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Researchers create ultra-light ceramic materials that withstand extreme temperatures



Optical image showing a sample of hBNAG based on a flower sting. Credits: X. Xu and X. Duan

UCLA researchers and staff at eight other scientific institutions have created an extremely lightweight, very durable ceramic aerogel. The material can be used for applications such as an isolation spacecraft, since it can withstand intense heat and strong temperature changes that withstand space missions.
Ceramic aerogels have been used to isolate industrial equipment since the 1

990s, and they have been used to isolate scientific equipment on NASA missions. But the new version is much stronger after the effects of extreme heat and repeated temperature adhesions, and much easier. Its unique atomic composition and microscopic structure also make it extremely elastic.

When heated, the material shrinks, not expands, as other ceramics do. It also contracts perpendicularly to the direction where it is compressed – imagine how to push a tennis table on the table, and the center of the ball moves inward, rather than expands – on the contrary, as most materials react with compression. As a result, the material is much more flexible and less fragile than a modern ceramic aerogel: it can be compressed to 5% of the original volume and completely restored, while other existing aerogels can only be compressed to 20% and then fully recover .

The research that was published today in Science was headed by Xiangfeng Duan, UCLA Professor of Chemistry and Biochemistry; Yu Huang, Professor of Materials Science and Engineering at UCLA; and Hui Lee from the Harbin Institute of Technology, China. The first authors of the study are Xiang Xu, who visits PhD in chemistry at UCLA from the Harbin Institute of Technology; Chiangqiang Zhang from Lanzhou University; and Menglong Hao from UC Berkeley and Southeast University.

Other members of the research team were from UC Berkeley; University of Purdue; Lawrence Berkeley National Laboratory; University of Hunan, China; University of Lanzhou, China; and the University of King Saud, Saudi Arabia

Despite the fact that more than 99 percent of their volume – the air, the aerogels are solid and structurally very strong for their weight. They can be made of many types of materials, including ceramics, carbon, or metal oxides. In comparison with other insulators, aerogels based on ceramics surpass the blocking of extreme temperatures, they are ultra-low density and have high resistance to fire and corrosion – all the qualities that are well suited for reusable spacecraft. Author: X. Xu and X. Duan

But the current ceramic aerogels are very fragile and tend to be destroyed after repeated exposure to strong heat and sharp temperature fluctuations, both of which are common in space travel. made of thin layers of boron nitride, ceramics, with atoms, which are connected to hexagonal structures, for example, in chicken wire

. It stood for hundreds of effects of sudden and extreme temperature adhesions, when engineers raised and lowered the temperature in the test container between minus 198 degrees Celsius and 900 degrees higher than zero for just a few seconds. In another test, it lost less than 1% of its mechanical strength after being stored for one week at a level of 1400 degrees Celsius




Thermal tests of ceramic aerogels. Posted by X. Xu and X. Duan

"The key to the durability of our new ceramic airgel is its unique architecture," Duan said. "Its innate flexibility helps to get hit by extreme heat and temperature shocks that can lead to the failure of other ceramic aerogels." Over time, these repeated temperature changes can lead to the destruction of these materials and, ultimately, to their failure. The new airgel has been designed in such a way to be more durable when it works on the contrary – it is reduced, but not expanding when heated. Surviving repeated and rapid temperature changes. (This property is known as the Poisson's negative coefficient.) It also has internal "walls" that are reinforced by a double structure, which reduces the weight of the material with increasing its insulating ability. to make a new airgel can also be adapted for the production of other ultra-light materials.

"These materials may be useful for thermal insulation in spacecraft, cars or other specialized equipment," he said. "They can also be useful for storing thermal energy, catalysis or filtration."


Explore further:
Rubber carbon aerogels significantly expand the application

Additional information:
X. Xu el al., "Double negative index of ceramic aerogels for thermal supylation" Science (2019). science.sciencemag.org/cgi/doi… 1126 / science.aav7304

Reference of the journal:
Science

Granted:
University of California, Los Angeles


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