SiOC nanospheres reinforced silica aerogel with excellent compatibility and excellent thermal insulation under high temperature conditions

Silica aerogel is a unique nanomaterial with three-dimensional nano-porous networks. However, the microstructures of aerogels are easily damaged at high temperatures environment, weakening the thermal insulation performance. In this work, we prepared thermally stable SiOC nanospheres and then composited them with aerogel matrix. SiOC nanospheres and aerogel matrix have excellent compatibility. SiOC nanospheres can induce the aerogel matrix forming island microstructures after drying process. The presence of the island microstructure leads to a reduce of the inter-skeleton macropore size, which declines from 4.77 μm to 2 μm. The thermal conductivity decreases from 0.0813 to 0.0646 W/ (m K). The volume shrinkage and density also show a clear downward trend. In order to investigate the impact of high-temperature to thermal insulation performance, the aerogel composites are experienced different high-temperature treatment. The results demonstrate that the island microstructure of aerogel is transformed into a spherical shape after high-temperature treatment. The particle diameter increases from 5 μm to 5.7 μm when treated in 200 °C and 400 °C. Upon 400 °C, the diameter reduces from 5.7 μm to 4.4 μm at 800 °C. The variety in the size of the aerogel skeleton particles results in a reduction in the pore diameters of the interskeleton pores from 8 to 3.8 μm. The thermal conductivity decreases from 0.0667 to 0.0466 W/ (m K) treating below 400 °C and increases to 0.0712 W/ (m K), when heat treatment temperature is 800 °C. The enhancement of thermal insulation performance is attributed to the decline of macropores content between skeletons caused by swelling of aerogel particles. The diameters of macropores between skeletons reduce, which can effectively weaken the influence of gaseous heat transfer. This work provides a reference for the preparation of aerogel composites that can maintain excellent thermal insulation properties in high-temperature environment.

Graphical Abstract