Armoring Boron Nitride with Pyrolytic Carbon Layers for Tunable Rigidity and Flexibility

Abstract Ceramic aerogels are acclaimed as ideal materials for extreme environments due to their ultrahigh porosity, low density, and exceptional thermal stability. However, the practical application of traditional ceramic aerogels is constrained by their inherent mechanical brittleness. Herein, a strategy is proposed to customize mechanically tunable aerogels by armoring ceramic nanounits with pyrolytic carbon (PyC). The PyC encapsulating layers with various thicknesses are transformed into ductile tights or rigid armors, facilitating the mechanical customization of BN@PyC aerogel from superelasticity to rigidity across scales. Interestingly, the PyC armor imparts unique versatility to the aerogel, including flame retardancy, elastic response conductivity, and thermal conductivity. Furthermore, owing to the thermal stability of the PyC armor, the BN@PyC aerogel maintains its mechanical integrity even after high‐temperature thermal treatment, and exhibits an unexpected resistance to butane torch ablation. Integrating mechanical stability, high‐temperature resistance, and multifunctionality, BN@PyC aerogels offer new possibilities for scalable applications in extreme environments. This facile strategy of armoring brittle ceramic aerogels with PyC provides a novel reference for customizing the mechanical properties of multifunctional aerogels.