HPMC-Based Anisotropic Aerogels with HGM-Alumina Fiber Co-Filling for Extreme-Temperature Thermal Management

Overcoming the inherent density-strength-stability trade-off in ceramic aerogels remains challenging. Herein, we present HAlCAs, an ultralight aerogel fabricated by integrating hollow glass microspheres and alumina microfibers within a nano-hydroxypropyl methylcellulose (HPMC) matrix. Utilizing a sol-gel process followed by directional freeze-casting, we construct a deliberately engineered, 3D interwoven scaffold with uniformly dispersed fibers and microspheres. This unique “rigid-yet-flexible” architecture achieves a record porosity of 96% and an ultralow density of 20 mg cm −3 . Critically, it endows HAlCAs with fully recoverable superelasticity across an extreme temperature range (−196°C to 1200°C), while simultaneously suppressing structural collapse and thermal-conductivity surges. The resultant aerogel exhibits exceptional thermal insulation, with a room-temperature conductivity of 0.028 W m −1 K −1 that rises minimally to only 0.046 W m −1 K −1 even at 1200°C. Remarkably, a 20 mm-thick HAlCAs sample reduces the backside temperature by 1000°C when exposed to a 1200°C flame, highlighting its outstanding flame barrier performance. This green, scalable process routinely yields monoliths from abundant, low-cost precursors. Combining ultralow density, high temperature superelasticity, superior thermal insulation, and intrinsic flame retardancy. HAlCAs aerogels offer opportunities for next-generation thermal super-insulators in extreme environments, including hypersonic thermal-protection systems, deep-space insulation cabins, industrial furnaces, and battery packs.