Optimized Optical and Thermal Properties of Al-Pigmented Low-Emissivity Coatings by CuCr2O4 Powder

To reduce the lightness and enhance the thermal resistance of Al-pigmented low-emissivity coatings, CuCr2O4 pigment was introduced into the coating system via ball milling. The results revealed that both ball milling time and Al: CuCr2O4 mass ratio significantly affect the optical and infrared properties of the coatings. When the milling time reached 9 h, the pigment attained an optimal flake morphology, leading to the best infrared performance of the composite coating. Additionally, the CuCr2O4 content effectively suppressed the lightness of Al-pigmented coatings. Compared to Al-pigmented low-emissivity coatings, the composite coating with an Al:CuCr2O4 ratio of 10:2 exhibited a reduction in L* value from 90 to 65. Meanwhile, it retained a low average infrared emissivity of 0.42 in the 3–5 μm and 8–14 μm ranges. Moreover, the incorporation of CuCr2O4 significantly improved the Al-pigmented coating’s thermal resistance from 500 °C to 600 °C. The composite coating maintained a Grade 1 adhesion rating with heat treatment of 600 °C due to a self-healing effect. These composite coatings with low emissivity, low lightness, and high-temperature resistance are highly suitable for high-temperature and infrared stealth applications.