Enhanced thermal stability of Al2O3 nanofibers via core-shell structural design for thermal insulation nanofibrous aerogels

Alumina-based nanofiber aerogels are commonly utilized in high-temperature insulation applications because of their remarkable chemical stability and low thermal conductivity. However, Al 2 O 3 nanofibers tend to experience grain growth at high temperatures, which severely impacts their performance. In this study, core-shell Al 2 O 3 nanofibers with SiO 2 coating were prepared using coaxial electrospinning technology. Combined with the foam template method and freeze-drying technology, Al 2 O 3 nanofiber aerogels with excellent thermal stability were fabricated. The results show that the shell thickness was controlled by adjusting the injection speed of SiO 2 solution. The SiO 2 shell effectively suppressed Al 2 O 3 grain growth, and as the shell thickness increased, the phase transition rate from γ -Al 2 O 3 to α -Al 2 O 3 gradually slowed, effectively enhancing the fibers' thermal stability. Moreover, as the SiO 2 shell thickness increased, the compressive strength of the aerogel after 1000 °C calcination increased from 16.08 kPa to 28.6 kPa at 50% strain, while its thermal conductivity decreased to 0.0298 from 0.0402 W/(m·K). This demonstrates a marked enhancement of the aerogel's mechanical and thermal insulation properties, further showing that improved fiber thermal stability contributes to overall aerogel performance. This study provides an effective approach for designing nanofiber aerogels with superior properties and offers a reference for their further application in high-temperature thermal insulation fields.