Thermal insulating and fire-retardant Si₃N₄ nanowire membranes resistant to high temperatures up to 1300 °C

Superior thermal insulating and fire-retardant ceramic membranes are urgently demanded in the aerospace, construction, and chemical engineering industries. However, the generic characteristics of ceramic membranes, such as brittleness, structural collapse, and crystallization-induced pulverization behavior, present a great plague to their practical applications. Herein, we report a highly flexible, mechanically stable, fire-retardant, and high-temperature-resistant ceramic membrane based on the interlocked Si₃N₄ nanowires formed by the precursor pyrolysis method. The Si₃N₄ nanowire membrane (SNM) has excellent high-temperature resistance under alcohol lamps and butane spray lance. The thermal insulation with a thermal conductivity as low as 0.056 W m^–1 K^–1 can be attributed to the high porosity of SNM, which makes it a desirable candidate for heat insulators under harsh conditions. More importantly, SNM exhibits thermal stability and robust mechanical properties in the range of 25 to 1300 °C. The high-temperature resistance of SNM up to 1300 °C is achieved by the four stages: Si₃N₄ nanowires, Si₃N₄@SiO₂ nanowires, SiO₂ nanowires, and bead-like SiO₂ nanowires. After heat-treated at 1300 °C, the macroscopic size of SNM does not change significantly, and the interlocked structure is still maintained. Furthermore, SNM still maintains excellent mechanical properties, with tensile strength as high as 0.26 MPa. This work provides a facile method for fabricating excellent thermal insulating and fire-retardant ceramic membranes, showing prospective application prospects in the era of thermal insulating materials.