Multiscale symbiotic carbonaceous silica nanofiber aerogels composed of a ZrO2 pinning structure with high-temperature thermal insulation and high strength

Abstract

Silica fiber aerogels often show considerably increased high-temperature thermal conductivity because of the weak infrared extinction ability, while showing limited mechanical strength. Improving infrared shielding and boosting structural strength are key challenges in achieving high-temperature insulation with SiO₂ nanofiber aerogels. Here, a multiphase sequence and multiscale structural engineering strategy is proposed to synthesize multiscale symbiotic carbonaceous SiO₂ nanofiber aerogels composed of a ZrO₂ pinning structure to achieve high-temperature thermal insulating performance with high mechanical strength. The ZrO₂ nanocrystalline pinning effect can effectively impede the formation of a shear band and suppress the generation-migration of pores and micro-cracks of single amorphous SiO₂ nanofibers, enhancing thermal stability and mechanical strength. Besides, what is particularly impressive is that the design of the pinning structure can also stabilize high extinction symbiotic carbon species to achieve the presence of high content carbon, thereby suppressing the thermal radiation heat transfer to reduce high temperature thermal conductivity. Meanwhile, the layered assembly and coating construction at the mesoscale further enhance the antioxidant capacity of the aerogel. Finally, the 3D aerogel assembled in layers demonstrates outstanding mechanical properties (a compressive strength of 78.27 kPa at 60% strain and a tensile strength of 240.69 kPa, which is several times better than that of other ceramic fiber aerogels) and ultralow thermal conductivity over a wide temperature range (0.0935 W m⁻¹ K⁻¹ at 1000 °C, which is approximately one order of magnitude lower than that of conventional ceramic fiber aerogels). Our work provides a new option for heat insulation under extreme conditions.