Double-negative-index ceramic aerogels for thermal superinsulation

Abstract

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 × 10−6 per °C). Our aerogels display robust mechanical and thermal stability and feature ultralow densities down to ~0.1 milligram per cubic centimeter, superelasticity up to 95%, and near-zero strength loss after sharp thermal shocks (275°C per second) or intense thermal stress at 1400°C, as well as ultralow thermal conductivity in vacuum [~2.4 milliwatts per meter-kelvin (mW/m·K)] and in air (~20 mW/m·K). This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.

Transformation Omnithermotics: Simultaneous Manipulation of Three Basic Modes of Heat Transfer

“…As experimental demonstrations, one may resort to the heat transfer in aerogels. 5 The carrier of convective flux can be either fluids or gases in aerogels. We can also use multilayered structures 10 to realize anisotropy and inhomogeneity.…”

“…For example, solar vapour generation [1][2][3][4] is a typical system which contains the three basic modes of heat transfer: The utilization of solar energy is related to radiation, the evaporation of seawater is associated with convection, and conduction exitsin almost each process. Another typical example is the heat transfer in aerogels 5 where the basic three modes of heat transfer should also be taken into consideration. On all accounts, the underlying physics is the simultaneous manipulation of conduction, convection, and radiation, which is of particular significance for thermal management.…”

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

“…Ceramic aerogels based on SiO 2 , [ 74 ] Al 2 O 3 , [ 75 ] SiC, [ 76 ] and BN [ 77 ] have been widely investigated due to their light weight, low thermal conductivity, high refractoriness, and corrosion resistance. As a well‐known example, thermal insulation systems of extraordinarily high performance have been achieved on the basis of silica aerogels and emerging as the first significantly commercialized aerogel materials.…”

Boron nitride aerogels consisting of varied superstructures

“…Besides the above routes, employing other aerogels as templates was also explored, which adds to the diversity of BN aerogel microstructures and unlocks their high temperature applications. [21][22][23][24][25] However, template deposition may only serve as a short-term expedient. More recently, efficient fabrication of BN aerogels with nanoribbon-tangled networks was also achieved.…”