Superelastic and responsive anisotropic silica nanofiber/polyvinylpyrrolidone/MXene hybrid aerogels for efficient thermal insulation and overheating alarm applications

Although silica aerogels with ultralow thermal conductivity are competitive for thermal insulation, their deficiencies in mechanical properties and single function affect their wide applications. Herein, we demonstrate a “soft fiber-stiff sheet” synergistic strategy for fabricating superelastic and responsive anisotropic silica nanofiber/polyvinylpyrrolidone/MXene hybrid aerogels by electrospinning, calcination, and directional-freezing. The anisotropic hybrid aerogel exhibits satisfactory thermal insulation performances at both high and low temperatures, delivering a low thermal conductivity of 21 mW m−1 K−1. The top surface temperature of the hybrid aerogel maintains at ∼74 °C after its standing on a hot plate of 300 °C. By putting the hybrid aerogel on a cold plate of −30 °C, its surface temperature is only 7.2 °C lower than the ambient temperature. Interestingly, the oxidation of MXene at high temperatures could transform the hybrid aerogel from electrically conductive to insulating, leading to sharp changes in electrical signals to trigger overheating alarm. Furthermore, the hybrid aerogel exhibits high compressibility and fatigue resistance with a high stress retention rate of 97.3% after 100 cycles under the compressive strain of 50%. Such compressive and thermally insulating aerogels are promising thermal management materials for smart alarms, and heat and cold protection of electronic devices.