Strong yet Superelastic Fibrous Ceramic Aerogels With Ultralow Shrinkage at 1200°C via Crystalline Nanoshell

Fibrous ceramic aerogels that simultaneously achieve high strength, superelasticity, and ultrahigh‐temperature dimensional stability remain an unmet challenge, as the amorphous phases essential for structural integrity typically accelerate sintering and collapse above 1000°C. Here, we report an in situ skeleton encapsulation strategy that creates fibrous ceramic aerogels (FCAs) with a unique amorphous@crystalline core–shell architecture. During two‐step calcination, ZrB 2 particles oxidize to form a continuous ZrO 2 nanoshell layer on the amorphous SiO 2 fiber surface, with a thin B 2 O 3 interlayer naturally generated at the interface. This hierarchical structure synergistically combines two protective mechanisms revealed by finite element method (FEM) simulations: (i) mechanical stress shielding and (ii) interfacial thermal barrier effects. At the optimized ZrB 2 loading (6 wt.%), the resulting aerogel demonstrates superior dimensional stability with a linear shrinkage of only 0.7% after 3000s and 11.72% after 24 h at 1200°C, together with superelasticity and high strength of 0.08–1.08 MPa at 10%–80% strain. This work resolves the long‐standing paradox between high‐temperature stability and mechanical robustness in elastic ceramic aerogels, offering a versatile design platform for next‐generation aerospace thermal protection.