Lamellar anisotropic ceramic nanofibrous aerogels for thermal insulation

Abstract

Thermal protection in high-temperature environments urgently demands ceramic aerogels that combine mechanical flexibility with low thermal conductivity. However, due to the heat transfer mechanism dominated by thermal radiation, conventional materials exhibit a sharp increase in thermal conductivity above 800 °C, which limits their practical application. To address this, we constructed a ceramic nanofibrous aerogel with an anisotropic lamellar structure, in which the nanofibers consist of a SiO2 shell and a multi-walled carbon nanotube (MWCNT) core. The as-prepared aerogel fully recovers from 80% compressive strain and maintains excellent structural integrity after 1,000 compression cycles at 50% strain. Furthermore, across the fiber membrane, the thermal conductivity drops to just 27.62 mW/(m·K) in the perpendicular orientation. More importantly, the embedded MWCNT cores serve as an infrared-absorbing medium, and radiative heat transfer is considerably suppressed, yielding a minimum thermal conductivity of 106.98 mW/(m·K) at 800 °C, which is far lower than reported values for similar materials. The synergistic design strategy of core-shell fibers combined with lamellar stacking presented in this work demonstrates an effective route to flexible thermal insulation materials suited for harsh environments.