Synthesis of flame-retardant and UV-resistant TiO2-doped silica aerogel composites for thermal insulation

High-performance HPSA/ATiO 2 composite aerogels are successfully fabricated. • HPSA/ATiO 2 aerogels show significantly improved flame retardancy and thermal stability. • HPSA/ATiO 2 aerogels exhibit low thermal conductivity, low density, and strong hydrophobicity. The coexistence of long-term low temperature and strong ultraviolet (UV) radiation in cold and high-altitude regions put forward stringent requirements for the thermal insulation and durability of building envelopes. However, conventional thermal insulation materials often struggle to simultaneously achieve low thermal conductivity and stable long-term performance. Therefore, it is critical to develop high-performance thermal insulation materials to improve indoor thermal comfort and reduce building energy consumption. In this work, surface modified titanium dioxide (ATiO 2 ) was incorporated to enhance the UV resistance of hydrophobic silica aerogel (HSA), and then used hypophosphorous acid as the acid catalyst to prepare flame retardant HSA composite aerogels (HPSA/ATiO 2 ). The aerogel exhibited outstanding UV resistance and flame retardancy while maintaining favorable comprehensive properties. For instance, HPSA/ATiO 2 –   0.50 containing 0.5 g ATiO 2 has low density (0.1594 g/cm 3 ), low thermal conductivity (24.9 mW·m –1 ·K –1 ), high specific surface area (654.3 m 2 /g), and high water contact angle (131.2°). Compared with the pristine sample, its total heat release and gross calorific value decreased by 44.7% and 26.39%, respectively. Moreover, the thermal stability of HPSA/ATiO 2 –   0.5 is also significantly improved compared with pure HSA. This study provides a valuable strategy for constructing high-performance HSA and broadens its potential applications in cold and high-altitude environments.