In situ construction of hierarchical TiO₂ nanowire/mullite fiber composite aerogels with enhanced ablation resistance

Ceramic fiber aerogels are highly desirable for extreme thermal protection due to their ultralight weight and superior insulation. However, their sparse skeleton often suffers from high radiative heat transfer and structural fragility, leading to catastrophic failure under intense heat flux. Here, a robust hierarchical structure is constructed via the in situ growth of TiO₂ nanowires (TNWs) on mullite nanofiber (MNF) aerogels to systematically enhance high-energy laser ablation resistance. This multiscale design significantly improves reflectivity from 94.68% to 97.25% and reduces light absorption by 48.3%, effectively mitigating laser ablation damage through high reflection and scattering efficiency. The MNF-TNW aerogels also exhibit superior thermal management, showing 30.8% lower thermal conductivity at 1000 and a 51.3 °C lower back temperature under flame exposure than conventional MNF aerogels. Under high-energy laser ablation at 300 W·cm⁻², the MNF aerogels fail within 3 s, whereas the MNF-TNW aerogels withstand 30 s of ablation and repeated impacts. Even at 500 W·cm⁻² for 30 s, no significant damage occurs. Therefore, this in situ growth strategy offers a promising avenue for engineering high-performance ceramic aerogels for applications in extreme environments.