Multiscale hypocrystalline ceramic nanofiber airgel design. a, Strain modes and the corresponding ν and α of crystalline (C), amorphous (A), and hypocrystalline (H) ceramic fiber cells under mechanical and thermal excitation. The colored scale bar indicates the variation of ceramics from amorphous to crystalline by using a local entropy-based fingerprint to characterize the crystallinity of each atom in the simulated system. b, Illustration of zigzag architectural design based on hypocrystalline fiber ceramic. The units of the colored scale bars are millimeters, representing absolute displacement values in the ν and α calculation. The triangular, square and pentagonal cells are the building blocks for assembling the fibrous airgel structure. Recognition: Nature (2022). DOI: 10.1038/s41586-022-04784-0
A research team at the Harbin Institute of Technology in China, in collaboration with a colleague in the US, has developed a new type of airgel for use in flexible thermal insulation material applications. In her article published in the journal Naturethe group describes how they made their airgel and how well it performed when extreme heat was applied.
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 material applications such as firefighter suits. They also tend to degrade when exposed to very high temperatures. In this new attempt, the researchers have developed a method to produce a ceramic-based aerogel that can be used in flexible applications and does not break down even when exposed to very high temperatures.
To make their airgel, the researchers used a novel approach – they pushed a zirconium-silicon precursor into a turbulent airflow chamber with a plastic syringe – an electrospinning process that produced a ceramic material resembling cotton candy. They then folded the resulting material into a zigzag pattern and heated it to 1100°C. Heating in this way changed the texture of the material from a glassy state to a nanocrystal. Examination of the resulting material with a spectroscope showed that their approach had led to the creation of a material with nanocrystalline bits embedded in an amorphous zirconium matrix – a flexible airgel made from a ceramic that didn’t tend to withstand high temperatures to decay.
The researchers tested the material by using it to insulate an airplane fuel hose and blowing it with a butane blowtorch for five minutes. They found that by using a generic polyimide barrier, the temperature in the tube could reach 267°C, while a conventional airgel maintained the temperature at 159°C and the new gel at just 33°C. They also found that the material was flexible enough to allow it to be used in flexible cloths, such as those used to make protective clothing for firefighters.
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Jingran Guo et al, Hypocrystalline Ceramic Aerogels for Thermal Insulation in Extreme Conditions, Nature (2022). DOI: 10.1038/s41586-022-04784-0
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Citation: A ceramic airgel made with nanocrystals and embedded in a matrix for use in thermal isolation applications (2022, July 1), retrieved July 3, 2022 from https://phys.org/news/2022-07-ceramic-aerogel -nanocrystals-embedded-matrix.html
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