24 May 2019
Super light space-age insulation
Published online 14 February 2019
An insulating material that can withstand rapid temperature changes without fracturing could have many aerospace applications.
Lightweight insulating materials are vital for spacecraft and other industrial applications to protect vulnerable contents and people from extreme temperatures. Without heat shield insulation, a spacecraft returning to Earth would burn up in the atmosphere.
Now, an international team of scientists, including Xiangfeng Duan and Yu Huang at the University of California, USA, with Hui Li at the Harbin Institute of Technology in Harbin, China, and Imran Shakir at King Saud University in Saudi Arabia, has developed a novel form of ceramic aerogel — an extremely lightweight, robust insulator — that does not lose structural stability under temperature stresses.
Existing aerogels are lightweight and resistant to fire and corrosion, but they are often brittle and fail structurally under extreme temperatures.
Duan and co-workers created latticed nanosheets of hexagonal boron nitride from engineered graphene templates. They designed the nanosheet structure to ensure the material did not bulge outwards under pressure or significantly change its shape and volume under thermal shocks. Their resulting aerogel has such low density it is almost weightless in air.
The researchers exposed the aerogel to long-term temperatures of up to 1400ºC in a vacuum, and rapid shocks such as heating it to 900ºC before pushing the temperature down to -198ºC in just four seconds. The material retained its strength and structure every time.
“This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft,” say the authors in their paper published in Science.
Xu, X. et al. Double-negative-index ceramic aerogels for thermal superinsulation. Science 363, 723–727 (2019).