Additive manufacturing of biomimetic lightweight silicon oxycarbide ceramics with high mechanical strength and low thermal conductivity

Thermal insulation is crucially important to the safety and reusability of aerospace vehicles. Fabrication of thermal insulation materials with light weight, high mechanical strength and low thermal conductivity remains challenging. In this study, porous polymer derived silicon oxycarbide (SiOC) ceramics with hierarchical structures mimicking cuttlebones were prepared through stereolithography additive manufacturing followed by pyrolysis. The compressive strength of SiOC ceramics with ridges ("R" structures) alongside the sinusoidal walls ("S" structures) (RS-SiOC, 13.37 +/- 0.86 MPa for 7-RS-SiOC) mimicking those of cuttlebone was much higher than that of SiOC ceramics with just sinusoidal walls (S-SiOC, 8.43 +/- 0.81 MPa), while the density of RS-SiOC with 7 ridges (7-RS-SiOC) and S-SiOC were 0.40 g/cm(3) and 0.39 g/cm(3), respectively. Our results revealed that the tailored "S" and "R" structures of biomimetic 7-RS-SiOC ceramics, together with the amorphous network of SiOC assembled in the layer-by-layer manner, rendered the high mechanical strength. In addition, the 7-RS-SiOC sample exhibited a low thermal conductivity of 0.12 W/(mK) at room temperature. The back temperature of the 7-RS-SiOC sample was 179.5 degrees C when exposed to 800 degrees C for 1200 s, showing excellent thermal insulation capability. The state-of-the-art biomimetic design of lightweight SiOC ceramics likely offers a solution to high-performance thermal insulation for aerospace vehicles.