High Temperature Resistant Calcium-doped Silica Aerogels with Enhanced Thermal Insulation via Sol-Gel Hydrothermal Route

doi:10.15541/jim20250113

Abstract

Abstract: Silica aerogel has a broad application in the field of high-temperature thermal insulation due to its low density, low thermal conductivity and high stability. However, its thermal insulation performance deteriorates significantly at elevated temperatures exceeding 600 ℃, primarily due to the collapse of pore structure. Meanwhile the shielding capacity of SiO₂ aerogel to the infrared radiation at high temperature is rather low due to the intrinsic properties of SiO₂. Herein, we explored to improve the high-temperature stability and infrared shielding properties of SiO₂ aerogel via Ca doping. Calcium-doped silica aerogel (CSA) powders were prepared by sol-gel, hydrothermal, and atmospheric pressure drying (APD) techniques using water glass and anhydrous calcium chloride as precursors and trimethylchlorosilane (TMCS) as a hydrophobic modifier. The effects of Ca/Si molar ratio in the precursor and hydrothermal conditions (temperature and pH) on the crystalline properties, microscopic morphology and pore structure of calcium-doped silica aerogels were investigated. The results show that the Ca/Si molar ratio and hydrothermal treatment have significant effects on the microstructure and heat resistance of calcium-doped silica aerogels in the temperature range of 400-1000 ℃. The samples sintered at 1000 ℃ have a high specific surface area of 100.1 m²/g and a pore volume of 0.8705 cm³/g, thereby indicating that the calcium-doped silica aerogel has good heat resistance. One-side insulation tests at temperatures up to 600 °C show that the sample with a Ca/Si molar ratio of 1.0 has the best insulation performance, with a cold surface temperature of 450 °C, which is 27 °C lower than that of the pure silica aerogel.

Key words: silica aerogel, calcium doping, high-temperature resistance, hydrothermal, ambient pressure drying

CLC Number:

TQ424

LI Hao, QI Yuan, GAO Xiangdong, ZHANG Xingxing, WANG Jinmin. High Temperature Resistant Calcium-doped Silica Aerogels with Enhanced Thermal Insulation via Sol-Gel Hydrothermal Route[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250113.

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