Ambient-Pressure-Dried Flame-Retardant Biomass-Based Hybrid Aerogel with Stiffness and Thermal Insulation at High Temperature

Abstract

Aerogels, as competitive thermal insulating substitutes, are seriously plagued by the deterioration of mechanical and insulating properties at high temperatures as well as energy-consuming drying methods. Herein, organic-inorganic biomass composite aerogels with ablative properties are fabricated by a straightforward and environmentally friendly ambient-pressure-dried method, utilizing gellan gum, hollow glass microspheres, and phenolic resin. This method uses air bubbles as pore templates for constructing aerogels without additional modification or organic solvent consumption. The robust cross-linking networks formed within the aerogels significantly mitigate volume shrinkage induced by surface tension during mild drying while endowing the aerogels with a high modulus of 37.8 MPa and robust resistance to diverse rigors. Remarkably, upon exposure to high temperatures or fire, it spontaneously transforms into ceramic-like hybrid char with low volume shrinkage, continuous pore structures, and high stability. The ablative property of these aerogels enables them to maintain a high modulus of 8.22 MPa even after being treated at 900 °C, while also exhibiting excellent high-temperature insulation, flame retardance, and smoke suppression. This work provides a facile and ecofriendly way for developing advanced hybrid biomass aerogels that combine high stiffness with superior thermal protection across a wide temperature range.