Development of hydrophobic silica aerogels with superior thermal and flame-retardant properties for energy-efficient buildings

Hydrophobic silica aerogel (HSA) is widely recognized for its ultralow thermal conductivity and high porosity, making it an ideal candidate for building thermal insulation and aerospace applications. However, its intrinsic flammability severely limits broader usage. In this work, a multifunctional flame-retardant HSA composite was successfully developed by employing DOPO as a phosphorus-based catalyst and incorporating hollow silica microspheres (HSM). The resulting DSA/HSM composite exhibited significantly enhanced thermal stability and flame retardancy. Specifically, the composite with 0.1 g HSM showed a 19.2 % reduction in peak of heat release rate and a 61.6 % decrease in total heat release compared to pristine HSA. Moreover, the DSA/HSM composites maintained excellent hydrophobicity and thermal insulation, with a water contact angle of 143.2° and a thermal conductivity of 24.3 mW m −1  K −1 . This study presents a facile and feasible strategy for fabricating advanced HSA composites with combined thermal insulation and flame retardancy, offering promising potential for application in energy-efficient and fire-safe building materials.