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

•A sodium alginate derived 3D SiCw@C composite aerogels were designed and fabricated.•SiCw@C aerogels have a hierarchically oriented micro-channel architecture.•The electromagnetic parameters of SiCw@C composite aerogels could be tuned by inducing different crosslinking cations.•SiCw@C-Fe exhibited good wave absorption performance at a thickness of 2 mm, RLmin is −49.2 dB, and EAB is 3.6 GHz. 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 (SiCw) as the reinforcing material, a series of three-dimensional (3D) SiCw@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 SiCw@C-Al exhibits a considerable minimum reflection loss (RLmin) value at 1.5 mm thickness (-28.7 dB) and a broad effective absorption bandwidth (EAB, RL