Superinsulation

A ceramic aerogel is light enough to be supported by the stamen of a flower.

X. Xu and X. Duan

Insulation on spacecraft must not only shield the vessel from the profound cold of space, which registers around -270°C, but also endure extreme temperature spikes. Insulating materials called aerogels, like those currently used on Mars rovers, are able to provide effective temperature protection but are prone to brittleness and degradation following exposure to big temperature swings. Now, scientists have developed a ceramic aerogel material that is more durable than existing insulators.

Xiangfeng Duan, a professor of chemistry and biochemistry at the University of California, Los Angeles, led a team of researchers to synthesize a new insulating material built out of boron nitride, a kind of ceramic whose constituent atoms link up hexagonally, bearing a resemblance to chicken wire. The material is more than 99 percent air by volume. The thin layers of its internal microstructure are double-paned, reducing overall weight but still offering excellent strength.

The new ceramic aerogel uniquely shrinks upon heating, unlike most ceramics, which expand when heated. Upon compression, the material contracts into itself, rather than spreading out laterally. Duan notes that these properties “endow exceptional mechanical stability and thermal stability for superinsulation under extreme conditions.”

The researchers subjected their new aerogel to a battery of tests. They built a special chamber that could rapidly fluctuate temperatures from –198 to 900°C, over just a few seconds span. The aerogel retained its structural stability through hundreds of these temperature change cycles. Roasting the aerogel for a week at 1400°C resulted in a mere 1 percent reduction in its mechanical strength.

The material showcased flexible resiliency as well. Currently available aerogels can collapse to about 20 percent of their original volume and still return to their initial state. The new material, however, can be crushed to 5 percent of its original volume and still fully rebound.

The next challenge for the material’s development is to realize large-scale production in a cost-effective manner, said Duan. If the scientists can figure that out, a next generation of space-exploring craft, along with such terrestrial applications as car engines and thermal storage, could receive insulation upgrades. (Science)