Metallic foams are often used to provide high strength with low weight. But a new series of experiments reveals that they’re far better at providing protection from heat than their solid counterparts, too.


Researchers from NC State have been testing metal foams in extreme conditions to see if they could be used for containing nuclear material or potentially explosive products. The foam in the picture—which is one they tested—is made from an a metallic alloy that’s cast around hollow metal spheres to provide voids.

Exposing a pure-steel foam with a structure like this to high heat from one side, the team found that it took four minutes for a 0.75-inch thick piece to reach 1,470 degrees Fahrenheit throughout. Meanwhile, a slab of plain steel took four minutes to reach the same temperature. “The presence of air pockets inside CMF make it so effective at blocking heat, mainly because heat travels more slowly through air than through metal,” explained Afsaneh Rabiei, one of the researchers, in a press release.


The team also found that the foam expands 80 percent less than solid metal as it reaches those high temperatures, and that expansion is much more consistent, too. “Our findings suggest that [metallic foam] can offer extremely good thermal insulation, superior thermal stability, and excellent flame retardant performances as compared to commercially available materials such as stainless steel,” the team said.

[International Journal of Thermal Sciences via PhysOrg]