Ultra-Lightweight Ceramic Withstands Extreme Temperatures

Breath mint-sized samples of the ceramic aerogels. The material is 99% air by volume, making it very lightweight. Photo by Oszie Tarula, UCLA.

A collaborative research project led by the University of California, Los Angeles (UCLA) (Los Angeles, California, USA) and eight other institutions has developed a durable, lightweight ceramic aerogel. They say the material could be used for applications such as insulating spacecraft, because it can withstand intense heat and severe temperature changes.

Though more than 99% of their volume is air, aerogels are solid and structurally strong. They can be made from many types of materials, including ceramics, carbon, or metal oxides. Compared with other insulators, the researchers say ceramic-based aerogels are superior in blocking extreme temperatures, and they have ultra-low density while offering strong resistance to fire and corrosion.

While these ceramic aerogels have been used to insulate industrial and scientific equipment since the 1990s, the researchers believe their new version is lighter and more durable after exposure to extreme heat and repeated temperature spikes. They say its unique atomic composition and microscopic structure also make it unusually elastic.

When heated, the material contracts rather than expanding. It contracts perpendicularly to the direction it is compressed, which they say is the opposite of how most materials react. As a result, the material is more flexible and less brittle than current ceramic aerogels. According to the researchers, it can be compressed to 5% of its original volume and fully recover, whereas existing aerogels can only be compressed to about 20% to fully recover.

The new material is made of thin layers of the ceramic boron nitride (BN), with atoms that are connected in hexagon patterns. In tests, the ceramic withstood conditions that researchers say would typically fracture other aerogels. For instance, it stood up to hundreds of exposures to sudden and extreme temperature spikes when engineers raised and lowered the temperature in a container between -198 °C and 900 °C within seconds. In another test, it lost less than 1% of its mechanical strength after being stored for one week at 1,400 °C.

The research team says the aerogel process could be adapted to make other ultra-lightweight materials. “Those materials could be useful for thermal insulation in spacecraft, automobiles, or other specialized equipment,” says Xiangfeng Duan, research leader and a UCLA professor of chemistry and biochemistry. “They could also be useful for thermal energy storage, catalysis, or filtration.”

Source: UCLA, chemistry.ucla.edu.