This study presents large-scale fabrication of singlecrystal SiC nanowire (SiC nw ) sponges through a carbothermal reduction approach using agricultural residue loofah, which is believed to be a perfect alternative to traditional petrochemical materials as the carbon source in industrial fabrication of SiC nanowires, without additional chemical C sources or catalysts. The single-crystal ultralong SiC nw are observed to have diverse morphologies with diameters of 50−400 nm, which possess a significant anisotropic and hierarchical microstructure with planaraligned bamboo joints. A roughly 2 nm thick amorphous SiO 2 layer is identified wrapping the crystalline 3C-SiC. The underlying vapor−solid mechanism is systematically investigated via thermodynamic calculations on the formation and interactions of SiO, CO, and SiC. Noteworthily, the fabricated loofah-based SiC nw sponge exhibits prominent high-temperature performance after thermal insulation tests of alcohol lamp flame and butane blowtorch flame, which is attributed to the stacking faults, SiO 2 layer, SiC/ SiO 2 interface of the nanowires, and the overlength pathway in the porous aerogel−sponge domain synergetically acting as a phonon barrier to enhance phonon scattering, prolong phonon diffusion, and eventually reduce solid thermal conductivity in the sponge architecture. Our current work has great potential to be applied in the eco-friendly industrial preparation of high-performing SiC nw as thermal protection materials in harsh environments.

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