Robust, fire-resistant, and thermal-stable SiZrNOC nanofiber membranes with amorphous microstructure for high-temperature thermal superinsulation

Ceramic nanofibers with robust mechanical properties, high-temperature resistance, and superior thermal insulation performance are promising thermal insulators used under extreme conditions. However, developing of ceramic fibers with both low solid thermal conductivity (λ_s) and low infrared radiation thermal conductivity (λ_r) is still a great challenge. Herein, according to the Ioffe–Regel limit theory, we report a novel SiZrNOC nanofiber membrane (NFM) with a typically amorphous structure by combining the electrospinning method and high-temperature pyrolysis technique in a NH₃ atmosphere. The prepared SiZrNOC NFM has a high tensile strength (1.98±0.09 MPa), excellent thermal stability (1100 ℃ in air), and superior thermal insulation performance. The thermal conductivity of SiZrNOC NFM was 0.112 W·m⁻¹·K⁻¹ at 1000 ℃, which is obviously lower than that of the traditional ceramic fiber membranes (> 0.2 W·m⁻¹·K⁻¹ at 1000 ℃). In addition, the prepared SiZrNOC NFM-reinforced SiO₂ aerogel composites (SiZrNOC_f/SiO₂ ACs) exhibited ultralow thermal conductivity of 0.044 W·m⁻¹·K⁻¹ at 1000 ℃, which was the lowest value for SiO₂-based aerogel composites ever reported. Such superior thermal insulation performance of SiZrNOC NFMs was mainly due to significant decreasing of solid heat conduction and thermal radiation by the fancy amorphous microstructure and high infrared shielding compositions. This work not only provides a promising high-temperature thermal insulator, but also offers a novel route to develop other high-performance thermal insulating materials.