Greatly enhanced anticorrosion of Al–AlNxOy nanocermet films with self-passivated Al nanoparticles for enduring solar-thermal energy harvesting

Metal-dielectric (cermet) solar selective absorber coatings (SSACs), in which metal NPs are embedded in dielectric matrices, have been widely used in photothermal conversion field which is due to their strong broadband absorption characteristics. However, metal nanoparticles (NP) always possess some inherent activity (i.e. diffusion, agglomerate and oxidation) to reduce their surface energy. Therefore, the cermet-based SSACs are not corrosion-resistant and poor thermal stability. Here, the Al NPs was selected as doped metal, and AlNxOy as dielectric matrices, with the aid of self-passivating Al NPs by the newly formed Al-enriched AlxOy/Al2O3/AlxOy(OH), the Al–AlNxOy SSACs possess unprecedented anticorrosion and outstanding thermal stability (up to 400 °C). The corrosion tolerance significantly surpasses those of reported commercial and laboratorial films. The film still displayed a desirable solar absorptance (0.924) and a low thermal emissivity (0.116) after 5.0 wt % NaCl salt spray for 2000 h. More importantly, the Al–AlNxOy SSACs is simple, cost-effective, which is very suitable for large scale production. A self-developed industrial-scale air-to-air sputtering line was fabricated for continuous production of Al–AlNxOy SSACs on 1000 mm wide aluminum strip. With above high-performance, Al–AlNxOy SSACs are promising absorbers for enduring photothermal utilization in high-salinity environments.