Synergistic investigation on thermal insulation in Al₂O₃/RF/SiO₂aerogels via silicon source ratios, heat treatment, and simulation

Aerogels have long been recognized in the aerospace field for their ultra‐lightweight properties and excellent thermal insulation, making them ideal for insulation in extreme environments. To address the limitations of mechanical brittleness and insufficient high‐temperature stability in traditional single‐component aerogels, this study synthesized Alumina/Resorcinol-Formaldehyde/Silica (Al₂O₃/RF/SiO₂) aerogels via ambient pressure drying. RF resin served as the organic carbon source to form a three-dimensional organic skeleton, which was subsequently oxidized during heat treatment to create a stable Al₂O₃/SiO₂composite framework with enhanced mechanical integrity. The synergistic effects of silicon source ratios and heat treatment temperatures were systematically investigated to enhance both thermal insulation performance and structural integrity. Experimental results revealed that the aerogel with a silicon source ratio of 3.5:3 exhibited the highest specific surface area and pore volume. The 700 °C heat treatment promoted the oxidation of the RF-derived organic framework and the formation of stable Al₂O₃/SiO₂composites, thereby reducing the room-temperature thermal conductivity to 0.0467 W/(m·K). A thermal insulation simulation validated the thermal insulation mechanism, showing that the optimized three-dimensional nanoscale pore network and dense Al₂O₃/SiO₂skeleton effectively retarded heat transfer, resulting in a steady-state cold surface temperature of 104 °C under a 400 °C thermal load. This work provided a novel strategy for designing lightweight, high-temperature-resistant aerogels with potential applications in insulation and catalyst support systems.