Enhancing particle heat resistance of the silicon-oxygen network skeleton in silica aerogel via Y/Yb dual-doping for thermal insulation

SiO₂ aerogels are nanoporous thermal insulation materials composed of a network of interconnected nanoparticles, but they are easy to crack and collapse above 800 °C which resulting in failure of thermal insulation. To improve the temperature resistance of nanoparticles, rare earth elements yttrium (Y) and ytterbium (Yb) were introduced as an enhancement system by sol-gel method to change the chemical interaction on the chemical structure and molecular bonding, together with improving the thermal stability. TEOS as the silicon source, yttrium nitrate and ytterbium nitrate as the rare earth sources, aerogel material with a density of 0.0904 g/cm³ was prepared by adjusting the finally chosen molar ratio of Si:Y:Yb = 1:0.05:0.05. By investigating the influence of RE on the microstructure, Y and Yb were found to be involved in the molecular bonding forming Si-O-Y and Si-O-Yb and changing the surface of primary particles. The thermal stability showed that the phase transition process after 573 °C was greatly inhibited by the introduction of single or dual RE. By analyzing the high temperature microstructural evolution, the shrinkage was decreased 25 % when at 1200 °C. The Cristobalite phase above 1200 °C was inhibited due to the Y/Yb dual-doping system. Furthermore, the decomposition stability was enhanced and the crack formation was significantly reduced at 1000 °C with thermal conductivity reducing from 0.2111W/(m·K) to 0.1187 W/(m·K) after heat treatment at 1000 °C.