Double-Negative-Index Ceramic Aerogels For Thermal Superinsulation

Summary:

UCLA researchers in the Departments of Chemistry and Biochemistry and Materials Science and Engineering have developed a novel ceramic aerogel material that has robust mechanical and thermal stability under extreme conditions.

Background:

Thermal insulation used in industries like aerospace and thermal power fields requires resistance to rapid temperature changes and long-term high-temperature exposure. Ceramic aerogels are appealing for thermal insulation due to their low density, low thermal conductivity, and exceptional fire/corrosion resistance. However, ceramic aerogels can be brittle and suffer structural collapse upon exposure to prolonged high-temperature or large thermal gradients. Prior strategies to improve structural stability have employed flexible amorphous, one-dimensional fibrous materials, but these ceramic aerogels still break down under extreme conditions. There is significant motivation to create alternative constructs with improved ceramic strength to maintain thermal and mechanical stability.

Innovation:

UCLA researchers have developed a ceramic aerogel material that has increased mechanical and thermal stability under large thermal gradients or extended high-temperature exposure. The material is protected from strength degradation and structural collapse in extreme environments. Its structural stability relies on a unique fibrous/film hybrid meta-structure that exhibits a negative Poisson’s ratio and negative thermal expansion coefficient, in contrast to ceramic aerogels with one-dimensional fibrous structures. The novel ceramic aerogel displays ultralow density (~0.1 mg/cm3), superelasticity (up to 95%), and thermal superinsulation (~2.4 mW/m K in vacuum and ~20 mW/m K in air). The material is able to withstand sharp thermal shocks (~275 ℃/s) and long-term temperature exposures (1,400 ℃ in vacuum and 900 ℃ in air), which is significantly improved compared to other ceramic aerogels.

Patent Status:

Application filed: WO2020167442A1

Potential Applications:

Thermal superinsulation under extreme conditions, such as in aerospace and thermal power fields
Mechanical stability under rapid temperature changes and long-term high temperature exposure

Advantages:

Ultra-low density (~0.1 mg/cm3)and super lightweight compared to other ceramic aerogels
Thermal superinsulation beyond typical aerogels
Near-zero strength loss under rapid thermal shocks and extended high temperature exposure
Enhanced torsion flexibility and superelasticity of compression (up to 95%) that exhibits highest deformability

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