Ultrafine silica aerogels microspheres for adaptive thermal management in large-temperature-fluctuation environment

A large number of areas on earth is suffered from large-temperature fluctuation (LTF) during the days or over the seasons. However, current strategies for adaptive thermal management in the LTF environment are limited. In this study, we developed a simple and cost-effective strategy to synthesize ultrafine and nearly monodispersed silica aerogel microspheres (SAM) with an average diameter of 1.9 μm. The aerogels possess low thermal conductivity of 0.039 W·m−1·K−1 and can preserve heat by reducing heat dissipation in cold environments. Meanwhile, IR emissivities range from 0.13 to 0.98 and a relatively high solar reflectance of 0.65, leading to an impressive sub-ambient cooling of 9.1 °C in a hot daytime. Additionally, a theoretical carbon emission analysis of the aerogels' daytime cooling and night warming suggests a carbon emission reduction of 13.6 tCO2 eq. This study develops a strategy to synthesize ultrafine SAM and provides a strategy for passive cooling and passive warming by SAM with the combination of passive cooling and thermal insulation, which could help to achieve global carbon neutrality and sustainability, and solve the problems of thermal management with large temperature-fluctuation.