Rotary-spun cristobalite fibrous aerogels with alkali-induced crystallization for multifunctional thermal and electrical protection

Abstract

Natural volcanic processes provide critical insights into crystallization pathways for materials designed for extreme environments. Inspired by these phenomena, we present an alkali-ion-catalyzed strategy to transform amorphous silica fibers into robust β-cristobalite fibrous aerogels at significantly reduced temperatures (∼900 °C). By incorporating trace amounts of potassium ions into a sol-gel precursor and utilizing airflow-assisted rotary spinning, we produce ultralight fibrous aerogels (5–50 mg·cm−3) that exhibit reversible polymorphism, high thermal resilience up to 1500 °C, and excellent mechanical flexibility. In situ X-ray diffraction and electron microscopy analyses reveal an ion-induced nucleation mechanism wherein K+ ions disrupt the Si-O-Si network, reduce interfacial energy, and accelerate crystallization. This structural transformation occurs without compromising the entangled fibrous morphology, preserving compliance and thermal shock resistance. The resulting aerogels demonstrate low thermal conductivity (0.026–0.028 W·m−1 K−1), exceptional elasticity, and long-term stability under direct flame exposure and electrical stress. Notably, the integration of sol-gel synthesis with scalable airflow-assisted rotary spinning facilitates continuous, ambient-pressure fabrication of large-area fibrous aerogels, offering a practical pathway for industrial production. Practical demonstrations highlight their multifunctionality in metal structural protection, battery cell thermal management, and electrical insulation under extreme fire exposure.