Bird's nest inspired aerogels towards ultrahigh strength and robust flame retardancy at extreme environment

The mechanical properties of aerogels remain a critical concern for their application. Inspired from the hierarchical architecture of bird's nests, we have designed an effective biomimetic hybrid strategy for creating an aerogel with ultrahigh strength and robust flame retardancy. The super-molecular micro-to nanofibrils formed by boric acid and melamine act as “twigs” while a small part of biobased polysaccharide agar serves as “glue”. Via the water as the solvent and an eco-friendly freeze-drying method, the obtained boric acid-melamine/agar (BMA) aerogel with a low density (0.0760 g/cm³) exhibited exceptional high compressive strength, reaching up to 3.92 MPa at 80 % strain. A piece of the BMA aerogel with 10 cm² can resist a motorcycle (150 kg) easily without any deformation. Additionally, the BMA aerogel demonstrated outstanding inherent flame retardant property (achieving UL-94 V-0 rating with relatively low the heat release, total heat release and CO release rate values) as well as superior thermal insulating properties (with a thermal conductivity as low as 0.0364 W/m⋅K). Given the distinctive mechanical properties and excellent other properties, the BMA aerogels hold great promise for potential promise in energy-saving and thermal protection applications. and the superior stiffness mechanism behind this performance is also analyzed.