Novel silica-modified boehmite aerogels and fiber-reinforced insulation composites with ultra-high thermal stability and low thermal conductivity

Abstract

Alumina–silica composite aerogels have drawn vast attention due to their enhanced thermal stability compared to pristine alumina aerogels. However, they are generally weakly-crystallized and tend to experience inevitable sintering and significant surface area loss especially above 1200 °C. In this study, we developed a hydrothermal treatment and supercritical drying strategy for synthesizing novel, well-crystallized, silica-modified boehmite aerogels and fiber-reinforced composites. For the prepared aerogel, network coarsening was significantly hindered and the α-Al2O3 transition was completely prevented even at 1400 °C. As a result, the aerogel exhibits extremely high surface area maintenance (87 % and 53 % after 1300 °C and 1400 °C calcination, respectively) and low linear shrinkage (14 % after 1300 °C calcination) at elevated temperatures. The composite with good toughness shows excellent heat resistance and thermal insulating performance up to 1500 °C. These findings provide a general, direct new idea to improve the thermal tolerance of alumina-based aerogels and extend their applications to higher temperatures.