Hydrothermal-Assisted Drying for Fabricating Silica Aerogels with High Intrinsic Structural Stability Withstanding Moisture Environments

Abstract

Silica aerogels are prized for their ultralow thermal conductivity, but their intrinsic hydrophilicity causes severe performance degradation under humid conditions. Here, we report SiO2 aerogels via a hydrothermal-assisted drying (HAD) process (hydrothermal-assisted drying of silica aerogel, HSA) that withstand >95% relative humidity for 10 h without measurable structural degradation and exhibit only a 6% increase in thermal conductivity (0.052 → 0.055 W/(m·K)). After five complete immersion-drying cycles, surface area (138–156 m2/g) and pore volume (1.01–1.30 cm3/g) remain basically unchanged, and thermal conductivity slightly varies by <12%. These properties arise from a neck-fused, pearl-necklace architecture generated during hydrothermal-assisted drying, not from postsynthetic hydrophobization. These findings extend the utility of silica aerogels to humid and thermally demanding applications that were previously precluded by moisture-induced collapse.