This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers have engineered a new material that is an extreme thermal insulator, is exceptionally stiff and can be printed as a thin film at large scales. The material has one of the lowest thermal conductivity profiles of any dense, or nonporous, material—approaching the theoretical limit of how good a material can be as a thermal insulator.
"Stiff materials that are good thermal insulators would have substantial utility in a variety of applications, from cookware to electronic devices to space travel," says Dali Sun, co-corresponding author of a journal article on the work and a professor of physics at North Carolina State University. "But this is a significant challenge," Sun says. "Because, in general, stiff materials are good at conducting heat, and materials that are not stiff are good at insulating against heat.
We've created a material that is very stiff and is extremely good at insulating against heat. Better than any material you would find in nature." "We had previously demonstrated unusual behavior related to the combination of stiffness and thermal conductivity in a specific class of materials," says Jun Liu, co-corresponding author and an associate professor of mechanical and aerospace engineering at NC State. "For this work, we engaged in more advanced molecular engineering to intentionally create an extreme combination of those properties." The paper, "Extremely Low Thermal Conductivity in Rigid Layered Hybrid Perovskites," will be published Sept. 18 in the journal Science Advances.
The researchers worked with a subset of the class of materials called two-dimensional hybrid organic-inorganic perovskites. These are thin-film semiconductors consisting of alternating organic and inorganic layers with a highly ordered crystalline structure. By replacing some of the carbon-carbon chains in the organic layers with a tailored combination of benzene rings, the researchers can control the stiffness and thermal conductivity of the materials.
Specifically, the researchers made an azobenzene ethyl ammonium lead iodine thin film. When the researchers tested it, they found that the material had a thermal conductivity of approximately 0.04 W m-1 K-1 at room temperature. To put that in context, this stiff material has a thermal conductivity that is five times lower than silicone—which has a thermal conductivity of 0.2 W m-1 K-1.
Silicone is used to insulate against heat in applications such as oven mitts. "So, if we want to compare this material to silicone, the material we made is 700–10,000 times stiffer than silicone and five times better at insulating against heat," says Liu. "And the method we used to produce this material can be scaled up fairly easily," says Liu.
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