Infrared Stealth Coating with Tunable Structural Color Based on ZnO Spheres

It is important to develop low infrared (IR) emissive coating with tunable structure color to improve the infrared-visible stealth performance of military equipment. In this work, uniform ZnO spheres are used as building units to construct photonic structures with both bright adjustable structure color and low IR emissivity due to the relatively high refractive index and low IR emissivity of ZnO. The vivid tunable structural colors are provided by the photonic bandgap of ZnO photonic crystals (PCs) or the quasi-bandgap of amorphous photonic crystals (APCs), respectively. Both ZnO PCs and APCs exhibited low IR emissivity in 3-5 µm. The IR emissivity of 255 nm ZnO PC is 0.483 and the IR emissivity of 255 nm ZnO APC is 0.492 at 25 °C. With the increase of temperature, the IR emissivity of further decreased to 0.295 and 0.312 at 300 °C. These structures can be applied to a variety of surfaces, and all these structures have good thermal and light stability as well. This work may open a simple and effective way to fabricate materials with good infrared-visible stealth performance, expanding the application of ZnO PCs and APCs coatings in the camouflage area.