Transition Metal-Based Spectrally Selective Coatings Using In-House Developed Spray System

The development of transition metal (Fe, Co, Ni, Mn) oxides based thin coatings is reported on stainless steel substrates for solar absorber applications. Absorber layers are synthesized using in-house developed spray system for metalmetal oxide composite coating structures. The optimized combinations of transition metal precursors are sprayed for thin film deposition. The post-spray heat treatment has been carried out to convert the transition metal precursor layers into spectrally selective absorber coatings showing metal-metal oxide composite structures. Three combinations of bi-transition metals Co-Mn, Co-Fe, and Co-Ni precursors are used to synthesize thin film structures. The thickness of these thin films structures is nearly 1 mu m. These spectrally selective coatings exhibit high absorptivity (alpha similar to 0.9) in 300-900 nm wavelength range and emissivity (epsilon similar to 0.18-0.44) in 2.5-25 mu m wavelength range. The extension of this work is focused on the development of a large-scale system, capable of fabricating spectrally selective coating on desired structures and optimization of annealing conditions, leading to the optimum solar thermal performance with high absorptivity (alpha > 0.95) and low emissivity (epsilon < 0.1) in the desired wavelength ranges.