ZrO2/SiO2/C nanofiber aerogels with enhanced mechanical and thermal insulation properties fabricated by freeze casting

Because of the inherent high-temperature resistance, the application of ZrO 2 nanofiber aerogels in thermal insulation is promising. However, the contradiction between mechanical and thermal insulation properties has limited its applications. In the present work, nanofiber aerogels of ZrO 2 /SiO 2 /C with enhanced thermal insulation and compressive strength were successfully prepared by freeze-casting using tetraethoxysilane (TEOS) as a binder. The effect of TEOS content on the microstructure, compressive and thermal insulation properties was investigated. The porosity of the fabricated aerogels is higher than 97.3 %. The pore structure exhibits hierarchical characteristics, with honeycomb pores on the micro-scale and mesopores on the nano-scale. Part of the SiO 2 phases generated by TEOS hydrolysis bond ZrO 2 nanofiber to form fiber junctions, while the others cover the surface of ZrO 2 nanofibers forming core-shell structure. With the increase of TEOS content, ZrO 2 /SiO 2 /C nanofiber aerogels showed a slightly decrease in thermal conductivity to a lower value of 0.032 W m −1  K −1 and an increase in compressive stress to 11.9 KPa. The thermal insulation mechanism and deformation mode during compression of aerogels were analyzed. This study not only provide ZrO 2 /SiO 2 /C nanofiber aerogels with both enhanced mechanical and thermal insulation properties, but also can guide the design and fabrication of other ceramic aerogels with excellent properties.