The experimental film combines stiffness with strong thermal insulation without relying on pores or softness. The lead-containing material is undergoing tests for possible coating uses.
Researchers at North Carolina State University in the US have made a dense film that combines mechanical stiffness with very low heat conduction. The result addresses a difficult materials problem: rigid solids generally conduct heat well, while good insulators such as foams and aerogels are softer.
Physics World described the experiments, published in Science Advances. The team studied spin-coated films of azobenzene ethyl ammonium lead iodide, a hybrid perovskite built from alternating organic and inorganic layers.
| Property | Measurement | What it measures |
|---|---|---|
| Thermal conductivity | 0.04 watts per metre per kelvin (W/m/K), at room temperature | How readily heat passes through a material; a lower value means better insulation. |
| Elastic modulus | 7.7 gigapascals (GPa) | Stiffness: how strongly a material resists changing shape under a force. |
Analysis
Mechanical and aerospace engineer Jun Liu co-led the study with physicist Dali Sun. Liu said the central challenge was to achieve extremely low heat conduction in a dense, rigid material, rather than relying on pores, voids or structural softness.
The proposed explanation centres on phonons: vibrations of a crystal’s atomic structure that carry heat. The repeating organic and inorganic layers slow the movement of these vibrations.
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The researchers also engineered organic cations—positively charged organic molecules—with two aromatic rings joined by a double-bond linkage. They describe these molecules as increasing stiffness while making the stacking of the inorganic layers less orderly, further restricting heat transport.
The measurements establish properties of an experimental film, not its performance as a practical coating. The team is testing the thin film for coating applications. Liu also said the researchers plan to replace its lead with other, non-toxic metals.
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