SA derived 3D SiC_w@C composite aerogels open a new path for the design of lightweight and effective EMW absorption materials used in multi-frequency.