Preparation of Hydrophobic Silica Aerogel with High Thermal Stability by Argon Atmosphere Heat Treatment

Improving the thermal stability of silica (SiO₂) aerogel plays a crucial role in expanding its heat insulation application. In this work, heat treatment in argon atmosphere was adopted to avoid the thermal oxidative decomposition of hydrophobic groups, which inevitably occurred in the heat treatment in air atmosphere. Also, the physicochemical properties were analyzed. The results show that the hydrophobicity of SiO₂ aerogels still maintains at a contact angle of 140° after heat treatment in argon atmosphere at 700 ℃. In the differential scanning calorimetry test in air atmosphere, the peak temperature in exothermic reaction (T_peak) of heat treated SiO₂ aerogels reaches 584 ℃, which is approximately 300 ℃ higher than that of untreated SiO₂ aerogels, thus improving the thermal stability. The results obtained also indicate that hydrophobic SiO₂ aerogels could be used at high temperatures due to the improved thermal stability and safety.