A flexible silica aerogel paper with temperature-switch opacifier for thermal insulation

Aerogels have an impressive thermal insulation performance at room temperature. However, with high infrared transmittance, pure aerogels have no advantages in thermal insulation at high temperature. Opacifiers can reduce infrared transmittance to make a low thermal conductivity with sacrifice of that at room temperature. Herein, VO₂ powders undergoing reversible insulator to metal transition at 67.8 °C as opacifier with temperature-switch were introduced into silica aerogel composites to prepare aerogel reinforced by VO₂@SiO₂ fibers paper (AVSP). At 25 °C, insulator VO₂ made little contribution to thermal conductivity (0.025 W/(m·K)) so that it was close to aerogel reinforced by pure SiO₂ fibers papers without opacifier (0.023 W/(m·K)). When temperature rose to 500 °C, metal VO₂ made thermal conductivity of AVSP (0.051 W/(m·K)) much lower than that of aerogel reinforced by pure SiO₂ fibers papers without opacifier (0.076 W/(m·K)). Meanwhile, SiO₂ fibers papers with three-dimensional network structure improved flexibility of aerogel. The tensile strength of AVSP was 2.1 MPa with density of 0.186 g/cm³. With 152° contact angle and flame resistance, AVSP showed a great potential in high temperature thermal insulation in a nonplanar condition. Thereby, this work provides a novel strategy to improve thermal insulation property at high temperature with little contribution to that at room temperature.