Enhancing thermal safety of hydrophobic SiO2 aerogels through introducing ammonium polyphosphate intercalated layered double hydroxides

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Enhancing the thermal safety of hydrophobic SiO2 aerogels (SAs) is crucial for its practical thermal insulation applications. Here, we explore a facile method to enhance the thermal safety of hydrophobic SAs with the introduction of ammonium polyphosphate intercalated layered double hydroxide (APP-LDH). The obtained results show that as-produced APP-LDH/SA composites maintain excellent fundamental properties, including low density (0.14–0.16 g/cm3), high porosity (92.8–93.5 %), high specific surface area (680.0–762.6 m2/g), and low thermal conductivity (25.3–26.9 mW/m/K). Notably, APP-LDH effectively inhibits the thermal oxidation decomposition of SAs. In comparison to pristine SAs and those modified solely with LDH, the APP-LDH/SA composites exhibit significantly improved thermal stability. The gross calorific value of the APP-LDH/SA-20 % (i.e., containing 20 wt% APP-LDH) decreases by 13.9 % and 5.2 % compared with that of neat SAs and SAs modified solely with 20 wt% LDH, respectively. The improved thermal stability and reduced gross calorific value completely confirm the enhancement of the thermal safety of the APP-LDH/SA composites. This work provides a simple method to improve the thermal safety of hydrophobic SAs, which expands the thermal insulation application scenarios of SAs.