New thermal insulator outperforms any material found in nature

Scientists have long faced a fundamental trade-off in materials science: rigid materials typically conduct heat efficiently, while substances that resist heat flow tend to be soft or flexible. A research team has bypassed this limitation by engineering a dense, nonporous thin film that combines exceptional stiffness with an extremely low thermal conductivity profile, approaching the theoretical limit of insulation performance.

According to Phys.org, the findings were published on September 18 in the journal Science Advances under the title Extremely Low Thermal Conductivity in Rigid Layered Hybrid Perovskites. The work demonstrates that advanced molecular engineering can intentionally merge structural rigidity with thermal resistance far beyond what occurs naturally.

Two-Dimensional Hybrid Organic-Inorganic Perovskites

The research focuses on a subset of materials known as two-dimensional hybrid organic-inorganic perovskites. These semiconductors feature alternating organic and inorganic layers arranged in a highly ordered crystalline structure. To control both stiffness and thermal transport, the team altered the organic layers.

Researchers replaced specific carbon-carbon chains within the organic layers using a tailored combination of benzene rings. This specific substitution yielded an azobenzene ethyl ammonium lead iodine thin film. Dali Sun, a professor of physics at North Carolina State University and co-corresponding author of the study, explained the breakthrough nature of the material.

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.

NC State honors astronaut Christina Koch with building name, ice cream flavor

Dali Sun, professor of physics at North Carolina State University

Jun Liu, an associate professor of mechanical and aerospace engineering at NC State and co-corresponding author, noted that the team intentionally targeted this extreme combination.

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.

Jun Liu, associate professor of mechanical and aerospace engineering at NC State

Azobenzene Ethyl Ammonium Lead Iodine Thin Film

When tested at room temperature, the newly engineered azobenzene ethyl ammonium lead iodine thin film recorded a thermal conductivity of approximately 0.04 W m-1 K-1. To put that metric in perspective, traditional silicone—widely used for heat insulation in household items like oven mitts—has a thermal conductivity of 0.2 W m-1 K-1.

This means the newly developed thin film blocks heat five times more effectively than silicone. At the same time, the material is vastly stiffer. According to Liu, the engineered compound is between 700 and 10,000 times stiffer than silicone.

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.

Jun Liu

North Carolina State University

Beyond its physical performance, the manufacturing process offers practical advantages for industrial implementation. The synthesis method allows the material to be produced at large scales and applied directly as a thin-film coating.

And the method we used to produce this material can be scaled up fairly easily, says Liu. You can produce it at fairly large scales, apply it as a coating, and so on.

Jun Liu

Liu emphasized the operational potential of the production technique, stating that the research team is excited because the work highlights the potential of molecular engineering to fine-tune these hybrid layered materials for use in applications that require novel combinations of stiffness and thermal insulation.