Fig. 1. Preparation of SiO₂–Al₂O₃ composite ceramic sponges (SAC sponges).

a Schematic diagram of the design and preparation process of the SAC sponges. b Schematic to show the high compressibility of the SAC sponges. The SAC sponges possess anisotropic mechanical properties and high compressibility owing to the unique lamellar structure. c Photograph of a large SAC sponge sample to demonstrate the scalability of the preparation method. d Photograph of a typical circular SAC sponge, which has a diameter of 16 cm. e Photograph showing a square SAC sponge cut from the large sample in d. Scale bar in e, 1 cm. The inset in the top right corner is the photograph of a microfiber layer peeling off from the square SAC sponge. f Photograph of a cubic SAC sponge sample obtained by stacking some square SAC sponge sheets. This shows how the thickness of the lamellar SAC sponge can be adjusted. Scale bar in f, 1 cm.