Double-negative-index ceramic aerogels for thermal superinsulation

Ceramic aerogels are attractive for thermal insulation but plagued by poor mechanical stability and degradation under thermal shock. In this study, we designed and synthesized hyperbolic architectured ceramic aerogels with nanolayered double-pane walls with a negative Poisson's ratio (-0.25) and a negative linear thermal expansion coefficient (-1.8 x 10(-6) per degrees C). Our aerogels display robust mechanical and thermal stability and feature ultralow densities down to similar to 0.1 milligram per cubic centimeter, superelasticity up to 95%, and near-zero strength loss after sharp thermal shocks (275 degrees C per second) or intense thermal stress at 1400 degrees C, as well as ultralow thermal conductivity in vacuum [similar to 2.4 milliwatts per meter-kelvin (mW/m.K)] and in air (similar to 20 mW/m.K). This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.