Preparation of a novel TiN/TiNxOy/SiO2 composite ceramic films on aluminum substrate as a solar selective absorber by magnetron sputtering

Advanced technology for solar energy collection is increasingly demanded in many applications. In this study we report a reactive magnetron sputtering technique to prepare a TiN/TiNxOy/SiO2 ceramic composite film on aluminum substrate as a solar selective absorber. Aluminum substrate, TiN/TiNxOy and SiO2 layers act as the IR-reflective metallic base layer, double interference absorber layers and ceramic anti-reflection layer, respectively. The structure of TiN, TiNxOy and SiO2 layers was investigated by XRD, SEM and XPS. The ceramic composite films exhibited high absorptance of 95.20% in the solar spectrum range (0.3-2.5 mu m) and low emittance of 5.45% (80 degrees C) in the infrared spectrum range (2.5-25 mu m). This represents an improvement of the solar absorptance by a factor of 23.16 when compared with the bare aluminum substrate. When the films were tested by a heat-treatment at 400 degrees C for 240 h in air, the photo-thermal conversion rate showed a slight reduction at the initial stage but soon stabilized, maintaining a reasonably high conversion rate in the rest of the heat-treatment. Extensive tests at elevated temperatures indicate that the composite ceramic film is a potential candidate in concentrated power solar absorber applications for up to 400 degrees C. (C) 2019 Elsevier B.V. All rights reserved.