Sodium alginate/ Al2O3 fiber nanocomposite aerogel with thermal insulation and flame retardancy properties

The severe environmental pollution issues require the urgent development of new green building insulation materials. Biomass aerogel is deemed as an optimal candidate to replace petroleum-based insulation materials owing to its significant advantages such as low thermal conductivity, eco-friendliness, and high biocompatibility. The interaction of the composite two-phase interface and the fabrication of multilevel pore structures have a significant impact on the comprehensive performance of aerogel applications. In this study, a tunable double-crosslinked network skeleton structure construction of sodium alginate (SA) composite with Al 2 O 3 fibers is proposed, where Ca 2+ induces the sol–gel transition to form a second layer of strong bonding force to effectively support the skeleton structure, and various cross-linking modes, such as ionic bonding, hydrogen bonding and physical cross-linking, are used to synergistically improve the SA aerogel and endow it with multifunctionality. The prepared Al 2 O 3 fiber/SA (SAA) aerogels achieve excellent flame retardancy and self-extinguishing smoke suppression (peak heat release rate as low as 9.7 kW m −2 , and total smoke release rate in the low range of 0.5 m 2  m −2 ). It also has superior mechanical strength (high specific compression modulus of ∼53.3 KN m kg −1 ) and can withstand weights over 2600 times its own weight without deformation, besides the broad range of self-cleaning properties and outstanding biocompatibility. The creation of a double-crosslinked three-dimensional aerogel network via reinforcement of inorganic electrospun fibers provides new insights for eco-friendly insulation materials in construction.