A ceramic airgel made from nanocrystals and embedded in a matrix for thermal insulation applications.

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Nature (2022). DOI: 10.1038/s41586-022-04784-0″ width=”800″ height=”530″/>

Multi-scale design of a hypocrystalline ceramic nanofiber airgel. (a) Deformation modes and corresponding ν and α of crystalline (C), amorphous (A), and hypocrystalline (H) ceramic fibrous cells under mechanical and thermal effects. The color bar on the scale indicates the change in ceramic from amorphous to crystalline using a fingerprint based on local entropy to characterize the crystallinity of each atom in the simulated system. b – Illustration of a zigzag architecture based on hypocrystalline fiber ceramics. The units of the colored bars on the scale are millimeters, representing the absolute values ​​of the offset in the ν and α calculations. Triangular, square and pentagonal cells are the building blocks for assembling the fibrous structure of the airgel. Credit: Nature (2022). DOI: 10.1038/s41586-022-04784-0

A team of researchers from the Harbin Institute of Technology in China, together with a US colleague, has developed a new type of airgel for use in flexible thermal insulation materials. In his article published in the journal Naturethe group describes how they made their airgel and how well it performed under high heat.

Previous work has shown that aerogels made from ceramic materials work very well as thermal insulators—their very low density has very low thermal conductivity. But such materials are brittle, making them unsuitable for use in flexible materials such as firefighter suits. They also tend to break down when exposed to very high temperatures. In this new work, the researchers have developed a method for making a ceramic-based airgel that can be used in flexible applications and also does not break down when exposed to very high temperatures.

To create their airgel, the researchers used a novel approach – they pushed a zirconium-silicon precursor with a plastic syringe into a chamber with turbulent airflow – an electrospinning approach that resulted in a cotton candy-like ceramic material. Then they folded the resulting material in a zigzag pattern and heated it to 1100°C. Such heating changed the texture of the material from a glassy state to a nanocrystal. The study of the resulting material using a spectroscope showed that their approach led to the creation of a material with nanocrystalline particles embedded in a matrix of amorphous zircon, a flexible airgel made of ceramic that is not prone to fracture at high temperatures.

The researchers tested the material by using it to insulate an aircraft fuel pipe and applying a butane blowtorch for five minutes. They found that using a conventional polyimide barrier allowed the temperature in the tube to reach 267°C, while the conventional airgel kept the temperature at 159°C and the new gel kept it at just 33°C. They also found that the material was flexible enough to be used in flexible fabrics such as those used to make protective clothing for firefighters.

Airgel-integrated wood provides better insulation than existing plastic-based materials.

Additional Information:
Jingran Guo et al. Hypocrystalline ceramic aerogels for thermal insulation under extreme conditions. Nature (2022). DOI: 10.1038/s41586-022-04784-0

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