High-entropy alloys exhibit a broad light-responsive spectrum, spanning the ultraviolet to visible range, and their light absorption coefficient is significantly higher than that of traditional binary oxides. Cr/AlCrNbSiTiN/AlCrNbSiTiO gradient nano-multilayer coatings with excellent solar selective absorption properties are prepared using ion source enhanced magnetron sputtering. The effects of thickness of the absorption layer of AlCrNbSiTiN (3/4/5 min, denoted as S-3/4/5) are systematically investigated. It is worth noting that nano-multilayer coatings of S-3, S-4, and S-5 exhibit nearly perfect absorption rates of 0.9847, 0.9888, and 0.9879, respectively. The TEM images shows clear interfaces between the various coating layers, exhibiting a gradient structure that combines nanocrystalline and amorphous characteristics. From the substrate to the surface, there is an increase in the content of nanocrystalline phases, coarsening of grain sizes, and a decrease in the amount of amorphous phases. The primary absorption layer of AlCrNbSiTiN displays a typical face-centered cubic nitride structure. The XPS analysis reveals that the high-valent oxides (Nb⁵⁺, Cr⁶⁺) ensure thermal stability, whereas mixed valence states of Cr³⁺/Cr⁶⁺ may enhance visible light absorption through multi-electron transitions. This study analyzes how both the thickness of absorbing layers and high-temperature annealing affect the optical properties and photothermal conversion performance of AlCrNbSiTiN-based high-entropy coatings, which provides valuable insights for developing high-performance selective absorbers.

In extreme working conditions such as deep-sea and aerospace, failure due to friction and wear of key metal components is very frequent. Traditional binary or ternary nitride protective coatings are unable to achieve a coordinated improvement in terms of hardness, wear resistance, and structural stability. In this manuscript, a high-entropy composite nano-coating of CrWNbTaMoVSiN with an alternating structure of metal and nitride layers was prepared by using anode layer ion source-assisted magnetron sputtering technology. The influence of substrate bias voltage on the microstructure, phase structure, surface chemical state, friction and wear properties of coatings was systematically studied. The findings demonstrate that the substrate bias voltage has a substantial impact on the structure and performance of the CrWNbTaMoVSiN coatings. As the bias voltage increases, the coating deposition rate and thickness decrease, while the grain growth morphology gradually transitions from directionally aligned columnar crystals to equiaxed crystals. The primary phase of the coating is a solid solution with a face-centered cubic (FCC) crystal structure. At a bias voltage of 60 V, the coating exhibits a denser surface and cross-sectional microstructure, fewer structural defects, higher hardness, superior wear resistance, and enhanced electrochemical corrosion protection performance. This study provides critical experimental evidence and theoretical insights into the bias-voltage-dependent regulation mechanism of high-entropy nano-multilayer coatings, thereby supporting the process optimization of high-performance protective coatings and their engineering deployment under extreme service conditions.