High-Temperature Resistance, Lightweight, and Thermally Insulating Silica Aerogel via Doping Hollow Silica Nanoparticles

Pure silica (SiO2) aerogels are highly susceptible to sintering and nanopore collapse at elevated temperatures, which limits their thermal stability. Traditional solutions to this issue, such as doping with opacifiers or fibers, often increase thermal conductivity and density. To increase the thermal stability of standard aerogels comprising small full-density SiO2 nanoparticles (SFPs) (typically 2–15 nm in diameter), SiO2 aerogels were doped with large hollow SiO2 nanoparticles (LHPs) with diameters of 100–250 nm. In situ transmission electron microscopy heating experiments were performed to observe the sintering behavior of SFPs and the antisintering properties of LHPs. At 1000 °C, LHPs with diameters of >120 nm and thicknesses of >22 nm retained their structural integrity, whereas substantial sintering was observed in the standard SFPs. Transient nanoparticle structural evolution was used to investigate the mechanisms underlying these phenomena. The results were validated using molecular dynamics simulations, which showed excellent agreement with the experimental results. Compared with SiO2 aerogels doped with Al2O3–SiO2 or zirconia fibers, the LHP-doped SiO2 aerogels (0.1 wt % LHPs) exhibited remarkable performance improvements. A 71% reduction in density was achieved under ambient conditions. Furthermore, at 1100 °C, thermal conductivity decreased by 34.4%, and the density was only 242 kg/m3, the lowest density among SiO2-based aerogel composites. This effectively overcomes the conventional trade-off among high-temperature resistance, thermal insulation, and low density. This study presents a cost-effective and resource-efficient approach for developing lightweight thermal insulation materials for high-temperature applications.