Angular absorptance and thermal degradation analysis of TiB2/Ti(B,N)/SiON/SiO2 multilayer solar absorber coating

Multilayer solar selective absorber coatings have been developed in the last few decades. The thermal stability in terms of microstructure gives an insightful understanding of the optical properties of such coatings. In this context, we extensively utilized transmission electron microscopy (TEM) analysis to establish the thermal stability of TiB₂/Ti(B,N)/SiON/SiO₂ coating, under thermal cycling/continuous heating to 500°C in vacuum for 250 h. In particular, this work reports the variation in the solar absorptance of TiB₂/Ti(B,N)/SiON/SiO₂ coating with different angles of incidence of the solar radiation. Extensive analysis using the TEM technique reveals the presence of oxide interlayers that act as diffusion barrier layers to enhance the thermal stability of the coating. Computational simulation using SCOUT software validates the measured reflectance spectrum of the developed multilayer coating. The minor changes in absorptance and emissivity after heat treatment in vacuum at 500°C, together with high solar absorptance over a broad angular variation, establish the potential application of TiB₂/Ti(B,N)/SiON/SiO₂ as a selective coating in concentrated solar power systems.