Thermal insulation under extreme conditions requires materials that can withstand complex thermomechanical stress and retain excellent thermal insulation properties at temperatures exceeding 1,000 degrees Celsius^1,2,3. Ceramic aerogels are attractive thermal insulating materials; however, at very high temperatures, they often show considerably increased thermal conductivity and limited thermomechanical stability that can lead to catastrophic failure^4,5,6. Here we report a multiscale design of hypocrystalline zircon nanofibrous aerogels with a zig-zag architecture that leads to exceptional thermomechanical stability and ultralow thermal conductivity at high temperatures. The aerogels show a near-zero Poisson’s ratio (3.3 × 10⁻⁴) and a near-zero thermal expansion coefficient (1.2 × 10⁻⁷ per degree Celsius), which ensures excellent structural flexibility and thermomechanical properties. They show high thermal stability with ultralow strength degradation (less than 1 per cent) after sharp thermal shocks, and a high working temperature (up to 1,300 degrees Celsius). By deliberately entrapping residue carbon species in the constituent hypocrystalline zircon fibres, we substantially reduce the thermal radiation heat transfer and achieve one of the lowest high-temperature thermal conductivities among ceramic aerogels so far—104 milliwatts per metre per kelvin at 1,000 degrees Celsius. The combined thermomechanical and thermal insulating properties offer an attractive material system for robust thermal insulation under extreme conditions.

极端条件下的隔热要求材料能够承受复杂的热机械应力，并在超过 1,000 摄氏度的温度下保持出色的隔热性能^1,2,3。陶瓷气凝胶是有吸引力的绝热材料；然而，在非常高的温度下，它们通常显示出显着增加的热导率和有限的热机械稳定性，这可能导致灾难性故障^4,5,6。在这里，我们报告了具有锯齿形结构的亚晶锆石纳米纤维气凝胶的多尺度设计，可在高温下实现出色的热机械稳定性和超低热导率。气凝胶的泊松比接近于零（3.3 × 10 ^-4）和接近零的热膨胀系数（1.2 × 10 ^-7每摄氏度），这确保了出色的结构灵活性和热机械性能。它们在剧烈热冲击后显示出高热稳定性和超低强度退化（小于 1%），以及高工作温度（高达 1,300 摄氏度）。通过在成分次晶锆石纤维中故意截留残余碳物质，我们大大减少了热辐射传热，并实现了迄今为止陶瓷气凝胶中最低的高温热导率之一——1000 摄氏度时每米开尔文 104 毫瓦。热机械和隔热性能相结合，为极端条件下的坚固隔热提供了有吸引力的材料系统。