Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The in-air stability of a novel solar absorber coating type based on aluminium titanium oxynitride nanocomposites deposited by Physical Vapour Deposition is studied up to temperatures of 800ºC. The microstructural and morphological characterization by high resolution electron microscopy and glancing angle X-ray diffraction reveals the creation of a nanocomposite structure formed by crystalline AlTiN nanoparticles inserted in an oxide matrix. This nanocomposite structure (nc-AlTiON) is responsible of the high absorption within the whole solar wavelength range (0.3-25 µm) that the absorber exhibits. The as-deposited absorber has solar absorptance, α, of 92% and room temperature emissivity, ε _RT, of 70%. The deposition of an antireflecting Al₂O₃ layer lowers the reflectance of the sample in the UV-Vis-NIR region and, consequently solar absorptance increases up to 93.5%. Post-deposition thermal treatments of 2 hours at 800ºC further improve the solar absorptance and emissivity of the absorber (α=96%, ε_RT=60%). Thus, this nc-AlTiON/Al₂O₃ coating presents solar performances that match, within the experimental errors, the ones calculated for the commercial absorber paint Pyromark® at C=1000 (typical of central tower receivers) or even surpass it for concentration factors typical of parabolic trough receivers (C=100) under the same operating temperatures. Very importantly, the studied nc-AlTiON/Al₂O₃ solar absorber coating shows no degradation after 1000 hours of thermal cycling in air between 300-700ºC. Therefore, the developed coating shows the best thermal in-air long-term stability up to 700°C reported so far for solar absorbers under cycling conditions, and it can be considered as a promising absorber candidate for Generation 3 (GEN3) CSP plants.